https://glycan.mit.edu/CFGparadigms/api.php?action=feedcontributions&feedformat=atom&user=Ron+SchnaarCFGparadigms - User contributions [en]2026-05-01T00:21:23ZUser contributionsMediaWiki 1.35.13https://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1637Botulinum toxin serotype A (BoNT/A)2011-10-03T14:17:34Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
<p>Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:</p><p>ceramide glucosyltransferase [UGCG]</p><p>beta-1,4-galactosyltransferase 6 [B4GALT6]</p><p><br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]</p><br />
<p>alpha-2,8-sialyltransferase [ST8SIA1]</p><br />
<p>N-acetylgalactosaminyltransferase [B4GALNT1]</p><br />
<p>beta-1,3-galactosyltransferase [B3GALT4]</p><br />
<p>alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]</p><br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1636Botulinum toxin serotype A (BoNT/A)2011-10-03T14:16:53Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
<p>Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:</p><p>ceramide glucosyltransferase [UGCG]</p><p>beta-1,4-galactosyltransferase 6 [B4GALT6]</p><p><br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]</p><br />
<p>alpha-2,8-sialyltransferase [ST8SIA1]</p><br />
<p>N-acetylgalactosaminyltransferase [B4GALNT1]</p><br />
<p>beta-1,3-galactosyltransferase [B3GALT4]</p><br />
<p>alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]</p><br />
<br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1635Botulinum toxin serotype A (BoNT/A)2011-10-03T14:16:20Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:</p>ceramide glucosyltransferase [UGCG]</p><p>beta-1,4-galactosyltransferase 6 [B4GALT6]</p><p><br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]</p><br />
<p>alpha-2,8-sialyltransferase [ST8SIA1]</p><br />
<p>N-acetylgalactosaminyltransferase [B4GALNT1]</p><br />
<p>beta-1,3-galactosyltransferase [B3GALT4]</p><br />
<p>alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]</p><br />
<br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1634Botulinum toxin serotype A (BoNT/A)2011-10-03T14:15:46Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
<br />
<p>Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:<p>ceramide glucosyltransferase [UGCG]</p><p>beta-1,4-galactosyltransferase 6 [B4GALT6]</p><p><br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]</p><br />
<p>alpha-2,8-sialyltransferase [ST8SIA1]</p><br />
<p>N-acetylgalactosaminyltransferase [B4GALNT1]</p><br />
<p>beta-1,3-galactosyltransferase [B3GALT4]</p><br />
<p>alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]</p><br />
<br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1633Botulinum toxin serotype A (BoNT/A)2011-10-03T14:14:06Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
<br />
Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:<p>ceramide glucosyltransferase [UGCG]<p>beta-1,4-galactosyltransferase 6 [B4GALT6]<p><br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]<br />
alpha-2,8-sialyltransferase [ST8SIA1]<br />
N-acetylgalactosaminyltransferase [B4GALNT1]<br />
beta-1,3-galactosyltransferase [B3GALT4]<br />
alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]<br />
<br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Botulinum_toxin_serotype_A_(BoNT/A)&diff=1632Botulinum toxin serotype A (BoNT/A)2011-10-03T14:12:38Z<p>Ron Schnaar: </p>
<hr />
<div>'''The clostridial neurotoxins''' are the most lethal protein toxins for humans and recently have been utilized as therapeutic agents to treat numerous human neurological inflictions. The Botulinum neurotoxins produced by ''Clostridium botulinum'' and Tetanus toxin produced by ''C. tetani'' are members of the family of clostridial neurotoxins. The clostridial neurotoxins are di-chain toxins with the N-terminal catalytic domains (Light Chain, LC) possessing metalloprotease activity that is disulfide linked to the C-terminal<br />
domain (Heavy Chain, HC). The neurological toxicity and therapeutic utility of the clostridial neurotoxins is due to the HC’s tropism for neuronal receptors and the LC’s cleavage of neuron-specific target proteins, termed SNARE proteins. SNARE proteins are responsible for the fusion of neurotransmitter vesicles with the plasma membrane. There are seven serotypes of the BoNTs that share primary and ternary structure-function properties. Each BoNT serotype utilizes dual receptors for entry into neurons and each cleaves a specific SNARE protein or a unique site on a specific SNARE protein.<br />
<br />
'''The Botulinum neurotoxins''' elicit flaccid paralysis, while tetanus toxin elicits spastic paralysis. The differential toxicity is due to the unique trafficking of these toxins in motor neurons. Botulinum neurotoxin HC binds to dual host receptors on the surface of motor neurons to deliver the BoNT to acidified vesicles where the LC is translocated into the cytoplasm of the neuron. Upon entry into the cytoplasm, LC cleaves a SNARE protein which inhibits fusion of neurotransmitter vesicles to the plasma membrane, inhibiting the release of neurotransmitter molecules. In contrast, TeNT HC binds to dual host receptors on the surface of motor neurons to deliver the TeNT to neutral vesicles for retrograde trafficking to the central nervous system. Following this transcytosis, Tetanus toxin binds dual receptors on inhibitory neurons to deliver TeNT to acidified endosomes where the LC is translocated into the cytoplasm of the neuron. TeNT LC cleaves the SNARE proteins, VAMP-2, which inhibits the release of neurotransmitters from inhibitory motor neurons. The inability to release neurotransmitter from inhibitory motor neurons yields spastic paralysis.<br />
<br />
'''Botulinum toxin serotype A (BoNT/A)''' was chosen as the paradigm for the clostridial neurotoxins, since the dual host receptors for BoNT/A have been determined and the basis for recognizing cleavage of the SNARES substrate SNAP25 has been characterized. In addition, BoNT/A is the most common serotype used in clinical therapies. It is anticipated that understanding BoNT/A action will provide new information relevant to the entire family of clostridial neurotoxins. These studies will enhance the understanding of the unique<br />
properties of each BoNT serotype and Tetanus toxin to extend their utility in human inflictions. The CFG has been used to facilitate the characterization of the ganglioside binding pocket of these neurotoxins. Prior studies utilized low throughput analyses that provided limited insight into interactions between these neurotoxins and gangliosides, and but high throughput analysis of the CFG core provided a better understanding of the biochemical and structural interactions of the neurotoxins with glycans. For example, array analysis showed that the dual receptors for Tetanus toxin recognized unique components of gangliosides.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
CFG Participating Investigators (PIs) contributing to the understanding of BoNT/A include: Joseph Barbieri, Edwin Chapman, Minoru Fukuda, Raymond Stevens, Willie Vann<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
Botulinum neurotoxins bind to two co-receptors on neuronal cell surfaces: common glycolipid receptors and different protein receptors that target them to specific cell types. The common ganglioside co-receptor is GT1b<ref>Yowler BC, Schengrund CL. Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b. "Biochemistry" 43, 9725-9731 (2004) </ref>.<ref> Stenmark. P, Dupuy1, J, Imamura, A, Kiso, M, and Stevens, RC. Crystal Structure of Botulinum Neurotoxin Type A in Complex with the Cell Surface Co-Receptor GT1b—Insight into the Toxin–Neuron Interaction “PLOS Pathogens” 4, e1000129 (2008) </ref><br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
Botulinum toxins are produced by ''Clostridium botulinum'' Their target glycolipid and protein receptors are found on the surface of motorneurons.<br />
<br><br />
<br />
=== Biosynthesis of ligands ===<br />
<br />
Ganglioside GT1b is synthesized stepwise from the lipid ceramide by the action of the following seven glycosyltransferases [genes]:<br />
<br />
ceramide glucosyltransferase [UGCG]<br />
beta-1,4-galactosyltransferase 6 [B4GALT6]<br />
lactosylceramide a-2,3-sialyltransferase [ST3GAL5]<br />
alpha-2,8-sialyltransferase [ST8SIA1]<br />
N-acetylgalactosaminyltransferase [B4GALNT1]<br />
beta-1,3-galactosyltransferase [B3GALT4]<br />
alpha-2,3-sialyltransferase [ST3GAL2, ST3GAL3]<br />
<br />
Evidence for the action of each of the above genes in this pathway is supported by either in vitro enzyme assays, genetic studies, or both. Other (redundant) enzymes may also act in this pathway.<br />
<br />
<br><br />
=== Structure ===<br />
The crystal structure of BoNT/A has been solved both alone and bound to its ganglioside co-receptor (see [http://pathema.jcvi.org/cgi-bin/Clostridium/shared/HtmlPage.cgi?page=bont_structures#typeA entry in Panthema] NIAID Bioinformatics Resource Center).<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
Botulinum toxins cause neurotoxicity by cleaving SNARE proteins, which normally allow neurotransmitter-containing vesicles to fuse with the neuronal plasma membrane.<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=botulinum&maxresults=20 CFG database search results for botulinum].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
BoNT/A is not represented on the CFG microarrays, which only contain probes for mouse and human glycogenes.<br />
<br><br />
<br />
=== Knockout mouse lines ===<br />
Not applicable.<br />
<br><br />
<br />
=== Glycan array ===<br />
The CFG synthesized ganglioside derivates that have been used in co-crystallization studies with the clostridial neurotoxins. The CFG glycan array was used to identify the ganglioside binding specificity to the clostridial neurotoxins ([http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_2011 BoNT/C], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1972 BoNT/D], [http://www.functionalglycomics.org/glycomics/HServlet?operation=view&sideMenu=no&psId=primscreen_1681 BoNT/F]).<br />
<br />
== Related GBPs ==<br />
<br />
Botulinum neurotoxins serotypes B-G (CFG data: [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FB&maxresults=20 BoNT/B,] [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FC&maxresults=20 BoNT/C,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FD&maxresults=20 BoNT/D,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FE&maxresults=20 BoNT/E,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Botulinum+AND+neurotoxin+AND+F&maxresults=20 BoNT/F,][http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=BoNT%2FG&maxresults=20 BoNT/G)], Tetanus toxin [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=tetanus+AND+toxin&maxresults=20 (CFG data)]<br />
<br />
== References ==<br />
<references/><br />
* C. Chen, Z. Fu, J-J. P. Kim, J.T. Barbieri, and M. R. Baldwin. 2009. Gangliosides as High Affinity Receptors for Tetanus Neurotoxin. J Biol Chem. 284: 26569-77. PMC2785345<br />
* M. Dong, W. H. Tepp, H. Liu, E. A. Johnson, and E. R. Chapman. 2007. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. J. Cell Biol. 179: 1511-1522. PMC2373501<br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Joseph Barbieri, James Paton</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1041MAG2010-07-19T18:00:31Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref name="mountney2010">Mountney A., Zahner M.R., Lorenzini I., Oudega M., Schramm L.P., Schnaar R.L. Sialidase enhances recovery from spinal cord contusion injury. Proc Natl Acad Sci U S A 107, 11561-11566, 2010</ref><ref name="vyas2005">Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref name="yang1996">Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system). In both central and peripheral nervous systems, MAG is enriched on the innermost wrap of myelin, directly apposing the axon surface.<ref name="quarles2007">Quarles RH. Myelin-associated glycoprotein (MAG): past, present and beyond. J Neurochem. 100, 1431-1448 (2007).</ref></b><br><br />
=== Biosynthesis of ligands ===<br />
<b>Mice null for the ganglioside-specific N-acetylgalactosaminyltransferase gene <i>B4galnt1</i> (GM2/GD2 synthase) have similar nervous system phenotypic deficits as MAG-null mice (see "Biological roles of GBP-ligand interaction" below). These data implicate MAG-binding brain gangliosides GD1a and/or GT1b as MAG ligands.<ref name="pan2005">Pan, B., Fromholt, S.E., Hess, E.J., Crawford, T.O., Griffin, J.W., Sheikh, K.A., Schnaar, R.L. Myelin-associated glycoprotein and gangliosides mediate axon-myelin stability: Neuropathology and behavioral deficits in single- and double-null mice. Exp. Neurol. 195, 208-217 (2005)</ref>.<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref name="umemori1994">Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref name="jaramillo1994">Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<p>MAG is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon survival, helps structure myelin gaps (nodes of Ranvier) essential for rapid nerve conduction, regulates the axon cytoskeleton and protects axons from acute toxic insults. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG on residual myelin membranes at injury sites actively signals axons to halt elongation. Whether MAG's stabilizing effects and its inhibition of axon regeneration are part of the same signaling system is under investigation.</p><br />
<p></p><br />
<p>MAG has multiple receptors on the axon surface, including gangliosides GD1a/GT1b, the GPI-anchored Nogo receptors (NgR1 and NgR2), and transmembrane proteins PirB and β-integrin. Some of these interactions involve MAG's glycan binding capability, while others may not. The following biological roles of MAG have been experimentally linked to its glycan binding activity using genetic, biochemical, and/or pharmacological criteria:</p><br />
<p></p><br />
<p>1. Long term axon stabilization: <i>B4galnt1</i>-null mice, which lack the termini of complex gangliosides, display the same progressive axon degeneration phenotype as <i>Mag</i>-null mice. Double null mice (<i>B4galnt1</i>, <i>Mag</i>) are similar. <ref name="pan2005"/></p><p></p><br />
<p>2. Nodes of Ranvier: <i>B4galnt1</i>-null and <i>Mag</i>-null mice have similar deficits in the structures of Nodes of Ranvier<ref name="pernet2008">Pernet V., Joly S., Christ F., Dimou L., Schwab M.E. Nogo-A and myelin-associated<br />
glycoprotein differently regulate oligodendrocyte maturation and myelin formation. J Neurosci. 16, 7435-44 (2008).</ref><ref name="susuki2007">Susuki K., Baba H., Tohyama K., Kanai K., Kuwabara S., Hirata K., Furukawa K., Furukawa K., Rasband M.N., Yuki N. Gangliosides contribute to stability of paranodal junctions and ion channel clusters in myelinated nerve fibers. Glia 55, 746-757. 2007.</ref></p><br />
<p>3. Cytoskeletal organization: <i>B4galnt1</i>-null, <i>Mag</i>-null and double-null mice have similarly reduced neurofilament spacing and reduced axon diameter.<ref name="pan2005"/></p><p></p><br />
<p>4. Axon protection: MAG-mediated protection of axons from toxic insults is diminished in <i>B4galnt1</i>-null mice or after treatment of axons with sialidase.<ref name="nguyen2009">Nguyen T., Mehta N.R., Conant K., Kim K.J., Jones M., Calabresi P.A., Melli G., Hoke A., Schnaar R.L., Ming G.L., Song H., Keswani S.C., Griffin J.W. Axonal protective effects of the myelin-associated glycoprotein. J Neurosci. 21, 630-637 (2009).</ref><ref name="mehta2010">Mehta N.R., Nguyen T., Bullen J.W., Griffin J.W., Schnaar R.L. Myelin-associated glycoprotein (MAG) protects neurons from acute toxicity using a ganglioside-dependent mechanism. ACS Chem Neurosci. 1, 215-222, 2010.</ref><br />
<p></p><br />
<p>5. Regulating axon regeneration: MAG-mediated inhibition of axon regeneration is diminished in <i>B4galnt1</i>-null mice, after treatment with sialidase, or by addition of MAG-binding soluble glycans.<ref name="vyas2002">Vyas A.A., Patel H.V., Fromholt S.E., Heffer-Lauc M., Vyas K.A., Dang J., Schachner M., Schnaar R.L. Gangliosides are functional nerve cell ligands for myelin-associated glycoprotein (MAG), an inhibitor of nerve regeneration. Proc Natl Acad Sci U S A 99, 8412-8417, 2002.</ref><ref name="vyas2005"/></p><br />
<br />
MAG signaling is bidirectional,<ref name="quarles2007"/> into the myelinating cells and into myelin-ensheathed axons. Signaling into myelinating cells may involve tyrosine phosphorylation of the MAG intracellular domain downstream of ligand engagement,<ref name="umemori1994"/><ref name="jaramillo1994"/> whereas signals into the axon are likely to involve activation of the small non-receptor GTPase RhoA.<ref name="yiu2006">Yiu G., He Z. Glial inhibition of CNS axon regeneration. Nat. Rev. Neurosci. 7, 617–627, 2006.</ref><br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1040MAG2010-07-19T17:33:22Z<p>Ron Schnaar: /* Biological roles of GBP-ligand interaction */</p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref name="mountney2010">Mountney A., Zahner M.R., Lorenzini I., Oudega M., Schramm L.P., Schnaar R.L. Sialidase enhances recovery from spinal cord contusion injury. Proc Natl Acad Sci U S A 107, 11561-11566, 2010</ref><ref name="vyas2005">Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref name="yang1996">Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system). In both central and peripheral nervous systems, MAG is enriched on the innermost wrap of myelin, directly apposing the axon surface.<ref name="quarles2007">Quarles RH. Myelin-associated glycoprotein (MAG): past, present and beyond. J Neurochem. 100, 1431-1448 (2007).</ref></b><br><br />
=== Biosynthesis of ligands ===<br />
<b>Mice null for the ganglioside-specific N-acetylgalactosaminyltransferase gene <i>B4galnt1</i> (GM2/GD2 synthase) have similar nervous system phenotypic deficits as MAG-null mice (see "Biological roles of GBP-ligand interaction" below). These data implicate MAG-binding brain gangliosides GD1a and/or GT1b as MAG ligands.<ref name="pan2005">Pan, B., Fromholt, S.E., Hess, E.J., Crawford, T.O., Griffin, J.W., Sheikh, K.A., Schnaar, R.L. Myelin-associated glycoprotein and gangliosides mediate axon-myelin stability: Neuropathology and behavioral deficits in single- and double-null mice. Exp. Neurol. 195, 208-217 (2005)</ref>.<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<p>MAG is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon survival, helps structure myelin gaps (nodes of Ranvier) essential for rapid nerve conduction, regulates the axon cytoskeleton and protects axons from acute toxic insults. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG on residual myelin membranes at injury sites actively signals axons to halt elongation. Whether MAG's stabilizing effects and its inhibition of axon regeneration are part of the same signaling system is under investigation.</p><br />
<p></p><br />
<p>MAG has multiple receptors on the axon surface, including gangliosides GD1a/GT1b, the GPI-anchored Nogo receptors (NgR1 and NgR2), and transmembrane proteins PirB and β-integrin. Some of these interactions involve MAG's glycan binding capability, while others may not. The following biological roles of MAG have been experimentally linked to its glycan binding activity using genetic, biochemical, and/or pharmacological criteria:</p><br />
<p></p><br />
<p>1. Long term axon stabilization: <i>B4galnt1</i>-null mice, which lack the termini of complex gangliosides, display the same progressive axon degeneration phenotype as <i>Mag</i>-null mice. Double null mice (<i>B4galnt1</i>, <i>Mag</i>) are similar. <ref name="pan2005"/></p><p></p><br />
<p>2. Nodes of Ranvier: <i>B4galnt1</i>-null and <i>Mag</i>-null mice have similar deficits in the structures of Nodes of Ranvier<ref name="pernet2008">Pernet V., Joly S., Christ F., Dimou L., Schwab M.E. Nogo-A and myelin-associated<br />
glycoprotein differently regulate oligodendrocyte maturation and myelin formation. J Neurosci. 16, 7435-44 (2008).</ref><ref name="susuki2007">Susuki K., Baba H., Tohyama K., Kanai K., Kuwabara S., Hirata K., Furukawa K., Furukawa K., Rasband M.N., Yuki N. Gangliosides contribute to stability of paranodal junctions and ion channel clusters in myelinated nerve fibers. Glia 55, 746-757. 2007.</ref></p><br />
<p>3. Cytoskeletal organization: <i>B4galnt1</i>-null, <i>Mag</i>-null and double-null mice have similarly reduced neurofilament spacing and reduced axon diameter.<ref name="pan2005"/></p><p></p><br />
<p>4. Axon protection: MAG-mediated protection of axons from toxic insults is diminished in <i>B4galnt1</i>-null mice or after treatment of axons with sialidase.<ref name="nguyen2009">Nguyen T., Mehta N.R., Conant K., Kim K.J., Jones M., Calabresi P.A., Melli G., Hoke A., Schnaar R.L., Ming G.L., Song H., Keswani S.C., Griffin J.W. Axonal protective effects of the myelin-associated glycoprotein. J Neurosci. 21, 630-637 (2009).</ref><ref name="mehta2010">Mehta N.R., Nguyen T., Bullen J.W., Griffin J.W., Schnaar R.L. Myelin-associated glycoprotein (MAG) protects neurons from acute toxicity using a ganglioside-dependent mechanism. ACS Chem Neurosci. 1, 215-222, 2010.</ref><br />
<p></p><br />
<p>5. Regulating axon regeneration: MAG-mediated inhibition of axon regeneration is diminished in <i>B4galnt1</i>-null mice, after treatment with sialidase, or by addition of MAG-binding soluble glycans.<ref name="vyas2002">Vyas A.A., Patel H.V., Fromholt S.E., Heffer-Lauc M., Vyas K.A., Dang J., Schachner M., Schnaar R.L. Gangliosides are functional nerve cell ligands for myelin-associated glycoprotein (MAG), an inhibitor of nerve regeneration. Proc Natl Acad Sci U S A 99, 8412-8417, 2002.</ref><ref name="vyas2005"/></p><br />
<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1039MAG2010-07-19T17:30:50Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref name="mountney2010">Mountney A., Zahner M.R., Lorenzini I., Oudega M., Schramm L.P., Schnaar R.L. Sialidase enhances recovery from spinal cord contusion injury. Proc Natl Acad Sci U S A 107, 11561-11566, 2010</ref><ref name="vyas2005">Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref name="yang1996">Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system). In both central and peripheral nervous systems, MAG is enriched on the innermost wrap of myelin, directly apposing the axon surface.<ref name="quarles2007">Quarles RH. Myelin-associated glycoprotein (MAG): past, present and beyond. J Neurochem. 100, 1431-1448 (2007).</ref></b><br><br />
=== Biosynthesis of ligands ===<br />
<b>Mice null for the ganglioside-specific N-acetylgalactosaminyltransferase gene <i>B4galnt1</i> (GM2/GD2 synthase) have similar nervous system phenotypic deficits as MAG-null mice (see "Biological roles of GBP-ligand interaction" below). These data implicate MAG-binding brain gangliosides GD1a and/or GT1b as MAG ligands.<ref name="pan2005">Pan, B., Fromholt, S.E., Hess, E.J., Crawford, T.O., Griffin, J.W., Sheikh, K.A., Schnaar, R.L. Myelin-associated glycoprotein and gangliosides mediate axon-myelin stability: Neuropathology and behavioral deficits in single- and double-null mice. Exp. Neurol. 195, 208-217 (2005)</ref>.<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<p>MAG is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon survival, helps structure myelin gaps (nodes of Ranvier) essential for rapid nerve conduction, regulates the axon cytoskeleton and protects axons from acute toxic insults. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG on residual myelin membranes at injury sites actively signals axons to halt elongation. Whether MAG's stabilizing effects and its inhibition of axon regeneration are part of the same signaling system is under investigation.</p><br />
<p></p><br />
<p>MAG has multiple receptors on the axon surface, including gangliosides GD1a/GT1b, the GPI-anchored Nogo receptors (NgR1 and NgR2), and transmembrane proteins PirB and β-integrin. Some of these interactions involve MAG's glycan binding capability, while others may not. The following biological roles of MAG have been experimentally linked to its glycan binding using genetic, biochemical, and/or pharmacological criteria:</p><br />
<p></p><br />
<p>1. Long term axon stabilization: <i>B4galnt1</i>-null mice, which lack the termini of complex gangliosides, display the same progressive axon degeneration phenotype as <i>Mag</i>-null mice. Double null mice (<i>B4galnt1</i>, <i>Mag</i>) are similar. <ref name="pan2005"/></p><p></p><br />
<p>2. Nodes of Ranvier: <i>B4galnt1</i>-null and <i>Mag</i>-null mice have similar deficits in the structures of Nodes of Ranvier<ref name="pernet2008">Pernet V., Joly S., Christ F., Dimou L., Schwab M.E. Nogo-A and myelin-associated<br />
glycoprotein differently regulate oligodendrocyte maturation and myelin formation. J Neurosci. 16, 7435-44 (2008).</ref><ref name="susuki2007">Susuki K., Baba H., Tohyama K., Kanai K., Kuwabara S., Hirata K., Furukawa K., Furukawa K., Rasband M.N., Yuki N. Gangliosides contribute to stability of paranodal junctions and ion channel clusters in myelinated nerve fibers. Glia 55, 746-757. 2007.</ref></p><br />
<p>3. Cytoskeletal organization: <i>B4galnt1</i>-null, <i>Mag</i>-null and double-null mice have similarly reduced neurofilament spacing and reduced axon diameter.<ref name="pan2005"/></p><p></p><br />
<p>4. Axon protection: MAG-mediated protection of axons from toxic insults is diminished in <i>B4galnt1</i>-null mice or after treatment of axons with sialidase.<ref name="nguyen2009">Nguyen T., Mehta N.R., Conant K., Kim K.J., Jones M., Calabresi P.A., Melli G., Hoke A., Schnaar R.L., Ming G.L., Song H., Keswani S.C., Griffin J.W. Axonal protective effects of the myelin-associated glycoprotein. J Neurosci. 21, 630-637 (2009).</ref><ref name="mehta2010">Mehta N.R., Nguyen T., Bullen J.W., Griffin J.W., Schnaar R.L. Myelin-associated glycoprotein (MAG) protects neurons from acute toxicity using a ganglioside-dependent mechanism. ACS Chem Neurosci. 1, 215-222, 2010.</ref><br />
<p></p><br />
<p>5. Regulating axon regeneration: MAG-mediated inhibition of axon regeneration is diminished in <i>B4galnt1</i>-null mice, after treatment with sialidase, or by addition of MAG-binding soluble glycans.<ref name="vyas2002">Vyas A.A., Patel H.V., Fromholt S.E., Heffer-Lauc M., Vyas K.A., Dang J., Schachner M., Schnaar R.L. Gangliosides are functional nerve cell ligands for myelin-associated glycoprotein (MAG), an inhibitor of nerve regeneration. Proc Natl Acad Sci U S A 99, 8412-8417, 2002.</ref><ref name="vyas2005"/></p><br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1030MAG2010-07-19T16:37:12Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system). In both central and peripheral nervous systems, MAG is enriched on the innermost wrap of myelin, directly apposing the axon surface.<ref name="quarles2007">Quarles RH. Myelin-associated glycoprotein (MAG): past, present and beyond. J Neurochem. 100, 1431-1448 (2007).</ref></b><br><br />
=== Biosynthesis of ligands ===<br />
<b>Mice null for the ganglioside-specific N-acetylgalactosaminyltransferase gene <i>B4galnt1</i> (GM2/GD2 synthase) have similar nervous system phenotypic deficits as MAG-null mice (see "Biological Roles," below). These data implicate MAG-binding brain gangliosides GD1a and/or GT1b as MAG ligands.<ref name="pan2005">Pan, B., Fromholt, S.E., Hess, E.J., Crawford, T.O., Griffin, J.W., Sheikh, K.A., Schnaar, R.L. Myelin-associated glycoprotein and gangliosides mediate axon-myelin stability: Neuropathology and behavioral deficits in single- and double-null mice. Exp. Neurol. 195, 208-217 (2005)</ref>.<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<p>MAG is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon-myelin stability, helps to structure nodes of Ranvier, and regulates the axon cytoskeleton. In addition to its long-term stabilizing effects, MAG protects axons from acute toxic insults. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG and a discrete set of other molecules on residual myelin membranes at injury sites actively signal axons to halt elongation. Whether MAG's stabilizing effects and its inhibition of axon regeneration after injury are part of the same signaling pathway is still under investigation.</p><br />
<p></p><br />
<p>MAG has multiple receptors on the axon surface, including gangliosides GD1a/GT1b, the GPI-anchored Nogo receptors (NgR1 and NgR2), and transmembrane proteins PirB and β-integrin. Which of these interactions involve MAG's glycan binding capabilities is still under investigation. The following biological roles of MAG have been associated with glycan binding using genetic, biochemical, and/or pharmacological tests:</p><br />
<p></p><br />
<p>1. Long term axon stabilization: <i>B4galnt1</i>-null mice, like <i>Mag</i>-null mice, display a progressive axon degeneration phenotype.<ref name="pan2005"/></p><br />
<p></p><br />
<p></p><br />
<p></p><br />
<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1014MAG2010-07-19T14:39:32Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<b>Mice null for the ganglioside-specific N-acetylgalactosaminyltransferase gene <i>B4galnt1</i> (GM2/GD2 synthase) have similar nervous system phenotypic deficits as MAG-null mice (see "Biological Roles," below). These data implicate MAG-binding brain gangliosides GD1a and/or GT1b as MAG ligands.<ref name="pan2005">Pan, B., Fromholt, S.E., Hess, E.J., Crawford, T.O., Griffin, J.W., Sheikh, K.A., Schnaar, R.L. Myelin-associated glycoprotein and gangliosides mediate axon-myelin stability: Neuropathology and behavioral deficits in single- and double-null mice. Exp. Neurol. 195, 208-217 (2005)</ref>.<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1013MAG2010-07-19T14:15:32Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref name="collins1996">Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref name="collins1996"/> and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<ref name=" Lehmann, F.2004"> Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1012MAG2010-07-19T14:11:02Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref name="strenge1998">Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref name="strenge1998"/>. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1011MAG2010-07-19T13:55:28Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref>. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1010MAG2010-07-19T13:52:42Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides. Enhanced binding to first structure in intact gangliosides<ref>Yang, L. J., Zeller, C.B., Shaper, N.L., Kiso, M., Hasegawa, A., Shapiro, R.E., Schnaar, R.L. Gangliosides are neuronal ligands for myelin-associated glycoprotein. Proc. Natl. Acad. Sci. USA 93, 814-818 (1996).</ref> <ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1009MAG2010-07-19T13:36:50Z<p>Ron Schnaar: /* Carbohydrate ligands */</p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal-R<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
Similar binding to the following structures as soluble glycosides. Enhanced binding to first structure in intact gangliosides.<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
<br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1008MAG2010-07-19T13:34:09Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, and inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1007MAG2010-07-19T13:32:15Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg2.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon_lg2.jpg&diff=1006File:Siglec-04 cartoon lg2.jpg2010-07-19T13:31:50Z<p>Ron Schnaar: </p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1005MAG2010-07-19T13:10:49Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon_lg.jpg]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1004MAG2010-07-19T13:10:11Z<p>Ron Schnaar: Undo revision 1003 by Ron Schnaar (Talk)</p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon.png]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=1003MAG2010-07-19T13:07:25Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Siglec-04_cartoon_lg.jpg]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon.png]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon_lg.jpg&diff=1002File:Siglec-04 cartoon lg.jpg2010-07-19T13:05:14Z<p>Ron Schnaar: </p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon.png&diff=1001File:Siglec-04 cartoon.png2010-07-19T13:03:53Z<p>Ron Schnaar: uploaded a new version of "File:Siglec-04 cartoon.png":&#32;jpg version large</p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon.png&diff=1000File:Siglec-04 cartoon.png2010-07-19T12:53:40Z<p>Ron Schnaar: uploaded a new version of "File:Siglec-04 cartoon.png":&#32;Increased size</p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon.png&diff=999File:Siglec-04 cartoon.png2010-07-19T12:44:24Z<p>Ron Schnaar: uploaded a new version of "File:Siglec-04 cartoon.png":&#32;Reverted to version as of 02:41, 8 June 2010</p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec-04_cartoon.png&diff=998File:Siglec-04 cartoon.png2010-07-19T12:43:30Z<p>Ron Schnaar: uploaded a new version of "File:Siglec-04 cartoon.png":&#32;Reverted to version as of 02:40, 8 June 2010</p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=997MAG2010-07-19T12:40:15Z<p>Ron Schnaar: </p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity of stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG-ligand interactions. Evidence suggests that inhibition of MAG-ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The glycan specificity of Siglec-4 has been investigated using resialylated erythrocytes<ref>Kelm, S. et al. Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily. Curr Biol. 4, 965-972 (1994)</ref>, gangliosides<ref>Collins, B. E., Kiso, M., Hasegawa, A., Tropak, M. B., Roder, J. C., Crocker, P. R., Schnaar, R. L. Binding specificities of the sialoadhesin family of I-type lectins. Sialic acid linkage and substructure requirements for binding of myelin-associated glycoprotein, Schwann cell myelin protein, and sialoadhesin. J Biol Chem. 272, 16889-16895 (1997)</ref><ref>Collins, B. E., Yang, L. J., Mukhopadhyay, G., Filbin, M. T., Kiso, M., Hasegawa, A., Schnaar, R.L. Sialic acid specificity of myelin-associated glycoprotein binding. J Biol Chem. 272, 1248-1255 (1997)</ref>, inhibition assays with oligosaccharides<ref>Strenge, K., Schauer, R., Bovin, N., Hasegawa, A., Ishida, H., Kiso, M., Kelm, S. Glycan specificity of myelin-associated glycoprotein and sialoadhesin deduced from interactions with synthetic oligosaccharides. Eur J Biochem. 258, 677-685 (1998)</ref><ref>Blixt, O., Collins, B. E., van den Nieuwenhof, I. M., Crocker, P. R., Paulson, J. C. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem. 278, 31007-31019 (2003)</ref>.<br />
<br />
'''Determinant recognized:'''<br />
<br />
[[File:Sia3Gal_small.png]]<br />
<br />
on glycolipids and/or glycoproteins<br />
<br />
'''Specificity for linkage of sialic acid to underlying Gal:'''<br />
<br />
about 10-fold better binding to Neu5Acα2,3Gal-R than Neu5Acα2,6Gal<br />
<br />
'''Underlying glycan structures can enhance binding:'''<br />
<br />
similar binding to the following structures<br />
<br />
[[File:Sia3Gal3GalNAc_small.png]]<br />
<br />
[[File:Sia3Gal3GlcNAc_small.png]]<br />
<br />
[[File:Sia3Gal4GlcNAc_small.png]]<br />
<br />
'''Enhanced binding through additional internal sialic acids:'''<br />
<br />
[[File:Sia3Gal3GalNAc4(Sia3)Gal_small.png]]<br />
<br />
higher binding to<br />
<br />
[[File:Sia3Gal3(Sia6)GalNAc_small.png]]<br />
<br />
<br><br />
=== Cellular expression of GBP and ligands ===<br />
<b>MAG (Siglec-4) is expressed exclusively on myelin, which is produced by oligodendrocytes (the myelinating cells of the central nervous system) and Schwann cells (the myelinating cells of the peripheral nervous system).</b><br><br />
=== Biosynthesis of ligands ===<br />
<br><br />
=== Structure ===<br />
<br />
[[File:Siglec-04_cartoon.png]]<br />
<br />
Siglec-4 is a heavily glycosylated protein of about 100kDa with 30% of its mass being made up by carbohydrates distributed over eight glycosylation sites. The extracellular part of Siglec-4 consists of five Ig-like domains (one V-set domain and four C2-set domains). Two splice variants for Siglec-4 are found in mammals, L-MAG (72kDa) and S-MAG (67kDa), which differ in their cytoplasmic domain. L-MAG contains a tyrosine phosphorylation site<ref>Umemori, H., Sato, S., Yagi, T., Aizawa, S., Yamamoto, T. Initial events of myelination involve Fyn tyrosine kinase signalling. Nature 367, 572-576 (1994)</ref><ref>Jaramillo, M. L., Afar, D. E., Almazan, G., Bell, J. C. Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules. J Biol Chem. 269, 27240-27245 (1994)</ref> that is missing in S-MAG.<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
Compared to other Siglecs, Siglec-4 is most conserved. Based on sequence similarity orthologous proteins can be identified in all vertebrate genomes available so far (several mammals, chicken, Xenopus, zebrafish and fugu). Sialic acid binding activity selective for 2,3-linked Sia has been shown for the avian ortholog (SMP<ref>Collins, B.E., Ito, H., Sawada, N., Ishida, H., Kiso, M., Schnaar, R.L. Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs. J Biol Chem. 274, 37637-37643 (1999)</ref>) and fish Siglec-4 from zebrafish (Danio rerio) and fugu (Takifugu rubripes)<br />
<ref name=" Lehmann, F.2004"><br />
Lehmann, F., Gäthje, H., Kelm, S., Dietz, F. Evolution of sialic acid-binding proteins: molecular cloning and expression of fish siglec-4. Glycobiology 14, 959-968 (2004)</ref>). Whereas the primary sequences of the Sia-binding N-terminal domains is 97 % identical between rodents and man and share over 50 % sequence identity between fish and mammals, the cytoplasmic tail is much less conserved (20% identical amino acids between fish and mammals<ref name=" Lehmann, F.2004"></ref>).<br />
<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:Siglec8_SiglecF.jpg&diff=474File:Siglec8 SiglecF.jpg2010-05-17T18:24:24Z<p>Ron Schnaar: uploaded a new version of "File:Siglec8 SiglecF.jpg":&#32;smaller</p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=473Siglec-82010-05-17T18:22:02Z<p>Ron Schnaar: /* Structure */</p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. [http://www.ncbi.nlm.nih.gov/pubmed/10856141 Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils.] J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B.S. [http://www.ncbi.nlm.nih.gov/pubmed/19178537 Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors.] Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8, and its murine paralog Siglec-F, recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
The high affinity ligand for Siglec-8 has been deduced from glycan microarray screening on the CFG microarray to be NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<ref>Bochner BS, Alvarez RA, Mehta P, Bovin NV, Blixt O, White JR, Schnaar RL. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 2005; 280:4307-12</ref><ref>Tateno H, Crocker PR, Paulson JC. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred glycan ligand. Glycobiology 2005; 15:1125-35</ref><br />
<br />
[[File:6pso3slex.jpg]]<br />
<br />
For Siglec-F, histologic studies suggest the presence of an &alpha;2,3-linked sialylated glycoprotein ligand expressed by airway epithelium. Its constitutive expression requires the enzyme St3Gal3.<ref>Guo JP, Brummet ME, Myers AC, Na HJ, Rowland E, Schnaar RL, Zheng T, Zhu Z, Bochner BS. Characterization of expression of glycan ligands for Siglec-F in normal mouse lungs. Am J Respir Cell and Molec Biol 2010 Apr 15 [Epub ahead of print] 2010 and </ref> Levels of this ligand are increased during allergic pulmonary inflammation.<ref>Zhang M, Angata T, Cho JY, Miller M, Broide DH, Varki A. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse eosinophils. Blood 2007; 109:4280-7</ref><br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils (weak)<ref>Kikly KK, Bochner BS, Freeman S, Tan KB, Gallagher KT, D'Alessio K, Holmes SD, Abrahamson J, Hopson CB, Fischer EI, Erickson-Miller CL, Tachimoto H, Schleimer RP, White JR. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells and basophils. J Allergy Clin Immunol 2000; 105:1093-100</ref><ref>Floyd H, Ni J, Cornish AL, Zeng Z, Liu D, Carter KC, Steel J, Crocker PR. Siglec-8: a novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 2000; 275:861-6</ref><ref>Yokoi H, Myers A, Matsumoto K, Crocker PR, Saito H, Bochner BS. Alteration and acquisition of Siglecs during in vitro maturation of CD34+ progenitors into human mast cells. Allergy 2006; 61:769-76</ref><br />
<br><br />
<br />
=== Structure ===<br />
[[File:Siglec8 SiglecF.jpg]]<br />
<br><br />
<br />
=== Biological roles of GBP-ligand interaction ===<br />
'''In vitro'''<br />
Eosinophil apoptosis.<ref>Nutku E, Aizawa H, Hudson SA, Bochner BS. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 2003; 101:5014-20</ref><ref>Nutku E, Hudson SA, Bochner BS. Mechanism of Siglec-8-induced human eosinophil apoptosis: role of caspases and mitochondrial injury. Biochem Biophys Res Commun 2005; 336:918-24</ref><ref>1Nutku-Bilir E, Hudson SA, Bochner BS. Interleukin-5 priming of human eosinophils alters Siglec-8 mediated apoptosis pathways. Am J Respir Cell Mol Biol 2008; 38:121-4</ref><br />
Inhibition of mast cell mediator release.<ref>Yokoi H, Choi OH, Hubbard W, Lee H-S, Canning BJ, Lee HH, Ryu S-D, Bickel CA, Hudson SA, MacGlashan DW, Jr., Bochner BS. Inhibition of FcεRI-dependent mediator release and calcium flux from human mast cells by Siglec-8 engagement. J Allergy Clin Immunol 2008; 121:499-505</ref><br />
<br />
'''In vivo (for Siglec-F)'''<br />
Antibody administration to mice causes selective depletion of eosinophils in blood and gastrointestinal tissues via apoptosis.<ref>Zimmermann N, McBride ML, Yamada Y, Hudson SA, Jones C, Cromie KD, Crocker PR, Rothenberg ME, Bochner BS. Siglec-F antibody administration to mice selectively reduces blood and tissue eosinophils. Allergy 2008; 63:1156-63</ref> They are also effective in reversing some sequelae of mouse models of eosinophilic gastroenteritis and asthma.<ref>Song DJ, Cho JY, Miller M, Strangman W, Zhang M, Varki A, Broide DH. Anti-Siglec-F antibody inhibits oral egg allergen induced intestinal eosinophilic inflammation in a mouse model. Clin Immunol 2009; 131:157-69</ref><ref>Song DJ, Cho JY, Lee SY, Miller M, Rosenthal P, Soroosh P, Croft M, Zhang M, Varki A, Broide DH. Anti-Siglec-F antibody reduces allergen-induced eosinophilic inflammation and airway remodeling. J Immunol 2009; 183:5333-41</ref><br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
Mice deficient in Siglec-F have normal blood and bone marrow eosinophils at baseline, but develop exaggerated bone marrow, blood and lung eosinophilia after allergen sensitization and challenge.<ref>Zhang M, Angata T, Cho JY, Miller M, Broide DH, Varki A. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse eosinophils. Blood 2007; 109:4280-7</ref><br />
<br><br />
<br />
=== Glycan array ===<br />
The discovery of the ligand for Siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Bruce Bochner, Paul Crocker, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=MAG&diff=435MAG2010-05-13T18:02:17Z<p>Ron Schnaar: /* Related GBPs */</p>
<hr />
<div>Myelin-associated glycoprotein (MAG, Siglec-4) is unique among the siglecs in that it is expressed exclusively on neuronal glial cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Schnaar 2009">Schnaar, R. L. Brain gangliosides in axon-myelin stability and axon regeneration. FEBS Lett (2009).</ref>. It is the most highly conserved among the siglecs in mammalian species. This siglec paradigm is unique in its activity for stabilizing axon-myelin interactions. MAG has a cytoplasmic domain that is devoid of ITIMs, but contains a tyrosine-based motif associated with binding the FYN tyrosine kinase, believed to play a role in its activity in myelin-axon interactions. MAG recognizes as ligands sialoside sequences found on gangliosides that are abundant in axonal membranes<ref name="Schnaar 2009"/>. It is one of several proteins in myelin that negatively regulate axon outgrowth following tissue injury, an activity that involves MAG ligand interactions. Evidence suggests that inhibition of MAG ligand interactions may enhance neurite outgrowth and repair of injured neurons<ref>Yang, L. J. et al. Sialidase enhances spinal axon outgrowth in vivo. Proc Natl Acad Sci U S A 103, 11057-11062 (2006).</ref><ref>Vyas, A. A., Blixt, O., Paulson, J. C. & Schnaar, R. L. Potent glycan inhibitors of myelin-associated<br />
glycoprotein enhance axon outgrowth in vitro. J Biol Chem 280, 16305-16310 (2005).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Several CFG Participating Investigators (PIs) have contributed to identification of MAG as a siglec and to understanding the functions of MAG, including: Paul Crocker, Sørge Kelm, James Paulson, Ronald Schnaar<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
<br />
<br><br />
=== Cellular expression ===<br />
Myelinating cells like oligodendrocytes or Schwann cells<br />
<br />
<br><br />
<br />
<br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-4&maxresults=20 CFG database search results for Siglec-4].<br />
<br />
=== Glycan profiling ===<br />
<br />
<br><br />
=== Glycogene microarray ===<br />
<br />
<br><br />
=== Knockout mouse lines ===<br />
The CFG has [https://www.functionalglycomics.org/glycomics/publicdata/phenotyping.jsp phenotyped] the MAG-deficient mouse.<br />
<br />
=== Glycan array ===<br />
Investigators have used CFG carbohydrate compounds to study MAG ligand specificity.<br />
<br />
== Related GBPs ==<br />
None.<br />
<br />
<br><br />
<br />
<br><br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, Sorge Kelm, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=434Siglec-82010-05-13T18:01:35Z<p>Ron Schnaar: /* Carbohydrate ligands */</p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. [http://www.ncbi.nlm.nih.gov/pubmed/10856141 Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils.] J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B.S. [http://www.ncbi.nlm.nih.gov/pubmed/19178537 Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors.] Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br />
[[File:6pso3slex.jpg]]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page: Paul Crocker, James Paulson, Ron Schnaar</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:6so3slex.jpg&diff=433File:6so3slex.jpg2010-05-13T18:00:02Z<p>Ron Schnaar: </p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=File:6pso3slex.jpg&diff=431File:6pso3slex.jpg2010-05-13T17:58:54Z<p>Ron Schnaar: </p>
<hr />
<div></div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=396Siglec-82010-05-13T16:46:15Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. [http://www.ncbi.nlm.nih.gov/pubmed/10856141 Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils.] J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B.S. [http://www.ncbi.nlm.nih.gov/pubmed/19178537 Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors.] Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=395Siglec-82010-05-13T16:40:58Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. [http://www.ncbi.nlm.nih.gov/pubmed/10856141 Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils.] J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">[http://www.ncbi.nlm.nih.gov/pubmed/19178537 Bochner, B. S.] Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=394Siglec-82010-05-13T16:37:55Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/10856141 Kikly, K.K.], Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">[http://www.ncbi.nlm.nih.gov/pubmed/19178537 Bochner, B. S.] Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=393Siglec-82010-05-13T16:35:23Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/10856141 Kikly, K.K.], Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=392Siglec-82010-05-13T16:23:24Z<p>Ron Schnaar: /* Biological roles of GBP-ligand interaction */</p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
Eosinophil apoptosis<br />
Inhibition of mast cell effector release<br />
<br><br />
<br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=391Siglec-82010-05-13T16:22:24Z<p>Ron Schnaar: /* Cellular expression */</p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
Human: Eosinophils, Mast Cells, Basophils<br />
<br><br />
<br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=390Siglec-82010-05-13T16:20:42Z<p>Ron Schnaar: /* Carbohydrate ligands */</p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc [6'Su-SLeX]<br />
<br><br />
<br />
=== Cellular expression ===<br />
<br />
<br><br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=389Siglec-82010-05-13T16:17:16Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
NeuAcα2-3(6-SO3)Galβ1-4(Fucα1-3)GlcNAc<br />
<br><br />
=== Cellular expression ===<br />
<br />
<br><br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=388Siglec-82010-05-13T16:11:47Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
<br />
<br><br />
=== Cellular expression ===<br />
<br />
<br><br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaarhttps://glycan.mit.edu/CFGparadigms/index.php?title=Siglec-8&diff=387Siglec-82010-05-13T16:09:50Z<p>Ron Schnaar: </p>
<hr />
<div>Siglec-8 is a human siglec expressed predominantly on eosinophils and mast cells, and is a paradigm for the rapidly evolving sub-family of CD33-related siglecs that are expressed on various white blood cells<ref>Kikly, K.K., Bochner, B.S., et al. Identification of SAF-2, a novel siglec expressed on eosinophils, mast cells, and basophils. J Allergy Clin Immunol 105, 1093-100 (2000)</ref>.<ref>Crocker, P. R., Paulson, J. C. & Varki, A. Siglecs and their roles in the immune system. Nat Rev Immunol 7, 255-266 (2007).</ref><ref name="Bochner 2009">Bochner, B. S. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors. Clin Exp Allergy 39, 317-324 (2009).</ref><ref>Floyd, H. et al. Siglec-8. A novel eosinophil-specific member of the immunoglobulin superfamily. J Biol Chem 275, 861-866 (2000).</ref>. A characteristic feature of Siglec-8 and most other CD33-related siglecs is a cytoplasmic domain with a single immunoreceptor tyrosine inhibitory motif (ITIM) and a single ITIM-like motif that participate in siglec-mediated regulation of cell signaling and endocytosis. While there is no clear ortholog in mice, Siglec-F has been documented as a functional paralog that has a similar expression pattern on murine leukocytes and similar ligand specificity<ref name="Bochner 2009"/><ref>Tateno, H., Crocker, P. R. & Paulson, J. C. Mouse Siglec-F and human Siglec-8 are functionally convergent paralogs that are selectively expressed on eosinophils and recognize 6'-sulfo-sialyl Lewis X as a preferred<br />
glycan ligand. Glycobiology 15, 1125-1135 (2005).</ref><ref>Zhang, M. et al. Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse<br />
eosinophils. Blood 109, 4280-4287 (2007).</ref>. Siglec-8 and its paralog Siglec-F recognize a ligand containing both sialic acid and sulfate (NeuAcα2-3[6S]Galβ1-4G[Fucα1-3]GlcNAc-), a specificity that is distinct from all other siglecs. Ligation of Siglec-8 (or Siglec-F) with antibodies or polymeric ligands induces apoptosis of eosinophils, suggesting a therapeutic approach for treating eosinophil (or mast cell) mediated disease by targeting Siglec-8<ref>O'Reilly, M. K. & Paulson, J. C. Siglecs as targets for therapy in immune-cell-mediated disease. Trends Pharmacol Sci 30, 240-248 (2009).</ref><ref>Zimmermann, N. et al. Siglec-F antibody administration to mice selectively reduces blood and tissue<br />
eosinophils. Allergy 63, 1156-1163 (2008).</ref><ref>Bochner, B. S. et al. Glycan array screening reveals a candidate ligand for Siglec-8. J Biol Chem 280, 4307-<br />
4312 (2005).</ref><ref>Nutku, E., Aizawa, H., Hudson, S. A. & Bochner, B. S. Ligation of Siglec-8: a selective mechanism for induction of human eosinophil apoptosis. Blood 101, 5014-5020 (2003).</ref>.<br />
<br />
== CFG Participating Investigators contributing to the understanding of this paradigm ==<br />
Participating Investigators (PIs) of the CFG have made major contributions to the understanding of the biology of Siglec-8 and its murine paralog, Siglec-F. These include: Bruce Bochner, Nicolai Bovin, Paul Crocker, James Paulson, Ronald Schnaar, Ajit Varki<br />
<br />
== Progress toward understanding this GBP paradigm ==<br />
<br />
=== Carbohydrate ligands ===<br />
<br />
<br><br />
=== Cellular expression ===<br />
<br />
<br><br />
=== Structure ===<br />
<br />
<br><br />
=== Biological roles of GBP-ligand interaction ===<br />
<br />
<br><br />
== CFG resources used in investigations ==<br />
The best examples of CFG contributions to this paradigm are described below, with links to specific data sets. For a complete list of CFG data and resources relating to this paradigm, see the [http://www.functionalglycomics.org/glycomics/search/jsp/landing.jsp?query=Siglec-8&maxresults=20 CFG database search results for Siglec-8].<br />
<br />
=== Glycan profiling ===<br />
Glycan structure analysis has been conducted by the CFG for human and mouse eosinophils.<br />
<br />
=== Glycogene microarray ===<br />
Analysis has been conducted on glycosyltransferase expression using the glycogene microarray for murine eosinophils.<br />
<br />
=== Knockout mouse lines ===<br />
<br />
<br><br />
=== Glycan array ===<br />
The discovery of the ligand for siglec-8 and its murine paralog, Siglec-F, was made by investigator-initiated resource requests for glycan array analysis and carbohydrate compounds.<br />
<br />
== Related GBPs ==<br />
hSiglec-3 (CD33), Siglec-5, Siglec-6, Siglec, 7, Siglec-9, Siglec-10, Siglec-11, Siglec-F, Siglec-E, Siglec-G<br />
<br />
== References ==<br />
<references/><br />
<br />
== Acknowledgements ==<br />
The CFG is grateful to the following PIs for their contributions to this wiki page:</div>Ron Schnaar