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Siglecs

Lectinology

See Also

• 19q13.3
• Carbohydrates as Biological Markers
• Cell Adhesion Molecules (CAMs)
• Glycans
• Glycoconjugates
• Sialogens
• Sialic acid
• Zeta-potential

Description

Siglecs are a group of adhesion receptors with tyrosine-based inhibitory signaling motifs. They are mainly expressed by cells of the hematopoietic system. Recently new members of the Siglec family were identified both in the human and the mouse. These comprise a CD33-related subgroup. All Siglecs specifically recognize sialic acids that are broadly expressed on many cell surfaces. These properties suggest that Siglecs may be involved in cell-cell interactions resulting in intracellular inhibitory signals.({{http://eurekah.com/abstract.php?chapid=1131&bookid=93&catid=36}})

I-type lectins are a family of carbohydrate-binding proteins within the immunoglobulin superfamily. Included are a group of sialic-acid-binding lectins (the Siglecs) and several non-sialic-acid-binding lectins.

A very significant feature of the Siglecs is their recognition of sialic-acid-containing structures in a linkage-specific manner. CD22 is absolutely specific for α2-6-linked sialic acid residues and MAG, Schwann cell myelin protein, and CD33, for α2-3-linked sialic acid residues; sialoadhesin can recognize α2-3-linked and α2-8-linked residues. The initial analysis of Siglec-5 using synthetic sialosides indicates that it is capable of binding to α2-3- and α2-6-linked sialic acid residues.

Genomics

Chromosomal localization studies indicate that CD22, CD33, Siglec-5, and MAG are clustered on human chromosome 19q and the syntenic murine chromosome 7. Twenty related genes of the IgSF, including members of the carcinoembryonic antigen and pregnancy-specific glycoprotein families, are also found in close proximity, suggesting their evolutionary origin by gene duplication. Sialoadhesin maps to murine chromosome 2 and human chromosome 20 (determined using the murine sialoadhesin as a probe), and thus is unlinked to the other Siglecs in both species. The presence of other Siglecs in proximity to the sialoadhesin gene has yet to be explore

Sialoadhesin

Compared to the other Siglecs, sialoadhesin binds to the widest array of sialylated structures. Early studies demonstrated binding to α2-3 sialic acid residues, including Siaα2-3Galβ1-3GalNAc and Siaα2-3Galβ1-3(4)GlcNAc. These structures are the products of several different α2-3-specific sialyltransferases and can be found on glycolipids and N-linked and O-linked chains on glycoproteins . More recently, sialoadhesin has been demonstrated to bind to gangliosides carrying terminal α2-8 sialic acid residues such as GD3 and GD1b. Thus, potential ligands for sialoadhesin are likely to be found on virtually all cell types. However, sialoadhesin (expressed on COS cells, macrophages, or as an Sn-Rg [sialoadhesion-receptor globulin] construct) shows marked preference for binding to granulocytes and erythroblasts over other cell types. ({{http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=glyco.section.1787}})

HGNC	Approved Symbol	Approved Name	Alias	Previous Symbol	Acc ID	PMID	Location
11127	SN	sialoadhesin	SIGLEC-1, CD169		AF230073	8530048	20p13
1643	CD22	CD22 antigen	SIGLEC-2		X52785	8496602	19q13.1
1659	CD33	CD33 antigen (gp67)	SIGLEC-3		M23197	3139766	19q13.3
6783	MAG	myelin associated glycoprotein	SIGLEC-4A	GMA	M29273	2476987	19q13.1
10874	SIGLEC5	sialic acid binding Ig-like lectin 5	OB-BP2, SIGLEC-5	CD33L2	U71383	10343116	19q13.3
10875	SIGLEC6	sialic acid binding Ig-like lectin 6	OB-BP1, SIGLEC-6	CD33L, CD33L1	D86358	9465907	19q13.3
10876	SIGLEC7	sialic acid binding Ig-likelectin 7	SIGLEC-7, p75/AIRM1, QA79		AF17048	10567377	19q13.3
10877	SIGLEC8	sialic acid binding Ig-likelectin 8	SIGLEC-8		AF195092	10625619	19q13.33-q13.41
10878	SIGLEC9	sialic acid binding Ig-likelectin 9			AF135027	10903842	19q13.3-q13.4
15620	SIGLEC10	sialic acid binding Ig-likelectin 10			AF310233	11284738	19q13.3
15622	SIGLEC11	sialic acid binding Ig-likelectin 11			AF337818		19q13.3
15482	SIGLEC12	sialic acid binding Ig-like lectin12	SLG,S2V, Siglec-XII, Siglec-12	SIGLECL1	AF282256	11409877	19q13.4
15491	SIGLECP1	sialic acid binding Ig-likelectin, pseudogene 1				11546777	19q13.3
15603	SIGLECP2	sialic acid binding Ig-likelectin, pseudogene 2				11546777	19q13.3
15604	SIGLECP3	sialic acid binding Ig-likelectin, pseudogene 3				11546777	19q13.3
15609	SIGLECP4	sialic acid binding Ig-likelectin, pseudogene 4				11546777	19q13.3
15610	SIGLECP5	sialic acid binding Ig-likelectin, pseudogene 5				11546777	19q13.3
15611	SIGLECP6	sialic acid binding Ig-likelectin, pseudogene 6				11546777	19q13.3
15612	SIGLECP7	sialic acid binding Ig-likelectin, pseudogene 7				11546777	19q13.3
15613	SIGLECP8	sialic acid binding Ig-likelectin, pseudogene 8				11546777	19q13.3
15614	SIGLECP9	sialic acid binding Ig-likelectin, pseudogene 9				11546777	19q13.3
15615	SIGLECP10	sialic acid binding Ig-likelectin, pseudogene 10				11546777	19q13.3
15617	SIGLECP11	sialic acid binding Ig-likelectin, pseudogene 11				11546777	19q13.3
15618	SIGLECP12	sialic acid binding Ig-likelectin, pseudogene 12				11546777	19q13.3
15619	SIGLECP13	sialic acid binding Ig-likelectin, pseudogene 13				11546777	19q13.3
15623	SIGLECP14	sialic acid binding Ig-likelectin, pseudogene 14				11546777	1
16072	SIGLECP15	sialic acid binding Ig-likelectin, pseudogene 15				11546777	19
24851	SIGLECP16	sialic acid binding Ig-like lectin, pseudogene 16	Siglec-P16			11986327	19q13.3

[http://www.gene.ucl.ac.uk/nomenclature/genefamily/siglec.html]

Links

• Biochemistry and Biology of the Siglec Family

References

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