The INDIVIDUALIST

A Wiki about biochemical individuality

Lectinology

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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.(1)

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. (2)

HGNC
Approved Symbol
Approved Name
Alias
Previous Symbol
Acc ID
PMID
Location
11127SNsialoadhesinSIGLEC-1, CD169 AF230073853004820p13
1643CD22CD22 antigenSIGLEC-2 X52785849660219q13.1
1659CD33CD33 antigen (gp67)SIGLEC-3 M23197313976619q13.3
6783 MAGmyelin associated glycoproteinSIGLEC-4AGMAM29273247698719q13.1
10874SIGLEC5sialic acid binding Ig-like lectin 5OB-BP2, SIGLEC-5CD33L2U713831034311619q13.3
10875SIGLEC6sialic acid binding Ig-like lectin 6OB-BP1, SIGLEC-6CD33L, CD33L1D86358946590719q13.3
10876SIGLEC7sialic acid binding Ig-likelectin 7SIGLEC-7, p75/AIRM1, QA79 AF170481056737719q13.3
10877SIGLEC8sialic acid binding Ig-likelectin 8SIGLEC-8 AF1950921062561919q13.33-q13.41
10878SIGLEC9sialic acid binding Ig-likelectin 9  AF1350271090384219q13.3-q13.4
15620SIGLEC10sialic acid binding Ig-likelectin 10  AF3102331128473819q13.3
15622SIGLEC11sialic acid binding Ig-likelectin 11  AF337818 19q13.3
15482SIGLEC12sialic acid binding Ig-like lectin12SLG,S2V, Siglec-XII, Siglec-12  SIGLECL1AF2822561140987719q13.4
15491SIGLECP1sialic acid binding Ig-likelectin, pseudogene 1   1154677719q13.3
15603SIGLECP2sialic acid binding Ig-likelectin, pseudogene 2   1154677719q13.3
15604SIGLECP3sialic acid binding Ig-likelectin, pseudogene 3   1154677719q13.3
15609SIGLECP4sialic acid binding Ig-likelectin, pseudogene 4   1154677719q13.3
15610SIGLECP5sialic acid binding Ig-likelectin, pseudogene 5   1154677719q13.3
15611SIGLECP6sialic acid binding Ig-likelectin, pseudogene 6   1154677719q13.3
15612SIGLECP7sialic acid binding Ig-likelectin, pseudogene 7   1154677719q13.3
15613SIGLECP8sialic acid binding Ig-likelectin, pseudogene 8   1154677719q13.3
15614SIGLECP9sialic acid binding Ig-likelectin, pseudogene 9   1154677719q13.3
15615SIGLECP10sialic acid binding Ig-likelectin, pseudogene 10   1154677719q13.3
15617SIGLECP11sialic acid binding Ig-likelectin, pseudogene 11   1154677719q13.3
15618SIGLECP12sialic acid binding Ig-likelectin, pseudogene 12   1154677719q13.3
15619SIGLECP13sialic acid binding Ig-likelectin, pseudogene 13   1154677719q13.3
15623SIGLECP14sialic acid binding Ig-likelectin, pseudogene 14   115467771
16072SIGLECP15sialic acid binding Ig-likelectin, pseudogene 15   1154677719
24851SIGLECP16sialic acid binding Ig-like lectin, pseudogene 16Siglec-P161198632719q13.3
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References

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