SIGLEC
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Siglecs, short for sialic acid binding Ig-like lectins are cell surface receptors and members of the immunoglobulin superfamily (IgSF) that recognize sialic acids. Their ability to recognize sialic acids using an immunoglobulin domain places them in the group of I-type (Ig-type) lectins. They are transmembrane proteins that contain an N-terminal V-like immunoglobulin (IgV) domain that binds sialic acid and a variable number of C2-type Ig (IgC2) domains.[1][2]
The first described candidate Siglec was sialoadhesin (Siglec-1/CD169) a lectin-like adhesion protein on macrophages.[3] Parallel studies by Ajit Varki and colleagues on the already cloned CD22 ( a B cell molecule involved in adhesion and activation) showed direct evidence for sialic acid recognition. The subsequent cloning of sialoadhesin by Crocker revealed homology to CD22 (Siglec-2), CD33 (Siglec-3) and myelin-associated glycoprotein (MAG/Siglec-4), leading to a proposal for a family of "sialoadhesins". Varki then suggested the term Siglec as better alternative, and as a subset of I-type (Ig-type) lectins. This nomenclature was agreed upon and has been adopted by almost all investigators working on these molecules. Several additional Siglecs (Siglecs 5–12) have been identified in humans that are highly similar in structure to CD33 so are collectively referred to as ‘CD33-related Siglecs’ [4][5]. The inhibitory subset of CD33-related siglecs all have two conserved immunoreceptor tyrosine-based inhibitory motif (ITIM)-like motifs in their cytoplasmic tails suggesting their involvement in cellular activation.[4]
[edit] References
- ^ Crocker P, Clark E, Filbin M, Gordon S, Jones Y, Kehrl J, Kelm S, Le Douarin N, Powell L, Roder J, Schnaar R, Sgroi D, Stamenkovic K, Schauer R, Schachner M, van den Berg T, van der Merwe P, Watt S, Varki A (1998). "Siglecs: a family of sialic-acid binding lectins". Glycobiology 8 (2): v. doi:10.1093/glycob/8.2.0. PMID 9498912.
- ^ Siglecs
- ^ discovered by Paul Crocker and shown to recognize sialic acids Crocker P, Gordon S (1986). "Properties and distribution of a lectin-like hemagglutinin differentially expressed by murine stromal tissue macrophages". J Exp Med 164 (6): 1862–75. doi:10.1084/jem.164.6.1862. PMC 2188478. PMID 3783087. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2188478.
- ^ a b Crocker P, Varki A (2001). "Siglecs in the immune system". Immunology 103 (2): 137–45. doi:10.1046/j.0019-2805.2001.01241.x. PMC 1783234. PMID 11412300. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1783234.
- ^ Angata T, Kerr S, Greaves D, Varki N, Crocker P, Varki A (2002). "Cloning and characterization of human Siglec-11. A recently evolved signaling that can interact with SHP-1 and SHP-2 and is expressed by tissue macrophages, including brain microglia". J Biol Chem 277 (27): 24466–74. doi:10.1074/jbc.M202833200. PMID 11986327.
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