Siglec
protein family
Siglecs (Sialic acid-binding immunoglobulin-type lectins) are cell surface proteins that bind sialic acids. They are found primarily on the surface of immune cells and are a subset of the I-type lectins. There are 14 different mammalian Siglecs, mediating an array of different functions based on cell surface receptor-ligand interactions.
History
The first described candidate Siglec was Sialoadhesin (Siglec-1/CD169) a lectin-like adhesion protein on macrophages. Parallel studies by Ajit Varki and colleagues on the previously cloned CD22 (a B cell surface protein 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 the proposal for a family of "Sialoadhesins". Varki then suggested the term Siglec as a 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 (by convention, Siglecs are always capitalised.) Several additional Siglecs (Siglecs 5–12) have been identified in humans that are highly similar in structure to CD33 and so are collectively referred to as "CD33-related Siglecs". Further Siglecs have been identified including Siglec-14 and Siglec-15. Siglecs have been characterized into two distinct groups: the first and highly conserved-across-mammals group composed of Sialoadhesins, CD22, MAG, and Siglec-15, and a second group comprising Siglecs closely related to CD33.
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This entry incorporates text from “Siglec” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.