| Sialoadhesin | |||||||
|---|---|---|---|---|---|---|---|
 Structure of the N-terminal domain of sialoadhesin.[1] | |||||||
| Identifiers | |||||||
| Symbol | SIGLEC1 | ||||||
| Alt. symbols | SN, CD169 | ||||||
| NCBI gene | 6614 | ||||||
| HGNC | 11127 | ||||||
| OMIM | 600751 | ||||||
| PDB | 2BVE | ||||||
| RefSeq | NM_023068 | ||||||
| UniProt | Q9BZZ2 | ||||||
| Other data | |||||||
| Locus | Chr. 20p13 | ||||||
| |||||||
Sialoadhesin (SIGLEC-1) is acell adhesion molecule found on the surface of variousimmune cells. It is found in especially high amounts onmacrophages of the spleen, liver, lymph node, bone marrow, colon, and lungs.
Soluble SIGLEC-1 is a biomarker of monocyte-macrophage activation insystemic lupus erythematosus (SLE) and other autoimmune disorders.[2] In patients with rheumatoid arthritis, the protein has been found in great amounts on macrophages of the affected tissues.[3] It is defined as an I-typelectin, since it contains 17immunoglobulin (Ig) domains (one variable domain and 16 constant domains), and thus also belongs to theimmunoglobulin superfamily (IgSF).
Sialoadhesin binds to certain molecules calledsialic acids. During this binding process asalt bridge is formed between a highly conservedarginine residue (in the v-set domain) and the carboxylate group of the sialic acid.[3] Since sialoadhesin binds sialic acids with itsN-terminal IgV-domain, it is also a member of theSiglec family. Alternate names for sialoadhesin includesiglec-1 andCD169 (cluster of differentiation 169).[4]
Sialoadhesin predominantly bindsneutrophils, but can also bindmonocytes,natural killer cells,B cells and a subset ofcytotoxic T cells by interacting with sialic acid molecules in theligands on their surfaces.[5]
Sialoadhesin (CD169) positive macrophages, along with mesenchymal stem cells and beta-adrenergic neurons, form thehematopoietic stem cell niche in the bone marrow. CD169+ macrophages mediate signaling between the various cells and seem to promote hematopoietic stem cell retention to the niche.
Siglec-1 is also expressed on lymph node subcapsular sinus macrophages. Research using a murine melanoma model has demonstrated that these subcapsular sinus macrophages bind to sialylated proteins present on the surface of pioneer metastatic cells shortly after their landing in the lymph nodes. This interaction serves as a critical step in metastatic colonization, providing a conducive environment, or 'soil,' for the establishment and proliferation of pioneer metastatic cells, often referred to as 'seeds.'[6]
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