Species Human Entrez 6402 | Human Mouse Ensembl ENSG00000188404 | |
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Aliases SELL, CD62L, LAM1, LECAM1, LEU8, LNHR, LSEL, LYAM1, PLNHR, TQ1, selectin L External IDs MGI: 98279 HomoloGene: 539 GeneCards: SELL | ||
L-selectin, also known as CD62L, is a cell adhesion molecule found on lymphocytes and the preimplantation embryo. It belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups. It is cleaved by ADAM17.
Contents
SELL is a cell surface component that is a member of a family of adhesion/homing receptors that play important roles in lymphocyte-endothelial cell interactions. The molecule is composed of multiple domains: one homologous to lectins, one to epidermal growth factor, and two to the consensus repeat units found in C3/C4-binding proteins.
Ligands
Function
L-selectin acts as a "homing receptor" for lymphocytes to enter secondary lymphoid tissues via high endothelial venules. Ligands present on endothelial cells will bind to lymphocytes expressing L-selectin, slowing lymphocyte trafficking through the blood, and facilitating entry into a secondary lymphoid organ at that point. The receptor is commonly found on the cell surfaces of T cells. Naive T-lymphocytes, which have not yet encountered their specific antigen, need to enter secondary lymph nodes to encounter their antigen. Central memory T-lymphocytes, which have encountered antigen, express L-selectin to localize in secondary lymphoid organs. Here they reside ready to proliferate upon re-encountering antigen. Effector memory T-lymphocytes do not express L-selectin, as they circulate in the periphery and have immediate effector functions upon encountering antigen.
High expression of L-selectin on human bone marrow progenitor cells is an early sign of cells becoming committed to lymphoid differentiation.
L-selectin is also present on the surface of human embryo trophoblasts prior to implantation into the uterus. Similar to its function in lymphocytes, L-selectin acts as a receptor to facilitate adhesion of the embryo to the site of invasion on the surface epithelium of the uterine endometrium. The embryo secretes human chorionic gonadotropin (hCG), which downregulates anti-adhesion factor, MUC-1, located on the uterine epithelium at the site of invasion. Removal of MUC-1 exposes the oligosaccharide ligands of the uterine epithelium, thus allowing binding by the L-selectin receptor of the trophopblast cell, followed by embryo adhesion and invasion.