Recombinant Mouse CD9 antigen (Cd9) Protein

Function

Integral membrane protein associated with integrins, which regulates different processes, such as sperm-egg fusion, platelet activation and aggregation, and cell adhesion (PubMed:10634790, PubMed:10634791, PubMed:10700183, PubMed:14715942). Present at the cell surface of oocytes and plays a key role in sperm-egg fusion, possibly by organizing multiprotein complexes and the morphology of the membrane required for the fusion (PubMed:10634790, PubMed:10634791, PubMed:10700183, PubMed:21690351). In myoblasts, associates with CD81 and PTGFRN and inhibits myotube fusion during muscle regeneration (PubMed:23575678). In macrophages, associates with CD9 and beta-1 and beta-2 integrins, and prevents macrophage fusion into multinucleated giant cells specialized in ingesting complement-opsonized large particles. Also prevents the fusion between mononuclear cell progenitors into osteoclasts in charge of bone resorption (PubMed:12796480). Acts as a receptor for PSG17 (PubMed:11805154). Involved in platelet activation and aggregation (PubMed:14715942). Regulates paranodal junction formation (PubMed:14715942). Involved in cell adhesion, cell motility and tumor metastasis (By similarity). Also regulates integrin-dependent migration of macrophages, particularly relevant for inflammatory response in the lung (PubMed:18662991)

Subcellular Location

Cell membrane (Multi-pass membrane protein); Membrane (Multi-pass membrane protein); Secreted, extracellular exosome

Tissue Specificity

Expressed predominantly in the peripheral nervous system (PubMed:14715942). Highly expressed in oocytes and blastocysts (at protein level) (PubMed:10518536, PubMed:10634790, PubMed:10634791, PubMed:23213457). Expression is also observed on follicular oocytes in the ovary, whereas no expression is found on follicular cells (at protein level) (PubMed:10518536, PubMed:10634790). Expressed in skeletal muscle mainly in endothelial cells of endomysial capillaries, in satellite cells and myoblasts (at protein level)

Subunit

Forms both disulfide-linked homodimers and higher homooligomers as well as heterooligomers with other members of the tetraspanin family (By similarity). Interacts (via the second extracellular domain) with integrin ITGAV:ITGB3 (By similarity). Interacts with integrin ITGA6:ITGB1; interaction takes place in oocytes and is involved in sperm-egg fusion (PubMed:10634791). Part of integrin-tetraspanin complexes composed of CD81, beta-1 and beta-2 integrins in the membrane of monocyte/macrophages (By similarity). Interacts with CD63; identified in a complex with CD63 and ITGB3 (By similarity). Associates with CR2/CD21 and with PTGFRN/CD9P1 (By similarity). Part of a complex composed of CD9, CD81, PTGFRN and IGSF8 (PubMed:23575678). Interacts directly with IGSF8 (By similarity). Interacts with PDPN; this interaction is homophilic and attenuates platelet aggregation and pulmonary metastasis induced by PDPN (By similarity)

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• Carninci P. et al. The transcriptional landscape of the mammalian genome. — Science (2005)
• The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). — Genome Res. (2004)
• Kaji K. et al. The gamete fusion process is defective in eggs of Cd9-deficient mice. — Nat. Genet. (2000)
• Chen M.S. et al. Role of the integrin-associated protein CD9 in binding between sperm ADAM 2 and the egg integrin alpha6beta1: implications for murine fertilization. — Proc. Natl. Acad. Sci. U.S.A. (1999)
• Le Naour F. et al. Severely reduced female fertility in CD9-deficient mice. — Science (2000)
• Miyado K. et al. Requirement of CD9 on the egg plasma membrane for fertilization. — Science (2000)
• Zhu G.-Z. et al. Residues SFQ (173-175) in the large extracellular loop of CD9 are required for gamete fusion. — Development (2002)