Recombinant Human CD9 antigen (CD9), partial, Biotinylated

Function

Integral membrane protein associated with integrins, which regulates different processes, such as sperm-egg fusion, platelet activation and aggregation, and cell adhesion (PubMed:14575715, PubMed:18541721, PubMed:8478605). 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 (By similarity). In myoblasts, associates with CD81 and PTGFRN and inhibits myotube fusion during muscle regeneration (By similarity). In macrophages, associates with CD81 and beta-1 and beta-2 integrins, and prevents macrophage fusion into multinucleated giant cells specialized in ingesting complement-opsonized large particles (PubMed:12796480). Also prevents the fusion between mononuclear cell progenitors into osteoclasts in charge of bone resorption (By similarity). Acts as a receptor for PSG17 (By similarity). Involved in platelet activation and aggregation (PubMed:18541721). Regulates paranodal junction formation (By similarity). Involved in cell adhesion, cell motility and tumor metastasis (PubMed:7511626, PubMed:8478605)

Subcellular Location

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

Tissue Specificity

Detected in platelets (at protein level) (PubMed:19640571). Expressed by a variety of hematopoietic and epithelial cells (PubMed:19640571)

Subunit

Forms both disulfide-linked homodimers and higher homooligomers as well as heterooligomers with other members of the tetraspanin family (PubMed:14556650). Interacts (via the second extracellular domain) with integrin ITGAV:ITGB3 (PubMed:19640571, PubMed:27993971). Interacts with integrin ITGA6:ITGB1; interaction takes place in oocytes and is involved in sperm-egg fusion (By similarity). Part of integrin-tetraspanin complexes composed of CD81, beta-1 and beta-2 integrins in the membrane of monocyte/macrophages (PubMed:12796480). Interacts with CD63; identified in a complex with CD63 and ITGB3 (PubMed:19640571). Associates with CR2/CD21 and with PTGFRN/CD9P1 (PubMed:11278880). Part of a complex composed of CD9, CD81, PTGFRN and IGSF8 (By similarity). Interacts directly with IGSF8 (PubMed:11504738). Interacts with PDPN; this interaction is homophilic and attenuates platelet aggregation and pulmonary metastasis induced by PDPN (PubMed:18541721). Interacts (on T cell side) with CD81 at immunological synapses between antigen-presenting cells and T cells (PubMed:23858057)

• Boucheix C. et al. Molecular cloning of the CD9 antigen. A new family of cell surface proteins. — J. Biol. Chem. (1991)
• Lanza F. et al. cDNA cloning and expression of platelet p24/CD9. Evidence for a new family of multiple membrane-spanning proteins. — J. Biol. Chem. (1991)
• Miyake M. et al. Identification of the motility-related protein (MRP-1), recognized by monoclonal antibody M31-15, which inhibits cell motility. — J. Exp. Med. (1991)
• Rubinstein E. et al. Organization of the human CD9 gene. — Genomics (1993)
• Kobayashi H. et al. The tetraspanin CD9 is preferentially expressed on the human CD4(+)CD45RA+ naive T cell population and is involved in T cell activation. — Clin. Exp. Immunol. (2004)
• Kim J.W. et al. Identification of a human growth inhibition gene 2 (GIG2). (SEP-)
• PubMed: CI-3C51VTH6B9TFK (SEP-)
• Mural R.J. et al. PubMed: CI-5GBD0VIIJ7C63 (SEP-)