CD9 antigen

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).

Palmitoylated at a low, basal level in unstimulated platelets. The level of palmitoylation increases when platelets are activated by thrombin (in vitro). The protein exists in three forms with molecular masses between 22 and 27 kDa, and is known to carry covalently linked fatty acids. Palmitoylation by ZDHHC2 regulates CD9 expression, association with other tetraspanin family proteins and function in cell adhesion.

Belongs to the tetraspanin (TM4SF) family.

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).

• Cell membrane
• Multi-pass membrane protein
• Membrane
• Multi-pass membrane protein
• Secreted
• Extracellular exosome
• Present at the cell surface of oocytes (PubMed:10518536, PubMed:10634791, PubMed:23213457). Accumulates in the adhesion area between the sperm and egg following interaction between IZUMO1 and its receptor IZUMO1R/JUNO (PubMed:25209248).

CD9, CD9 antigen, Cd9

• entrezGene:12527
• swissprot:P40240

Proteins

Oncology

25258Da