The Annexin family is composed of at least thirteen mammalian genes (Annexin A1-13). These proteins are characterized by a conserved core domain which binds to phospholipids in a Ca2+-dependent manner and a unique amino terminal region which may confer binding specificity. Annexins have roles in membrane fusion, endocytosis, secretion, and repair. Annexin A1 binds to cellular membranes in a calcium-dependent manner, promotes membrane fusion and endocytosis, and has been implicated as an anti-inflammatory mediator. Annexin A2 is a cytoskeletal calcium-dependent phospholipid binding protein, which has been shown to be a mediator of corticosteroid activity, a substrate for serine/threonine kinases and growth regulated tyrosine kinases, and may play a role in secretion. Annexin A5 is a PKC inhibitor, directly interacts with VEGFR2 receptor, and binds phosphatidylserine to inhibit blood coagulation. Annexin A6 reverses transformation of A431 cells after overexpression, and this effect may involve annexin A6 targeting of p120 RasGAP to the plasma membrane to inactivate Ras.
