Vav links antigen-receptor signaling to the actin cytoskeleton.

The haematopoietic-specific Rho-family guanine-nucleotide exchange factor Vav is a regulator of lymphocyte antigen receptor signaling leading to proliferation of B and T cells, generation of the B1 cell lineage and IL-2 production and maturation in T cells. The specific role it plays in these events, however, has not yet been resolved. Recent findings suggest that Vav is recruited to activated antigen receptors and requires both tyrosine phosphorylation and the presence of activating phospholipids for catalytic activity towards Rho-family GTPases. Studies form vav-deficient mice show that in response to antigen receptor activation, Vav is not essential for activation of JNK kinase pathways, but is required for actin polymerisation and T cell capping. We discuss Vav function in the light of these new findings.