Vav: Captain Hook for signal transduction?

The binding of growth factors to membrane receptors leads to transmission of signals through the cytoplasm and into the nucleus. One of the proteins that is involved in linking tyrosine phosphorylation and subsequent signal transduction events is proto-vav. Vav was first identified as a transforming gene by the use of the nude mice tumorigenicity assay. The vav protooncogene encodes a protein with motifs usually found in nucleotide exchange factors, as well as those found in substrates of signal transduction (Src Homology 2-SH2 and Src Homology 3-SH3). Based on the transforming potential of vav, its exclusive expression in hematopoietic cells and its encoded protein structure, it is suggested that the vav protooncogene functions as an important mediator in hematopoietic signal transduction, resulting in cell growth and/or differentiation. In this review I discuss the evidence that proto-vav acts as one of the most pivotal hook elements forsignal transduction in the hemopoietic system.