THE PROLINE-RICH REGION OF VAV BINDS TO GRB2, AND GRB3-3

Vav has structural features found in signaling proteins and is express ed only in hematopoietic cells. The recent development of mice Vav (-/ -) has confirmed a major role of Vav in early blood cell development. We previously showed that Vav constitutively interacts with glutathion e-S-transferase-Grb2. Coimmunoprecipitation experiments supported the idea of a complex formed by Vav-Grb2 in vivo. This complex is of poten tial interest in signaling of hematopoietic cells. In this work we loc alize the domains of Vav and Grb2 involved in this interaction. By the use of an in vivo genetic approach (the double hybrid system) and thr ough in vitro experiments (glutathione-S-transferase fusion proteins) me furnish evidence that the interaction between Vav and Grb2 involves the C-SH3 domain of Grb2 and the proline-rich region located in the N -SH3 of Vav. Furthermore this was confirmed by the use of both Vav and Sos derived proline-rich peptides which blocked the binding. Tn addit ion me show that Vav also interacts with Grb3-3, a naturally occurring Grb2 isoform wich lacks functional SH2 domain.