The C-terminal SH3 domain contributes to the intramolecular inhibition of Vav family proteins

Vav proteins are phosphorylation-dependent guanine nucleotide exchange factors (GEFs) that catalyze the activation of members of the Rho family of guanosine triphosphatases (GTPases). The current regulatory model holds that the nonphosphorylated, catalytically inactive state of these GEFs is maintained by intramolecular interactions among the amino-terminal domains and the central catalytic core, which block the binding of Vav proteins to GTPases. We showed that this autoinhibition is mechanistically more complex, also involving the bivalent association of the carboxyl-terminal Src homology 3 (SH3) region of Vav with its catalytic and pleckstrin homology (PH) domains. Such interactions occurred through proline-rich region-independent mechanisms. Full release from this double-locked state required synergistic weakening effects from multiple phosphorylated tyrosine residues, thus providing an optimized system to generate gradients of Vav GEF activity depending on upstream signaling inputs. This mechanism is shared by mammalian and Drosophila melanogaster Vav proteins, suggesting that it may be a common regulatory feature for this protein family.Work in the laboratory of X.R.B. has been funded by grants from the Spanish Ministry of Economy and Competitiveness (SAF2009-07172, SAF2012-3171, RD06/0020/0001, and RD12/0036/0002), the Castilla-León Autonomous Government (CSI039A12-1), and the Asociación Española Contra el Cáncer (AECC). O.L. has been supported by grants from the Spanish Ministry of Economy and Competitiveness (SAF2011-22988 and RD06/0020/1001). The salary of M.B. has been partially supported by a JAE-Predoc contract (CSIC), the AECC, and grant RD06/0020/0001. S.F. is supported by a graduate student FPI contract from the Spanish Ministry of Economy and Competitiveness (BES-2010-031386). Spanish funding is cosponsored by the European Regional Development Fund.Peer Reviewe