Mutation of an N-terminal acidic-rich region of p115-RhoGEF dissociates alpha13 binding and alpha13-promoted plasma membrane recruitment.

The Ras homology (Rho) guanine nucleotide exchange factor p115-RhoGEF couples the alpha(13) heterotrimeric guanine nucleotide binding protein (G protein) subunit to Rho GTPase. Alpha(13) binds to a regulator of G protein signaling (RGS) domain in p115-RhoGEF, but the mechanism of alpha(13) activation of p115-RhoGEF is poorly understood. In this report, we demonstrate in cell-based assays that the acidic-rich N-terminus, adjacent to the RGS domain, is required for binding to activated alpha(13), and refine the importance of this region by showing that mutation of glutamic acids 27 and 29 in full-length p115-RhoGEF is sufficient to prevent interaction with activated alpha(13). However, alpha(13)-interacting deficient N-terminal mutants of p115-RhoGEF retain alpha(13)-dependent plasma membrane recruitment. Overall, these findings demonstrate a critical role for the N-terminal extension of p115-RhoGEF in mediating binding to alpha(13) and dissociate two activities of p115-RhoGEF: binding to activated alpha(13) and translocation to the PM in response to activated alpha(13).