Mutation of an N-terminal acidic-rich region of p115-RhoGEF dissociates α13 binding and α13 -promoted plasma membrane recruitment

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Abstract
The Ras homology (Rho) guanine nucleotide exchange factor p115-RhoGEF couples the α13 heterotrimeric guanine nucleotide binding protein (G protein) subunit to Rho GTPase. α13 binds to a regulator of G protein signaling (RGS) domain in p115-RhoGEF, but the mechanism of α13 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 α13, 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 α13. However, α13-interacting deficient N-terminal mutants of p115-RhoGEF retain α13-dependent plasma membrane recruitment. Overall, these findings demonstrate a critical role for the N-terminal extension of p115-RhoGEF in mediating binding to α13 and dissociate two activities of p115-RhoGEF: binding to activated α13 and translocation to the PM in response to activated α13