Direct stimulation of the guanine nucleotide exchange activity of p115 RoGEF by Gα₁₃

Signaling pathways that link extracellular factors to activation of the monomeric guanosine triphosphatase (GTPase) Rho control cytoskeletal rearrangements and cell growth. Heterotrimeric guanine nucleotide-binding proteins (G proteins) participate in several of these pathways, although their mechanisms are unclear. The GTPase activities of two G protein α subunits, Gα₁₂ and Gα₁₃, are stimulated by the Rho guanine nucleotide exchange factor p115 RhoGEF. Activated Gα₁₃ bound tightly to p115 RhoGEF and stimulated its capacity to catalyze nucleotide exchange on Rho. In contrast, activated Gα₁₂ inhibited stimulation by Gα₁₃. Thus, p115 RhoGEF can directly link heterotrimeric G protein α subunits to regulation of Rho.