Seems to play a role in the regulation of RhoA GTPase by guanine nucleotide-binding alpha-12(GNA12) and alpha-13(GNA13) subunits. Acts as GTPase-activating protein(GAP) for GNA12 and GNA13, and as guanine nucleotide exchange factor(GEF) for RhoA GTPase. Activated G alpha 13/GNA13 stimulates the RhoGEF activity through interaction with the RGS-like domain. This GEF activity is inhibited by binding to activated GNA12. Mediates angiotensin-2-induced RhoA activation.