Rho GTPase-activating protein involved in cell polarity, cell morphology and cytoskeletal organization. Acts as a GTPase activator for the Rac-type GTPase by converting it to an inactive GDP-bound state. Controls actin remodeling by inactivating Rac downstream of Rho leading to suppress leading edge protrusion and promotes cell retraction to achieve cellular polarity. Able to suppress RAC1 and CDC42 activity in vitro. Overexpression induces cell rounding with partial or complete disruption of actin stress fibers and formation of membrane ruffles, lamellipodia, and filopodia. Isoform 2 is a vascular cell-specific GAP involved in modulation of angiogenesis. Interacts with FLNA. Localizes to actin stress fibers. In migrating cells, localizes to membrane lamellae and protusions. Isoform 1 is widely expressed with a higher level in kidney. Isoform 2 is mainly expressed in endothelial cells. Up-regulated during capillary tube formation in umbilical vein endothelial cells. The coiled coil domain mediates the interaction with FLNA leading to its recruitment to lamellae. Phosphorylated by ROCK, leading to activate the RacGAP activity.