GTPase-activating proteins (GAPs) accelerate the intrinsic rate of GTP hydrolysis of Ras-related proteins, resulting in down regulation of their active form. ARHGAP17 (Rho GTPase activating protein 17), also known as RICH1, WBP15, MST066, MST110, NADRIN, PP4534, RICH1B, MSTP038, MSTP066 or MSTP110, is a ubiquitously expressed peripheral membrane protein whose expression is highest in heart and placenta. ARHGAP17 is involved in the maintenance of tight junctions by regulating the activity of Cdc42, thereby playing a central role in apical polarity of epithelial cells. Containina a BAR domain and a Rho-GAP domain, ARHGAP17 acts as a GTPase activator for the Cdc42 GTPase by converting it to an inactive GDP-bound state. ARHGAP17 may also participate in the Ca2+-dependent regulation of exocytosis by catalyzing
GTPase activity of Rho family proteins and by inducing the reorganization of cortical actin filaments. ARHGAP17 exists as seven alternative splice variants.