Rho GTPase Activating Protein 21 (ARHGAP21)

ARHGAP21 functions preferentially as a GTPase-activating protein (GAP) for CDC42 and regulates the ARP2/3 complex and F-actin dynamics at the Golgi through control of CDC42 activity.

GST pull-down and mutation analyses showed that the interactions occurred through the PH domain of ARHGAP21. RHOGAP assays indicated that ARHGAP21 acted preferentially on CDC42 over RHOA (ARHA) and RAC1. Small interfering (siRNA) treatment of ARHGAP21 led to constitutive activation of CDC42 that resulted in actin cytoskeleton remodeling, suggesting that ARHGAP21 is required for Golgi complex organization. Loss of ARHGAP21 also caused a massive activation/recruitment of the ARP2/3 complex in the juxtanuclear region.