ArfGap with Rho-Gap domain, ANK repeat and PH domain-containing protein 2
The ARAP subfamily includes three members, ARAP1-3, and belongs to the ADP-ribosylation factor GTPase-activating proteins (Arf GAPs) family of proteins that promotes the hydrolysis of GTP bound to Arf, thereby inactivating Arf signaling. The function of Arfs is dependent on GAPs and guanine nucleotide exchange factors (GEFs), which allow Arfs to cycle between the GDP-bound and GTP-bound forms. In addition to the Arf GAP domain, ARAPs contain the SAM (sterile-alpha motif) domain, 5 pleckstrin homology (PH) domains, the Rho-GAP domain, the Ras-association domain, and ANK repeats. ARAPs show phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3)-dependent GAP activity toward Arf6. ARAPs play important roles in endocytic trafficking, cytoskeleton reorganization in response to growth factors stimulation, and focal adhesion dynamics. ARAP2 localizes to the cell periphery and on focal adhesions composed of paxillin and vinculin, and functions downstream of RhoA to regulate focal adhesion dynamics. ARAP2 is a PI(3,4,5)P3-dependent Arf6 GAP that binds RhoA-GTP, but it lacks the predicted catalytic arginine in the RhoGAP domain and does not have RhoGAP activity. ARAP2 reduces Rac1oGTP levels by reducing Arf6oGTP levels through GAP activity. AGAP2 also binds to and regulates focal adhesion kinase (FAK). Thus, ARAP2 signals through Arf6 and Rac1 to control focal adhesion morphology.