p190RhoGAP has cellular RacGAP activity regulated by a polybasic region

Abstract

ABSTRACTp190RhoGAP is a GTPase-activating protein (GAP) known to regulate actin cytoskeleton dynamics by decreasing RhoGTP levels through activation the intrinsic GTPase activity of Rho. Although the GAP domain of p190RhoGAP stimulates the intrinsic GTPase activity of several Rho family members (Rho, Rac, Cdc42) under in vitro conditions, p190RhoGAP is generally regarded as a GAP for RhoA in the cell. The cellular RacGAP activity of the protein has not been proved directly. We have previously shown that the in vitro RacGAP and RhoGAP activity of p190RhoGAP was inversely regulated through a polybasic region of the protein. Here we provide evidence that p190RhoGAP shows remarkable GAP activity toward Rac also in the cell. The cellular RacGAP activity of p190RhoGAP requires an intact polybasic region adjacent to the GAP domain whereas the RhoGAP activity is inhibited by the same domain. Our data indicate that through its alternating RacGAP and RhoGAP activity, p190RhoGAP probably plays a more complex role in the Rac-Rho antagonism than it was realized earlier.

Role of Rac GTPase activating proteins in regulation of NADPH oxidase in human neutrophils

“…In contrast to ARHGAP1 and ARHGAP25, depletion of ARHGAP35 to a similar extent had no effect on the enzyme activity of Nox2, although the RacGAP activity of ARHGAP35 has been confirmed also in cellular context [61] . The lack of effect upon immunodepletion of ARHGAP35 agrees with data obtained in mice with ARHGAP35-deficient hemopoetic system [62].…”

The neglected terminators: Rho family GAPs in neutrophils

“…28,29 Opposing alteration of the Rac and RhoGAP activity could be verified also in cellular functions. 30 In contrast, phosphorylation of four amino acids at the C-terminal end of p190-A by GSK decreases both the Rac and the RhoGAP activity of the protein. 31,32 Although the regulatory function could be demonstrated both with human proteins and with murine cells, contribution of the protein to integrin activation differs in human and murine neutrophils.…”

Crossroads of PI3K and Rac pathways

“…cdGAPs contain a polybasic region (PBR) able to interact with PtdIns(3,4,5)P 3 and this binding is required for full inactivation of Rac1 signaling. 87,88 PtdIns(3,4,5)P 3 -binding domains have been also identified in other GAPs, such as p190 Rho-GAPs that possess a PBR (polybasic region) domain able to recognize phosphorylated lipids, 89,90 and the ArhGAP family, characterized by a PH domain. 91 In particular, ArhGAP15 has been suggested to be activated downstream of PI3Kg and to negatively regulate Rac activity in C5a-stimulated bone marrow-derived macrophages.…”