p200 RhoGAP Promotes Cell Proliferation by Mediating Cross-talk between Ras and Rho Signaling Pathways

Abstract

p200 RhoGAP, a member of the Rho GTPase-activating protein (RhoGAP) family, was previously implicated in the regulation of neurite outgrowth through its RhoGAP activity. Here we show that ectopic expression of p200 RhoGAP stimulates fibroblast cell proliferation and cell cycle progression, leading to transformation. The morphology of the foci induced by p200 RhoGAP is distinct from that formed by Rac or Rho activation but similar to that induced by oncogenic Ras, raising the possibility that p200 RhoGAP may engage Ras signaling. Expression of p200 RhoGAP results in a significant increase of Ras-GTP and the activation of two downstream signaling pathways of Ras, ERK1/2 and phosphatidylinositol 3-kinase. Inhibition of Ras or ERK1/2, but not phosphatidylinositol 3-kinase, effectively suppresses the foci formation induced by p200 RhoGAP, suggesting that the Ras-ERK pathway is required for p200 RhoGAP-mediated cell transformation. p200 RhoGAP co-localizes with p120 RasGAP in cells and forms a complex with p120 RasGAP, and this interaction is mediated by the C-terminal region and the Src homology 3 domain of p200 RhoGAP and p120 RasGAP, respectively. Mutations of p200 RhoGAP that disrupt interaction with p120 RasGAP abolish its Ras activation and cell transforming activities. Interestingly, the RhoGAP activity of the N-terminal RhoGAP domain in p200 RhoGAP is also required for its full transforming activity, and expression of a dominant negative RhoA mutant that blocks RhoA cycling between the GDP-and GTP-bound states suppresses p200 RhoGAP transformation. These results suggest that a Rho GTPase-activating protein may have a positive input to cell proliferation and provide evidence that p200 RhoGAP can mediate cross-talks between Ras-and Rho-regulated signaling pathways in cell growth regulation.

MgcRacGAP restricts active RhoA at the cytokinetic furrow and both RhoA and Rac1 at cell–cell junctions in epithelial cells

“…In contrast, in MO + S386E and MO + R384A embryos, we observed significant increases in the intensity of RhoA-GTP at the contractile ring, the width of the RhoA activity zone, and the width of F-actin at the contractile ring ( Figure 3, A–D , and Supplemental Movie S5). To confirm that the MgcR384A phenotypes observed in vivo were due to the loss of GAP function and not to an unexpected effect caused by the loss of positive charge from the active site of the GAP domain, we tested an alternate GAP-dead mutant, R384K, which does not alter the charge of the active site (Supplemental Figure S3A; Rittinger et al ., 1997a ; Miura et al ., 2002 ; Lavelin and Geiger, 2005 ; Shang et al ., 2007 ). Similar to results with the R384A mutant, cells expressing MO + R384K also fail cytokinesis (Supplemental Figure S3, B and D) and exhibit significantly increased RhoA-GTP intensity at the furrow (Supplemental Figure S3, C and E).…”

p120RasGAP Protein Mediates Netrin-1 Protein-induced Cortical Axon Outgrowth and Guidance

“…The repulsive guidance cue RGMa releases p120RasGAP from that interaction to mediate the inhibition of Ras activity (34). Other studies have shown that the GAP activity of p120RasGAP is inhibited when its N terminus interacts with p190RhoGAP, FAK, p200RhoGAP, or SOCS-3 (53,(61)(62)(63). Tyrosine phosphorylation of these proteins, except for p200RhoGAP, mediated the interaction (53,61,63).…”

SmgGDS antagonizes BPGAP1-induced Ras/ERK activation and neuritogenesis in PC12 cell differentiation

“…In addition, the p200RhoGAP protein not only stimulates the GTPase activities of Rac1 and RhoA in vivo to regulate neurite outgrowth (Moon et al. , 2003) but also increases the Ras-GTP levels to stimulate fibroblast cell proliferation and cell cycle progression, leading to transformation (Shang et al. , 2007).…”