R-Ras Controls Membrane Protrusion and Cell Migration through the Spatial Regulation of Rac and Rho

Abstract

Although it is known that the spatial coordination of Rac and Rho activity is essential for cell migration, the molecular mechanisms regulating these GTPases during migration are unknown. We found that the expression of constitutively activated R-Ras (38V) blocked membrane protrusion and random migration. In contrast, expression of dominant negative R-Ras (41A) enhanced migrational persistence and membrane protrusion. Endogenous R-Ras is necessary for cell migration, as cells that were transfected with siRNA for R-Ras did not migrate. Expression of R-Ras (38V) decreased Rac activity and increased Rho activity around the entire cell periphery, whereas expression of dominant negative R-Ras (41A) showed the converse, suggesting that R-Ras can spatially activate Rho and inactivate Rac. Consistent with this role, endogenous R-Ras localized and was preferentially activated at the leading edge of migratory cells in response to adhesion. The effects of R-Ras on cell migration are mediated by PI3-Kinase, as an effector mutant that uncouples PI3-Kinase binding from R-Ras (38V) rescued migration. From these data, we hypothesize that R-Ras plays a key role in cell migration by locally regulating the switch from Rac to Rho activity after membrane protrusion and adhesion.

Mechanism of Akt1 inhibition of breast cancer cell invasion reveals a protumorigenic role for TSC2

“…3B). Consistent with the implication that compromised cell motility and invasiveness in myr-Akt1-expressing cells was due to inhibition of Rho activity, treatment with exoenzyme C3 transferase (C3 toxin), which inhibits Rho when added to the media (45,46), was as effective at blocking cell migration as was expression of myrAkt1 (Fig. 3C).…”

Semaphorin Signals in Cell Adhesion and Cell Migration: Functional Role and Molecular Mechanisms

“…7 Notably, two conserved arginine residues are essential for R-Ras inactivation by plexins, and their point mutation results in the loss of most (although not all) functional responses mediated by plexins. 68,73,91 R-Ras is a major positive regulator of integrin function: 92 it gets activated upon cell contact to the ECM, 93 and in turn it sustains the clustering and activation of β1-integrin receptors (as well as others), it enhances focal adhesion formation and cell adhesion, and it regulates positively cell spreading, cell migration and invasion, as well as axon outgrowth (for a general review see ref. functions qualify R-Ras as the ideal target for the inhibitory activity of semaphorins; nonetheless the molecular mechanisms involved in this pathway are presently unclear.…”

“…However, two recent reports demonstrated that R-Ras signaling instead induces RhoA activation and Rac1 inactivation at the leading edge, via still unknown pathways. 93,97 Therefore, further studies are required to elucidate the mechanism whereby R-Ras inactivation mediated by semaphorins may regulate cell adhesion and cell migration.…”

Structure, functional regulation and signaling properties of Rap2B

“…In 2002, Evellin et al (76) demonstrated that PLC-ε appeared to be stimulated by GPCRs through the formation of cAMP and activation of Rap2B. Rap2B may promote cell adhesion, spread, migration and polarity, in addition to integrin activation, axonal outgrowth and phagocytosis, through interacting with R-Ras effectors such as PLC-ε (76)(77)(78)(79)(80)(81)(82)(83).…”