Heterotrimeric G protein Gαs subunit attenuates PLEKHG2, a Rho family-specific guanine nucleotide exchange factor, by direct interaction

PLEKHG2 is a G beta gamma-dependent guanine nucleotide exchange factor (GEF) for the small GTPases Rac and Cdc42, and has been shown to mediate signalling pathways such as actin cytoskeleton reorganization and serum response element (SRE)-dependent gene transcription. Here we show that the constitutively active mutant of the G alpha s subunit significantly attenuated PLEKHG2-induced SRE-mediated gene transcription. Strikingly, we observed that the constitutive activation of endogenous G alpha s by treatment with CTx caused a similar inhibitory effect on PLEKHG2-induced activation of SRE. However, both the enforced expression of the catalytic subunit beta, of protein kinase A and the treatment with dibutyl-cyclic AMP failed to mimic the inhibitory effect of G alpha s on PLEKHG2. Furthermore, the dominant negative mutant of protein kinase A had no effect on PLEKHG2-mediated SRE activation. Performing immunoprecipitation and an in vitro pulldown assay, we found that PLEKHG2 directly interacted with the active form of the G alpha s subunit in cells. The interaction between PLEKHG2 and G alpha s required the N-terminal region of PLEKHG2, which includes the DH domain, a functional domain of GEF, suggesting that G alpha s directly masks the DH domain of PLEKHG2. In a previous study, we reported that G beta gamma accelerates PLEKHG2-mediated SRE-dependent gene transcription. Interestingly, G alpha s also inhibited the hyperactivation of SRE induced by the co-expression of G beta gamma and PLEKHG2; however, G alpha s and G beta gamma bind to different regions of PLEKHG2. This is the first report to show that PLEKHG2 is a novel effector of G alpha s, and is negatively regulated by the G alpha s subunit through direct interaction. (C) 2017 Elsevier Inc. All rights reserved.