G{beta}{gamma} signaling to the chemotactic effector P-REX1 and mammalian cell migration is directly regulated by G{alpha}q and G{alpha}13 proteins [Cell Biology] (Journal of Biological Chemistry)

G protein-coupled receptors stimulate Rho guanine nucleotide exchange factors that promote mammalian cell migration. Rac and Rho GTPases exert opposing effects on cell morphology and are stimulated downstream of G?? and G?12/13 or G?q, respectively. These G? subunits might in turn favor Rho pathways by preventing G?? signaling to Rac. Here, we investigated whether G?? signaling to phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-REX1), a key G?? chemotactic effector, is directly controlled by Rho-activating G? subunits. We show that pharmacological inhibition of G?q makes P-REX1 activation by Gq/Gi-coupled lysophosphatidic acid receptors more effective. Moreover, chemogenetic control of Gi and Gq by designer receptors exclusively activated by designer drugs (DREADDs) confirmed that Gi differentially activates P-REX1. GTPase-deficient G?qQL and G?13QL variants formed stable complexes with G??, impairing its interaction with P-REX1. The N-terminal regions of these variants were essential for stable interaction with G??. Pulldown assays revealed that chimeric G?13-i2QL interacts with G?? unlike to G?i2-13QL, the reciprocal chimera, which similarly to G?i2QL could not interact with G??. Moreover, G?? was part of tetrameric G??-G?qQL-RGS2 and G??-G?13-i2QL-RGS4 complexes, whereas G?13QL dissociated from G?? to interact with the PDZ-RhoGEF-RGS domain. Consistent with an integrated response, G?? and AKT kinase were associated with active SDF-1/CXCL12-stimulated P-REX1. This pathway was inhibited by G?qQL and G?13QL, which also prevented CXCR4-dependent cell migration. We conclude that a coordinated mechanism prioritizes G?q- and G?13-mediated signaling to Rho over a G??-dependent Rac pathway, attributed to heterotrimeric Gi proteins.