PDZ-RhoGEF and LARG are essential for embryonic development and provide a link between thrombin and LPA receptors and Rho activation

G protein-coupled receptors (GPCRs) linked to both members of the Gα₁₂ family of heterotrimeric G proteins α subunits, Gα₁₂ and Gα₁₃, regulate the activation of Rho GTPases, thereby contributing to many key biological processes. Multiple Rho GEFs have been proposed to link Gα_12/13 GPCRs to Rho activation, including PDZ-RhoGEF (PRG), leukemia-associated Rho GEF (LARG), p115-RhoGEF (p115), lymphoid blast crisis (Lbc), and Dbl. PRG, LARG, and p115 share the presence of aregulator of G protein signaling homology (RGS) domain. There is limited information on the biological roles of this RGS-containing family of RhoGEFs in vivo. p115-deficient mice are viable with some defects in the immune system and gastrointestinal motor dysfunctions, whereas in an initial study we showed that mice deficient for Larg are viable and resistant to salt-induced hypertension. Here, we generated knock-out mice for Prg and observed that these mice do not display any overt phenotype. However, deficiency in Prg and Larg leads to complex developmental defects and early embryonic lethality. Signaling from Gα_11/q linked GPCRs to Rho was not impaired in mouse embryonic fibroblasts defective in all three RGS-containing RhoGEFs. However, a combined lack of Prg, Larg, and p115 expression abolished signaling through Gα_12/13 to Rho and thrombin-induced cell proliferation, directional migration, and nuclear signaling through JNK and p38. These findings provide evidence of an essential role for the RGS-containing RhoGEF family in signaling to Rho by Gα_12/13-coupled GPCRs, which may likely play a critical role during embryonic development.