Conclusion
We demonstrate that p63RhoGEF selectively couples Gα(q/11) but not Gα(12/13), to RhoA activation in blood vessels and cultured cells and thus mediates the physiologically important Ca2+ sensitization of force induced with Gα(q/11)-coupled agonists. Our results suggest that signaling through p63RhoGEF provides a novel mechanism for selective regulation of blood pressure.
Objective
We examine whether p63RhoGEF, known to couple specifically to Gα(q/11) in vitro, is functional in blood vessels as a mediator of RhoA activation and if it is selectively activated by Gα(q/11) coupled agonists.
Results
We find that p63RhoGEF is present across SM tissues and demonstrate that silencing of the endogenous p63RhoGEF in mouse portal vein inhibits contractile force induced by endothelin-1 to a greater extent than the predominantly Gα(12/13)-mediated thromboxane analog U46619. This is because endothelin-1 acts on Gα(q/11) as well as Gα(12/13). Introduction of the exogenous isolated pleckstrin-homology (PH) domain of p63RhoGEF (residues 331-580) into permeabilized rabbit portal vein inhibited Ca2+ sensitized force and activation of RhoA, when phenylephrine was used as an agonist. This reinforces the results based on endothelin-1, because phenylephrine is thought to act exclusively through Gα(q/11).