P2Y(1), P2Y(2), P2Y(4), and P2Y(6) receptors are coupled to Rho and Rho kinase activation in vascular myocytes

In the cardiovascular system, activation of ionotropic (P2X receptors) and metabotropic (P2Y receptors) P2 nucleotide receptors exerts potent and vari ous responses including vasodilation, vasoconstriction, and vascular smooth muscle cell proliferation. Here we examined the involvement of the small G TPase RhoA in P2Y receptor-mediated effects in vascular myocytes. Stimulati on of cultured aortic myocytes with P2Y receptor agonists induced an increa se in the amount of membrane-bound RhoA and stimulated actin cytoskeleton o rganization. P2Y receptor agonist-induced actin stress fiber formation was inhibited by C3 exoenzyme and the Rho kinase inhibitor Y-27632. Stimulation of actin cytoskeleton organization by extracellular nucleotides was also a bolished in aortic myocytes expressing a dominant negative form of RhoA. Ex tracellular nucleotides induced contraction and Y-27632-sensitive Ca2+ sens itization in aortic rings. Transfection of Swiss 3T3 cells with P2Y recepto rs showed that Rho kinase-dependent actin stress fiber organization was ind uced in cells expressing P2Y(1), P2Y(2), P2Y(4), or P2Y(6) receptor subtype s. Our data demonstrate that P2Y(1), P2Y(2), P2Y(4), and P2Y(6) receptor su btypes are coupled to activation of RhoA and subsequently to Rho-dependent signaling pathways.