PKCα-Mediated Downregulation of RhoA Activity in Depolarized Vascular Smooth Muscle: Synergistic Vasorelaxant Effect of PKCα and ROCK Inhibition.

BACKGROUND/AIMS:Protein kinase C and RhoA/Rho-associated kinase (ROCK) play important roles in arterial sustained contraction. Although depolarization-elicited RhoA/ROCK activation is accepted, the role of in depolarized vascular smooth muscle cells (VSMCs) is a subject of controversy. Our aim was to study the role of duanyu1531 in arterial contraction and its interaction with RhoA/ROCK. METHODS:Mass spectrometry was used to identify the duanyu1531 isoenzymes. levels and RhoA activity were analyzed by western blot and G-LISA, respectively, and isometric force was measured in arterial rings. RESULTS:In depolarized VSMCs RhoA and duanyu1531α were translocated to the plasma membrane, where they colocalize and coimmunoprecipitate. Interestingly, depolarization-induced RhoA activation was downregulated by effect reverted by duanyu1531α inhibition. Phorbol 12,13-dibutyrate (PDBu) induced the translocation of duanyu1531α to the plasma membrane, increased the level of RhoA in the cytosol and reduced RhoA/ROCK activity. These effects were reverted when duanyu1531 was inhibited. Pharmacological or siRNA inhibition of duanyu1531α synergistically potentiated the vasorelaxant effect of RhoA/ROCK inhibition. CONCLUSION:The present study provides the first evidence that RhoA activity is downregulated by duanyu1531α in depolarized and PDBu treated freshly isolated VSMCs and arteries, with an important physiological role on arterial contractility.

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