title: RhoA-Rho kinase pathway mediates thrombin- and U-46619-induced phosphorylation of a myosin phosphatase inhibitor, CPI-17, in vascular smooth muscle cells.
abstract: Protein kinase C-potentiated phosphatase inhibitor of 17 kDa (CPI-17) mediates some agonist-induced smooth muscle contraction by suppressing the myosin phosphatase in a phosphorylation-dependent manner. The physiologically relevant kinases that phosphorylate CPI-17 remain to be identified. Several previous studies have shown that some agonist-induced CPI-17 phosphorylation in smooth muscle tissues was attenuated by the Rho kinase (ROCK) inhibitor Y-27632, suggesting that ROCK is involved in agonist-induced CPI-17 phosphorylation. However, Y-27632 has recently been found to inhibit protein kinase C (PKC)-delta, a well-recognized CPI-17 kinase. Thus the role of ROCK in agonist-induced CPI-17 phosphorylation remains uncertain. The present study was designed to address this important issue. We selectively activated the RhoA pathway using inducible adenovirus-mediated expression of a constitutively active mutant RhoA (V14RhoA) in primary cultured rabbit aortic vascular smooth muscle cells (VSMCs). V14RhoA caused expression level-dependent CPI-17 phosphorylation at Thr38 as well as myosin phosphatase phosphorylation at Thr853. Importantly, we have shown that V14RhoA-induced CPI-17 phosphorylation was not affected by the PKC inhibitor GF109203X but was abolished by Y-27632, suggesting that ROCK but not PKC was involved. Furthermore, we have shown that the contractile agonists thrombin and U-46619 induced CPI-17 phosphorylation in VSMCs. Similarly to V14RhoA-induced CPI-17 phosphorylation, thrombin-induced CPI-17 phosphorylation was not affected by inhibition of PKC with GF109203X, but it was blocked by inhibition of RhoA with adenovirus-mediated expression of exoenzyme C3 as well as by Y-27632. Taken together, our present data provide the first clear evidence indicating that ROCK is responsible for thrombin- and U-46619-induced CPI-17 phosphorylation in primary cultured VSMCs.
authors.affiliation: Department of Physiology and Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Huan
authors.initials: H
authors.lastname: Pang
authors.forename: Zhenheng
authors.initials: Z
authors.lastname: Guo
authors.forename: Wen
authors.initials: W
authors.lastname: Su
authors.forename: Zhongwen
authors.initials: Z
authors.lastname: Xie
authors.forename: Masumi
authors.initials: M
authors.lastname: Eto
authors.forename: Ming C
authors.initials: MC
authors.lastname: Gong
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000378:metabolism; D015151:Immunoblotting; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009124:Muscle Proteins / Q000187:drug effects / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology; D013917:Thrombin / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D008301:Maleimides; D009124:Muscle Proteins; D010750:Phosphoproteins; D011725:Pyridines; D014662:Vasoconstrictor Agents; C108830:Y 27632; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D043263:Myosin-Light-Chain Phosphatase; D013917:Thrombin; D020742:rhoA GTP-Binding Protein; C070515:bisindolylmaleimide I