Rho-kinase-mediated regulation of receptor-agonist-stimulated smooth muscle contraction.
Rho kinase was shown to regulate smooth muscle contraction through modulating myosin phosphatase (MLCP) activity, but the in vivo mechanism remains to be clarified. This study examined the effects of Rho kinase inhibition on the phosphorylation time course of MLCP subunit MYPT1 at Thr697 and Thr855 and MLCP inhibitory protein CPI-17 at Thr38 and on actin polymerization during the contraction of rat tail artery (RTA) smooth muscle. Rho kinase inhibitor Y27632 suppressed force activated by alpha(1)-adrenergic agonist phenylephrine or thromboxane A(2) analog U46619 with concomitant decreases in MLC(20) phosphorylation. Phenylephrine and U46619 significantly increased MYPT1(Thr855) phosphorylation that was eliminated by Y27632 pretreatment, whereas MYPT1(Thr697) phosphorylation was not stimulated. Phenylephrine increased CPI-17(Thr38) phosphorylation that was not inhibited by Y27632 but was abolished by a protein kinase C inhibitor Ro 31-8220; in contrast, U46619 did not stimulate CPI-17 phosphorylation. Both agonists increased actin polymerization that was diminished by Y27632 under phenylephrine but not U46619 activation. These results demonstrated a temporal correlation between MYPT1(Thr855) phosphorylation, MLC(20) phosphorylation, and contraction in a Rho-kinase-dependent manner for both phenylephrine and U46619 stimulation, suggesting that Rho kinase regulates MLCP activity through MYPT1(Thr855) phosphorylation during RTA smooth muscle contraction. Furthermore, Rho kinase regulates actin polymerization activated by alpha(1)-adrenoceptors but is less significant in thromboxane receptor stimulation.
Tsai
Ming-Ho
MH
Institute of Basic Medical Sciences, National Cheng-Kung University College of Medicine, Tainan, Taiwan.
Jiang
Meei Jyh
MJ
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000199:Actins / Q000378:metabolism; D000577:Amides; D000818:Animals; D001158:Arteries / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism*; D010656:Phenylephrine; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines; D051381:Rats; D017207:Rats, Sprague-Dawley; D013912:Threonine / Q000378:metabolism; D014662:Vasoconstrictor Agents; D054460:rho-Associated Kinases
D000199:Actins; D000577:Amides; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D018994:Myosin Light Chains; D010750:Phosphoproteins; C491519:Ppp1r14a protein, rat; D011725:Pyridines; D014662:Vasoconstrictor Agents; C108830:Y 27632; D010656:Phenylephrine; D013912:Threonine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D010749:Phosphoprotein Phosphatases; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1