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Rho-kinase-mediated regulation of receptor-agonist-stimulated smooth muscle contraction

Ming-Ho Tsai1, Meei Jyh Jiang

  • 1Institute of Basic Medical Sciences, National Cheng-Kung University College of Medicine, Tainan, Taiwan.

Pflugers Archiv : European Journal of Physiology
|September 6, 2006
PubMed

Insights

Rho kinase regulates smooth muscle contraction by phosphorylating MYPT1 at Thr855, impacting myosin phosphatase activity. This mechanism is crucial for force generation and actin polymerization in rat tail artery smooth muscle.

Area of Science:

  • Physiology
  • Biochemistry
  • Pharmacology

Background:

  • Rho kinase plays a role in smooth muscle contraction by modulating myosin phosphatase (MLCP) activity.
  • The precise in vivo mechanism of Rho kinase in regulating MLCP activity requires further clarification.

Purpose of the Study:

  • To investigate the in vivo effects of Rho kinase inhibition on MLCP subunit MYPT1 and CPI-17 phosphorylation.
  • To examine the role of Rho kinase in actin polymerization during rat tail artery (RTA) smooth muscle contraction.

Main Methods:

  • Used Rho kinase inhibitor Y27632 to study RTA smooth muscle contraction.
  • Measured phosphorylation of MYPT1 (Thr697, Thr855) and CPI-17 (Thr38).
  • Assessed actin polymerization and MLC(20) phosphorylation.

Main Results:

  • Y27632 suppressed phenylephrine- and U46619-induced force and MLC(20) phosphorylation.
  • Phenylephrine and U46619 increased MYPT1(Thr855) phosphorylation, abolished by Y27632.
  • Rho kinase inhibition reduced actin polymerization under phenylephrine but not U46619 stimulation.

Conclusions:

  • Rho kinase regulates MLCP activity via MYPT1(Thr855) phosphorylation during RTA smooth muscle contraction.
  • Rho kinase is essential for alpha(1)-adrenoceptor-mediated actin polymerization, with a lesser role in thromboxane receptor stimulation.

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