Acetylcholine-induced phosphorylation of CPI-17 in rat bronchial smooth muscle: the roles of Rho-kinase and protein kinase C

Can J Physiol Pharmacol. 2005 Apr;83(4):375-81. doi: 10.1139/y05-022.


It has been demonstrated that CPI-17 provokes an inhibition of myosin light chain phosphatase to increase myosin light chain phosphorylaton and Ca(2+) sensitivity during contraction of vascular smooth muscle. However, expression and agonist-mediated regulation of CPI-17 in bronchial smooth muscle have not been documented. Thus, expression and phosphorylation of CPI-17 mediated by PKC and ROCK were investigated using rat bronchial preparations. Acetylcholine (ACh)-induced contraction and Ca(2+) sensitization were both attenuated by 10(-6) mol Y-27632 /L, a ROCK inhibitor, 10(-6) mol calphostin C/L, a PKC inhibitor, and their combination. A PKC activator, PDBu, induced a Ca(2+) sensitization in alpha-toxin-permeabilized bronchial smooth muscle. In this case, the Ca(2+) sensitizing effect was significantly inhibited by caphostin C but not by Y-27632. An immunoblot study demonstrated CPI-17 expression in the rat bronchial smooth muscle. Acetylcholine induced a phosphorylation of CPI-17 in a concentration-dependent manner, which was significantly inhibited by Y-27632 and calphostin C. In conclusion, these data suggest that both PKC and ROCK are involved in force development, Ca(2+) sensitization, and CPI-17 phosphorylation induced by ACh stimulation in rat bronchial smooth muscle. As such, RhoA/ROCK, PKC/CPI-17, and RhoA/ROCK/CPI pathways may play important roles in the ACh-induced Ca(2+) sensitization of bronchial smooth muscle contraction.

MeSH terms

  • Acetylcholine / pharmacology*
  • Animals
  • Bronchi / drug effects*
  • Enzyme Inhibitors / pharmacology
  • In Vitro Techniques
  • Intracellular Signaling Peptides and Proteins
  • Male
  • Muscle Proteins / pharmacology*
  • Muscle, Smooth / drug effects*
  • Myosin Light Chains / metabolism
  • Naphthalenes / pharmacology
  • Phorbol 12,13-Dibutyrate / pharmacology
  • Phosphoproteins / pharmacology*
  • Phosphorylation
  • Protein Kinase C / physiology*
  • Protein Serine-Threonine Kinases / metabolism
  • Protein Serine-Threonine Kinases / physiology*
  • Rats
  • Rats, Wistar
  • Type C Phospholipases / pharmacology
  • Vasodilator Agents / pharmacology*
  • rho-Associated Kinases


  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Muscle Proteins
  • Myosin Light Chains
  • Naphthalenes
  • Phosphoproteins
  • Ppp1r14a protein, rat
  • Vasodilator Agents
  • Phorbol 12,13-Dibutyrate
  • Protein Serine-Threonine Kinases
  • rho-Associated Kinases
  • Protein Kinase C
  • Type C Phospholipases
  • calphostin C
  • Acetylcholine