Role of calmodulin and myosin light chain kinase in the activation of carbachol-activated cationic current in murine ileal myocytes.
We investigated the effect of calmodulin (CaM) and myosin light chain kinase (MLCK) on murine ileal myocytes using the whole-cell patch-clamp technique. Under the voltage clamp, at the holding potential of -60 mV, 50 micromol/L carbachol (CCh) induced inward currents (I CCh), and spontaneous decay of I CCh occurred. The peak inward currents induced by the repetitive application of CCh (50 micromol/L) tended to decrease in amplitude. Intracellular application of 0.2 mmol/L guanosine 5'-O-(gamma-thio)triphosphate (GTP gammaS) from the patch electrode induced an inward current at a holding potential of -60m V, and the peak inward currents induced by the repetitive application of Cs tended to decrease slightly in amplitude. The amplitude of I CCh was reduced by pretreatment either with W-7, trifluoroperazine, W-5, and melittin (CaM inhibitors) or with ML-7 and ML-9 (selective MLCK inhibitors), and the inhibitory effects were reversible. However, when we pretreated with 50 micromol/L W-7 or 5 micromol/L ML-7 on GTP gammaS-induced inward currents, almost no inhibition was observed in the inward currents. Application of both Rho kinase inhibitor and MLCK inhibitor inhibited GTP gammaS-induced currents. We conclude that CaM and MLCK modulate the activation process of I CCh in murine ileal myocytes and suggest that the classical type transient receptor potential (TRPC) channel 5 might be a candidate for nonselective cationic currents (NSCC) activated by muscarinic stimulation in gastrointestinal smooth muscle cells.
Kim
Byung Joo
BJ
Center for Bio-Artificial Muscle and Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
Jeon
Ju-Hong
JH
Kim
Seon Jeong
SJ
So
Insuk
I
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007082:Ileum / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000502:physiology*; D009281:Naphthalenes / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D050052:TRPC Cation Channels / Q000502:physiology
D001381:Azepines; D002147:Calmodulin; D009281:Naphthalenes; D013449:Sulfonamides; D050052:TRPC Cation Channels; C112021:Trpc5 protein, mouse; C070571:ML 7; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C017967:W 7; D002217:Carbachol; D009219:Myosin-Light-Chain Kinase