title: Evidence for myosin light chain kinase mediating noradrenaline-evoked cation current in rabbit portal vein myocytes.
abstract: The role of myosin light chain kinase (MLCK) in the activation of the noradrenaline-evoked non-selective cation current (Icat) was examined with the whole-cell recording technique in single rabbit portal vein smooth muscle cells. Intracellular dialysis with 5 microM MLCK(11-19)amide, a substrate-specific peptide inhibitor of MLCK, markedly reduced the amplitude and rate of activation of noradrenaline-evoked Icat. A similar result was obtained when the cells were dialysed with 10 microM AV25, which also inhibits MLCK by an action at the auto-inhibitory domain of MLCK. Inhibitors of binding of ATP to MLCK, wortmannin and synthetic naphthalenesulphonyl derivatives (ML-7 and ML-9), at micromolar concentrations, also reduced the amplitude of noradrenaline-evoked Icat. ML-7 and ML-9 (both at 5 microM) reduced the amplitude of Icat induced by both guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) and 1-oleoyl-2-acetyl-sn-glycerol (OAG). MLCK(11-19)amide, AV25 and ML-9 did not inhibit the noradrenaline-evoked Ca2+-activated potassium current at a holding potential of 0 mV. In addition, MLCK(11-19)amide and AV25 did not reduce the non-selective cation current induced by ATP in rabbit ear artery cells. Intracellular dialysis with 2 microM Ca2+ and 9 microM calmodulin activated Icat, which developed over a period of about 5 min. Intracellular dialysis with the non-hydrolysable analogue of ATP, 5'-adenylylimidodiphosphate (AMP-PNP), reduced the amplitude and rate of activation of noradrenaline-evoked Icat. The results indicate that MLCK mediates noradrenaline-activated Icat in rabbit portal vein smooth muscle cells.
authors.affiliation: Department of Pharmacology and Clinical Pharmacology, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: A S
authors.initials: AS
authors.lastname: Aromolaran
authors.forename: A P
authors.initials: AP
authors.lastname: Albert
authors.forename: W A
authors.initials: WA
authors.lastname: Large
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation; D011169:Portal Vein / Q000187:drug effects / Q000201:enzymology*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002147:Calmodulin; D002412:Cations; D004075:Diglycerides; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D015221:Potassium Channels; D014662:Vasoconstrictor Agents; D000266:Adenylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C038237:1-oleoyl-2-acetylglycerol; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D000077191:Wortmannin