title: Myosin light-chain phosphorylation controls insulin secretion at a proximal step in the secretory cascade.
abstract: The aim of this study was to investigate how insulin secretion is controlled by phosphorylation of the myosin light chain (MLC). Ca2+-evoked insulin release from pancreatic islets permeabilized with streptolysin O was inhibited by different monoclonal antibodies against myosin light-chain kinase (MLCK) to an extent parallel to their inhibition of purified MLCK. Anti-MLCK antibody also inhibited insulin release caused by the stable GTP analog guanosine 5'-O-(3-thiodiphosphate), even at a substimulatory concentration (0.1 microM) of Ca2+. Free Ca2+ increased MLC peptide phosphorylation by beta-cell extracts in vitro. In contrast to the phosphorylation by purified MLCK or by calmodulin (CaM) kinase II, the activity partially remained with the beta-cell under nonstimulatory Ca2+ (0.1 microM) conditions. The MLCK inhibitor ML-9 inhibited the activity in the beta-cell with both substimulatory and stimulatory Ca2+, whereas KN-62, an inhibitor of CaM kinase II, only exerted an influence in the latter case. ML-9 decreased intracellular granule movement in MIN6 cells under basal and acetylcholine-stimulated conditions. We propose that MLC phosphorylation may modulate translocation of secretory granules, resulting in enhanced insulin secretion.
authors.affiliation: Department of Pharmacology, Nagoya University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Iida
authors.forename: T
authors.initials: T
authors.lastname: Senda
authors.forename: Y
authors.initials: Y
authors.lastname: Matsukawa
authors.forename: K
authors.initials: K
authors.lastname: Onoda
authors.forename: J I
authors.initials: JI
authors.lastname: Miyazaki
authors.forename: H
authors.initials: H
authors.lastname: Sakaguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Nimura
authors.forename: H
authors.initials: H
authors.lastname: Hidaka
authors.forename: I
authors.initials: I
authors.lastname: Niki
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001381:Azepines / Q000494:pharmacology; D001426:Bacterial Proteins; D002118:Calcium / Q000494:pharmacology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006706:Homeostasis; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007700:Kinetics; D008297:Male; D018995:Myosin Heavy Chains / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D013301:Streptolysins
chemical_list: D000911:Antibodies, Monoclonal; D001381:Azepines; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D007328:Insulin; D018994:Myosin Light Chains; D013301:Streptolysins; C025964:streptolysin O; C056218:ML 9; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; D018995:Myosin Heavy Chains; D002118:Calcium