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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / analogs & derivatives
-
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / pharmacology
-
Animals
-
Antibodies, Monoclonal / pharmacology
-
Azepines / pharmacology
-
Bacterial Proteins
-
Calcium / pharmacology*
-
Calcium-Calmodulin-Dependent Protein Kinase Type 2
-
Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
-
Cell Membrane Permeability
-
Cells, Cultured
-
Enzyme Inhibitors / pharmacology
-
Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
-
Homeostasis
-
Insulin / metabolism*
-
Insulin Secretion
-
Islets of Langerhans / drug effects
-
Islets of Langerhans / metabolism
-
Islets of Langerhans / physiology*
-
Kinetics
-
Male
-
Myosin Heavy Chains / metabolism
-
Myosin Light Chains / metabolism*
-
Myosin-Light-Chain Kinase / immunology
-
Myosin-Light-Chain Kinase / metabolism*
-
Phosphorylation
-
Rats
-
Rats, Wistar
-
Streptolysins
Substances
-
Antibodies, Monoclonal
-
Azepines
-
Bacterial Proteins
-
Enzyme Inhibitors
-
Insulin
-
Myosin Light Chains
-
Streptolysins
-
streptolysin O
-
ML 9
-
Guanosine 5'-O-(3-Thiotriphosphate)
-
KN 62
-
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
-
Calcium-Calmodulin-Dependent Protein Kinase Type 2
-
Calcium-Calmodulin-Dependent Protein Kinases
-
Myosin-Light-Chain Kinase
-
Myosin Heavy Chains
-
Calcium