Ca2+/calmodulin and cyclic 3,5' adenosine monophosphate control movement of secretory granules through protein phosphorylation/dephosphorylation in the pancreatic beta-cell.
We observed the movement of insulin granules in living transformed hamster pancreatic beta-cells (HIT T15) with a light microscope, where secretory granules are moving in the cytoplasmic space. Velocity of the typical granule movement was approximately 1.5 microns/sec. A stimulatory concentration of glucose activated the movement of the secretory granules. Forskolin, an activator of adenylate cyclase, increased the movement, resulting in changes in intracellular localization of the granules. Acetylcholine also activated the granule movement, whereas high K+ and tolbutamide, which cause Ca2+ influx through the voltage-dependent Ca2+ channel, had only little effect. The movement was abolished by BAPTA, the intracellular Ca2+-chelator. Activation of protein kinase C by 12-O-tetradecanoyl-phorbol 13-acetate failed to affect this movement. The motile events were inhibited by the calmodulin antagonist, W-7, and dramatically increased by okadaic acid, an inhibitor of protein phosphatases 1 and 2A. These results suggest protein phosphorylation by Ca2+/calmodulin- and cAMP-dependent protein kinases play a positive role in the control of the insulin granule movements, which results in potentiation of insulin release from the pancreatic beta-cell.
Second Department of Internal Medicine, Nagoya University School of Medicine, Japan.
M
M
Hisatomi
H
H
Hidaka
I
I
Niki
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D007700:Kinetics; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology
D002147:Calmodulin; D002614:Chelating Agents; D007328:Insulin; D010750:Phosphoproteins; D013449:Sulfonamides; D005576:Colforsin; D019319:Okadaic Acid; D004533:Egtazic Acid; C017967:W 7; D014044:Tolbutamide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D005947:Glucose; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000109:Acetylcholine; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium; D002118:Calcium