title: Post-priming actions of ATP on Ca2+-dependent exocytosis in pancreatic beta cells.
abstract: The role of cytosolic ATP in exocytosis was investigated by using amperometric measurement of insulin exocytosis in pancreatic beta cells, which were stimulated with photolysis of caged Ca2+ compounds. Insulin exocytosis occurred with two rates. We found that ATP hastened and augmented the exocytosis via selective enhancement of the exocytosis with the faster rate. A nonhydrolysable analog of ATP, adenosine 5'-O-(3-thiotriphosphate), which blocks ATPase, was even more effective than ATP, indicating that the phosphorylation event occurred downstream of ATP-dependent vesicle transportation and priming. The action of ATP was eliminated by a competitive antagonist of cAMP, and by an inhibitor of adenylate cyclase. These data characterize an ATP sensing mechanism for the Ca2+-dependent exocytosis involving adenylate-cyclase, cAMP-dependent protein kinase, and, possibly, the fusion machinery itself. Thus, the fast exocytotic machinery requires both phosphorylation and Ca2+ for the final triggering and likely constitutes a distal ATP sensor for insulin exocytosis that acts in concert with ATP-sensitive K+ channels.
authors.affiliation: Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Kadowaki
authors.forename: Y
authors.initials: Y
authors.lastname: Yazaki
authors.forename: G C
authors.initials: GC
authors.lastname: Ellis-Davies
authors.forename: Y
authors.initials: Y
authors.lastname: Miyashita
authors.forename: H
authors.initials: H
authors.lastname: Kasai
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects*; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D010179:Pancreas / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D010782:Photolysis; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007328:Insulin; D013873:Thionucleotides; C117677:dimethoxynitrophenyl-EGTA-4; C016957:adenosine-3',5'-cyclic phosphorothioate; C022571:adenosine 5'-O-(3-thiotriphosphate); D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium