Post-priming actions of ATP on Ca2+-dependent exocytosis in pancreatic beta cells
- Noriko Takahashi*,
- Takashi Kadowaki*,
- Yoshio Yazaki*,
- Graham C. R. Ellis-Davies†,
- Yasushi Miyashita‡, and
- Haruo Kasai‡,§
- ‡Department of Physiology and *Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan; and †Department of Physiology, MCP Hahnemann University, Philadelphia, Pennsylvania 19129
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Communicated by Erwin Neher, Max Planck Institute of Biophysical Chemistry, Goettingen, Germany (received for review August 25, 1998)
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.
Footnotes
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↵ § To whom reprint requests should be addressed: e-mail: hkasai{at}m.u-tokyo.ac.jp.
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A Commentary on this article begins on page 329.
- ABBREVIATIONS:
- Rp-cAMP,
- adenosine 3′,5′-monophosphothioate;
- ATP[γS],
- adenosine 5′-O-(3-thiotriphosphate);
- AMP-PNP,
- 5′-adenylyl-β,γ-imidodiphosphate;
- LV,
- large dense-core vesicle;
- PKA,
- protein kinase A;
- MDL-12,
- 330A, cis-N-(as-2-phenylcyclopentyl)azacyclo-tridecan-2-imine hydrochloride;
- DMNPE-4,
- dimethoxynitrophenyl-EGTA-4
- Copyright © 1999, The National Academy of Sciences
