2-Aminoethoxydiphenyl Borate Modulates Kinetics of Intracellular Ca2+ Signals Mediated by Inositol 1,4,5-Trisphosphate-Sensitive Ca2+ Stores in Single Pancreatic Acinar Cells of Mouse

  1. Jie Wu1,1,
  2. Noritaka Kamimura1,
  3. Teruko Takeo1,
  4. Sechiko Suga1,
  5. Makoto Wakui1,
  6. Takayuki Maruyama2 and
  7. Katsuhiko Mikoshiba3
  1. 1Department of Physiology, Hirosaki University School of Medicine, Hirosaki, Japan (J.W., N.K., T.T., S.S., M.W.); 2Minase Research Institute, Ono Pharmacological Company, Osaka, Japan (T.M.); and3Department of Molecular Neurobiology, Institute of Medical Science, Tokyo University, Tokyo, Japan (K.M.)

    Abstract

    Regulation of the kinetics of intracellular Ca2+ signals with a novel, membrane-penetrable, inositol 1,4,5-trisphosphate (InsP3) receptor/Ca2+ channel modulator, 2-amino-ethoxydiphenyl borate (2APB), has been investigated using patch-clamp, whole-cell recording to monitor Ca2+-activated Cl− currents in single isolated pancreatic acinar cells. 2APB itself fails to evoke a detectable current response but it dramatically changes the kinetics of agonist-induced Ca2+release from pulsatile spikes to long-lasting, huge Ca2+waves, suggesting that 2APB coordinates local Ca2+ release to generate global Ca2+ signals. The regulation by 2APB can be elicited by internal perfusion of InsP3 in a concentration-dependent manner, indicating that this regulation is not mediated through membrane receptors or G protein signal transduction. The InsP3 receptor blocker heparin, but not the ryanodine-sensitive receptor blockers ruthenium red or ryanodine, abolishes 2APB-mediated regulation of Ca2+ release. This results also suggest that 2APB effects are mediated through InsP3 receptors. 2APB substantially modifies single inward Cl− current pulse evoked by the photolytic release of caged InsP3 but not by caged Ca2+. These data indicate that 2APB-induced regulation is mediated neither by Ca2+-induced Ca2+ release nor by affecting Cl− channel activity directly. We conclude that 2APB regulates the kinetics of intracellular Ca2+ signals, represented as the change in the Ca2+ oscillation patterns from brief pulsatile spikes to huge, long-lasting Ca2+waves. Moreover, this regulation seems to be mediated through InsP3-sensitive Ca2+ pools. 2APB may act as a novel, useful pharmacological tool to study the genesis of intracellular Ca2+ signals.

    Footnotes

    • Send reprint requests to: Jie Wu, M.D., Ph.D., Division of Neurology, Barrow Neurological Institute, St. Joseph Hospital and Medical Center, 350 West Thomas Road, Phoenix AZ 85013-4496. E-mail:jwu2{at}chw.edu

    • ↵1 Present address: Division of Neurology, Barrow Neurological Institute, St. Joseph Hospital and Medical Center, Phoenix, Arizona.

    • Abbreviations:
      InsP3
      inositol 1,4,5-trisphosphate
      IICR
      inositol 1,4,5-trisphosphate-induced Ca2+ release
      CICR
      Ca2+-induced Ca2+ release
      2APB
      2-aminoethoxydiphenyl borate
      CCK
      cholecystokinin
      Ach
      acetylcholine
      GTPγS
      guanosine-5′-O-(3-thio)triphosphate
      InsP3R
      inositol 1,4,5-trisphosphate receptor
      DTT
      dithiothreitol
      RyR
      ryanodine receptor
      DMSO
      dimethyl sulfoxide
      SH
      sulfhydryl
      • Received December 17, 1999.
      • Accepted August 9, 2000.
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    1. Molecular Pharmacology December 1, 2000 vol. 58 no. 6 1368-1374
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