Regulation of Calcium-Permeable TRPV2 Channel by Insulin in Pancreatic β-Cells

  1. Itaru Kojima1
  1. 1Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
  2. 2Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Maebashi, Japan
  3. 3Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
  4. 4Department of Medicine, Joslin Diabetic Center, Harvard Medical School, Boston, Massachusetts
  1. Corresponding author: Itaru Kojima, ikojima{at}showa.gunma-u.ac.jp

Abstract

OBJECTIVE—Calcium-permeable cation channel TRPV2 is expressed in pancreatic β-cells. We investigated regulation and function of TRPV2 in β-cells.

RESEARCH DESIGN AND METHODS—Translocation of TRPV2 was assessed in MIN6 cells and cultured mouse β-cells by transfecting TRPV2 fused to green fluorescent protein or TRPV2 containing c-Myc tag in the extracellular domain. Calcium entry was assessed by monitoring fura-2 fluorescence.

RESULTS—In MIN6 cells, TRPV2 was observed mainly in cytoplasm in an unstimulated condition. Addition of exogenous insulin induced translocation and insertion of TRPV2 to the plasma membrane. Consistent with these observations, insulin increased calcium entry, which was inhibited by tranilast, an inhibitor of TRPV2, or by knockdown of TRPV2 using shRNA. A high concentration of glucose also induced translocation of TRPV2, which was blocked by nefedipine, diazoxide, and somatostatin, agents blocking glucose-induced insulin secretion. Knockdown of the insulin receptor attenuated insulin-induced translocation of TRPV2. Similarly, the effect of insulin on TRPV2 translocation was not observed in a β-cell line derived from islets obtained from a β-cell–specific insulin receptor knockout mouse. Knockdown of TRPV2 or addition of tranilast significantly inhibited insulin secretion induced by a high concentration of glucose. Likewise, cell growth induced by serum and glucose was inhibited by tranilast or by knockdown of TRPV2. Finally, insulin-induced translocation of TRPV2 was observed in cultured mouse β-cells, and knockdown of TRPV2 reduced insulin secretion induced by glucose.

CONCLUSIONS—TRPV2 is regulated by insulin and is involved in the autocrine action of this hormone on β-cells.

Footnotes

  • Published ahead of print at http://diabetes.diabetesjournals.org on 4 November 2008.

  • Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Received June 6, 2008.
    • Accepted October 10, 2008.
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  1. Diabetes vol. 58 no. 1 174-184
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