Involvement of annexin-I in glucose-induced insulin secretion in rat pancreatic islets

Makoto Ohnishi, Masaaki Tokuda, Tsutomu Masaki, Takashi Fujimura, Yuji Tai, Toshifumi Itano, Hideki Matsui, Osamu Hatase, Jiro Takahara

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Abstract

Annexin-I was demonstrated to specifically present in islets and not in exocrine tissues of the rat pancreas and to have a diffuse and homogeneous distribution in all islet cells in our previous study. In the present report, to clarify the functions of annexin-I in rat pancreatic islets, especially in β-cells, we investigated the role of annexin-I in insulin secretion. Immunoelectron microscopic analysis of pancreatic β-cells demonstrated that immunogold particles reactive to annexin-I were almost exclusively observed on most of the insulin-containing granules (∼ 90%) and less frequently located in cytosol and other organelles, such as the endoplasmic reticulum and mitochondria. The number of annexin-I gold particles located on insulin granules after oral glucose administration was significantly increased compared with that observed in fasted rats. Moreover, when the isolated islets were stimulated by a high concentration of glucose (20 mM), the phosphorylation of annexin-I was markedly enhanced, and it was synchronized to insulin secretion. This phosphorylation mainly occurred on serine residues. H-7 (100 μM), a potent inhibitor of protein kinase-C, inhibited the phosphorylation to about 90%. These findings suggest that annexin-I might be involved in the regulatory mechanism of glucose-induced insulin secretion in rat pancreatic islets via phosphorylation-dephosphorylation processes.

Original languageEnglish
Pages (from-to)2421-2426
Number of pages6
JournalEndocrinology
Volume136
Issue number6
DOIs
Publication statusPublished - Jun 1995

ASJC Scopus subject areas

  • Endocrinology

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    Ohnishi, M., Tokuda, M., Masaki, T., Fujimura, T., Tai, Y., Itano, T., Matsui, H., Hatase, O., & Takahara, J. (1995). Involvement of annexin-I in glucose-induced insulin secretion in rat pancreatic islets. Endocrinology, 136(6), 2421-2426. https://doi.org/10.1210/endo.136.6.7750463