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Science 297 (5585): 1349-1352

Copyright © 2002 by the American Association for the Advancement of Science

Fusion Pore Dynamics and Insulin Granule Exocytosis in the Pancreatic Islet

Noriko Takahashi,1 Takuya Kishimoto,1 Tomomi Nemoto,1 Takashi Kadowaki,2 Haruo Kasai1*

Insulin secretion from intact mouse pancreatic islets was investigated with two-photon excitation imaging. Insulin granule exocytosis occurred mainly toward the interstitial space, away from blood vessels. The fusion pore was unusually stable with a lifetime of 1.8 seconds. Opening of the 1.4-nanometer-diameter pore was preceded by unrestricted lateral diffusion of lipids along the inner wall of the pore, supporting the idea that this structure is composed of membrane lipids. When the pore dilated to 12 nanometers, the granules rapidly flattened and discharged their contents. Thus, our methodology reveals fusion pore dynamics in intact tissues at nanometer resolution.

1 Department of Cell Physiology, National Institute for Physiological Sciences, and the Graduate University of Advanced Studies, Myodaiji, Okazaki 444-8585, Japan.
2 Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
*   To whom correspondence should be addressed. E-mail: hkasai{at}

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