HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 582/3/1087    most recent jphysiol.2007.135228v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hatakeyama, H. Articles by Kasai, H. Search for Related Content PubMed PubMed Citation Articles by Hatakeyama, H. Articles by Kasai, H. Related Collections Cellular

¹Division of Biophysics, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033 Japan ²Center for NanoBio Integration, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033 Japan ³Department of Cell Physiology, National Institute for Physiological Sciences, and Graduate University of Advanced Studies (SOKENDAI), Myodaiji, Okazaki, 444-8585 Japan ⁴Section of Information Processing, Center for Brain Experiment, National Institute for Physiological Sciences, and Graduate University of Advanced Studies (SOKENDAI), Myodaiji, Okazaki, 444-8585 Japan

It has been reported that cAMP regulates Ca²⁺-dependent exocytosis via protein kinase A (PKA) and exchange proteins directly activated by cAMP (Epac) in neurons and secretory cells. It has, however, never been clarified how regulation of Ca²⁺-dependent exocytosis by cAMP differs depending on the involvement of PKA and Epac, and depending on two types of secretory vesicles, large dense-core vesicles (LVs) and small vesicles (SVs). In this study, we have directly visualized Ca²⁺-dependent exocytosis of both LVs and SVs with two-photon imaging in mouse pancreatic -cells. We found that marked exocytosis of SVs occurred with a time constant of 0.3 s, more than three times as fast as LV exocytosis, on stimulation by photolysis of a caged-Ca²⁺ compound. The diameter of SVs was identified as 80 nm with two-photon imaging, which was confirmed by electron-microscopic investigation with photoconversion of diaminobenzidine. Calcium-dependent exocytosis of SVs was potentiated by the cAMP-elevating agent forskolin, and the potentiating effect was unaffected by antagonists of PKA and was mimicked by the Epac-selective agonist 8-(4-chlorophenylthio)-2'-O-methyl cAMP, unlike that on LVs. Moreover, high-glucose stimulation induced massive exocytosis of SVs in addition to LVs, and photolysis of caged cAMP during glucose stimulation caused potentiation of exocytosis with little delay for SVs but with a latency of 5 s for LVs. Thus, Epac and PKA selectively regulate exocytosis of SVs and LVs, respectively, in -cells, and Epac can regulate exocytosis more rapidly than PKA.

(Received 23 April 2007; accepted after revision 15 May 2007; first published online 17 May 2007)
Corresponding author H. Kasai: Division of Biophysics, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033 Japan. Email: hkasai{at}m.u-tokyo.ac.jp

This article has been cited by other articles:

				G. Kang, C. A. Leech, O. G. Chepurny, W. A. Coetzee, and G. G. Holz Role of the cAMP sensor Epac as a determinant of KATP channel ATP sensitivity in human pancreatic {beta}-cells and rat INS-1 cells J. Physiol., March 1, 2008; 586(5): 1307 - 1319. [Abstract] [Full Text] [PDF]