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PKC-induced Sensitization of Ca2+-dependent Exocytosis Is Mediated by Reducing the Ca2+ Cooperativity in Pituitary Gonadotropes

PKC-induced Sensitization of Ca2+-dependent Exocytosis Is Mediated by Reducing the Ca2+... The highly cooperative nature of Ca 2+ -dependent exocytosis is very important for the precise regulation of transmitter release. It is not known whether the number of binding sites on the Ca 2+ sensor can be modulated or not. We have previously reported that protein kinase C (PKC) activation sensitizes the Ca 2+ sensor for exocytosis in pituitary gonadotropes. To further unravel the underlying mechanism of how the Ca 2+ sensor is modulated by protein phosphorylation, we have performed kinetic modeling of the exocytotic burst and investigated how the kinetic parameters of Ca 2+ -triggered fusion are affected by PKC activation. We propose that PKC sensitizes exocytosis by reducing the number of calcium binding sites on the Ca 2+ sensor (from three to two) without significantly altering the Ca 2+ -binding kinetics. The reduction in the number of Ca 2+ -binding steps lowers the threshold for release and up-regulates release of fusion-competent vesicles distant from Ca 2+ channels. exocytosis kinetic modeling Ca 2+ dependency fusion protein phosphorylation Footnotes H. Yang and H. Liu contributed equally to this work. Abbreviations used in this paper: DMN, DM-nitrophen; HCSP, highly Ca 2+ -sensitive pool; KS, Kolmogorov-Smirnov; NP-EGTA, nitrophenyl-EGTA. Submitted: 6 December 2004 Accepted: 18 January 2005 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of General Physiology Rockefeller University Press

PKC-induced Sensitization of Ca2+-dependent Exocytosis Is Mediated by Reducing the Ca2+ Cooperativity in Pituitary Gonadotropes

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Publisher
Rockefeller University Press
Copyright
Copyright © 2005, by The Rockefeller University Press
ISSN
0022-1295
eISSN
1540-7748
DOI
10.1085/jgp.200409230
pmid
15710914
Publisher site
See Article on Publisher Site

Abstract

The highly cooperative nature of Ca 2+ -dependent exocytosis is very important for the precise regulation of transmitter release. It is not known whether the number of binding sites on the Ca 2+ sensor can be modulated or not. We have previously reported that protein kinase C (PKC) activation sensitizes the Ca 2+ sensor for exocytosis in pituitary gonadotropes. To further unravel the underlying mechanism of how the Ca 2+ sensor is modulated by protein phosphorylation, we have performed kinetic modeling of the exocytotic burst and investigated how the kinetic parameters of Ca 2+ -triggered fusion are affected by PKC activation. We propose that PKC sensitizes exocytosis by reducing the number of calcium binding sites on the Ca 2+ sensor (from three to two) without significantly altering the Ca 2+ -binding kinetics. The reduction in the number of Ca 2+ -binding steps lowers the threshold for release and up-regulates release of fusion-competent vesicles distant from Ca 2+ channels. exocytosis kinetic modeling Ca 2+ dependency fusion protein phosphorylation Footnotes H. Yang and H. Liu contributed equally to this work. Abbreviations used in this paper: DMN, DM-nitrophen; HCSP, highly Ca 2+ -sensitive pool; KS, Kolmogorov-Smirnov; NP-EGTA, nitrophenyl-EGTA. Submitted: 6 December 2004 Accepted: 18 January 2005

Journal

The Journal of General Physiology – Rockefeller University Press

Published: Mar 1, 2005

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