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Regulation of the Ca 2+ Sensitivity of Exocytosis by Rab3a
Author(s) -
Johannes Ludger,
Lledo PierreMarie,
Chameau Pascal,
Vincent JeanDidier,
Henry JeanPierre,
Darchen François
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.71031127.x
Subject(s) - exocytosis , chromaffin cell , depolarization , microbiology and biotechnology , stimulation , biology , microinjection , secretory vesicle , gtp' , patch clamp , chemistry , medicine , biophysics , endocrinology , adrenal medulla , catecholamine , secretion , biochemistry , neuroscience , electrophysiology , enzyme
Ca 2+ ions trigger the release of hormones and neurotransmitters and contribute to making the secretory vesicles competent for fusion. Here, we present evidence for the involvement of the GTP‐binding protein Rab3a in the sensitivity of the exocytotic process to internal [Ca 2+ ]. The secretory activity of bovine adrenal chromaffin cells was elicited by Ca 2+ dialysis through a patch‐clamp pipette and assayed by monitoring changes in cell membrane capacitance. Microinjection of antisense oligonucleotides directed to rab3a mRNA increased the secretory activity observed at low (0.2–4 µ M ) [Ca 2+ ], but did not change the maximal activity observed at 10 µ M free [Ca 2+ ]. Moreover, after a train of depolarizing stimuli, the secretory activity of antisense‐injected cells dialyzed with 10 µ M [Ca 2+ ] was increased significantly compared with that of control cells. This result suggests that the activity of either Rab3a or its partners might change upon stimulation. We conclude that Rab3a, together with its partners, participates in the Ca 2+ dependence of exocytosis and that its activity is modulated further in a stimulus‐dependent manner. These findings should provide some clues to elucidate the role of Rab3a in synaptic plasticity.