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Asynchronous Ca2+ current conducted by voltage-gated Ca2+ (CaV)-2.1 and CaV2.2 channels and its implications for asynchronous neurotransmitter release.

TitleAsynchronous Ca2+ current conducted by voltage-gated Ca2+ (CaV)-2.1 and CaV2.2 channels and its implications for asynchronous neurotransmitter release.
Publication TypeJournal Article
Year of Publication2012
AuthorsFew AP, Nanou E, Watari H, Sullivan JM, Scheuer T, Catterall WA
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue7
PaginationE452-60
Date Published2012 Feb 14
ISSN1091-6490
KeywordsAnimals, Calcium, Calcium Channels, N-Type, Ion Channel Gating, Monoterpenes, Neurotransmitter Agents, Synaptic Transmission
Abstract

<p>We have identified an asynchronously activated Ca(2+) current through voltage-gated Ca(2+) (Ca(V))-2.1 and Ca(V)2.2 channels, which conduct P/Q- and N-type Ca(2+) currents that initiate neurotransmitter release. In nonneuronal cells expressing Ca(V)2.1 or Ca(V)2.2 channels and in hippocampal neurons, prolonged Ca(2+) entry activates a Ca(2+) current, I(Async), which is observed on repolarization and decays slowly with a half-time of 150-300 ms. I(Async) is not observed after L-type Ca(2+) currents of similar size conducted by Ca(V)1.2 channels. I(Async) is Ca(2+)-selective, and it is unaffected by changes in Na(+), K(+), Cl(-), or H(+) or by inhibitors of a broad range of ion channels. During trains of repetitive depolarizations, I(Async) increases in a pulse-wise manner, providing Ca(2+) entry that persists between depolarizations. In single-cultured hippocampal neurons, trains of depolarizations evoke excitatory postsynaptic currents that show facilitation followed by depression accompanied by asynchronous postsynaptic currents that increase steadily during the train in parallel with I(Async). I(Async) is much larger for slowly inactivating Ca(V)2.1 channels containing &beta;(2a)-subunits than for rapidly inactivating channels containing &beta;(1b)-subunits. I(Async) requires global rises in intracellular Ca(2+), because it is blocked when Ca(2+) is chelated by 10 mM EGTA in the patch pipette. Neither mutations that prevent Ca(2+) binding to calmodulin nor mutations that prevent calmodulin regulation of Ca(V)2.1 block I(Async). The rise of I(Async) during trains of stimuli, its decay after repolarization, its dependence on global increases of Ca(2+), and its enhancement by &beta;(2a)-subunits all resemble asynchronous release, suggesting that I(Async) is a Ca(2+) source for asynchronous neurotransmission.</p>

DOI10.1073/pnas.1121103109
Alternate JournalProc. Natl. Acad. Sci. U.S.A.