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First published online 20 February 2007
doi: 10.1242/jcs.03399


Journal of Cell Science 120, 985-995 (2007)
Published by The Company of Biologists 2007
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Research Article

Co-assembly of N-type Ca2+ and BK channels underlies functional coupling in rat brain

David J. Loane*, Pedro A. Lima{ddagger} and Neil V. Marrion§

Department of Pharmacology and MRC Centre for Synaptic Plasticity, University of Bristol, Bristol, BS8 1TD, UK

§ Author for correspondence (e-mail: N.V.Marrion{at}bris.ac.uk)

Accepted 9 January 2007

Activation of large conductance Ca2+-activated potassium (BK) channels hastens action potential repolarisation and generates the fast afterhyperpolarisation in hippocampal pyramidal neurons. A rapid coupling of Ca2+ entry with BK channel activation is necessary for this to occur, which might result from an identified coupling of Ca2+ entry through N-type Ca2+ channels to BK channel activation. This selective coupling was extremely rapid and resistant to intracellular BAPTA, suggesting that the two channel types are close. Using reciprocal co-immunoprecipitation, we found that N-type channels were more abundantly associated with BK channels than L-type channels (CaV1.2) in rat brain. Expression of only the pore-forming {alpha}-subunits of the N-type (CaV2.2) and BK (Slo27) channels in a non-neuronal cell-line gave robust macroscopic currents and reproduced the interaction. Co-expression of CaV2.2/CaVbeta3 subunits with Slo27 channels revealed rapid functional coupling. By contrast, extremely rare examples of rapid functional coupling were observed with co-expression of CaV1.2/CaVbeta3 and Slo27 channels. Action potential repolarisation in hippocampal pyramidal neurons was slowed by the N-type channel blocker {omega}-conotoxin GVIA, but not by the L-type channel blocker isradipine. These data showed that selective functional coupling between N-type Ca2+ and BK channels provided rapid activation of BK channels in central neurons.

Key words: Co-immunoprecipitation, Channel coupling, Hippocampus, Action potential




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