title: Co-assembly of N-type Ca2+ and BK channels underlies functional coupling in rat brain.
abstract: Activation of large conductance Ca(2+)-activated potassium (BK) channels hastens action potential repolarisation and generates the fast afterhyperpolarisation in hippocampal pyramidal neurons. A rapid coupling of Ca(2+) entry with BK channel activation is necessary for this to occur, which might result from an identified coupling of Ca(2+) entry through N-type Ca(2+) 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 (Ca(V)1.2) in rat brain. Expression of only the pore-forming alpha-subunits of the N-type (Ca(V)2.2) and BK (Slo(27)) channels in a non-neuronal cell-line gave robust macroscopic currents and reproduced the interaction. Co-expression of Ca(V)2.2/Ca(V)beta(3) subunits with Slo(27) channels revealed rapid functional coupling. By contrast, extremely rare examples of rapid functional coupling were observed with co-expression of Ca(V)1.2/Ca(V)beta(3) and Slo(27) 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 Ca(2+) and BK channels provided rapid activation of BK channels in central neurons.
authors.affiliation: Department of Pharmacology and MRC Centre for Synaptic Plasticity, University of Bristol, Bristol, BS8 1TD, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Loane
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Lima
authors.forename: Neil V
authors.initials: NV
authors.lastname: Marrion
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D020746:Calcium Channels, L-Type / Q000502:physiology*; D020864:Calcium Channels, N-Type / Q000502:physiology*; D002460:Cell Line; D006624:Hippocampus / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects; D017275:Isradipine / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D021122:Protein Subunits / Q000502:physiology*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: C503279:Cacna1b protein, rat; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; C419385:L-type calcium channel alpha(1C); D051036:Large-Conductance Calcium-Activated Potassium Channels; D021122:Protein Subunits; D020866:omega-Conotoxin GVIA; D017275:Isradipine