Department of Anesthesiology

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The beta subunit increases the Ca2+ sensitivity of large conductance Ca2+-activated potassium channels by retaining the gating in the bursting states.

TitleThe beta subunit increases the Ca2+ sensitivity of large conductance Ca2+-activated potassium channels by retaining the gating in the bursting states.
Publication TypeJournal Article
Year of Publication1999
AuthorsNimigean CM, Magleby KL
JournalJ Gen Physiol
Volume113
Issue3
Pagination425-40
Date Published1999 Mar
ISSN0022-1295
KeywordsAnimals, Calcium Signaling, Cell Line, Humans, Ion Channel Gating, Kidney, Kinetics, Large-Conductance Calcium-Activated Potassium Channel alpha Subunits, Large-Conductance Calcium-Activated Potassium Channel beta Subunits, Large-Conductance Calcium-Activated Potassium Channels, Muscle, Skeletal, Potassium Channels, Potassium Channels, Calcium-Activated, Rats
Abstract

Coexpression of the beta subunit (KV,Cabeta) with the alpha subunit of mammalian large conductance Ca2+- activated K+ (BK) channels greatly increases the apparent Ca2+ sensitivity of the channel. Using single-channel analysis to investigate the mechanism for this increase, we found that the beta subunit increased open probability (Po) by increasing burst duration 20-100-fold, while having little effect on the durations of the gaps (closed intervals) between bursts or on the numbers of detected open and closed states entered during gating. The effect of the beta subunit was not equivalent to raising intracellular Ca2+ in the absence of the beta subunit, suggesting that the beta subunit does not act by increasing all the Ca2+ binding rates proportionally. The beta subunit also inhibited transitions to subconductance levels. It is the retention of the BK channel in the bursting states by the beta subunit that increases the apparent Ca2+ sensitivity of the channel. In the presence of the beta subunit, each burst of openings is greatly amplified in duration through increases in both the numbers of openings per burst and in the mean open times. Native BK channels from cultured rat skeletal muscle were found to have bursting kinetics similar to channels expressed from alpha subunits alone.

Alternate JournalJ. Gen. Physiol.
PubMed ID10051518
PubMed Central IDPMC2222905
Grant ListAR32805 / AR / NIAMS NIH HHS / United States