Voltage- and Ca2+-activated potassium channels in Ca2+ store control Ca2+ release

FEBS J. 2006 Aug;273(15):3585-97. doi: 10.1111/j.1742-4658.2006.05365.x.


Ca2+ release from Ca2+ stores is a 'quantal' process; it terminates after a rapid release of stored Ca2+. To explain the quantal nature, it has been supposed that a decrease in luminal Ca2+ acts as a 'brake' on store release. However, the mechanism for the attenuation of Ca2+ efflux remains unknown. We show that Ca2+ release is controlled by voltage- and Ca2+-activated potassium channels in the Ca2+ store. The potassium channel was identified as the big or maxi-K (BK)-type, and was activated by positive shifts in luminal potential and luminal Ca2+ increases, as revealed by patch-clamp recordings from an exposed nuclear envelope. The blockage or closure of the store BK channel due to Ca2+ efflux developed lumen-negative potentials, as revealed with an organelle-specific voltage-sensitive dye [DiOC5(3); 3,3'-dipentyloxacarbocyanine iodide], and suppressed Ca2+ release. The store BK channels are reactivated by Ca2+ uptake by Ca2+ pumps regeneratively with K+ entry to allow repetitive Ca2+ release. Indeed, the luminal potential oscillated bistably by approximately 45 mV in amplitude. Our study suggests that Ca2+ efflux-induced store BK channel closures attenuate Ca2+ release with decreases in counter-influx of K+.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Cells, Cultured
  • Electroporation
  • Ion Channel Gating*
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Oxidation-Reduction
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism
  • Potassium Channels / physiology*


  • Potassium Channels
  • Calcium