Wanderlust kinetics and variable Ca2+-sensitivity of Drosophila, a large conductance Ca2+-activated K+ channel, expressed in oocytes

Shai D. Silberberg, Armando Lagrutta, John P. Adelman, Karl L. Magleby

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Cloned large conductance Ca2+-activated K+ channels (BK or maxi-K+ channels) from Drosophila (dSlo) were expressed in Xenopus oocytes and studied in excised membrane patches with the patch-clamp technique. Both a natural variant and a mutant that eliminated a putative cyclic AMP-dependent protein kinase phosphorylation site exhibited large, slow fluctuations in open probability with time. These fluctuations, termed "wanderlust kinetics," occurred with a time course of tens of seconds to minutes and had kinetic properties inconsistent with simple gating models. Wanderlust kinetics was still observed in the presence of 5 mM caffeine or 50 nM thapsigargin, or when the Ca2+ buffering capacity of the solution was increased by the addition of 5 mM HEDTA, suggesting that the wanderlust kinetics did not arise from Ca2+ release from caffeine and thapsigargin sensitive internal stores in the excised patch. The slow changes in kinetics associated with wanderlust kinetics could be generated with a discrete-state Markov model with transitions among three or more kinetic modes with different levels of open probability. To average out the wanderlust kinetics, large amounts of data were analyzed and demonstrated up to a threefold difference in the [Ca2+], required for an open probability of 0.5 among channels expressed from the same injected mRNA. These findings indicate that cloned dSlo channels in excised patches from Xenopus oocytes can exhibit large variability in gating properties, both within a single channel and among channels.

Original languageEnglish (US)
Pages (from-to)2640-2651
Number of pages12
JournalBiophysical journal
Volume70
Issue number6
DOIs
StatePublished - Jun 1996

ASJC Scopus subject areas

  • Biophysics

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