Rectification and rapid activation at low Ca2+ of Ca2+-activated, voltage-dependent BK currents: Consequences of rapid inactivation by a novel β subunit

Xiao Ming Xia, Jiu Ping Ding, Xu Hui Zeng, Kai Lai Duan, Christopher J. Lingle

Research output: Contribution to journalArticle

142 Scopus citations

Abstract

A family of accessory β subunits significantly contributes to the functional diversity of large-conductance, Ca2+- and voltage-dependent potassium (BK) channels in native cells. Here we describe the functional properties of one variant of the β subunit family, which confers properties on BK channels totally unlike any that have as yet been observed. Coexpression of this subunit (termed β3) with Slo α subunits results in rectifying outward currents and, at more positive potentials, rapidly inactivating (~1 msec) currents. The underlying rapid inactivation process results in an increase in the apparent activation rate of macroscopic currents, which is coupled with a shift in the activation range of the currents at low Ca2+. AS a consequence, the currents exhibit more rapid activation at low Ca2+ relative to any other BK channel subunit combinations that have been examined. In part because of the rapid inactivation process, single channel openings are exceedingly brief. Although variance analysis suggests a conductance in excess of 160 pS, fully resolved single channel openings are not observed. The inactivation process results from a cytosolic N-terminal domain of the β3 subunit, whereas an extended C- terminal domain does not participate in the inactivation process. Thus, the β3 subunit appears to use a rapid inactivation mechanism to produce a current with a relatively rapid apparent activation time course at low Ca2+. The β3 subunit is a compelling example of how the β subunit family can finely tune the gating properties of Ca2+- and voltage-dependent BK channels.

Original languageEnglish
Pages (from-to)4890-4903
Number of pages14
JournalJournal of Neuroscience
Volume20
Issue number13
StatePublished - Jul 1 2000

Keywords

  • Accessory subunits
  • BK channels
  • Ca- and voltage-gated K channels
  • Inactivation
  • K channels
  • mSlo channels

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