Characterization of a Functionally Expressed Stretch-activated BKca Channel Cloned from Chick Ventricular Myocytes

Q. Y. Tang, Z. Qi, K. Naruse, M. Sokabe

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

We have characterized electrophysiological and pharmacological properties of a stretch-activated BKca channel (SAKcaC) that was cloned from cultured chick ventricular myocytes (CCVM) and expressed in Chinese hamster ovary cells (CHO) using the patch-clamp technique. Our results indicate that the cloned SAKcaC keeps most of the key properties of the native SAKcaC in CCVM, such as conductance, ion selectivity, pressure-, voltage- and Ca2+- dependencies. However, there was a slight difference between these channels in the effects of channel blockers, charybdotoxin (CTX) and gadolinium (Gd 3+). The native SAKcaC was blocked in an all-or-none fashion characterized as the slow blockade, whereas the conductance of the cloned SAKcaC was gradually decreased with the blockers' concentration, without noticeable blocking noise. As the involvement of some auxiliary components was suspected in this difference, we cloned a BK β-subunit from CCVM and coexpressed it with the cloned SAKcaC in CHO cells to examine its effects on the SAKcaC. Although the pharmacological properties of the cloned SAKcaC turned out to be very similar to the native one by the coexpression, it also significantly altered the key characteristics of SAKcaC, such as voltage- and Ca2+-dependencies. Therefore we concluded that the native SAKca in CCVM does not interact with the corresponding endogenous β-subunit. The difference in pharmacological properties between the expressed SAKcaC in CHO and the native one in CCVM suggests that the native SAKca in CCVM is modulated by unknown auxiliary components.

Original languageEnglish
Pages (from-to)185-200
Number of pages16
JournalJournal of Membrane Biology
Volume196
Issue number3
DOIs
Publication statusPublished - Dec 1 2003
Externally publishedYes

Keywords

  • BK channel
  • Channel blockade
  • Functional expression
  • Gating
  • Gene cloning
  • Heart
  • SA channel
  • β subunit

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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