Arrhythmogenic calmodulin mutations impede activation of small-conductance calcium-activated potassium current

Chih Chieh Yu, Jum Suk Ko, Tomohiko Ai, Wen Chin Tsai, Zhenhui Chen, Michael Rubart, Matteo Vatta, Thomas H. Everett, Alfred L. George, Peng Sheng Chen

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Background Apamin-sensitive small-conductance calcium-activated potassium (SK) channels are gated by intracellular Ca2+ through a constitutive interaction with calmodulin. Objective We hypothesize that arrhythmogenic human calmodulin mutations impede activation of SK channels. Methods We studied 5 previously published calmodulin mutations (N54I, N98S, D96V, D130G, and F90L). Plasmids encoding either wild-type or mutant calmodulin were transiently transfected into human embryonic kidney 293 cells that stably express subtype 2 of SK protein channels (SK2 cells). Whole-cell voltage-clamp recording was used to determine apamin-sensitive current densities. We also performed optical mapping studies in normal murine hearts to determine the effects of apamin in hearts with (n=7) or without (n=3) pretreatment with sea anemone toxin. Results SK2 cells transfected with wild-type calmodulin exhibited an apamin-sensitive current density of 33.6 pA/pF (31.4–36.5 pA/pF) (median and confidence interval 25th–75th percentile), which was significantly higher than that observed for cells transfected with N54I (17.0 pA/pF [14.0–27.7 pA/pF]; P = .016), F90L (22.6 pA/pF [20.3–24.3 pA/pF]; P = .011), D96V (13.0 pA/pF [10.9–15.8 pA/pF]; P = .003), N98S (13.7 pA/pF [8.8–20.4 pA/pF]; P = .005), and D130G (17.6 pA/pF [13.8–24.6 pA/pF]; P = .003). The decrease in SK2 current densities was not associated with a decrease in membrane protein expression or intracellular distribution of the channel protein. Apamin increased the ventricular action potential duration at 80% repolarization (from 79.6 ms [63.4–93.3 ms] to 121.8 ms [97.9–127.2 ms]; P = .010) in hearts pretreated with anemone toxin but not in control hearts. Conclusion Human arrhythmogenic calmodulin mutations impede the activation of SK2 channels in human embryonic kidney 293 cells.

Original languageEnglish (US)
Pages (from-to)1716-1723
Number of pages8
JournalHeart Rhythm
Volume13
Issue number8
DOIs
StatePublished - Aug 1 2016

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Keywords

  • Arrhythmias
  • Catecholaminergic polymorphic ventricular tachycardia
  • Ion channels
  • Long QT syndrome
  • Patch clamp

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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