2. Academic Validation
  3. Arrhythmogenic calmodulin mutations impede activation of small-conductance calcium-activated potassium current

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

  • Heart Rhythm. 2016 Aug;13(8):1716-23. doi: 10.1016/j.hrthm.2016.05.009.
Chih-Chieh Yu 1,  Jum-Suk Ko 2,  Tomohiko Ai 3,  Wen-Chin Tsai 4,  Zhenhui Chen 5,  Michael Rubart 6,  Matteo Vatta 7,  Thomas H Everett 4th 5,  Alfred L George Jr 8,  Peng-Sheng Chen 9
Affiliations

Affiliations

  • 1 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
  • 2 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Iksan, Korea.
  • 3 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Molecular Pathogenesis, Medical Research Institute; Department of Emergency Medicine, Tokyo Medical and Dental University, Tokyo, Japan.
  • 4 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Hualien Tzu-Chi General Hospital, Hualien City, Taiwan.
  • 5 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana.
  • 6 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Pediatrics, Riley Heart Research Center.
  • 7 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana.
  • 8 Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
  • 9 Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana. Electronic address: [email protected].
PMID: 27165696 DOI: 10.1016/j.hrthm.2016.05.009
Abstract

Background: Apamin-sensitive small-conductance calcium-activated potassium (SK) channels are gated by intracellular Ca(2+) 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.

Keywords

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

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