2. Academic Validation
  3. Novel CPVT-Associated Calmodulin Mutation in CALM3 (CALM3-A103V) Activates Arrhythmogenic Ca Waves and Sparks

Novel CPVT-Associated Calmodulin Mutation in CALM3 (CALM3-A103V) Activates Arrhythmogenic Ca Waves and Sparks

  • Circ Arrhythm Electrophysiol. 2016 Aug;9(8):10.1161/CIRCEP.116.004161 e004161. doi: 10.1161/CIRCEP.116.004161.
Nieves Gomez-Hurtado 1,  Nicole J Boczek 1,  Dmytro O Kryshtal 1,  Christopher N Johnson 1,  Jennifer Sun 1,  Florentin R Nitu 1,  Razvan L Cornea 1,  Walter J Chazin 1,  Melissa L Calvert 1,  David J Tester 1,  Michael J Ackerman 2,  Björn C Knollmann 2
Affiliations

Affiliations

  • 1 From the Vanderbilt Center for Arrhythmia Research and Therapeutics (VanCART), Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN (N.G.-H., D.O.K., B.C.K.); Department Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (N.J.B., M.L.C., D.J.T., M.J.A.), Department of Cardiovascular Diseases, Division of Heart Rhythm Services (M.J.A.), and Department of Pediatrics, Division of Pediatric Cardiology (M.J.A.), Mayo Clinic, Rochester, MN; Departments of Biochemistry and Chemistry & Center for Structural Biology, Vanderbilt University, Nashville, TN (C.N.J., J.S., W.J.C.); and Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN (F.R.N., R.L.C.).
  • 2 From the Vanderbilt Center for Arrhythmia Research and Therapeutics (VanCART), Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN (N.G.-H., D.O.K., B.C.K.); Department Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory (N.J.B., M.L.C., D.J.T., M.J.A.), Department of Cardiovascular Diseases, Division of Heart Rhythm Services (M.J.A.), and Department of Pediatrics, Division of Pediatric Cardiology (M.J.A.), Mayo Clinic, Rochester, MN; Departments of Biochemistry and Chemistry & Center for Structural Biology, Vanderbilt University, Nashville, TN (C.N.J., J.S., W.J.C.); and Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN (F.R.N., R.L.C.). [email protected] [email protected].
PMID: 27516456 DOI: 10.1161/CIRCEP.116.004161
Abstract

Background: Calmodulin (CaM) mutations are associated with severe forms of long QT syndrome and catecholaminergic polymorphic ventricular tachycardia (CPVT). CaM mutations are found in 13% of genotype-negative long QT syndrome patients, but the prevalence of CaM mutations in genotype-negative CPVT patients is unknown. Here, we identify and characterize CaM mutations in 12 patients with genotype-negative but clinically diagnosed CPVT.

Methods and results: We performed mutational analysis of CALM1, CALM2, and CALM3 gene-coding regions, in vitro measurement of CaM-Ca(2+) (Ca)-binding affinity, ryanodine receptor 2-CaM binding, Ca handling, L-type Ca current, and action potential duration. We identified a novel CaM mutation-A103V-in CALM3 in 1 of 12 patients (8%), a female who experienced episodes of exertion-induced syncope since age 10, had normal QT interval, and displayed ventricular ectopy during stress testing consistent with CPVT. A103V modestly lowered CaM Ca-binding affinity (3-fold reduction versus WT-CaM), but did not alter CaM binding to ryanodine receptor 2. In permeabilized cardiomyocytes, A103V-CaM (100 nmol/L) promoted spontaneous Ca wave and spark activity, a cellular phenotype of ryanodine receptor 2 activation. Even a 1:3 mixture of A103V-CaM:WT-CaM activated Ca waves, demonstrating functional dominance. Compared with long QT syndrome D96V-CaM, A103V-CaM had significantly less effects on L-type Ca current inactivation, did not alter action potential duration, and caused delayed afterdepolarizations and triggered beats in intact cardiomyocytes.

Conclusions: We discovered a novel CPVT mutation in the CALM3 gene that shares functional characteristics with established CPVT-associated mutations in CALM1. A small proportion of A103V-CaM is sufficient to evoke arrhythmogenic Ca disturbances via ryanodine receptor 2 dysregulation, which explains the autosomal dominant inheritance.

Keywords

calcium; calcium channel; calmodulin; catecholaminergic polymorphic ventricular tachycardia; ryanodine receptor.

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