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

ABSTRACT: 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.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.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.

SUBMITTER: Gomez-Hurtado N

PROVIDER: S-EPMC4988333 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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

Gomez-Hurtado Nieves N Boczek Nicole J NJ Kryshtal Dmytro O DO Johnson Christopher N CN Sun Jennifer J Nitu Florentin R FR Cornea Razvan L RL Chazin Walter J WJ Calvert Melissa L ML Tester David J DJ Ackerman Michael J MJ Knollmann Björn C BC

Circulation. Arrhythmia and electrophysiology 20160801 8

<h4>Background</h4>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.<h4>Methods and results</h4>We performed mutational anal ...[more]

PMID: 27516456

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Project description:Phospholamban (PLN) is an inhibitor of cardiac sarco(endo)plasmic reticulum Ca²? ATPase. PLN knockout (PLN-KO) enhances sarcoplasmic reticulum Ca²? load and Ca²? leak. Conversely, PLN-KO accelerates Ca²? sequestration and aborts arrhythmogenic spontaneous Ca²? waves (SCWs). An important question is whether these seemingly paradoxical effects of PLN-KO exacerbate or protect against Ca²?-triggered arrhythmias.We investigate the impact of PLN-KO on SCWs, triggered activities, and stress-induced ventricular tachyarrhythmias (VTs) in a mouse model of cardiac ryanodine-receptor (RyR2)-linked catecholaminergic polymorphic VT.We generated a PLN-deficient, RyR2-mutant mouse model (PLN-/-/RyR2-R4496C+/-) by crossbreeding PLN-KO mice with catecholaminergic polymorphic VT-associated RyR2-R4496C mutant mice. Ca²? imaging and patch-clamp recording revealed cell-wide propagating SCWs and triggered activities in RyR2-R4496C+/- ventricular myocytes during sarcoplasmic reticulum Ca²? overload. PLN-KO fragmented these cell-wide SCWs into mini-waves and Ca²? sparks and suppressed the triggered activities evoked by sarcoplasmic reticulum Ca²? overload. Importantly, these effects of PLN-KO were reverted by partially inhibiting sarco(endo)plasmic reticulum Ca²? ATPase with 2,5-di-tert-butylhydroquinone. However, Bay K, caffeine, or Li? failed to convert mini-waves to cell-wide SCWs in PLN-/-/RyR2-R4496C+/- ventricular myocytes. Furthermore, ECG analysis showed that PLN-KO mice are not susceptible to stress-induced VTs. On the contrary, PLN-KO protected RyR2-R4496C mutant mice from stress-induced VTs.Our results demonstrate that despite severe sarcoplasmic reticulum Ca²? leak, PLN-KO suppresses triggered activities and stress-induced VTs in a mouse model of catecholaminergic polymorphic VT. These data suggest that breaking up cell-wide propagating SCWs by enhancing Ca²? sequestration represents an effective approach for suppressing Ca²?-triggered arrhythmias.

Dataset Information

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

Publications

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

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