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Circ Res. 2011 Jul 22;109(3):281-90. doi: 10.1161/CIRCRESAHA.111.244970. Epub 2011 Jun 9.

A novel ryanodine receptor mutation linked to sudden death increases sensitivity to cytosolic calcium.

Author information

1
Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY, USA.

Abstract

RATIONALE:

Mutations in the cardiac type 2 ryanodine receptor (RyR2) have been linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT-associated RyR2 mutations cause fatal ventricular arrhythmias in young individuals during β-adrenergic stimulation.

OBJECTIVE:

This study sought to determine the effects of a novel RyR2-G230C mutation and whether this mutation and RyR2-P2328S alter the sensitivity of the channel to luminal calcium (Ca(2+)).

METHODS AND RESULTS:

Functional characterizations of recombinant human RyR2-G230C channels were performed under conditions mimicking stress. Human RyR2 mutant channels were generated by site-directed mutagenesis and heterologously expressed in HEK293 cells together with calstabin2. RyR2 channels were measured to examine the regulation of the channels by cytosolic versus luminal sarcoplasmic reticulum Ca(2+). A 50-year-old white man with repeated syncopal episodes after exercise had a cardiac arrest and harbored the mutation RyR2-G230C. cAMP-dependent protein kinase-phosphorylated RyR2-G230C channels exhibited a significantly higher open probability at diastolic Ca(2+) concentrations, associated with a depletion of calstabin2. The luminal Ca(2+) sensitivities of RyR2-G230C and RyR2-P2328S channels were WT-like.

CONCLUSIONS:

The RyR2-G230C mutant exhibits similar biophysical defects compared with previously characterized CPVT mutations: decreased binding of the stabilizing subunit calstabin2 and a leftward shift in the Ca(2+) dependence for activation under conditions that simulate exercise, consistent with a "leaky" channel. Both RyR2-G230C and RyR2-P2328S channels exhibit normal luminal Ca(2+) activation. Thus, diastolic sarcoplasmic reticulum Ca(2+) leak caused by reduced calstabin2 binding and a leftward shift in the Ca(2+) dependence for activation by diastolic levels of cytosolic Ca(2+) is a common mechanism underlying CPVT.

PMID:
21659649
PMCID:
PMC3690513
DOI:
10.1161/CIRCRESAHA.111.244970
[Indexed for MEDLINE]
Free PMC Article
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