A Novel Ryanodine Receptor Mutation Linked to Sudden Death Increases Sensitivity to Cytosolic Calcium
Male
0301 basic medicine
Ryanodine Receptor Calcium Release Channel
Middle Aged
Cyclic AMP-Dependent Protein Kinases
Recombinant Proteins
3. Good health
Tacrolimus Binding Proteins
Electrocardiography
03 medical and health sciences
Catecholamines
Cytosol
Death, Sudden, Cardiac
HEK293 Cells
Phenotype
Diastole
Mutagenesis, Site-Directed
Tachycardia, Ventricular
Humans
Point Mutation
Calcium
Ion Channel Gating
DOI:
10.1161/circresaha.111.244970
Publication Date:
2011-06-10T09:07:57Z
AUTHORS (9)
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.
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