Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disease that manifests as
syncope or
sudden death during high
adrenergic tone in the absence of structural heart defects. It is primarily caused by mutations in the cardiac
ryanodine receptor (
RyR2). The mechanism by which these mutations cause
arrhythmia remains controversial, with discrepant findings related to the role of the
RyR2 binding protein FKBP12.6. The purpose of this study was to characterize a novel
RyR2 mutation identified in a kindred with clinically diagnosed CPVT. Single-strand conformational polymorphism analysis and direct
DNA sequencing were used to screen the
RyR2 gene for mutations. Site-directed mutagenesis was employed to introduce the mutation into the mouse
RyR2 cDNA. The impact of the mutation on the interaction between
RyR2 and a 12.6 kDa
FK506 binding protein (
FKBP12.6) was determined by immunoprecipitation and immunoblotting and its effect on
RyR2 function was characterized by single cell Ca(2+) imaging and [(3)H]
ryanodine binding. A novel CPVT mutation, E189D, was identified. The E189D mutation does not alter the affinity of the channel for
FKBP12.6, but it increases the propensity for store-overload-induced Ca(2+) release (SOICR). Furthermore, the E189D mutation enhances the basal channel activity of
RyR2 and its sensitivity to activation by
caffeine. The E189D
RyR2 mutation is causative for CPVT and functionally increases the propensity for SOICR without altering the affinity for
FKBP12.6. These observations strengthen the notion that enhanced SOICR, but not altered
FKBP12.6 binding, is a common mechanism by which
RyR2 mutations cause arrhythmias.