FKBP12.6 Binding Characteristics of Ryanodine Receptor Mutations Associated with Arrhythmogenic Cardiac Disease

Abstract

The cardiac muscle ryanodine receptor-calcium release channel (RyR2) and its interaction with an accessory protein, FK506-binding protein (FKBP12.6), have been implicated in the molecular pathogenesis of acquired and inherited cardiac disease (e.g. catecholaminergic polymorphic ventricular tachycardia; CPVT). We have assessed the FKBP12.6 binding characteristics of recombinant wild-type and CPVT mutant RyR2 channels under basal and oxidising conditions. We find that the R176Q and S2246L mutations exhibit an increased FKBP12.6 binding by ∼40% and ∼20% respectively, whereas R4497C was similar to wild-type. The redox sensitivity of the FKBP12.6 interaction with the mutant RyR2 channels was very similar to wild-type. The oxidising reagents H2O2 and diamide resulted in reduced FKBP12.6 binding by ∼10% and by ∼50%, respectively, compared to the untreated state for all four RyR2 proteins. These results suggest that the FKBP12.6 regulation of RyR2 is unlikely to be defective in inherited arrhythmogenic cardiac disease.