Leaky Ca2+ release channel/ryanodine receptor 2 causes seizures and sudden cardiac death in mice
Stephan E. Lehnart, … , Gregory Morley, Andrew R. Marks
Stephan E. Lehnart, … , Gregory Morley, Andrew R. Marks
Published May 15, 2008
Citation Information: J Clin Invest. 2008;118(6):2230-2245. https://doi.org/10.1172/JCI35346.
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Research Article Cardiology

Leaky Ca2+ release channel/ryanodine receptor 2 causes seizures and sudden cardiac death in mice

Abstract

The Ca2+ release channel ryanodine receptor 2 (RyR2) is required for excitation-contraction coupling in the heart and is also present in the brain. Mutations in RyR2 have been linked to exercise-induced sudden cardiac death (catecholaminergic polymorphic ventricular tachycardia [CPVT]). CPVT-associated RyR2 mutations result in “leaky” RyR2 channels due to the decreased binding of the calstabin2 (FKBP12.6) subunit, which stabilizes the closed state of the channel. We found that mice heterozygous for the R2474S mutation in Ryr2 (Ryr2-R2474S mice) exhibited spontaneous generalized tonic-clonic seizures (which occurred in the absence of cardiac arrhythmias), exercise-induced ventricular arrhythmias, and sudden cardiac death. Treatment with a novel RyR2-specific compound (S107) that enhances the binding of calstabin2 to the mutant Ryr2-R2474S channel inhibited the channel leak and prevented cardiac arrhythmias and raised the seizure threshold. Thus, CPVT-associated mutant leaky Ryr2-R2474S channels in the brain can cause seizures in mice, independent of cardiac arrhythmias. Based on these data, we propose that CPVT is a combined neurocardiac disorder in which leaky RyR2 channels in the brain cause epilepsy, and the same leaky channels in the heart cause exercise-induced sudden cardiac death.

Authors

Stephan E. Lehnart, Marco Mongillo, Andrew Bellinger, Nicolas Lindegger, Bi-Xing Chen, William Hsueh, Steven Reiken, Anetta Wronska, Liam J. Drew, Chris W. Ward, W.J. Lederer, Robert S. Kass, Gregory Morley, Andrew R. Marks

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Figure 6

RyR2 channels from heterozygous Ryr2RS/WT hearts show a gain-of-function defect that is rescued by S107 treatment.

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RyR2 channels from heterozygous Ryr2RS/WT hearts show a gain-of-function...
(A) Representative single-channel traces from isolated from the hearts of sedentary Ryr2RS/WT mice (RS/WT), after maximal exercise followed by injection of 0.5 mg/kg epinephrine (RS/WT + EPI), or after 1 week treatment with S107 (5 mg/kg/h) followed by maximal exercise and EPI injection (RS/WT + EPI + S107). Thick horizontal bars below 5-second traces indicate area shown in 0.5-second traces. Po, mean open (To) and mean (Tc) closed times, closed state (c), and fully open level (4 pA) are as indicated. Corresponding all-point histograms demonstrate altered current amplitude distribution, including multiple subconductance states and full open events in the EPI group, consistent with a gain-of-function defect. In contrast, S107-treated group histograms show redistribution toward closed states. (B) Average Po of single cardiac WT and Ryr2RS/WT channels under different treatment conditions. Single-channel measurements were performed in low activating Ca2+ concentrations (150 nM) to mimic diastolic conditions. *P < 0.05 versus hearts from sedentary mice; #P < 0.05 versus hearts from exercise- and EPI-treated mice; †P < 0.05 between sedentary and EPI-treated Ryr2RS/WT mice. Each bar represents the average of 7 channels. (C–E) Equivalent amounts of RyR2 were immunoprecipitated with an RyR2-specific antibody followed by immunoblotting: amounts of relative PKA phosphorylation of RyR2 at Ser2808 (D) and of calstabin2 bound to RyR2 (E) under the indicated conditions. Data refer to the same cardiac vesicles used in A and B. *P < 0.05 versus hearts from sedentary mice; #P < 0.05 versus hearts from exercise- and EPI-treated mice.