Impaired Binding to Junctophilin-2 and Nanostructural Alteration in CPVT Mutation
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Date
2021-07-23
Author
Yin, Liheng, Jr, Alexandra Zahradnikova, Rizzetto, Riccardo, Boncompagni, Simona, Meritens, Camille Rabesahala de, Zhang, Yadan, Joanne, Pierre, Marqués-Sulé, Elena, Aguilar-Sánchez, Yuriana, Fernández-Tenorio, Miguel, Villejoubert, Olivier, Li, Linwei, Wang, Yue Yi, Mateo, Philippe, Nicolas, Valérie, Gerbaud, Pascale, Lai, F. Anthony, Perrier, Romain, Álvarez, Julio L., Niggli, Ernst, Valdivia, Héctor H., Valdivia, Carmen R., Ramos-Franco, Josefina, Zorio, Esther, Zissimopoulos, Spyros, Protasi, Feliciano, Benitah, Jean-Pierre, Gómez, Ana M.
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Abstract
RATIONALE: Catecholaminergic polymorphic ventricular tachycardia is a rare disease, manifested by syncope or sudden death
in children or young adults under stress conditions. Mutations in the Ca2+ release channel/type 2 ryanodine receptor (RyR2)
gene account for about 60% of the identified mutations. Recently, we found and described a mutation in RyR2 N-terminal
domain, RyR2R420Q.
OBJECTIVE: To determine the arrhythmogenic mechanisms of this mutation.
METHODS AND RESULTS: Ventricular tachycardias under stress conditions were observed in both patients with catecholaminergic
polymorphic ventricular tachycardia and knock-in mice. During action potential recording (by patch-clamp in knock-in mouse
cardiomyocytes and by microelectrodes in mutant human induced pluripotent stem cell-derived cardiomyocytes), we observed
an increased occurrence of delayed afterdepolarizations under isoproterenol stimulation, associated with increased Ca2+ waves
during confocal Ca2+ recording in both mouse and human RyR2R420Q cardiomyocytes. In addition, Ca2+-induced Ca2+-release,
as well as a rough indicator of fractional Ca2+ release, were higher and Ca2+ sparks longer in the RyR2R420Q-expressing cells.
At the ultrastructural nanodomain level, we observed smaller RyR2 clusters and widened junctional sarcoplasmic reticulum
measured by gated stimulated emission depletion super-resolution and electronic microscopy, respectively. The increase in
junctional sarcoplasmic reticulum width might be due to the impairment of RyR2R420Q binding to junctophilin-2, as there were
less junctophilin-2 coimmunoprecipitated with RyR2R420Q. At the single current level, the RyR2R420Q channel dwells longer in
the open state at low intracellular Ca2+ ([Ca2+]i), but there is predominance of a subconductance state. The latter might be
correlated with an enhanced interaction between the N terminus and the core solenoid, a RyR2 interdomain association that
has not been previously implicated in the pathogenesis of arrhythmias and sudden cardiac death.
CONCLUSIONS: The RyR2R420Q catecholaminergic polymorphic ventricular tachycardia mutation modifies the interdomain
interaction of the channel and weakens its association with junctophillin-2. These defects may underlie both nanoscale
disarrangement of the dyad and channel dysfunction.
GRAPHIC ABSTRACT: An online graphic abstract is available for this article.