Phospholamban ablation rescues the enhanced propensity to arrhythmias of mice with CaMKII-constitutive phosphorylation of RyR2-S2814 site

MAZZOCCHI G; SOMMESE L; PALOMEQUE J; FELICE JI; DI CARLO MN; FAINSTEIN D; GONZALEZ P; CONTRERAS P; SKAPURA DG; MCCAULEY MD; LASCANO E; NEGRONI J; KRANIAS EG; VALVERDE CA; MATTIAZZI A

JOURNAL OF PHYSIOLOGY (PARIS)

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015

0928-4257

Background: Mice with constitutive pseudo-phosphorylation at Ser2814-RyR2 (S2814D+/+), increase the propensity to arrhythmias under β-adrenergic stress conditions. Although abnormal Ca2+ release from the SR has been linked to arrhythmogenesis, the role played by SR Ca2+ uptake remains controversial. We tested the hypothesis that an increase in SR Ca2+ uptake is able to rescue the increased arrhythmia propensity of S2814D+/+ mice. Methods and Results: We generated PLN-deficient/S2814D+/+ knock-in mice by crossing the two colonies (SD+/+KO mice). SD+/+KO myocytes exhibited both, increased SR Ca2+ uptake seen in PLNKO myocytes and diminished SR Ca2+ load (relative to PLNKO), characteristic of S2814D+/+ myocytes. Ventricular arrhythmias evoked by catecholaminergic challenge (caffeine/epinephrine) in S2814D+/+ mice in vivo or programmed electric stimulation and high extracellular Ca2+ in S2814D+/- hearts ex vivo, were significantly diminished by PLN ablation. At the myocyte level, PLN ablation converted the arrhythmogenic Ca2+ waves evoked by high extracellular Ca2+ provocation in S2814D+/+ mice to non-propagated Ca2+ mini-waves on confocal microscopy. Myocyte Ca2+ waves, typical of S2814D+/+ mice, could be evoked in SD+/+KO cells by partially inhibiting SERCA2a. A mathematical human myocyte model replicated these results and allowed for predicting the increase in SR Ca2+ uptake required to prevent the arrhythmias induced by a CaMKII-dependent leaky RyR2. Conclusions: Our results demonstrate that increasing SR Ca2+ uptake by PLN ablation can prevent the arrhythmic events triggered by SR Ca2+ leak due to CaMKII-dependent phosphorylation of S2814-RyR2 site and underscore the benefits of increasing SERCA2a activity on SR Ca2+ triggered arrhythmias.