Role of chronic ryanodine receptor phosphorylation in heart failure and β-adrenergic receptor blockade in mice

Abstract

Increased sarcoplasmic reticulum (SR) Ca 2+ leak via the cardiac ryanodine receptor/calcium release channel (RyR2) is thought to play a role in heart failure (HF) progression. Inhibition of this leak is an emerging therapeutic strategy. To explore the role of chronic PKA phosphorylation of RyR2 in HF pathogenesis and treatment, we generated a knockin mouse with aspartic acid replacing serine 2808 (mice are referred to herein as RyR2-S2808D +/+ mice). This mutation mimics constitutive PKA hyperphosphorylation of RyR2, which causes depletion of the stabilizing subunit FKBP12.6 (also known as calstabin2), resulting in leaky RyR2. RyR2-S2808D +/+ mice developed age-dependent cardiomyopathy, elevated RyR2 oxidation and nitrosylation, reduced SR Ca 2+ store content, and increased diastolic SR Ca 2+ leak. After myocardial infarction, RyR2-S2808D +/+ mice exhibited increased mortality compared with WT littermates. Treatment with S107, a 1,4-benzothiazepine derivative that stabilizes RyR2-calstabin2 interactions, inhibited the RyR2-mediated diastolic SR Ca 2+ leak and reduced HF progression in WT and RyR2-S2808D +/+ mice. In contrast, β-adrenergic receptor blockers improved cardiac function in WT but not in RyR2-S2808D +/+ mice.Thus, chronic PKA hyperphosphorylation of RyR2 results in a diastolic leak that causes cardiac dysfunction. Reversing PKA hyperphosphorylation of RyR2 is an important mechanism underlying the therapeutic action of β-blocker therapy in HF.

Identifying cellular mechanisms of zinc-induced relaxation in isolated cardiomyocytes

“…Our finding that Zn 2ϩ reduces RyR S2808 phosphorylation is novel and potentially important in cardiomyocyte Ca 2ϩ regulation. Phosphorylation of RyR S2808 has been associated with increased RyR open probability and SR Ca 2ϩ leak due to dissociation of the stabilizing protein FKBP1B (16,29). Phosphorylation of RyR S2808 has been found especially high in the context of hyperglycemia and diabetes (30,38,39).…”

“…Phosphorylation of RyR S2808 has already been demonstrated to be associated with a high open probability of RyR and SR Ca 2ϩ leak (16,29). We were curious to test if Zn 2ϩ exposure could alter RyR S2808 phosphorylation and thus signal an effect on SR Ca 2ϩ leak, which could underlie diastolic function.…”

Targeting ryanodine receptors for anti-arrhythmic therapy

“…Further, S107 was recently shown to be effective at preventing ventricular arrhythmias in the mdx mouse model of muscular dystrophy [56] . Thus, 1,4-benzothiazepine derivatives JTV519 and S107 hold promise as RyR2-stabilizing molecules that could reduce the risk of arrhythmias [57] .…”

“…Shan et al [57] demonstrated that mice in which RyR2 was constitutively by PKA (RyR2-S2808D knock-in mice) exhibited an increased open probability, more calcium sparks, and increased SR Ca 2+ leak. Inhibition of PKA phosphorylation of RyR2 in RyR2-S2808A mice was shown to protect against catecholamineinduced ventricular arrhythmias [72] .…”

Is ryanodine receptor phosphorylation key to the fight or flight response and heart failure?

“…Yet, this is only partially the case, as shown by two studies from the Marks laboratory published in this issue of the JCI (25,26). The two papers report on two new mouse models: one in which the S2808 site was mutated to a non-phosphorylatable alanine (S2808A; ref.…”