Stress Signaling JNK2 Crosstalk with CaMKII Underlies Enhanced Atrial Arrhythmogenesis
Rationale: Atrial fibrillation (AF) is the most common arrhythmia and advanced age is an inevitable and predominant AF risk factor. However, the mechanisms that couple aging and AF propensity remain unclear, making targeted therapeutic interventions unattainable.
Objective: To explore the functional role of an important stress-response c-Jun N-terminal kinase (JNK) in sarcoplasmic reticulum (SR) Ca2+ handling and consequently Ca2+-mediated atrial arrhythmias.
Methods and Results: We employed a series of cutting-edge electrophysiological and molecular techniques, exploited the power of transgenic mouse models to detail the molecular mechanism, and verified its clinical applicability in parallel studies on donor human hearts. We discovered that significantly increased activity of the stress-response kinase JNK isoform 2 (JNK2) in the aged atria is involved in arrhythmic remodeling. The JNK-driven atrial pro-arrhythmic mechanism is supported by a pathway linking JNK, CaMKII, and SR Ca2+ release ryanodine receptor (RyR) channels. JNK2 activates CaMKII, a critical pro-arrhythmic molecule in cardiac muscle. In turn, activated CaMKII up-regulates diastolic SR Ca2+ leak mediated by RyR channels. This leads to aberrant intracellular Ca2+ waves and enhanced AF propensity. In contrast, this mechanism is absent in young atria. In JNK challenged animal models, this is eliminated by JNK2 ablation or CaMKII inhibition.
Conclusions: We have identified JNK2-driven CaMKII activation as a novel mode of kinase crosstalk and a causal factor in atrial arrhythmic remodeling, making JNK2 a compelling new therapeutic target for AF prevention and/or treatment.
- Diastolic SR Calcium Leak
- atrial fibrillation
- c-Jun NH2-terminal kinase
- calcium/calmodulin-dependent protein kinase II
- ryanodine receptor
- Received December 19, 2017.
- Revision received January 8, 2018.
- Accepted January 18, 2018.