Aims Diastolic Ca release (DCR) from sarcoplasmic reticulum (SR) Ca release channel ryanodine receptor (RyR2) has been linked to multiple cardiac pathologies, but its exact role in shaping divergent cardiac pathologies remains unclear. We hypothesize that the SR-mitochondria interplay contributes to disease phenotypes by shaping Ca signalling. Methods and results A genetic model of catecholaminergic polymorphic ventricular tachycardia (CPVT2 model of CASQ2 knockout) and a pre-diabetic cardiomyopathy model of fructose-fed mice (FFD), both marked by DCR, are employed in this study. Mitochondria Ca (mCa) is modulated by pharmacologically targeting mitochondria Ca uniporter (MCU) or permeability transition pore (mPTP), mCa uptake, and extrusion mechanisms, respectively. An MCU activator abolished Ca waves in CPVT2 but exacerbated waves in FFD cells. Mechanistically this is ascribed to mitochondria’s function as a Ca buffer or source of reactive oxygen species (mtROS) to exacerbate RyR2 functionality, respectively. Enhancing mCa uptake reduced and elevated mtROS production in CPVT2 and FFD, respectively. In CPVT2, mitochondria took up more Ca in permeabilized cells, and had higher level of mCa content in intact cells vs. FFD. Conditional ablation of MCU in the CPVT2 model caused lethality and cardiac remodelling, but reduced arrhythmias in the FFD model. In parallel, CPVT2 mitochondria also employ up-regulated mPTP-mediated Ca efflux to avoid mCa overload, as seen by elevated incidence of MitoWinks (an indicator of mPTP-mediated Ca efflux) vs. FFD. Both pharmacological and genetic inhibition of mPTP promoted mtROS production and exacerbation of myocyte Ca handling in CPVT2. Further, genetic inhibition of mPTP exacerbated arrhythmias in CPVT2. Conclusion In contrast to FFD, which is more susceptible to mtROS-dependent RyR2 leak, in CPVT2 mitochondria buffer SR-derived DCR to mitigate Ca-dependent pathological remodelling and rely on mPTP-mediated Ca efflux to avoid mCa overload. SR-mitochondria interplay contributes to the divergent pathologies by disparately shaping intracellular Ca signalling.

中文翻译：

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SR-线粒体串扰塑造 Ca 信号传导，影响以细胞内 Ca 释放失调为标志的疾病模型的病理表型


肌浆网 (SR) Ca 释放通道兰尼碱受体 (RyR2) 的舒张期 Ca 释放 (DCR) 与多种心脏病相关，但其在形成不同心脏病中的确切作用仍不清楚。我们假设 SR-线粒体相互作用通过塑造 Ca 信号传导而导致疾病表型。方法和结果本研究采用儿茶酚胺能多形性室性心动过速遗传模型（CASQ2敲除的CPVT2模型）和果糖喂养小鼠糖尿病前期心肌病模型（FFD），两者均以DCR标记。线粒体 Ca (mCa) 分别通过药理学靶向线粒体 Ca 单向转运蛋白 (MCU) 或通透性转换孔 (mPTP)、mCa 摄取和挤出机制进行调节。 MCU 激活剂消除了 CPVT2 中的 Ca 波，但加剧了 FFD 细胞中的 Ca 波。从机制上讲，这归因于线粒体作为 Ca 缓冲剂或活性氧 (mtROS) 来源的功能，分别加剧了 RyR2 的功能。增强 mCa 摄取可分别减少和增加 CPVT2 和 FFD 中 mtROS 的产生。在 CPVT2 中，线粒体在透化细胞中吸收更多的 Ca，并且与 FFD 相比，完整细胞中的 mCa 含量水平更高。在 CPVT2 模型中条件性消融 MCU 会导致死亡和心脏重塑，但在 FFD 模型中会减少心律失常。与此同时，CPVT2 线粒体还利用上调的 mPTP 介导的 Ca 流出来避免 mCa 过载，如 MitoWinks（mPTP 介导的 Ca 流出的指标）相对于 FFD 的发生率升高所示。 mPTP 的药理和遗传抑制促进了 CPVT2 中 mtROS 的产生并加剧了肌细胞 Ca 的处理。此外，mPTP 的基因抑制加剧了 CPVT2 的心律失常。 结论 与更容易受到 mtROS 依赖性 RyR2 泄漏影响的 FFD 相比，CPVT2 线粒体缓冲液 SR 衍生的 DCR 可减轻 Ca 依赖性病理重塑，并依靠 mPTP 介导的 Ca 外流来避免 mCa 过载。 SR-线粒体相互作用通过不同地塑造细胞内 Ca 信号传导而导致不同的病理学。