Project 4: Mitochondrial Uniporter Regulation can Limit Ischemic Damage

总结 线粒体钙（mCa 2+）超载是心肌梗死（MI）和心力衰竭（HF）的中心事件， 导致代谢紊乱，线粒体通透性转换孔（MPTP）激活，遗传 重新编程和由于坏死导致的细胞损失。线粒体钙单向转运体通道（mtCU）是线粒体的钙转运体。 mCa 2+摄取的主要机制，位于线粒体内膜（IMM）， 是激活线粒体能量通路以支持应激（战斗或逃跑）期间的收缩性所必需的 响应）。mtCU是一种多蛋白高分子量通道，大小约为400-800 kD，含有成孔蛋白， 支架和调节组分。鉴于在新陈代谢和细胞死亡中的关键作用， 有兴趣了解调节mCa 2+摄取的机制。我们最近报道了条件遗传学 MCU（mtCU的孔形成亚基）的消融在体内缺血模型中具有心脏保护作用， 再灌注（IR）损伤，提供了翻译潜力的证据。最近一个MCU的基因参数， CCDC 109 b（MCUB）被鉴定为单向转运蛋白的组分，理论上可以负调节 mCa 2+摄取。然而，没有遗传学或体内研究调查了这个基因及其作用机制 仍然未知。鉴于破译单向转运体通道调节的治疗价值，该提议将 检查MCUB的分子功能及其对心脏生理学中mCa 2+动力学的贡献， 使用体外和体内遗传获得和丧失功能的方法治疗疾病。我们假设MCUB是 线粒体钙摄取的应激响应调节剂，通过调节组合物（成员和 化学计量），并且MCUB的治疗性操作将减少致病性mCa 2+摄取， 发生在IR损伤和心力衰竭（HF）中。

SUMMARY Mitochondrial calcium (mCa2+) overload is a central event in myocardial infarction (MI) and heart failure (HF), causing metabolic derangement, mitochondrial permeability transition pore (MPTP) activation, genetic reprograming and loss of cells due to necrosis. The Mitochondrial Calcium Uniporter Channel (mtCU) is the primary mechanism for mCa2+ uptake, located at the inner mitochondrial membrane (IMM), and physiologically is required for activation of mitochondrial energetic pathways to support contractility during stress (fight-or-flight response). The mtCU is a multiprotein high-MW channel, ~400-800 kD in size, containing pore-forming, scaffold and regulatory components. Given the critical roles in metabolism and cell death it is of great scientific interest to understand the mechanisms regulating mCa2+ uptake. We recently reported that conditional genetic ablation of MCU, the pore forming subunit of the mtCU, is cardioprotective in an in vivo model of ischemia- reperfusion (IR) injury, providing evidence of translational potential. Recently a gene paralog of MCU, CCDC109b (MCUB), was identified as a component of the uniporter and is theorized to negatively regulate mCa2+ uptake. However, no genetic or in vivo studies have investigated this gene and it's mechanism of action remains unknown. Given the therapeutic value of deciphering uniporter channel regulation, this proposal will examine the molecular function of MCUB, and its contribution to mCa2+ dynamics in cardiac physiology and disease using in vitro and in vivo genetic gain- and loss-of-function approaches. We hypothesize that MCUB is a stress-responsive regulator of mitochondrial calcium uptake by modulating the composition (members and stoichiometry) of the mtCU and that therapeutic manipulation of MCUB will reduce pathogenic mCa2+ uptake, as occurs in IR injury and heart failure (HF).