Mitochondrial ATP Synthase in Cardiac Biology and Disease

线粒体ATP合酶是一种多亚基复合物，催化线粒体中>90%的ATP的合成。 哺乳动物细胞ATP合酶也被假设为线粒体通透性转换的功能 孔（mPTP），坏死细胞死亡的主要触发因素。除了短期药物抑制剂实验外， ATP合酶的功能从未在体内心脏中进行过评估。我们创造了第一只老鼠 心肌细胞中整个ATP合酶复合物缺乏的模型。为了做到这一点，我们每个人 在5周龄时缺失ATP 5L和ATP 5 J，ATP合酶亚基是复合物组装所需的。到目前为止， 我们分析了ATP 5L KO小鼠。因为大多数线粒体ATP合酶亚基的半衰期 在心肌细胞中，超过35天，复合物的丰度逐渐下降， 删除后12周。KO小鼠一致发生心力衰竭（HF），收缩功能降低并死亡 在删除后12-16周之间。心肌线粒体分析证实ATP合成速率降低 果然然而，出乎意料的是，整个心脏裂解物中的ATP浓度，以及细胞质和 与对照组相比，KO小鼠的线粒体组分升高。同时调查 ATP合酶作为mPTP显示，缺乏ATP合酶并不能抑制Ca ~（2+）诱导的mPTP开放， ATP合成酶使这一事件敏感。此外，心肌细胞特异性ATP缺乏的小鼠 合成酶在体内心肌缺血/再灌注后表现出更大而不是更小的梗死。最后我们 观察到在压力超负荷诱导的HF期间线粒体中ATP合酶水平和活性降低， 在野生型小鼠中。这些结果表明：（a）线粒体ATP合酶的丧失激活了显著的 代谢/能量反应，并释放以前未被认识到的促进致命HF的机制。 关于后者，我们的初步研究暗示复合物II至I的反向电子传递（RET）促进了 ROS诱导的心肌细胞凋亡。(b)我们的研究怀疑ATP合酶也起着 mPTP，而不是建议它是一个负调节器。(c)ATP合成酶功能缺陷可能有助于 获得性HF。我们建议进行研究，以了解我们观察的机械基础，并评估 线粒体ATP合酶功能缺陷在人HF中的作用。目标1。定义代谢/能量 心肌细胞特异性缺陷小鼠中激活的通路和导致HF的机制 线粒体ATP合酶的基因目标2.为了明确地测试线粒体ATP合酶是否是 mPTP。目标3。评估线粒体ATP合酶丰度/功能缺陷在压力中的作用 在小鼠和人HF中的超负荷诱导的HF。这些研究在研究细胞的功能方面开辟了新的领域。 心肌细胞线粒体ATP合成酶的研究。可评估项目包括可再生能源技术评估， 新的HF机制，ATP合酶作为mPTP的作用的确定性测定，以及 ATP合酶功能缺陷的作用。

The mitochondrial ATP synthase is a multi-subunit complex that catalyzes the synthesis of >90% of ATP in mammalian cells. The ATP synthase is also hypothesized to function as the mitochondrial permeability transition pore (mPTP), a major trigger for necrotic cell death. Except for short-term drug inhibitor experiments, the functions of the ATP synthase have never been assessed in the heart in vivo. We have created the first mouse models deficient in the entire ATP synthase complex in cardiomyocytes. To accomplish this, we individually deleted at 5 weeks of age ATP5L and ATP5J, ATP synthase subunits required for complex assembly. Thus far, we have analyzed the ATP5L KO mice. Because the half-lives of most mitochondrial ATP synthase subunits exceed 35 days in cardiomyocytes, the abundance of the complex decreased gradually with 15% remaining at 12 weeks post-deletion. KO mice uniformly developed heart failure (HF) with reduced systolic function and died between 12-16 weeks post-deletion. Analysis of cardiac mitochondria confirmed reduced ATP synthesis rates as expected. Unexpectedly, however, ATP concentrations in whole heart lysates, as well as in cytoplasmic and mitochondrial fractions, were elevated in KO, compared with control, mice. Parallel investigations into the role of the ATP synthase as the mPTP revealed that, rather than inhibiting Ca2+-induced mPTP opening, deficiency of the ATP synthase sensitized this event. Moreover, mice with cardiomyocyte-specific deficiency of the ATP synthase exhibited larger – not smaller – infarcts following myocardial ischemia/reperfusion in vivo. Finally, we observed that ATP synthase levels and activity in mitochondria decrease during pressure overload-induced HF in wild type mice. These results suggest: (a) Loss of the mitochondrial ATP synthase activates marked metabolic/energetic responses and unleashes previously unrecognized mechanisms that promote lethal HF. Regarding the latter, our preliminary studies implicate Complex II to I reverse electron transport (RET) promoting ROS-induced cardiomyocyte apoptosis. (b) Our studies cast doubt that the ATP synthase also functions as the mPTP and rather suggest that it is a negative regulator. (c) Deficient ATP synthase function may contribute to acquired forms of HF. We propose studies to understand the mechanistic basis of our observations and to assess the role deficient mitochondrial ATP synthase function in human HF. Aim 1. To define metabolic/energetic pathways that are activated and mechanisms that contribute to HF in mice with cardiomyocyte-specific deficiency of the mitochondrial ATP synthase. Aim 2. To test definitively whether the mitochondrial ATP synthase is the mPTP. Aim 3. To assess the role of deficient mitochondrial ATP synthase abundance/function in pressure overload-induced HF in mice and in human HF. These studies break new ground in investigating functions of the mitochondrial ATP synthase in cardiomyocytes in vivo. Deliverables include the assessment of RET as a novel HF mechanism, a definitive determination of the role of the ATP synthase as the mPTP, and a delineation of the role deficient ATP synthase function in human HF.