Mitochondrial ATP Synthase in Cardiac Biology and Disease

线粒体三磷酸腺苷合成酶是一种多亚单位复合体，催化合成体内90%的三磷酸腺苷 哺乳动物细胞。三磷酸腺苷合成酶也被认为是线粒体通透性的转变 毛孔(MPTP)，是坏死性细胞死亡的主要触发因素。除了短期的药物抑制试验， ATP合成酶的功能在活体心脏中从未被评估过。我们已经创造了第一只老鼠 心肌细胞中缺乏完整的ATP合成酶复合体的模型。为了做到这一点，我们个人 在5周龄时，ATP5L和ATP5J，复杂组装所需的ATP合成酶亚基被删除。到目前为止， 我们对ATP5L KO小鼠进行了分析。因为大多数线粒体ATP合成酶亚基的半衰期 在心肌细胞中超过35天后，复合体的丰度逐渐下降，15%保持在 缺失后12周。KO小鼠一致发展为心力衰竭(HF)并伴有收缩功能降低并死亡 在删除后12-16周之间。对心肌线粒体的分析证实ATP合成率降低 不出所料。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 与对照小鼠相比，KO组小鼠的线粒体组分明显升高。同时进行调查，以了解 作为MPTP的ATP合成酶显示，不是抑制钙离子诱导的MPTP开放，而是缺乏 ATP合成酶使这一事件变得敏感。此外，心肌细胞特异性三磷酸腺苷缺乏的小鼠 合酶在活体心肌缺血/再灌注后显示出更大的-而不是更小的-梗塞。最后，我们 观察到在压力超负荷诱导的心衰期间线粒体中的ATP合成酶水平和活性降低 在野生型小鼠身上。这些结果表明：(A)线粒体ATP合酶的丢失显著地激活了 代谢/能量反应，并释放以前不为人知的机制，促进致命的心衰。 关于后者，我们的初步研究表明，配合物II to I促进反向电子传递(RET) ROS诱导心肌细胞凋亡。(B)我们的研究怀疑三磷酸腺苷合成酶是否也具有 MPTP，更确切地说，这表明它是一个负监管机构。(C)ATP合成酶功能缺陷可能导致 获得性形式的心力衰竭。我们建议进行研究，以了解我们观察到的机制基础并评估 线粒体三磷酸腺苷合成酶功能缺陷在人心衰中的作用。目标1.定义新陈代谢/能量 心肌细胞特异性缺陷小鼠心力衰竭的激活途径和机制 线粒体的ATP合成酶。目的2.明确检测线粒体三磷酸腺苷合成酶是否为 MPTP。目的3.评估线粒体ATP合成酶丰度/功能缺陷在压力中的作用 超负荷引起的小鼠和人心衰。这些研究在研究细胞的功能方面开辟了新的天地 在体心肌细胞线粒体三磷酸腺苷合成酶。可交付成果包括将RET作为 新的HF机制，明确了作为MPTP的ATP合成酶的作用，并描述了 人类心力衰竭中角色缺陷的三磷酸腺苷合成酶功能。

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.