Metabolic Impact and Mechanism of Enhanced Mitochondrial Calcium Uptake in Mitochondrial Cardiomyopathies

项目摘要 由线粒体氧化磷酸化组分突变引起的疾病可以是 这是毁灭性的，因为线粒体对能量合成至关重要。这些疾病主要发生在婴儿身上 和儿童，患病率为1/5000。虽然几乎任何器官都可能受到影响，但心脏经常 因为心脏功能需要很高的能量。这些线粒体 心肌病的预后特别糟糕，死亡率增加了近三倍， 与没有心脏受累的儿童相比，没有特殊的治疗方法。在连接心脏 由于钙信号对线粒体代谢的作用，钙信号可能是病理过程的中心。钙 流入线粒体可以有效地刺激ATP合成。在本申请的最初阶段，我们 确定了一种调节机制，通过该机制，电子传递链复合物I内的功能障碍 引起线粒体钙单向转运体通道活性的代偿性增加， 合成.在正常生理过程中，复合物I通过与蛋白质相互作用促进单向转运体降解。 单向转运体，一种我们称之为复合物I诱导的蛋白质周转（CLIPT）的机制。在复合体I功能障碍期间， 与单向转运蛋白的相互作用被抑制，从而防止降解并导致功能性转运蛋白的积累。 渠道这种机制是广泛存在的，在果蝇、小鼠和人类中都有发现。此外，虽然 抑制单向转运蛋白导致复合物I缺陷动物的早期死亡，增强单向转运蛋白的稳定性 拯救生存和功能。在本项目期间，我们提出以下三个目标，以进一步研究这一点 途径，并确定其是否可以用于潜在的治疗益处。我们专注于 线粒体一碳（1C）代谢，线粒体抗氧化剂种类（NAPDH）的生产者， 因为该途径在线粒体心肌病中显著上调。在第一个目标中，我们将 检查腺嘌呤二核苷酸（NAD+/NADP+）是否调节单向转运蛋白，以及钙是否调节关键的1C 代谢酶在第二个目标中，我们将确定线粒体中的单向转运体活性是否 心肌病超越ATP合成，影响NADPH生物学，影响氧化还原平衡和一碳 新陈代谢.在第三个目标，我们将测试是否操纵的部分uniporter的相互作用 与复合物I，单向转运体N-末端结构域（NTD），可以在小鼠模型中作为潜在的 线粒体心肌病的治疗。

PROJECT SUMMARY Diseases that arise from mutations in components of mitochondrial oxidative phosphorylation can be devastating, as mitochondria are crucial for energy synthesis. These diseases occur predominantly in infants and children, with a prevalence of 1 in 5000. Though virtually any organ can be affected, the heart is frequently involved, because cardiac function has such high energy requirements. These mitochondrial cardiomyopathies have a particularly grim prognosis, with mortality rates increased nearly three-fold compared to children without cardiac involvement, and no specific therapies available. In linking cardiac function to mitochondrial metabolism, calcium signaling may be central to the pathological process. Calcium influx into the mitochondria can potently stimulate ATP synthesis. In the initial period of this application, we identified a regulatory mechanism by which dysfunction within Complex I of the electron transport chain causes a compensatory increase in activity of the mitochondrial calcium uniporter channel, preserving ATP synthesis. During normal physiology, Complex I promotes uniporter degradation via an interaction with the uniporter, a mechanism we term Complex I-induced protein turnover (CLIPT). During Complex I dysfunction, interaction with the uniporter is inhibited, preventing degradation and leading to a build-up in functional channels. This mechanism is widespread and was seen in fruit flies, mice, and humans. Moreover, while inhibiting the uniporter led to early demise in Complex I-deficient animals, enhancing uniporter stability rescued survival and function. In this project period, we propose the following three aims to further study this pathway and determine whether it can be exploited for potential therapeutic benefit. We focus on mitochondrial one-carbon (1C) metabolism, a producer of mitochondrial antioxidant species (NAPDH), because this pathway is substantially upregulated in mitochondrial cardiomyopathies. In the first aim, we will examine if adenine dinucleotides (NAD+/NADP+) regulate the uniporter, and if calcium regulates critical 1C metabolism enzymes. In the second aim, we will establish whether uniporter activity in mitochondrial cardiomyopathies extends beyond ATP synthesis to NADPH biology, affecting redox balance and one-carbon metabolism. In the third aim, we will test whether manipulation of the portion of the uniporter that interacts with Complex I, the uniporter N-terminal domain (NTD), can be exploited in mouse models as a potential therapy for mitochondrial cardiomyopathies.