Relevance of mitochondrial calcium uniporter for mitochondrial myopathy

翻译后摘要：该项目探讨了两个基本领域的交叉点：细胞（mal）适应， 原发性线粒体功能障碍和线粒体Ca 2+单向转运体（MCUC）的生物学。在人类中， 原发性线粒体疾病是由核或线粒体编码的DNA突变引起的，或由 药理学试剂或毒素。骨骼肌是受影响最严重的器官之一。鼠标 线粒体肌病（MM）模型显示，能量缺乏本身不是导致线粒体肌病的主要因素。 相反，线粒体功能障碍引发了适应性和适应不良的进展， 改变，例如，代谢和蛋白质稳态，也激活内质网（ER）应激和 综合应激反应（ISR）;结果是肌肉萎缩、虚弱和运动能力下降。 已经研究了ISR以外的主要细胞质信号传导途径，但发现不能完全解释MM。 线粒体内的过程是否可以影响MM进展仅被狭义地考虑。 已发表的数据和我们的初步数据记录了MCUC丰度的增加， MM和其他来源的肌病中线粒体Ca 2+摄取增加。的可能性 线粒体Ca 2+摄取对病理学的贡献仅在MCUC的能力背景下被考虑， 引起线粒体通透性转换孔（mPTP）的持续开放，这可以触发细胞 死亡然而，我们的初步数据表明，MCUC在MM中发挥有益作用的假设， 扩大功能失调的肌肉线粒体的氧化磷酸化能力， 侦察监视器该假设将在两个特定目的中通过在两种MM模型（小鼠）中消耗MCUC进行检验 骨骼肌中PiC耗尽; Frataxin全身缺失的小鼠），用于体内和离体 问题研究我们还将使用先进的成像技术和遗传传感器来评估新陈代谢， 生物能量学和氧化还原，以及钙，以区室化的方式，包括在ER-线粒体 界面，在细胞急性耗尽MCUC。我们还将使用复杂的方法来评估蛋白质 翻译，因为这是ISR的一个关键特征，可以影响肌肉质量。目标1将检验假设 线粒体Ca 2+摄取在线粒体功能障碍的早期阶段改善能量学。 目的2将确定MCUC如何促进线粒体功能障碍诱导的ER应激和ISR 以及对细胞活力和肌肉质量的影响。目的3将检验MCUC的调节 通过MICU 3使线粒体易受持续mPTP开放的影响，使得MCUC成为一个 在线粒体功能障碍的后期阶段对骨骼肌的易感性。这些研究有望揭示 MCUC在骨骼肌对线粒体功能障碍的适应性反应中的新作用， 在调节肌肉质量的肌病，并广泛地说，提供新的见解，以调节主要的 在不同的肌病和许多其他应激条件下激活的应激信号通路。 .

Abstract: This project explores the intersection of two fundamental areas: cellular (mal)adaptation to primary mitochondrial dysfunction and the biology of the mitochondrial Ca2+ uniporter (MCUC). In humans, primary mitochondrial disease arises from mutations in nuclear- or mitochondrial-encoded DNA, or from pharmacological agents or toxins. Skeletal muscle is among the most severely affected organs. Mouse models of mitochondrial myopathy (MM) show that energy deficit, per se, is not the major factor for pathology, but, rather, that mitochondrial dysfunction initiate a progression of adaptive and maladaptive changes in, e.g., metabolism and proteostasis, and also activates endoplasmic reticulum (ER) stress and the Integrated Stress Response (ISR); the result is muscle atrophy, weakness, and diminished exercise capacity. Major cytoplasmic signaling pathways beyond the ISR have been investigated but found to not fully explain MM. Whether processes within mitochondria can impact MM progression has only been narrowly considered. Published data and our preliminary data document an increased abundance of the MCUC and increased mitochondrial Ca2+ uptake in MM and myopathies of other origins. The possibility that mitochondrial Ca2+ uptake contributes to pathology has only been considered in the context of MCUC's ability to cause a sustained opening of the mitochondrial permeability transition pore (mPTP), which can trigger cell death. Yet, our preliminary data suggest the hypothesis that the MCUC serves a beneficial role in MM, by expanding the oxidative phosphorylation capacity of dysfunctional muscle mitochondrial, and blunting the ISR. This hypothesis will be tested in two Specific Aims, by depletion MCUC in two models of MM (mice with depletion of PiC in skeletal muscle; mice with whole-body loss of Frataxin), for in vivo and ex vivo studies. We will also use advanced imaging techniques and genetic sensors to evaluate metabolism, bioenergetics and redox, and calcium, in a compartmentalized manner, including at the ER-mitochondria interface, in cells acutely depleted of MCUC. We will also use sophisticated methods to evaluate protein translation, since this is a key feature of the ISR that can influence muscle mass. Aim 1 will test the hypothesis that mitochondrial Ca2+ uptake improves energetics during the early phase of mitochondrial dysfunction. Aim 2 will determine how MCUC contributes to mitochondrial dysfunction-induced ER stress and the ISR and consequences on cell viability and muscle mass. Aim 3 will test the hypothesis that regulation of MCUC by MICU3 renders mitochondria vulnerable to sustained mPTP opening such that the MCUC becomes a liability for skeletal muscle at later phases of mitochondrial dysfunction. These studies are expected to reveal a novel role for MCUC in the (mal)adaptive response of skeletal muscle to mitochondrial dysfunction and in regulating muscle mass in myopathy, and, broadly, to provide new insight into the regulation of major stress signaling pathways that are activated in different myopathies, and many other stress conditions. .