Aberrant ER-mitochondria communication in human mitochondrial disease

线粒体疾病是由呼吸链/氧化-磷酸化系统(OxPhos)缺陷引起的一组疾病，是一组重要的病理学，具有挑战性 并进行治疗，因为它们在每个层面上都是最不同的人类疾病之一：临床、生化、 而且是遗传的。线粒体受双重遗传控制，依赖于核DNA(NDNA)和 线粒体DNA(MtDNA)由两个基因组编码的基因的致病突变引起 线粒体疾病，其中许多是神经退行性疾病，通常具有破坏性和 最终是致命的。线粒体DNA基因的突变会影响OxPhos系统的结构亚单位，而突变 在nDNA中，基因数量更多，种类更多，因为它们不仅编码大量的OxPhos亚单位 也是OxPhos机制正确合成、组装和运作所需的因素。 我们最近发现，在线粒体疾病患者的细胞中，有明显的 线粒体和线粒体之间的身体和生物化学方面的亲密交流中断 内质网(ER)位于“线粒体相关ER膜(MAM)”。MAM是一个中心位置 维持细胞胆固醇、磷脂和钙的稳态，以及调节线粒体 生物能量学和动力学(细胞器融合、分裂和定位)。基于这一发现，我们假设 氧化能量代谢的减少会扰乱内质网-线粒体的通讯，并严重 对细胞存活率的影响远远超出了ATP产量减少的影响。 因此，这项申请的目标--以及我们的具体目标--有三个：(1)推断基因和 缺乏OxPhos影响MAM(“表型景观”)的生化环境，通过 分析来自nDNA和mtDNA已知突变导致OxPhos缺乏症患者的细胞，并通过 用特定的OxPhos毒素扰乱生物能量学；(2)深入了解这一现象的机制 发生，使用有偏见的(即有针对性的)和无偏见的方法来确定影响OxPhos的相关因素 内质网-线粒体连接；以及(3)确定我们是否可以利用遗传或药物 用基因折衷的生物能量学改善细胞内质网-线粒体通讯的方法， 从而揭示了潜在的OxPhos潜力(即提高了OxPhos的产量和效率)，并提高了 生物能量输出，即使在具有高突变负荷的细胞中也是如此。 我们发现了一种“OxPhos-MAM连接”，揭示了迄今为止未知的致病作用。 线粒体疾病中细胞器间通讯的改变。反过来，这又开辟了一种新的方式 对线粒体疾病发病机制和治疗的思考。一种基于 修复内质网-线粒体连接以使MAM功能重新正常化很可能是一种普遍的 线粒体疾病的数量。

Mitochondrial disease, defined as a group of disorders due to defects in the respiratory chain/oxidative-phosphorylation system (OxPhos), comprises an important group of pathologies that are challenging to study and treat, as they are among the most heterogeneous human conditions at every level: clinical, biochemical, and genetic. Mitochondria are under dual genetic control, dependent on both nuclear DNA (nDNA) and mitochondrial DNA (mtDNA). Pathogenic mutations in genes encoded by both genomes give rise to mitochondrial disease, many of which are neurodegenerative disorders that typically are both devastating and ultimately fatal. Mutations in mtDNA genes affect structural subunits of the OxPhos system, whereas mutations in nDNA genes are more numerous and diverse, as they encode not only a large number of OxPhos subunits but also factors needed for the proper synthesis, assembly, and functioning of the OxPhos machinery. We recently discovered that in cells from patients with mitochondrial disease there is a significant disruption in the intimate communication, both physical and biochemical, between mitochondria and endoplasmic reticulum (ER) at "mitochondria-associated ER membranes (MAM)". MAM is a central locus for maintaining cellular cholesterol, phospholipid, and calcium homeostasis, as well as regulating mitochondrial bioenergetics and dynamics (organellar fusion, fission, and positioning). Based on this finding, we hypothesize that reductions in oxidative energy metabolism can disrupt ER-mitochondrial communication, with serious consequences for cell survivability that go well beyond that of reduced ATP output. The objectives of this application - and our Specific Aims - are thus threefold: (1) to deduce the genetic and biochemical circumstances under which OxPhos deficits affect MAM (the "phenotypic landscape"), by analyzing cells from patients with known mutations in nDNA and mtDNA causing OxPhos deficiency, and by perturbing bioenergetics with specific OxPhos toxins; (2) to gain insight into the mechanism by which this occurs, using both biased (i.e. targeted) and unbiased approaches to identify OxPhos-related factors that affect ER-mitochondrial connectivity; and (3) to determine if we can use either genetic or pharmacological approaches to improve ER-mitochondrial communication in cells with genetically-compromised bioenergetics, thereby revealing "latent" OxPhos potential (i.e. improved OxPhos output and efficiency) and increasing bioenergetic output, even in cells with a high mutation load. Our discovery of an "OxPhos-MAM connection" has revealed a hitherto unknown pathogenetic role of altered inter-organellar communication in mitochondrial disease. In turn, this has opened up a new way of thinking about the pathogenesis and treatment of mitochondrial disease. A therapeutic strategy based on "fixing" ER-mitochondrial connectivity to re-normalize MAM function will likely be generalizable to a large number of mitochondrial disorders.