Mitochondrial inner membrane architecture in skeletal muscle pathophysiology

COVID-19是由严重急性呼吸系统综合征冠状病毒2（SARS-1）引起的一种不断升级的大流行病。 CoV-2）。自2019年底爆发以来，它已在全球范围内迅速蔓延，造成60多万人死亡， 2020年8月1日目前没有有效的治疗或预防方法。虽然SARS-CoV-2 它会导致严重的呼吸系统疾病，也会影响其他器官系统，包括肌肉骨骼系统。 其中肌痛、肌肉损失和肌肉功能障碍是常见的后遗症。唐氏综合症（Down Syndrome，DS） 最常见的遗传形式的智力和发育障碍所造成的三倍染色体 21. DS患者还表现出共同发生的病症，包括早发性阿尔茨海默病（AD）、先天性阿尔茨海默病（AD）和阿尔茨海默病（AD）。 心脏缺陷、呼吸和肺阻塞以及肌肉功能障碍。这些潜在的条件 使DS患者特别容易受到COVID-19并发症的影响。产生的分子机制 DS病理学和使DS患者特别容易受到COVID-19的影响仍然难以捉摸。线粒体 在DS和影响神经肌肉系统的其它病理状况中广泛观察到功能障碍 如原发性线粒体肌病、肌肉减少症和AD。在母公司补助金中，我们试图阐明 线粒体结构在维持骨骼肌功能中的基本机制 完整我们确定了线粒体接触位点和嵴组织系统（MICOS）为关键位点 被导致神经肌肉疾病的有毒蛋白质攻击我们还确定了细胞质量控制系统 以及保护免受这种毒性蛋白作用的药理学试剂。在这个补充项目中， 我们将检验SARS-CoV-2感染肌肉细胞破坏线粒体MICOS结构的假设 并加重DS患者的线粒体缺陷。这种假设是 基于强有力的前提：1）ACE 2，SARS-CoV-2进入细胞所需的关键因子，在骨骼肌中表达， 肌细胞; 2）SARS-CoV-2 RNA预计在线粒体中富集; 3）某些SARS-CoV-2 编码的蛋白质与线粒体TOM/TIM复合物相互作用，已知该复合物与MICOS相关; 4)一些SARS-CoV-2编码的蛋白质与细胞质量控制途径相互作用，对于 线粒体生物发生和稳态; 5）我们已经观察到动物肌肉线粒体缺陷 DS模型在目标1中，我们将使用人诱导多能干细胞（iPSC）衍生的肌肉细胞来测试 SARS-CoV-2病毒蛋白对线粒体结构/功能的影响，特别是对MICOS的影响， DS肌肉细胞。在目标2中，我们将使用iPSC衍生的肌肉细胞来测试遗传和免疫治疗的治疗效果。 靶向线粒体质量控制途径的药理学试剂。预计到年底， 我们将提供一个解释DS患者对SARS-CoV-2的易感性的项目，并测试 潜在的针对宿主的药物在保护免受SARS-CoV-2的致病作用。

COVID-19 is an escalating pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2). Since its breakout in late 2019 it has spread rapidly worldwide and killed more than 600,000 people as of August 1st, 2020. There are currently no effective treatment or prevention options. Although SARS-CoV-2 causes severe respiratory disease, it also affects other organ systems, including the musculoskeletal system where myalgias, muscle loss, and muscle dysfunction are common sequelae. Down Syndrome (DS) is the most common genetic form of intellectual and developmental disabilities caused by triplication of chromosome 21. DS patients also exhibit co-occurring conditions including early-onset Alzheimer's disease (AD), congenital heart defects, respiratory and pulmonary obstructions, and muscular dysfunction. These underlying conditions make DS patients particular susceptible to COVID-19 complications. The molecular mechanisms giving rise to DS pathologies and making DS patients particularly vulnerable to COVID-19 remain elusive. Mitochondrial dysfunction is widely observed in DS and other pathological conditions affecting the neuromuscular systems such as primary mitochondrial myopathy, sarcopenia, and AD. In the parent grant, we seek to elucidate fundamental mechanisms underlying the function of mitochondrial structures in maintaining skeletal muscle integrity. We identified mitochondrial contact site and cristae organizing system (MICOS) as a critical site targeted by toxic proteins causing neuromuscular diseases. We also identified cellular quality control systems and pharmacological agents that protect against the action of such toxic proteins. In this Supplement Project, we will test the hypothesis that SARS-CoV-2 infection of muscle cells disrupts mitochondrial MICOS structure and function in normal subjects and exacerbates mitochondrial defects in DS patients. This hypothesis is based on strong premises: 1) ACE2, a key factor needed for cell entry of SARS-CoV-2, is expressed in skeletal muscle cells; 2) SARS-CoV-2 RNA is predicted to be enriched in mitochondria; 3) Certain SARS-CoV-2 encoded proteins interact with the mitochondrial TOM/TIM complex, which is known to associate with MICOS; 4) Some SARS-CoV-2 encoded proteins interact with cellular quality control pathways important for mitochondrial biogenesis and homeostasis; 5) We have observed muscle mitochondrial defects in an animal model of DS. In Aim 1, we will use human induced pluripotent stem cell (iPSC)-derived muscle cells to test the effect of SARS-CoV-2 viral proteins on mitochondrial structure/function in general and MICOS in particular in DS muscle cells. In Aim 2, we will use iPSC-derived muscle cells to test the therapeutic effect of genetic and pharmacological agents targeting mitochondrial quality control pathways. It is anticipated that by the end of the project we will have offered an explanation of the susceptibility of DS patients to SARS-CoV-2 and tested potential host-directed drugs in protecting against the pathogenic effect of SARS-CoV-2.