Mechanism of age-dependent neuromuscular degeneration caused by protein misfolding on the inner mitochondrial membrane

线粒体内膜蛋白质错误折叠引起的年龄依赖性神经肌肉变性的机制

基本信息

批准号：
9980255
负责人：
Liam Patrick Coyne
金额：
$ 5.05万
依托单位：
UPSTATE MEDICAL UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-30 至 2022-08-29
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9980255
关键词：
ATP Synthesis Pathway Acute Address Adenine Nucleotide Translocase Affect Aging Alleles Ataxia Calcium Signaling Cell Death Cell physiology Cells Chronic Chronic progressive external ophthalmoplegia Clinical Complex Cytosol Defect Degenerative Disorder Degradation Pathway Disease Exhibits Failure Histologic Histology Homeostasis Immunohistochemistry Inherited Inner mitochondrial membrane Intervention Knock-in Knock-in Mouse Mammals Mass Spectrum Analysis Measures Membrane Membrane Potentials Mitochondria Mitochondrial Membrane Protein Mitochondrial Myopathies Mitochondrial Proteins Modeling Mus Muscle Muscle Mitochondria Muscle Weakness Muscle function Mutation Nerve Degeneration Neurodegenerative Disorders Neuromuscular Diseases Organelles Organism Orthologous Gene Oxidation-Reduction Oxidative Phosphorylation Paralysed Paraplegia Parkinson Disease Pathogenicity Pathology Pathway interactions Peptide Hydrolases Phenotype Physiological Process Production Protein Import Protein Precursors Proteins Proteomics Quality Control Respiration Role Skeletal Muscle Spastic Paraplegia Spinocerebellar Ataxias Stress Study models Syndrome System Testing Time Transmission Electron Microscopy Validation Variant Western Blotting Yeasts age related base density disease-causing mutation effective therapy exercise intolerance in vivo insight misfolded protein mitochondrial membrane mouse model muscle degeneration mutant neuromuscular novel prevent protein aggregation protein degradation protein misfolding proteostasis respiratory response skeletal muscle weakness spasticity tool

项目摘要

PROJECT SUMMARY Mitochondria are essential organelles responsible for many cellular processes including energy production through oxidative phosphorylation (OXPHOS), calcium signaling, redox homeostasis, and cell death. Many of these functions are executed by a densely packed network of proteins in the inner mitochondrial membrane (IMM). As such, mitochondrial functions depend on protein homeostasis (proteostasis) in the IMM. IMM proteostasis is maintained by an extensive protein quality control system composed, in part, of IMM proteases that degrade misfolded proteins. Persistent IMM protein misfolding is speculated to cause a growing number of age-dependent neurodegenerative and neuromuscular degenerative diseases. For example, mutations in IMM proteases cause Parkinson's disease, spinocerebellar ataxia, spastic ataxia syndrome, spastic paraplegia, and other neurodegenerative diseases. Does a failure to degrade misfolded IMM proteins cause these diseases? This is unknown. In addition, misfolded variants of the ADP/ATP exchanger in the IMM, Ant1, cause autosomal dominant Progressive External Ophthalmoplegia and a mitochondrial myopathy. We used one such misfolded Ant1 variant to dissect the cellular consequences of IMM protein misfolding in yeast. Unexpectedly, IMM protein misfolding does not kill yeast cells by affecting essential mitochondrial functions in the IMM, but instead by disrupting mitochondrial protein import causing the toxic accumulation of mitochondrial precursor proteins in the cytosol. This novel mechanism was termed mitochondrial precursor overaccumulation stress (mPOS). It is not known if mPOS occurs in higher organisms, or if it can contribute to disease. Moreover, despite the significant clinical implications, the physiological consequences of IMM protein misfolding are poorly understood. To address these issues, we generated a novel knock-in (KI) mouse model expressing a pathogenic misfolded variant of Ant1. A fraction of KI mice undergo drastic neurodegeneration culminating in paralysis, thus confirming the pathogenic potential of IMM protein misfolding and providing a tool for in vivo mechanistic studies. Non-paralyzed KI mice exhibit exercise intolerance and reduced skeletal muscle mitochondrial respiration in skeletal muscle. This raises the possibility that IMM protein misfolding causes damage to specific components in the OXPHOS pathway leading to muscle weakness. We test this hypothesis in Aim 1. In addition to OXPHOS deficiency, cytosolic protein degradation pathways are activated in skeletal muscle of “asymptomatic” KI mice. The activation of cytosolic protein degradation pathways suggests that cytosolic proteostasis is challenged, possibly via mPOS. Therefore, in Aim 2, we test the hypothesis that IMM protein misfolding induces mPOS in KI mouse muscle to cause muscle weakness. The mechanism(s) revealed in this proposal will be important for understanding the role of IMM protein misfolding in Ant1-induced pathologies and neuromuscular degenerative diseases alike. In long term, interventions alleviating the identified mechanism(s) may be effective treatments for these diseases, of which there are currently none. !

项目概要线粒体是负责许多细胞过程（包括能量产生）的重要细胞器通过氧化磷酸化 (OXPHOS)、钙信号传导、氧化还原稳态和细胞死亡。这些功能是由线粒体内膜中密集的蛋白质网络执行的 (IMM) 因此，线粒体功能取决于 IMM 中的蛋白质稳态（蛋白质稳态）。蛋白质稳态由部分由 IMM 蛋白酶组成的广泛蛋白质质量控制系统维持据推测，持续的 IMM 蛋白错误折叠会导致错误折叠蛋白的数量不断增加。年龄依赖性神经退行性和神经肌肉退行性疾病，例如 IMM 突变。蛋白酶导致帕金森病、脊髓小脑性共济失调、痉挛性共济失调综合征、痉挛性截瘫和其他神经退行性疾病是否会导致这些疾病？此外，IMM 中 ADP/ATP 交换器 Ant1 的错误折叠变体也是未知的。常染色体显性遗传进行性外眼肌麻痹和线粒体肌病我们使用了这样的一种。错误折叠的 Ant1 变体剖析了酵母中 IMM 蛋白错误折叠的细胞后果。 IMM 蛋白错误折叠不会通过影响 IMM 中重要的线粒体功能来杀死酵母细胞，但相反，通过破坏线粒体蛋白质的输入，导致线粒体前体的毒性积累这种新机制被称为线粒体前体过度积累应激。 (mPOS)。目前尚不清楚 mPOS 是否发生在高等生物体中，或者是否会导致疾病。尽管具有重要的临床意义，但 IMM 蛋白错误折叠的生理后果是为了解决这些问题，我们生成了一种表达 a 的新型敲入 (KI) 小鼠模型。 Ant1 的致病性错误折叠变异。部分 KI 小鼠经历剧烈的神经退行性变，最终导致麻痹，从而证实了IMM蛋白错误折叠的致病潜力，并为体内研究提供了工具机制研究。非瘫痪 KI 小鼠表现出运动不耐受和骨骼肌减少。这增加了 IMM 蛋白错误折叠导致的可能性。 OXPHOS 通路中特定成分的损伤导致肌肉无力，我们对此进行了测试。目标 1 中的假设。除了 OXPHOS 缺乏之外，胞浆蛋白降解途径在 “无症状”KI 小鼠的骨骼肌细胞质蛋白降解途径的激活表明。细胞质蛋白质稳态受到挑战，可能是通过 mPOS 因此，在目标 2 中，我们检验以下假设： IMM 蛋白错误折叠诱导 KI 小鼠肌肉中的 mPOS 导致肌肉无力。该提案中揭示的内容对于理解 IMM 蛋白错误折叠在 Ant1 诱导的中的作用非常重要从长远来看，干预措施可以缓解病理学和神经肌肉退行性疾病。已确定的机制可能是治疗这些疾病的有效方法，但目前还没有这种方法。！