Molecular Mechanisms of Mitochondrial Biogenesis

项目摘要 线粒体是内共生衍生的双膜结合细胞器， 通过氧化呼吸获得能量。线粒体还充当细胞代谢的主要枢纽， 参与许多重要途径，包括细胞信号传导、先天免疫反应和细胞凋亡。 线粒体的功能障碍与衰老和许多疾病有关，并且是衰老的潜在致病因素。 神经退行性疾病> 1，000种线粒体蛋白质中的大多数由核基因组编码， 因此在被合成后不久作为前体在胞质核糖体上从胞质中输入。因此，在本发明中， 线粒体蛋白质输入是线粒体生物发生和功能维持所需的重要过程 线粒体输入过程主要由两个普遍保守的膜复合物介导， 外膜易位酶（TOM）复合物和内膜易位酶（TIM）复合物。 TOM复合物介导前体蛋白跨线粒体外膜的初始易位 TIM复合物进一步将前体蛋白易位穿过内部线粒体 膜的TIM复合物还负责许多整合的膜蛋白整合到细胞膜上。 内膜目前，人们对TOM和TIM复合物如何介导这些变化知之甚少。 易位过程在目前的建议中，我们的目标是解决以下悬而未决的核心问题： TOM和TIM复合物的蛋白质输入机制，使用结构，生物化学和生物物理 方法。这些问题包括易位酶复合体如何特异性地识别它们的客户 蛋白质，它们如何形成蛋白质在膜中移位的路径，分子相互作用是什么 和驱动蛋白质易位的力，以及易位酶复合物如何被调节。特别是要 进行几次冷冻电子显微镜（cryo-EM）研究，以观察不同组织中的易位酶复合物 功能状态，包括衬底参与状态，并深入了解其机制，为衬底 接合和构象变化。这些研究的结果将从根本上推动我们的 了解线粒体生物学，并提供新的见解，以开发新的方法来治疗 神经系统相关疾病，如神经退行性疾病。

PROJECT SUMMARY Mitochondria are endosymbiotically-derived double membrane-bound organelles which provide cells with energy via oxidative respiration. Mitochondria also serve as a major hub for cellular metabolism and are involved in numerous vital pathways, including cell signaling, innate immune response, and apoptosis. Dysfunction of mitochondria is implicated in aging and many diseases and is a potential causative factor in neurodegenerative diseases. Most of >1,000 mitochondrial proteins are encoded by the nuclear genome and thus are imported from the cytosol shortly after being synthesized as precursors on cytosolic ribosomes. Thus, mitochondrial protein import is an essential process required for biogenesis and functional maintenance of mitochondria. The import process is mainly mediated by two universally conserved membrane complexes, the translocase of the outer membrane (TOM) complex and the translocase of the inner membrane (TIM) complex. The TOM complex mediates the initial translocation of precursor proteins across the outer mitochondrial membrane, and the TIM complex further translocates the precursor proteins across the inner mitochondrial membrane. The TIM complex is also responsible for integration of many integral membrane proteins to the inner membrane. Currently, it is poorly understood how the TOM and TIM complexes mediate these translocation processes. In the current proposal, we aim to address central outstanding questions about protein import mechanisms by the TOM and TIM complexes, using structural, biochemical, and biophysical approaches. These questions include how the translocase complexes specifically recognize their client proteins, how they form a path for protein translocation in the membranes, what are the molecular interactions and forces driving protein translocation, and how the translocase complexes are regulated. In particular, we will perform several cryo-electron microscopy (cryo-EM) studies to visualize the translocase complexes in different functional states, including substrate-engaged states, and gain insights into their mechanisms for substrate engagement and conformational changes. The outcomes of these studies will fundamentally advance our understanding of mitochondrial biology and provide new insights to develop novel approaches to treat mitochondrial-associated diseases, such as neurodegenerative diseases.