The Biosynthetic Pathway of Mitochondrial Respirasomes

描述（由申请人提供）：线粒体氧化磷酸化（OXPHOS）缺陷是一大批异质多系统疾病的原因，也与神经变性和衰老有关。OXPHOS系统由酶复合物I-IV （CI to CIV）和ATP合成酶（Complex V）形成的呼吸链（MRC）组成。RC配合物被组织成超配合物或呼吸小体，以促进底物和电子通道，并尽量减少活性氧的形成。由于这种组织，单个复杂的生物发生依赖于其他RC成分，一个蛋白质编码基因的改变可能导致复合酶复合物缺陷。更好地了解RC的生物发生对于阐明这些疾病的分子基础至关重要。本研究的主要目的是利用酵母、酿酒酵母和培养的人类细胞作为研究模型，研究RC超复合体组装的参与者和机制。我们的长期目标是全面了解导致呼吸小体生物发生的途径及其组成部分，这是开发与RC缺陷相关的疾病治疗方法的先决条件。我们最近报道了人类细胞中MRC超复合物生物合成途径的首次描述。我们的数据表明，呼吸小体的生物发生涉及复合体I组装中间体，作为复合体III和IV亚基结合的支架，而不是起源于预组装的单个全酶的结合。该过程以复合物I NADH脱氢酶催化模块的掺入结束，导致呼吸小体激活。该建议的中心假设是，当复合物III和IV作为自由全酶或通过将自由亚基结合到超复合物中组装时，呼吸小体构成了复合物I组装和激活的结构单元，从而解释了呼吸小体对RC功能的功能意义。提出了三个具体目标来表征超复杂的生物合成途径及其在健康和疾病中的调节。目的1 -完善提出的超复合体组装途径，并测试其在转化和非转化细胞系中的普遍性；目的2 -研究缺乏一种全酶的超复合体组装途径；目的3 -探索在细胞应激条件下诱导MRC酶亚基亚型表达的超复合体组装

DESCRIPTION (provided by applicant): Mitochondrial oxidative phosphorylation (OXPHOS) deficiencies account for a large group of heterogeneous multisystemic disorders and have also been associated to neurodegeneration and aging. The OXPHOS system is comprised of the respiratory chain (MRC) formed by enzymatic Complexes I-IV (CI to CIV) and the ATP synthase (Complex V). The RC complexes are organized into supercomplexes or respirasomes to facilitate substrate and electron channeling and minimize formation of reactive oxygen species. As a consequence of this organization, single complex biogenesis depends on other RC components and alterations in one protein-coding gene can result in combined enzyme complex defects. A better understanding of RC biogenesis is essential for elucidating the molecular basis underlying these diseases. The main objective of the proposed research is to investigate the players and mechanisms involved in RC supercomplex assembly using the yeast Saccharomyces cerevisiae and cultured human cells as research models. Our long-term goal is to attain a complete understanding of the pathways leading to respirasome biogenesis and their components as a prerequisite to the development of therapies for the management of disorders associated with RC deficiencies. We have recently reported the first description of the MRC supercomplexes biosynthetic pathway in human cells. Our data indicate that respirasome biogenesis involves a complex I assembly intermediate acting as a scaffold for the combined incorporation of complexes III and IV subunits, rather than originating from the association of preassembled individual holoenzymes. The process ends with the incorporation of complex I NADH dehydrogenase catalytic module, which leads to the respirasome activation. The central hypothesis of this proposal is that while complexes III and IV assemble either as free holoenzymes or by incorporation of free subunits into supercomplexes, the respirasomes constitute the structural units where complex I is assembled and activated, thus explaining the functional significance of the respirasomes for RC function. Three specific aims are proposed to characterize the supercomplex biosynthetic pathway and its regulation in health and disease. Aim # 1 - To refine the proposed supercomplex assembly pathway and test its universality in transformed and non-transformed cell lines Aim # 2 - To investigate the supercomplex assembly pathway in absence of one of the holoenzymes Aim # 3 - To explore the assembly of supercomplexes under cellular stress conditions that induce the expression of MRC enzyme subunit isoforms