Roles of Molecular Chaperones in Mitochondrial Function

描述(申请人提供)：线粒体是多种重要代谢过程的场所，是真核生物必不可少的细胞器。由线粒体功能障碍引起的生物能量能力降低和铁代谢改变的病理效应在人类中很常见。分子伴侣在线粒体的生物发生中起着至关重要的作用。这项研究的目的是了解HSP70/J蛋白分子伴侣在两个关键的线粒体过程中的作用机制--蛋白质从胞浆转运到线粒体基质中和铁/S簇的产生，这两个过程是许多酶的关键辅助因子。线粒体基质的数百种蛋白质中的绝大多数是在胞质核糖体上合成的。因此，蛋白质的有效进口对线粒体的功能至关重要。驱动蛋白质穿过内膜进入基质所需的输入马达由5个基本成分组成，其中基质Hsp70，Ssc1是其核心。我们将集中精力研究提高进口马达效率的监管机制。我们将使用遗传、生化和结构方法，目标是了解专门受调控的蛋白质：蛋白质相互作用已经进化为驱动蛋白质有效地跨膜转移。线粒体基质包含一组致力于Fe/S簇生物发生的必要蛋白质。在转移到受体载脂蛋白之前，这些簇被组装在支架蛋白ISU上。J-蛋白：HSP70伴侣对Jac1：SSQ1与ISU结合，促进簇的转移。为了了解这种伴侣蛋白在Fe/S簇生物发生中的作用机制，我们将利用生化相互作用分析和利用突变蛋白与伴侣蛋白相互作用缺陷的方法，确定ISU与其他铁/S簇形成和转移所需蛋白质之间的相互作用的时间集合。酵母线粒体系统也将被用作了解Hsp70专门化的分子基础的模型。关于线粒体基质中多个Hsp70特化的基础所获得的知识将成为理解Hsp70如何进化到在其他细胞隔室的一系列生理过程中发挥作用的范例，特别是在定义较不明确的人类Hsp70家族的情况下。公共卫生相关性：本提案中描述的研究侧重于了解线粒体功能和生物发生的基本方面。线粒体是重要的细胞器，对能量生产至关重要。线粒体功能降低与一系列健康问题有关，从年龄相关的神经和心血管疾病到早发性神经肌肉疾病。

DESCRIPTION (provided by applicant): Mitochondria, the site of a variety of important metabolic processes, are essential organelles of eukaryotic organisms. Pathological effects of reduced bioenergetic capacity and altered iron metabolism caused by mitochondrial dysfunction are common in human populations. Molecular chaperones play a vital role in the biogenesis of mitochondria. The goal of this proposal is to understand the mechanism of action of Hsp70/J-protein molecular chaperones in two critical mitochondrial processes - translocation of proteins from the cytosol into the mitochondrial matrix and the generation of Fe/S clusters, critical co- factors for numerous enzymes. The vast majority of the hundreds of proteins of the mitochondrial matrix are synthesized on cytosolic ribosomes. Thus, efficient import of proteins is critical for mitochondrial function. The import motor required for driving proteins across the inner membrane into the matrix is composed of 5 essential components, with the matrix Hsp70, Ssc1, at its core. We will concentrate on regulatory mechanisms that increase the efficiency of the import motor. We will use genetic, biochemical and structural approaches, with a goal of understanding the specialized regulated protein:protein interactions that have evolved to drive efficient translocation of proteins across the membrane. The mitochondrial matrix contains a set of essential proteins devoted to the biogenesis of Fe/S clusters. The clusters are assembled on the scaffold protein, Isu, prior to transfer to recipient apo- proteins. The J-protein:Hsp70 chaperone pair, Jac1:Ssq1, binds to Isu and facilitates transfer of the cluster. To understand the mechanism of this chaperone function in Fe/S cluster biogenesis the temporal set of interactions between Isu and other proteins required for Fe/S cluster formation and transfer will be determined, using biochemical interaction assays and exploiting mutant proteins having defects in their interactions with partner proteins. The yeast mitochondrial system will also be used as a model to understand the molecular basis of the specialization of Hsp70s. Knowledge gained as to the basis of the specialization of multiple Hsp70s of the mitochondrial matrix will serve as a paradigm for understanding how Hsp70s have evolved to function in an array of physiological processes in other cellular compartments particularly in the case of the less well-defined human Hsp70 family. PUBLIC HEALTH RELEVANCE: The research described in this proposal focuses on understanding fundamental aspects of mitochondrial function and biogenesis. Mitochondria are essential organelles that are vital for energy production. Reduced mitochondrial function has been linked to a wide array of health issues from age-related neurological and cardiovascular disease to early onset neuromuscular disorders.