Roles of Molecular Chaperones in Mitochondrial Function

描述（申请人提供）：线粒体是真核生物的重要细胞器，是多种重要代谢过程的场所。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群中很常见。分子伴侣在线粒体的生物合成中起着至关重要的作用。该提案的目标是了解Hsp70/J蛋白分子伴侣在两个关键线粒体过程中的作用机制-蛋白质从细胞质到线粒体基质的易位和Fe/S簇的产生，这是许多酶的关键辅因子。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，蛋白质的有效输入对于线粒体功能至关重要。驱动蛋白质穿过内膜进入基质所需的输入马达由5种基本组分组成，其中基质Hsp70，Ssc1处于其核心。我们将专注于提高进口汽车效率的监管机制。我们将使用遗传，生物化学和结构的方法，了解专门的调节蛋白质的目标：蛋白质相互作用，已经发展到驱动蛋白质跨膜的有效易位。线粒体基质包含一组致力于Fe/S簇生物发生的必需蛋白质。在转移到受体载脂蛋白之前，将簇组装在支架蛋白Isu上。J-protein：Hsp70分子伴侣对Jac1：Ssq1与Isu结合并促进簇的转移。要了解这种伴侣功能在Fe/S簇生物发生的时间组的铁/S簇的形成和转移所需的ISU和其他蛋白质之间的相互作用的机制将被确定，使用生物化学相互作用测定和利用突变蛋白在其与伴侣蛋白的相互作用有缺陷。酵母线粒体系统也将被用来作为一个模型，以了解热休克蛋白70的专业化的分子基础。所获得的知识的基础上的线粒体基质的多个Hsp70的专业化将作为一个范例，了解Hsp70如何演变为功能在一系列的生理过程中，在其他细胞室，特别是在不太明确的人类Hsp70家族的情况下。公共卫生相关性：本提案中描述的研究重点是了解线粒体功能和生物发生的基本方面。线粒体是对能量产生至关重要的基本细胞器。线粒体功能降低与一系列广泛的健康问题有关，从与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.