RNA trafficking in mitochondria

描述(申请人提供)：线粒体是在大多数真核细胞中发现的基本细胞器，提供不同的代谢功能，包括产生能量和专门的代谢物。线粒体需要由线粒体和核基因组编码的蛋白质和RNA。在人类中，至少有1000个核编码蛋白被输入线粒体，而13个蛋白质由线粒体基因编码。这种有限数量的线粒体编码蛋白的翻译需要线粒体核糖体、翻译因子和转移RNA。最近在进化多样性生物中的研究表明，各种RNA成分在细胞核中编码，并从胞浆输入到线粒体。虽然对线粒体蛋白质的导入途径的了解非常详细，但对RNA导入的机制了解很少，更不用说导入的特定RNA底物了。该提案的总体目标是剖析RNA导入线粒体的途径，识别导入的RNA物种，并确定当RNA导入被抑制时的病理后果。RNA结合酶PNPase定位于线粒体膜间间隙，似乎是从细胞质输入的RNA的受体。此外，PNPase只存在于苍蝇、蠕虫和哺乳动物等生物体中，这表明它在高等真核生物中具有功能。为了实现拟议的目标，计划实现以下具体目标：在目标1中，将确定PNPase在线粒体RNA输入和生物发生中的生化作用。在目标2中，我们将建立一个有条件的小鼠模型，在该模型中，PNPase可以以可控的方式被下调，以确定PNPase的生理功能以及PNPase丢失对线粒体功能的影响。最后，在特定的目标3中，将研究PNPase在体内RNA导入中的作用。PNPase的突变与一种神经退行性疾病有关，这表明PNPase在健康和疾病中发挥着重要作用。除了基础知识外，对RNA导入途径的表征可以为开发治疗与线粒体tRNAs或线粒体基因突变相关的严重病理疾病的方法打开新的大门。这项应用对公共卫生有更广泛的影响，因为PNPase的突变与神经退化有关。 公共卫生相关性：这项建议与公共健康相关，因为PNPase基因的突变与一种遗传性神经退行性疾病有关。这种疾病的特征将有助于深入了解线粒体功能障碍是如何导致神经退变的。

DESCRIPTION (provided by applicant): Mitochondria are essential organelles found in most eukaryotic cells and provide for diverse metabolic functions including the production of energy and specialized metabolites. Mitochondria require proteins and RNAs coded both by the mitochondrial and nuclear genomes. In humans, at least 1000 nuclear encoded proteins are imported into mitochondria, whereas 13 proteins are coded by mitochondrial genes. The translation of this limited number of mitochondrial coded proteins requires mitochondrial ribosomes, translation factors, and transfer RNAs. Recent studies in evolutionarily diverse organisms have shown that various RNA components are coded in the nucleus and imported from the cytosol into mitochondria. Whereas the understanding of import pathways for mitochondrial proteins is very detailed, very little is understood about the mechanism of RNA import, let alone the specific RNA substrates that are imported. The overall goal of this proposal is to dissect the pathway of RNA import into mitochondria, identify the RNA species that are imported, and determine pathological consequences when RNA import is inhibited. The RNA-binding enzyme PNPase localizes to the mitochondrial intermembrane space and seems to function as a receptor for RNAs that are imported from the cytosol. In addition, PNPase is only present in organisms such as flies, worms, and mammals, suggesting it functions in higher eukaryotes. To accomplish the proposed goals, the following specific aims are planned: In Aim 1, the biochemical role of PNPase in the import and biogenesis of RNA in the mitochondrion will be determined. In Aim 2, a conditional mouse model in which PNPase can be knocked down in a controlled manner will be characterized to determine the physiologic function of PNPase and the consequences of PNPase loss in mitochondrial function. Finally, in Specific Aim 3, the role of PNPase in RNA import in vivo will be investigated. A mutation in PNPase has been linked to a neurodegenerative disease, suggesting PNPase plays an important role in health and disease. In addition to the fundamental knowledge, characterization of the RNA import pathway can open a new door to develop methods for treating severe pathological diseases associated with mutations in mitochondrial tRNAs or mitochondrial genes. This application has a broader impact in public health because mutations in PNPase have been linked to neurodegeneration. PUBLIC HEALTH RELEVANCE: This proposal is relevant to public health because mutations in the gene PNPase have been linked to a hereditary neurodegenerative disease. Characterization of this disease will provide insight into how mitochondrial dysfunction contributes to neurodegeneration.