A 'Mitochondria-nucleus-ribosome' Signaling Axis Controls Lifespan in Mit Mutants

描述（由申请人提供）：本研究的长期目标是改善美国老年人的健康和福祉。我们的直接目标是研究线粒体功能的破坏是如何与衰老过程联系起来的。近年来，人们已经清楚地认识到，细胞中产生能量的关键部位线粒体的电子传递链缺陷与许多与年龄相关的疾病有关，包括心脏病、II型糖尿病、帕金森病、阿尔茨海默氏痴呆症和癌症。15%的美国人患有这些慢性退行性疾病。虽然还不能说线粒体引起了这些问题，但很明显，线粒体的变化与此有关，因为它们的功能发生了明显的改变。也许最令人惊讶的是，在包括老鼠、苍蝇、线虫和酵母在内的几个物种中发现了许多突变体，它们对线粒体电子传递链功能障碍的矛盾反应是延长它们的寿命。对这个有趣的突变家族的研究为线粒体及其在衰老中的作用提供了新的线索。

DESCRIPTION (provided by applicant): The long-term goal of this study is to improve the health and well-being of older Americans. Our immediate goal is to examine how disruption of mitochondrial function is linked with the aging process. In recent years, it has become clear that defects in the electron transport chain of mitochondria, the key site of energy production in cells are linked with many age-related diseases - including heart disease, Type II diabetes, Parkinson Disease, Alzheimer's dementia, and cancer. 15% of the US population suffers from these chronic degenerative disorders. While it cannot yet be said that mitochondria cause these problems, it is clear that changes in mitochondria are involved, because their function is measurably altered. Perhaps most surprising has been the discovery of a number of mutants, across several species including mice, flies, nematodes and yeast, that paradoxically respond to mitochondrial electron transport chain dysfunction with increases in their lifespan. Investigation of this intriguing family of mutants is shedding new light on mitochondria and their role in aging. In this study, we will examine aging in the Caenorhabditis elegans Mit mutants, which are all long-lived and contain defective mitochondrial electron transport chain activity. We have uncovered evidence for a novel, three component signaling cascade in these mutants that links disruption of mitochondrial ETC activity with nuclear checkpoint signaling, blockade of cytoplasmic ribosomal translation, and lifespan control. This is a completely unexpected finding because these processes span three distinct cellular compartments. Our current study will define the cause and effects of this novel signaling cascade. We hypothesize that disruption of nucleotide synthesis in Mit mutants underlies activation of their nuclear checkpoint response. We have identified three checkpoint proteins that are activated in these animals, and now our preliminary data points toward a direct ribosomal target that potentially acts as a key longevity control point by regulating trafficking of nuclear-encoded proteins to the mitochondria. Our specific objectives will be determined if the biosynthesis of ribonucleotides is altered in Mit mutants. We will also determine if there is nuclear transcriptional stalling in these animals. Finally we will test whether our identified ribosomal target does indeed differentially act to control translation of nuclear-encoded mitochondrial ETC transcripts following checkpoint activation. We will address these questions through the use of powerful biochemical and genetic tools. We will use LC-MS/MS to quantify changes in nucleotide pools, quantitative PCR to determine if transcriptional stalling is occurring, and a combination of transgenic reporters, polysomal profiling and RNA Seq to determine if nuclear-encoded mitochondrial proteins are differentially prevented from being translated in Mit mutants.