TOR, Translation and Aging

描述(申请人提供)：对蠕虫和酵母的研究将饮食限制延长寿命与改变翻译调控联系在一起。一直以来，TOR信号或S6激酶活性的降低会导致这两种无脊椎动物寿命的延长，并推迟哺乳动物年龄相关疾病的发生。除了蛋白激酶A(PKA)外，TOR和Sch9还产生三种与酵母长寿调节相关的营养响应蛋白。在这项建议中，我们使用酵母作为模式生物，通过减少营养信号、饮食限制或改变翻译调节来解决导致酵母复制寿命延长的机制。作为对长寿酵母基因缺失菌株全基因组筛选的结果，我们发现了一些核糖体大亚基基因缺失，导致60S亚基生物合成减少。减少60S亚单位的生物发生导致寿命延长的一个机制是通过增强GCN4转录因子的翻译。Gcn4的翻译也是由减少的TOR信号诱导的，在这种情况下最大限度地延长寿命是必需的，这使得这成为调节酵母衰老的常见机制。Gcn4的靶标包括氨基酸生物合成基因以及应激反应和线粒体因子。控制GCN4翻译的调控系统在包括人类在内的所有真核生物中都高度保守。在本提案的目标1中，我们进行了一系列实验，以确定导致Gcn4激活的机制以及Gcn4在酵母衰老中的重要靶点。虽然增强的Gcn4翻译是通过减少60S亚单位的生物发生和营养信号来延长寿命的一个机制，但我们的证据表明，也存在其他机制。因此，在目标2中，我们描述了使用一系列无偏见和定向的方法来识别这些Gcn4独立机制的努力。最后，在目标3中，我们解决了第二个主要问题：核糖体生物发生减少是否会导致哺乳动物寿命延长。为了测试这一点，我们将确定缺乏核糖体大亚基基因的小鼠的寿命，因为类似的突变延长了蠕虫和酵母的寿命。我们还将测试一系列与年龄相关的表型，重点是代谢输出。总之，这些研究将更好地定义营养信号减少和核糖体生物发生与衰老之间的联系，并测试它们的影响是否延伸到哺乳动物。公共卫生相关性：越来越多的人认识到，减缓衰老的干预措施将为与年龄相关的疾病提供广泛的好处，包括神经退化、癌症和心血管疾病。在这个提案中，我们在机制水平上解决了蛋白质翻译和衰老之间的关系。通过更好地了解受调控的蛋白质翻译在衰老中所起的调节作用，我们将能够准确地确定药物干预的关键靶点。

DESCRIPTION (provided by applicant): Studies in worms and yeast have linked lifespan extension by dietary restriction to altered translational regulation. Consistently, reduced TOR signaling or S6 kinase activity leads to increased lifespan in both invertebrates, and delays the onset of age-related diseases in mammals. In addition to Protein Kinase A (PKA), TOR and Sch9 make three nutrient-responsive kinases linked to yeast longevity modulation. In this proposal, we employ yeast as a model organism to address the mechanisms by reduced nutrient signaling, dietary restriction, or altered translational regulation that lead to extension of yeast replicative lifespan. As a result of a genome-wide screen for long-lived yeast gene deletion strains, we identified a number of ribosomal large subunit gene deletions that result in reduced 60S subunit biogenesis. One mechanism by which reduced 60S subunit biogenesis lead to lifespan extension is through enhanced translation of the GCN4 transcription factor. GCN4 translation is also induced by reduced TOR signaling and required for maximum lifespan extension in this setting, making this a common mechanism modulating yeast aging. Gcn4 targets include amino acid biosynthetic genes as well as stress responsive and mitochondrial factors. The regulatory system controlling Gcn4 translation is highly conserved in all eukaryotes including humans. In Aim 1 of this proposal, we perform a series of experiments to determine the mechanisms leading to GCN4 activation and the targets of GCN4 important for yeast aging. While enhanced GCN4 translation is one mechanism underlying lifespan extension by reduced 60S subunit biogenesis and nutrient signaling, our evidence indicates that others exist as well. Therefore, in Aim 2 we describe efforts to identify these GCN4- independent mechanisms using a series of approaches both unbiased and directed. Finally, in Aim 3 we address a second major question: does reduced ribosome biogenesis lead to lifespan extension in mammals. To test this, we will determine the longevity of mice lacking ribosomal large subunit genes chosen because of similar mutations extend lifespan in worms and yeast. We will also test a series of age-associated phenotypes, focusing on metabolic outputs. Together, these studies will better define the mechanisms linking reduced nutrient signaling and ribosome biogenesis to aging and test whether their effects extend to mammals. PUBLIC HEALTH RELEVANCE: It is increasingly becoming recognized that interventions to slow aging will provide broad spectrum benefits to age-related diseases including neurodegeneration, cancer and cardiovascular disease. In this proposal, we address at the mechanistic level the relationship between protein translation and aging. Through achieving a better understand of the modulatory role played by regulated protein translation in aging, we will be able to pinpoint key targets for pharmacological interventions.