TOR, Translation and Aging

描述（由申请人提供）：蠕虫和酵母研究将通过饮食限制延长寿命与改变翻译调节联系起来。一致地，TOR信号传导或S6激酶活性降低导致两种无脊椎动物的寿命增加，并延迟哺乳动物中年龄相关疾病的发作。除了蛋白激酶A（PKA），TOR和Sch9还产生了三种与酵母寿命调节相关的营养响应激酶。在这个提议中，我们采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。作为长寿酵母基因缺失菌株的全基因组筛选的结果，我们确定了一些核糖体大亚基基因缺失，导致60 S亚基生物合成减少。减少的60S亚基生物合成导致寿命延长的一种机制是通过增强GCN 4转录因子的翻译。GCN 4翻译也由减少的TOR信号传导诱导，并且在这种情况下是最大寿命延长所需的，使其成为调节酵母衰老的常见机制。Gcn4靶点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翻译的调节系统在包括人类在内的所有真核生物中高度保守。在本提案的目标1中，我们进行了一系列实验以确定导致GCN 4活化的机制以及GCN 4对酵母老化的重要靶点。虽然增强的GCN 4翻译是通过减少60S亚基生物合成和营养信号传导延长寿命的一种机制，但我们的证据表明还存在其他机制。因此，在目标2中，我们描述了使用一系列无偏和定向的方法来识别这些GCN 4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：核糖体生物合成减少是否会导致哺乳动物寿命延长。为了验证这一点，我们将确定缺乏核糖体大亚基基因的小鼠的寿命，因为在蠕虫和酵母中相似的突变延长了寿命。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将减少的营养信号和核糖体生物合成与衰老联系起来的机制，并测试它们的影响是否延伸到哺乳动物。

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.