Discovery of genes that extend yeast lifespan: Aging in immobilized cell reactors

发现延长酵母寿命的基因：固定化细胞反应器中的老化

• 批准号: 7305291
• 负责人: Raphael F Rosenzweig
• 金额: $ 21.23万
• 依托单位: UNIVERSITY OF MONTANA
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7305291
• 关键词: Age; Aging; Alginates; Biology of Aging; Biomass; Bioreactors; Caloric Restriction; Cell Aging; Cell Maintenance; Cell division; Cells; Class; Collection; Condition; Data; Depth; Environment; Ethanol; Eukaryota; Eukaryotic Cell; Fellowship; Gene Deletion; Gene Expression; Genes; Genetic; Genetic Determinism; Genetic Screening; Genomics; Homologous Gene; Human; Immobilization; Immobilized Cells; Individual; Interphase Cell; Investigation; Life; Longevity; Mammals; Metabolic; Metabolism; Microbe; Mothers; Mutation; Nutrient; Pathway interactions; Phase; Physiological; Population; Proteins; Purpose; Quality of life; Rate; Relative (related person); Reproduction; Resistance; Resources; Role playing therapy; Saccharomyces cerevisiae; Solid; Stress; System; Time; Week; Yeasts; cell age; cell growth; feeding; gene discovery; improved; insight; longevity gene; member; mutant; sugar; symposium; tool

DESCRIPTION (provided by applicant): - Many of our deepest insights into the biology of aging have been gained using the simple Eukaryote Saccharomyces cerevisiae. Foundational studies using yeast have led to the discovery of the role played by the silent information regulator protein Sir2 in modulating replicative lifespan, and the roles played by Ras2, Cyr1 and Sch9 in modulating chronological lifespan. Each of these genes has a homologue with similar function in higher Eukaryotes, including mammals. These discoveries have generated excitement about the prospects for extending lifespan and improving quality of life for older members of the human population. To date, all investigations into the genetic mechanisms that extend chronological lifespan in yeast have focused on the viability of non-growing planktonic cells in stationary-phase batch culture. There, cells enter a physiological state where metabolism is reprogrammed to efficiently use stored resources for the purpose of cell maintenance. Not surprisingly, screens for mutants which alter chronological lifespan under these conditions have produced a collection of genes whose activities influence resistance to stress. But yeast populations largely cease to reproduce in another, very different environmental context. Continuously or semi-continuously fed bioreactors populated by yeast immobilized in semi-solid beads can be maintained for weeks, or even months. These reactors continue to produce close-to-theoretical yields of ethanol but very little biomass, relative to substrate input. Herein, we present demographic, physiological and genomic data that illuminate features of the immobilized state, features that we contend make this system ideally suited for the study of chronological aging. We propose to follow on from these results with an investigation into the mechanism(s) that enable yeast to live for extended periods of time in a calorically un-restricted environment wherein metabolic flux appears to be maximized at the expense of cell growth and reproduction. The Specific Aims of this investigation are threefold; we will: (1) Determine in wild-type yeast whether long-term immobilization alters chronological lifespan and global gene expression relative to aging planktonic cultures; (2) Establish, relative to wild-type, whether mutations known to alter both replicative and chronological lifespan in planktonic cells produce similar alterations in aging immobilized cells. (3) Conduct a large-scale genetic screen of single-gene-deletion yeast strains cultured in the immobilized and planktonic states (a) to discover new classes of longevity genes that act in undescribed pathways, and (b) to establish whether there are common determinants of chronological longevity under calorically-restricted and non-calorically-restricted conditions. PROJECT NARRATIVE - Many of our deepest insights into the biology of aging have been gained using the simple microbe, Bakers yeast. Individual yeast cells have a finite lifespan, and they age in two ways: mother cells age as they undergo successive rounds of cell division; non-dividing cells also age and eventually die. Caloric restriction appears to extend lifespan in all species studied, including yeast. But controversy surrounds the issue of whether caloric restriction is a proximal or ultimate cause of longevity. To date, all studies on the genetics on non-dividing cells have imposed caloric restriction, making this variable impossible to tease out. Yeast can be confined within semi-solid alginate beads and exposed to excess nutrients. There, they convert sugar to ethanol at extremely high rates, but do so with little or no cell division. We will exploit this system as a tool to discover whether lifespan extension is possible under calorically non- restrictive conditions, and if so, we aim to discover underlying genetic determinants.

描述（由申请人提供）：我们对衰老生物学的许多最深刻的见解都是通过使用简单的真核生物酿酒酵母获得的。利用酵母进行的基础研究发现，沉默信息调节蛋白Sir2在调节复制寿命中所起的作用，以及Ras2、Cyr1和Sch9在调节时间顺序寿命中所起的作用。这些基因中的每一个在包括哺乳动物在内的高等真核生物中都有类似功能的同源物。这些发现让人们对延长寿命和提高老年人生活质量的前景感到兴奋。迄今为止，所有对延长酵母按时间顺序寿命的遗传机制的研究都集中在静止期分批培养中不生长的浮游细胞的生存能力上。在那里，细胞进入一种生理状态，新陈代谢被重新编程，以有效地利用储存的资源来维持细胞。毫不奇怪，在这些条件下，对改变时间顺序寿命的突变体的筛选已经产生了一系列基因，这些基因的活动影响对压力的抵抗力。但酵母种群在另一种非常不同的环境中基本上停止了繁殖。连续或半连续投料的生物反应器中填充的酵母固定化在半固体珠可以维持数周，甚至数月。这些反应器继续产生接近理论的乙醇产量，但相对于底物的投入，生物量很少。在此，我们提出了人口统计学、生理学和基因组学数据，阐明了固定状态的特征，我们认为这些特征使这个系统非常适合于时间顺序衰老的研究。我们建议在这些结果的基础上，对酵母菌在热量不受限制的环境中存活更长时间的机制进行研究，在这种环境中，代谢通量似乎以牺牲细胞生长和繁殖为代价最大化。本调查的具体目的有三个方面；我们将：(1)确定在野生型酵母中，长期固定化是否会改变相对于老化的浮游生物培养物的时间顺序寿命和整体基因表达；(2)相对于野生型，确定在浮游细胞中改变复制寿命和时间顺序寿命的已知突变是否会在老化的固定细胞中产生类似的变化。(3)对固定化和浮游状态下培养的单基因缺失酵母菌株进行大规模遗传筛选(a)以发现在未描述的途径中起作用的新类别的长寿基因，(b)确定在热量限制和非热量限制条件下是否存在按时间顺序长寿的共同决定因素。项目叙述——我们对衰老生物学的许多最深刻的见解都是通过使用一种简单的微生物——面包师酵母获得的。单个酵母细胞的寿命是有限的，它们以两种方式衰老：母细胞在经历连续的细胞分裂时衰老；非分裂细胞也会衰老并最终死亡。热量限制似乎可以延长所有被研究物种的寿命，包括酵母。但是，热量限制是长寿的直接原因还是最终原因，这个问题一直存在争议。迄今为止，所有关于非分裂细胞的遗传学研究都施加了热量限制，使得这个变量无法梳理出来。酵母可以被限制在半固态海藻酸珠和暴露于过量的营养。在那里，它们以极快的速度将糖转化为乙醇，但在此过程中很少或根本没有细胞分裂。我们将利用这个系统作为一种工具来发现在热量非限制性条件下是否可能延长寿命，如果是这样，我们的目标是发现潜在的遗传决定因素。