Proteostasis and stem cell aging

 描述（由申请人提供）：在衰老过程中，干细胞功能的丧失被认为在器官变性和功能障碍中起主要作用。因此，能够恢复干细胞的策略可能会导致广泛的退行性疾病的新的和有效的疗法。已经发现了几个细胞过程来驱动衰老过程，但负责干细胞变化的精确机制相对未知。蛋白质稳态的破坏（即，蛋白质稳态）导致细胞内积累 受损和错误折叠的蛋白质，是衰老的主要决定因素。大多数研究蛋白质稳定性的研究集中在蛋白质折叠和降解，试图改善有毒蛋白质聚集体的消除，但蛋白质合成的速率在维持蛋白质组的完整性方面起着重要作用，因为加速的翻译速率可能导致更高的错误氨基酸掺入率以及新生多肽的错误折叠。热量限制和哺乳动物雷帕霉素靶蛋白（mTOR）的抑制都可以降低蛋白质合成速率，并且可能改善的蛋白质稳态在其延长一系列生物体寿命的能力中起主要作用。我们推测，蛋白质合成的定量和定性变化是与年龄相关的干细胞功能丧失的原因。我们还假设，降低蛋白质合成速率将恢复蛋白质稳态和老年人干细胞的功能。为了解决这些假设，我们将研究造血干细胞（HSC）和祖细胞，因为年龄相关的造血变化已经得到很好的描述。此外，我们将利用我们独特的从18- 75岁的正常供体获得人骨髓样本的机会，这将使我们能够最大限度地提高我们研究的人类相关性，这与大多数研究小鼠造血中衰老的研究相反。因此，我们将：（1）。确定衰老对HSC和祖细胞蛋白质合成速率以及翻译机制组分表达的影响和（2）。确定HSPC功能中年龄相关变化的可逆性。对于目标1中的研究，我们将量化蛋白质合成和周转率，并将这些结果与体外和体内功能研究相关联。此外，我们还将进行多核糖体分析，以量化随着衰老发生的翻译机制组分表达的变化。在目标2中，我们将确定雷帕霉素的影响和差异表达的转录调节因子对年轻和老年供体的HSC和祖细胞的作用。如果成功的话，我们的发现将提高我们对衰老的人类造血系统的理解，定义蛋白质稳态在衰老干细胞中的作用，验证关于mTOR抑制对HSC的影响的小鼠研究结果，为改善HSC和其他组织特异性干细胞的功能的新策略提供基础，并作为开发恢复老年人干细胞功能的新策略的基础。

 DESCRIPTION (provided by applicant): During aging, the loss of stem cell function is thought to play a major role in organ degeneration and dysfunction. Therefore, strategies capable of restoring stem cells may lead to novel and effective therapies for a wide-range of degenerative disorders. Several cellular processes have been found to drive the aging process, but the precise mechanisms responsible for changes in stem cells are relatively unknown. The disruption of protein homeostasis (i.e., proteostasis) results in the intracellular accumulation of damaged and misfolded proteins and is a major determinant of aging. The majority of studies examining proteostasis have focused on protein folding and degradation in attempts to improve the elimination of toxic protein aggregates, but the rate of protein synthesis plays a major role i maintaining the integrity of the proteome as accelerated translation rates can lead to higher rates of incorrect amino acid incorporation as well as the misfolding of nascent polypeptides. Both caloric restriction and inhibition of the mammalian Target of Rapamycin (mTOR) can decrease protein synthesis rates and it is possible that improved proteostasis plays a major role in their capacity to extend lifespan across a range of organisms. We hypothesize that both quantitative and qualitative changes in protein synthesis are responsible for the age-related loss of stem cell function. We also hypothesize that reducing protein synthesis rates will restore proteostasis and the function of stem cells from elderly individuals. In order to address these hypotheses, we will study hematopoietic stem cells (HSCs) and progenitors since age-related changes in hematopoiesis have been well described. Furthermore, we will take advantage of our unique access to human bone marrow samples from normal donors ranging in age from 18- 75 years old that will allow us to maximize the human relevance of our studies in contrast to most studies that have investigated aging within murine hematopoiesis. Accordingly, we will: (1). determine the impact of aging on HSC and progenitor protein synthesis rates and the expression of translational machinery components and (2). determine the reversibility of age-related changes in HSPC function. For studies in Aim 1 we will quantify the rates of protein synthesis and turnover and correlate these results with in vitro and in vivo functional studies. Moreover, we will carry out polysome profiling to quantify changes in the expression of components of the translational machinery that occur with aging. In Aim 2, we will determine the impact of rapamycin and the role of differentially expressed regulators of translational on HSCs and progenitors from young and elderly donors. If successful, our findings will improve our understanding of the aging human hematopoietic system, define the role of proteostasis in aging stem cells, validate the results of murine studies regarding the effects of mTOR inhibition on HSCs, provide the basis for novel strategies to improve the function of both HSCs and other tissue-specific stem cells, and serve as the basis for the development of novel strategies to restore stem cell function in the elderly.