Akt, cellular senescence, and lifespan

描述(由申请人提供)：寿命和能量代谢之间的耦合被很好地记录下来，并且卡路里限制被证明延长了广泛范围的生物体的寿命。对线虫和果蝇的遗传学研究表明，通过PI3K及其下游效应因子丝氨酸/苏氨酸激酶Akt影响胰岛素信号，与能量代谢下降和寿命延长有关。在线虫中，决定寿命的胰岛素信号最远端的效应物是叉头转录因子DAF-16，它被Akt通过磷酸化失活。因此，Akt活性降低会增加DAF-16活性，从而延长寿命。另一个保守的Akt下游效应子是雷帕霉素(TOR)的靶标，最近被发现参与了线虫和苍蝇寿命的调节。然而，Pisk/Akt信号通路对哺乳动物长寿的作用还没有得到深入的研究。特别是，没有现有的遗传学证据支持这一途径在哺乳动物寿命中发挥作用。这可能部分归因于该途径与一系列过程的关联，包括细胞凋亡、葡萄糖代谢和分化，这使得评估其在调节哺乳动物长寿中的作用变得复杂。我们的长期目标是确定Akt是否可以调节小鼠的寿命和对氧化应激的敏感性。小鼠有三种Akt亚型，由不同的基因(akt1、Akt2和akt3)编码。我们建议利用我们实验室培育的基因工程Akt缺陷小鼠的可用性。这些动物缺乏单独的AKT基因，无论是单独的还是组合的。它们为研究Akt活性和单个Akt亚型对长寿和氧化应激依赖的衰老和衰老的贡献提供了优秀的遗传模型。在细胞水平上，我们将扩展我们的初步观察，来自Akt(基因敲除)KO小鼠的细胞比它们的野生型细胞表现出更低的细胞内活性氧(ROS)基础水平，而表达激活Akt的细胞产生更高的ROS水平。这些变化与能量代谢和氧气消耗的相应变化有关。我们将阐明Akt活性调节细胞内ROS丰度的机制，以及Akt在调节细胞衰老中的作用。在生物体水平上，我们将确定单独或联合丢失单个亚型导致的Akt活性的部分消融是否足以延长小鼠的正常寿命并增强对氧化应激的抵抗力。

DESCRIPTION (provided by applicant): The coupling between lifespan and energy metabolism is well documented, and caloric restriction was shown to extend the lifespan of a wide spectrum of organisms. Genetic studies in nematodes and flies showed that impaired insulin signaling through PI3K and its downstream effector, the serine/threonine kinase, Akt, is associated with a decline in energy metabolism and an extended lifespan. In C. elegans, the most distal effector of insulin signaling that determines lifespan is the forkhead transcription factor, DAF-16, which is inactivated by Akt via phosphorylation. Thus, reduced Akt activity increases DAF-16 activity and thereby increases lifespan. Another conserved downstream effector of Akt, the target of rapamycin (TOR), was recently implicated in the regulation of lifespan both in nematodes and flies. However, the contribution of the PISK/Akt signaling pathway to longevity in mammals has not been thoroughly explored. In particular, there is no extant genetic evidence supporting a role for this pathway in mammalian lifespan. This may be due, in part, to the association of this pathway with an array of processes including, apoptosis, glucose metabolism, and differentiation, which complicate evaluating its role in modulating mammalian longevity. Our long-term goal is to determine whether Akt can regulate lifespan and sensitivity to oxidative stress in mice. The mouse has three Akt isoforms encoded by distinct genes (aktl, akt2, and akt3). We propose to take advantage of the availability of genetically engineered Akt-deficient mice generated in our laboratory. These animals lack individual akt genes, alone and in combination. They provide excellent genetic models for examination of the contributions of Akt activity and individual Akt isoforms to longevity and oxidative-stress-dependent aging and senescence. At the cellular level, we will expand on our initial observations that cells derived from Akt (knockout) KO mice exhibit lower basal levels of intracellular reactive oxygen species (ROS) than their wild-type counterparts, whereas cells expressing activated Akt generate higher ROS levels. These changes are associated with corresponding changes in both energy metabolism and oxygen consumption. We will elucidate the mechanisms whereby Akt activity regulates intracellular ROS abundance and the role of Akt in the regulation of cellular senescence. At the organism level, we will determine whether partial ablation of Akt activity caused by the loss of individual isoforms, alone or in combination, is sufficient to extend normal lifespan and confer resistance to oxidative stress in the mouse.