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已被充分记录，并且热量限制已被证明可以延长多种生物体的寿命。线虫和果蝇的遗传学研究表明，通过PI3K及其下游效应物丝氨酸/苏氨酸激酶Akt介导的胰岛素信号传导受损与能量代谢下降和寿命延长有关。在秀丽隐杆线虫中，决定寿命的胰岛素信号的最远端效应因子是叉头转录因子DAF-16， Akt通过磷酸化使其失活。因此，Akt活性降低会增加DAF-16活性，从而延长寿命。Akt的另一个保守的下游效应，雷帕霉素靶点（TOR），最近被认为与线虫和苍蝇的寿命调节有关。然而，PISK/Akt信号通路对哺乳动物寿命的贡献尚未得到充分探讨。特别是，没有现存的遗传证据支持这一途径在哺乳动物寿命中的作用。这可能部分归因于该通路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寿命中的作用变得复杂。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。小鼠具有由不同基因（aktl、akt2和akt3）编码的三种Akt亚型。我们建议利用我们实验室产生的基因工程akt缺陷小鼠的可用性。这些动物缺乏单独或组合的akt基因。它们为研究Akt活性和单个Akt亚型对寿命和氧化应激依赖性衰老和衰老的贡献提供了良好的遗传模型。在细胞水平上，我们将扩展我们最初的观察结果，即Akt（敲除）KO小鼠衍生的细胞比野生型小鼠表现出更低的细胞内活性氧（ROS）基础水平，而表达活化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。在机体水平上，我们将确定由单个同种异构体缺失引起的Akt活性的部分消融（单独或联合）是否足以延长小鼠的正常寿命并赋予其抗氧化应激能力。

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.