Role of S6 Kinase 2 in Aging

描述（由申请人提供）：在各种生物体中，由蛋白质TOR（雷帕霉素的靶标）控制的营养传感途径的调节导致寿命延长。这一发现对人类健康有显著的潜在益处。然而，由于对其作用机制的不了解，延缓了其在临床健康方面的应用。哺乳动物TOR复合物1 （mTORC1）可被复方雷帕霉素药理学抑制。雷帕霉素主要通过S6激酶1和2 （S6K1和S6K2）抑制TOR活性的一个特定子集。雷帕霉素可以延长雄性和雌性小鼠的寿命，但也会通过未知的机制对健康产生负面影响。缺乏s6k1的雌性小鼠，而不是雄性小鼠，寿命延长，这表明另一种激酶S6K2在雷帕霉素延长寿命中的作用。此外，没有关于s6k2缺陷小鼠寿命的数据。有趣的是，S6K2与保护细胞免于凋亡有关。另外，肿瘤抑制机制是细胞衰老（一种永久性的细胞生长抑制程序）。可能表达S6K2的细胞促进衰老而不是凋亡作为防止肿瘤出现的机制。随着年龄的增长，细胞衰老积累被广泛认为是衰老表型的一个因素。这些细胞分泌促炎细胞因子，一种被称为SASP的表型，用于衰老相关的分泌表型，因此，它们在衰老生物体中的积累可能导致慢性炎症，从而刺激年龄相关病理的出现。最近，研究表明，清除衰老细胞可减轻类早衰小鼠模型中与年龄相关的表型。我的初步数据显示，在培养的衰老细胞中，雷帕霉素减少了这些促炎细胞因子的产生，并且通过下调S6K2而不是S6K1获得了类似的结果。我的假设是，S6K2活性的降低通过减轻衰老小鼠的衰老表型来延长健康和寿命。我的研究计划将验证这样一个假设，即通过雷帕霉素或其他方式抑制复合物活性，通过抑制S6K2活性来降低SASP，特别是其促炎臂。我将进一步验证抑制S6K2活性导致小鼠寿命和健康寿命延长的假设。此外，我将探讨S6K2的作用机制，并确定其主要底物。我将通过评估S6K2缺陷细胞和小鼠的细胞、组织表型和生理，以及表达或缺乏S6K2的人类成纤维细胞来实现这些目标。我将使用先进的生物化学和细胞生物学技术检查细胞、组织和动物的相关表型。这个奖项将成为我实现教授这一职业目标和制定改善人类健康战略这一科学目标的跳板。该奖项的指导部分将为我提供必要的技能，以实现科学独立和完成我的短期科学目标。为了实现这一目标，我将得到众多合作者的帮助，也将得到两个各自领域的两位导师专家的帮助（衰老与Judith Campisi博士和小鼠健康跨度与Richard Miller博士）。我的两位导师也将在科学和个人层面帮助我准备成为老龄化领域的助理教授。此外，在受指导的阶段，我将参加加州大学戴维斯分校的组织学强化课程。然后，我将全副武装地接受该奖项的独立部分，在那里我将继续研究S6K2消耗对体内细胞衰老的影响及其对小鼠健康寿命的作用。

DESCRIPTION (provided by applicant): Modulation of the nutrient sensing pathway governed by the protein TOR (target of rapamycin) leads to lifespan extension in various organisms. This discovery has outstanding potential health benefits for humans. However, failure to understand its mechanisms of action has slowed down its application for clinical healthspan benefits. The mammalian TOR complex 1 (mTORC1) can be pharmacologically inhibited with the compound rapamycin. Rapamycin inhibits a particular subset of TOR activity, mainly through S6 Kinase 1 and 2 (S6K1 and S6K2). Rapamycin extends lifespan of male and female mice, but also has negative effect on health via unknown mechanisms. S6K1-deficient female mice, but not male mice, have an extended lifespan suggesting a role for the other kinase, S6K2, in the lifespan extension by rapamycin. Also, no data is available regarding the lifespan of S6K2-deficient mice. Interestingly, S6K2 has been link to protect cells against apoptosis. Another, tumor suppressor mechanism is cellular senescence (a permanent cell growth arrest program). It is possible that cells expressing S6K2 favor senescence rather than apoptosis as a mechanism to protect against tumor apparition. Cellular senescence accumulation with age is widely seen as a contributor of aging phenotypes. These cells secrete proinflammatory cytokines a phenotype termed SASP for senescence- associated secretory phenotype and, therefore, their accumulation in an aging organism could contribute to chronic inflammation known to stimulate the apparition of age-related pathologies. Recently, it was shown that clearance of senescent cells alleviates age-related phenotypes in the progeroid mouse model. My preliminary data show that, in senescent cells in culture, rapamycin decreases the production of these proinflammatory cytokines and that similar results are obtained by downregulating S6K2, but not S6K1. My hypothesis is that reduction of S6K2 activity extends health- and lifespan by alleviating the senescent phenotype in aging mice. My research proposal will test the hypothesis that dampening complex activity by rapamycin or other means decreases the SASP, particularly its pro-inflammatory arm, by suppressing S6K2 activity. I will further test the hypothesis that suppression of S6K2 activity results in extension of both lifespan and healthspan in mice. Further, I will explore the mechanisms by which S6K2 acts and identify its major substrates. I will accomplish these aims by evaluating cells, tissues phenotypes and the physiology of S6K2 deficient cells and mice, as well as S6K2-expressing or -depleted human fibroblasts. I will examine the cells, tissues and animals for the relevant phenotypes using advanced biochemical and cell biological techniques. This award will serve me as a springboard to achieve my career goal for being professor and my scientific goals of developing strategies to ameliorate human healthspan. The mentored portion of the award will provide me with the necessary skills to achieve scientific independence and accomplish my short-term scientific goal. To achieve that I will received the help of numerous collaborators but also from two mentors experts in the two respective fields (senescence with Dr. Judith Campisi and mice healthspan with Dr. Richard Miller). My two mentors will also help for my preparation to become an assistant professor in the field of aging both at the scientific and personal level. In addition during the mentored phase I will take an intensive histology class from UC Davis. I will then be fully armed to embrace the independent portion of the award where I will continue studying the effects that S6K2 depletion on cellular senescence in vivo and its role on mice healthspan.