ULK, mediator of mTORC1 signaling to aging

描述(由申请人提供)：通过促进mTORC1抑制的干预已成为治疗衰老和与衰老相关的疾病(如癌症)的一种有前途的治疗策略。目前尚不清楚mTORC1抑制如何有助于抗衰老的有益结果。我们的长期目标是了解依赖mTORC1的自噬如何调节衰老，以及如何利用这些知识来预防衰老和衰老相关疾病。目前应用的目的是了解ULK1和ULK2(Atg1的哺乳动物同源物)如何介导mTORC1活性来调节线粒体稳态和细胞衰老。中心假设是，mTORC1抑制激活ULK1和ULK2，从而通过线粒体自噬(有丝分裂)促进受损线粒体的周转，线粒体是导致氧化损伤的活性氧物种(ROS)的主要来源。我们的假设是基于我们的初步数据证明了含有ULK和ATG13的蛋白质复合体。我们将这些蛋白质复合体确定为mTORC1的靶标和mTORC1自噬机制的中介，确定了mTORC1和自噬之间长期追求的分子联系。这项拟议研究的基本原理是，了解ULK如何调节线粒体的动态平衡和细胞衰老，将促进对mTORC1在调节寿命中的作用的基础知识，并帮助开发目前缺乏的分子靶点，以提高有缺陷的线粒体的周转。这一假说将通过追求以下三个具体目标来验证：1)确定ULK在mTORC1介导的氧化应激反应和衰老中的作用；2)定义mTOR-ULK-线粒体途径；3)确定ULK如何调节线粒体的周转。在第一个目标下，我们将分析ULK1和ULK2缺失对受损线粒体积累、氧化应激反应和细胞衰老的影响。在第二个目标下，我们将确定ATG13上调节ULK募集到受损线粒体的ULK磷酸化位点。在第三个目标下，我们将鉴定被ULK1和ULK2磷酸化的线粒体蛋白，并表征它们在有丝分裂和线粒体动力学中的功能。这项申请中提出的研究具有很高的创新性，因为它专注于一条以前未被探索的途径，填补了目前存在的将mTORC1与线粒体稳态调节联系在一起的空白。这项拟议的研究意义重大，因为它将把人们对mTORC1在衰老中的作用的理解转变到前所未有的详细程度。这是研究中必不可少的第一步，有望开发出专门操纵mTORC1-ULK-线粒体途径的策略，以抑制细胞衰老和癌症。

DESCRIPTION (provided by applicant): Intervention by promoting mTORC1 inhibition has emerged as a promising therapeutic strategy to treat aging and aging-related diseases such as cancer. How mTORC1 inhibition contributes to such beneficial outcomes for anti-aging remains unclear. Our long-term goal is to understand how mTORC1-dependent autophagy regulates aging and how the knowledge can be utilized to prevent aging and aging-related diseases. The objective of the current application is to understand how ULK1 and ULK2 (mammalian homologues of Atg1) mediates mTORC1 activity toward the regulation of mitochondrial homeostasis and cellular aging. The central hypothesis is that mTORC1 inhibition activates ULK1 and ULK2 thereby facilitating the turnover of damaged mitochondria, the main source of reactive oxygen species (ROS) that can cause oxidative damages, via mitochondrial autophagy (mitophagy). Our hypothesis has been formulated based on our preliminary data demonstrating protein complexes containing ULK and Atg13. We identified these protein complexes as targets of mTORC1 and the mediators of mTORC1 activity toward the autophagy machinery, defining the long sought-after molecular link between mTORC1 and autophagy. The rationale for the proposed research is that understanding how ULK regulates mitochondrial homeostasis and cellular aging will advance the fundamental knowledge of the role of mTORC1 in the regulation of longevity and assist in the development of molecular targets that are currently lacking to enhance the turnover of defective mitochondria specifically. The hypothesis will be tested by pursing the following three specific aims: 1) Define the role of ULK in mTORC1-mediated oxidative stress response and senescence; 2) Define the mTOR-ULK-mitochondrial pathway; 3) Determine how ULK regulates mitochondrial turnover. Under the first aim, we will analyze the effects of ULK1 and ULK2 depletion on accumulation of damaged mitochondria, oxidative stress response, and cellular senescence. Under the second aim, we will identify ULK phosphorylation sites on Atg13 that regulate the ULK recruitment to damaged mitochondria. Under the third aim, we will identify mitochondrial proteins phosphorylated by ULK1 and ULK2 and characterize their function in mitophagy and mitochondrial dynamics. The research proposed in this application is highly innovative, because it focuses on a previously unexplored pathway that fills in the current existing gap that links mTORC1 with the regulation of mitochondrial homeostasis. The proposed research is significant, because it will transform understanding of mTORC1 function in aging to an unprecedented level of detail. This is the essential first step in research that is expected to enable development of strategies that specifically manipulate the mTORC1-ULK-mitochondrial pathway to suppress cellular aging and cancer.