ULK, mediator of mTORC1 signaling to aging

描述（由申请人提供）：通过促进mTORC 1抑制进行干预已成为治疗衰老和衰老相关疾病（如癌症）的有前景的治疗策略。mTORC 1抑制如何有助于抗衰老的有益结果仍不清楚。我们的长期目标是了解mTORC 1依赖性自噬如何调节衰老，以及如何利用这些知识来预防衰老和衰老相关疾病。本申请的目的是理解ULK 1和ULK 2（Atg 1的哺乳动物同系物）如何介导mTORC 1活性以调节线粒体稳态和细胞衰老。核心假设是mTORC 1抑制激活ULK 1和ULK 2，从而促进受损线粒体的周转，线粒体是活性氧（ROS）的主要来源，可通过线粒体自噬（mitophagy）引起氧化损伤。我们的假设已经制定了基于我们的初步数据，证明蛋白质复合物含有ULK和Atg 13。我们确定这些蛋白质复合物作为mTORC 1的靶点和mTORC 1活性对自噬机制的介导剂，定义了mTORC 1和自噬之间长期寻求的分子联系。拟议研究的基本原理是，了解ULK如何调节线粒体稳态和细胞衰老将推进mTORC 1在调节寿命中的作用的基本知识，并有助于开发目前缺乏的分子靶点，以提高缺陷线粒体的周转率。该假设将通过追求以下三个具体目标进行检验：1）确定ULK在mTORC 1介导的氧化应激反应和衰老中的作用; 2）确定mTOR-ULK-线粒体途径; 3）确定ULK如何调节线粒体周转。在第一个目标下，我们将分析ULK 1和ULK 2耗竭对受损线粒体积累、氧化应激反应和细胞衰老的影响。根据第二个目标，我们将确定Atg 13上的ULK磷酸化位点，这些位点调节ULK向受损线粒体的募集。在第三个目标下，我们将鉴定由ULK 1和ULK 2磷酸化的线粒体蛋白，并表征它们在线粒体自噬和线粒体动力学中的功能。本申请中提出的研究具有高度创新性，因为它专注于以前未探索的途径，填补了目前存在的将mTORC 1与线粒体稳态调节联系起来的空白。这项研究意义重大，因为它将把对mTORC 1在衰老中功能的理解转变到前所未有的细节水平。这是研究中必不可少的第一步，有望开发出特异性操纵mTORC 1-ULK-线粒体途径以抑制细胞衰老和癌症的策略。 公共卫生相关性：拟议的研究与公共卫生有关，因为确定的机制将促进mTOR-线粒体途径作为预防衰老和延长寿命的有希望的目标的知识。该项目涉及国家卫生研究院的使命，即通过提供预防衰老的新目标来发展基础知识。

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. PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health because the identified mechanism will advance the knowledge of the mTOR-mitochondrial pathway as a promising target to prevent aging and extend longevity. The project addresses the NIH's mission that pertains to developing fundamental knowledge by providing novel targets for prevention of aging.