TSC2 Localization and Function at the Peroxisome

TSC2 在过氧化物酶体上的定位和功能

• 批准号: 8015641
• 负责人: Cheryl L. Walker
• 金额: $ 31万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-25 至 2011-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8015641
• 关键词: ATM activation; Apoptosis; Attention; Autophagocytosis; Autophagosome; Carrier Proteins; Catabolism; Cell physiology; Cells; Clofibrate; Complex; Confocal Microscopy; Data; Development; Fractionation; Future; Gatekeeping; Generations; Hepatocarcinogenesis; Homeostasis; Imagery; Knockout Mice; Mediating; Membrane; Monomeric GTP-Binding Proteins; Organelles; Oxidation-Reduction; Oxidative Stress; Pathway interactions; Peroxisome Proliferators; Phosphotransferases; Physiological; Play; Prevention strategy; Process; Production; Protein Biosynthesis; Proteins; Proto-Oncogene Proteins c-akt; Ras homolog enriched in brain; Reactive Oxygen Species; Regulation; Repression; Role; STK11 gene; Signal Pathway; Signal Transduction; Site; TSC1 gene; Testing; Therapeutic; Time; Tuberous sclerosis protein complex; Tumor Suppressor Proteins; biological adaptation to stress; cancer therapy; carcinogenesis; cell growth; design; fatty acid oxidation; human FRAP1 protein; in vivo; mutant; neoplastic cell; novel; peroxisome; public health relevance; receptor; research study; response; sensor

DESCRIPTION (provided by applicant): The Tuberous Sclerosis Complex 2 (TSC2) tumor suppressor functions as a gatekeeper for mTOR activity in the PI3K signaling pathway. The mTOR kinase regulates several cellular functions, including protein synthesis, cell growth and autophagy, with TSC2 functioning as a rheostat to regulate mTOR by integrating mitogenic signals with energy availability. Interestingly, TSC2-deficent cells have aberrant redox homeostasis, and our preliminary data indicate TSC2 is required for mTOR repression by reactive oxygen species (ROS), leading us to hypothesize that TSC2 represses mTOR in response to oxidative stress. In addition, we found that the cellular damage sensor ATM is activated by ROS, and that in the absence of either ATM or TSC2, cells are unable to appropriately repress mTOR in response to ROS. It is known that TSC2 localizes to cellular endomembranes, and that membrane localization regulates TSC2 function. However, the specific endomembrane(s) to which this tumor suppressor localizes has not been determined. Importantly, we found that both ATM and TSC2 localize to the peroxisome, a major site for 2-oxidation of fatty acids and generation of ROS in the cell. These data have led us to propose the hypothesis that ATM and TSC2 participate in a stress response pathway at the peroxisome that responds to ROS to repress mTOR signaling. As mTOR is a negative regulator of autophagy, we hypothesize that the physiological role for TSC2-mediated mTOR repression in response to ROS is to regulate autophagy and peroxisome turnover. The overarching hypothesis of this proposal is that the TSC2 tumor suppressor participates downstream of ATM in a novel stress response pathway at the peroxisome to repress mTOR signaling and regulate autophagy. To test this hypothesis, we propose the following Specific Aims: Specific Aim 1: Test the hypothesis that TSC2 and components of this mTOR regulatory node (the TSC2 activation partner TSC1, its GAP target Rheb and mTOR) localize to the peroxisome. Specific Aim 2: Identify the signaling pathway(s) that regulate TSC2 function at the peroxisome. Specific Aim 3: Test the hypothesis that peroxisomal TSC2 represses mTOR to regulate autophagy and/or peroxisomal turnover by pexophagy. The experiments proposed in this application will allow us to test our hypothesis that TSC2 participates downstream of ATM in a novel stress response pathway at the peroxisome to repress mTOR and regulate cellular autophagy. If this hypothesis is correct, and we are successful at demonstrating that this peroxisome- localized pathway has physiological significance, these studies will for the first time focus attention on the peroxisome as a signaling organelle. In addition, they will lay the groundwork for future studies to understand how cell signaling at the peroxisome participates in carcinogensis and open the possibility for the development of strategies targeting the peroxisome to regulate cell signaling and autophagy in tumor cells. PUBLIC HEALTH RELEVANCE: The overarching hypothesis of this proposal is that TSC2 participates in a novel stress response pathway at the peroxisome to repress mTOR signaling and regulate cellular autophagy. Understanding the mechanisms that regulate the process of autophagy or influence the cell's decision to initiate this process has important implications for carcinogenesis and cancer therapy. A better understanding of the mechanisms that control this process has the potential to aid in the design of prevention strategies targeting the peroxisome and signaling pathways that localize to this organelle. In addition, in the future they may aid in the design of therapeutics that limit the ability of tumor cells to utilize autophagy as a survival pathway and/or promote autophagy-induced programmed cell death in response to therapy.

描述（由申请人提供）：结节性硬化症复合体 2 (TSC2) 肿瘤抑制因子在 PI3K 信号通路中充当 mTOR 活性的看门人。 mTOR 激酶调节多种细胞功能，包括蛋白质合成、细胞生长和自噬，TSC2 充当变阻器，通过整合有丝分裂信号与能量可用性来调节 mTOR。有趣的是，TSC2 缺陷的细胞具有异常的氧化还原稳态，我们的初步数据表明 TSC2 是活性氧 (ROS) 抑制 mTOR 所必需的，这使我们推测 TSC2 响应氧化应激而抑制 mTOR。此外，我们发现细胞损伤传感器 ATM 被 ROS 激活，并且在缺乏 ATM 或 TSC2 的情况下，细胞无法响应 ROS 适当抑制 mTOR。众所周知，TSC2 定位于细胞内膜，膜定位调节 TSC2 功能。然而，该肿瘤抑制因子定位的具体内膜尚未确定。重要的是，我们发现 ATM 和 TSC2 都定位于过氧化物酶体，过氧化物酶体是细胞中脂肪酸 2-氧化和 ROS 生成的主要位点。这些数据使我们提出这样的假设：ATM 和 TSC2 参与过氧化物酶体的应激反应途径，该途径响应 ROS 以抑制 mTOR 信号传导。由于 mTOR 是自噬的负调节因子，我们假设 TSC2 介导的 mTOR 抑制响应 ROS 的生理作用是调节自噬和过氧化物酶体周转。 该提议的总体假设是，TSC2 肿瘤抑制因子参与 ATM 下游过氧化物酶体的新型应激反应途径，以抑制 mTOR 信号传导并调节自噬。为了检验这一假设，我们提出以下具体目标： 具体目标 1：检验 TSC2 和该 mTOR 调节节点的组件（TSC2 激活伙伴 TSC1、其 GAP 靶标 Rheb 和 mTOR）定位于过氧化物酶体的假设。具体目标 2：确定在过氧化物酶体上调节 TSC2 功能的信号传导通路。具体目标 3：检验过氧化物酶体 TSC2 抑制 mTOR 以通过 pexophagy 调节自噬和/或过氧化物酶体周转的假设。 本申请中提出的实验将使我们能够检验我们的假设，即 TSC2 参与 ATM 下游过氧化物酶体的一种新型应激反应途径，以抑制 mTOR 并调节细胞自噬。如果这个假设是正确的，并且我们成功地证明了这种过氧化物酶体定位途径具有生理意义，那么这些研究将首次将注意力集中在过氧化物酶体作为信号细胞器上。此外，他们还将为未来的研究奠定基础，以了解过氧化物酶体的细胞信号传导如何参与致癌作用，并为开发针对过氧化物酶体的策略来调节肿瘤细胞中的细胞信号传导和自噬提供可能性。 公共健康相关性：该提案的总体假设是 TSC2 参与过氧化物酶体的一种新型应激反应途径，以抑制 mTOR 信号传导并调节细胞自噬。了解调节自噬过程或影响细胞启动该过程的决定的机制对于癌发生和癌症治疗具有重要意义。更好地了解控制这一过程的机制有可能有助于设计针对该细胞器的过氧化物酶体和信号通路的预防策略。此外，未来它们可能有助于设计治疗方法，限制肿瘤细胞利用自噬作为生存途径的能力和/或促进自噬诱导的程序性细胞死亡以响应治疗。