Tumor Suppressor Localization and Function at the Peroxisome

 描述（由申请人提供）：过氧化物酶体是自主复制的细胞器，是细胞中ROS产生的主要来源。在上一个资助期，我们有两个重大发现，构成了这次竞争性续约的基础：1）细胞质中的DNA修复激酶ATM“月光”，在那里它向TSC肿瘤抑制因子发出信号以抑制响应于ROS的mTORC 1信号传导，和2）TSC信号传导节点TSC1、TSC2和Rheb）存在于过氧化物酶体中，在那里它响应于该细胞器的ROS产生而被激活。这些发现使我们假设过氧化物酶体是TSC和ATM肿瘤抑制因子之间功能相互作用的输入位点，并且这种相互作用通过调节过氧化物酶体的选择性自噬（pexophagy）在维持过氧化物酶体稳态中起关键作用。我们假设ATM定位于过氧化物酶体，在那里它被过氧化物酶体ROS激活，并向TSC 2下游发出信号以抑制mTORC 1（Aim 1）。除了TSC肿瘤抑制因子之外，我们的初步数据表明ATM激酶还磷酸化驻留在过氧化物酶体中的PEX5（以及可能的其他）蛋白质（Aim 2），靶向它们进行泛素化和自噬衔接蛋白的识别，以将自噬体募集到过氧化物酶体并介导自噬（Aim 3）。总之，在本申请中提出的研究将是第一个证明ATM信号在过氧化物酶体，并定义新的功能位点的ATM和TSC肿瘤抑制剂的相互作用，理解这些肿瘤抑制剂在过氧化物酶体稳态和维持细胞氧化还原平衡的作用具有重要意义。

 DESCRIPTION (provided by applicant): Peroxisomes are autonomously replicating organelles, and a major source of ROS generation in the cell. In the previous funding period, we made two major discoveries that form the basis for this competitive renewal: 1) the DNA repair kinase ATM "moonlights" in the cytoplasm where it signals to the TSC tumor suppressor to repress mTORC1 signaling in response to ROS and 2) the TSC signaling node (TSC1, TSC2 and Rheb) is resident at the peroxisome, where it is activated in response to ROS generation by this organelle. These findings have led us to hypothesize that the peroxisome is an import site for functional interaction between the TSC and ATM tumor suppressors, and that this interaction plays a key role in maintaining peroxisomal homeostasis by regulating selective autophagy of peroxisome (pexophagy). We hypothesize that ATM localizes to the peroxisome, where it is activated by peroxisomal ROS and signals downstream to TSC2 to suppress mTORC1 (Aim 1). In addition to the TSC tumor suppressor, our Preliminary Data suggest the ATM kinase also phosphorylates PEX5 (and perhaps other) proteins resident at the peroxisome (Aim 2), targeting them for ubiquitination and recognition by autophagy adaptor proteins to recruit the autophagosome to the peroxisome and mediate pexophagy (Aim 3). Together, the studies proposed in this application would be the first to demonstrate ATM signaling at the peroxisome, and to define new functional site for interaction of the ATM and TSC tumor suppressors, with important implications for understanding the role of these tumor suppressors in peroxisome homeostasis and maintenance of cellular redox balance.