Tumor Suppressor Localization and Function at the Peroxisome

 描述(申请人提供)：过氧化物体是自主复制的细胞器，是细胞内产生ROS的主要来源。在之前的资助期间，我们有两个主要发现，它们构成了这一竞争性更新的基础：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mTORC1信号转导以响应ROS；以及2)TSC信号节点(TSC1、TSC2和Rheb)驻留在过氧酶体上，在那里它被激活以响应ROS的产生。这些发现使我们假设，过氧酶体是TSC和ATM肿瘤抑制因子之间功能相互作用的重要部位，这种相互作用通过调节过氧酶体的选择性自噬(Pexphagy)在维持过氧素体的动态平衡中发挥关键作用。我们假设ATM定位于Peroxisome，在那里它被Peroxisomal ROS激活，并向下游传递信号到TSC2以抑制mTORC1(目标1)。除了TSC肿瘤抑制因子，我们的初步数据表明，ATM激酶还使驻留在过氧体上的PEX5(以及其他)蛋白磷酸化(目标2)，针对它们进行泛素化和自噬适配器蛋白的识别，以招募自噬小体到过氧体并介导吞噬(目标3)。总之，本申请中提出的研究将是第一次展示ATM在过氧化酶体上的信号转导，并定义ATM和TSC肿瘤抑制因子相互作用的新功能位点，对于理解这些肿瘤抑制因子在过氧化体稳态和维持细胞氧化还原平衡中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.