Regulation of the mTOR Pathway by Hypoxia and the REDD1 Protein

描述（由申请人提供）：哺乳动物雷帕霉素靶蛋白复合物1（mTORC 1）是细胞生长和代谢的关键调节因子，其将细胞内和细胞外的各种信号与蛋白质翻译机制整合在一起。来自生长因子和能量储存的信号通过结节性硬化症复合物蛋白1（TSC 1）和2（TSC 2）传递到mTORC 1，其形成具有肿瘤抑制功能的复合物（TSC 1/TSC 2）。我们已经发现，mTORC 1通过氧水平的调节也需要TSC 1/TSC 2复合物。在TSC 1/TSC 2缺陷细胞中，由于缺氧而不能抑制mTORC 1，导致细胞增殖异常，并可能导致肿瘤生长。最近，我们建立了基因调控的发展和DNA损伤1（REDD 1），一个迄今为止未知的功能基因，是必要的mTORC 1抑制缺氧。REDD 1在缺氧时被转录诱导，REDD 1过表达足以抑制mTORC 1。REDD 1编码一种保守的25 kDa蛋白，没有可识别的结构或功能结构域，与其他已知功能的蛋白没有同源性。在此，数据显示，REDD 1形成一个复杂的，包含一个单一的REDD 1单体和实验提出评估的作用，复杂的REDD 1信号。结构-功能分析揭示了REDD 1中存在两个功能所需的结构域，并通过实验来测试这些结构域的作用。此外，实验概述，以评估是否REDD 1复合物调节mTORC 1直接，或通过TSC 1/TSC 2。初步的数据也提出了表征REDD 1的亚细胞定位和实验提出评估机制，管理REDD 1亚细胞分布及其功能意义。最后，一种新的小鼠品系已经产生，并概述了实验，以表征REDD 1在小鼠缺氧信号传导中的作用的调节和机制。mTORC 1在许多病理条件下被解除调节，了解mTORC 1如何受缺氧和REDD 1调节可能对人类健康有影响。 公共卫生相关性：该项目旨在了解细胞适应环境变化的机制。特别是，我们有兴趣了解细胞如何适应低氧水平。该过程涉及抑制称为雷帕霉素复合物1（mTORC 1）的哺乳动物靶蛋白复合物，并且该复合物涉及多种病理过程。事实上，mTORC 1抑制剂已被FDA批准用于（1）治疗癌症，（2）预防移植排斥反应，（3）预防冠状动脉支架闭塞。因此，了解mTORC 1是如何调节的对人类健康具有深远的意义。

DESCRIPTION (provided by applicant): Mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of cell growth and metabolism that integrates a variety of signals, both intracellular and extracellular, with the protein translation machinery. Signals from growth factors and energy stores are relayed to mTORC1 through the tuberous sclerosis complex proteins 1 (TSC1) and 2 (TSC2), which form a complex (TSC1/TSC2) with tumor suppressor function. We have discovered that mTORC1 regulation by oxygen levels also requires the TSC1/TSC2 complex. Failure to inhibit mTORC1 in TSC1/TSC2-deficient cells in response to hypoxia results in abnormal cell proliferation and might contribute to tumor growth. Recently, we established that the gene regulated in development and DNA damage 1 (REDD1), a gene of hitherto unknown function, was necessary for mTORC1 inhibition by hypoxia. REDD1 is transcriptionally induced in response to hypoxia and REDD1 overexpression is sufficient to inhibit mTORC1. REDD1 encodes a conserved 25 kDa protein with no recognizable structural or functional domains and no homology to other proteins of known function. Herein, data is presented showing that REDD1 forms a complex that contains a single REDD1 monomer and experiments are proposed to evaluate the role of the complex in REDD1 signaling. Structure-function analyses have revealed the existence of two domains in REDD1 that are required for function, and experiments are presented to test how these domains act. In addition, experiments are outlined to assess whether the REDD1 complex regulates mTORC1 directly, or through TSC1/TSC2. Preliminary data is also presented characterizing the subcellular localization of REDD1 and experiments are proposed to evaluate the mechanism that governs REDD1 subcellular distribution and its functional significance. Finally, a novel mouse strain has been generated and experiments are outlined to characterize the regulation and mechanism of REDD1 action in hypoxia signaling in the mouse. mTORC1 is deregulated in many pathological conditions and understanding how mTORC1 is regulated by hypoxia and REDD1 might have implications for human health. PUBLIC HEALTH RELEVANCE: This project seeks to understand the mechanism whereby cells adapt to changes in their environment. In particular we are interested in understanding how cells adapt to low oxygen levels. This process involves the inhibition of a cellular protein complex called mammalian target of rapamycin complex 1 (mTORC1) and this complex is implicated in multiple pathological processes. mTORC1 inhibitors have, in fact, been approved by the FDA for (1) the treatment of cancer, (2) to prevent transplant rejection, and (3) to prevent coronary artery stent occlusions. Thus, understanding how mTORC1 is regulated has profound implications for human health.