Regulation of the mTOR Pathway by Hypoxia and the REDD1 Protein

描述(申请人提供)：哺乳动物雷帕霉素复合体靶标1(MTORC1)是细胞生长和代谢的关键调节因子，它整合了多种信号，包括细胞内和细胞外的信号，以及蛋白质翻译机制。生长因子和能量储存的信号通过结节性硬化症复合体蛋白1(TSC1)和2(TSC2)传递到mTORC1，这两个蛋白形成了具有肿瘤抑制功能的复合体(TSC1/TSC2)。我们发现，氧水平对mTORC1的调节也需要TSC1/TSC2复合体。缺氧不能抑制TSC1/TSC2缺陷细胞的mTORC1会导致细胞的异常增殖，并可能导致肿瘤的生长。最近，我们发现发育和DNA损伤调控基因1(Redd1)是缺氧抑制mTORC1所必需的，该基因的功能尚不清楚。在低氧条件下，Redd1在转录水平上被诱导，而Redd1的过表达足以抑制mTORC1。Redd1编码一个保守的25 kDa蛋白，没有可识别的结构或功能结构域，也没有与其他已知功能蛋白的同源性。在这里，提供的数据表明，Redd1形成一个包含单个Redd1单体的复合体，并建议通过实验来评估该复合体在Redd1信号转导中的作用。结构-功能分析揭示了Redd1中存在两个功能所需的结构域，并通过实验测试了这些结构域的作用。此外，还概述了评估Redd1复合体是直接调节mTORC1还是通过TSC1/TSC2调节mTORC1的实验。还提供了初步的数据来表征Redd1的亚细胞定位，并提出了实验来评估支配Redd1亚细胞分布的机制及其功能意义。最后，我们产生了一个新的小鼠品系，并概述了Redd1在小鼠缺氧信号中的调节和作用机制的实验。MTORC1在许多病理条件下被解除调控，了解mTORC1如何受到缺氧和Redd1的调节可能对人类健康有影响。 与公共健康相关：该项目试图了解细胞适应环境变化的机制。特别是，我们对了解细胞如何适应低氧水平感兴趣。这一过程涉及到一种被称为哺乳动物雷帕霉素靶复合体1(MTORC1)的细胞蛋白复合体的抑制，该复合体参与了多种病理过程。事实上，mTORC1抑制剂已被FDA批准用于(1)治疗癌症，(2)防止移植排斥反应，(3)防止冠状动脉支架闭塞。因此，了解mTORC1是如何被调控的对人类健康具有深远的影响。

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.