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.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA129387-05
Application #
8304398
Study Section
Tumor Cell Biology Study Section (TCB)
Program Officer
Spalholz, Barbara A
Project Start
2008-09-22
Project End
2014-07-31
Budget Start
2012-08-01
Budget End
2014-07-31
Support Year
5
Fiscal Year
2012
Total Cost
$316,002
Indirect Cost
$114,727
Name
University of Texas Sw Medical Center Dallas
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
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Wolff, Nicholas C; McKay, Renée M; Brugarolas, James (2014) REDD1/DDIT4-independent mTORC1 inhibition and apoptosis by glucocorticoids in thymocytes. Mol Cancer Res 12:867-77
Hasan, Maroof; Koch, James; Rakheja, Dinesh et al. (2013) Trex1 regulates lysosomal biogenesis and interferon-independent activation of antiviral genes. Nat Immunol 14:61-71
Brugarolas, James (2013) PBRM1 and BAP1 as novel targets for renal cell carcinoma. Cancer J 19:324-32
Pena-Llopis, Samuel; Christie, Alana; Xie, Xian-Jin et al. (2013) Cooperation and antagonism among cancer genes: the renal cancer paradigm. Cancer Res 73:4173-9
Tran, Tram Anh; Kinch, Lisa; Pena-Llopis, Samuel et al. (2013) Platelet-derived growth factor/vascular endothelial growth factor receptor inactivation by sunitinib results in Tsc1/Tsc2-dependent inhibition of TORC1. Mol Cell Biol 33:3762-79
Wolff, Nicholas C; Vega-Rubin-de-Celis, Silvia; Xie, Xian-Jin et al. (2011) Cell-type-dependent regulation of mTORC1 by REDD1 and the tumor suppressors TSC1/TSC2 and LKB1 in response to hypoxia. Mol Cell Biol 31:1870-84
Kucejova, Blanka; Pena-Llopis, Samuel; Yamasaki, Toshinari et al. (2011) Interplay between pVHL and mTORC1 pathways in clear-cell renal cell carcinoma. Mol Cancer Res 9:1255-65
Pena-Llopis, Samuel; Vega-Rubin-de-Celis, Silvia; Schwartz, Jacob C et al. (2011) Regulation of TFEB and V-ATPases by mTORC1. EMBO J 30:3242-58
Kucejova, B; Sunny, N E; Nguyen, A D et al. (2011) Uncoupling hypoxia signaling from oxygen sensing in the liver results in hypoketotic hypoglycemic death. Oncogene 30:2147-60

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