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Powis K, De Virgilio C. Conserved regulators of Rag GTPases orchestrate amino acid-dependent TORC1 signaling. Cell Discov 2016; 2:15049. [PMID: 27462445 PMCID: PMC4860963 DOI: 10.1038/celldisc.2015.49] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 12/02/2015] [Indexed: 12/16/2022] Open
Abstract
The highly conserved target of rapamycin complex 1 (TORC1) is the central component of a signaling network that couples a vast range of internal and external stimuli to cell growth, proliferation and metabolism. TORC1 deregulation is associated with a number of human pathologies, including many cancers and metabolic disorders, underscoring its importance in cellular and organismal growth control. The activity of TORC1 is modulated by multiple inputs; however, the presence of amino acids is a stimulus that is essential for its activation. Amino acid sufficiency is communicated to TORC1 via the highly conserved family of Rag GTPases, which assemble as heterodimeric complexes on lysosomal/vacuolar membranes and are regulated by their guanine nucleotide loading status. Studies in yeast, fly and mammalian model systems have revealed a multitude of conserved Rag GTPase modulators, which have greatly expanded our understanding of amino acid sensing by TORC1. Here we review the major known modulators of the Rag GTPases, focusing on recent mechanistic insights that highlight the evolutionary conservation and divergence of amino acid signaling to TORC1.
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Affiliation(s)
- Katie Powis
- Department of Biology, University of Fribourg , Fribourg, Switzerland
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Kira S, Kumano Y, Ukai H, Takeda E, Matsuura A, Noda T. Dynamic relocation of the TORC1-Gtr1/2-Ego1/2/3 complex is regulated by Gtr1 and Gtr2. Mol Biol Cell 2015; 27:382-96. [PMID: 26609069 PMCID: PMC4713139 DOI: 10.1091/mbc.e15-07-0470] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 11/19/2015] [Indexed: 11/29/2022] Open
Abstract
Ego2 is characterized as a new subunit of Ego protein complex (the yeast Ragulaor counterpart) that is a scaffold of Gtr (the yeast Rag counterpart) and TORC1. Gtr1 and Gtr2 regulate the dynamic translocation of the Ego/Gtr/TORC1 supercomplex between the vacuolar limiting membrane and perivacuolar foci. This localization shift is closely associated with the TORC1 activity level. TORC1 regulates cellular growth, metabolism, and autophagy by integrating various signals, including nutrient availability, through the small GTPases RagA/B/C/D in mammals and Gtr1/2 in budding yeast. Rag/Gtr is anchored to the lysosomal/vacuolar membrane by the scaffold protein complex Ragulator/Ego. Here we show that Ego consists of Ego1 and Ego3, and novel subunit Ego2. The ∆ego2 mutant exhibited only partial defects both in Gtr1-dependent TORC1 activation and Gtr1 localization on the vacuole. Ego1/2/3, Gtr1/2, and Tor1/Tco89 were colocalized on the vacuole and associated puncta. When Gtr1 was in its GTP-bound form and TORC1 was active, these proteins were preferentially localized on the vacuolar membrane, whereas when Gtr1 was in its GDP-bound form, they were mostly localized on the puncta. The localization of TORC1 to puncta was further facilitated by direct binding to Gtr2, which is involved in suppression of TORC1 activity. Thus regulation of TORC1 activity through Gtr1/Gtr2 is tightly coupled to the dynamic relocation of these proteins.
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Affiliation(s)
- Shintaro Kira
- Center for Frontier Oral Science, Graduate School of Dentistry, Osaka University, Osaka 565-0871, Japan
| | - Yuri Kumano
- Graduate School of Frontier BioSciences, Osaka University, Osaka 565-0871, Japan
| | - Hirofumi Ukai
- Graduate School of Frontier BioSciences, Osaka University, Osaka 565-0871, Japan
| | - Eigo Takeda
- Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Akira Matsuura
- Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Takeshi Noda
- Center for Frontier Oral Science, Graduate School of Dentistry, Osaka University, Osaka 565-0871, Japan Graduate School of Frontier BioSciences, Osaka University, Osaka 565-0871, Japan
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Dutchak PA, Laxman S, Estill SJ, Wang C, Wang Y, Wang Y, Bulut GB, Gao J, Huang LJ, Tu BP. Regulation of Hematopoiesis and Methionine Homeostasis by mTORC1 Inhibitor NPRL2. Cell Rep 2015; 12:371-9. [PMID: 26166573 DOI: 10.1016/j.celrep.2015.06.042] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 05/08/2015] [Accepted: 06/08/2015] [Indexed: 01/23/2023] Open
Abstract
Nitrogen permease regulator-like 2 (NPRL2) is a component of a conserved complex that inhibits mTORC1 (mammalian Target Of Rapamycin Complex 1) in response to amino acid insufficiency. Here, we show that NPRL2 is required for mouse viability and that its absence significantly compromises fetal liver hematopoiesis in developing embryos. Moreover, NPRL2 KO embryos have significantly reduced methionine levels and exhibit phenotypes reminiscent of cobalamin (vitamin B12) deficiency. Consistent with this idea, NPRL2 KO liver and mouse embryonic fibroblasts (MEFs) show defective processing of the cobalamin-transport protein transcobalamin 2, along with impaired lysosomal acidification and lysosomal gene expression. NPRL2 KO MEFs exhibit a significant defect in the cobalamin-dependent synthesis of methionine from homocysteine, which can be rescued by supplementation with cyanocobalamin. Taken together, these findings demonstrate a role for NPRL2 and mTORC1 in the regulation of lysosomal-dependent cobalamin processing, methionine synthesis, and maintenance of cellular re-methylation potential, which are important during hematopoiesis.
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Affiliation(s)
- Paul A Dutchak
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Sunil Laxman
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Sandi Jo Estill
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Chensu Wang
- Simmons Comprehensive Cancer Center and Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-8807, USA
| | - Yun Wang
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Yiguang Wang
- Simmons Comprehensive Cancer Center and Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-8807, USA
| | - Gamze B Bulut
- Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA
| | - Jinming Gao
- Simmons Comprehensive Cancer Center and Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-8807, USA
| | - Lily J Huang
- Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA
| | - Benjamin P Tu
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA.
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Dokudovskaya S, Rout MP. SEA you later alli-GATOR--a dynamic regulator of the TORC1 stress response pathway. J Cell Sci 2015; 128:2219-28. [PMID: 25934700 DOI: 10.1242/jcs.168922] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cells constantly adapt to various environmental changes and stresses. The way in which nutrient and stress levels in a cell feed back to control metabolism and growth are, unsurprisingly, extremely complex, as responding with great sensitivity and speed to the 'feast or famine, slack or stress' status of its environment is a central goal for any organism. The highly conserved target of rapamycin complex 1 (TORC1) controls eukaryotic cell growth and response to a variety of signals, including nutrients, hormones and stresses, and plays the key role in the regulation of autophagy. A lot of attention has been paid recently to the factors in this pathway functioning upstream of TORC1. In this Commentary, we focus on a major, newly discovered upstream regulator of TORC1--the multiprotein SEA complex, also known as GATOR. We describe the structural and functional features of the yeast complex and its mammalian homolog, and their involvement in the regulation of the TORC1 pathway and TORC1-independent processes. We will also provide an overview of the consequences of GATOR deregulation in cancer and other diseases.
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Affiliation(s)
- Svetlana Dokudovskaya
- CNRS UMR 8126, Université Paris-Sud 11, Institut Gustave Roussy, 114, rue Edouard Vaillant, 94805, Villejuif, France
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
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Delorme-Axford E, Guimaraes RS, Reggiori F, Klionsky DJ. The yeast Saccharomyces cerevisiae: an overview of methods to study autophagy progression. Methods 2014; 75:3-12. [PMID: 25526918 DOI: 10.1016/j.ymeth.2014.12.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 11/26/2014] [Accepted: 12/04/2014] [Indexed: 12/15/2022] Open
Abstract
Macroautophagy (hereafter autophagy) is a highly evolutionarily conserved process essential for sustaining cellular integrity, homeostasis, and survival. Most eukaryotic cells constitutively undergo autophagy at a low basal level. However, various stimuli, including starvation, organelle deterioration, stress, and pathogen infection, potently upregulate autophagy. The hallmark morphological feature of autophagy is the formation of the double-membrane vesicle known as the autophagosome. In yeast, flux through the pathway culminates in autophagosome-vacuole fusion, and the subsequent degradation of the resulting autophagic bodies and cargo by vacuolar hydrolases, followed by efflux of the breakdown products. Importantly, aberrant autophagy is associated with diverse human pathologies. Thus, there is a need for ongoing work in this area to further understand the cellular factors regulating this process. The field of autophagy research has grown exponentially in recent years, and although numerous model organisms are being used to investigate autophagy, the baker's yeast Saccharomyces cerevisiae remains highly relevant, as there are significant and unique benefits to working with this organism. In this review, we will focus on the current methods available to evaluate and monitor autophagy in S. cerevisiae, which in several cases have also been subsequently exploited in higher eukaryotes.
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Affiliation(s)
| | - Rodrigo Soares Guimaraes
- Department of Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; Department of Cell Biology, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Fulvio Reggiori
- Department of Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; Department of Cell Biology, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Daniel J Klionsky
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, United States.
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