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Loissell-Baltazar YA, Dokudovskaya S. SEA and GATOR 10 Years Later. Cells 2021; 10:cells10102689. [PMID: 34685669 PMCID: PMC8534245 DOI: 10.3390/cells10102689] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/30/2021] [Accepted: 10/03/2021] [Indexed: 12/17/2022] Open
Abstract
The SEA complex was described for the first time in yeast Saccharomyces cerevisiae ten years ago, and its human homologue GATOR complex two years later. During the past decade, many advances on the SEA/GATOR biology in different organisms have been made that allowed its role as an essential upstream regulator of the mTORC1 pathway to be defined. In this review, we describe these advances in relation to the identification of multiple functions of the SEA/GATOR complex in nutrient response and beyond and highlight the consequence of GATOR mutations in cancer and neurodegenerative diseases.
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2
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Phithakrotchanakoon C, Puseenam A, Kruasuwan W, Likhitrattanapisal S, Phaonakrop N, Roytrakul S, Ingsriswang S, Tanapongpipat S, Roongsawang N. Identification of proteins responsive to heterologous protein production in thermotolerant methylotrophic yeast Ogataea thermomethanolica TBRC656. Yeast 2021; 38:316-325. [PMID: 33445217 DOI: 10.1002/yea.3548] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 01/04/2021] [Accepted: 01/05/2021] [Indexed: 11/09/2022] Open
Abstract
The thermotolerant methylotrophic yeast Ogataea thermomethanolica TBRC656 is a potential host for heterologous protein production. However, overproduction of heterologous protein can induce cellular stress and limit the level of its secretion. To improve the secretion of heterologous protein, we identified the candidate proteins with altered production during production of heterologous protein in O. thermomethanolica by using a label-free comparative proteomic approach. Four hundred sixty-four proteins with various biological functions showed differential abundance between O. thermomethanolica expressing fungal xylanase (OT + Xyl) and a control strain. The induction of proteins in transport and proteasomal proteolysis was prominently observed. Eight candidate proteins involved in cell wall biosynthesis (Chs3, Gas4), chaperone (Sgt2, Pex19), glycan metabolism (Csf1), protein transport (Ypt35), and vacuole and protein sorting (Cof1, Npr2) were mutated by a CRISPR/Cas9 approach. An Sgt2 mutant showed higher phytase and xylanase activity compared with the control strain (13%-20%), whereas mutants of other genes including Cof1, Pex19, Gas4, and Ypt35 showed lower xylanase activity compared with the control strain (15%-25%). In addition, an Npr2 mutant showed defective growth, while overproduction of Npr2 enhanced xylanase activity. These results reveal genes that can be mutated to modulate heterologous protein production and growth of O. thermomethanolica TBRC656.
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Affiliation(s)
- Chitwadee Phithakrotchanakoon
- Microbial Systems and Computational Biology Research Team, Thailand Bioresource Research Center, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Aekkachai Puseenam
- Microbial Cell Factory Research Team, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Worarat Kruasuwan
- Microbial Cell Factory Research Team, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Somsak Likhitrattanapisal
- Microbial Systems and Computational Biology Research Team, Thailand Bioresource Research Center, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Narumon Phaonakrop
- Functional Proteomics Technology, Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Sittiruk Roytrakul
- Functional Proteomics Technology, Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Supawadee Ingsriswang
- Microbial Systems and Computational Biology Research Team, Thailand Bioresource Research Center, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Sutipa Tanapongpipat
- Microbial Cell Factory Research Team, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
| | - Niran Roongsawang
- Microbial Cell Factory Research Team, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, Thailand
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Wei Y, Bettedi L, Ting CY, Kim K, Zhang Y, Cai J, Lilly MA. The GATOR complex regulates an essential response to meiotic double-stranded breaks in Drosophila. eLife 2019; 8:e42149. [PMID: 31650955 PMCID: PMC6834368 DOI: 10.7554/elife.42149] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 10/13/2019] [Indexed: 01/18/2023] Open
Abstract
The TORC1 regulator GATOR1/SEACIT controls meiotic entry and early meiotic events in yeast. However, how metabolic pathways influence meiotic progression in metazoans remains poorly understood. Here we examine the role of the TORC1 regulators GATOR1 and GATOR2 in the response to meiotic double-stranded breaks (DSB) during Drosophila oogenesis. We find that in mutants of the GATOR2 component mio, meiotic DSBs trigger the constitutive downregulation of TORC1 activity and a permanent arrest in oocyte growth. Conversely, in GATOR1 mutants, high TORC1 activity results in the delayed repair of meiotic DSBs and the hyperactivation of p53. Unexpectedly, we found that GATOR1 inhibits retrotransposon expression in the presence of meiotic DSBs in a pathway that functions in parallel to p53. Thus, our studies have revealed a link between oocyte metabolism, the repair of meiotic DSBs and retrotransposon expression.
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Affiliation(s)
- Youheng Wei
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
- College of Bioscience and BiotechnologyYangzhou UniversityYangzhouChina
| | - Lucia Bettedi
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Chun-Yuan Ting
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Kuikwon Kim
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Yingbiao Zhang
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Jiadong Cai
- College of Bioscience and BiotechnologyYangzhou UniversityYangzhouChina
| | - Mary A Lilly
- Cell Biology and Neurobiology BranchNational Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
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4
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Chen J, Sutter BM, Shi L, Tu BP. GATOR1 regulates nitrogenic cataplerotic reactions of the mitochondrial TCA cycle. Nat Chem Biol 2017; 13:1179-1186. [PMID: 28920930 PMCID: PMC5659745 DOI: 10.1038/nchembio.2478] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 08/10/2017] [Indexed: 12/14/2022]
Abstract
The GATOR1/SEACIT complex consisting of Iml1-Npr2-Npr3 inhibits Target of Rapamycin Complex 1 (TORC1) in response to amino acid insufficiency. In glucose medium, Saccharomyces cerevisiae mutants lacking the function of this complex grow poorly in the absence of amino acid supplementation, despite hallmarks of increased TORC1 signaling. Such mutants perceive they are amino acid-replete and thus repress metabolic activities that are important for achieving this state. We find that npr2Δ mutants have defective mitochondrial TCA cycle activity and retrograde response. Supplementation of glutamine, and especially aspartate, which are nitrogen-containing forms of TCA cycle intermediates, rescue growth of npr2Δ mutants. These amino acids are then consumed in biosynthetic pathways that require nitrogen to support proliferative metabolism. Our findings reveal that negative regulators of TORC1 such as GATOR1/SEACIT regulate the cataplerotic synthesis of these amino acids from the TCA cycle in tune with the amino acid and nitrogen status of cells.
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Affiliation(s)
- Jun Chen
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Benjamin M Sutter
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Lei Shi
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Benjamin P Tu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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5
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Abstract
For almost all cells, nutrient availability, from glucose to amino acids, dictates their growth or developmental programs. This nutrient availability is closely coupled to the overall intracellular metabolic state of the cell. Therefore, cells have evolved diverse, robust and versatile modules to sense intracellular metabolic states, activate signaling outputs and regulate outcomes to these states. Yet, signaling and metabolism have been viewed as important but separate. This short review attempts to position aspects of intracellular signaling from a metabolic perspective, highlighting how conserved, core principles of metabolic sensing and signaling can emerge from an understanding of metabolic regulation. I briefly explain the nature of metabolic sensors, using the example of the AMP activated protein kinase (AMPK) as an "energy sensing" hub. Subsequently, I explore how specific central metabolites, particularly acetyl-CoA, but also S -adenosyl methionine and SAICAR, can act as signaling molecules. I extensively illustrate the nature of a metabolic signaling hub using the specific example of the Target of Rapamycin Complex 1 (TORC1), and amino acid sensing. A highlight is the emergence of the lysosome/vacuole as a metabolic and signaling hub. Finally, the need to expand our understanding of the intracellular dynamics (in concentration and localization) of several metabolites, and their signaling hubs is emphasized.
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Affiliation(s)
- Sunil Laxman
- Institute for Stem Cell Biology and Regenerative Medicine (inStem), NCBS Campus, GKVK, Bellary Road, Bangalore 560065, India
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6
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Multiple Targets on the Gln3 Transcription Activator Are Cumulatively Required for Control of Its Cytoplasmic Sequestration. G3-GENES GENOMES GENETICS 2016; 6:1391-408. [PMID: 26976442 PMCID: PMC4856090 DOI: 10.1534/g3.116.027615] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A remarkable characteristic of nutritional homeostatic mechanisms is the breadth of metabolite concentrations to which they respond, and the resolution of those responses; adequate but rarely excessive. Two general ways of achieving such exquisite control are known: stoichiometric mechanisms where increasing metabolite concentrations elicit proportionally increasing responses, and the actions of multiple independent metabolic signals that cumulatively generate appropriately measured responses. Intracellular localization of the nitrogen-responsive transcription activator, Gln3, responds to four distinct nitrogen environments: nitrogen limitation or short-term starvation, i.e., nitrogen catabolite repression (NCR), long-term starvation, glutamine starvation, and rapamycin inhibition of mTorC1. We have previously identified unique sites in Gln3 required for rapamycin-responsiveness, and Gln3-mTor1 interaction. Alteration of the latter results in loss of about 50% of cytoplasmic Gln3 sequestration. However, except for the Ure2-binding domain, no evidence exists for a Gln3 site responsible for the remaining cytoplasmic Gln3-Myc13 sequestration in nitrogen excess. Here, we identify a serine/threonine-rich (Gln3477–493) region required for effective cytoplasmic Gln3-Myc13 sequestration in excess nitrogen. Substitutions of alanine but not aspartate for serines in this peptide partially abolish cytoplasmic Gln3 sequestration. Importantly, these alterations have no effect on the responses of Gln3-Myc13 to rapamycin, methionine sulfoximine, or limiting nitrogen. However, cytoplasmic Gln3-Myc13 sequestration is additively, and almost completely, abolished when mutations in the Gln3-Tor1 interaction site are combined with those in Gln3477–493 cytoplasmic sequestration site. These findings clearly demonstrate that multiple individual regulatory pathways cumulatively control cytoplasmic Gln3 sequestration.
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7
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The TORC1 effector kinase Npr1 fine tunes the inherent activity of the Mep2 ammonium transport protein. Nat Commun 2015; 5:3101. [PMID: 24476960 DOI: 10.1038/ncomms4101] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 12/13/2013] [Indexed: 12/30/2022] Open
Abstract
The TORC1 complex controls cell growth upon integrating nutritional signals including amino-acid availability. TORC1 notably adapts the plasma membrane protein content by regulating arrestin-mediated endocytosis of amino-acid transporters. Here we demonstrate that TORC1 further fine tunes the inherent activity of the ammonium transport protein, Mep2, a yeast homologue of mammalian Rhesus factors, independently of arrestin-mediated endocytosis. The TORC1 effector kinase Npr1 and the upstream TORC1 regulator Npr2 control Mep2 transport activity by phospho-silencing a carboxy-terminal autoinhibitory domain. Under poor nitrogen supply, Npr1 enables Mep2 S457 phosphorylation and thus ammonium transport activity. Supplementation of the preferred nitrogen source glutamine leads to Mep2 inactivation and instant S457 dephosphorylation via plasma membrane Psr1 and Psr2 redundant phosphatases. This study underscores that TORC1 also adjusts nutrient permeability to regulate cell growth in a fast and flexible response to environmental perturbation, establishing a hierarchy in the transporters to be degraded, inactivated or maintained active at the plasma membrane.
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8
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Huang N, Cheng S, Mi X, Tian Q, Huang Q, Wang F, Xu Z, Xie Z, Chen J, Cheng Y. Downregulation of nitrogen permease regulator like-2 activates PDK1-AKT1 and contributes to the malignant growth of glioma cells. Mol Carcinog 2015; 55:1613-1626. [PMID: 26455908 DOI: 10.1002/mc.22413] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 08/20/2015] [Accepted: 08/31/2015] [Indexed: 12/24/2022]
Affiliation(s)
- Ning Huang
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Si Cheng
- Department of Orthopaedics; The First Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Xiujuan Mi
- Department of neurology; The First Affiliated Hospital of Chongqing Medical University; Chongqing China
- Chongqing Key Laboratory of Neurology; Chongqing China
| | - Qin Tian
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
- Institute of Life Sciences; Chongqing Medical University; Chongqing China
| | - Qin Huang
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Feng Wang
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Zongye Xu
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Zongyi Xie
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Jin Chen
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
| | - Yuan Cheng
- Department of Neurosurgery; The Second Affiliated Hospital of Chongqing Medical University; Chongqing China
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9
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Nakatsukasa K, Okumura F, Kamura T. Proteolytic regulation of metabolic enzymes by E3 ubiquitin ligase complexes: lessons from yeast. Crit Rev Biochem Mol Biol 2015; 50:489-502. [PMID: 26362128 DOI: 10.3109/10409238.2015.1081869] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Eukaryotic organisms use diverse mechanisms to control metabolic rates in response to changes in the internal and/or external environment. Fine metabolic control is a highly responsive, energy-saving process that is mediated by allosteric inhibition/activation and/or reversible modification of preexisting metabolic enzymes. In contrast, coarse metabolic control is a relatively long-term and expensive process that involves modulating the level of metabolic enzymes. Coarse metabolic control can be achieved through the degradation of metabolic enzymes by the ubiquitin-proteasome system (UPS), in which substrates are specifically ubiquitinated by an E3 ubiquitin ligase and targeted for proteasomal degradation. Here, we review select multi-protein E3 ligase complexes that directly regulate metabolic enzymes in Saccharomyces cerevisiae. The first part of the review focuses on the endoplasmic reticulum (ER) membrane-associated Hrd1 and Doa10 E3 ligase complexes. In addition to their primary roles in the ER-associated degradation pathway that eliminates misfolded proteins, recent quantitative proteomic analyses identified native substrates of Hrd1 and Doa10 in the sterol synthesis pathway. The second part focuses on the SCF (Skp1-Cul1-F-box protein) complex, an abundant prototypical multi-protein E3 ligase complex. While the best-known roles of the SCF complex are in the regulation of the cell cycle and transcription, accumulating evidence indicates that the SCF complex also modulates carbon metabolism pathways. The increasing number of metabolic enzymes whose stability is directly regulated by the UPS underscores the importance of the proteolytic regulation of metabolic processes for the acclimation of cells to environmental changes.
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Affiliation(s)
- Kunio Nakatsukasa
- a Division of Biological Sciences , Graduate School of Science, Nagoya University , Nagoya , Aichi , Japan
| | - Fumihiko Okumura
- a Division of Biological Sciences , Graduate School of Science, Nagoya University , Nagoya , Aichi , Japan
| | - Takumi Kamura
- a Division of Biological Sciences , Graduate School of Science, Nagoya University , Nagoya , Aichi , Japan
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10
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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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11
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Laxman S, Sutter BM, Shi L, Tu BP. Npr2 inhibits TORC1 to prevent inappropriate utilization of glutamine for biosynthesis of nitrogen-containing metabolites. Sci Signal 2014; 7:ra120. [PMID: 25515537 DOI: 10.1126/scisignal.2005948] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cells must be capable of switching between growth and autophagy in unpredictable nutrient environments. The conserved Npr2 protein complex (comprising Iml1, Npr2, and Npr3; also called SEACIT) inhibits target of rapamycin complex 1 (TORC1) kinase signaling, which inhibits autophagy in nutrient-rich conditions. In yeast cultured in media with nutrient limitations that promote autophagy and inhibit growth, loss of Npr2 enables cells to bypass autophagy and proliferate. We determined that Npr2-deficient yeast had a metabolic state distinct from that of wild-type yeast when grown in minimal media containing ammonium as a nitrogen source and a nonfermentable carbon source (lactate). Unlike wild-type yeast, which accumulated glutamine, Npr2-deficient yeast metabolized glutamine into nitrogen-containing metabolites and maintained a high concentration of S-adenosyl methionine (SAM). Moreover, in wild-type yeast grown in these nutrient-limited conditions, supplementation with methionine stimulated glutamine consumption for synthesis of nitrogenous metabolites, demonstrating integration of a sulfur-containing amino acid cue and nitrogen utilization. These data revealed the metabolic basis by which the Npr2 complex regulates cellular homeostasis and demonstrated a key function for TORC1 in regulating the synthesis and utilization of glutamine as a nitrogen source.
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Affiliation(s)
- Sunil Laxman
- Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Benjamin M Sutter
- Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Lei Shi
- Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA
| | - Benjamin P Tu
- Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA.
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12
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TORC1 regulators Iml1/GATOR1 and GATOR2 control meiotic entry and oocyte development in Drosophila. Proc Natl Acad Sci U S A 2014; 111:E5670-7. [PMID: 25512509 DOI: 10.1073/pnas.1419156112] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In single-cell eukaryotes the pathways that monitor nutrient availability are central to initiating the meiotic program and gametogenesis. In Saccharomyces cerevisiae an essential step in the transition to the meiotic cycle is the down-regulation of the nutrient-sensitive target of rapamycin complex 1 (TORC1) by the increased minichromosome loss 1/ GTPase-activating proteins toward Rags 1 (Iml1/GATOR1) complex in response to amino acid starvation. How metabolic inputs influence early meiotic progression and gametogenesis remains poorly understood in metazoans. Here we define opposing functions for the TORC1 regulatory complexes Iml1/GATOR1 and GATOR2 during Drosophila oogenesis. We demonstrate that, as is observed in yeast, the Iml1/GATOR1 complex inhibits TORC1 activity to slow cellular metabolism and drive the mitotic/meiotic transition in developing ovarian cysts. In iml1 germline depletions, ovarian cysts undergo an extra mitotic division before meiotic entry. The TORC1 inhibitor rapamycin can suppress this extra mitotic division. Thus, high TORC1 activity delays the mitotic/meiotic transition. Conversely, mutations in Tor, which encodes the catalytic subunit of the TORC1 complex, result in premature meiotic entry. Later in oogenesis, the GATOR2 components Mio and Seh1 are required to oppose Iml1/GATOR1 activity to prevent the constitutive inhibition of TORC1 and a block to oocyte growth and development. To our knowledge, these studies represent the first examination of the regulatory relationship between the Iml1/GATOR1 and GATOR2 complexes within the context of a multicellular organism. Our data imply that the central role of the Iml1/GATOR1 complex in the regulation of TORC1 activity in the early meiotic cycle has been conserved from single cell to multicellular organisms.
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13
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Wei Y, Lilly MA. The TORC1 inhibitors Nprl2 and Nprl3 mediate an adaptive response to amino-acid starvation in Drosophila. Cell Death Differ 2014; 21:1460-8. [PMID: 24786828 DOI: 10.1038/cdd.2014.63] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/02/2014] [Accepted: 04/03/2014] [Indexed: 01/09/2023] Open
Abstract
Target of rapamycin complex 1 (TORC1) is a master regulator of metabolism in eukaryotes that integrates information from multiple upstream signaling pathways. In yeast, the Nitrogen permease regulators 2 and 3 (Npr2 and Npr3) mediate an essential response to amino-acid limitation upstream of TORC1. In mammals, the Npr2 ortholog, Nprl2, is a putative tumor suppressor gene that inhibits cell growth and enhances sensitivity to numerous anticancer drugs including cisplatin. However, the precise role of Nprl2 and Nprl3 in the regulation of metabolism in metazoans remains poorly defined. Here we demonstrate that the central importance of Nprl2 and Nprl3 in the response to amino-acid starvation has been conserved from single celled to multicellular animals. We find that in Drosophila Nprl2 and Nprl3 physically interact and are targeted to lysosomes and autolysosomes. Using oogenesis as a model system, we show that Nprl2 and Nprl3 inhibit TORC1 signaling in the female germline in response to amino-acid starvation. Moreover, the inhibition TORC1 by Nprl2/3 is critical to the preservation of female fertility during times of protein scarcity. In young egg chambers the failure to downregulate TORC1 in response to amino-acid limitation triggers apoptosis. Thus, our data suggest the presence of a metabolic checkpoint that initiates a cell death program when TORC1 activity remains inappropriately high during periods of amino-acid and/or nutrient scarcity in oogenesis. Finally, we demonstrate that Nprl2/3 work in concert with the TORC1 inhibitors Tsc1/2 to fine tune TORC1 activity during oogenesis and that Tsc1 is a critical downstream effector of Akt1 in the female germline.
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Affiliation(s)
- Y Wei
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - M A Lilly
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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14
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Changes in cell morphology are coordinated with cell growth through the TORC1 pathway. Curr Biol 2013; 23:1269-79. [PMID: 23810534 DOI: 10.1016/j.cub.2013.05.035] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 04/10/2013] [Accepted: 05/21/2013] [Indexed: 11/21/2022]
Abstract
BACKGROUND Growth rate is determined not only by extracellular cues such as nutrient availability but also by intracellular processes. Changes in cell morphology in budding yeast, mediated by polarization of the actin cytoskeleton, have been shown to reduce cell growth. RESULTS Here we demonstrate that polarization of the actin cytoskeleton inhibits the highly conserved Target of Rapamycin Complex 1 (TORC1) pathway. This downregulation is suppressed by inactivation of the TORC1 pathway regulatory Iml1 complex, which also regulates TORC1 during nitrogen starvation. We further demonstrate that attenuation of growth is important for cell recovery after conditions of prolonged polarized growth. CONCLUSIONS Our results indicate that extended periods of polarized growth inhibit protein synthesis, mass accumulation, and the increase in cell size at least in part through inhibiting the TORC1 pathway. We speculate that this mechanism serves to coordinate the ability of cells to increase in size with their biosynthetic capacity.
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15
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Abstract
Amino acid availability is a rate-limiting factor in the regulation of protein synthesis. When amino acid supplies become restricted, mammalian cells employ homeostatic mechanisms to rapidly inhibit processes such as protein synthesis, which demands high levels of amino acids. Muscle cells in particular are subject to high protein turnover rates to maintain amino acid homeostasis. Mammalian target of rapamycin complex 1 (mTORC1) is an evolutionary conserved multiprotein complex that coordinates a network of signaling cascades and functions as a key mediator of protein translation, gene transcription, and autophagy. Signal transduction through mTORC1, which is centrally involved in muscle growth through enhanced protein translation, is governed by intracellular amino acid supply. The branched-chain amino acid leucine is critical for muscle growth and acts in part through activation of mTORC1. Recent research has revealed that mTORC1 signaling is coordinated primarily at the lysosomal membranes. This discovery has sparked a wealth of research in this field, revealing several different signaling molecules involved in transducing the amino acid signal to mTORC1, including the Rag GTPases, MAP4K3, and Vps34/ULK1. This review evaluates the current knowledge regarding cellular mechanisms that control and sense the intracellular amino acid pool. We discuss the role of leucine and mTORC1 in the regulation of amino acid transport via the system L and system A transporters such as LAT1 and SNAT2, as well as protein degradation via autophagic and proteasomal pathways. We also describe the complexities of energy homeostasis via AMPK and cell receptor-mediated growth signals that also converge on mTORC1. Leucine is a particularly potent regulator of protein turnover, to the extent where leucine stimulation alone is sufficient to stimulate mTORC1 signal transduction. The significance of leucine in this context is not yet known; however, recent advancements in this area will also be covered within this review.
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Affiliation(s)
- Kayleigh M Dodd
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, Wales, UK
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16
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Affiliation(s)
- Alfred C O Vertegaal
- Department of Molecular Cell Biology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands.
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17
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Morin N, Cescut J, Beopoulos A, Lelandais G, Le Berre V, Uribelarrea JL, Molina-Jouve C, Nicaud JM. Transcriptomic analyses during the transition from biomass production to lipid accumulation in the oleaginous yeast Yarrowia lipolytica. PLoS One 2011; 6:e27966. [PMID: 22132183 PMCID: PMC3222671 DOI: 10.1371/journal.pone.0027966] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/28/2011] [Indexed: 12/12/2022] Open
Abstract
We previously developed a fermentation protocol for lipid accumulation in the oleaginous yeast Y. lipolytica. This process was used to perform transcriptomic time-course analyses to explore gene expression in Y. lipolytica during the transition from biomass production to lipid accumulation. In this experiment, a biomass concentration of 54.6 g(CDW)/l, with 0.18 g/g(CDW) lipid was obtained in ca. 32 h, with low citric acid production. A transcriptomic profiling was performed on 11 samples throughout the fermentation. Through statistical analyses, 569 genes were highlighted as differentially expressed at one point during the time course of the experiment. These genes were classified into 9 clusters, according to their expression profiles. The combination of macroscopic and transcriptomic profiles highlighted 4 major steps in the culture: (i) a growth phase, (ii) a transition phase, (iii) an early lipid accumulation phase, characterized by an increase in nitrogen metabolism, together with strong repression of protein production and activity; (iv) a late lipid accumulation phase, characterized by the rerouting of carbon fluxes within cells. This study explores the potential of Y. lipolytica as an alternative oil producer, by identifying, at the transcriptomic level, the genes potentially involved in the metabolism of oleaginous species.
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Affiliation(s)
| | - Julien Cescut
- Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France
- INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, France
- CNRS, UMR5504, Toulouse, France
| | | | - Gaëlle Lelandais
- Dynamique des Structures et Interactions des Macromolécules Biologiques, UMR-S 665 - Université Paris 7, INTS, Paris, France
| | - Veronique Le Berre
- Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France
- INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, France
- CNRS, UMR5504, Toulouse, France
- Plateforme Biopuces de la Génopole de Toulouse Midi Pyrénées, INSA/DGBA 135, Toulouse, France
| | - Jean-Louis Uribelarrea
- Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France
- INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, France
- CNRS, UMR5504, Toulouse, France
| | - Carole Molina-Jouve
- Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France
- INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, France
- CNRS, UMR5504, Toulouse, France
| | - Jean-Marc Nicaud
- INRA, UMR1319 Micalis, Jouy-en-Josas, France
- CNRS, Micalis, Jouy-en-Josas, France
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18
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Wu X, Tu BP. Selective regulation of autophagy by the Iml1-Npr2-Npr3 complex in the absence of nitrogen starvation. Mol Biol Cell 2011; 22:4124-33. [PMID: 21900499 PMCID: PMC3204073 DOI: 10.1091/mbc.e11-06-0525] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Autophagy can be induced in response to more subtle changes in nutritional state, without severe nitrogen starvation. The Iml1p-Npr2p-Npr3p complex selectively regulates this form of autophagy. Autophagy is an evolutionarily conserved pathway for the degradation of intracellular contents. How autophagy is regulated, especially upon changes in metabolic and nutritional state, remains poorly understood. By using a prototrophic strain of Saccharomyces cerevisiae, we observed that, unexpectedly, autophagy is strongly induced simply upon switch from a rich medium to a minimal medium in the complete absence of nitrogen starvation. This novel form of autophagy was termed “non-nitrogen-starvation (NNS)–induced autophagy.” A visual screen uncovered three regulators of autophagy—Iml1p, Npr2p, and Npr3p—which function in the same complex and are selectively required for NNS-induced autophagy. During NNS-induced autophagy, Iml1p localized to either preautophagosomal structures (PAS) or non-PAS punctate structures. This localization suggests that Iml1p or the Iml1p-Npr2p-Npr3p complex might regulate autophagosome formation. Ultrastructural analysis confirmed that autophagosome formation was strongly impaired in Δiml1, Δnpr2, and Δnpr3 cells during NNS-induced autophagy. Moreover, Iml1p contains a conserved domain that is required for NNS-induced autophagy as well as complex formation. Collectively, our findings have revealed the existence of additional mechanisms that regulate autophagy under previously unrecognized conditions, in response to relatively more subtle changes in metabolic and nutritional state.
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Affiliation(s)
- Xi Wu
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390, USA
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19
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Omnus DJ, Pfirrmann T, Andréasson C, Ljungdahl PO. A phosphodegron controls nutrient-induced proteasomal activation of the signaling protease Ssy5. Mol Biol Cell 2011; 22:2754-65. [PMID: 21653827 PMCID: PMC3145550 DOI: 10.1091/mbc.e11-04-0282] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The Ssy1-Ptr3-Ssy5 (SPS) sensor of extracellular amino acids coordinates the sequential activity of general signaling factors and the 26S proteasome in a novel proteolytic activation cascade to activate the intracellular signaling protease Ssy5, which endoproteolytically activates two latent transcription factors. Regulated proteolysis serves as a mechanism to control cellular processes. The SPS (Ssy1-Ptr3-Ssy5) sensor in yeast responds to extracellular amino acids by endoproteolytically activating transcription factors Stp1 and Stp2 (Stp1/2). The processing endoprotease Ssy5 is regulated via proteasomal degradation of its noncovalently associated N-terminal prodomain. We find that degradation of the prodomain requires a conserved phosphodegron comprising phosphoacceptor sites and ubiquitin-accepting lysine residues. Upon amino acid induction, the phosphodegron is modified in a series of linked events by a set of general regulatory factors involved in diverse signaling pathways. First, an amino acid–induced conformational change triggers phosphodegron phosphorylation by the constitutively active plasma membrane–localized casein kinase I (Yck1/2). Next the prodomain becomes a substrate for polyubiquitylation by the Skp1/Cullin/Grr1 E3 ubiquitin ligase complex (SCFGrr1). Finally, the modified prodomain is concomitantly degraded by the 26S proteasome. These integrated events are requisite for unfettering the Ssy5 endoprotease, and thus Stp1/2 processing. The Ssy5 phosphoacceptor motif resembles the Yck1/2- and Grr1-dependent degrons of regulators in the Snf3/Rgt2 glucose-sensing pathway. Our work defines a novel proteolytic activation cascade that regulates an intracellular signaling protease and illustrates how general signaling components are recruited to distinct pathways that achieve conditional and specific signaling outputs.
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Affiliation(s)
- Deike J Omnus
- Wenner-Gren Institute, Stockholm University, S-106 91 Stockholm, Sweden
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20
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Dokudovskaya S, Waharte F, Schlessinger A, Pieper U, Devos DP, Cristea IM, Williams R, Salamero J, Chait BT, Sali A, Field MC, Rout MP, Dargemont C. A conserved coatomer-related complex containing Sec13 and Seh1 dynamically associates with the vacuole in Saccharomyces cerevisiae. Mol Cell Proteomics 2011; 10:M110.006478. [PMID: 21454883 DOI: 10.1074/mcp.m110.006478] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The presence of multiple membrane-bound intracellular compartments is a major feature of eukaryotic cells. Many of the proteins required for formation and maintenance of these compartments share an evolutionary history. Here, we identify the SEA (Seh1-associated) protein complex in yeast that contains the nucleoporin Seh1 and Sec13, the latter subunit of both the nuclear pore complex and the COPII coating complex. The SEA complex also contains Npr2 and Npr3 proteins (upstream regulators of TORC1 kinase) and four previously uncharacterized proteins (Sea1-Sea4). Combined computational and biochemical approaches indicate that the SEA complex proteins possess structural characteristics similar to the membrane coating complexes COPI, COPII, the nuclear pore complex, and, in particular, the related Vps class C vesicle tethering complexes HOPS and CORVET. The SEA complex dynamically associates with the vacuole in vivo. Genetic assays indicate a role for the SEA complex in intracellular trafficking, amino acid biogenesis, and response to nitrogen starvation. These data demonstrate that the SEA complex is an additional member of a family of membrane coating and vesicle tethering assemblies, extending the repertoire of protocoatomer-related complexes.
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21
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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