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O’Donnell MP, Chao PH, Kammenga JE, Sengupta P. Rictor/TORC2 mediates gut-to-brain signaling in the regulation of phenotypic plasticity in C. elegans. PLoS Genet 2018; 14:e1007213. [PMID: 29415022 PMCID: PMC5819832 DOI: 10.1371/journal.pgen.1007213] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 02/20/2018] [Accepted: 01/22/2018] [Indexed: 01/03/2023] Open
Abstract
Animals integrate external cues with information about internal conditions such as metabolic state to execute the appropriate behavioral and developmental decisions. Information about food quality and quantity is assessed by the intestine and transmitted to modulate neuronal functions via mechanisms that are not fully understood. The conserved Target of Rapamycin complex 2 (TORC2) controls multiple processes in response to cellular stressors and growth factors. Here we show that TORC2 coordinates larval development and adult behaviors in response to environmental cues and feeding state in the bacterivorous nematode C. elegans. During development, pheromone, bacterial food, and temperature regulate expression of the daf-7 TGF-β and daf-28 insulin-like peptide in sensory neurons to promote a binary decision between reproductive growth and entry into the alternate dauer larval stage. We find that TORC2 acts in the intestine to regulate neuronal expression of both daf-7 and daf-28, which together reflect bacterial-diet dependent feeding status, thus providing a mechanism for integration of food signals with external cues in the regulation of neuroendocrine gene expression. In the adult, TORC2 similarly acts in the intestine to modulate food-regulated foraging behaviors via a PDF-2/PDFR-1 neuropeptide signaling-dependent pathway. We also demonstrate that genetic variation affects food-dependent larval and adult phenotypes, and identify quantitative trait loci (QTL) associated with these traits. Together, these results suggest that TORC2 acts as a hub for communication of feeding state information from the gut to the brain, thereby contributing to modulation of neuronal function by internal state. Decision-making in all animals, including humans, involves weighing available information about the external environment as well as the animals’ internal conditions. Information about the environment is obtained via the sensory nervous system, whereas internal state can be assessed via cues such as levels of hormones or nutrients. How multiple external and internal inputs are processed in the nervous system to drive behavior or development is not fully understood. In this study, we examine how the nematode C. elegans integrates dietary information received by the gut with environmental signals to alter nervous system function. We have found that a signaling complex, called TORC2, acts in the gut to relay nutrition signals to alter hormonal signaling by the nervous system in C. elegans. Altered neuronal signaling in turn affects a food-dependent binary developmental decision in larvae, as well as food-dependent foraging behaviors in adults. Our results provide a mechanism by which animals prioritize specific signals such as feeding status to appropriately alter their development and/or behavior.
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Affiliation(s)
- Michael P. O’Donnell
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA, United States of America
- * E-mail: (MPO); (PS)
| | - Pin-Hao Chao
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA, United States of America
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University and Research, Wageningen, The Netherlands
| | - Piali Sengupta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA, United States of America
- * E-mail: (MPO); (PS)
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102
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Vadla R, Haldar D. Mammalian target of rapamycin complex 2 (mTORC2) controls glycolytic gene expression by regulating Histone H3 Lysine 56 acetylation. Cell Cycle 2018; 17:110-123. [PMID: 29143563 DOI: 10.1080/15384101.2017.1404207] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Metabolic reprogramming is a hallmark of cancer cells, but the mechanisms are not well understood. The mammalian target of rapamycin complex 2 (mTORC2) controls cell growth and proliferation and plays a critical role in metabolic reprogramming in glioma. mTORC2 regulates cellular processes such as cell survival, metabolism, and proliferation by phosphorylation of AGC kinases. Components of mTORC2 are shown to localize to the nucleus, but whether mTORC2 modulates epigenetic modifications to regulate gene expression is not known. Here, we identified histone H3 lysine 56 acetylation (H3K56Ac) is regulated by mTORC2 and show that global H3K56Ac levels were downregulated on mTORC2 knockdown but not on mTORC1 knockdown. mTORC2 promotes H3K56Ac in a tuberous sclerosis complex 1/2 (TSC1/2) mediated signaling pathway. We show that knockdown of sirtuin6 (SIRT6) prevented H3K56 deacetylation in mTORC2 depleted cells. Using glioma model consisting of U87EGFRvIII cells, we established that mTORC2 promotes H3K56Ac in glioma. Finally, we show that mTORC2 regulates the expression of glycolytic genes by regulating H3K56Ac levels at the promoters of these genes in glioma cells and depletion of mTOR leads to increased recruitment of SIRT6 to these promoters. Collectively, these results identify mTORC2 signaling pathway positively promotes H3K56Ac through which it may mediate metabolic reprogramming in glioma.
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Affiliation(s)
- Raghavendra Vadla
- a Centre for DNA Fingerprinting and Diagnostics , Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Hyderabad 500039 , Ranga Reddy District , India.,b Graduate Studies , Manipal University , Manipal , India
| | - Devyani Haldar
- a Centre for DNA Fingerprinting and Diagnostics , Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Hyderabad 500039 , Ranga Reddy District , India
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103
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Rad E, Murray JT, Tee AR. Oncogenic Signalling through Mechanistic Target of Rapamycin (mTOR): A Driver of Metabolic Transformation and Cancer Progression. Cancers (Basel) 2018; 10:cancers10010005. [PMID: 29301334 PMCID: PMC5789355 DOI: 10.3390/cancers10010005] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 12/27/2017] [Accepted: 12/28/2017] [Indexed: 12/29/2022] Open
Abstract
Throughout the years, research into signalling pathways involved in cancer progression has led to many discoveries of which mechanistic target of rapamycin (mTOR) is a key player. mTOR is a master regulator of cell growth control. mTOR is historically known to promote cell growth by enhancing the efficiency of protein translation. Research in the last decade has revealed that mTOR’s role in promoting cell growth is much more multifaceted. While mTOR is necessary for normal human physiology, cancer cells take advantage of mTOR signalling to drive their neoplastic growth and progression. Oncogenic signal transduction through mTOR is a common occurrence in cancer, leading to metabolic transformation, enhanced proliferative drive and increased metastatic potential through neovascularisation. This review focuses on the downstream mTOR-regulated processes that are implicated in the “hallmarks” of cancer with focus on mTOR’s involvement in proliferative signalling, metabolic reprogramming, angiogenesis and metastasis.
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Affiliation(s)
- Ellie Rad
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.
- School of Biochemistry & Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
| | - James T Murray
- School of Biochemistry & Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
| | - Andrew R Tee
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.
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104
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Jüppner J, Mubeen U, Leisse A, Caldana C, Wiszniewski A, Steinhauser D, Giavalisco P. The target of rapamycin kinase affects biomass accumulation and cell cycle progression by altering carbon/nitrogen balance in synchronized Chlamydomonas reinhardtii cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:355-376. [PMID: 29172247 DOI: 10.1111/tpj.13787] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 10/31/2017] [Accepted: 11/15/2017] [Indexed: 05/19/2023]
Abstract
Several metabolic processes tightly regulate growth and biomass accumulation. A highly conserved protein complex containing the target of rapamycin (TOR) kinase is known to integrate intra- and extracellular stimuli controlling nutrient allocation and hence cellular growth. Although several functions of TOR have been described in various heterotrophic eukaryotes, our understanding lags far behind in photosynthetic organisms. In the present investigation, we used the model alga Chlamydomonas reinhardtii to conduct a time-resolved analysis of molecular and physiological features throughout the diurnal cycle after TOR inhibition. Detailed examination of the cell cycle phases revealed that growth is not only repressed by 50%, but also that significant, non-linear delays in the progression can be observed. By using metabolomics analysis, we elucidated that the growth repression was mainly driven by differential carbon partitioning between anabolic and catabolic processes. Accordingly, the time-resolved analysis illustrated that metabolic processes including amino acid-, starch- and triacylglycerol synthesis, as well RNA degradation, were redirected within minutes of TOR inhibition. Here especially the high accumulation of nitrogen-containing compounds indicated that an active TOR kinase controls the carbon to nitrogen balance of the cell, which is responsible for biomass accumulation, growth and cell cycle progression.
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Affiliation(s)
- Jessica Jüppner
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Umarah Mubeen
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Andrea Leisse
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
- Brazilian Bioethanol Science and Technology Laboratory/CNPEM, Rua Giuseppe Máximo Scolfano 10000, 13083-970, Campinas, Brazil
| | - Andrew Wiszniewski
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Dirk Steinhauser
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Patrick Giavalisco
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
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105
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Abstract
It is now widely recognised that ageing and its associated functional decline are regulated by a wide range of molecules that fit into specific cellular pathways. Here, we describe several of the evolutionary conserved cellular signalling pathways that govern organismal ageing and discuss how their identification, and work on the individual molecules that contribute to them, has aided in the design of therapeutic strategies to alleviate the adverse effects of ageing and age-related disease.
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106
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Influence of the Novel ATP-Competitive Dual mTORC1/2 Inhibitor AZD2014 on Immune Cell Populations and Heart Allograft Rejection. Transplantation 2017; 101:2830-2840. [PMID: 28885497 DOI: 10.1097/tp.0000000000001933] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Little is known about how new-generation adenosine triphosphate-competitive mechanistic target of rapamycin (mTOR) kinase inhibitors affect immunity and allograft rejection. METHODS mTOR complex (C) 1 and 2 signaling in dendritic cells and T cells was analyzed by Western blotting, whereas immune cell populations in normal and heart allograft recipient mice were analyzed by flow cytometry. Alloreactive T cell proliferation was quantified in mixed leukocyte reaction; intracellular cytokine production and serum antidonor IgG levels were determined by flow analysis and immunofluorescence staining used to detect IgG in allografts. RESULTS The novel target of rapamycin kinase inhibitor AZD2014 impaired dendritic cell differentiation and T cell proliferation in vitro and depressed immune cells and allospecific T cell responses in vivo. A 9-day course of AZD2014 (10 mg/kg, intraperitoneally, twice daily) or rapamycin (RAPA) (1 mg/kg, intraperitoneally, daily) prolonged median heart allograft survival time significantly (25 days for AZD2014, 100 days for RAPA, 9.5 days for control). Like RAPA, AZD2014 suppressed graft mononuclear cell infiltration, increased regulatory T cell to effector memory T cell ratios and reduced T follicular helper and B cells 7 days posttransplant. By 21 days (10 days after drug withdrawal), however, T follicular helper and B cells and donor-specific IgG1 and IgG2c antibody titers were significantly lower in RAPA-treated compared with AZD2014-treated mice. Elevated regulatory T cell to effector memory T cell ratios were maintained after RAPA, but not AZD2014 withdrawal. CONCLUSIONS Immunomodulatory effects of AZD2014, unlike those of RAPA, were not sustained after drug withdrawal, possibly reflecting distinct pharmacokinetics or/and inhibitory effects of AZD2014 on mTORC2.
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107
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Karuppasamy M, Kusmider B, Oliveira TM, Gaubitz C, Prouteau M, Loewith R, Schaffitzel C. Cryo-EM structure of Saccharomyces cerevisiae target of rapamycin complex 2. Nat Commun 2017; 8:1729. [PMID: 29170376 PMCID: PMC5700991 DOI: 10.1038/s41467-017-01862-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 10/18/2017] [Indexed: 12/11/2022] Open
Abstract
The target of rapamycin (TOR) kinase assembles into two distinct multiprotein complexes, conserved across eukaryote evolution. In contrast to TOR complex 1 (TORC1), TORC2 kinase activity is not inhibited by the macrolide rapamycin. Here, we present the structure of Saccharomyces cerevisiae TORC2 determined by electron cryo-microscopy. TORC2 contains six subunits assembling into a 1.4 MDa rhombohedron. Tor2 and Lst8 form the common core of both TOR complexes. Avo3/Rictor is unique to TORC2, but interacts with the same HEAT repeats of Tor2 that are engaged by Kog1/Raptor in mammalian TORC1, explaining the mutual exclusivity of these two proteins. Density, which we conclude is Avo3, occludes the FKBP12-rapamycin-binding site of Tor2’s FRB domain rendering TORC2 rapamycin insensitive and recessing the kinase active site. Although mobile, Avo1/hSin1 further restricts access to the active site as its conserved-region-in-the-middle (CRIM) domain is positioned along an edge of the TORC2 active-site-cleft, consistent with a role for CRIM in substrate recruitment. Target of rapamycin (TOR) kinase operates within two distinct multiprotein complexes named TORC1 and TORC2. Here the authors report a cryo-EM structure of TORC2, establish its subunit organization, providing a rationale for TORC2’s rapamycin insensitivity and the mutually exclusive inclusion of Avo3/Rictor or Raptor within their respective TOR complex.
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Affiliation(s)
- Manikandan Karuppasamy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Beata Kusmider
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Taiana M Oliveira
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Christl Gaubitz
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Manoel Prouteau
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Robbie Loewith
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland. .,Swiss National Centre for Competence in Research (NCCR) in Chemical Biology, University of Geneva, 30 Quai Ernest-Ansermet, Bristol, CH1211 Geneva, Switzerland.
| | - Christiane Schaffitzel
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France. .,School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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108
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Evolutionary Conservation of the Components in the TOR Signaling Pathways. Biomolecules 2017; 7:biom7040077. [PMID: 29104218 PMCID: PMC5745459 DOI: 10.3390/biom7040077] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/26/2017] [Accepted: 10/27/2017] [Indexed: 01/08/2023] Open
Abstract
Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that controls multiple cellular processes upon various intracellular and extracellular stimuli. Since its first discovery, extensive studies have been conducted both in yeast and animal species including humans. Those studies have revealed that TOR forms two structurally and physiologically distinct protein complexes; TOR complex 1 (TORC1) is ubiquitous among eukaryotes including animals, yeast, protozoa, and plants, while TOR complex 2 (TORC2) is conserved in diverse eukaryotic species other than plants. The studies have also identified two crucial regulators of mammalian TORC1 (mTORC1), Ras homolog enriched in brain (RHEB) and RAG GTPases. Of these, RAG regulates TORC1 in yeast as well and is conserved among eukaryotes with the green algae and land plants as apparent exceptions. RHEB is present in various eukaryotes but sporadically missing in multiple taxa. RHEB, in the budding yeast Saccharomyces cerevisiae, appears to be extremely divergent with concomitant loss of its function as a TORC1 regulator. In this review, we summarize the evolutionarily conserved functions of the key regulatory subunits of TORC1 and TORC2, namely RAPTOR, RICTOR, and SIN1. We also delve into the evolutionary conservation of RHEB and RAG and discuss the conserved roles of these GTPases in regulating TORC1.
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109
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Evolving Significance and Future Relevance of Anti-Angiogenic Activity of mTOR Inhibitors in Cancer Therapy. Cancers (Basel) 2017; 9:cancers9110152. [PMID: 29104248 PMCID: PMC5704170 DOI: 10.3390/cancers9110152] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 10/23/2017] [Accepted: 10/27/2017] [Indexed: 12/12/2022] Open
Abstract
mTOR inhibitors have demonstrated remarkable anti-tumor activity in experimental models, mainly by reducing cancer cell growth and tumor angiogenesis. Their use in cancer patients as monotherapy has, however, generated only limited benefits, increasing median overall survival by only a few months. Likewise, in other targeted therapies, cancer cells develop resistance mechanisms to overcome mTOR inhibition. Hence, novel therapeutic strategies have to be designed to increase the efficacy of mTOR inhibitors in cancer. In this review, we discuss the present and future relevance of mTOR inhibitors in cancer therapy by focusing on their effects on tumor angiogenesis.
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110
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Abstract
In this issue of Molecular Cell, Moloughney et al. (2016) find that mTORC2 responds to falling levels of glucose and glutamine catabolites, promoting glutaminolysis and preserving the TCA cycle and hexosamine biosynthesis.
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Affiliation(s)
- Sebastian I Arriola Apelo
- Department of Medicine, University of Wisconsin-Madison and William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Dudley W Lamming
- Department of Medicine, University of Wisconsin-Madison and William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA.
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111
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Cameron AJ, Veeriah S, Marshall JJ, Murray ER, Larijani B, Parker PJ. Uncoupling TORC2 from AGC kinases inhibits tumour growth. Oncotarget 2017; 8:84685-84696. [PMID: 29156676 PMCID: PMC5689566 DOI: 10.18632/oncotarget.20086] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 06/26/2017] [Indexed: 12/28/2022] Open
Abstract
Mammalian target of rapamycin (mTOR) is a central regulator of growth and metabolism. mTOR resides in two distinct multi-protein complexes - mTORC1 and mTORC2 - with distinct upstream regulators and downstream targets. While it is possible to specifically inhibit mTORC1 with rapamycin, or inhibit both mTOR complexes together with ATP pocket directed mTOR kinase inhibitors, it is not possible to assess the specific roles for mTORC2 pharmacologically. To overcome this, we have developed a novel, inducible, dominant negative system for disrupting substrate recruitment to mTORC2. Previously we identified the mTORC2 specific subunit Sin1 as a direct binding partner for AGC kinases Akt and PKC. Sin1 mutants, which retain the ability to bind Rictor and mTOR, but fail to recruit their AGC client kinases, inhibit AKT and PKC priming and block cell growth. In this study, we demonstrate that uncoupling mTORC2 from AGC kinases in DLD1 colon cancer cells inhibits Akt activation and blocks tumour growth in vivo. Further we demonstrate, using time resolved two-site amplified FRET (A-FRET) analysis of xenograft tumours, that inhibition of tumour growth correlates with the degree of mTORC2 uncoupling from its downstream targets, as demonstrated for Akt. These data add weight to the body of evidence that mTORC2 represents a pharmacological target in cancer independently of mTORC1.
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Affiliation(s)
- Angus J.M. Cameron
- Kinase Biology Laboratory, Barts Cancer Institute, Queen Mary University of London, John Vane Science Centre, Charterhouse Square, London, UK
| | - Selvaraju Veeriah
- Translational Cancer Therapeutics Laboratory, Paul O’Gorman Building, University College London Cancer Institute, London, United Kingdom
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
| | | | - Elizabeth R. Murray
- Kinase Biology Laboratory, Barts Cancer Institute, Queen Mary University of London, John Vane Science Centre, Charterhouse Square, London, UK
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) & Biofísika Instituto (UPV/EHU, CSIC), University of the Basque Country, Areatza Hiribidea, Plentzia, Spain
| | - Peter J. Parker
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
- Division of Cancer Studies, King’s College London, New Hunts House, Guy’s Campus, London, UK
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112
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Deregulated c-Myc requires a functional HSF1 for experimental and human hepatocarcinogenesis. Oncotarget 2017; 8:90638-90650. [PMID: 29207593 PMCID: PMC5710874 DOI: 10.18632/oncotarget.21469] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 09/21/2017] [Indexed: 12/16/2022] Open
Abstract
Deregulated activity of the c-Myc protooncogene is a frequent molecular event underlying mouse and human hepatocarcinogenesis. Nonetheless, the mechanisms sustaining c-Myc oncogenic activity in liver cancer remain scarcely delineated. Recently, we showed that the mammalian target of rapamycin complex 1 (mTORC1) cascade is induced and necessary for c-Myc dependent liver tumor development and progression. Since the heat shock factor 1 (HSF1) transcription factor is a major positive regulator of mTORC1 in the cell, we investigated the functional interaction between HSF1 and c-Myc using in vitro and in vivo approaches. We found that ablation of HSF1 restrains the growth of c-Myc-derived mouse hepatocellular carcinoma (HCC) cell lines, where it induces downregulation of c-Myc levels. Conversely, silencing of c-Myc gene in human and mouse HCC cells led to downregulation of HSF1 expression. Most importantly, overexpression of a dominant negative form of HSF1 (HSF1dn) in the mouse liver via hydrodynamic gene delivery resulted in the complete inhibition of mouse hepatocarcinogenesis driven by overexpression of c-Myc. Altogether, the present results indicate that a functional HSF1 is necessary for c-Myc-driven hepatocarcinogenesis. Consequently, targeting HSF1 might represent a novel and effective therapeutic strategy for the treatment of HCC subsets with activated c-Myc signaling.
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113
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Nguyen TP, Frank AR, Jewell JL. Amino acid and small GTPase regulation of mTORC1. CELLULAR LOGISTICS 2017; 7:e1378794. [PMID: 29296509 PMCID: PMC5739091 DOI: 10.1080/21592799.2017.1378794] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/06/2017] [Accepted: 09/08/2017] [Indexed: 11/03/2022]
Abstract
The mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that belongs to the phosphatidylinositol 3-kinase-related kinase (PIKK) family. mTOR is the catalytic subunit of mTOR complex 1 (mTORC1), which integrates multiple environmental signals to control cell growth and metabolism. Nutrients, specifically amino acids, are the most potent stimuli for mTORC1 activation. Multiple studies have focused on how leucine and arginine activate mTORC1 through the Rag GTPases, with mechanistic details slowly emerging. Recently, a Rag GTPase-independent glutamine signaling pathway to mTORC1 has been identified, suggesting that mTORC1 is differentially regulated through distinct pathways by specific amino acids. In this review, we summarize our current understanding of how amino acids modulate mTORC1, and the role of other small GTPases in the regulation of mTORC1 activity.
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Affiliation(s)
- Thu P Nguyen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX USA.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Anderson R Frank
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX USA.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Jenna L Jewell
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX USA.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX USA
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114
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The TORC2-Dependent Signaling Network in the Yeast Saccharomyces cerevisiae. Biomolecules 2017; 7:biom7030066. [PMID: 28872598 PMCID: PMC5618247 DOI: 10.3390/biom7030066] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 12/21/2022] Open
Abstract
To grow, eukaryotic cells must expand by inserting glycerolipids, sphingolipids, sterols, and proteins into their plasma membrane, and maintain the proper levels and bilayer distribution. A fungal cell must coordinate growth with enlargement of its cell wall. In Saccharomyces cerevisiae, a plasma membrane-localized protein kinase complex, Target of Rapamicin (TOR) complex-2 (TORC2) (mammalian ortholog is mTORC2), serves as a sensor and master regulator of these plasma membrane- and cell wall-associated events by directly phosphorylating and thereby stimulating the activity of two types of effector protein kinases: Ypk1 (mammalian ortholog is SGK1), along with a paralog (Ypk2); and, Pkc1 (mammalian ortholog is PKN2/PRK2). Ypk1 is a central regulator of pathways and processes required for plasma membrane lipid and protein homeostasis, and requires phosphorylation on its T-loop by eisosome-associated protein kinase Pkh1 (mammalian ortholog is PDK1) and a paralog (Pkh2). For cell survival under various stresses, Ypk1 function requires TORC2-mediated phosphorylation at multiple sites near its C terminus. Pkc1 controls diverse processes, especially cell wall synthesis and integrity. Pkc1 is also regulated by Pkh1- and TORC2-dependent phosphorylation, but, in addition, by interaction with Rho1-GTP and lipids phosphatidylserine (PtdSer) and diacylglycerol (DAG). We also describe here what is currently known about the downstream substrates modulated by Ypk1-mediated and Pkc1-mediated phosphorylation.
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115
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Dual abrogation of MNK and mTOR: a novel therapeutic approach for the treatment of aggressive cancers. Future Med Chem 2017; 9:1539-1555. [PMID: 28841037 DOI: 10.4155/fmc-2017-0062] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Targeting the translational machinery has emerged as a promising therapeutic option for cancer treatment. Cancer cells require elevated protein synthesis and exhibit augmented activity to meet the increased metabolic demand. Eukaryotic translation initiation factor 4E is necessary for mRNA translation, its availability and phosphorylation are regulated by the PI3K/AKT/mTOR and MNK1/2 pathways. The phosphorylated form of eIF4E drives the expression of oncogenic proteins including those involved in metastasis. In this article, we will review the role of eIF4E in cancer, its regulation and discuss the benefit of dual inhibition of upstream pathways. The discernible interplay between the MNK and mTOR signaling pathways provides a novel therapeutic opportunity to target aggressive migratory cancers through the development of hybrid molecules.
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Bootman MD, Chehab T, Bultynck G, Parys JB, Rietdorf K. The regulation of autophagy by calcium signals: Do we have a consensus? Cell Calcium 2017; 70:32-46. [PMID: 28847414 DOI: 10.1016/j.ceca.2017.08.005] [Citation(s) in RCA: 172] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 12/12/2022]
Abstract
Macroautophagy (hereafter called 'autophagy') is a cellular process for degrading and recycling cellular constituents, and for maintenance of cell function. Autophagy initiates via vesicular engulfment of cellular materials and culminates in their degradation via lysosomal hydrolases, with the whole process often being termed 'autophagic flux'. Autophagy is a multi-step pathway requiring the interplay of numerous scaffolding and signalling molecules. In particular, orthologs of the family of ∼30 autophagy-regulating (Atg) proteins that were first characterised in yeast play essential roles in the initiation and processing of autophagic vesicles in mammalian cells. The serine/threonine kinase mTOR (mechanistic target of rapamycin) is a master regulator of the canonical autophagic response of cells to nutrient starvation. In addition, AMP-activated protein kinase (AMPK), which is a key sensor of cellular energy status, can trigger autophagy by inhibiting mTOR, or by phosphorylating other downstream targets. Calcium (Ca2+) has been implicated in autophagic signalling pathways encompassing both mTOR and AMPK, as well as in autophagy seemingly not involving these kinases. Numerous studies have shown that cytosolic Ca2+ signals can trigger autophagy. Moreover, introduction of an exogenous chelator to prevent cytosolic Ca2+ signals inhibits autophagy in response to many different stimuli, with suggestions that buffering Ca2+ affects not only the triggering of autophagy, but also proximal and distal steps during autophagic flux. Observations such as these indicate that Ca2+ plays an essential role as a pro-autophagic signal. However, cellular Ca2+ signals can exert anti-autophagic actions too. For example, Ca2+ channel blockers induce autophagy due to the loss of autophagy-suppressing Ca2+ signals. In addition, the sequestration of Ca2+ by mitochondria during physiological signalling appears necessary to maintain cellular bio-energetics, thereby suppressing AMPK-dependent autophagy. This article attempts to provide an integrated overview of the evidence for the proposed roles of various Ca2+ signals, Ca2+ channels and Ca2+ sources in controlling autophagic flux.
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Affiliation(s)
- Martin D Bootman
- School of Life, Health and Chemical Sciences, The Open University, MK7 6AA, UK.
| | - Tala Chehab
- School of Life, Health and Chemical Sciences, The Open University, MK7 6AA, UK
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), B-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), B-3000 Leuven, Belgium
| | - Katja Rietdorf
- School of Life, Health and Chemical Sciences, The Open University, MK7 6AA, UK
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Nomura W, Maeta K, Inoue Y. Phosphatidylinositol 3,5-bisphosphate is involved in methylglyoxal-induced activation of the Mpk1 mitogen-activated protein kinase cascade in Saccharomyces cerevisiae. J Biol Chem 2017; 292:15039-15048. [PMID: 28743744 DOI: 10.1074/jbc.m117.791590] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 07/21/2017] [Indexed: 11/06/2022] Open
Abstract
Methylglyoxal (MG) is a natural metabolite derived from glycolysis, and this 2-oxoaldehyde has been implicated in some diseases including diabetes. However, the physiological significance of MG for cellular functions is yet to be fully elucidated. We previously reported that MG activates the Mpk1 (MAPK) cascade in the yeast Saccharomyces cerevisiae To gain further insights into the cellular functions and responses to MG, we herein screened yeast-deletion mutant collections for susceptibility to MG. We found that mutants defective in the synthesis of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) are more susceptible to MG. PtdIns(3,5)P2 levels increased following MG treatment, and vacuolar morphology concomitantly changed to a single swollen shape. MG activated the Pkc1-Mpk1 MAPK cascade in which a small GTPase Rho1 plays a crucial role, and the MG-induced phosphorylation of Mpk1 was impaired in mutants defective in the PtdIns(3,5)P2 biosynthetic pathway. Of note, heat shock-induced stress also provoked Mpk1 phosphorylation in a Rho1-dependent manner; however, PtdIns(3,5)P2 was dispensable for the heat shock-stimulated activation of this signaling pathway. Our results suggest that PtdIns(3,5)P2 is specifically involved in the MG-induced activation of the Mpk1 MAPK cascade and in the cellular adaptation to MG-induced stress.
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Affiliation(s)
- Wataru Nomura
- From the Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kazuhiro Maeta
- From the Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yoshiharu Inoue
- From the Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
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The Stress-Sensing TORC2 Complex Activates Yeast AGC-Family Protein Kinase Ypk1 at Multiple Novel Sites. Genetics 2017; 207:179-195. [PMID: 28739659 PMCID: PMC5586371 DOI: 10.1534/genetics.117.1124] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 07/16/2017] [Indexed: 01/18/2023] Open
Abstract
Yeast (Saccharomyces cerevisiae) target of rapamycin (TOR) complex 2 (TORC2) is a multi-subunit plasma membrane-associated protein kinase and vital growth regulator. Its essential functions are exerted via phosphorylation and stimulation of downstream protein kinase Ypk1 (and its paralog Ypk2). Ypk1 phosphorylates multiple substrates to regulate plasma membrane lipid and protein composition. Ypk1 function requires phosphorylation of Thr504 in its activation loop by eisosome-associated Pkh1 (and its paralog Pkh2). For cell survival under certain stresses, however, Ypk1 activity requires further stimulation by TORC2-mediated phosphorylation at C-terminal sites, dubbed the “turn” (Ser644) and “hydrophobic” (Thr662) motifs. Here we show that four additional C-terminal sites are phosphorylated in a TORC2-dependent manner, collectively defining a minimal consensus. We found that the newly identified sites are as important for Ypk1 activity, stability, and biological function as Ser644 and Thr662. Ala substitutions at the four new sites abrogated the ability of Ypk1 to rescue the phenotypes of Ypk1 deficiency, whereas Glu substitutions had no ill effect. Combining the Ala substitutions with an N-terminal mutation (D242A), which has been demonstrated to bypass the need for TORC2-mediated phosphorylation, restored the ability to complement a Ypk1-deficient cell. These findings provide new insights about the molecular basis for TORC2-dependent activation of Ypk1.
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Tumor suppressor Pdcd4 attenuates Sin1 translation to inhibit invasion in colon carcinoma. Oncogene 2017; 36:6225-6234. [PMID: 28692058 PMCID: PMC5680133 DOI: 10.1038/onc.2017.228] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/22/2017] [Accepted: 06/01/2017] [Indexed: 12/16/2022]
Abstract
Programmed cell death 4 (Pdcd4), a tumor invasion suppressor, is frequently down-regulated in colorectal cancer and other cancers. In this study, we find that loss of Pdcd4 increases the activity of mammalian target of rapamycin complex 2 (mTORC2) and thereby upregulates Snail expression. Examining the components of mTORC2 showed that Pdcd4 knockdown increased the protein but not mRNA level of stress-activated-protein kinase interacting protein 1 (Sin1), which resulted from enhanced Sin1 translation. To understand how Pdcd4 regulates Sin1 translation, the SIN1 5’ untranslated region (5’UTR) was fused with luciferase reporter and named as 5’Sin1-Luc. Pdcd4 knockdown/knockout significantly increased the translation of 5’Sin1-Luc but not the control luciferase without the SIN1 5’UTR, suggesting that Sin1 5’UTR is necessary for Pdcd4 to inhibit Sin1 translation. Ectopic expression of wild type Pdcd4 and Pdcd4(157–469), a deletion mutant that binds to translation initiation factor 4A (eIF4A), sufficiently inhibited Sin1 translation, and thus suppressed mTORC2 kinase activity and invasion in colon tumor cells. By contrast, Pdcd4(157–469)(D253A,D418A), a mutant that does not bind to eIF4A, failed to inhibit Sin1 translation, and consequently failed to repress mTORC2 activity and invasion. In addition, directly inhibiting eIF4A with silvestrol significantly suppressed Sin1 translation and attenuated invasion. These results indicate that Pdcd4-inhibited Sin1 translation is through suppressing eIF4A, and functionally important for suppression of mTORC2 activity and invasion. Moreover, in colorectal cancer tissues, the Sin1 protein but not mRNA was significantly up-regulated while Pdcd4 protein was down-regulated, suggesting that loss of Pdcd4 might correlate with Sin1 protein level but not mRNA level in colorectal cancer patients. Taken together, our work reveals a novel mechanism by which Pdcd4 inhibits Sin1 translation to attenuatemTORC2 activity and thereby suppresses invasion.
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Inflammation dependent mTORC1 signaling interferes with the switch from keratinocyte proliferation to differentiation. PLoS One 2017; 12:e0180853. [PMID: 28700632 PMCID: PMC5507280 DOI: 10.1371/journal.pone.0180853] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 06/06/2017] [Indexed: 12/13/2022] Open
Abstract
Psoriasis is a frequent and often severe inflammatory skin disease, characterized by altered epidermal homeostasis. Since we found previously that Akt/mTOR signaling is hyperactivated in psoriatic skin, we aimed at elucidating the role of aberrant mTORC1 signaling in this disease. We found that under healthy conditions mTOR signaling was shut off when keratinocytes switch from proliferation to terminal differentiation. Inflammatory cytokines (IL-1β, IL-17A, TNF-α) induced aberrant mTOR activity which led to enhanced proliferation and reduced expression of differentiation markers. Conversely, regular differentiation could be restored if mTORC1 signaling was blocked. In mice, activation of mTOR through the agonist MHY1485 also led to aberrant epidermal organization and involucrin distribution. In summary, these results not only identify mTORC1 as an important signal integrator pivotal for the cells fate to either proliferate or differentiate, but emphasize the role of inflammation-dependent mTOR activation as a psoriatic pathomechanism.
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Liu P, Ge M, Hu J, Li X, Che L, Sun K, Cheng L, Huang Y, Pilo MG, Cigliano A, Pes GM, Pascale RM, Brozzetti S, Vidili G, Porcu A, Cossu A, Palmieri G, Sini MC, Ribback S, Dombrowski F, Tao J, Calvisi DF, Chen L, Chen X. A functional mammalian target of rapamycin complex 1 signaling is indispensable for c-Myc-driven hepatocarcinogenesis. Hepatology 2017; 66:167-181. [PMID: 28370287 PMCID: PMC5481473 DOI: 10.1002/hep.29183] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 02/11/2017] [Accepted: 03/17/2017] [Indexed: 02/05/2023]
Abstract
UNLABELLED Amplification and/or activation of the c-Myc proto-oncogene is one of the leading genetic events along hepatocarcinogenesis. The oncogenic potential of c-Myc has been proven experimentally by the finding that its overexpression in the mouse liver triggers tumor formation. However, the molecular mechanism whereby c-Myc exerts its oncogenic activity in the liver remains poorly understood. Here, we demonstrate that the mammalian target of rapamycin complex 1 (mTORC1) cascade is activated and necessary for c-Myc-dependent hepatocarcinogenesis. Specifically, we found that ablation of Raptor, the unique member of mTORC1, strongly inhibits c-Myc liver tumor formation. Also, the p70 ribosomal S6 kinase/ribosomal protein S6 and eukaryotic translation initiation factor 4E-binding protein 1/eukaryotic translation initiation factor 4E signaling cascades downstream of mTORC1 are required for c-Myc-driven tumorigenesis. Intriguingly, microarray expression analysis revealed up-regulation of multiple amino acid transporters, including solute carrier family 1 member A5 (SLC1A5) and SLC7A6, leading to robust uptake of amino acids, including glutamine, into c-Myc tumor cells. Subsequent functional studies showed that amino acids are critical for activation of mTORC1 as their inhibition suppressed mTORC1 in c-Myc tumor cells. In human hepatocellular carcinoma specimens, levels of c-Myc directly correlate with those of mTORC1 activation as well as of SLC1A5 and SLC7A6. CONCLUSION Our current study indicates that an intact mTORC1 axis is required for c-Myc-driven hepatocarcinogenesis; thus, targeting the mTOR pathway or amino acid transporters may be an effective and novel therapeutic option for the treatment of hepatocellular carcinoma with activated c-Myc signaling. (Hepatology 2017;66:167-181).
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Affiliation(s)
- Pin Liu
- Department of Pediatrics, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
| | - Mengmeng Ge
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Junjie Hu
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
- School of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, China
| | - Xiaolei Li
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
- Department of Thyroid and Breast Surgery, Jinan Military General Hospital of PLA, Jinan, Shandong, China
| | - Li Che
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
| | - Kun Sun
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Lili Cheng
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Yuedong Huang
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Maria G. Pilo
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Antonio Cigliano
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Giovanni M. Pes
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Rosa M. Pascale
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Stefania Brozzetti
- Pietro Valdoni Surgery Department, University of Rome La Sapienza, Rome, Italy
| | - Gianpaolo Vidili
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Alberto Porcu
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Antonio Cossu
- Unit of Pathology, Azienda Ospedaliero Universitaria Sassari, Sassari, Italy
| | - Giuseppe Palmieri
- Institute of Biomolecular Chemistry, National Research Council, Sassari, Italy
| | - Maria C. Sini
- Institute of Biomolecular Chemistry, National Research Council, Sassari, Italy
| | - Silvia Ribback
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Frank Dombrowski
- Institute of Pathology, University of Greifswald, Greifswald, Germany
| | - Junyan Tao
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
| | - Diego F. Calvisi
- Institute of Pathology, University of Greifswald, Greifswald, Germany
- Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Ligong Chen
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Xin Chen
- Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA. U.S.A
- School of Pharmacy, Hubei University of Chinese Medicine, Wuhan, Hubei, China
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122
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The Architecture of the Rag GTPase Signaling Network. Biomolecules 2017; 7:biom7030048. [PMID: 28788436 PMCID: PMC5618229 DOI: 10.3390/biom7030048] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 06/22/2017] [Accepted: 06/27/2017] [Indexed: 12/11/2022] Open
Abstract
The evolutionarily conserved target of rapamycin complex 1 (TORC1) couples an array of intra- and extracellular stimuli to cell growth, proliferation and metabolism, and its deregulation is associated with various human pathologies such as immunodeficiency, epilepsy, and cancer. Among the diverse stimuli impinging on TORC1, amino acids represent essential input signals, but how they control TORC1 has long remained a mystery. The recent discovery of the Rag GTPases, which assemble as heterodimeric complexes on vacuolar/lysosomal membranes, as central elements of an amino acid signaling network upstream of TORC1 in yeast, flies, and mammalian cells represented a breakthrough in this field. Here, we review the architecture of the Rag GTPase signaling network with a special focus on structural aspects of the Rag GTPases and their regulators in yeast and highlight both the evolutionary conservation and divergence of the mechanisms that control Rag GTPases.
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123
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Tsapras P, Nezis IP. Caspase involvement in autophagy. Cell Death Differ 2017; 24:1369-1379. [PMID: 28574508 DOI: 10.1038/cdd.2017.43] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 02/24/2017] [Accepted: 02/28/2017] [Indexed: 12/26/2022] Open
Abstract
Caspases are a family of cysteine proteases widely known as the principal mediators of the apoptotic cell death response, but considerably less so as the contributors to the regulation of pathways outside cellular demise. In regards to autophagy, the modulatory roles of caspases have only recently begun to be adequately described. In contrast to apoptosis, autophagy promotes cell survival by providing energy and nutrients through the lysosomal degradation of cytoplasmic constituents. Under basal conditions autophagy and apoptosis cross-regulate each other through an elaborate network of interconnections which also includes the interplay between autophagy-related proteins (ATGs) and caspases. In this review we focus on the effects of this crosstalk at the cellular level, as we aim to concentrate the main observations from research conducted so far on the fine-tuning of autophagy by caspases. Several members of this protease-family have been found to directly interact with key ATGs involved in different tiers across the autophagic cascade. Therefore, we firstly outline the core mechanism of macroautophagy in brief. In an effort to emphasize the importance of the intricate cross-regulation of ATGs and caspases, we also present examples of autophagy's contribution to apoptotic cell death during development.
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Affiliation(s)
| | - Ioannis P Nezis
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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124
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Tiedemann K, Le Nihouannen D, Fong JE, Hussein O, Barralet JE, Komarova SV. Regulation of Osteoclast Growth and Fusion by mTOR/raptor and mTOR/rictor/Akt. Front Cell Dev Biol 2017; 5:54. [PMID: 28573133 PMCID: PMC5435769 DOI: 10.3389/fcell.2017.00054] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 05/02/2017] [Indexed: 12/31/2022] Open
Abstract
Osteoclasts are giant bone cells formed by fusion from monocytes and uniquely capable of a complete destruction of mineralized tissues. Previously, we have demonstrated that in energy-rich environment not only osteoclast fusion index (the number of nuclei each osteoclast contains), but also cytoplasm volume per single nucleus was increased. The goal of this study was to investigate the regulation of metabolic sensor mTOR during osteoclast differentiation in energy-rich environment simulated by addition of pyruvate. We have found that in the presence of pyruvate, the proportion of mTOR associated with raptor increased, while mTOR-rictor-mediated Akt phosphorylation decreased. Inhibition of mTOR with rapamycin (10 nM) significantly interfered with all aspects of osteoclastogenesis. However, rapamycin at 1 nM, which preferentially targets mTOR-raptor complex, was only effective in control cultures, while in the presence of pyruvate osteoclast fusion index was successfully increased. Inhibition of Akt drastically reduced osteoclast fusion, however in energy-rich environment, osteoclasts of comparable size were formed through increased cytoplasm growth. These data suggest that mTOR-rictor mediated Akt signaling regulates osteoclast fusion, while mTOR-raptor regulation of protein translation contributes to fusion-independent cytoplasm growth. We demonstrate that depending on the bioenergetics microenvironment osteoclastogenesis can adjust to occur through preferential multinucleation or through cell growth, implying that attaining large cell size is part of the osteoclast differentiation program.
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Affiliation(s)
- Kerstin Tiedemann
- Faculty of Dentistry, McGill UniversityMontreal, QC, Canada.,Shriners Hospital for Children-CanadaMontreal, QC, Canada
| | | | - Jenna E Fong
- Faculty of Dentistry, McGill UniversityMontreal, QC, Canada
| | - Osama Hussein
- Faculty of Dentistry, McGill UniversityMontreal, QC, Canada
| | - Jake E Barralet
- Faculty of Dentistry, McGill UniversityMontreal, QC, Canada.,Department of Surgery, Faculty of Medicine, McGill UniversityMontreal, QC, Canada
| | - Svetlana V Komarova
- Faculty of Dentistry, McGill UniversityMontreal, QC, Canada.,Shriners Hospital for Children-CanadaMontreal, QC, Canada
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125
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Lee PL, Jung SM, Guertin DA. The Complex Roles of Mechanistic Target of Rapamycin in Adipocytes and Beyond. Trends Endocrinol Metab 2017; 28:319-339. [PMID: 28237819 PMCID: PMC5682923 DOI: 10.1016/j.tem.2017.01.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/20/2017] [Accepted: 01/23/2017] [Indexed: 01/01/2023]
Abstract
Having healthy adipose tissue is essential for metabolic fitness. This is clear from the obesity epidemic, which is unveiling a myriad of comorbidities associated with excess adipose tissue including type 2 diabetes, cardiovascular disease, and cancer. Lipodystrophy also causes insulin resistance, emphasizing the importance of having a balanced amount of fat. In cells, the mechanistic target of rapamycin (mTOR) complexes 1 and 2 (mTORC1 and mTORC2, respectively) link nutrient and hormonal signaling with metabolism, and recent studies are shedding new light on their in vivo roles in adipocytes. In this review, we discuss how recent advances in adipose tissue and mTOR biology are converging to reveal new mechanisms that maintain healthy adipose tissue, and discuss ongoing mysteries of mTOR signaling, particularly for the less understood complex mTORC2.
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Affiliation(s)
- Peter L Lee
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Su Myung Jung
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - David A Guertin
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA.
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Benavides-Serrato A, Lee J, Holmes B, Landon KA, Bashir T, Jung ME, Lichtenstein A, Gera J. Specific blockade of Rictor-mTOR association inhibits mTORC2 activity and is cytotoxic in glioblastoma. PLoS One 2017; 12:e0176599. [PMID: 28453552 PMCID: PMC5409528 DOI: 10.1371/journal.pone.0176599] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/13/2017] [Indexed: 12/19/2022] Open
Abstract
A small molecule which specifically blocks the interaction of Rictor and mTOR was identified utilizing a high-throughput yeast two-hybrid screen and evaluated as a potential inhibitor of mTORC2 activity in glioblastoma multiforme (GBM). In vitro, CID613034 inhibited mTORC2 kinase activity at submicromolar concentrations and in cellular assays specifically inhibited phosphorylation of mTORC2 substrates, including AKT (Ser-473), NDRG1 (Thr-346) and PKCα (Ser-657), while having no appreciable effects on the phosphorylation status of the mTORC1 substrate S6K (Thr-389) or mTORC1-dependent negative feedback loops. CID613034 demonstrated significant inhibitory effects on cell growth, motility and invasiveness in GBM cell lines and sensitivity correlated with relative Rictor or SIN1 expression. Structure-activity relationship analyses afforded an inhibitor, JR-AB2-011, with improved anti-GBM properties and blocked mTORC2 signaling and Rictor association with mTOR at lower effective concentrations. In GBM xenograft studies, JR-AB2-011 demonstrated significant anti-tumor properties. These data support mTORC2 as a viable therapeutic target in GBM and suggest that targeting protein-protein interactions critical for mTORC2 function is an effective strategy to achieve therapeutic responses.
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Affiliation(s)
- Angelica Benavides-Serrato
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California, United States of America
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
| | - Jihye Lee
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, United States of America
| | - Brent Holmes
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California, United States of America
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
| | - Kenna A. Landon
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
| | - Tariq Bashir
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
| | - Michael E. Jung
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, United States of America
- Jonnson Comprehensive Cancer Center, University of California-Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California-Los Angeles, Los Angeles, California, United States of America
| | - Alan Lichtenstein
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California, United States of America
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
- Jonnson Comprehensive Cancer Center, University of California-Los Angeles, Los Angeles, California, United States of America
| | - Joseph Gera
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California, United States of America
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California, United States of America
- Jonnson Comprehensive Cancer Center, University of California-Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California-Los Angeles, Los Angeles, California, United States of America
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127
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Abstract
INTRODUCTION Dishevelled, Egl-10 and Pleckstrin (DEP) domain-containing protein 5 (DEPDC5) is a protein subunit of the GTPase-activating proteins towards Rags 1 (GATOR1) complex. GATOR1 is a recently identified modulator of mechanistic target of rapamycin (mTOR) activity. mTOR is a key regulator of cell proliferation and metabolism; disruption of the mTOR pathway is implicated in focal epilepsy, both acquired and genetic. Tuberous sclerosis is the prototypic mTOR genetic syndrome with epilepsy, however GATOR1 gene mutations have recently been shown to cause lesional and non-lesional focal epilepsy. Areas covered: This review summarizes the mTOR pathway, including regulators and downstream effectors, emphasizing recent developments in the understanding of the complex role of the GATOR1 complex. We review the epilepsy types associated with mTOR overactivity, including tuberous sclerosis, polyhydramnios megalencephaly symptomatic epilepsy, cortical dysplasia, non-lesional focal epilepsy and post-traumatic epilepsy. Currently available mTOR inhibitors are discussed, primarily rapamycin analogs and ATP competitive mTOR inhibitors. Expert opinion: DEPDC5 is an attractive therapeutic target in focal epilepsy, as effects of DEPDC5 agonists would likely be anti-epileptogenic and more selective than currently available mTOR inhibitors. Therapeutic effects might be synergistic with certain existing dietary therapies, including the ketogenic diet.
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Affiliation(s)
- Kenneth A Myers
- a Epilepsy Research Centre, Department of Medicine , The University of Melbourne, Austin Health , Heidelberg , Victoria , Australia.,b Department of Paediatrics , Royal Children's Hospital, The University of Melbourne , Flemington , Victoria , Australia
| | - Ingrid E Scheffer
- a Epilepsy Research Centre, Department of Medicine , The University of Melbourne, Austin Health , Heidelberg , Victoria , Australia.,b Department of Paediatrics , Royal Children's Hospital, The University of Melbourne , Flemington , Victoria , Australia.,c The Florey Institute of Neuroscience and Mental Health , Heidelberg , Victoria , Australia
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Merhi A, Delrée P, Marini AM. The metabolic waste ammonium regulates mTORC2 and mTORC1 signaling. Sci Rep 2017; 7:44602. [PMID: 28303961 PMCID: PMC5355986 DOI: 10.1038/srep44602] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/09/2017] [Indexed: 12/21/2022] Open
Abstract
Two structurally and functionally distinct mammalian TOR complexes control cell growth and metabolism in physiological and pathological contexts including cancer. Upregulated glutaminolysis is part of the metabolic reprogramming occurring in cancer, providing fuels for growth but also liberating ammonium, a potent neurotoxic waste product. Here, we identify ammonium as a novel dose-dependent signal mediating rapid mTORC2 activation and further regulating mTORC1. We show that ammonium induces rapid RICTOR-dependent phosphorylation of AKT-S473, a process requiring the PI3K pathway and further involving the Src-family kinase YES1, the FAK kinase and the ITGβ1 integrin. Release of calcium from the endoplasmic reticulum store triggers rapid mTORC2 activation, similar to ammonium-induced activation, the latter being conversely prevented by calcium chelation.Moreover, in analogy to growth factors, ammonium triggers the AKT-dependent phosphoinhibition of the TSC complex and of PRAS40, two negative regulators of mTORC1. Consistent with mTORC1 stimulation, ammonium induces the inhibitory phosphorylation of 4EBP1, a negative regulator of protein biogenesis. Ammonium however dually impacts on the phosphorylation of p70S6K1 triggering a transient AKT-independent decrease in the phosphorylation of this second mTORC1 readout. Finally, we reveal ammonium as a dose-dependent stimulator of proliferation. This study underscores an mTORC2 and mTORC1 response to the so-called ammonium waste.
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Affiliation(s)
- Ahmad Merhi
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium.,Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium.,Tumour Bank, Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium
| | - Paul Delrée
- Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium.,Tumour Bank, Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium
| | - Anna Maria Marini
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium
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Yang W, Yang LF, Song ZQ, Shah SZA, Cui YY, Li CS, Zhao HF, Gao HL, Zhou XM, Zhao DM. PRAS40 alleviates neurotoxic prion peptide-induced apoptosis via mTOR-AKT signaling. CNS Neurosci Ther 2017; 23:416-427. [PMID: 28294542 DOI: 10.1111/cns.12685] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 02/06/2017] [Accepted: 02/07/2017] [Indexed: 01/04/2023] Open
Abstract
AIMS The proline-rich Akt substrate of 40-kDa (PRAS40) protein is a direct inhibitor of mTORC1 and an interactive linker between the Akt and mTOR pathways. The mammalian target of rapamycin (mTOR) is considered to be a central regulator of cell growth and metabolism. Several investigations have demonstrated that abnormal mTOR activity may contribute to the pathogenesis of several neurodegenerative disorders and lead to cognitive deficits. METHODS Here, we used the PrP peptide 106-126 (PrP106-126 ) in a cell model of prion diseases (also known as transmissible spongiform encephalopathies, TSEs) to investigate the mechanisms of mTOR-mediated cell death in prion diseases. RESULTS We have shown that, upon stress caused by PrP106-126 , the mTOR pathway activates and contributes to cellular apoptosis. Moreover, we demonstrated that PRAS40 down-regulates mTOR hyperactivity under stress conditions and alleviates neurotoxic prion peptide-induced apoptosis. The effect of PRAS40 on apoptosis is likely due to an mTOR/Akt signaling. CONCLUSION PRAS40 inhibits mTORC1 hyperactivation and plays a key role in protecting cells against neurotoxic prion peptide-induced apoptosis. Thus, PRAS40 is a potential therapeutic target for prion disease.
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Affiliation(s)
- Wei Yang
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China.,Hebei Institute of Animal Science and Veterinary Medicine, Baoding, China
| | - Li-Feng Yang
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Zhi-Qi Song
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Syed Zahid Ali Shah
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Yong-Yong Cui
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Chao-Si Li
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Hua-Fen Zhao
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Hong-Li Gao
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - Xiang-Mei Zhou
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
| | - De-Ming Zhao
- National Animal Transmissible Spongiform Encephalopathy Laboratory and Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China
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130
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Thobe K, Sers C, Siebert H. Unraveling the regulation of mTORC2 using logical modeling. Cell Commun Signal 2017; 15:6. [PMID: 28103956 PMCID: PMC5244562 DOI: 10.1186/s12964-016-0159-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 12/20/2016] [Indexed: 11/10/2022] Open
Abstract
Background The mammalian target of rapamycin (mTOR) is a regulator of cell proliferation, cell growth and apoptosis working through two distinct complexes: mTORC1 and mTORC2. Although much is known about the activation and inactivation of mTORC1, the processes controlling mTORC2 remain poorly characterized. Experimental and modeling studies have attempted to explain the regulation of mTORC2 but have yielded several conflicting hypotheses. More specifically, the Phosphoinositide 3-kinase (PI3K) pathway was shown to be involved in this process, but the identity of the kinase interacting with and regulating mTORC2 remains to be determined (Cybulski and Hall, Trends Biochem Sci 34:620-7, 2009). Method We performed a literature search and identified 5 published hypotheses describing mTORC2 regulation. Based on these hypotheses, we built logical models, not only for each single hypothesis but also for all combinations and possible mechanisms among them. Based on data provided by the original studies, a systematic analysis of all models was performed. Results We were able to find models that account for experimental observations from every original study, but do not require all 5 hypotheses to be implemented. Surprisingly, all hypotheses were in agreement with all tested data gathered from the different studies and PI3K was identified as an essential regulator of mTORC2. Conclusion The results and additional data suggest that more than one regulator is necessary to explain the behavior of mTORC2. Finally, this study proposes a new experiment to validate mTORC1 as second essential regulator.
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Affiliation(s)
- Kirsten Thobe
- Group for Discrete Biomathematics, Department for Mathematics and Computer Science, Freie Universitaet Berlin, Arnimallee 7, Berlin, 14195, Germany. .,International Research School for Scientific Computing and Computational Biology, Max-Plank Institute for Molecular Genetics, Berlin, Germany.
| | - Christine Sers
- Laboratory of Molecular Tumor Pathology, Institute of Pathology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Heike Siebert
- Group for Discrete Biomathematics, Department for Mathematics and Computer Science, Freie Universitaet Berlin, Arnimallee 7, Berlin, 14195, Germany.,International Research School for Scientific Computing and Computational Biology, Max-Plank Institute for Molecular Genetics, Berlin, Germany
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131
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Faus-Garriga J, Novoa I, Ozaita A. mTOR signaling in proteostasis and its relevance to autism spectrum disorders. AIMS BIOPHYSICS 2017. [DOI: 10.3934/biophy.2017.1.63] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Miyata S, Kurachi M, Sakurai N, Yanagawa Y, Ishizaki Y, Mikuni M, Fukuda M. Gene expression alterations in the medial prefrontal cortex and blood cells in a mouse model of depression during menopause. Heliyon 2016; 2:e00219. [PMID: 28054037 PMCID: PMC5198744 DOI: 10.1016/j.heliyon.2016.e00222] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 11/30/2016] [Accepted: 12/19/2016] [Indexed: 01/09/2023] Open
Abstract
Aims The prevalence of major depressive disorder (MDD) is higher in women than in men, and this may be due to the decline in estrogen levels that occurs during the menopausal transition. We studied the biological alterations in the medial prefrontal cortex (mPFC), which is a region that is highly implicated in the neurobiology of MDD, and the blood cells (BCs) of ovariectomized (OVX) mice subjected to chronic mild stress (CMS), which represents a mouse model of depression during menopause. Main methods The mPFC and the BCs were obtained from the same individuals. Gene expression levels were analyzed by microarray. The data were used for the Ingenuity Pathway Analysis and the Gene Ontology analysis. Key findings The gene expression alterations (GEAs) induced by OVX were mainly associated with ribosomal and mitochondrial functions in both the mPFC and the BCs. Rapamycin-insensitive companion of mTOR (RICTOR) was identified as a possible upstream regulator of the OVX-induced GEAs in both tissues. The CMS-induced GEAs were associated with retinoic acid receptor signaling, inflammatory cytokines and post-synaptic density in the mPFC, but not in the BCs. Significance OVX and CMS independently affect biological pathways in the mPFC, which is involved in the development of the depression-like phenotype. Because a subset of the OVX-induced GEAs in the mPFC also occurred in the BCs, the GEAs in the BCs might be a useful probe to predict biological pathways in the corresponding brain tissue under specific conditions such as OVX in females.
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Affiliation(s)
- Shigeo Miyata
- Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masashi Kurachi
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Noriko Sakurai
- Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yasuki Ishizaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masahiko Mikuni
- Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masato Fukuda
- Department of Psychiatry and Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
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Lana D, Di Russo J, Mello T, Wenk GL, Giovannini MG. Rapamycin inhibits mTOR/p70S6K activation in CA3 region of the hippocampus of the rat and impairs long term memory. Neurobiol Learn Mem 2016; 137:15-26. [PMID: 27838442 DOI: 10.1016/j.nlm.2016.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 10/06/2016] [Accepted: 11/08/2016] [Indexed: 01/09/2023]
Abstract
The present study was aimed at establishing whether the mTOR pathway and its downstream effector p70S6K in CA3 pyramidal neurons are under the modulation of the cholinergic input to trigger the formation of long term memories, similar to what we demonstrated in CA1 hippocampus. We performed in vivo behavioral experiments using the step down inhibitory avoidance test in adult Wistar rats to evaluate memory formation under different conditions. We examined the effects of rapamycin, an inhibitor of mTORC1 formation, scopolamine, a muscarinic receptor antagonist or mecamylamine, a nicotinic receptor antagonist, on short and long term memory formation and on the functionality of the mTOR pathway. Acquisition was conducted 30min after i.c.v. injection of rapamycin. Recall testing was performed 1h, 4h or 24h after acquisition. We found that (1) mTOR and p70S6K activation in CA3 pyramidal neurons were involved in long term memory formation; (2) rapamycin significantly inhibited mTOR and of p70S6K activation at 4h, and long term memory impairment 24h after acquisition; (3) scopolamine impaired short but not long term memory, with an early increase of mTOR/p70S6K activation at 1h followed by stabilization at longer times; (4) mecamylamine and scopolamine co-administration impaired short term memory at 1h and 4h and reduced the scopolamine-induced increase of mTOR/p70S6K activation at 1h and 4h; (5) mecamylamine and scopolamine treatment did not impair long term memory formation; (6) unexpectedly, rapamycin increased mTORC2 activation in microglial cells. Our results demonstrate that in CA3 pyramidal neurons the mTOR/p70S6K pathway is under the modulation of the cholinergic system and is involved in long-term memory encoding, and are consistent with the hypothesis that the CA3 region of the hippocampus is involved in memory mechanisms based on rapid, one-trial object-place learning and recall. Furthermore, our results are in accordance with previous reports that selective molecular mechanisms underlie either short term memory, long term memory, or both. Furthermore, our discovery that administration of rapamycin increased the activation of mTORC2 in microglial cells supports a reappraisal of the beneficial/adverse effects of rapamycin administration.
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Affiliation(s)
- D Lana
- Department of Health Sciences, Section of Pharmacology and Clinical Oncology, University of Florence, Florence, Italy
| | - J Di Russo
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence, University of Muenster, Muenster, Germany
| | - T Mello
- Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence, Italy
| | - G L Wenk
- Department of Psychology, The Ohio State University, OH, USA
| | - M G Giovannini
- Department of Health Sciences, Section of Pharmacology and Clinical Oncology, University of Florence, Florence, Italy.
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134
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Roohi A, Hojjat-Farsangi M. Recent advances in targeting mTOR signaling pathway using small molecule inhibitors. J Drug Target 2016; 25:189-201. [PMID: 27632356 DOI: 10.1080/1061186x.2016.1236112] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Targeted-based cancer therapy (TBCT) or personalized medicine is one of the main treatment modalities for cancer that has been developed to decrease the undesirable effects of chemotherapy. Targeted therapy inhibits the growth of tumor cells by interrupting with particular molecules required for tumorigenesis and proliferation of tumor cells rather than interfering with dividing normal cells. Therefore, targeted therapies are anticipated to be more efficient than former tumor treatment agents with minimal side effects on non-tumor cells. Small molecule inhibitors (SMIs) are currently one of the most investigated anti-tumor agents of TBCT. These small organic agents target several vital molecules involved in cell biological processes and induce target cells apoptosis and necrosis. Mechanistic (mammalian) target of rapamycin (mTOR) complexes (mTORC1/2) control different intracellular processes, including growth, proliferation, angiogenesis and metabolism. Signaling pathways, in which mTOR complexes are involved in are usually dysregulated in various tumors and have been shown to be ideal targets for SMIs. Currently, different mTOR-SMIs are in the clinic for the treatment of cancer patients, and several others are in preclinical or clinical settings. In this review, we summarize recent advances in developing different mTOR inhibitors, which are currently in preclinical and clinical investigations or have been approved for cancer treatment.
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Affiliation(s)
- Azam Roohi
- a Department of Immunology, School of Public Health , Tehran University of Medical Sciences , Tehran , Iran
| | - Mohammad Hojjat-Farsangi
- b Department of Oncology-Pathology, Immune and Gene therapy Lab , Cancer Center Karolinska (CCK), Karolinska University Hospital Solna and Karolinska Institute , Stockholm , Sweden.,c Department of Immunology, School of Medicine , Bushehr University of Medical Sciences , Bushehr , Iran
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In B cells, phosphatidylinositol 5-phosphate 4-kinase-α synthesizes PI(4,5)P2 to impact mTORC2 and Akt signaling. Proc Natl Acad Sci U S A 2016; 113:10571-6. [PMID: 27601656 DOI: 10.1073/pnas.1522478113] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks) are enigmatic lipid kinases with physiological functions that are incompletely understood, not the least because genetic deletion and cell transfection have led to contradictory data. Here, we used the genetic tractability of DT40 cells to create cell lines in which endogenous PI5P4Kα was removed, either stably by genetic deletion or transiently (within 1 h) by tagging the endogenous protein genomically with the auxin degron. In both cases, removal impacted Akt phosphorylation, and by leaving one PI5P4Kα allele present but mutating it to be kinase-dead or have PI4P 5-kinase activity, we show that all of the effects on Akt phosphorylation were dependent on the ability of PI5P4Kα to synthesize phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] rather than to remove PI5P. Although stable removal of PI5P4Kα resulted in a pronounced decrease in Akt phosphorylation at Thr308 and Ser473, in part because of reduced plasma membrane PIP3, its acute removal led to an increase in Akt phosphorylation only at Ser473. This process invokes activation primarily of mammalian target of rapamycin complex 2 (mTORC2), which was confirmed by increased phosphorylation of other mTORC2 substrates. These findings establish PI5P4Kα as a kinase that synthesizes a physiologically relevant pool of PI(4,5)P2 and as a regulator of mTORC2, and show a phenomenon similar to the "butterfly effect" described for phosphatidylinositol 3-kinase Iα [Hart JR, et al. (2015) Proc Natl Acad Sci USA 112(4):1131-1136], whereby through apparently the same underlying mechanism, the removal of a protein's activity from a cell can have widely divergent effects depending on the time course of that removal.
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mTORC2 Responds to Glutamine Catabolite Levels to Modulate the Hexosamine Biosynthesis Enzyme GFAT1. Mol Cell 2016; 63:811-26. [PMID: 27570073 DOI: 10.1016/j.molcel.2016.07.015] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 06/24/2016] [Accepted: 07/19/2016] [Indexed: 12/28/2022]
Abstract
Highly proliferating cells are particularly dependent on glucose and glutamine for bioenergetics and macromolecule biosynthesis. The signals that respond to nutrient fluctuations to maintain metabolic homeostasis remain poorly understood. Here, we found that mTORC2 is activated by nutrient deprivation due to decreasing glutamine catabolites. We elucidate how mTORC2 modulates a glutamine-requiring biosynthetic pathway, the hexosamine biosynthesis pathway (HBP) via regulation of expression of glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), the rate-limiting enzyme of the HBP. GFAT1 expression is dependent on sufficient amounts of glutaminolysis catabolites particularly α-ketoglutarate, which are generated in an mTORC2-dependent manner. Additionally, mTORC2 is essential for proper expression and nuclear accumulation of the GFAT1 transcriptional regulator, Xbp1s. Thus, while mTORC1 senses amino acid abundance to promote anabolism, mTORC2 responds to declining glutamine catabolites in order to restore metabolic homeostasis. Our findings uncover the role of mTORC2 in metabolic reprogramming and have implications for understanding insulin resistance and tumorigenesis.
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137
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Abstract
The mammalian target of rapamycin, mTOR, plays key roles in cell growth and proliferation, acting at the catalytic subunit of two protein kinase complexes: mTOR complexes 1 and 2 (mTORC1/2). mTORC1 signaling is switched on by several oncogenic signaling pathways and is accordingly hyperactive in the majority of cancers. Inhibiting mTORC1 signaling has therefore attracted great attention as an anti-cancer therapy. However, progress in using inhibitors of mTOR signaling as therapeutic agents in oncology has been limited by a number of factors, including the fact that the classic mTOR inhibitor, rapamycin, inhibits only some of the effects of mTOR; the existence of several feedback loops; and the crucial importance of mTOR in normal physiology.
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Affiliation(s)
- Jianling Xie
- Nutrition and Metabolism, South Australian Health and Medical research Institute, Adelaide, SA, Australia
| | - Xuemin Wang
- Nutrition and Metabolism, South Australian Health and Medical research Institute, Adelaide, SA, Australia; School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Christopher G Proud
- Nutrition and Metabolism, South Australian Health and Medical research Institute, Adelaide, SA, Australia; School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
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