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Fernandes SA, Angelidaki DD, Nüchel J, Pan J, Gollwitzer P, Elkis Y, Artoni F, Wilhelm S, Kovacevic-Sarmiento M, Demetriades C. Spatial and functional separation of mTORC1 signalling in response to different amino acid sources. Nat Cell Biol 2024:10.1038/s41556-024-01523-7. [PMID: 39385049 DOI: 10.1038/s41556-024-01523-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 09/09/2024] [Indexed: 10/11/2024]
Abstract
Amino acid (AA) availability is a robust determinant of cell growth through controlling mechanistic/mammalian target of rapamycin complex 1 (mTORC1) activity. According to the predominant model in the field, AA sufficiency drives the recruitment and activation of mTORC1 on the lysosomal surface by the heterodimeric Rag GTPases, from where it coordinates the majority of cellular processes. Importantly, however, the teleonomy of the proposed lysosomal regulation of mTORC1 and where mTORC1 acts on its effector proteins remain enigmatic. Here, by using multiple pharmacological and genetic means to perturb the lysosomal AA-sensing and protein recycling machineries, we describe the spatial separation of mTORC1 regulation and downstream functions in mammalian cells, with lysosomal and non-lysosomal mTORC1 phosphorylating distinct substrates in response to different AA sources. Moreover, we reveal that a fraction of mTOR localizes at lysosomes owing to basal lysosomal proteolysis that locally supplies new AAs, even in cells grown in the presence of extracellular nutrients, whereas cytoplasmic mTORC1 is regulated by exogenous AAs. Overall, our study substantially expands our knowledge about the topology of mTORC1 regulation by AAs and hints at the existence of distinct, Rag- and lysosome-independent mechanisms that control its activity at other subcellular locations. Given the importance of mTORC1 signalling and AA sensing for human ageing and disease, our findings will probably pave the way towards the identification of function-specific mTORC1 regulators and thus highlight more effective targets for drug discovery against conditions with dysregulated mTORC1 activity in the future.
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Affiliation(s)
- Stephanie A Fernandes
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Cologne Graduate School of Ageing Research, Cologne, Germany
| | | | - Julian Nüchel
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Jiyoung Pan
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Cologne Graduate School of Ageing Research, Cologne, Germany
| | | | - Yoav Elkis
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Filippo Artoni
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Cologne Graduate School of Ageing Research, Cologne, Germany
| | - Sabine Wilhelm
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | | | - Constantinos Demetriades
- Max Planck Institute for Biology of Ageing, Cologne, Germany.
- Cologne Graduate School of Ageing Research, Cologne, Germany.
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany.
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2
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Ndunguru SF, Reda GK, Csernus B, Knop R, Lugata JK, Szabó C, Lendvai ÁZ, Czeglédi L. Embryonic Leucine Promotes Early Postnatal Growth via mTOR Signalling in Japanese Quails. Animals (Basel) 2024; 14:2596. [PMID: 39272381 PMCID: PMC11394045 DOI: 10.3390/ani14172596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Revised: 08/26/2024] [Accepted: 09/04/2024] [Indexed: 09/15/2024] Open
Abstract
Nutritional cues during embryonic development can alter developmental trajectories and affect postnatal growth. However, the specific mechanisms by which nutrients influence avian growth remain largely unknown. Amino acids can directly interact with the nutrient-sensing pathways, such as the insulin-like growth factor 1 (IGF-1)/mechanistic target of rapamycin (mTOR) pathways, which are known to regulate growth. We examined the effects of embryonic leucine on gene expression and phenotypic growth in Japanese quails by injecting 2.5 mg leucine or saline (control) into Japanese quail eggs on the tenth day of incubation and incubating them under standard conditions. The treatment groups had similar hatching success and size at hatching. However, between 3 and 7 days post-hatching, quails treated with embryonic leucine showed increased growth in body mass and wing, tarsus, head, and intestinal lengths, lasting up to 21 days. The hepatic expression of IGF1, IGF1R, mTOR, and RPS6K1 was upregulated in leucine-treated quails, while the expression of FOXO1 remained unaffected. In conclusion, a subtle increase in embryonic leucine may induce developmental programming effects in Japanese quail by interacting with the IGF-1/mTOR nutrient-sensing pathway to promote growth. This study highlights the role of embryonic amino acids as crucial nutrients for enhancing growth. It provides valuable insight into nutrient intervention strategies during embryonic development to potentially improve poultry growth performance.
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Affiliation(s)
- Sawadi F Ndunguru
- Department of Animal Science, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
- Doctoral School of Animal Science, University of Debrecen, 4032 Debrecen, Hungary
- Department of Evolutionary Zoology and Human Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Gebrehaweria K Reda
- Department of Animal Science, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
- Doctoral School of Animal Science, University of Debrecen, 4032 Debrecen, Hungary
- Department of Evolutionary Zoology and Human Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Brigitta Csernus
- Department of Evolutionary Zoology and Human Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Renáta Knop
- Department of Animal Science, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
| | - James K Lugata
- Doctoral School of Animal Science, University of Debrecen, 4032 Debrecen, Hungary
- Department of Animal Nutrition and Physiology, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agriculture and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
| | - Csaba Szabó
- Department of Animal Nutrition and Physiology, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agriculture and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
| | - Ádám Z Lendvai
- Department of Evolutionary Zoology and Human Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Levente Czeglédi
- Department of Animal Science, Institute of Animal Science, Biotechnology and Nature Conservation, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, 4032 Debrecen, Hungary
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3
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Tripathi R, Aggarwal T, Lindberg FA, Klemm AH, Fredriksson R. SLC38A10 Regulate Glutamate Homeostasis and Modulate the AKT/TSC2/mTOR Pathway in Mouse Primary Cortex Cells. Front Cell Dev Biol 2022; 10:854397. [PMID: 35450293 PMCID: PMC9017388 DOI: 10.3389/fcell.2022.854397] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 03/15/2022] [Indexed: 12/13/2022] Open
Abstract
Glutamate acts as a critical regulator of neurotransmitter balance, recycling, synaptic function and homeostasis in the brain and glutamate transporters control glutamate levels in the brain. SLC38A10 is a member of the SLC38 family and regulates protein synthesis and cellular stress responses. Here, we uncover the role of SLC38A10 as a transceptor involved in glutamate-sensing signaling pathways that control both the glutamate homeostasis and mTOR-signaling. The culture of primary cortex cells from SLC38A10 knockout mice had increased intracellular glutamate. In addition, under nutrient starvation, KO cells had an impaired response in amino acid-dependent mTORC1 signaling. Combined studies from transcriptomics, protein arrays and metabolomics established that SLC38A10 is involved in mTOR signaling and that SLC38A10 deficient primary cortex cells have increased protein synthesis. Metabolomic data showed decreased cholesterol levels, changed fatty acid synthesis, and altered levels of fumaric acid, citrate, 2-oxoglutarate and succinate in the TCA cycle. These data suggests that SLC38A10 may act as a modulator of glutamate homeostasis, and mTOR-sensing and loss of this transceptor result in lower cholesterol, which could have implications in neurodegenerative diseases.
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Affiliation(s)
- Rekha Tripathi
- Department of Pharmaceutical Bioscience, Unit of Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
- *Correspondence: Rekha Tripathi,
| | - Tanya Aggarwal
- Department of Pharmaceutical Bioscience, Unit of Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Frida A. Lindberg
- Department of Pharmaceutical Bioscience, Unit of Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Anna H. Klemm
- BioImage Informatics Facility, SciLifeLab, Division of Visual Information and Interaction, Department of Information Technology, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Pharmaceutical Bioscience, Unit of Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
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4
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Zhang S, Lin X, Hou Q, Hu Z, Wang Y, Wang Z. Regulation of mTORC1 by amino acids in mammalian cells: A general picture of recent advances. ACTA ACUST UNITED AC 2021; 7:1009-1023. [PMID: 34738031 PMCID: PMC8536509 DOI: 10.1016/j.aninu.2021.05.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 05/13/2021] [Accepted: 05/18/2021] [Indexed: 12/11/2022]
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) integrates various types of signal inputs, such as energy, growth factors, and amino acids to regulate cell growth and proliferation mainly through the 2 direct downstream targets, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1) and ribosomal protein S6 kinase 1 (S6K1). Most of the signal arms upstream of mTORC1 including energy status, stress signals, and growth factors converge on the tuberous sclerosis complex (TSC) - Ras homologue enriched in brain (Rheb) axis. Amino acids, however, are distinct from other signals and modulate mTORC1 using a unique pathway. In recent years, the transmission mechanism of amino acid signals upstream of mTORC1 has been gradually elucidated, and some sensors or signal transmission pathways for individual amino acids have also been discovered. With the help of these findings, we propose a general picture of recent advances, which demonstrates that various amino acids from lysosomes, cytoplasm, and Golgi are sensed by their respective sensors. These signals converge on mTORC1 and form a huge and complicated signal network with multiple synergies, antagonisms, and feedback mechanisms.
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Affiliation(s)
- Shizhe Zhang
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
| | - Xueyan Lin
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
| | - Qiuling Hou
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
| | - Zhiyong Hu
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
| | - Yun Wang
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
| | - Zhonghua Wang
- Key Laboratory of Ruminant Nutrition and Physiology, College of Animal Science and Technology, Shandong Agricultural University, No. 61, Daizong Street, Tai'an, Shandong, China
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5
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Lakatos Z, Benkő P, Juhász G, Lőrincz P. Drosophila Rab39 Attenuates Lysosomal Degradation. Int J Mol Sci 2021; 22:ijms221910635. [PMID: 34638976 PMCID: PMC8508792 DOI: 10.3390/ijms221910635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/27/2021] [Accepted: 09/28/2021] [Indexed: 11/16/2022] Open
Abstract
Lysosomal degradation, the common destination of autophagy and endocytosis, is one of the most important elements of eukaryotic metabolism. The small GTPases Rab39A and B are potential new effectors of this pathway, as their malfunction is implicated in severe human diseases like cancer and neurodegeneration. In this study, the lysosomal regulatory role of the single Drosophila Rab39 ortholog was characterized, providing valuable insight into the potential cell biological mechanisms mediated by these proteins. Using a de novo CRISPR-generated rab39 mutant, we found no failure in the early steps of endocytosis and autophagy. On the contrary, we found that Rab39 mutant nephrocytes internalize and degrade endocytic cargo at a higher rate compared to control cells. In addition, Rab39 mutant fat body cells contain small yet functional autolysosomes without lysosomal fusion defect. Our data identify Drosophila Rab39 as a negative regulator of lysosomal clearance during both endocytosis and autophagy.
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Affiliation(s)
- Zsolt Lakatos
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, H-1117 Budapest, Hungary; (Z.L.); (P.B.)
| | - Péter Benkő
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, H-1117 Budapest, Hungary; (Z.L.); (P.B.)
- Department of Physiology, Semmelweis University, H-1094 Budapest, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, H-1117 Budapest, Hungary; (Z.L.); (P.B.)
- Biological Research Centre, Institute of Genetics, Hungarian Academy of Sciences, H-6726 Szeged, Hungary
- Correspondence: (G.J.); (P.L.)
| | - Péter Lőrincz
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, H-1117 Budapest, Hungary; (Z.L.); (P.B.)
- Premium Postdoctoral Research Program, Hungarian Academy of Sciences, H-1052 Budapest, Hungary
- Correspondence: (G.J.); (P.L.)
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6
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Melnik BC. Lifetime Impact of Cow's Milk on Overactivation of mTORC1: From Fetal to Childhood Overgrowth, Acne, Diabetes, Cancers, and Neurodegeneration. Biomolecules 2021; 11:404. [PMID: 33803410 PMCID: PMC8000710 DOI: 10.3390/biom11030404] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/04/2021] [Accepted: 03/04/2021] [Indexed: 02/07/2023] Open
Abstract
The consumption of cow's milk is a part of the basic nutritional habits of Western industrialized countries. Recent epidemiological studies associate the intake of cow's milk with an increased risk of diseases, which are associated with overactivated mechanistic target of rapamycin complex 1 (mTORC1) signaling. This review presents current epidemiological and translational evidence linking milk consumption to the regulation of mTORC1, the master-switch for eukaryotic cell growth. Epidemiological studies confirm a correlation between cow's milk consumption and birthweight, body mass index, onset of menarche, linear growth during childhood, acne vulgaris, type 2 diabetes mellitus, prostate cancer, breast cancer, hepatocellular carcinoma, diffuse large B-cell lymphoma, neurodegenerative diseases, and all-cause mortality. Thus, long-term persistent consumption of cow's milk increases the risk of mTORC1-driven diseases of civilization. Milk is a highly conserved, lactation genome-controlled signaling system that functions as a maternal-neonatal relay for optimized species-specific activation of mTORC1, the nexus for regulation of eukaryotic cell growth, and control of autophagy. A deeper understanding of milk´s impact on mTORC1 signaling is of critical importance for the prevention of common diseases of civilization.
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Affiliation(s)
- Bodo C Melnik
- Department of Dermatology, Environmental Medicine and Health Theory, University of Osnabrück, Am Finkenhügel 7a, D-49076 Osnabrück, Germany
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7
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Morozumi Y, Shiozaki K. Conserved and Divergent Mechanisms That Control TORC1 in Yeasts and Mammals. Genes (Basel) 2021; 12:genes12010088. [PMID: 33445779 PMCID: PMC7828246 DOI: 10.3390/genes12010088] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 12/23/2022] Open
Abstract
Target of rapamycin complex 1 (TORC1), a serine/threonine-protein kinase complex highly conserved among eukaryotes, coordinates cellular growth and metabolism with environmental cues, including nutrients and growth factors. Aberrant TORC1 signaling is associated with cancers and various human diseases, and TORC1 also plays a key role in ageing and lifespan, urging current active research on the mechanisms of TORC1 regulation in a variety of model organisms. Identification and characterization of the RAG small GTPases as well as their regulators, many of which are highly conserved from yeast to humans, led to a series of breakthroughs in understanding the molecular bases of TORC1 regulation. Recruitment of mammalian TORC1 (mTORC1) by RAGs to lysosomal membranes is a key step for mTORC1 activation. Interestingly, the RAG GTPases in fission yeast are primarily responsible for attenuation of TORC1 activity on vacuoles, the yeast equivalent of lysosomes. In this review, we summarize our current knowledge about the functions of TORC1 regulators on yeast vacuoles, and illustrate the conserved and divergent mechanisms of TORC1 regulation between yeasts and mammals.
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Affiliation(s)
- Yuichi Morozumi
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan;
- Correspondence: ; Tel.: +81-743-72-5543
| | - Kazuhiro Shiozaki
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan;
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA
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8
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Bass JJ, Nakhuda A, Deane CS, Brook MS, Wilkinson DJ, Phillips BE, Philp A, Tarum J, Kadi F, Andersen D, Garcia AM, Smith K, Gallagher IJ, Szewczyk NJ, Cleasby ME, Atherton PJ. Overexpression of the vitamin D receptor (VDR) induces skeletal muscle hypertrophy. Mol Metab 2020; 42:101059. [PMID: 32771696 PMCID: PMC7475200 DOI: 10.1016/j.molmet.2020.101059] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/23/2020] [Accepted: 07/28/2020] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE The Vitamin D receptor (VDR) has been positively associated with skeletal muscle mass, function and regeneration. Mechanistic studies have focused on the loss of the receptor, with in vivo whole-body knockout models demonstrating reduced myofibre size and function and impaired muscle development. To understand the mechanistic role upregulation of the VDR elicits in muscle mass/health, we studied the impact of VDR over-expression (OE) in vivo before exploring the importance of VDR expression upon muscle hypertrophy in humans. METHODS Wistar rats underwent in vivo electrotransfer (IVE) to overexpress the VDR in the Tibialis anterior (TA) muscle for 10 days, before comprehensive physiological and metabolic profiling to characterise the influence of VDR-OE on muscle protein synthesis (MPS), anabolic signalling and satellite cell activity. Stable isotope tracer (D2O) techniques were used to assess sub-fraction protein synthesis, alongside RNA-Seq analysis. Finally, human participants underwent 20 wks of resistance exercise training, with body composition and transcriptomic analysis. RESULTS Muscle VDR-OE yielded total protein and RNA accretion, manifesting in increased myofibre area, i.e., hypertrophy. The observed increases in MPS were associated with enhanced anabolic signalling, reflecting translational efficiency (e.g., mammalian target of rapamycin (mTOR-signalling), with no effects upon protein breakdown markers being observed. Additionally, RNA-Seq illustrated marked extracellular matrix (ECM) remodelling, while satellite cell content, markers of proliferation and associated cell-cycled related gene-sets were upregulated. Finally, induction of VDR mRNA correlated with muscle hypertrophy in humans following long-term resistance exercise type training. CONCLUSION VDR-OE stimulates muscle hypertrophy ostensibly via heightened protein synthesis, translational efficiency, ribosomal expansion and upregulation of ECM remodelling-related gene-sets. Furthermore, VDR expression is a robust marker of the hypertrophic response to resistance exercise in humans. The VDR is a viable target of muscle maintenance through testable Vitamin D molecules, as active molecules and analogues.
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Affiliation(s)
- Joseph J Bass
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Asif Nakhuda
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Colleen S Deane
- Department of Sport and Health Sciences, University of Exeter, EX1 2LU, UK
| | - Matthew S Brook
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Daniel J Wilkinson
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Bethan E Phillips
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Andrew Philp
- Mitochondrial Metabolism and Ageing Laboratory, Diabetes and Metabolism Division, Garvan Institute of Medical Research, NSW, 2010, Australia; School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, B15 2TT, UK
| | - Janelle Tarum
- School of Health Sciences, Örebro University, 70182, Sweden
| | - Fawzi Kadi
- School of Health Sciences, Örebro University, 70182, Sweden
| | - Ditte Andersen
- Molecular Physiology of Diabetes Laboratory, Dept. of Comparative Biomedical Sciences, Royal Veterinary College, NW1 0TU, UK
| | - Amadeo Muñoz Garcia
- Institute of Metabolism and Systems Research, The University of Birmingham, Birmingham, UK; Department of Bioinformatics - BiGCaT, NUTRIM School of Nutrition and Metabolism in Translational Research, Maastricht University, Maastricht, the Netherlands
| | - Ken Smith
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Iain J Gallagher
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, FK9 4LA, UK
| | - Nathaniel J Szewczyk
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK
| | - Mark E Cleasby
- Molecular Physiology of Diabetes Laboratory, Dept. of Comparative Biomedical Sciences, Royal Veterinary College, NW1 0TU, UK
| | - Philip J Atherton
- MRC/ARUK Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR), Nottingham Biomedical Research Centre (BRC), School of Medicine, University of Nottingham, DE22 3DT, UK.
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9
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Ramaian Santhaseela A, Jayavelu T. Does mTORC1 inhibit autophagy at dual stages?: A possible role of mTORC1 in late-stage autophagy inhibition in addition to its known early-stage autophagy inhibition. Bioessays 2020; 43:e2000187. [PMID: 33165974 DOI: 10.1002/bies.202000187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 10/13/2020] [Accepted: 10/13/2020] [Indexed: 11/09/2022]
Abstract
Extensive studies have attributed the lysosomal localization of the mechanistic target of rapamycin complex 1 (mTORC1) during its activation. However, the exact biological significance of this lysosomal localization of mTORC1 remains ill-defined. Interestingly, findings have shown that localization of the lysosome itself is altered under conditions influencing mTORC1 activity. In this perspective, we hypothesize that the localization of mTORC1 and lysosome could be interconnected in a way that manifests regulation of autophagy that is already under progression at the time of mTORC1 activation. This provides a new possibility for autophagy regulation whose complete mechanistic insights remain to be determined.
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10
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Xiao J, Zhu S, Guan H, Zheng Y, Li F, Zhang X, Guo H, Wang X, Ye Z. AMPK alleviates high uric acid-induced Na +-K +-ATPase signaling impairment and cell injury in renal tubules. Exp Mol Med 2019; 51:1-14. [PMID: 31118410 PMCID: PMC6531502 DOI: 10.1038/s12276-019-0254-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 01/30/2019] [Accepted: 02/08/2019] [Indexed: 12/22/2022] Open
Abstract
One of the mechanisms in hyperuricemia (HUA)-induced renal tubular injury is the impairment of Na+-K+-ATPase (NKA) signaling, which further triggers inflammation, autophagy, and mitochondrial dysfunction and leads to cell injury. Here, we used RNA sequencing to screen the most likely regulators of NKA signaling and found that the liver kinase B1(LKB1)/adenosine monophosphate (AMP)-activated protein kinase (AMPK)/ mammalian target of rapamycin (mTOR) pathway was the most abundantly enriched pathway in HUA. AMPK is a key regulator of cell energy metabolism; hence, we examined the effect of AMPK on HUA-induced dysregulation of NKA signaling and cell injury. We first detected AMPK activation in high uric acid (UA)-stimulated proximal tubular epithelial cells (PTECs). We further found that sustained treatment with the AMPK activator 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR), but not the AMPK inhibitor Compound C, significantly alleviated UA-induced reductions in NKA activity and NKA α1 subunit expression on the cell membrane by reducing NKA degradation in lysosomes; sustained AICAR treatment also significantly alleviated activation of the NKA downstream molecules Src and interleukin-1β (IL-1β) in PTECs. AICAR further alleviated high UA-induced apoptosis, autophagy, and mitochondrial dysfunction. Although AMPK activation by metformin did not reduce serum UA levels in hyperuricemic rats, it significantly alleviated HUA-induced renal tubular injury and NKA signaling impairment in vivo with effects similar to those of febuxostat. Our study suggests that AMPK activation may temporarily compensate for HUA-induced renal injury. Sustained AMPK activation could reduce lysosomal NKA degradation and maintain NKA function, thus alleviating NKA downstream inflammation and protecting tubular cells from high UA-induced renal tubular injury. High serum levels of uric acid cause kidney tissue damage through cellular processes that have now been identified by researchers in China. Uric acid is a common component of urine, but causes damage if it is present in high levels in the blood (hyperuricemia). While investigating the mechanisms behind hyperuricemia, Zhibin Ye and co-workers at Fudan University in Shanghai recently showed that impairment of the Na+-K+-ATPase (NKA) signaling pathway, which regulates uric acid transportation through the kidneys, is a crucial feature of renal damage progression. The team have now shown that NKA is regulated by the AMP-activated protein kinase (AMPK) pathway, and that AMPK is enriched during the initial phases of hyperuricemia. Studies on rat models indicated that sustained AMPK activation restored NKA signaling, limiting damage from hyperuricemia.
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Affiliation(s)
- Jing Xiao
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Sibo Zhu
- School of Life Sciences, Fudan University, Shanghai, People's Republic of China
| | - Haochen Guan
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Yuqi Zheng
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Fengqin Li
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Xiaoli Zhang
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Hui Guo
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Xiaojun Wang
- Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China
| | - Zhibin Ye
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China. .,Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong Hospital Affiliated to Fudan University, Shanghai, People's Republic of China.
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11
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Pasini E, Flati V, Comini L, Olivares A, Bertella E, Corsetti G, Vitacca M. Mammalian Target of Rapamycin: Is It Relevant to COPD Pathogenesis or Treatment? COPD 2019; 16:89-92. [PMID: 31056947 DOI: 10.1080/15412555.2019.1583726] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The mammalian target of rapamycin (mTOR) signalling pathway regulates fundamental metabolic processes such as inflammation, autophagy and apoptosis, all of which influence cell fate. Recent experimental data suggest that mTOR signalling is involved in many diseases, including lung diseases, but with contrasting data. Overexpression of mTOR and its signalling proteins have been linked to lung cell senescence and development of emphysema, pulmonary hypertension and inflammation. On the other hand, mTOR inhibitors, as rapamycin and/or its derivatives, restore corticosteroid sensitivity in peripheral blood mononuclear cells from chronic obstructive pulmonary disease (COPD) patients, and overexpression of mTOR suppresses cigarette smoke-induced inflammation and emphysema, suggesting that induction of mTOR expression/activity might be useful to treat COPD. This apparent discrepancy is due to complex and heterogenic enzymatic pathway of mTOR. Translation of pre-clinical positive data on the use of mTOR inhibitors to COPD therapy needs a more in-depth knowledge of mTOR signalling.
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Affiliation(s)
- Evasio Pasini
- a Cardiac Rehabilitation of the Institute of Lumezzane , Istituti Clinici Scientifici Maugeri IRCCS , Brescia , Italy
| | - Vincenzo Flati
- b Department of Biotechnological and Applied Clinical Sciences , University of L'Aquila , L'Aquila , Italy
| | - Laura Comini
- c Scientific Direction of the Institute of Lumezzane , Istituti Clinici Scientifici Maugeri IRCCS , Brescia , Italy
| | - Adriana Olivares
- c Scientific Direction of the Institute of Lumezzane , Istituti Clinici Scientifici Maugeri IRCCS , Brescia , Italy
| | - Enrica Bertella
- d Respiratory Rehabilitation of the Institute of Lumezzane , Istituti Clinici Scientifici Maugeri IRCCS , Brescia , Italy
| | - Giovanni Corsetti
- e Division of Human Anatomy and Physiopathology, Department of Clinical & Experimental Sciences , University of Brescia , Brescia , Italy
| | - Michele Vitacca
- d Respiratory Rehabilitation of the Institute of Lumezzane , Istituti Clinici Scientifici Maugeri IRCCS , Brescia , Italy
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12
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Gan L, Seki A, Shen K, Iyer H, Han K, Hayer A, Wollman R, Ge X, Lin JR, Dey G, Talbot WS, Meyer T. The lysosomal GPCR-like protein GPR137B regulates Rag and mTORC1 localization and activity. Nat Cell Biol 2019; 21:614-626. [PMID: 31036939 PMCID: PMC6649673 DOI: 10.1038/s41556-019-0321-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 03/27/2019] [Indexed: 12/13/2022]
Abstract
Cell growth is controlled by a lysosomal signaling complex containing Rag small GTPases and mTORC1 kinase. Here we carried out a microscopy-based genome-wide human siRNA screen and discovered a lysosome-localized G-protein coupled receptor (GPCR)-like protein, GPR137B, that interacts with Rag GTPases, increases Rag localization and activity, and thereby regulates mTORC1 translocation and activity. High GPR137B expression can recruit and activate mTORC1 in the absence of amino acids. Furthermore, GPR137B also regulates the dissociation of activated Rag from lysosomes, suggesting that GPR137B controls a cycle of Rag activation and dissociation from lysosomes. GPR137B knockout cells exhibited defective autophagy and an expanded lysosome compartment, similar to Rag knockout cells. Like zebrafish RagA mutants, GPR137B mutant zebrafish had upregulated TFEB target gene expression and an expanded lysosome compartment in microglia. Thus, GPR137B is a GPCR-like lysosomal regulatory protein that controls dynamic Rag and mTORC1 localization and activity as well as lysosome morphology.
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Affiliation(s)
- Lin Gan
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Akiko Seki
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Kimberle Shen
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Harini Iyer
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Kyuho Han
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Arnold Hayer
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Roy Wollman
- Department of Integrative Biology and Physiology and Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Xuecai Ge
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Jerry R Lin
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Gautam Dey
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA.
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13
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Sanders SS, De Simone FI, Thomas GM. mTORC1 Signaling Is Palmitoylation-Dependent in Hippocampal Neurons and Non-neuronal Cells and Involves Dynamic Palmitoylation of LAMTOR1 and mTOR. Front Cell Neurosci 2019; 13:115. [PMID: 31001086 PMCID: PMC6454084 DOI: 10.3389/fncel.2019.00115] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/08/2019] [Indexed: 11/13/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR) Complex 1 (mTORC1) controls growth and proliferation of non-neuronal cells, while during neuronal development mTORC1 responds to glutamate and neurotrophins to promote neuronal migration and dendritic arborization. Recent studies reveal that mTORC1 signaling complexes are assembled on lysosomal membranes, but how mTORC1 membrane targeting is regulated is not fully clear. Our examination of palmitoyl-proteomic databases and additional bioinformatic analyses revealed that several mTORC1 proteins are predicted to undergo covalent modification with the lipid palmitate. This process, palmitoylation, can dynamically target proteins to specific membranes but its roles in mTORC1 signaling are not well described. Strikingly, we found that acute pharmacological inhibition of palmitoylation prevents amino acid-dependent mTORC1 activation in HEK293T cells and brain-derived neurotrophic factor (BDNF)-dependent mTORC1 activation in hippocampal neurons. We sought to define the molecular basis for this finding and found that the mTORC1 proteins LAMTOR1 and mTOR itself are directly palmitoylated, while several other mTORC1 proteins are not palmitoylated, despite strong bioinformatic prediction. Interestingly, palmitoylation of LAMTOR1, whose anchoring on lysosomal membranes is important for mTORC1 signaling, was rapidly increased prior to mTORC1 activation. In contrast, mTOR palmitoylation was decreased by stimuli that activate mTORC1. These findings reveal that specific key components of the mTOR pathway are dynamically palmitoylated, suggesting that palmitoylation is not merely permissive for mTOR activation but is instead actively involved in mTORC1-dependent signaling.
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Affiliation(s)
- Shaun S Sanders
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | - Francesca I De Simone
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | - Gareth M Thomas
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States.,Department of Anatomy and Cell Biology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
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14
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Leucine regulates α-amylase and trypsin synthesis in dairy calf pancreatic tissue in vitro via the mammalian target of rapamycin signalling pathway. Animal 2019; 13:1899-1906. [DOI: 10.1017/s1751731118003683] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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15
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Clatici VG, Voicu C, Voaides C, Roseanu A, Icriverzi M, Jurcoane S. Diseases of Civilization - Cancer, Diabetes, Obesity and Acne - the Implication of Milk, IGF-1 and mTORC1. MAEDICA 2018; 13:273-281. [PMID: 30774725 PMCID: PMC6362881 DOI: 10.26574/maedica.2018.13.4.273] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Nutrition and food are one of the most complex aspects of human lives, being influenced by biochemical, psychological, social and cultural factors. The Western diet is the prototype of modern dietary pattern and is mainly characterized by the intake of large amounts of red meat, dairy products, refined grains and sugar. Large amounts of scientific evidence positively correlate Western diet to acne, obesity, diabetes, heart disease and cancer, the so-called "diseases of civilization". The pathophysiological common ground of all these pathologies is the IGF-1 and mTORC pathways, which will be disscussed further in this paper.
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Affiliation(s)
| | | | | | - Anca Roseanu
- Department of Ligand-Receptor Interaction, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Madalina Icriverzi
- Department of Ligand-Receptor Interaction, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
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16
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Phenylalanine regulates initiation of digestive enzyme mRNA translation in pancreatic acinar cells and tissue segments in dairy calves. Biosci Rep 2018; 38:BSR20171189. [PMID: 29263147 PMCID: PMC5784178 DOI: 10.1042/bsr20171189] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 12/14/2017] [Accepted: 12/20/2017] [Indexed: 01/13/2023] Open
Abstract
As new nutritional strategies for ruminant are designed to change production efficiency by improving the supply of rumen protect protein, lipid, and even starch, the digestive system must fit to utilize these increased nutrient supplies, especially the pancreas. The objective of this study was to investigate the effects of phenylalanine (Phe) on digestive enzymes synthesis or secretion and cellular signaling in pancreatic acinar (PA) cells of dairy calves. The PA cells isolated from fresh pancreas of dairy calves, and cultured in completed RIPA 1640 medium with no fetal serum but 0, 0.15 and 0.45 mM Phe at 37°C in CO2 incubator for 120 min. The pancreatic tissue segments (PTS) was cut approximately 2 × 2 mm from the fresh pancreas, and incubated in oxygenated Krebs-Ringer bicarbonate (KRB) buffer containing 0 or 0.35 mM Phe at 39°C for 180 min, and the samples were collected every 60 min after incubation. In PA cells, Phe increased (P < 0.05) the α-amylase secretion and mRNA expression, the phosphorylation of ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4EBP1). In PTS, the Phe increased (P < 0.05) α-amylase and trypsin synthesis, secretion and mRNA expression, as well as the phosphorylation of S6K1 and 4EBP1. Conclusively, these results suggested that Phe regulates the synthesis or secretion of α-amylase, trypsin and lipase through mRNA translation initiation factors – S6K1 and 4EBP1.
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17
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mTORC1 as the main gateway to autophagy. Essays Biochem 2017; 61:565-584. [PMID: 29233869 PMCID: PMC5869864 DOI: 10.1042/ebc20170027] [Citation(s) in RCA: 356] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 10/19/2017] [Accepted: 10/20/2017] [Indexed: 12/16/2022]
Abstract
Cells and organisms must coordinate their metabolic activity with changes in their environment to ensure their growth only when conditions are favourable. In order to maintain cellular homoeostasis, a tight regulation between the synthesis and degradation of cellular components is essential. At the epicentre of the cellular nutrient sensing is the mechanistic target of rapamycin complex 1 (mTORC1) which connects environmental cues, including nutrient and growth factor availability as well as stress, to metabolic processes in order to preserve cellular homoeostasis. Under nutrient-rich conditions mTORC1 promotes cell growth by stimulating biosynthetic pathways, including synthesis of proteins, lipids and nucleotides, and by inhibiting cellular catabolism through repression of the autophagic pathway. Its close signalling interplay with the energy sensor AMP-activated protein kinase (AMPK) dictates whether the cell actively favours anabolic or catabolic processes. Underlining the role of mTORC1 in the coordination of cellular metabolism, its deregulation is linked to numerous human diseases ranging from metabolic disorders to many cancers. Although mTORC1 can be modulated by a number of different inputs, amino acids represent primordial cues that cannot be compensated for by any other stimuli. The understanding of how amino acids signal to mTORC1 has increased considerably in the last years; however this area of research remains a hot topic in biomedical sciences. The current ideas and models proposed to explain the interrelationship between amino acid sensing, mTORC1 signalling and autophagy is the subject of the present review.
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18
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Lim JA, Li L, Shirihai OS, Trudeau KM, Puertollano R, Raben N. Modulation of mTOR signaling as a strategy for the treatment of Pompe disease. EMBO Mol Med 2017; 9:353-370. [PMID: 28130275 PMCID: PMC5331267 DOI: 10.15252/emmm.201606547] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mechanistic target of rapamycin (mTOR) coordinates biosynthetic and catabolic processes in response to multiple extracellular and intracellular signals including growth factors and nutrients. This serine/threonine kinase has long been known as a critical regulator of muscle mass. The recent finding that the decision regarding its activation/inactivation takes place at the lysosome undeniably brings mTOR into the field of lysosomal storage diseases. In this study, we have examined the involvement of the mTOR pathway in the pathophysiology of a severe muscle wasting condition, Pompe disease, caused by excessive accumulation of lysosomal glycogen. Here, we report the dysregulation of mTOR signaling in the diseased muscle cells, and we focus on potential sites for therapeutic intervention. Reactivation of mTOR in the whole muscle of Pompe mice by TSC knockdown resulted in the reversal of atrophy and a striking removal of autophagic buildup. Of particular interest, we found that the aberrant mTOR signaling can be reversed by arginine. This finding can be translated into the clinic and may become a paradigm for targeted therapy in lysosomal, metabolic, and neuromuscular diseases.
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Affiliation(s)
- Jeong-A Lim
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.,Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Lishu Li
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Orian S Shirihai
- Department of Medicine, Obesity and Nutrition Section, Evans Biomedical Research Center, Boston University School of Medicine, Boston, MA, USA
| | - Kyle M Trudeau
- Department of Medicine, Obesity and Nutrition Section, Evans Biomedical Research Center, Boston University School of Medicine, Boston, MA, USA
| | - Rosa Puertollano
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nina Raben
- Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
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19
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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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20
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Mlitz V, Gendronneau G, Berlin I, Buchberger M, Eckhart L, Tschachler E. The Expression of the Endogenous mTORC1 Inhibitor Sestrin 2 Is Induced by UVB and Balanced with the Expression Level of Sestrin 1. PLoS One 2016; 11:e0166832. [PMID: 27861561 PMCID: PMC5115827 DOI: 10.1371/journal.pone.0166832] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 11/05/2016] [Indexed: 01/28/2023] Open
Abstract
Sestrin 2 (SESN2) is an evolutionarily conserved regulator of mechanistic target of rapamycin complex 1 (mTORC1) which controls central cellular processes such as protein translation and autophagy. Previous studies have suggested that SESN2 itself is subjected to regulation at multiple levels. Here, we investigated the expression of SESN2 in the skin and in isolated skin cells. SESN2 was detected by immunofluorescence analysis in fibroblasts and keratinocytes of human skin. Differentiation of epidermal keratinocytes was not associated with altered SESN2 expression and siRNA-mediated knockdown of SESN2 did not impair stratum corneum formation in vitro. However, SESN2 was increased in both cell types when the expression of its paralog SESN1 was blocked by siRNA-mediated knock down, indicating a compensatory mechanism for the control of expression. Irradiation with UVB but not with UVA significantly increased SESN2 expression in both keratinocytes and fibroblasts. Upregulation of SESN2 expression could be completely blocked by suppression of p53. These results suggest that SESN2 is dispensable for normal epidermal keratinization but involved in the UVB stress response of skin cells.
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Affiliation(s)
- Veronika Mlitz
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | | | - Irina Berlin
- Department of Biology and Women Beauty, Chanel R&T, Pantin, France
| | - Maria Buchberger
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
| | - Leopold Eckhart
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
- * E-mail: (ET); (LE)
| | - Erwin Tschachler
- Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria
- * E-mail: (ET); (LE)
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21
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Hu Y, Carraro-Lacroix LR, Wang A, Owen C, Bajenova E, Corey PN, Brumell JH, Voronov I. Lysosomal pH Plays a Key Role in Regulation of mTOR Activity in Osteoclasts. J Cell Biochem 2016. [PMID: 26212375 DOI: 10.1002/jcb.25287] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian target of rapamycin (mTOR) is a serine/threonine kinase involved in the regulation of cell growth. It has been shown to play an important role in osteoclast differentiation, particularly at the earlier stages of osteoclastogenesis. mTOR activation and function, as part of mTORC1 complex, is dependent on lysosomal localization and the vacuolar H(+) -ATPase (V-ATPase) activity; however, the precise mechanism is still not well understood. Using primary mouse osteoclasts that are known to have higher lysosomal pH due to R740S mutation in the V-ATPase a3 subunit, we investigated the role of lysosomal pH in mTORC1 signaling. Our results demonstrated that +/R740S cells had increased basal mTOR protein levels and mTORC1 activity compared to +/+ osteoclasts, while mTOR gene expression was decreased. Treatment with lysosomal inhibitors chloroquine and ammonium chloride, compounds known to raise lysosomal pH, significantly increased mTOR protein levels in +/+ cells, confirming the importance of lysosomal pH in mTOR signaling. These results also suggested that mTOR could be degraded in the lysosome. To test this hypothesis, we cultured osteoclasts with chloroquine or proteasomal inhibitor MG132. Both chloroquine and MG132 increased mTOR and p-mTOR protein levels in +/+ osteoclasts, suggesting that mTOR undergoes both lysosomal and proteasomal degradation. Treatment with cycloheximide, an inhibitor of new protein synthesis, confirmed that mTOR is constitutively expressed and degraded. These results show that, in osteoclasts, the lysosome plays a key role not only in mTOR activation but also in its deactivation through protein degradation, representing a novel molecular mechanism of mTOR regulation.
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Affiliation(s)
- Yingwei Hu
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.,Institute of Dental Medicine, Qilu Hospital, Shandong University, Jinan, China
| | | | - Andrew Wang
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Celeste Owen
- Centre for Modeling Human Disease, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Elena Bajenova
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Paul N Corey
- Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
| | - John H Brumell
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Irina Voronov
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
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22
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GCN2 contributes to mTORC1 inhibition by leucine deprivation through an ATF4 independent mechanism. Sci Rep 2016; 6:27698. [PMID: 27297692 PMCID: PMC4906353 DOI: 10.1038/srep27698] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 05/19/2016] [Indexed: 12/22/2022] Open
Abstract
It is well known that the GCN2 and mTORC1 signaling pathways are regulated by amino acids and share common functions, in particular the control of translation. The regulation of GCN2 activity by amino acid availability relies on the capacity of GCN2 to sense the increased levels of uncharged tRNAs upon amino acid scarcity. In contrast, despite recent progress in the understanding of the regulation of mTORC1 by amino acids, key aspects of this process remain unsolved. In particular, while leucine is well known to be a potent regulator of mTORC1, the mechanisms by which this amino acid is sensed and control mTORC1 activity are not well defined. Our data establish that GCN2 is involved in the inhibition of mTORC1 upon leucine or arginine deprivation. However, the activation of GCN2 alone is not sufficient to inhibit mTORC1 activity, indicating that leucine and arginine exert regulation via additional mechanisms. While the mechanism by which GCN2 contributes to the initial step of mTORC1 inhibition involves the phosphorylation of eIF2α, we show that it is independent of the downstream transcription factor ATF4. These data point to a novel role for GCN2 and phosphorylation of eIF2α in the control of mTORC1 by certain amino acids.
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23
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Weikel KA, Ruderman NB, Cacicedo JM. Unraveling the actions of AMP-activated protein kinase in metabolic diseases: Systemic to molecular insights. Metabolism 2016; 65:634-645. [PMID: 27085772 PMCID: PMC4834453 DOI: 10.1016/j.metabol.2016.01.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 01/08/2016] [Accepted: 01/09/2016] [Indexed: 12/13/2022]
Abstract
AMP-activated protein kinase (AMPK) plays a critical role both in sensing and regulating cellular energy state. In experimental animals, its activation has been shown to reduce the risk of obesity and diabetes-related co-morbidities such as insulin resistance, the metabolic syndrome and atherosclerotic cardiovascular disease. However, in humans, AMPK activation alone often does not completely resolve these conditions. Thus, an improved understanding of AMPK action and regulation in metabolic and other diseases is needed. Herein, we provide a brief description of the enzymatic regulation of AMPK and review its role in maintaining energy homeostasis. We then discuss tissue-specific actions of AMPK that become distorted during such conditions as obesity, type 2 diabetes and certain cancers. Finally, we explore recent findings regarding the interactions of AMPK with mammalian target of rapamycin complex 1 and the lysosome and discuss how changes in these relationships during overnutrition may lead to AMPK dysfunction. A more thorough understanding of AMPK's molecular interactions during diseases of overnutrition may provide key insights for the development of AMPK-based combinatorial treatments for metabolic disease.
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Affiliation(s)
- Karen A Weikel
- Department of Medicine, Boston University School of Medicine and Boston Medical Center, 650 Albany Street, Boston, MA, 02118, USA.
| | - Neil B Ruderman
- Department of Medicine, Boston University School of Medicine and Boston Medical Center, 650 Albany Street, Boston, MA, 02118, USA
| | - José M Cacicedo
- Department of Medicine, Boston University School of Medicine and Boston Medical Center, 650 Albany Street, Boston, MA, 02118, USA
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24
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Abstract
Cell metabolism and growth are matched to nutrient availability via the amino-acid-regulated mechanistic target of rapamycin complex 1 (mTORC1). Transporters have emerged as important amino acid sensors controlling mTOR recruitment and activation at the surface of multiple intracellular compartments. Classically, this has involved late endosomes and lysosomes, but now, in a recent twist, also the Golgi apparatus. Here we propose a model in which specific amino acids in assorted compartments activate different mTORC1 complexes, which may have distinct drug sensitivities and functions. We will discuss the implications of this for mTORC1 function in health and disease.
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Affiliation(s)
- Deborah C I Goberdhan
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford OX1 3QX, UK.
| | - Clive Wilson
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford OX1 3QX, UK
| | - Adrian L Harris
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
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25
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Tsokanos FF, Albert MA, Demetriades C, Spirohn K, Boutros M, Teleman AA. eIF4A inactivates TORC1 in response to amino acid starvation. EMBO J 2016; 35:1058-76. [PMID: 26988032 PMCID: PMC4868951 DOI: 10.15252/embj.201593118] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 02/19/2016] [Indexed: 12/20/2022] Open
Abstract
Amino acids regulate TOR complex 1 (TORC1) via two counteracting mechanisms, one activating and one inactivating. The presence of amino acids causes TORC1 recruitment to lysosomes where TORC1 is activated by binding Rheb. How the absence of amino acids inactivates TORC1 is less well understood. Amino acid starvation recruits the TSC1/TSC2 complex to the vicinity of TORC1 to inhibit Rheb; however, the upstream mechanisms regulating TSC2 are not known. We identify here the eIF4A-containing eIF4F translation initiation complex as an upstream regulator of TSC2 in response to amino acid withdrawal in Drosophila We find that TORC1 and translation preinitiation complexes bind each other. Cells lacking eIF4F components retain elevated TORC1 activity upon amino acid removal. This effect is specific for eIF4F and not a general consequence of blocked translation. This study identifies specific components of the translation machinery as important mediators of TORC1 inactivation upon amino acid removal.
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Affiliation(s)
- Foivos-Filippos Tsokanos
- Division of Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Marie-Astrid Albert
- Division of Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Constantinos Demetriades
- Division of Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Kerstin Spirohn
- Department of Cell and Molecular Biology, Medical Faculty Mannheim, German Cancer Research Center (DKFZ), Division of Signaling and Functional Genomics and Heidelberg University, Heidelberg, Germany
| | - Michael Boutros
- Department of Cell and Molecular Biology, Medical Faculty Mannheim, German Cancer Research Center (DKFZ), Division of Signaling and Functional Genomics and Heidelberg University, Heidelberg, Germany
| | - Aurelio A Teleman
- Division of Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany
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Powis K, De Virgilio C. Conserved regulators of Rag GTPases orchestrate amino acid-dependent TORC1 signaling. Cell Discov 2016; 2:15049. [PMID: 27462445 PMCID: PMC4860963 DOI: 10.1038/celldisc.2015.49] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 12/02/2015] [Indexed: 12/16/2022] Open
Abstract
The highly conserved target of rapamycin complex 1 (TORC1) is the central component of a signaling network that couples a vast range of internal and external stimuli to cell growth, proliferation and metabolism. TORC1 deregulation is associated with a number of human pathologies, including many cancers and metabolic disorders, underscoring its importance in cellular and organismal growth control. The activity of TORC1 is modulated by multiple inputs; however, the presence of amino acids is a stimulus that is essential for its activation. Amino acid sufficiency is communicated to TORC1 via the highly conserved family of Rag GTPases, which assemble as heterodimeric complexes on lysosomal/vacuolar membranes and are regulated by their guanine nucleotide loading status. Studies in yeast, fly and mammalian model systems have revealed a multitude of conserved Rag GTPase modulators, which have greatly expanded our understanding of amino acid sensing by TORC1. Here we review the major known modulators of the Rag GTPases, focusing on recent mechanistic insights that highlight the evolutionary conservation and divergence of amino acid signaling to TORC1.
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Affiliation(s)
- Katie Powis
- Department of Biology, University of Fribourg , Fribourg, Switzerland
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Wuolikainen A, Jonsson P, Ahnlund M, Antti H, Marklund SL, Moritz T, Forsgren L, Andersen PM, Trupp M. Multi-platform mass spectrometry analysis of the CSF and plasma metabolomes of rigorously matched amyotrophic lateral sclerosis, Parkinson's disease and control subjects. MOLECULAR BIOSYSTEMS 2016; 12:1287-98. [PMID: 26883206 DOI: 10.1039/c5mb00711a] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) are protein-aggregation diseases that lack clear molecular etiologies. Biomarkers could aid in diagnosis, prognosis, planning of care, drug target identification and stratification of patients into clinical trials. We sought to characterize shared and unique metabolite perturbations between ALS and PD and matched controls selected from patients with other diagnoses, including differential diagnoses to ALS or PD that visited our clinic for a lumbar puncture. Cerebrospinal fluid (CSF) and plasma from rigorously age-, sex- and sampling-date matched patients were analyzed on multiple platforms using gas chromatography (GC) and liquid chromatography (LC)-mass spectrometry (MS). We applied constrained randomization of run orders and orthogonal partial least squares projection to latent structure-effect projections (OPLS-EP) to capitalize upon the study design. The combined platforms identified 144 CSF and 196 plasma metabolites with diverse molecular properties. Creatine was found to be increased and creatinine decreased in CSF of ALS patients compared to matched controls. Glucose was increased in CSF of ALS patients and α-hydroxybutyrate was increased in CSF and plasma of ALS patients compared to matched controls. Leucine, isoleucine and ketoleucine were increased in CSF of both ALS and PD. Together, these studies, in conjunction with earlier studies, suggest alterations in energy utilization pathways and have identified and further validated perturbed metabolites to be used in panels of biomarkers for the diagnosis of ALS and PD.
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Ham DJ, Lynch GS, Koopman R. Amino acid sensing and activation of mechanistic target of rapamycin complex 1: implications for skeletal muscle. Curr Opin Clin Nutr Metab Care 2016; 19:67-73. [PMID: 26560525 DOI: 10.1097/mco.0000000000000240] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE OF REVIEW This article evaluates recent studies on the mechanisms involved in sensing changes in amino acid availability and activation of the mechanistic target of rapamycin complex 1 (mTORC1). RECENT FINDINGS mTORC1 is sensitive to changes in amino acid availability and a well known regulator of protein turnover. The mechanisms of amino acid sensing and mTORC1 signaling are emerging with multiple potential sensors (e.g., solute carrier family 38, member 9, lysosomal protein transmembrane 4 beta/solute carrier family 7, member 5-solute carrier family 3, member 2) and signal transducers (e.g., Sestrins, ADP-ribosylation factor 1, and microspherule protein 1) identified. Studies in various cell lines have unveiled the importance of the lysosome in amino acid sensing and signal transmission. SUMMARY Recent discoveries in amino acid sensing highlight a complex scenario, whereby mTORC1 is not merely sensitive to some amino acids and not others, but where specific amino acids are sensed by specific pathways under specific conditions. The physiological purpose of such an arrangement remains to be unraveled, but it would allow mTORC1 to precisely regulate growth during different metabolic conditions. Understanding the mechanisms responsible for sensing amino acid availability and regulating mTORC1 activity is an important prerequisite for the development of nutritional strategies to combat skeletal muscle wasting disorders.
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Affiliation(s)
- Daniel J Ham
- Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne, Victoria, Australia
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Xu W, Bai K, He J, Su W, Dong L, Zhang L, Wang T. Leucine improves growth performance of intrauterine growth retardation piglets by modifying gene and protein expression related to protein synthesis. Nutrition 2016; 32:114-21. [DOI: 10.1016/j.nut.2015.07.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 05/31/2015] [Accepted: 07/07/2015] [Indexed: 01/10/2023]
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Abstract
Acne vulgaris, an epidemic inflammatory skin disease of adolescence, is closely related to Western diet. Three major food classes that promote acne are: 1) hyperglycemic carbohydrates, 2) milk and dairy products, 3) saturated fats including trans-fats and deficient ω-3 polyunsaturated fatty acids (PUFAs). Diet-induced insulin/insulin-like growth factor (IGF-1)-signaling is superimposed on elevated IGF-1 levels during puberty, thereby unmasking the impact of aberrant nutrigenomics on sebaceous gland homeostasis. Western diet provides abundant branched-chain amino acids (BCAAs), glutamine, and palmitic acid. Insulin and IGF-1 suppress the activity of the metabolic transcription factor forkhead box O1 (FoxO1). Insulin, IGF-1, BCAAs, glutamine, and palmitate activate the nutrient-sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1), the key regulator of anabolism and lipogenesis. FoxO1 is a negative coregulator of androgen receptor, peroxisome proliferator-activated receptor-γ (PPARγ), liver X receptor-α, and sterol response element binding protein-1c (SREBP-1c), crucial transcription factors of sebaceous lipogenesis. mTORC1 stimulates the expression of PPARγ and SREBP-1c, promoting sebum production. SREBP-1c upregulates stearoyl-CoA- and Δ6-desaturase, enhancing the proportion of monounsaturated fatty acids in sebum triglycerides. Diet-mediated aberrations in sebum quantity (hyperseborrhea) and composition (dysseborrhea) promote Propionibacterium acnes overgrowth and biofilm formation with overexpression of the virulence factor triglyceride lipase increasing follicular levels of free palmitate and oleate. Free palmitate functions as a "danger signal," stimulating toll-like receptor-2-mediated inflammasome activation with interleukin-1β release, Th17 differentiation, and interleukin-17-mediated keratinocyte proliferation. Oleate stimulates P. acnes adhesion, keratinocyte proliferation, and comedogenesis via interleukin-1α release. Thus, diet-induced metabolomic alterations promote the visible sebofollicular inflammasomopathy acne vulgaris. Nutrition therapy of acne has to increase FoxO1 and to attenuate mTORC1/SREBP-1c signaling. Patients should balance total calorie uptake and restrict refined carbohydrates, milk, dairy protein supplements, saturated fats, and trans-fats. A paleolithic-like diet enriched in vegetables and fish is recommended. Plant-derived mTORC1 inhibitors and ω-3-PUFAs are promising dietary supplements supporting nutrition therapy of acne vulgaris.
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Affiliation(s)
- Bodo C Melnik
- Department of Dermatology, Environmental Medicine and Health Theory, University of Osnabrück, Germany
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31
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GSK3-mediated raptor phosphorylation supports amino-acid-dependent mTORC1-directed signalling. Biochem J 2015; 470:207-21. [PMID: 26348909 PMCID: PMC4652938 DOI: 10.1042/bj20150404] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 07/09/2015] [Indexed: 01/06/2023]
Abstract
Glycogen synthase kinase-3 (GSK3) mediates phosphorylation of raptor on Ser859, which crucially supports activation of mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) signalling in response to amino acid availability. GSK3 inhibition is associated with reduced mTORC1 signalling that impacts negatively on cell growth, protein synthesis and promotes cellular autophagy. The mammalian or mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a ubiquitously expressed multimeric protein kinase complex that integrates nutrient and growth factor signals for the co-ordinated regulation of cellular metabolism and cell growth. Herein, we demonstrate that suppressing the cellular activity of glycogen synthase kinase-3 (GSK3), by use of pharmacological inhibitors or shRNA-mediated gene silencing, results in substantial reduction in amino acid (AA)-regulated mTORC1-directed signalling, as assessed by phosphorylation of multiple downstream mTORC1 targets. We show that GSK3 regulates mTORC1 activity through its ability to phosphorylate the mTOR-associated scaffold protein raptor (regulatory-associated protein of mTOR) on Ser859. We further demonstrate that either GSK3 inhibition or expression of a S859A mutated raptor leads to reduced interaction between mTOR and raptor and under these circumstances, irrespective of AA availability, there is a consequential loss in phosphorylation of mTOR substrates, such as p70S6K1 (ribosomal S6 kinase 1) and uncoordinated-51-like kinase (ULK1), which results in increased autophagic flux and reduced cellular proliferation.
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Rozas NS, Redell JB, Pita-Almenar JD, Mckenna J, Moore AN, Gambello MJ, Dash PK. Intrahippocampal glutamine administration inhibits mTORC1 signaling and impairs long-term memory. ACTA ACUST UNITED AC 2015; 22:239-46. [PMID: 25878136 PMCID: PMC4408772 DOI: 10.1101/lm.038265.115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 02/13/2015] [Indexed: 11/25/2022]
Abstract
The mechanistic Target of Rapamycin Complex 1 (mTORC1), a key regulator of protein synthesis and cellular growth, is also required for long-term memory formation. Stimulation of mTORC1 signaling is known to be dependent on the availability of energy and growth factors, as well as the presence of amino acids. In vitro studies using serum- and amino acid-starved cells have reported that glutamine addition can either stimulate or repress mTORC1 activity, depending on the particular experimental system that was used. However, these experiments do not directly address the effect of glutamine on mTORC1 activity under physiological conditions in nondeprived cells in vivo. We present experimental results indicating that intrahippocampal administration of glutamine to rats reduces mTORC1 activity. Moreover, post-training administration of glutamine impairs long-term spatial memory formation, while coadministration of glutamine with leucine had no influence on memory. Intracellular recordings in hippocampal slices showed that glutamine did not alter either excitatory or inhibitory synaptic activity, suggesting that the observed memory impairments may not result from conversion of glutamine to either glutamate or GABA. Taken together, these findings indicate that glutamine can decrease mTORC1 activity in the brain and may have implications for treatments of neurological diseases associated with high mTORC1 signaling.
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Affiliation(s)
- Natalia S Rozas
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA
| | - John B Redell
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA
| | - Juan D Pita-Almenar
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA
| | - James Mckenna
- Department of Human Genetics, Emory University, Atlanta, Georgia 30322, USA
| | - Anthony N Moore
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA
| | - Michael J Gambello
- Department of Human Genetics, Emory University, Atlanta, Georgia 30322, USA
| | - Pramod K Dash
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA
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Marcotte GR, West DWD, Baar K. The molecular basis for load-induced skeletal muscle hypertrophy. Calcif Tissue Int 2015; 96:196-210. [PMID: 25359125 PMCID: PMC4809742 DOI: 10.1007/s00223-014-9925-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 10/18/2014] [Indexed: 12/19/2022]
Abstract
In a mature (weight neutral) animal, an increase in muscle mass only occurs when the muscle is loaded sufficiently to cause an increase in myofibrillar protein balance. A tight relationship between muscle hypertrophy, acute increases in protein balance, and the activity of the mechanistic target of rapamycin complex 1 (mTORC1) was demonstrated 15 years ago. Since then, our understanding of the signals that regulate load-induced hypertrophy has evolved considerably. For example, we now know that mechanical load activates mTORC1 in the same way as growth factors, by moving TSC2 (a primary inhibitor of mTORC1) away from its target (the mTORC activator) Rheb. However, the kinase that phosphorylates and moves TSC2 is different in the two processes. Similarly, we have learned that a distinct pathway exists whereby amino acids activate mTORC1 by moving it to Rheb. While mTORC1 remains at the forefront of load-induced hypertrophy, the importance of other pathways that regulate muscle mass are becoming clearer. Myostatin, is best known for its control of developmental muscle size. However, new mechanisms to explain how loading regulates this process are suggesting that it could play an important role in hypertrophic muscle growth as well. Last, new mechanisms are highlighted for how β2 receptor agonists could be involved in load-induced muscle growth and why these agents are being developed as non-exercise-based therapies for muscle atrophy. Overall, the results highlight how studying the mechanism of load-induced skeletal muscle mass is leading the development of pharmaceutical interventions to promote muscle growth in those unwilling or unable to perform resistance exercise.
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Affiliation(s)
- George R Marcotte
- Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, CA, USA
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Rozas NS, Redell JB, McKenna J, Moore AN, Gambello MJ, Dash PK. Prolonging the survival of Tsc2 conditional knockout mice by glutamine supplementation. Biochem Biophys Res Commun 2015; 457:635-9. [PMID: 25613864 PMCID: PMC4386275 DOI: 10.1016/j.bbrc.2015.01.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 01/10/2015] [Indexed: 10/24/2022]
Abstract
The genetic disease tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by loss of function mutations in either TSC1 (hamartin) or TSC2 (tuberin), which serve as negative regulators of mechanistic target of rapamycin complex 1 (mTORC1) activity. TSC patients exhibit developmental brain abnormalities and tuber formations that are associated with neuropsychological and neurocognitive impairments, seizures and premature death. Mechanistically, TSC1 and TSC2 loss of function mutations result in abnormally high mTORC1 activity. Thus, the development of a strategy to inhibit abnormally high mTORC1 activity may have therapeutic value in the treatment of TSC. mTORC1 is a master regulator of growth processes, and its activity can be reduced by withdrawal of growth factors, decreased energy availability, and by the immunosuppressant rapamycin. Recently, glutamine has been shown to alter mTORC1 activity in a TSC1-TSC2 independent manner in cells cultured under amino acid- and serum-deprived conditions. Since starvation culture conditions are not physiologically relevant, we examined if glutamine can regulate mTORC1 in non-deprived cells and in a murine model of TSC. Our results show that glutamine can reduce phosphorylation of S6 and S6 kinase, surrogate indicators of mTORC1 activity, in both deprived and non-deprived cells, although higher concentrations were required for non-deprived cultures. When administered orally to TSC2 knockout mice, glutamine reduced S6 phosphorylation in the brain and significantly prolonged their lifespan. Taken together, these results suggest that glutamine supplementation can be used as a potential treatment for TSC.
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Affiliation(s)
- Natalia S Rozas
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, TX 77225, USA
| | - John B Redell
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, TX 77225, USA
| | - James McKenna
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Anthony N Moore
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, TX 77225, USA
| | | | - Pramod K Dash
- Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, TX 77225, USA.
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