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Liu L, Wu Y, Liu K, Zhu M, Guang S, Wang F, Liu X, Yao X, He J, Fu C. The absence of the ribosomal protein Rpl2702 elicits the MAPK-mTOR signaling to modulate mitochondrial morphology and functions. Redox Biol 2024; 73:103174. [PMID: 38701646 PMCID: PMC11088351 DOI: 10.1016/j.redox.2024.103174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 04/17/2024] [Accepted: 04/27/2024] [Indexed: 05/05/2024] Open
Abstract
Ribosomes mediate protein synthesis, which is one of the most energy-demanding activities within the cell, and mitochondria are one of the main sources generating energy. How mitochondrial morphology and functions are adjusted to cope with ribosomal defects, which can impair protein synthesis and affect cell viability, is poorly understood. Here, we used the fission yeast Schizosaccharomyces Pombe as a model organism to investigate the interplay between ribosome and mitochondria. We found that a ribosomal insult, caused by the absence of Rpl2702, activates a signaling pathway involving Sty1/MAPK and mTOR to modulate mitochondrial morphology and functions. Specifically, we demonstrated that Sty1/MAPK induces mitochondrial fragmentation in a mTOR-independent manner while both Sty1/MAPK and mTOR increases the levels of mitochondrial membrane potential and mitochondrial reactive oxygen species (mROS). Moreover, we demonstrated that Sty1/MAPK acts upstream of Tor1/TORC2 and Tor1/TORC2 and is required to activate Tor2/TORC1. The enhancements of mitochondrial membrane potential and mROS function to promote proliferation of cells bearing ribosomal defects. Hence, our study reveals a previously uncharacterized Sty1/MAPK-mTOR signaling axis that regulates mitochondrial morphology and functions in response to ribosomal insults and provides new insights into the molecular and physiological adaptations of cells to impaired protein synthesis.
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Affiliation(s)
- Ling Liu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Yifan Wu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Ke Liu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Mengdan Zhu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Shouhong Guang
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Fengsong Wang
- Department of Biology, School of Life Sciences, Anhui Medical University, Hefei, 230032, China
| | - Xing Liu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Xuebiao Yao
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China
| | - Jiajia He
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China.
| | - Chuanhai Fu
- MOE Key Laboratory for Cellular Dynamics & Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China; Anhui Key Laboratory of Cellular Dynamics and Chemical Biology & Hefei National Research Center for Interdisciplinary Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China.
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Ohtsuka H, Shimasaki T, Aiba H. Low-Molecular Weight Compounds that Extend the Chronological Lifespan of Yeasts, Saccharomyces cerevisiae, and Schizosaccharomyces pombe. Adv Biol (Weinh) 2024; 8:e2400138. [PMID: 38616173 DOI: 10.1002/adbi.202400138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/04/2024] [Indexed: 04/16/2024]
Abstract
Yeast is an excellent model organism for research for regulating aging and lifespan, and the studies have made many contributions to date, including identifying various factors and signaling pathways related to aging and lifespan. More than 20 years have passed since molecular biological perspectives are adopted in this research field, and intracellular factors and signal pathways that control aging and lifespan have evolutionarily conserved from yeast to mammals. Furthermore, these findings have been applied to control the aging and lifespan of various model organisms by adjustment of the nutritional environment, genetic manipulation, and drug treatment using low-molecular weight compounds. Among these, drug treatment is easier than the other methods, and research into drugs that regulate aging and lifespan is consequently expected to become more active. Chronological lifespan, a definition of yeast lifespan, refers to the survival period of a cell population under nondividing conditions. Herein, low-molecular weight compounds are summarized that extend the chronological lifespan of Saccharomyces cerevisiae and Schizosaccharomyces pombe, along with their intracellular functions. The low-molecular weight compounds are also discussed that extend the lifespan of other model organisms. Compounds that have so far only been studied in yeast may soon extend lifespan in other organisms.
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Affiliation(s)
- Hokuto Ohtsuka
- Laboratory of Molecular Microbiology, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Aichi, Japan
| | - Takafumi Shimasaki
- Laboratory of Molecular Microbiology, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Aichi, Japan
| | - Hirofumi Aiba
- Laboratory of Molecular Microbiology, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Aichi, Japan
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3
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Ragupathi A, Kim C, Jacinto E. The mTORC2 signaling network: targets and cross-talks. Biochem J 2024; 481:45-91. [PMID: 38270460 PMCID: PMC10903481 DOI: 10.1042/bcj20220325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/29/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024]
Abstract
The mechanistic target of rapamycin, mTOR, controls cell metabolism in response to growth signals and stress stimuli. The cellular functions of mTOR are mediated by two distinct protein complexes, mTOR complex 1 (mTORC1) and mTORC2. Rapamycin and its analogs are currently used in the clinic to treat a variety of diseases and have been instrumental in delineating the functions of its direct target, mTORC1. Despite the lack of a specific mTORC2 inhibitor, genetic studies that disrupt mTORC2 expression unravel the functions of this more elusive mTOR complex. Like mTORC1 which responds to growth signals, mTORC2 is also activated by anabolic signals but is additionally triggered by stress. mTORC2 mediates signals from growth factor receptors and G-protein coupled receptors. How stress conditions such as nutrient limitation modulate mTORC2 activation to allow metabolic reprogramming and ensure cell survival remains poorly understood. A variety of downstream effectors of mTORC2 have been identified but the most well-characterized mTORC2 substrates include Akt, PKC, and SGK, which are members of the AGC protein kinase family. Here, we review how mTORC2 is regulated by cellular stimuli including how compartmentalization and modulation of complex components affect mTORC2 signaling. We elaborate on how phosphorylation of its substrates, particularly the AGC kinases, mediates its diverse functions in growth, proliferation, survival, and differentiation. We discuss other signaling and metabolic components that cross-talk with mTORC2 and the cellular output of these signals. Lastly, we consider how to more effectively target the mTORC2 pathway to treat diseases that have deregulated mTOR signaling.
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Affiliation(s)
- Aparna Ragupathi
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Christian Kim
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Estela Jacinto
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
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4
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Villota-Salazar NA, Ramos-García VH, González-Prieto JM, Hernández-Delgado S. Effects of chemical inhibition of histone deacetylase proteins in the growth and virulence of Macrophomina phaseolina (Tassi) Goid. Rev Argent Microbiol 2023; 55:296-306. [PMID: 37296064 DOI: 10.1016/j.ram.2023.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 01/31/2023] [Accepted: 04/14/2023] [Indexed: 06/12/2023] Open
Abstract
Chromatin remodeling enzymes are important "writers", "readers" and "erasers" of the epigenetic code. These proteins are responsible for the placement, recognition, and removal of molecular marks in histone tails that trigger structural and functional changes in chromatin. This is also the case for histone deacetylases (HDACs), i.e., enzymes that remove acetyl groups from histone tails, signaling heterochromatin formation. Chromatin remodeling is necessary for cell differentiation processes in eukaryotes, and fungal pathogenesis in plants includes many adaptations to cause disease. Macrophomina phaseolina (Tassi) Goid. is a nonspecific, necrotrophic ascomycete phytopathogen that causes charcoal root disease. M. phaseolina is a frequent and highly destructive pathogen in crops such as common beans (Phaseolus vulgaris L.), particularly under both water and high temperature stresses. Here, we evaluated the effects of the classical HDAC inhibitor trichostatin A (TSA) on M. phaseolinain vitro growth and virulence. During inhibition assays, the growth of M. phaseolina in solid media, as well as the size of the microsclerotia, were reduced (p<0.05), and the colony morphology was remarkably affected. Under greenhouse experiments, treatment with TSA reduced (p<0.05) fungal virulence in common bean cv. BAT 477. Tests of LIPK, MAC1 and PMK1 gene expression during the interaction of fungi with BAT 477 revealed noticeable deregulation. Our results provide additional evidence about the role of HATs and HDACs in important biological processes of M. phaseolina.
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Affiliation(s)
- Nubia Andrea Villota-Salazar
- Biotecnología Vegetal, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. del Maestro s/n esq. Elías Piña, Col. Narciso Mendoza, 88710 Reynosa, Tamaulipas, Mexico
| | - Víctor Hugo Ramos-García
- Biotecnología Vegetal, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. del Maestro s/n esq. Elías Piña, Col. Narciso Mendoza, 88710 Reynosa, Tamaulipas, Mexico
| | - Juan Manuel González-Prieto
- Biotecnología Vegetal, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. del Maestro s/n esq. Elías Piña, Col. Narciso Mendoza, 88710 Reynosa, Tamaulipas, Mexico
| | - Sanjuana Hernández-Delgado
- Biotecnología Vegetal, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. del Maestro s/n esq. Elías Piña, Col. Narciso Mendoza, 88710 Reynosa, Tamaulipas, Mexico.
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5
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Alao JP, Legon L, Dabrowska A, Tricolici AM, Kumar J, Rallis C. Interplays of AMPK and TOR in Autophagy Regulation in Yeast. Cells 2023; 12:cells12040519. [PMID: 36831186 PMCID: PMC9953913 DOI: 10.3390/cells12040519] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 02/08/2023] Open
Abstract
Cells survey their environment and need to balance growth and anabolism with stress programmes and catabolism towards maximum cellular bioenergetics economy and survival. Nutrient-responsive pathways, such as the mechanistic target of rapamycin (mTOR) interact and cross-talk, continuously, with stress-responsive hubs such as the AMP-activated protein kinase (AMPK) to regulate fundamental cellular processes such as transcription, protein translation, lipid and carbohydrate homeostasis. Especially in nutrient stresses or deprivations, cells tune their metabolism accordingly and, crucially, recycle materials through autophagy mechanisms. It has now become apparent that autophagy is pivotal in lifespan, health and cell survival as it is a gatekeeper of clearing damaged macromolecules and organelles and serving as quality assurance mechanism within cells. Autophagy is hard-wired with energy and nutrient levels as well as with damage-response, and yeasts have been instrumental in elucidating such connectivities. In this review, we briefly outline cross-talks and feedback loops that link growth and stress, mainly, in the fission yeast Schizosaccharomyces pombe, a favourite model in cell and molecular biology.
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Matsuo Y, Marcus S, Kawamukai M. Synergistic roles of the phospholipase B homolog Plb1 and the cAMP-dependent protein kinase Pka1 in the hypertonic stress response of Schizosaccharomyces pombe. Curr Genet 2022; 68:661-674. [DOI: 10.1007/s00294-022-01253-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/02/2022] [Accepted: 08/24/2022] [Indexed: 12/01/2022]
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7
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Li ML, Ragupathi A, Patel N, Hernandez T, Magsino J, Werlen G, Brewer G, Jacinto E. The RNA-binding protein AUF1 facilitates Akt phosphorylation at the membrane. J Biol Chem 2022; 298:102437. [PMID: 36041631 PMCID: PMC9513781 DOI: 10.1016/j.jbc.2022.102437] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/18/2022] [Accepted: 08/19/2022] [Indexed: 11/25/2022] Open
Abstract
Mammalian target of rapamycin (mTOR), which is part of mTOR complex 1 (mTORC1) and mTORC2, controls cellular metabolism in response to levels of nutrients and other growth signals. A hallmark of mTORC2 activation is the phosphorylation of Akt, which becomes upregulated in cancer. How mTORC2 modulates Akt phosphorylation remains poorly understood. Here, we found that the RNA-binding protein, AUF1 (ARE/poly(U)-binding/degradation factor 1), modulates mTORC2/Akt signaling. We determined that AUF1 is required for phosphorylation of Akt at Thr308, Thr450, and Ser473 and that AUF1 also mediates phosphorylation of the mTORC2-modulated metabolic enzyme glutamine fructose-6-phosphate amidotransferase 1 at Ser243. In addition, AUF1 immunoprecipitation followed by quantitative RT–PCR revealed that the mRNAs of Akt, glutamine fructose-6-phosphate amidotransferase 1, and the mTORC2 component SIN1 associate with AUF1. Furthermore, expression of the p40 and p45, but not the p37 or p42, isoforms of AUF1 specifically mediate Akt phosphorylation. In the absence of AUF1, subcellular fractionation indicated that Akt fails to localize to the membrane. However, ectopic expression of a membrane-targeted allele of Akt is sufficient to allow Akt-Ser473 phosphorylation despite AUF1 depletion. Finally, conditions that enhance mTORC2 signaling, such as acute glutamine withdrawal, augment AUF1 phosphorylation, whereas mTOR inhibition abolishes AUF1 phosphorylation. Our findings unravel a role for AUF1 in promoting membrane localization of Akt to facilitate its phosphorylation on this cellular compartment. Targeting AUF1 could have therapeutic benefit for cancers with upregulated mTORC2/Akt signaling.
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Affiliation(s)
- Mei-Ling Li
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Aparna Ragupathi
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Nikhil Patel
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Tatiana Hernandez
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Jedrick Magsino
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Guy Werlen
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854
| | - Gary Brewer
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854.
| | - Estela Jacinto
- From the Department of Biochemistry and Molecular Biology, Rutgers Biomedical Health Sciences-Robert Wood Johnson Medical School, 683 Hoes Lane, Piscataway, NJ 08854.
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Cohen A, Pataki E, Kupiec M, Weisman R. TOR complex 2 contributes to regulation of gene expression via inhibiting Gcn5 recruitment to subtelomeric and DNA replication stress genes. PLoS Genet 2022; 18:e1010061. [PMID: 35157728 PMCID: PMC8880919 DOI: 10.1371/journal.pgen.1010061] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 02/25/2022] [Accepted: 01/28/2022] [Indexed: 11/18/2022] Open
Abstract
The fission yeast TOR complex 2 (TORC2) is required for gene silencing at subtelomeric regions and for the induction of gene transcription in response to DNA replication stress. Thus, TORC2 affects transcription regulation both negatively and positively. Whether these two TORC2-dependent functions share a common molecular mechanism is currently unknown. Here, we show that Gad8 physically interacts with proteins that regulate transcription, including subunits of the Spt-Ada-Gcn5-acetyltransferase (SAGA) complex and the BET bromodomain protein Bdf2. We demonstrate that in the absence of TORC2, Gcn5, the histone acetyltransferase subunit of SAGA, accumulates at subtelomeric genes and at non-induced promoters of DNA replication genes. Remarkably, the loss of Gcn5 in TORC2 mutant cells restores gene silencing as well as transcriptional induction in response to DNA replication stress. Loss of Bdf2 alleviates excess of Gcn5 binding in TORC2 mutant cells and also rescues the aberrant regulation of transcription in these cells. Furthermore, the loss of either SAGA or Bdf2 suppresses the sensitivity of TORC2 mutant cells to a variety of stresses, including DNA replication, DNA damage, temperature and nutrient stresses. We suggest a role of TORC2 in transcriptional regulation that is critical for gene silencing and gene induction in response to stress and involves the binding of Gcn5 to the chromatin. A fundamental characteristic of signaling pathways is their role in the regulation of gene expression. Target of rapamycin (TOR), an atypical protein kinase, is a component of two highly conserved TOR complexes: TORC1 and TORC2. These complexes affect nuclear functions through their activity in the cytoplasm as well as directly, through nuclear TOR pools. We previously showed that in fission yeast, TORC2 and its downstream substrate Gad8 associate with the chromatin fraction. We have also demonstrated that TORC2-Gad8 is required for gene silencing and transcriptional induction in response to stresses. Here, we demonstrate that Gad8 physically associates with proteins of the transcriptional machinery. We found that the loss of two positive transcriptional regulators, the SAGA complex and the bromodomain protein Bdf2, restored gene silencing as well as stress-induced transcriptional induction in TORC2 mutant cells. Our data suggests that TORC2-Gad8 contributes to gene regulation through a mechanism involving the inhibition of the accumulation of Gcn5 at the chromatin. These findings suggest a novel and possibly conserved functional relationship between TORC2, Gcn5 and Bdf2. These proteins and protein complexes are key targets in cancer therapies, thus, deciphering their functional relationship may be valuable for combination therapy in personalized medicine.
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Affiliation(s)
- Adiel Cohen
- Department of Natural and Life Sciences, The Open University of Israel, Ra’anana, Israel
| | - Emese Pataki
- Department of Natural and Life Sciences, The Open University of Israel, Ra’anana, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine & Cancer Research, Tel Aviv University, Tel Aviv, Israel
| | - Ronit Weisman
- Department of Natural and Life Sciences, The Open University of Israel, Ra’anana, Israel
- * E-mail:
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9
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Cansado J, Soto T, Franco A, Vicente-Soler J, Madrid M. The Fission Yeast Cell Integrity Pathway: A Functional Hub for Cell Survival upon Stress and Beyond. J Fungi (Basel) 2021; 8:jof8010032. [PMID: 35049972 PMCID: PMC8781887 DOI: 10.3390/jof8010032] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 12/27/2021] [Accepted: 12/27/2021] [Indexed: 12/11/2022] Open
Abstract
The survival of eukaryotic organisms during environmental changes is largely dependent on the adaptive responses elicited by signal transduction cascades, including those regulated by the Mitogen-Activated Protein Kinase (MAPK) pathways. The Cell Integrity Pathway (CIP), one of the three MAPK pathways found in the simple eukaryote fission of yeast Schizosaccharomyces pombe, shows strong homology with mammalian Extracellular signal-Regulated Kinases (ERKs). Remarkably, studies over the last few decades have gradually positioned the CIP as a multi-faceted pathway that impacts multiple functional aspects of the fission yeast life cycle during unperturbed growth and in response to stress. They include the control of mRNA-stability through RNA binding proteins, regulation of calcium homeostasis, and modulation of cell wall integrity and cytokinesis. Moreover, distinct evidence has disclosed the existence of sophisticated interplay between the CIP and other environmentally regulated pathways, including Stress-Activated MAP Kinase signaling (SAPK) and the Target of Rapamycin (TOR). In this review we present a current overview of the organization and underlying regulatory mechanisms of the CIP in S. pombe, describe its most prominent functions, and discuss possible targets of and roles for this pathway. The evolutionary conservation of CIP signaling in the dimorphic fission yeast S. japonicus will also be addressed.
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10
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Inamura SI, Tanabe T, Kawamukai M, Matsuo Y. Expression of Mug14 is regulated by the transcription factor Rst2 through the cAMP-dependent protein kinase pathway in Schizosaccharomyces pombe. Curr Genet 2021; 67:807-821. [PMID: 34086083 DOI: 10.1007/s00294-021-01194-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 05/26/2021] [Accepted: 05/28/2021] [Indexed: 01/04/2023]
Abstract
The cAMP-dependent protein kinase (Pka1) regulates many cellular events, including sexual development and glycogenesis, and response to the limitation of glucose, in Schizosaccharomyces pombe. Despite its importance in many cellular events, the targets of the cAMP/PKA pathway have not been fully investigated. Here, we demonstrate that the expression of mug14 is induced by downregulation of the cAMP/PKA pathway and limitation of glucose. This regulation is dependent on the function of Rst2, a transcription factor that regulates transition from mitosis to meiosis. The loss of the C2H2-type zinc finger domain in Rst2, termed Rst2 (C2H2∆), abolished the induction of Mug14 expression. Upon deletion of the stress starvation response element of the S. pombe (STREP: CCCCTC) sequence, which is a potential binding site of Rst2 on mug14, in the pka1∆ strain, its induction was abolished. The expression of Mug14 was significantly reduced and delayed by the limitation of glucose and also by nitrogen starvation in the rst2∆ strain. Mug14 is known to share a common function with Mde1 and Mta3 in the methionine salvage pathway, but the expression of mde1 and mta3 mRNAs was not enhanced by pka1 deletion and limitation of glucose. We conclude that the expression of Mug14 is upregulated by Rst2 under the control of the cAMP/PKA signaling pathway, which senses the limitation of glucose.
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Affiliation(s)
- Shin-Ich Inamura
- Graduate School of Natural Science and Technology, Shimane University, Matsue, 690-8504, Japan
| | - Takuma Tanabe
- Department of Life Sciences, Faculty of Life and Environmental Sciences, Shimane University, Matsue, 690-8504, Japan
| | - Makoto Kawamukai
- Graduate School of Natural Science and Technology, Shimane University, Matsue, 690-8504, Japan.,Department of Life Sciences, Faculty of Life and Environmental Sciences, Shimane University, Matsue, 690-8504, Japan.,Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, Matsue, 690-8504, Japan
| | - Yasuhiro Matsuo
- Graduate School of Natural Science and Technology, Shimane University, Matsue, 690-8504, Japan. .,Department of Life Sciences, Faculty of Life and Environmental Sciences, Shimane University, Matsue, 690-8504, Japan. .,Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, Matsue, 690-8504, Japan.
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11
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Pataki E, Simhaev L, Engel H, Cohen A, Kupiec M, Weisman R. TOR Complex 2- independent mutations in the regulatory PIF pocket of Gad8AKT1/SGK1 define separate branches of the stress response mechanisms in fission yeast. PLoS Genet 2020; 16:e1009196. [PMID: 33137119 PMCID: PMC7660925 DOI: 10.1371/journal.pgen.1009196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/12/2020] [Accepted: 10/14/2020] [Indexed: 12/12/2022] Open
Abstract
The Target of rapamycin (TOR) protein kinase forms part of TOR complex 1 (TORC1) and TOR complex 2 (TORC2), two multi-subunit protein complexes that regulate growth, proliferation, survival and developmental processes by phosphorylation and activation of AGC-family kinases. In the fission yeast, Schizosaccharomyces pombe, TORC2 and its target, the AGC kinase Gad8 (an orthologue of human AKT or SGK1) are required for viability under stress conditions and for developmental processes in response to starvation cues. In this study, we describe the isolation of gad8 mutant alleles that bypass the requirement for TORC2 and reveal a separation of function of TORC2 and Gad8 under stress conditions. In particular, osmotic and nutritional stress responses appear to form a separate branch from genotoxic stress responses downstream of TORC2-Gad8. Interestingly, TORC2-independent mutations map into the regulatory PIF pocket of Gad8, a highly conserved motif in AGC kinases that regulates substrate binding in PDK1 (phosphoinositide dependent kinase-1) and kinase activity in several AGC kinases. Gad8 activation is thought to require a two-step mechanism, in which phosphorylation by TORC2 allows further phosphorylation and activation by Ksg1 (an orthologue of PDK1). We focus on the Gad8-K263C mutation and demonstrate that it renders the Gad8 kinase activity independent of TORC2 in vitro and independent of the phosphorylation sites of TORC2 in vivo. Molecular dynamics simulations of Gad8-K263C revealed abnormal high flexibility at T387, the phosphorylation site for Ksg1, suggesting a mechanism for the TORC2-independent Gad8 activity. Significantly, the K263 residue is highly conserved in the family of AGC-kinases, which may suggest a general way of keeping their activity in check when acting downstream of TOR complexes. Protein kinases catalyze the transfer of phosphate from high-energy, phosphate-donating molecules, such as ATP, to their substrates. This process is pivotal for regulation of almost any aspect of cellular biology. Many human diseases are associated with aberrant functions of protein kinases due to mutations. Accordingly, there is a growing number of kinase inhibitors that have been approved for clinical use. A better understanding of how protein kinases become active and how their activity is relayed to regulate their cellular functions is much needed for rational design of kinase inhibitors and for their optimal use in the clinic. The AGC-family of protein kinases play key roles in regulating cellular growth, proliferation and survival. In human cells, as well as in the fission yeast, our cellular model system, a subgroup of the AGC kinases is activated by the TOR protein kinases. Here we report the isolation of mutations in the AGC kinase Gad8 (AKT or SGK1 in human) that bypass the requirement for activation by TOR. Analyses of how these mutations affect cellular growth revealed separate branches of stress response mechanisms downstream of Gad8, while computer simulation methods suggested a molecular mechanism that keeps the activity of Gad8 in check.
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Affiliation(s)
- Emese Pataki
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Luba Simhaev
- Blavatnik Center for Drug Discovery, Tel Aviv University, Tel Aviv, Israel
| | - Hamutal Engel
- Blavatnik Center for Drug Discovery, Tel Aviv University, Tel Aviv, Israel
| | - Adiel Cohen
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine & Cancer Research, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
| | - Ronit Weisman
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
- * E-mail:
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12
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Athanasopoulos A, André B, Sophianopoulou V, Gournas C. Fungal plasma membrane domains. FEMS Microbiol Rev 2020; 43:642-673. [PMID: 31504467 DOI: 10.1093/femsre/fuz022] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/25/2019] [Indexed: 12/11/2022] Open
Abstract
The plasma membrane (PM) performs a plethora of physiological processes, the coordination of which requires spatial and temporal organization into specialized domains of different sizes, stability, protein/lipid composition and overall architecture. Compartmentalization of the PM has been particularly well studied in the yeast Saccharomyces cerevisiae, where five non-overlapping domains have been described: The Membrane Compartments containing the arginine permease Can1 (MCC), the H+-ATPase Pma1 (MCP), the TORC2 kinase (MCT), the sterol transporters Ltc3/4 (MCL), and the cell wall stress mechanosensor Wsc1 (MCW). Additional cortical foci at the fungal PM are the sites where clathrin-dependent endocytosis occurs, the sites where the external pH sensing complex PAL/Rim localizes, and sterol-rich domains found in apically grown regions of fungal membranes. In this review, we summarize knowledge from several fungal species regarding the organization of the lateral PM segregation. We discuss the mechanisms of formation of these domains, and the mechanisms of partitioning of proteins there. Finally, we discuss the physiological roles of the best-known membrane compartments, including the regulation of membrane and cell wall homeostasis, apical growth of fungal cells and the newly emerging role of MCCs as starvation-protective membrane domains.
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Affiliation(s)
- Alexandros Athanasopoulos
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Bruno André
- Molecular Physiology of the Cell laboratory, Université Libre de Bruxelles (ULB), Institut de Biologie et de Médecine Moléculaires, rue des Pr Jeener et Brachet 12, 6041, Gosselies, Belgium
| | - Vicky Sophianopoulou
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Christos Gournas
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
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13
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Laribee RN, Weisman R. Nuclear Functions of TOR: Impact on Transcription and the Epigenome. Genes (Basel) 2020; 11:E641. [PMID: 32532005 PMCID: PMC7349558 DOI: 10.3390/genes11060641] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/04/2020] [Accepted: 06/09/2020] [Indexed: 12/15/2022] Open
Abstract
The target of rapamycin (TOR) protein kinase is at the core of growth factor- and nutrient-dependent signaling pathways that are well-known for their regulation of metabolism, growth, and proliferation. However, TOR is also involved in the regulation of gene expression, genomic and epigenomic stability. TOR affects nuclear functions indirectly through its activity in the cytoplasm, but also directly through active nuclear TOR pools. The mechanisms by which TOR regulates its nuclear functions are less well-understood compared with its cytoplasmic activities. TOR is an important pharmacological target for several diseases, including cancer, metabolic and neurological disorders. Thus, studies of the nuclear functions of TOR are important for our understanding of basic biological processes, as well as for clinical implications.
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Affiliation(s)
- R. Nicholas Laribee
- Department of Pathology and Laboratory Medicine, College of Medicine and Center for Cancer Research, University of Tennessee Health Science Center, 19 South Manassas, Cancer Research Building Rm 318, Memphis, TN 38163, USA
| | - Ronit Weisman
- Department of Natural and Life Sciences, The Open University of Israel, University Road 1, Ra’anana 4353701, Israel
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14
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Morigasaki S, Chin LC, Hatano T, Emori M, Iwamoto M, Tatebe H, Shiozaki K. Modulation of TOR complex 2 signaling by the stress-activated MAPK pathway in fission yeast. J Cell Sci 2019; 132:jcs.236133. [PMID: 31477575 DOI: 10.1242/jcs.236133] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 08/28/2019] [Indexed: 01/27/2023] Open
Abstract
Sin1 is a substrate-binding subunit of target of rapamycin complex 2 (TORC2), an evolutionarily conserved protein kinase complex. In fission yeast, Sin1 has also been identified as a protein that interacts with Spc1 (also known as Sty1) in the stress-activated protein kinase (SAPK) pathway. Therefore, this study examined the relationship between TORC2 and Spc1 signaling. We found that the common docking (CD) domain of Spc1 interacts with a cluster of basic amino acid residues in Sin1. Although diminished TORC2 activity in the absence of the functional Spc1 cascade suggests positive regulation of TORC2 by Spc1, such regulation appears to be independent of the Sin1-Spc1 interaction. Hyperosmotic stress transiently inhibits TORC2, and its swift recovery is dependent on Spc1, the transcription factor Atf1, and the glycelrol-3-phosphate dehydrogenase Gpd1, whose expression is induced upon osmostress by the Spc1-Atf1 pathway. Thus, cellular adaptation to osmostress seems important for TORC2 reactivation, though Spc1 and Atf1 contribute to TORC2 activation also in the absence of osmostress. These results indicate coordinated actions of the SAPK and TORC2 pathways, both of which are essential for fission yeast cells to survive environmental stress.
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Affiliation(s)
- Susumu Morigasaki
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.,Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa 904-0495, Japan
| | - Lit Chein Chin
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - Tomoyuki Hatano
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - Midori Emori
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - Mika Iwamoto
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - Hisashi Tatebe
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - 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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15
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Baker K, Gyamfi IA, Mashanov GI, Molloy JE, Geeves MA, Mulvihill DP. TORC2-Gad8-dependent myosin phosphorylation modulates regulation by calcium. eLife 2019; 8:e51150. [PMID: 31566560 PMCID: PMC6802964 DOI: 10.7554/elife.51150] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 09/26/2019] [Indexed: 01/22/2023] Open
Abstract
Cells respond to changes in their environment through signaling networks that modulate cytoskeleton and membrane organization to coordinate cell-cycle progression, polarized cell growth and multicellular development. Here, we define a novel regulatory mechanism by which the motor activity and function of the fission yeast type one myosin, Myo1, is modulated by TORC2-signalling-dependent phosphorylation. Phosphorylation of the conserved serine at position 742 (S742) within the neck region changes both the conformation of the neck region and the interactions between Myo1 and its associating calmodulin light chains. S742 phosphorylation thereby couples the calcium and TOR signaling networks that are involved in the modulation of myosin-1 dynamics to co-ordinate actin polymerization and membrane reorganization at sites of endocytosis and polarised cell growth in response to environmental and cell-cycle cues.
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Affiliation(s)
- Karen Baker
- School of BiosciencesUniversity of KentCanterburyUnited Kingdom
| | - Irene A Gyamfi
- School of BiosciencesUniversity of KentCanterburyUnited Kingdom
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16
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Oya E, Durand-Dubief M, Cohen A, Maksimov V, Schurra C, Nakayama JI, Weisman R, Arcangioli B, Ekwall K. Leo1 is essential for the dynamic regulation of heterochromatin and gene expression during cellular quiescence. Epigenetics Chromatin 2019; 12:45. [PMID: 31315658 PMCID: PMC6636030 DOI: 10.1186/s13072-019-0292-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 07/10/2019] [Indexed: 11/16/2022] Open
Abstract
Background Cellular quiescence is a reversible differentiation state during which cells modify their gene expression program to inhibit metabolic functions and adapt to a new cellular environment. The epigenetic changes accompanying these alterations are not well understood. We used fission yeast cells as a model to study the regulation of quiescence. When these cells are starved for nitrogen, the cell cycle is arrested in G1, and the cells enter quiescence (G0). A gene regulatory program is initiated, including downregulation of thousands of genes—for example, those related to cell proliferation—and upregulation of specific genes—for example, autophagy genes—needed to adapt to the physiological challenge. These changes in gene expression are accompanied by a marked alteration of nuclear organization and chromatin structure. Results Here, we investigated the role of Leo1, a subunit of the conserved RNA polymerase-associated factor 1 (Paf1) complex, in the quiescence process using fission yeast as the model organism. Heterochromatic regions became very dynamic in fission yeast in G0 during nitrogen starvation. The reduction of heterochromatin in early G0 was correlated with reduced target of rapamycin complex 2 (TORC2) signaling. We demonstrated that cells lacking Leo1 show reduced survival in G0. In these cells, heterochromatic regions, including subtelomeres, were stabilized, and the expression of many genes, including membrane transport genes, was abrogated. TOR inhibition mimics the effect of nitrogen starvation, leading to the expression of subtelomeric genes, and this effect was suppressed by genetic deletion of leo1. Conclusions We identified a protein, Leo1, necessary for survival during quiescence. Leo1 is part of a conserved protein complex, Paf1C, linked to RNA polymerase II. We showed that Leo1, acting downstream of TOR, is crucial for the dynamic reorganization of chromosomes and the regulation of gene expression during cellular quiescence. Genes encoding membrane transporters are not expressed in quiescent leo1 mutant cells, and cells die after 2 weeks of nitrogen starvation. Taken together, our results suggest that Leo1 is essential for the dynamic regulation of heterochromatin and gene expression during cellular quiescence. Electronic supplementary material The online version of this article (10.1186/s13072-019-0292-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Eriko Oya
- Department of Biosciences and Nutrition, Karolinska Institutet, NEO Building, 141 83, Huddinge, Sweden
| | - Mickaël Durand-Dubief
- Department of Biosciences and Nutrition, Karolinska Institutet, NEO Building, 141 83, Huddinge, Sweden
| | - Adiel Cohen
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Vladimir Maksimov
- Department of Biosciences and Nutrition, Karolinska Institutet, NEO Building, 141 83, Huddinge, Sweden
| | - Catherine Schurra
- Unite Dynamique du Génome, Département Génomes et Génétique, Pasteur Institute, Paris, France
| | - Jun-Ichi Nakayama
- Division of Chromatin Regulation, National Institute for Basic Biology, Okazaki, Japan
| | - Ronit Weisman
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Benoit Arcangioli
- Unite Dynamique du Génome, Département Génomes et Génétique, Pasteur Institute, Paris, France
| | - Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institutet, NEO Building, 141 83, Huddinge, Sweden.
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17
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Leskoske KL, Roelants FM, Emmerstorfer-Augustin A, Augustin CM, Si EP, Hill JM, Thorner J. Phosphorylation by the stress-activated MAPK Slt2 down-regulates the yeast TOR complex 2. Genes Dev 2018; 32:1576-1590. [PMID: 30478248 PMCID: PMC6295167 DOI: 10.1101/gad.318709.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 10/10/2018] [Indexed: 12/13/2022]
Abstract
Here, Leskoske et al. studied how TORC2 activity is modulated in response to changes in the status of the cell envelope. They demonstrate that TORC2 subunit Avo2 is a direct target of Slt2, the MAPK of the cell wall integrity pathway, and their findings provide new insights into TORC2 function and regulation. Saccharomyces cerevisiae target of rapamycin (TOR) complex 2 (TORC2) is an essential regulator of plasma membrane lipid and protein homeostasis. How TORC2 activity is modulated in response to changes in the status of the cell envelope is unclear. Here we document that TORC2 subunit Avo2 is a direct target of Slt2, the mitogen-activated protein kinase (MAPK) of the cell wall integrity pathway. Activation of Slt2 by overexpression of a constitutively active allele of an upstream Slt2 activator (Pkc1) or by auxin-induced degradation of a negative Slt2 regulator (Sln1) caused hyperphosphorylation of Avo2 at its MAPK phosphoacceptor sites in a Slt2-dependent manner and diminished TORC2-mediated phosphorylation of its major downstream effector, protein kinase Ypk1. Deletion of Avo2 or expression of a phosphomimetic Avo2 allele rendered cells sensitive to two stresses (myriocin treatment and elevated exogenous acetic acid) that the cell requires Ypk1 activation by TORC2 to survive. Thus, Avo2 is necessary for optimal TORC2 activity, and Slt2-mediated phosphorylation of Avo2 down-regulates TORC2 signaling. Compared with wild-type Avo2, phosphomimetic Avo2 shows significant displacement from the plasma membrane, suggesting that Slt2 inhibits TORC2 by promoting Avo2 dissociation. Our findings are the first demonstration that TORC2 function is regulated by MAPK-mediated phosphorylation.
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Affiliation(s)
- Kristin L Leskoske
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Françoise M Roelants
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Anita Emmerstorfer-Augustin
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Christoph M Augustin
- Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720, USA
| | - Edward P Si
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Jennifer M Hill
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
| | - Jeremy Thorner
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
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18
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Nakase Y, Matsumoto T. The RHEB-mTOR axis regulates expression of Tf2 transposons in fission yeast. J Cell Sci 2018; 131:jcs.221457. [PMID: 30301783 DOI: 10.1242/jcs.221457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/01/2018] [Indexed: 01/12/2023] Open
Abstract
The human TSC2 gene, mutations in which predispose individuals to the disease tuberous sclerosis complex (TSC), encodes a GTPase-activating protein for the GTPase RHEB. Loss of TSC2 results in constitutive activation of RHEB and its target mammalian target of rapamycin (mTOR). We have previously reported that fission yeast (Schizosaccharomyces pombe) Tf2 retrotransposons (hereafter Tf2s) are abnormally induced upon nitrogen starvation in cells lacking the tsc2+ gene (Δtsc2), a homolog of the human TSC2 gene, and in cells with a dominant-active mutation in the fission yeast RHEB GTPase (rhb1-DA4). We report here that induction of Tf2s in these mutants is suppressed upon overexpression of the cgs2+ gene, which encodes a cAMP-specific phosphodiesterase, or upon deletion of components in the glucose/cAMP signaling pathway, namely Cyr1, Pka1, Tor1 and the stress-activated transcription factor Atf1. The results suggest that the glucose/cAMP signaling pathway is downregulated when cells are starved for nitrogen. We also show that Tf2 proteins are degraded via autophagy, which is under control of Tor2, a homolog of human mTOR. It appears that failure in the two processes, downregulation of the glucose/cAMP signaling pathway and induction of autophagy, allows abnormal induction of Tf2s upon nitrogen starvation in Δtsc2 and rhb1-DA4 cells.
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Affiliation(s)
- Yukiko Nakase
- Radiation Biology Center, Kyoto University, Yoshida-Konoe cho, Sakyo ku, Kyoto 606-8501, Japan
| | - Tomohiro Matsumoto
- Radiation Biology Center, Kyoto University, Yoshida-Konoe cho, Sakyo ku, Kyoto 606-8501, Japan .,Graduate School of Biostudies, Kyoto University, Yoshida-Konoe cho, Sakyo ku, Kyoto 606-8501, Japan
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19
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PKA-site phosphorylation of importin13 regulates its subcellular localization and nuclear transport function. Biochem J 2018; 475:2699-2712. [PMID: 30045875 DOI: 10.1042/bcj20180082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 07/12/2018] [Accepted: 07/16/2018] [Indexed: 01/25/2023]
Abstract
Importin 13 (IPO13) is a key member of the importin β superfamily, which can transport cargoes both into and out of the nucleus to contribute to a variety of important cellular processes. IPO13 is known to undergo phosphorylation, but the impact of this on function has not been investigated. Here, we show for the first time that IPO13 is phosphorylated by cAMP-dependent protein kinase A specifically at serine 193. Results from fluorescence recovery after photobleaching and fluorescence loss in photobleaching approaches establish that negative charge at serine 193 through phosphorylation or point mutation both reduces IPO13 nuclear import and increases its nuclear export. Importantly, phosphorylation also appears to enhance cargo interaction on the part of IPO13, with significant impact on localization, as shown for the Pax6 homeobox-containing transcription partner. This is the first report that IPO13 can be phosphorylated at Ser193 and that this modification regulates IPO13 subcellular localization and nucleocytoplasmic transport function, with important implications for IPO13's role in development and other processes.
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20
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Cohen A, Habib A, Laor D, Yadav S, Kupiec M, Weisman R. TOR complex 2 in fission yeast is required for chromatin-mediated gene silencing and assembly of heterochromatic domains at subtelomeres. J Biol Chem 2018; 293:8138-8150. [PMID: 29632066 DOI: 10.1074/jbc.ra118.002270] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/14/2018] [Indexed: 12/21/2022] Open
Abstract
The conserved serine/threonine protein kinase target of rapamycin (TOR) is a major regulator of eukaryotic cellular and organismal growth and a valuable target for drug therapy. TOR forms the core of two evolutionary conserved complexes, TOR complex 1 (TORC1) and TORC2. In the fission yeast Schizosaccharomyces pombe, TORC2 responds to glucose levels and, by activating the protein kinase Gad8 (an orthologue of human AKT), is required for well-regulated cell cycle progression, starvation responses, and cell survival. Here, we report that TORC2-Gad8 is also required for gene silencing and the formation of heterochromatin at the S. pombe mating-type locus and at subtelomeric regions. Deletion of TORC2-Gad8 resulted in loss of the heterochromatic modification of histone 3 lysine 9 dimethylation (H3K9me2) and an increase in euchromatic modifications, including histone 3 lysine 4 trimethylation (H3K4me3) and histone 4 lysine 16 acetylation (H4K16Ac). Accumulation of RNA polymerase II (Pol II) at subtelomeric genes in TORC2-Gad8 mutant cells indicated a defect in silencing at the transcriptional level. Moreover, a concurrent decrease in histone 4 lysine 20 dimethylation (H4K20me2) suggested elevated histone turnover. Loss of gene silencing in cells lacking TORC2-Gad8 is partially suppressed by loss of the anti-silencer Epe1 and fully suppressed by loss of the Pol II-associated Paf1 complex, two chromatin regulators that have been implicated in heterochromatin stability and spreading. Taken together, our findings suggest that TORC2-Gad8 signaling contributes to epigenetic stability at subtelomeric regions and the mating-type locus in S. pombe.
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Affiliation(s)
- Adiel Cohen
- Department of Natural and Life Sciences, Open University of Israel, University Road 1, 4353701 Ranana, Israel
| | - Aline Habib
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69977801, Tel Aviv, Israel
| | - Dana Laor
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69977801, Tel Aviv, Israel
| | - Sudhanshu Yadav
- Department of Natural and Life Sciences, Open University of Israel, University Road 1, 4353701 Ranana, Israel
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69977801, Tel Aviv, Israel
| | - Ronit Weisman
- Department of Natural and Life Sciences, Open University of Israel, University Road 1, 4353701 Ranana, Israel.
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21
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Lucena R, Alcaide-Gavilán M, Schubert K, He M, Domnauer MG, Marquer C, Klose C, Surma MA, Kellogg DR. Cell Size and Growth Rate Are Modulated by TORC2-Dependent Signals. Curr Biol 2017; 28:196-210.e4. [PMID: 29290562 DOI: 10.1016/j.cub.2017.11.069] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 10/19/2017] [Accepted: 11/30/2017] [Indexed: 02/05/2023]
Abstract
The size of all cells, from bacteria to vertebrates, is proportional to the growth rate set by nutrient availability, but the underlying mechanisms are unknown. Here, we show that nutrients modulate cell size and growth rate via the TORC2 signaling network in budding yeast. An important function of the TORC2 network is to modulate synthesis of ceramide lipids, which play roles in signaling. TORC2-dependent control of ceramide signaling strongly influences both cell size and growth rate. Thus, cells that cannot make ceramides fail to modulate their growth rate or size in response to changes in nutrients. PP2A associated with the Rts1 regulatory subunit (PP2ARts1) is embedded in a feedback loop that controls TORC2 signaling and helps set the level of TORC2 signaling to match nutrient availability. Together, the data suggest a model in which growth rate and cell size are mechanistically linked by ceramide-dependent signals arising from the TORC2 network.
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Affiliation(s)
- Rafael Lucena
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Maria Alcaide-Gavilán
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Katherine Schubert
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Maybo He
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Matthew G Domnauer
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Catherine Marquer
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA
| | | | | | - Douglas R Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
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22
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Abstract
All organisms can respond to the availability of nutrients by regulating their metabolism, growth, and cell division. Central to the regulation of growth in response to nutrient availability is the target of rapamycin (TOR) signaling that is composed of two structurally distinct complexes: TOR complex 1 (TORC1) and TOR complex 2 (TORC2). The TOR genes were first identified in yeast as target of rapamycin, a natural product of a soil bacterium, which proved beneficial as an immunosuppressive and anticancer drug and is currently being tested for a handful of other pathological conditions including diabetes, neurodegeneration, and age-related diseases. Studies of the TOR pathway unraveled a complex growth-regulating network. TOR regulates nutrient uptake, transcription, protein synthesis and degradation, as well as metabolic pathways, in a coordinated manner that ensures that cells grow or cease growth in response to nutrient availability. The identification of specific signals and mechanisms that stimulate TOR signaling is an active and exciting field of research that has already identified nitrogen and amino acids as key regulators of TORC1 activity. The signals, as well as the cellular functions of TORC2, are far less well understood. Additional open questions in the field concern the relationships between TORC1 and TORC2, as well as the links with other nutrient-responsive pathways. Here I review the main features of TORC1 and TORC2, with a particular focus on yeasts as model organisms.
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23
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Martínez-Soto D, Ruiz-Herrera J. Functional analysis of the MAPK pathways in fungi. Rev Iberoam Micol 2017; 34:192-202. [PMID: 28732778 DOI: 10.1016/j.riam.2017.02.006] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 01/27/2017] [Accepted: 02/17/2017] [Indexed: 01/19/2023] Open
Abstract
The Mitogen-Activated Protein Kinase (MAPK) signaling pathways constitute one of the most important and evolutionarily conserved mechanisms for the perception of extracellular information in all the eukaryotic organisms. The MAPK pathways are involved in the transfer to the cell of the information perceived from extracellular stimuli, with the final outcome of activation of different transcription factors that regulate gene expression in response to them. In all species of fungi, the MAPK pathways have important roles in their physiology and development; e.g. cell cycle control, mating, morphogenesis, response to different stresses, resistance to UV radiation and to temperature changes, cell wall assembly and integrity, degradation of cellular organelles, virulence, cell-cell signaling, fungus-plant interaction, and response to damage-associated molecular patterns (DAMPs). Considering the importance of the phylogenetically conserved MAPK pathways in fungi, an updated review of the knowledge on them is discussed in this article. This information reveals their importance, their distribution in fungal species evolutionarily distant and with different lifestyles, their organization and function, and the interactions occurring between different MAPK pathways, and with other signaling pathways, for the regulation of the most complex cellular processes.
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Affiliation(s)
- Domingo Martínez-Soto
- Departamento de Ingeniería Genética, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Gto., Mexico
| | - José Ruiz-Herrera
- Departamento de Ingeniería Genética, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Gto., Mexico.
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24
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Martín R, Portantier M, Chica N, Nyquist-Andersen M, Mata J, Lopez-Aviles S. A PP2A-B55-Mediated Crosstalk between TORC1 and TORC2 Regulates the Differentiation Response in Fission Yeast. Curr Biol 2016; 27:175-188. [PMID: 28041796 PMCID: PMC5266790 DOI: 10.1016/j.cub.2016.11.037] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 09/20/2016] [Accepted: 11/14/2016] [Indexed: 12/20/2022]
Abstract
Extracellular cues regulate cell fate, and this is mainly achieved through the engagement of specific transcriptional programs. The TORC1 and TORC2 complexes mediate the integration of nutritional cues to cellular behavior, but their interplay is poorly understood. Here, we use fission yeast to investigate how phosphatase activity participates in this interplay during the switch from proliferation to sexual differentiation. We find that loss of PP2A-B55Pab1 enhances the expression of differentiation-specific genes and leads to premature conjugation. pab1 deletion brings about a transcriptional profile similar to TORC1 inactivation, and deletion of pab1 overcomes the repression of differentiation genes in cells overexpressing TORC1. Importantly, we show that this effect is mediated by an increased TORC2-AKT (Gad8) signaling. Under nutrient-rich conditions, PP2A-B55Pab1 dephosphorylates Gad8 Ser546, repressing its activity. Conversely, TORC1 inactivation upon starvation leads to the inactivation of PP2A-B55Pab1 through the Greatwall-Endosulfin pathway. This results in the activation of Gad8 and the commitment to differentiation. Thus, PP2A-B55Pab1 enables a crosstalk between the two TOR complexes that controls cell-fate decisions in response to nutrient availability. PP2A-B55Pab1 regulates the differentiation response of fission yeast cells PP2A-B55Pab1 enables a crosstalk between TORC1 and TORC2 TORC1 favors PP2A-B55Pab1 activity to prevent the hyperphosphorylation of Gad8 TORC1 inactivation leads to PP2A-B55Pab1 inhibition, activation of Gad8, and differentiation
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Affiliation(s)
- Ruth Martín
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalléen 21, Oslo 0349, Norway
| | - Marina Portantier
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalléen 21, Oslo 0349, Norway
| | - Nathalia Chica
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalléen 21, Oslo 0349, Norway
| | - Mari Nyquist-Andersen
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalléen 21, Oslo 0349, Norway
| | - Juan Mata
- Department of Biochemistry, University of Cambridge, Building O, Downing Site, Cambridge CB2 1QW, UK
| | - Sandra Lopez-Aviles
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalléen 21, Oslo 0349, Norway.
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25
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Du W, Forte GM, Smith D, Petersen J. Phosphorylation of the amino-terminus of the AGC kinase Gad8 prevents its interaction with TORC2. Open Biol 2016; 6:rsob.150189. [PMID: 26935949 PMCID: PMC4821236 DOI: 10.1098/rsob.150189] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cell proliferation, metabolism, migration and survival are coordinated through the tight control of two target of rapamycin (TOR) kinase complexes: TORC1 and TORC2. Here, we show that a novel phosphorylation of fission yeast Gad8 (AGC kinase) on the evolutionarily conserved threonine 6 (Thr6) prevents the physical association between Gad8 and TORC2. Accordingly, this block to protein interactions by Gad8 Thr6 phosphorylation decreases TORC2-controlled activation of Gad8. Likewise, phosphorylation of Gad8 Thr6, possibly by PKC, prevents the association of Gad8 with TORC2 thereby increasing TORC2 activity, because it reduces Gad8-mediated feedback inhibition of TORC2. Consistently, the introduction of a Gad8 T6D mutant, that mimics phosphorylation, increased TORC2 activity. Increased PKCPck2 expression prevented Gad8–TORC2 binding and so reduced the TORC2-mediated phosphorylation of Gad8 serine 546 that activates Gad8. Interestingly, independent of the Ser546 phosphorylation status, Gad8 Thr6 phosphorylation is important for remodelling the actin cytoskeleton and survival upon potassium ion and heat stresses. In contrast, Ser546 phosphorylation is required for the control of G1 arrest, mating, cell length at division and vascular size. Finally, these findings reveal a novel mode of TORC2 activation that is essential for cell survival following stress.
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Affiliation(s)
- Wei Du
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Gabriella M Forte
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Duncan Smith
- Biological Mass Spectrometry, Cancer Research UK Manchester Institute, The Paterson Building, Wilmslow Road, Manchester M20 4BX, UK
| | - Janni Petersen
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK Flinders Centre for Innovation in Cancer, School of Medicine, Flinders University, Adelaide, South Australia 5001, Australia South Australia Health and Medical Research Institute, North Terrace, PO Box 11060, Adelaide, South Australia 5000, Australia
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26
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Multiple crosstalk between TOR and the cell integrity MAPK signaling pathway in fission yeast. Sci Rep 2016; 6:37515. [PMID: 27876895 PMCID: PMC5120329 DOI: 10.1038/srep37515] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 10/28/2016] [Indexed: 02/07/2023] Open
Abstract
In eukaryotic cells, the highly conserved Target of Rapamycin (TOR) and the Mitogen Activated Protein Kinase (MAPK) signaling pathways elicit adaptive responses to extra- and intracellular conditions by regulating essential cellular functions. However, the nature of the functional relationships between both pathways is not fully understood. In the fission yeast Schizosaccharomyces pombe the cell integrity MAPK pathway (CIP) regulates morphogenesis, cell wall structure and ionic homeostasis. We show that the Rab GTPase Ryh1, a TORC2 complex activator, cross-activates the CIP and its core member, the MAPK Pmk1, by two distinct mechanisms. The first one involves TORC2 and its downstream effector, Akt ortholog Gad8, which together with TORC1 target Psk1 increase protein levels of the PKC ortholog Pck2 during cell wall stress or glucose starvation. Also, Ryh1 activates Pmk1 in a TORC2-independent fashion by prompting plasma membrane trafficking and stabilization of upstream activators of the MAPK cascade, including PDK ortholog Ksg1 or Rho1 GEF Rgf1. Besides, stress-activated Pmk1 cross-inhibits Ryh1 signaling by decreasing the GTPase activation cycle, and this ensures cell growth during alterations in phosphoinositide metabolism. Our results reveal a highly intricate cross-regulatory relationship between both pathways that warrants adequate cell adaptation and survival in response to environmental changes.
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27
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Cohen A, Kupiec M, Weisman R. Gad8 Protein Is Found in the Nucleus Where It Interacts with the MluI Cell Cycle Box-binding Factor (MBF) Transcriptional Complex to Regulate the Response to DNA Replication Stress. J Biol Chem 2016; 291:9371-81. [PMID: 26912660 DOI: 10.1074/jbc.m115.705251] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Indexed: 12/31/2022] Open
Abstract
The target of rapamycin (TOR) kinase is found at the core of two evolutionarily conserved complexes known as TOR complexes 1 and 2 (TORC1 and TORC2). In fission yeast, TORC2 is dispensable for proliferation under optimal growth conditions but is required for starvation and stress responses. We have previously reported that loss of function of TORC2 renders cells highly sensitive to DNA replication stress; however, the mechanism underlying this sensitivity is unknown. TORC2 has one known direct substrate, the kinase Gad8, which is related to AKT in human cells. Here we show that both TORC2 and its substrate Gad8 are found in the nucleus and are bound to the chromatin. We also demonstrate that Gad8 physically interacts with the MluI cell cycle box-binding factor (MBF) transcription complex that regulates the G1/S progression and the response to DNA stress. In mutant cells lacking TORC2 or Gad8, the binding of the MBF complex to its cognate promoters is compromised, and the induction of MBF target genes in response to DNA replication stress is reduced. Consistently, the protein levels of Cdt2 and Cig2, two MBF target genes, are reduced in the absence of TORC2-Gad8 signaling. Taken together, our findings highlight critical functions of TORC2 in the nucleus and suggest a role in surviving DNA replication stress via transcriptional regulation of MBF target genes.
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Affiliation(s)
- Adiel Cohen
- From the Department of Natural and Life Sciences, The Open University of Israel, University Road 1, 4353701 Raanana, Israel and
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Ronit Weisman
- From the Department of Natural and Life Sciences, The Open University of Israel, University Road 1, 4353701 Raanana, Israel and
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28
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Masuda F, Ishii M, Mori A, Uehara L, Yanagida M, Takeda K, Saitoh S. Glucose restriction induces transient G2 cell cycle arrest extending cellular chronological lifespan. Sci Rep 2016; 6:19629. [PMID: 26804466 PMCID: PMC4726166 DOI: 10.1038/srep19629] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 12/16/2015] [Indexed: 01/15/2023] Open
Abstract
While glucose is the fundamental source of energy in most eukaryotes, it is not always abundantly available in natural environments, including within the human body. Eukaryotic cells are therefore thought to possess adaptive mechanisms to survive glucose-limited conditions, which remain unclear. Here, we report a novel mechanism regulating cell cycle progression in response to abrupt changes in extracellular glucose concentration. Upon reduction of glucose in the medium, wild-type fission yeast cells undergo transient arrest specifically at G2 phase. This cell cycle arrest is dependent on the Wee1 tyrosine kinase inhibiting the key cell cycle regulator, CDK1/Cdc2. Mutant cells lacking Wee1 are not arrested at G2 upon glucose limitation and lose viability faster than the wild-type cells under glucose-depleted quiescent conditions, suggesting that this cell cycle arrest is required for extension of chronological lifespan. Our findings indicate the presence of a novel cell cycle checkpoint monitoring glucose availability, which may be a good molecular target for cancer therapy.
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Affiliation(s)
- Fumie Masuda
- Institute of Life Science, Kurume University, Hyakunen-Khoen 1-1, Kurume, Fukuoka 839-0864, Japan
| | - Mahiro Ishii
- Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Ayaka Mori
- Okinawa Institute of Science and Technology Graduate School, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
| | - Lisa Uehara
- Okinawa Institute of Science and Technology Graduate School, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
| | - Mitsuhiro Yanagida
- Okinawa Institute of Science and Technology Graduate School, Tancha 1919-1, Onna, Okinawa 904-0495, Japan
| | - Kojiro Takeda
- Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan.,Institute for Integrative Neurobiology, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Shigeaki Saitoh
- Institute of Life Science, Kurume University, Hyakunen-Khoen 1-1, Kurume, Fukuoka 839-0864, Japan
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29
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Hatano T, Morigasaki S, Tatebe H, Ikeda K, Shiozaki K. Fission yeast Ryh1 GTPase activates TOR Complex 2 in response to glucose. Cell Cycle 2015; 14:848-56. [PMID: 25590601 PMCID: PMC4612450 DOI: 10.1080/15384101.2014.1000215] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The Target Of Rapamycin (TOR) is an evolutionarily conserved protein kinase that forms 2 distinct protein complexes referred to as TOR complex 1 (TORC1) and 2 (TORC2). Recent extensive studies have demonstrated that TORC1 is under the control of the small GTPases Rheb and Rag that funnel multiple input signals including those derived from nutritional sources; however, information is scarce as to the regulation of TORC2. A previous study using the model system provided by the fission yeast Schizosaccharomyces pombe identified Ryh1, a Rab-family GTPase, as an activator of TORC2. Here, we show that the nucleotide-binding state of Ryh1 is regulated in response to glucose, mediating this major nutrient signal to TORC2. In glucose-rich growth media, the GTP-bound form of Ryh1 induces TORC2-dependent phosphorylation of Gad8, a downstream target of TORC2 in fission yeast. Upon glucose deprivation, Ryh1 becomes inactive, which turns off the TORC2-Gad8 pathway. During glucose starvation, however, Gad8 phosphorylation by TORC2 gradually recovers independently of Ryh1, implying an additional TORC2 activator that is regulated negatively by glucose. The paired positive and negative regulatory mechanisms may allow fine-tuning of the TORC2-Gad8 pathway, which is essential for growth under glucose-limited environment.
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Affiliation(s)
- Tomoyuki Hatano
- a Graduate School of Biological Sciences , Nara Institute of Science and Technology , Ikoma , Nara , Japan
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30
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Bond ME, Brown R, Rallis C, Bähler J, Mole SE. A central role for TOR signalling in a yeast model for juvenile CLN3 disease. MICROBIAL CELL 2015; 2:466-480. [PMID: 28357272 PMCID: PMC5354605 DOI: 10.15698/mic2015.12.241] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Yeasts provide an excellent genetically tractable eukaryotic system for investigating the function of genes in their biological context, and are especially relevant for those conserved genes that cause disease. We study the role of btn1, the orthologue of a human gene that underlies an early onset neurodegenerative disease (juvenile CLN3 disease, neuronal ceroid lipofuscinosis (NCLs) or Batten disease) in the fission yeast Schizosaccharomyces pombe. A global screen for genetic interactions with btn1 highlighted a conserved key signalling hub in which multiple components functionally relate to this conserved disease gene. This signalling hub includes two major mitogen-activated protein kinase (MAPK) cascades, and centers on the Tor kinase complexes TORC1 and TORC2. We confirmed that yeast cells modelling CLN3 disease exhibit features consistent with dysfunction in the TORC pathways, and showed that modulating TORC function leads to a comprehensive rescue of defects in this yeast disease model. The same pathways may be novel targets in the development of therapies for the NCLs and related diseases.
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Affiliation(s)
- Michael E Bond
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Rachel Brown
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Charalampos Rallis
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK. ; Institute of Healthy Ageing, University College London, London WC1E 6BT, UK
| | - Jürg Bähler
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK. ; Institute of Healthy Ageing, University College London, London WC1E 6BT, UK
| | - Sara E Mole
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK. ; UCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK. ; Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
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31
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Asakawa H, Yamamoto TG, Hiraoka Y. Fission yeast meets a legend in Kobe: report of the Eighth International Fission Yeast Meeting. Genes Cells 2015; 20:967-71. [PMID: 26477989 DOI: 10.1111/gtc.12307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 09/14/2015] [Indexed: 11/28/2022]
Abstract
The Eighth International Fission Yeast Meeting, which was held at Ikuta Shrine Hall in Kobe, Japan, from 21 to 26 June 2015, was attended by 327 fission yeast researchers from 25 countries (190 overseas and 137 domestic participants). At this meeting, 124 talks were held and 145 posters were presented. In addition, newly developed database tools were introduced to the community during a workshop. Researchers shared cutting-edge knowledge across broad fields of study, ranging from molecules to evolution, derived from the superior model organism commonly used within the fission yeast community. Intensive discussions and constructive suggestions generated in this meeting will surely advance the understanding of complex biological systems in fission yeast, extending to general eukaryotes.
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Affiliation(s)
- Haruhiko Asakawa
- Graduate School of Frontier Biosciences, Osaka University, Suita, 565-0871, Japan
| | - Takaharu G Yamamoto
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe, 651-2492, Japan
| | - Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, Suita, 565-0871, Japan.,Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe, 651-2492, Japan
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32
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TORC1 Regulates Developmental Responses to Nitrogen Stress via Regulation of the GATA Transcription Factor Gaf1. mBio 2015; 6:e00959. [PMID: 26152587 PMCID: PMC4488950 DOI: 10.1128/mbio.00959-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The TOR (target of rapamycin [sirolimus]) is a universally conserved kinase that couples nutrient availability to cell growth. TOR complex 1 (TORC1) in Schizosaccharomyces pombe positively regulates growth in response to nitrogen availability while suppressing cellular responses to nitrogen stress. Here we report the identification of the GATA transcription factor Gaf1 as a positive regulator of the nitrogen stress-induced gene isp7+, via three canonical GATA motifs. We show that under nitrogen-rich conditions, TORC1 positively regulates the phosphorylation and cytoplasmic retention of Gaf1 via the PP2A-like phosphatase Ppe1. Under nitrogen stress conditions when TORC1 is inactivated, Gaf1 becomes dephosphorylated and enters the nucleus. Gaf1 was recently shown to negatively regulate the transcription induction of ste11+, a major regulator of sexual development. Our findings support a model of a two-faceted role of Gaf1 during nitrogen stress. Gaf1 positively regulates genes that are induced early in the response to nitrogen stress, while inhibiting later responses, such as sexual development. Taking these results together, we identify Gaf1 as a novel target for TORC1 signaling and a step-like mechanism to modulate the nitrogen stress response. TOR complex 1 (TORC1) is an evolutionary conserved protein complex that positively regulates growth and proliferation, while inhibiting starvation responses. In fission yeast, the activity of TORC1 is downregulated in response to nitrogen starvation, and cells reprogram their transcriptional profile and prepare for sexual development. We identify Gaf1, a GATA-like transcription factor that regulates transcription and sexual development in response to starvation, as a downstream target for TORC1 signaling. Under nitrogen-rich conditions, TORC1 positively regulates the phosphorylation and cytoplasmic retention of Gaf1 via the PP2A-like phosphatase Ppe1. Under nitrogen stress conditions when TORC1 is inactivated, Gaf1 becomes dephosphorylated and enters the nucleus. Budding yeast TORC1 regulates GATA transcription factors via the phosphatase Sit4, a structural homologue of Ppe1. Thus, the TORC1-GATA transcription module appears to be conserved in evolution and may also be found in higher eukaryotes.
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33
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Takeda K, Starzynski C, Mori A, Yanagida M. The critical glucose concentration for respiration-independent proliferation of fission yeast, Schizosaccharomyces pombe. Mitochondrion 2015; 22:91-5. [DOI: 10.1016/j.mito.2015.04.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/30/2015] [Accepted: 04/09/2015] [Indexed: 11/25/2022]
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34
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Howie D, Waldmann H, Cobbold S. Nutrient Sensing via mTOR in T Cells Maintains a Tolerogenic Microenvironment. Front Immunol 2014; 5:409. [PMID: 25221554 PMCID: PMC4147234 DOI: 10.3389/fimmu.2014.00409] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 08/13/2014] [Indexed: 01/01/2023] Open
Abstract
We have proposed that tolerance can be maintained through the induction, by Treg cells, of a tolerogenic microenvironment within tolerated tissues that inhibits effector cell activity but which supports the generation of further Treg cells by “infectious tolerance.” Two important components of this tolerogenic microenvironment depend on metabolism and nutrient sensing. The first is due to the up-regulation of multiple enzymes that consume essential amino acids, which are sensed in naïve T cells primarily via inhibition of the mechanistic target of rapamycin (mTOR) pathway, which in turn encourages their further differentiation into FOXP3+ Treg cells. The second mechanism is the metabolism of extracellular ATP to adenosine by the ectoenzymes CD39 and CD73. These two enzymes are constitutively co-expressed on Treg cells, but can also be induced on a wide variety of cell types by TGFβ and the adenosine generated can be shown to be a potent inhibitor of T cell proliferation. This review will focus on mechanisms of nutrient sensing in T cells, how these are integrated with TCR and cytokine signals via the mTOR pathway, and what impact this has on intracellular metabolism and subsequently the control of differentiation into different effector or regulatory T cell subsets.
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Affiliation(s)
- Duncan Howie
- Sir William Dunn School of Pathology, University of Oxford , Oxford , UK
| | - Herman Waldmann
- Sir William Dunn School of Pathology, University of Oxford , Oxford , UK
| | - Stephen Cobbold
- Sir William Dunn School of Pathology, University of Oxford , Oxford , UK
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35
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Madrid M, Jiménez R, Sánchez-Mir L, Soto T, Franco A, Vicente-Soler J, Gacto M, Pérez P, Cansado J. Multiple regulatory levels influence cell integrity control by PKC ortholog Pck2 in fission yeast. J Cell Sci 2014; 128:266-80. [DOI: 10.1242/jcs.158295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fission yeast PKC ortholog Pck2 controls cell wall synthesis and is a major upstream activator of the cell integrity pathway (CIP) and its core component, MAP kinase Pmk1, in response to environmental stimuli. We show that in vivo phosphorylation of Pck2 at the conserved T842 activation loop during growth and in response to different stresses is mediated by the PDK ortholog Ksg1 and an autophosphorylation mechanism. However, T842 phosphorylation is not essential for Pmk1 activation, and putative phosphorylation at T846 might play an additional role for Pck2 catalytic activation and downstream signaling. These events together with turn motif autophosphorylation at T984 and binding to small GTPases Rho1 and/or Rho2 stabilize and render Pck2 competent to exert its biological functions. Remarkably, the TORC2 complex does not participate in catalytic activation of Pck2, but instead contributes to de novo Pck2 synthesis which is essential to activate the CIP in response to cell wall damage or glucose exhaustion. These results unveil a novel mechanism whereby TOR regulates PKC function at a translational level and add a new regulatory layer to MAPK signaling cascades.
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