1
|
Ohtsuka H, Otsubo Y, Shimasaki T, Yamashita A, Aiba H. ecl family genes: Factors linking starvation and lifespan extension in Schizosaccharomyces pombe. Mol Microbiol 2023; 120:645-657. [PMID: 37525511 DOI: 10.1111/mmi.15134] [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: 04/18/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 08/02/2023]
Abstract
In the fission yeast Schizosaccharomyces pombe, the duration of survival in the stationary phase, termed the chronological lifespan (CLS), is affected by various environmental factors and the corresponding gene activities. The ecl family genes were identified in the genomic region encoding non-coding RNA as positive regulators of CLS in S. pombe, and subsequently shown to encode relatively short proteins. Several studies revealed that ecl family genes respond to various nutritional starvation conditions via different mechanisms, and they are additionally involved in stress resistance, autophagy, sexual differentiation, and cell cycle control. Recent studies reported that Ecl family proteins strongly suppress target of rapamycin complex 1, which is a conserved eukaryotic nutrient-sensing kinase complex that also regulates longevity in a variety of organisms. In this review, we introduce the regulatory mechanisms of Ecl family proteins and discuss their emerging findings.
Collapse
Affiliation(s)
- Hokuto Ohtsuka
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
| | - Yoko Otsubo
- Interdisciplinary Research Unit, National Institute for Basic Biology, Okazaki, Japan
| | - Takafumi Shimasaki
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
| | - Akira Yamashita
- Interdisciplinary Research Unit, National Institute for Basic Biology, Okazaki, Japan
| | - Hirofumi Aiba
- Laboratory of Molecular Microbiology, Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan
| |
Collapse
|
2
|
Barros GC, Guerrero S, Silva GM. The central role of translation elongation in response to stress. Biochem Soc Trans 2023; 51:959-969. [PMID: 37318088 PMCID: PMC11160351 DOI: 10.1042/bst20220584] [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: 02/06/2023] [Revised: 06/02/2023] [Accepted: 06/05/2023] [Indexed: 06/16/2023]
Abstract
Protein synthesis is essential to support homeostasis, and thus, must be highly regulated during cellular response to harmful environments. All stages of translation are susceptible to regulation under stress, however, the mechanisms involved in translation regulation beyond initiation have only begun to be elucidated. Methodological advances enabled critical discoveries on the control of translation elongation, highlighting its important role in translation repression and the synthesis of stress-response proteins. In this article, we discuss recent findings on mechanisms of elongation control mediated by ribosome pausing and collisions and the availability of tRNAs and elongation factors. We also discuss how elongation intersects with distinct modes of translation control, further supporting cellular viability and gene expression reprogramming. Finally, we highlight how several of these pathways are reversibly regulated, emphasizing the dynamics of translation control during stress-response progression. A comprehensive understanding of translation regulation under stress will produce fundamental knowledge of protein dynamics while opening new avenues and strategies to overcome dysregulated protein production and cellular sensitivity to stress.
Collapse
Affiliation(s)
| | | | - Gustavo M. Silva
- Department of Biology, Duke University, Durham, NC, USA
- Lead contact
| |
Collapse
|
3
|
Zhigailov AV, Nizkorodova AS, Sharipov KO, Polimbetova NS, Iskakov BK. Glyphosate treatment mediates the accumulation of small discrete 5'- and 3'-terminal fragments of 18S rRNA in plant cells. Vavilovskii Zhurnal Genet Selektsii 2023; 27:93-98. [PMID: 37063515 PMCID: PMC10090119 DOI: 10.18699/vjgb-23-13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 04/18/2023] Open
Abstract
Under many kinds of stress, eukaryotic cells rapidly decrease the overall translation level of the majority of mRNAs. However, some molecular mechanisms of protein synthesis inhibition like phosphorylation of eukaryotic elongation factor 2 (eEF2), which are known to be functional in animals and yeast, are not implemented in plants. We suggest that there is an alternative mechanism for the inhibition of protein synthesis in plant cells and possibly, in other eukaryotes, which is based on the discrete fragmentation of 18S rRNA molecules within small ribosomal subunits. We identified four stress-induced small RNAs, which are 5'- and 3'-terminal fragments of 18S rRNA. In the present work, we studied the induction of 18S rRNA discrete fragmentation and phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α) in germinated wheat embryos in the presence of glyphosate, which imitates the condition of amino acid starvation. Using northern and western blotting, we have shown that stress-induced 18S rRNA fragments started to accumulate in wheat embryos at glyphosate concentrations that did not evoke eIF2α phosphorylation. It was also found that cleavage of 18S rRNA near the 5'-terminus began much earlier than eIF2α phosphorylation, which became noticeable only at higher concentration (500 μM) of glyphosate. This result suggests that discrete fragmentation of 18S rRNA may constitute a regulatory mechanism of mRNA translation in response to stress and may occur in plant cells in parallel with and independently of eIF2α phosphorylation. The identified small 5'- and 3'-terminal fragments of 18S rRNA that accumulate during various stresses may serve as stress resistance markers in the breeding of economically important plant crops.
Collapse
Affiliation(s)
- A V Zhigailov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - A S Nizkorodova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - K O Sharipov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - N S Polimbetova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| | - B K Iskakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry of the Ministry of Science and Higher Education of the Republic of Kazakhstan, Almaty, Kazakhstan
| |
Collapse
|
4
|
Urano Y, Osaki S, Chiba R, Noguchi N. Integrated stress response is involved in the 24(S)-hydroxycholesterol-induced unconventional cell death mechanism. Cell Death Dis 2022; 8:406. [PMID: 36195595 PMCID: PMC9532424 DOI: 10.1038/s41420-022-01197-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 09/14/2022] [Accepted: 09/21/2022] [Indexed: 01/11/2023]
Abstract
Perturbation of proteostasis triggers the adaptive responses that contribute to the homeostatic pro-survival response, whereas disruption of proteostasis can ultimately lead to cell death. Brain-specific oxysterol-i.e., 24(S)-hydroxycholesterol (24S-OHC)-has been shown to cause cytotoxicity when esterified by acyl-CoA:cholesterol acyltransferase 1 (ACAT1) in the endoplasmic reticulum (ER). Here, we show that the accumulation of 24S-OHC esters caused phosphorylation of eukaryotic translation initiator factor 2α (eIF2α), dissociation of polysomes, and formation of stress granules (SG), resulting in robust downregulation of global protein de novo synthesis in human neuroblastoma SH-SY5Y cells. We also found that integrated stress response (ISR) activation through PERK and GCN2 activation induced by 24S-OHC treatment caused eIF2α phosphorylation. 24S-OHC-inducible SG formation and cell death were suppressed by inhibition of ISR. These results show that ACAT1-mediated 24S-OHC esterification induced ISR and formation of SG, which play crucial roles in 24S-OHC-inducible protein synthesis inhibition and unconventional cell death.
Collapse
Affiliation(s)
- Yasuomi Urano
- Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyoto, 610-0394, Japan.
| | - Shoya Osaki
- Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyoto, 610-0394, Japan
| | - Ren Chiba
- Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyoto, 610-0394, Japan
| | - Noriko Noguchi
- Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyoto, 610-0394, Japan.
| |
Collapse
|
5
|
Lokdarshi A, von Arnim AG. Review: Emerging roles of the signaling network of the protein kinase GCN2 in the plant stress response. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2022; 320:111280. [PMID: 35643606 PMCID: PMC9197246 DOI: 10.1016/j.plantsci.2022.111280] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 03/07/2022] [Accepted: 03/30/2022] [Indexed: 06/15/2023]
Abstract
The pan-eukaryotic protein kinase GCN2 (General Control Nonderepressible2) regulates the translation of mRNAs in response to external and metabolic conditions. Although GCN2 and its substrate, translation initiation factor 2 (eIF2) α, and several partner proteins are substantially conserved in plants, this kinase has assumed novel functions in plants, including in innate immunity and retrograde signaling between the chloroplast and cytosol. How exactly some of the biochemical paradigms of the GCN2 system have diverged in the green plant lineage is only partially resolved. Specifically, conflicting data underscore and cast doubt on whether GCN2 regulates amino acid biosynthesis; also whether phosphorylation of eIF2α can in fact repress global translation or activate mRNA specific translation via upstream open reading frames; and whether GCN2 is controlled in vivo by the level of uncharged tRNA. This review examines the status of research on the eIF2α kinase, GCN2, its function in the response to xenobiotics, pathogens, and abiotic stress conditions, and its rather tenuous role in the translational control of mRNAs.
Collapse
Affiliation(s)
- Ansul Lokdarshi
- Department of Biology, Valdosta State University, Valdosta, GA 31698, USA.
| | - Albrecht G von Arnim
- Department of Biochemistry & Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN 37996-1939, USA; UT-ORNL Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN 37996-1939, USA.
| |
Collapse
|
6
|
Mak T, Jones AW, Nurse P. The TOR-dependent phosphoproteome and regulation of cellular protein synthesis. EMBO J 2021; 40:e107911. [PMID: 34296454 PMCID: PMC8365262 DOI: 10.15252/embj.2021107911] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 05/28/2021] [Accepted: 06/09/2021] [Indexed: 01/21/2023] Open
Abstract
Cell growth is orchestrated by a number of interlinking cellular processes. Components of the TOR pathway have been proposed as potential regulators of cell growth, but little is known about their immediate effects on protein synthesis in response to TOR‐dependent growth inhibition. Here, we present a resource providing an in‐depth characterisation of Schizosaccharomyces pombe phosphoproteome in relation to changes observed in global cellular protein synthesis upon TOR inhibition. We find that after TOR inhibition, the rate of protein synthesis is rapidly reduced and that notable phosphorylation changes are observed in proteins involved in a range of cellular processes. We show that this reduction in protein synthesis rates upon TOR inhibition is not dependent on S6K activity, but is partially dependent on the S. pombe homologue of eIF4G, Tif471. Our study demonstrates the impact of TOR‐dependent phospho‐regulation on the rate of protein synthesis and establishes a foundational resource for further investigation of additional TOR‐regulated targets both in fission yeast and other eukaryotes.
Collapse
Affiliation(s)
- Tiffany Mak
- Cell Cycle Laboratory, The Francis Crick Institute, London, UK
| | - Andrew W Jones
- Cell Cycle Laboratory, The Francis Crick Institute, London, UK.,Protein Analysis and Proteomics Platform, The Francis Crick Institute, London, UK
| | - Paul Nurse
- Cell Cycle Laboratory, The Francis Crick Institute, London, UK.,Laboratory of Yeast Genetics and Cell Biology, Rockefeller University, New York, NY, USA
| |
Collapse
|
7
|
Rubio A, Ghosh S, Mülleder M, Ralser M, Mata J. Ribosome profiling reveals ribosome stalling on tryptophan codons and ribosome queuing upon oxidative stress in fission yeast. Nucleic Acids Res 2021; 49:383-399. [PMID: 33313903 PMCID: PMC7797079 DOI: 10.1093/nar/gkaa1180] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 11/13/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022] Open
Abstract
Translational control is essential in response to stress. We investigated the translational programmes launched by the fission yeast Schizosaccharomyces pombe upon five environmental stresses. We also explored the contribution of defence pathways to these programmes: The Integrated Stress Response (ISR), which regulates translation initiation, and the stress-response MAPK pathway. We performed ribosome profiling of cells subjected to each stress, in wild type cells and in cells with the defence pathways inactivated. The transcription factor Fil1, a functional homologue of the yeast Gcn4 and the mammalian Atf4 proteins, was translationally upregulated and required for the response to most stresses. Moreover, many mRNAs encoding proteins required for ribosome biogenesis were translationally downregulated. Thus, several stresses trigger a universal translational response, including reduced ribosome production and a Fil1-mediated transcriptional programme. Surprisingly, ribosomes stalled on tryptophan codons upon oxidative stress, likely due to a decrease in charged tRNA-Tryptophan. Stalling caused ribosome accumulation upstream of tryptophan codons (ribosome queuing/collisions), demonstrating that stalled ribosomes affect translation elongation by other ribosomes. Consistently, tryptophan codon stalling led to reduced translation elongation and contributed to the ISR-mediated inhibition of initiation. We show that different stresses elicit common and specific translational responses, revealing a novel role in Tryptophan-tRNA availability.
Collapse
Affiliation(s)
- Angela Rubio
- Department of Biochemistry, University of Cambridge, UK
| | - Sanjay Ghosh
- Department of Biochemistry, University of Cambridge, UK
| | - Michael Mülleder
- The Molecular Biology of Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - Markus Ralser
- The Molecular Biology of Metabolism Laboratory, The Francis Crick Institute, London, UK.,Department of Biochemistry, Charité University Medicine, Berlin, Germany
| | - Juan Mata
- Department of Biochemistry, University of Cambridge, UK
| |
Collapse
|
8
|
Sharma S, Sourirajan A, Baumler DJ, Dev K. Saccharomyces cerevisiae ER membrane protein complex subunit 4 (EMC4) plays a crucial role in eIF2B-mediated translation regulation and survival under stress conditions. J Genet Eng Biotechnol 2020; 18:15. [PMID: 32476094 PMCID: PMC7261713 DOI: 10.1186/s43141-020-00029-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/22/2020] [Indexed: 11/10/2022]
Abstract
Background Eukaryotic initiation factor 2B (eIF2B) initiates and regulates translation initiation in eukaryotes. eIF2B gene mutations cause leukoencephalopathy called vanishing white matter disease (VWM) in humans and slow growth (Slg−) and general control derepression (Gcd−) phenotypes in Saccharomyces cerevisiae. Results To suppress eIF2B mutations, S. cerevisiae genomic DNA library was constructed in high-copy vector (YEp24) and transformed into eIF2B mutant S. cerevisiae strains. The library was screened for wild-type genes rescuing S. cerevisiae (Slg−) and (Gcd−) phenotypes. A genomic clone, Suppressor-I (Sup-I), rescued S. cerevisiae Slg− and Gcd− phenotypes (gcd7-201 gcn2∆). The YEp24/Sup-I construct contained truncated TAN1, full length EMC4, full length YGL230C, and truncated SAP4 genes. Full length EMC4 (chaperone protein) gene was sub-cloned into pEG (KG) yeast expression vector and overexpressed in gcd7-201 gcn2∆ strain which suppressed the Slg− and Gcd− phenotype. A GST-Emc4 fusion protein of 47 kDa was detected by western blotting using α-GST antibodies. Suppression was specific to gcd7-201 gcn2∆ mutation in eIF2Bβ and Gcd1-502 gcn2∆ in eIF2Bγ subunit. Emc4p overexpression also protected the wild type and mutant (gcd7-201 gcn2∆, GCD7 gcn2∆, and GCD7 GCN2∆) strains from H2O2, ethanol, and caffeine stress. Conclusions Our results suggest that Emc4p is involved in eIF2B-mediated translational regulation under stress and could provide an amenable tool to understand the eIF2B-mediated defects.
Collapse
|
9
|
Mediani L, Galli V, Carrà AD, Bigi I, Vinet J, Ganassi M, Antoniani F, Tiago T, Cimino M, Mateju D, Cereda C, Pansarasa O, Alberti S, Mandrioli J, Carra S. BAG3 and BAG6 differentially affect the dynamics of stress granules by targeting distinct subsets of defective polypeptides released from ribosomes. Cell Stress Chaperones 2020; 25:1045-1058. [PMID: 32696179 PMCID: PMC7591658 DOI: 10.1007/s12192-020-01141-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/10/2020] [Accepted: 07/15/2020] [Indexed: 12/26/2022] Open
Abstract
Stress granules (SGs) are dynamic ribonucleoprotein granules induced by environmental stresses. They play an important role in the stress response by integrating mRNA stability, translation, and signaling pathways. Recent work has connected SG dysfunction to neurodegenerative diseases. In these diseases, SG dynamics are impaired because of mutations in SG proteins or protein quality control factors. Impaired SG dynamics and delayed SG dissolution have also been observed for SGs that accumulate misfolding-prone defective ribosomal products (DRiPs). DRiP accumulation inside SGs is controlled by a surveillance system referred to as granulostasis and encompasses the molecular chaperones VCP and the HSPB8-BAG3-HSP70 complex. BAG3 is a member of the BAG family of proteins, which includes five additional members. One of these proteins, BAG6, is functionally related to BAG3 and able to assist degradation of DRiPs. However, whether BAG6 is involved in granulostasis is unknown. We report that BAG6 is not recruited into SGs induced by different types of stress, nor does it affect SG dynamics. BAG6 also does not replace BAG3's function in SG granulostasis. We show that BAG3 and BAG6 target different subsets of DRiPs, and BAG3 binding to DRiPs is mediated by HSPB8 and HSP70. Our data support the idea that SGs are sensitive to BAG3-HSP70-bound DRiPs but not to BAG6-bound DRiPs. Additionally, only BAG3 is strongly upregulated in the stress recovery phase, when SGs dissolve. These data exclude a role for BAG6 in granulostasis and point to a more specialized function in the clearance of a specific subset of DRiPs.
Collapse
Affiliation(s)
- Laura Mediani
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Veronica Galli
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Arianna Dorotea Carrà
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Ilaria Bigi
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Jonathan Vinet
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Massimo Ganassi
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Francesco Antoniani
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Tatiana Tiago
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Marco Cimino
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Daniel Mateju
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307, Dresden, Germany
| | - Cristina Cereda
- Genomic and post-Genomic Center, IRCCS Mondino Foundation, Via Mondino 2, 27100, Pavia, Italy
| | - Orietta Pansarasa
- Genomic and post-Genomic Center, IRCCS Mondino Foundation, Via Mondino 2, 27100, Pavia, Italy
| | - Simon Alberti
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307, Dresden, Germany
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Tatzberg 47/49, 01307, Dresden, Germany
| | - Jessica Mandrioli
- Department of Neuroscience, St. Agostino Estense Hospital, Azienda Ospedaliero Universitaria di Modena, Modena, Italy
| | - Serena Carra
- Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy.
| |
Collapse
|
10
|
Jungers CF, Elliff JM, Masson-Meyers DS, Phiel CJ, Origanti S. Regulation of eukaryotic translation initiation factor 6 dynamics through multisite phosphorylation by GSK3. J Biol Chem 2020; 295:12796-12813. [PMID: 32703900 DOI: 10.1074/jbc.ra120.013324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 07/16/2020] [Indexed: 01/25/2023] Open
Abstract
Eukaryotic translation initiation factor 6 (eIF6) is essential for the synthesis of 60S ribosomal subunits and for regulating the association of 60S and 40S subunits. A mechanistic understanding of how eIF6 modulates translation in response to stress, specifically starvation-induced stress, is lacking. We here show a novel mode of eIF6 regulation by glycogen synthase kinase 3 (GSK3) that is predominantly active in response to serum starvation. Both GSK3α and GSK3β phosphorylate human eIF6. Multiple residues in the C terminus of eIF6 are phosphorylated by GSK3 in a sequential manner. In response to serum starvation, eIF6 accumulates in the cytoplasm, and this altered localization depends on phosphorylation by GSK3. Disruption of eIF6 phosphorylation exacerbates the translation inhibitory response to serum starvation and stalls cell growth. These results suggest that eIF6 regulation by GSK3 contributes to the attenuation of global protein synthesis that is critical for adaptation to starvation-induced stress.
Collapse
Affiliation(s)
- Courtney F Jungers
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Jonah M Elliff
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | | | - Christopher J Phiel
- Department of Integrative Biology, University of Colorado Denver, Colorado, USA
| | - Sofia Origanti
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA .,Department of Biology, Saint Louis University, St. Louis, Missouri, USA
| |
Collapse
|
11
|
Zhigailov AV, Alexandrova AM, Nizkorodova AS, Stanbekova GE, Kryldakov RV, Karpova OV, Polimbetova NS, Halford NG, Iskakov BK. Evidence That Phosphorylation of the α-Subunit of eIF2 Does Not Essentially Inhibit mRNA Translation in Wheat Germ Cell-Free System. FRONTIERS IN PLANT SCIENCE 2020; 11:936. [PMID: 32655610 PMCID: PMC7324750 DOI: 10.3389/fpls.2020.00936] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 06/09/2020] [Indexed: 05/30/2023]
Abstract
A mechanism based on reversible phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α) has been confirmed as an important regulatory pathway for the inhibition of protein synthesis in mammalian and yeast cells, while plants constitute the significant exception. We studied the induction of TaeIF2α phosphorylation in germinated wheat (Triticum aestivum) embryos subjected to different adverse conditions. Data confirmed that formation of TaeIF2(αP) was not a general response, as no phosphorylation was observed under salt, oxidative, or heat stress. Nevertheless, treatment by salicylic acid, UV-light, cold shock and histidinol did induce phosphorylation of TaeIF2α of wheat as has been established previously for AteIF2α in Arabidopsis (Arabidopsis thaliana). The influence of TaeIF2α phosphorylation on translation of reporter mRNA with different 5'-untranslated regions (5'UTRs) was studied in wheat germ cell-free system (WG-CFS), in which TaeIF2α was first phosphorylated either by heterologous recombinant human protein kinase, HsPKR (activated by double-stranded (ds)RNA), or by endogenous protein kinase TaGCN2 (activated by histidinol). Pretreatment of WG-CFS with HsPKR in the presence of dsRNA or with histidinol resulted in intense phosphorylation of TaeIF2α; however, the translation levels of all tested mRNAs decreased by only 10-15% and remained relatively high. In addition, factor OceIF2 from rabbit (Oryctolagus cuniculus) bound GDP much more strongly than the homologous factor TaeIF2 from wheat germ. Furthermore, factor OceIF2B was able to stimulate guanine nucleotide exchange (GDP→GTP) on OceIF2 but had no effect on a similar exchange on TaeIF2. These results suggest that the mechanism of stress response via eIF2α phosphorylation is not identical in all eukaryotes, and further research is required to find and study in detail new plant-specific mechanisms that may inhibit overall protein synthesis in plants under stress.
Collapse
Affiliation(s)
- Andrey V. Zhigailov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Alena M. Alexandrova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Anna S. Nizkorodova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Gulshan E. Stanbekova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Ruslan V. Kryldakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
- Institute of Plant Biology and Biotechnology, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Oxana V. Karpova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Nailya S. Polimbetova
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| | - Nigel G. Halford
- Plant Sciences Department, Rothamsted Research, Harpenden, United Kingdom
| | - Bulat K. Iskakov
- M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
- Institute of Plant Biology and Biotechnology, Science Committee, Ministry of Education and Science, Almaty, Kazakhstan
| |
Collapse
|
12
|
Lokdarshi A, Guan J, Urquidi Camacho RA, Cho SK, Morgan PW, Leonard M, Shimono M, Day B, von Arnim AG. Light Activates the Translational Regulatory Kinase GCN2 via Reactive Oxygen Species Emanating from the Chloroplast. THE PLANT CELL 2020; 32:1161-1178. [PMID: 32079667 PMCID: PMC7145473 DOI: 10.1105/tpc.19.00751] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 02/03/2020] [Accepted: 02/16/2020] [Indexed: 05/12/2023]
Abstract
Cytosolic mRNA translation is subject to global and mRNA-specific controls. Phosphorylation of the translation initiation factor eIF2α anchors a reversible regulatory switch that represses cytosolic translation globally. The stress-responsive GCN2 kinase is the only known kinase for eIF2α serine 56 in Arabidopsis (Arabidopsis thaliana). Here, we show that conditions that generate reactive oxygen species (ROS) in the chloroplast, including dark-light transitions, high light, and the herbicide methyl viologen, rapidly activated GCN2 kinase, whereas mitochondrial and endoplasmic reticulum stress did not. GCN2 activation was light dependent and mitigated by photosynthesis inhibitors and ROS quenchers. Accordingly, the seedling growth of multiple Arabidopsis gcn2 mutants was retarded under excess light conditions, implicating the GCN2-eIF2α pathway in responses to light and associated ROS. Once activated, GCN2 kinase preferentially suppressed the ribosome loading of mRNAs for functions such as mitochondrial ATP synthesis, the chloroplast thylakoids, vesicle trafficking, and translation. The gcn2 mutant overaccumulated transcripts functionally related to abiotic stress, including oxidative stress, as well as innate immune responses. Accordingly, gcn2 displayed defects in immune priming by the fungal elicitor, chitin. Therefore, we provide evidence that reactive oxygen species produced by the photosynthetic apparatus help activate the highly conserved GCN2 kinase, leading to eIF2α phosphorylation and thus affecting the status of the cytosolic protein synthesis apparatus.
Collapse
Affiliation(s)
- Ansul Lokdarshi
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Ju Guan
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Ricardo A Urquidi Camacho
- UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996
| | - Sung Ki Cho
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Philip W Morgan
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Madison Leonard
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Masaki Shimono
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824
| | - Brad Day
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824
| | - Albrecht G von Arnim
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
- UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996
| |
Collapse
|
13
|
Norovirus infection results in eIF2α independent host translation shut-off and remodels the G3BP1 interactome evading stress granule formation. PLoS Pathog 2020; 16:e1008250. [PMID: 31905230 PMCID: PMC6964919 DOI: 10.1371/journal.ppat.1008250] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 01/16/2020] [Accepted: 12/04/2019] [Indexed: 12/14/2022] Open
Abstract
Viral infections impose major stress on the host cell. In response, stress pathways can rapidly deploy defence mechanisms by shutting off the protein synthesis machinery and triggering the accumulation of mRNAs into stress granules to limit the use of energy and nutrients. Because this threatens viral gene expression, viruses need to evade these pathways to propagate. Human norovirus is responsible for gastroenteritis outbreaks worldwide. Here we examined how norovirus interacts with the eIF2α signaling axis controlling translation and stress granules. While norovirus infection represses host cell translation, our mechanistic analyses revealed that eIF2α signaling mediated by the stress kinase GCN2 is uncoupled from translational stalling. Moreover, infection results in a redistribution of the RNA-binding protein G3BP1 to replication complexes and remodelling of its interacting partners, allowing the avoidance from canonical stress granules. These results define novel strategies by which norovirus undergo efficient replication whilst avoiding the host stress response and manipulating the G3BP1 interactome. Viruses have evolved elegant strategies to evade host responses that restrict viral propagation by targeting the protein synthesis machinery and stress granules, which are membrane-less RNA granules with antiviral properties. Previous studies have unravelled how viruses, including norovirus the leading cause of gastroenteritis, regulate the activity of translation factors to affect the antiviral response. Furthermore, stress granules evasion strategies have been linked to targeting the scaffolding protein G3BP1. Here we dissect how murine norovirus, the main model for norovirus, evades the cellular stress responses. Our work challenges the dogma that translational control during infection is mainly mediated by eIF2α and demonstrate that norovirus evades this stress pathway. We further show that norovirus evades the stress granule response in a novel way by isolating and characterising the G3BP1 interactome for the first time in the context of a viral infection. We conclude that norovirus infection results in a redistribution of G3BP1 and its cellular partners to replication complexes, thereby preventing the assembly of stress granules. Overall, we define a novel evasion strategy by which norovirus escapes stress granule formation by rewiring the G3BP1 interactome.
Collapse
|
14
|
Sprooten J, Garg AD. Type I interferons and endoplasmic reticulum stress in health and disease. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2019; 350:63-118. [PMID: 32138904 PMCID: PMC7104985 DOI: 10.1016/bs.ircmb.2019.10.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type I interferons (IFNs) comprise of pro-inflammatory cytokines created, as well as sensed, by all nucleated cells with the main objective of blocking pathogens-driven infections. Owing to this broad range of influence, type I IFNs also exhibit critical functions in many sterile inflammatory diseases and immunopathologies, especially those associated with endoplasmic reticulum (ER) stress-driven signaling pathways. Indeed, over the years accumulating evidence has indicated that the presence of ER stress can influence the production, or sensing of, type I IFNs induced by perturbations like pattern recognition receptor (PRR) agonists, infections (bacterial, viral or parasitic) or autoimmunity. In this article we discuss the link between type I IFNs and ER stress in various diseased contexts. We describe how ER stress regulates type I IFNs production or sensing, or how type I IFNs may induce ER stress, in various circumstances like microbial infections, autoimmunity, diabetes, cancer and other ER stress-related contexts.
Collapse
Affiliation(s)
- Jenny Sprooten
- Department for Cellular and Molecular Medicine, Cell Death Research & Therapy (CDRT) Unit, KU Leuven, Leuven, Belgium
| | - Abhishek D Garg
- Department for Cellular and Molecular Medicine, Cell Death Research & Therapy (CDRT) Unit, KU Leuven, Leuven, Belgium.
| |
Collapse
|
15
|
Sanchez M, Lin Y, Yang CC, McQuary P, Rosa Campos A, Aza Blanc P, Wolf DA. Cross Talk between eIF2α and eEF2 Phosphorylation Pathways Optimizes Translational Arrest in Response to Oxidative Stress. iScience 2019; 20:466-480. [PMID: 31627132 PMCID: PMC6823656 DOI: 10.1016/j.isci.2019.09.031] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 06/14/2019] [Accepted: 09/23/2019] [Indexed: 01/26/2023] Open
Abstract
The cellular stress response triggers a cascade of events leading to transcriptional reprogramming and a transient inhibition of global protein synthesis, which is thought to be mediated by phosphorylation of eukaryotic initiation factor-2α (eIF2α). Using mouse embryonic fibroblasts (MEFs) and the fission yeast S. pombe, we report that rapid translational arrest and cell survival in response to hydrogen peroxide-induced oxidative stress do not rely on eIF2α kinases and eIF2α phosphorylation. Rather, H2O2 induces a block in elongation through phosphorylation of eukaryotic elongation factor 2 (eEF2). Kinetic and dose-response analyses uncovered cross talk between the eIF2α and eEF2 phosphorylation pathways, indicating that, in MEFs, eEF2 phosphorylation initiates the acute shutdown in translation, which is maintained by eIF2α phosphorylation. Our results challenge the common conception that eIF2α phosphorylation is the primary trigger of translational arrest in response to oxidative stress and point to integrated control that may facilitate the survival of cancer cells. Oxidative stress-induced translation arrest is independent of eIF2α phosphorylation Oxidative stress blocks translation elongation Oxidative stress triggers eEF2 kinase activation eEF2K KO cells are hypersensitive to oxidative stress
Collapse
Affiliation(s)
- Marisa Sanchez
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.
| | - Yingying Lin
- School of Pharmaceutical Sciences, Fujian Provincial Key Laboratory of Innovative Drug Target Research and Center for Stress Signaling Networks, Xiamen University, Xiamen 361102, China
| | - Chih-Cheng Yang
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Philip McQuary
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | | | - Pedro Aza Blanc
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Dieter A Wolf
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA; School of Pharmaceutical Sciences, Fujian Provincial Key Laboratory of Innovative Drug Target Research and Center for Stress Signaling Networks, Xiamen University, Xiamen 361102, China.
| |
Collapse
|
16
|
Boye E, Grallert B. eIF2α phosphorylation and the regulation of translation. Curr Genet 2019; 66:293-297. [PMID: 31485739 DOI: 10.1007/s00294-019-01026-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/13/2019] [Accepted: 08/16/2019] [Indexed: 12/27/2022]
Abstract
We discuss novel insight into the role and consequences of the phosphorylation of the translation initiation factor eIF2α in the context of stress responses and cell-cycle regulation. eIF2α is centrally located to regulate translation and its phosphorylation in response to different environmental challenges is one of the best characterized stress-response pathways. In addition to its role in stress management, eIF2α phosphorylation is also linked to cell-cycle progression and memory consolidation in the nervous system. The best known consequences of eIF2α phosphorylation are downregulation of global translation and stimulation of translation of some mRNAs. However, recent evidence shows that (i) eIF2α phosphorylation is not always required for the downregulation of global translation after exposure to stress and (ii) eIF2α phosphorylation does not necessarily lead to the downregulation of global translation. These results suggest that the textbook view of eIF2α phosphorylation needs to be revised and that there must be additional regulatory mechanisms at play.
Collapse
Affiliation(s)
- Erik Boye
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.
| |
Collapse
|
17
|
Samluk L, Urbanska M, Kisielewska K, Mohanraj K, Kim MJ, Machnicka K, Liszewska E, Jaworski J, Chacinska A. Cytosolic translational responses differ under conditions of severe short-term and long-term mitochondrial stress. Mol Biol Cell 2019; 30:1864-1877. [PMID: 31116686 PMCID: PMC6727742 DOI: 10.1091/mbc.e18-10-0628] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Previous studies demonstrated that cells inhibit protein synthesis as a compensatory mechanism for mitochondrial dysfunction. Protein synthesis can be attenuated by 1) the inhibition of mTOR kinase, which results in a decrease in the phosphorylation of S6K1 and 4E-BP1 proteins, and 2) an increase in the phosphorylation of eIF2α protein. The present study investigated both of these pathways under conditions of short-term acute and long-term mitochondrial stress. Short-term responses were triggered in mammalian cells by treatment with menadione, antimycin A, or CCCP. Long-term mitochondrial stress was induced by prolonged treatment with menadione or rotenone and expression of genetic alterations, such as knocking down the MIA40 oxidoreductase or knocking out NDUFA11 protein. Short-term menadione, antimycin A, or CCCP cell treatment led to the inhibition of protein synthesis, accompanied by a decrease in mTOR kinase activity, an increase in the phosphorylation of eIF2α (Ser51), and an increase in the level of ATF4 transcription factor. Conversely, long-term stress led to a decrease in eIF2α (Ser51) phosphorylation and ATF4 expression and to an increase in S6K1 (Thr389) phosphorylation. Thus, under long-term mitochondrial stress, cells trigger long-lasting adaptive responses for protection against excessive inhibition of protein synthesis.
Collapse
Affiliation(s)
- Lukasz Samluk
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.,International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Malgorzata Urbanska
- Department of Neurology and Epileptology, Children's Memorial Health Institute, Warsaw 04-730, Poland
| | | | - Karthik Mohanraj
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.,ReMedy International Research Agenda Unit, University of Warsaw, Warsaw 02-097, Poland
| | - Min-Ji Kim
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland
| | - Katarzyna Machnicka
- International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Ewa Liszewska
- International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Jacek Jaworski
- International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Agnieszka Chacinska
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.,International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland.,ReMedy International Research Agenda Unit, University of Warsaw, Warsaw 02-097, Poland
| |
Collapse
|
18
|
Hochberg-Laufer H, Schwed-Gross A, Neugebauer KM, Shav-Tal Y. Uncoupling of nucleo-cytoplasmic RNA export and localization during stress. Nucleic Acids Res 2019; 47:4778-4797. [PMID: 30864659 PMCID: PMC6511838 DOI: 10.1093/nar/gkz168] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 02/26/2019] [Accepted: 03/02/2019] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic cells contain sub-cellular compartments that are not membrane bound. Some structures are always present, such as nuclear speckles that contain RNA-binding proteins (RBPs) and poly(A)+ RNAs. Others, like cytoplasmic stress granules (SGs) that harbor mRNAs and RBPs, are induced upon stress. When we examined the formation and composition of nuclear speckles during stress induction with tubercidin, an adenosine analogue previously shown to affect nuclear speckle composition, we unexpectedly found that it also led to the formation of SGs and to the inhibition of several crucial steps of RNA metabolism in cells, thereby serving as a potent inhibitor of the gene expression pathway. Although transcription and splicing persisted under this stress, RBPs and mRNAs were mislocalized in the nucleus and cytoplasm. Specifically, lncRNA and RBP localization to nuclear speckles was disrupted, exon junction complex (EJC) recruitment to mRNA was reduced, mRNA export was obstructed, and cytoplasmic poly(A)+ RNAs localized in SGs. Furthermore, nuclear proteins that participate in mRNA export, such as nucleoporins and mRNA export adaptors, were mislocalized to SGs. This study reveals structural aspects of granule assembly in cells, and describes how the flow of RNA from the nucleus to the cytoplasm is severed under stress.
Collapse
Affiliation(s)
- Hodaya Hochberg-Laufer
- The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Avital Schwed-Gross
- The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Karla M Neugebauer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Yaron Shav-Tal
- The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| |
Collapse
|
19
|
Back S, Gorman AW, Vogel C, Silva GM. Site-Specific K63 Ubiquitinomics Provides Insights into Translation Regulation under Stress. J Proteome Res 2018; 18:309-318. [PMID: 30489083 DOI: 10.1021/acs.jproteome.8b00623] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During oxidative stress, K63-linked polyubiquitin chains modify a variety of proteins including ribosomes. Knowledge of the precise sites of K63 ubiquitin is key to understand its function during the response to stress. To identify the sites of K63 ubiquitin, we developed a new mass spectrometry based method that quantified >1100 K63 ubiquitination sites in yeast that responded to oxidative stress induced by H2O2. We determined that under stress, K63 ubiquitin-modified proteins were involved in several cellular functions including ion transport, protein trafficking, and translation. The most abundant ubiquitin sites localized to the head of the 40S subunit of the ribosome, modified assembled polysomes, and affected the binding of translation factors. The results suggested a new pathway of post-initiation control of translation during oxidative stress and illustrated the importance of high-resolution mapping of noncanonical ubiquitination events.
Collapse
Affiliation(s)
- Songhee Back
- Center for Genomics and Systems Biology , New York University , 12 Waverly Place , New York , New York 10003 , United States
| | - Andrew W Gorman
- Department of Biology , Duke University , 130 Science Drive , Durham , North Carolina 27708 , United States
| | - Christine Vogel
- Center for Genomics and Systems Biology , New York University , 12 Waverly Place , New York , New York 10003 , United States
| | - Gustavo M Silva
- Department of Biology , Duke University , 130 Science Drive , Durham , North Carolina 27708 , United States
| |
Collapse
|
20
|
Paraquat-Mediated Oxidative Stress in Anopheles gambiae Mosquitoes Is Regulated by An Endoplasmic Reticulum (ER) Stress Response. Proteomes 2018; 6:proteomes6040047. [PMID: 30424486 PMCID: PMC6313908 DOI: 10.3390/proteomes6040047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 11/07/2018] [Accepted: 11/09/2018] [Indexed: 11/20/2022] Open
Abstract
Paraquat is a potent superoxide (O2−)-inducing agent that is capable of inducing an oxidative imbalance in the mosquito midgut. This oxidative imbalance can super-stress the malaria parasite, leading to arrested development in the mosquito midgut and reduced transmission. While several studies have explored the effect of paraquat on malaria parasites, a fundamental understanding of the mosquito response to this compound remains unknown. Here, we quantified the mosquito midgut proteomic response to a paraquat-laced sugar meal, and found that An. gambiae midguts were enriched in proteins that are indicative of cells under endoplasmic reticulum (ER) stress. We also carried out qRT-PCR analyses for nine prominent thioredoxin (Trx) and glutathione (GSH)-dependent genes in mosquito midguts post P. falciparum blood meal ingestion to evaluate the concordance between transcripts and proteins under different oxidative stress conditions. Our data revealed an absence of significant upregulation in the Trx and GSH-dependent genes following infected blood meal ingestion. These data suggest that the intrinsic tolerance of the mosquito midgut to paraquat-mediated oxidative stress is through an ER stress response. These data indicate that mosquitoes have at least two divergent pathways of managing the oxidative stress that is induced by exogenous compounds, and outline the potential application of paraquat-like drugs to act selectively against malaria parasite development in mosquito midguts, thereby blocking mosquito-to-human transmission.
Collapse
|
21
|
Stonyte V, Boye E, Grallert B. Regulation of global translation during the cell cycle. J Cell Sci 2018; 131:jcs.220327. [PMID: 30072440 DOI: 10.1242/jcs.220327] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/20/2018] [Indexed: 01/10/2023] Open
Abstract
It is generally accepted that global translation varies during the cell cycle and is low during mitosis. However, addressing this issue is challenging because it involves cell synchronization, which evokes stress responses that, in turn, affect translation rates. Here, we have used two approaches to measure global translation rates in different cell-cycle phases. First, synchrony in different cell-cycle phases was obtained involving the same stress, by using temperature-sensitive mutants. Second, translation and DNA content were measured by flow cytometry in exponentially growing, single cells. We found no major variation in global translation rates through the cell cycle in either fission yeast or mammalian cells. We also measured phosphorylation of eukaryotic initiation factor-2α, an event that is thought to downregulate global translation in mitosis. In contrast with the prevailing view, eIF2α phosphorylation correlated poorly with downregulation of global translation and ectopically induced eIF2α phosphorylation inhibited global translation only at high levels.
Collapse
Affiliation(s)
- Vilte Stonyte
- Department of Radiation Biology, Institute for Cancer Research, Montebello, 0379 Oslo University Hospital, Oslo, Norway
| | - Erik Boye
- Department of Radiation Biology, Institute for Cancer Research, Montebello, 0379 Oslo University Hospital, Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Montebello, 0379 Oslo University Hospital, Oslo, Norway
| |
Collapse
|
22
|
Alberti S, Carra S. Quality Control of Membraneless Organelles. J Mol Biol 2018; 430:4711-4729. [PMID: 29758260 DOI: 10.1016/j.jmb.2018.05.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/04/2018] [Accepted: 05/04/2018] [Indexed: 02/06/2023]
Abstract
The formation of membraneless organelles (MLOs) by phase separation has emerged as a new way of organizing the cytoplasm and nucleoplasm of cells. Examples of MLOs forming via phase separation are nucleoli in the nucleus and stress granules in the cytoplasm. The main components of these MLOs are macromolecules such as RNAs and proteins. In order to assemble by phase separation, these proteins and RNAs have to undergo many cooperative interactions. These cooperative interactions are supported by specific molecular features within phase-separating proteins, such as multivalency and the presence of disordered domains that promote weak and transient interactions. However, these features also predispose phase-separating proteins to aberrant behavior. Indeed, evidence is emerging for a strong link between phase-separating proteins, MLOs, and age-related diseases. In this review, we discuss recent progress in understanding the formation, properties, and functions of MLOs. We pay special attention to the emerging link between MLOs and age-related diseases, and we explain how changes in the composition and physical properties of MLOs promote their conversion into an aberrant state. Furthermore, we discuss the key role of the protein quality control machinery in regulating the properties and functions of MLOs and thus in preventing age-related diseases.
Collapse
Affiliation(s)
- Simon Alberti
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
| | - Serena Carra
- Department of Biomedical, Metabolic and Neural Science, University of Modena and Reggio Emilia, Center for Neuroscience and Neurotechnology, 41125 Modena, Italy.
| |
Collapse
|
23
|
White MC, Schroeder RD, Zhu K, Xiong K, McConkey DJ. HRI-mediated translational repression reduces proteotoxicity and sensitivity to bortezomib in human pancreatic cancer cells. Oncogene 2018; 37:4413-4427. [PMID: 29720726 PMCID: PMC6138554 DOI: 10.1038/s41388-018-0227-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 10/26/2017] [Accepted: 11/03/2017] [Indexed: 12/31/2022]
Abstract
Human cancer cells display extensive heterogeneity in their sensitivities to the proteasome inhibitor bortezomib (Velcade). The molecular mechanisms underlying this heterogeneity remain unclear, and strategies to overcome resistance are limited. Here, we discover that inherent differences in eIF2α phosphorylation among a panel of ten human pancreatic cancer cell lines significantly impacts bortezomib sensitivity, and implicate the HRI (heme-regulated inhibitor) eIF2α kinase as a novel therapeutic target. Within our panel, we identified a subset of cell lines with defective induction of eIF2α phosphorylation, conferring a high degree of sensitivity to bortezomib. These bortezomib-sensitive cells exhibited impaired translation attenuation followed by toxic accumulation of protein aggregates and reactive oxygen species (ROS), whereas the bortezomib-resistant cell lines displayed increased phosphorylation of eIF2α, decreased translation, few protein aggregates, and minimal ROS production. Importantly, we identified HRI as the primary bortezomib-activated eIF2α kinase, and demonstrated that HRI knockdown promoted cell death in the bortezomib-resistant cells. Overall, our data implicate inducible HRI-mediated phosphorylation of eIF2α as a central cytoprotective mechanism following exposure to bortezomib and provide proof-of-concept for the development of HRI inhibitors to overcome proteasome inhibitor resistance.
Collapse
Affiliation(s)
- Matthew C White
- Departments of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.,Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.,The Program in Experimental Therapeutics, The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA
| | - Rebecca D Schroeder
- The Program in Experimental Therapeutics, The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA
| | - Keyi Zhu
- Departments of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.,Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Katherine Xiong
- Departments of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.,Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - David J McConkey
- Departments of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA. .,Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA. .,The Program in Experimental Therapeutics, The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA. .,Johns Hopkins Greenberg Bladder Cancer Institute, Baltimore, MD, 21287, USA.
| |
Collapse
|
24
|
Interplay between P-Glycoprotein Expression and Resistance to Endoplasmic Reticulum Stressors. Molecules 2018; 23:molecules23020337. [PMID: 29415493 PMCID: PMC6017601 DOI: 10.3390/molecules23020337] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 01/30/2018] [Accepted: 02/01/2018] [Indexed: 12/13/2022] Open
Abstract
Multidrug resistance (MDR) is a phenotype of cancer cells with reduced sensitivity to a wide range of unrelated drugs. P-glycoprotein (P-gp)—a drug efflux pump (ABCB1 member of the ABC transporter gene family)—is frequently observed to be a molecular cause of MDR. The drug-efflux activity of P-gp is considered as the underlying mechanism of drug resistance against P-gp substrates and results in failure of cancer chemotherapy. Several pathological impulses such as shortages of oxygen and glucose supply, alterations of calcium storage mechanisms and/or processes of protein N-glycosylation in the endoplasmic reticulum (ER) leads to ER stress (ERS), characterized by elevation of unfolded protein cell content and activation of the unfolded protein response (UPR). UPR is responsible for modification of protein folding pathways, removal of misfolded proteins by ER associated protein degradation (ERAD) and inhibition of proteosynthesis. However, sustained ERS may result in UPR-mediated cell death. Neoplastic cells could escape from the death pathway induced by ERS by switching UPR into pro survival mechanisms instead of apoptosis. Here, we aimed to present state of the art information about consequences of P-gp expression on mechanisms associated with ERS development and regulation of the ERAD system, particularly focused on advances in ERS-associated therapy of drug resistant malignancies.
Collapse
|
25
|
Rothe C, Rødland GE, Anda S, Stonyte V, Boye E, Lopez-Aviles S, Grallert B. A checkpoint-independent mechanism delays entry into mitosis after UV irradiation. J Cell Sci 2017; 130:4028-4037. [PMID: 29046339 DOI: 10.1242/jcs.204693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 10/16/2017] [Indexed: 12/30/2022] Open
Abstract
When cells are exposed to stress they delay entry into mitosis. The most extensively studied mechanism behind this delay is the DNA-damage-induced G2/M checkpoint. Here, we show the existence of an additional stress-response pathway in Schizosaccharomyces pombe that is independent of the classic ATR/Rad3-dependent checkpoint. This novel mechanism delays entry mitosis independently of the spindle assembly checkpoint and the mitotic kinases Fin1, Ark1 and Plo1. The pathway delays activation of the mitotic cyclin-dependent kinase (CDK) Cdc2 after UV irradiation. Furthermore, we demonstrate that translation of the mitotic cyclin Cdc13 is selectively downregulated after UV irradiation, and we propose that this downregulation of Cdc13 contributes to the delayed activation of Cdc2 and the delayed mitosis.
Collapse
Affiliation(s)
- Christiane Rothe
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Gro Elise Rødland
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Silje Anda
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Vilte Stonyte
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway.,Centre for Molecular Medicine Norway, University of Oslo, Gaustadalléen 21, 0349 Oslo, Norway
| | - Erik Boye
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Sandra Lopez-Aviles
- Centre for Molecular Medicine Norway, University of Oslo, Gaustadalléen 21, 0349 Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| |
Collapse
|
26
|
Anda S, Zach R, Grallert B. Activation of Gcn2 in response to different stresses. PLoS One 2017; 12:e0182143. [PMID: 28771613 PMCID: PMC5542535 DOI: 10.1371/journal.pone.0182143] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 07/12/2017] [Indexed: 12/12/2022] Open
Abstract
All organisms have evolved pathways to respond to different forms of cellular stress. The Gcn2 kinase is best known as a regulator of translation initiation in response to starvation for amino acids. Work in budding yeast has showed that the molecular mechanism of GCN2 activation involves the binding of uncharged tRNAs, which results in a conformational change and GCN2 activation. This pathway requires GCN1, which ensures delivery of the uncharged tRNA onto GCN2. However, Gcn2 is activated by a number of other stresses which do not obviously involve accumulation of uncharged tRNAs, raising the question how Gcn2 is activated under these conditions. Here we investigate the requirement for ongoing translation and tRNA binding for Gcn2 activation after different stresses in fission yeast. We find that mutating the tRNA-binding site on Gcn2 or deleting Gcn1 abolishes Gcn2 activation under all the investigated conditions. These results suggest that tRNA binding to Gcn2 is required for Gcn2 activation not only in response to starvation but also after UV irradiation and oxidative stress.
Collapse
Affiliation(s)
- Silje Anda
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Róbert Zach
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
- * E-mail:
| |
Collapse
|
27
|
Aledo JC. Inferring Methionine Sulfoxidation and serine Phosphorylation crosstalk from Phylogenetic analyses. BMC Evol Biol 2017; 17:171. [PMID: 28750604 PMCID: PMC5530960 DOI: 10.1186/s12862-017-1017-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 07/19/2017] [Indexed: 11/10/2022] Open
Abstract
Background The sulfoxidation of methionine residues within the phosphorylation motif of protein kinase substrates, may provide a mechanism to couple oxidative signals to changes in protein phosphorylation. Herein, we hypothesize that if the residues within a pair of phosphorylatable-sulfoxidable sites are functionally linked, then they might have been coevolving. To test this hypothesis a number of site pairs previously detected on human stress-related proteins has been subjected to analysis using eukaryote ortholog sequences and a phylogenetic approach. Results Overall, the results support the conclusion that in the eIF2α protein, serine phosphorylation at position 218 and methionine oxidation at position 222, belong to the same functional network. First, the observed data were much better fitted by Markovian models that assumed coevolution of both sites, with respect to their counterparts assuming independent evolution (p-value = 0.003). Second, this conclusion was robust with respect to the methods used to reconstruct the phylogenetic relationship between the 233 eukaryotic species analyzed. Third, the co-distribution of phosphorylatable and sulfoxidable residues at these positions showed multiple origins throughout the evolution of eukaryotes, which further supports the view of an adaptive value for this co-occurrence. Fourth, the possibility that the coevolution of these two sites might be due to structure-driven compensatory mutations was evaluated. The results suggested that factors other than those merely structural were behind the observed coevolution. Finally, the relationship detected between other modifiable site pairs from ataxin-2 (S814-M815), ataxin-2-like (S211-M215) and Pumilio homolog 1 (S124-M125), reinforce the view of a role for phosphorylation-sulfoxidation crosstalk. Conclusions For the four stress-related proteins analyzed herein, their respective pairs of PTM sites (phosphorylatable serine and sulfoxidable methionine) were found to be evolving in a correlated fashion, which suggests a relevant role for methionine sulfoxidation and serine phosphorylation crosstalk in the control of protein translation under stress conditions. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-1017-9) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Juan Carlos Aledo
- Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, 29071, Málaga, Spain.
| |
Collapse
|
28
|
Sharma S, Sourirajan A, Dev K. Role of Saccharomyces cerevisiae TAN1 (tRNA acetyltransferase) in eukaryotic initiation factor 2B (eIF2B)-mediated translation control and stress response. 3 Biotech 2017; 7:223. [PMID: 28677085 DOI: 10.1007/s13205-017-0857-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 06/17/2017] [Indexed: 10/19/2022] Open
Abstract
Eukaryotic initiation factor 2B (eIF2B) controls the first step of translation by catalyzing guanine nucleotide exchange on eukaryotic initiation factor 2 (eIF2). Mutations in the genes encoding eIF2B subunits inhibit the nucleotide exchange and eventually slow down the process of translation, causing vanishing white matter disease. We constructed a Saccharomyces cerevisiae genomic DNA library in YEp24 vector and screened it for the identification of extragenic suppressors of eIF2B mutations, corresponding to human eIF2B mutations. We found a suppressor-II (Sup-II) genomic clone, as suppressor of eIF2Bβ (gcd7-201) mutation. Identification of Sup-II reveals the presence of truncated SEC15, full-length TAN1 (tRNA acetyltransferase), full-length EMC4, full-length YGL230C (putative protein) and truncated SAP4 genes. Full-length TAN1 (tRNA acetyltransferase) gene, subcloned into pEG(KG) vector and overexpressed in gcd7-201 gcn2∆ strain, suppresses the slow-growth (Slg-) and general control derepression (Gcd-) phenotype of gcd7-201 gcn2∆ mutation, but YGL230C did not show any effect. A GST-Tan1p fusion protein of 60 kDa was detected by western blotting using α-GST antibodies. Interestingly, Tan1p overexpression also suppresses the temperature-sensitive (Ts-), Slg- and Gcd- phenotype of eIF2Bγ (gcd1-502) mutant. Role of Tan1p protein in eIF2B-mediated translation regulation was also studied. Results revealed that Tan1p overexpression confers resistance to GCD7 GCN2, gcd7-201 gcn2∆, GCD7 gcn2∆ growth defect under ethanol, H2O2 and caffeine stress. No resistance to DMSO-, NaCl- and DTT-mediated growth defect upon GCD7 gcn2∆, GCD7 GCN2, gcd7-201 gcn2∆ was observed by overexpression of TAN1. Hence, we proposed that Tan1p is involved directly or indirectly in regulating eIF2B-mediated translation.
Collapse
Affiliation(s)
- Sonum Sharma
- Faculty of Applied Sciences and Biotechnology, Shoolini University, Solan, Himachal Pradesh, India
| | - Anuradha Sourirajan
- Faculty of Applied Sciences and Biotechnology, Shoolini University, Solan, Himachal Pradesh, India
| | - Kamal Dev
- Faculty of Applied Sciences and Biotechnology, Shoolini University, Solan, Himachal Pradesh, India.
| |
Collapse
|
29
|
Differential processing of small RNAs during endoplasmic reticulum stress. Sci Rep 2017; 7:46080. [PMID: 28452371 PMCID: PMC5408347 DOI: 10.1038/srep46080] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 03/10/2017] [Indexed: 12/30/2022] Open
Abstract
The accumulation of misfolded proteins in the endoplasmic reticulum (ER) lumen due to the disruption of the homeostatic system of the ER leads to the induction of the ER stress response. Cellular stress-induced pathways globally transform genes expression on both the transcriptional and post-transcriptional levels with small RNA involvement as regulators of the stress response. The modulation of small RNA processing might represent an additional layer of a complex stress response program. However, it is poorly understood. Here, we studied changes in expression and small RNAs processing upon ER stress in Jurkat T-cells. Induced by ER-stress, depletion of miRNAs among small RNA composition was accompanied by a global decrease of 3′ mono-adenylated, mono-cytodinylated and a global increase of 3′ mono-uridinylated miRNA isoforms. We observed the specific subset of differentially expressed microRNAs, and also the dramatic induction of 32-nt tRNA fragments precisely phased to 5′ and 3′ ends of tRNA from a subset of tRNA isotypes. The induction of these tRNA fragments was linked to Angiogenin RNase, which mediates translation inhibition. Overall, the global perturbations of the expression and processing of miRNAs and tiRNAs were the most prominent features of small RNA transcriptome changes upon ER stress.
Collapse
|
30
|
Ballester-Tomás L, Prieto JA, Alepuz P, González A, Garre E, Randez-Gil F. Inappropriate translation inhibition and P-body formation cause cold-sensitivity in tryptophan-auxotroph yeast mutants. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1864:314-323. [PMID: 27864078 DOI: 10.1016/j.bbamcr.2016.11.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 10/28/2016] [Accepted: 11/14/2016] [Indexed: 11/18/2022]
Abstract
In response to different adverse conditions, most eukaryotic organisms, including Saccharomyces cerevisiae, downregulate protein synthesis through the phosphorylation of eIF2α (eukaryotic initiation factor 2α) by Gcn2, a highly conserved protein kinase. Gcn2 also controls the translation of Gcn4, a transcription factor involved in the induction of amino acid biosynthesis enzymes. Here, we have studied the functional role of Gcn2 and Gcn2-regulating proteins, in controlling translation during temperature downshifts of TRP1 and trp1 yeast cells. Our results suggest that neither cold-instigated amino acid limitation nor Gcn2 are involved in the translation suppression at low temperature. However, loss of TRP1 causes increased eIF2α phosphorylation, Gcn2-dependent polysome disassembly and overactivity of Gcn4, which result in cold-sensitivity. Indeed, knock-out of GCN2 improves cold growth of trp1 cells. Likewise, mutation of several Gcn2-regulators and effectors results in cold-growth effects. Remarkably, we found that Hog1, the osmoresponsive MAPK, plays a role in the regulatory mechanism of Gcn2-eIF2α. Finally, we demonstrated that P-body formation responds to a downshift in temperature in a TRP1-dependent manner and is required for cold tolerance.
Collapse
Affiliation(s)
- Lidia Ballester-Tomás
- Department of Biotechnology, Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas, Avda. Agustín Escardino, 7, 46980-Paterna, Valencia, Spain
| | - Jose A Prieto
- Department of Biotechnology, Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas, Avda. Agustín Escardino, 7, 46980-Paterna, Valencia, Spain
| | - Paula Alepuz
- Departament of Biochemistry and Molecular Biology, ERI Biotecmed, Universitat de València, Dr. Moliner 50, Burjassot 46100, Spain
| | | | - Elena Garre
- Department of Biotechnology, Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas, Avda. Agustín Escardino, 7, 46980-Paterna, Valencia, Spain
| | - Francisca Randez-Gil
- Department of Biotechnology, Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas, Avda. Agustín Escardino, 7, 46980-Paterna, Valencia, Spain.
| |
Collapse
|
31
|
Boye E, Anda S, Rothe C, Stokke T, Grallert B. Analyzing Schizosaccharomyces pombe DNA Content by Flow Cytometry. Cold Spring Harb Protoc 2016; 2016:2016/6/pdb.prot091280. [PMID: 27250946 DOI: 10.1101/pdb.prot091280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Flow cytometry can be used to measure the DNA content of individual cells. The data are usually presented as DNA histograms that can be used to examine the cells' progression through the cell cycle. Under standard growth conditions, fission yeast cells do not complete cytokinesis until after G1 phase; therefore, DNA histograms show one major peak representing cells in G1 (2×1C DNA) and G2 phase (1×2C DNA). By analysis of the duration of the fluorescence signal as well as the intensity of the DNA-related signal, it is possible to discriminate between cells in M/G1, S, and G2 This protocol describes how to prepare cells for flow cytometry and analyze them. We also describe the application of barcoding for more accurate comparison of samples.
Collapse
Affiliation(s)
- Erik Boye
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Silje Anda
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Christiane Rothe
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Trond Stokke
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
| |
Collapse
|
32
|
Ishimura R, Nagy G, Dotu I, Chuang JH, Ackerman SL. Activation of GCN2 kinase by ribosome stalling links translation elongation with translation initiation. eLife 2016; 5. [PMID: 27085088 PMCID: PMC4917338 DOI: 10.7554/elife.14295] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 04/14/2016] [Indexed: 12/17/2022] Open
Abstract
Ribosome stalling during translation has recently been shown to cause neurodegeneration, yet the signaling pathways triggered by stalled elongation complexes are unknown. To investigate these pathways we analyzed the brain of C57BL/6J-Gtpbp2nmf205-/- mice in which neuronal elongation complexes are stalled at AGA codons due to deficiencies in a tRNAArgUCU tRNA and GTPBP2, a mammalian ribosome rescue factor. Increased levels of phosphorylation of eIF2α (Ser51) were detected prior to neurodegeneration in these mice and transcriptome analysis demonstrated activation of ATF4, a key transcription factor in the integrated stress response (ISR) pathway. Genetic experiments showed that this pathway was activated by the eIF2α kinase, GCN2, in an apparent deacylated tRNA-independent fashion. Further we found that the ISR attenuates neurodegeneration in C57BL/6J-Gtpbp2nmf205-/- mice, underscoring the importance of cellular and stress context on the outcome of activation of this pathway. These results demonstrate the critical interplay between translation elongation and initiation in regulating neuron survival during cellular stress. DOI:http://dx.doi.org/10.7554/eLife.14295.001 Information stored in DNA is used to make proteins in a two-step process. First, the DNA is copied to make molecules of messenger ribonucleic acid (or messenger RNA for short). Next, machines called ribosomes use the messenger RNAs as templates to assemble chains of amino acids – the building blocks of proteins – in a process called translation. Another type of RNA molecule called transfer RNA carries each amino acid to the ribosomes. If a specific transfer RNA is not available for translation at the right time, the ribosome might stall as it moves along the messenger RNA. At this point, the ribosome needs to be restarted or it will fall off the mRNA without finishing the protein. In 2014, a group of researchers reported that certain types of brain cells are very sensitive to ribosome stalling, and tend to die if translation does not continue. A protein called GTPBP2 was shown to play an important role in restarting stalled ribosomes in these cells. Here, Ishimura, Nagy et al. – including some of the researchers from the earlier work – investigated the molecular pathways that ribosome stalling triggers in brain cells using mutant mice that lacked the GTPBP2 protein. The experiments show that ribosome stalling activates an enzyme known as GCN2, which was already known to sense other types of malfunctions in cellular processes. Ishimura, Nagy et al. also show that GCN2 triggers stress responses in the cells by activating a communication system called the ATF4 pathway. This pathway protects the cells from damage, and its absence results in more rapid cell deterioration and death. The next challenges are to understand the exact mechanism by which GCN2 senses stalled ribosomes, and to find out how ribosome stalling causes the death of brain cells. DOI:http://dx.doi.org/10.7554/eLife.14295.002
Collapse
Affiliation(s)
- Ryuta Ishimura
- Howard Hughes Medical Institute, The Jackson Laboratory for Mammalian Genetics, Bar Harbor, United States
| | - Gabor Nagy
- Howard Hughes Medical Institute, The Jackson Laboratory for Mammalian Genetics, Bar Harbor, United States
| | - Ivan Dotu
- Research Programme on Biomedical Informatics, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Jeffrey H Chuang
- The Jackson Laboratory for Genomic Medicine, Farmington, United States.,Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, United States
| | - Susan L Ackerman
- Howard Hughes Medical Institute, The Jackson Laboratory for Mammalian Genetics, Bar Harbor, United States.,Department of Cell and Molecular Medicine, University of California, San Diego School of Medicine, La Jolla, United States.,Section of Neurobiology, University of California, La Jolla, United States
| |
Collapse
|
33
|
Chatty Mitochondria: Keeping Balance in Cellular Protein Homeostasis. Trends Cell Biol 2016; 26:577-586. [PMID: 27004699 DOI: 10.1016/j.tcb.2016.03.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/16/2016] [Accepted: 03/01/2016] [Indexed: 12/25/2022]
Abstract
Mitochondria are multifunctional cellular organelles that host many biochemical pathways including oxidative phosphorylation (OXPHOS). Defective mitochondria pose a threat to cellular homeostasis and compensatory responses exist to curtail the source of stress and/or its consequences. The mitochondrial proteome comprises proteins encoded by the nuclear and mitochondrial genomes. Disturbances in protein homeostasis may originate from mistargeting of nuclear encoded mitochondrial proteins. Defective protein import and accumulation of mistargeted proteins leads to stress that triggers translation alterations and proteasomal activation. These cytosolic pathways are complementary to the mitochondrial unfolded protein response (UPRmt) that aims to increase the capacity of protein quality control mechanisms inside mitochondria. They constitute putative targets for interventions aimed at increasing the fitness, stress resistance, and longevity of cells and organisms.
Collapse
|