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Pei Y, Liu S, Wang L, Chen C, Hu M, Xue Y, Guan D, Xie L, Liao H, Zhou J, Zhang H. Design, Synthesis, and Biological Evaluation of Eukaryotic Initiation Factor 2B (eIF2B) Activators. ChemMedChem 2024; 19:e202300716. [PMID: 38426720 DOI: 10.1002/cmdc.202300716] [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: 12/18/2023] [Revised: 02/29/2024] [Accepted: 02/29/2024] [Indexed: 03/02/2024]
Abstract
The eukaryotic initiation factor 2B (eIF2B) is a key regulator in protein-regulated signaling pathways and is closely related to the function of the central nervous system. Modulating eIF2B could retard the process of neurodegenerative diseases, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and vanishing white matter disease (VWM) et al. Here, we designed and synthesized a series of novel eIF2B activators containing oxadiazole fragments. The activating effects of compounds on eIF2B were investigated through testing the inhibition of ATF4 expression. Of all the targeted compounds, compounds 21 and 29 exhibited potent inhibition on ATF4 expression with IC50 values of 32.43 nM and 47.71 nM, respectively, which were stronger than that of ISRIB (IC50=67.90 nM). ATF4 mRNA assay showed that these two compounds could restore ATF4 mRNA to normal levels in thapsigargin-stimulated HeLa cells. Protein Translation assay showed that both compounds were effective in restoring protein synthesis. Compound potency assay showed that both compounds had similar potency to ISRIB with EC50 values of 5.844 and 37.70 nM. Cytotoxicity assay revealed that compounds 21 and 29 had low toxicity and were worth further investigation.
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Affiliation(s)
- Yifeng Pei
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Sentao Liu
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Lixun Wang
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Chao Chen
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Mengqiu Hu
- New Drug Screening Center, Jiangsu Center for Pharmacodynamics Research and Evaluation, China Pharmaceutical University, Nanjing, China
| | - Yi Xue
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Dezhong Guan
- Department of Medicinal Chemistry, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing, 210009, PR China
| | - Lingfeng Xie
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
| | - Hong Liao
- New Drug Screening Center, Jiangsu Center for Pharmacodynamics Research and Evaluation, China Pharmaceutical University, Nanjing, China
| | - Jinpei Zhou
- Department of Medicinal Chemistry, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing, 210009, PR China
| | - Huibin Zhang
- Center for Drug Discovery, Jiangsu Key Laboratory of Drug Discovery for Metabolic Disease, China Pharmaceutical University, Nanjing, 210009, PR China
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2
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Oudejans E, Witkamp D, Hu-A-Ng GV, Hoogterp L, van Rooijen-van Leeuwen G, Kruijff I, Schonewille P, Lalaoui El Mouttalibi Z, Bartelink I, van der Knaap MS, Abbink TE. Pridopidine subtly ameliorates motor skills in a mouse model for vanishing white matter. Life Sci Alliance 2024; 7:e202302199. [PMID: 38171595 PMCID: PMC10765115 DOI: 10.26508/lsa.202302199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 12/22/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024] Open
Abstract
The leukodystrophy vanishing white matter (VWM) is characterized by chronic and episodic acute neurological deterioration. Curative treatment is presently unavailable. Pathogenic variants in the genes encoding eukaryotic initiation factor 2B (eIF2B) cause VWM and deregulate the integrated stress response (ISR). Previous studies in VWM mouse models showed that several ISR-targeting compounds ameliorate clinical and neuropathological disease hallmarks. It is unclear which ISR components are suitable therapeutic targets. In this study, effects of 4-phenylbutyric acid, tauroursodeoxycholic acid, or pridopidine (PDPD), with ISR targets upstream or downstream of eIF2B, were assessed in VWM mice. In addition, it was found that the composite ataxia score represented motor decline of VWM mice more accurately than the previously used neuroscore. 4-phenylbutyric acid and tauroursodeoxycholic acid did not improve VWM disease hallmarks, whereas PDPD had subtle beneficial effects on motor skills. PDPD alone does not suffice as treatment in VWM mice but may be considered for combination therapy. Also, treatments aimed at ISR components upstream of eIF2B do not improve chronic neurological deterioration; effects on acute episodic decline remain to be investigated.
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Affiliation(s)
- Ellen Oudejans
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Diede Witkamp
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Gino V Hu-A-Ng
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Leoni Hoogterp
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Gemma van Rooijen-van Leeuwen
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Iris Kruijff
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Pleun Schonewille
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Zeinab Lalaoui El Mouttalibi
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Imke Bartelink
- Department of Pharmacy and Clinical Pharmacology, Amsterdam UMC, Location VUmc, Amsterdam, Netherlands
| | - Marjo S van der Knaap
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Truus Em Abbink
- https://ror.org/05grdyy37 Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
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3
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Oliveira MM, Mohamed M, Elder MK, Banegas-Morales K, Mamcarz M, Lu EH, Golhan EAN, Navrange N, Chatterjee S, Abel T, Klann E. The integrated stress response effector GADD34 is repurposed by neurons to promote stimulus-induced translation. Cell Rep 2024; 43:113670. [PMID: 38219147 PMCID: PMC10964249 DOI: 10.1016/j.celrep.2023.113670] [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: 07/04/2023] [Revised: 10/11/2023] [Accepted: 12/26/2023] [Indexed: 01/16/2024] Open
Abstract
Neuronal protein synthesis is required for long-lasting plasticity and long-term memory consolidation. Dephosphorylation of eukaryotic initiation factor 2α is one of the key translational control events that is required to increase de novo protein synthesis that underlies long-lasting plasticity and memory consolidation. Here, we interrogate the molecular pathways of translational control that are triggered by neuronal stimulation with brain-derived neurotrophic factor (BDNF), which results in eukaryotic initiation factor 2α (eIF2α) dephosphorylation and increases in de novo protein synthesis. Primary rodent neurons exposed to BDNF display elevated translation of GADD34, which facilitates eIF2α dephosphorylation and subsequent de novo protein synthesis. Furthermore, GADD34 requires G-actin generated by cofilin to dephosphorylate eIF2α and enhance protein synthesis. Finally, GADD34 is required for BDNF-induced translation of synaptic plasticity-related proteins. Overall, we provide evidence that neurons repurpose GADD34, an effector of the integrated stress response, as an orchestrator of rapid increases in eIF2-dependent translation in response to plasticity-inducing stimuli.
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Affiliation(s)
| | - Muhaned Mohamed
- Center for Neural Science, New York University, New York, NY, USA
| | - Megan K Elder
- Center for Neural Science, New York University, New York, NY, USA
| | | | - Maggie Mamcarz
- Center for Neural Science, New York University, New York, NY, USA
| | - Emily H Lu
- Center for Neural Science, New York University, New York, NY, USA
| | - Ela A N Golhan
- Center for Neural Science, New York University, New York, NY, USA
| | - Nishika Navrange
- Center for Neural Science, New York University, New York, NY, USA
| | - Snehajyoti Chatterjee
- Department of Neuroscience and Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Ted Abel
- Department of Neuroscience and Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Eric Klann
- Center for Neural Science, New York University, New York, NY, USA; NYU Neuroscience Institute, New York University School of Medicine, New York, NY, USA.
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4
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Witkamp D, Oudejans E, Hoogterp L, Hu-A-Ng GV, Glaittli KA, Stevenson TJ, Huijsmans M, Abbink TEM, van der Knaap MS, Bonkowsky JL. Lithium: effects in animal models of vanishing white matter are not promising. Front Neurosci 2024; 18:1275744. [PMID: 38352041 PMCID: PMC10861708 DOI: 10.3389/fnins.2024.1275744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 01/04/2024] [Indexed: 02/16/2024] Open
Abstract
Vanishing white matter (VWM) is a devastating autosomal recessive leukodystrophy, resulting in neurological deterioration and premature death, and without curative treatment. Pathogenic hypomorphic variants in subunits of the eukaryotic initiation factor 2B (eIF2B) cause VWM. eIF2B is required for regulating the integrated stress response (ISR), a physiological response to cellular stress. In patients' central nervous system, reduced eIF2B activity causes deregulation of the ISR. In VWM mouse models, the extent of ISR deregulation correlates with disease severity. One approach to restoring eIF2B activity is by inhibition of GSK3β, a kinase that phosphorylates eIF2B and reduces its activity. Lithium, an inhibitor of GSK3β, is thus expected to stimulate eIF2B activity and ameliorate VWM symptoms. The effects of lithium were tested in zebrafish and mouse VWM models. Lithium improved motor behavior in homozygous eif2b5 mutant zebrafish. In lithium-treated 2b4he2b5ho mutant mice, a paradoxical increase in some ISR transcripts was found. Furthermore, at the dosage tested, lithium induced significant polydipsia in both healthy controls and 2b4he2b5ho mutant mice and did not increase the expression of other markers of lithium efficacy. In conclusion, lithium is not a drug of choice for further development in VWM based on the limited or lack of efficacy and significant side-effect profile.
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Affiliation(s)
- Diede Witkamp
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Ellen Oudejans
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Leoni Hoogterp
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Gino V. Hu-A-Ng
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Kathryn A. Glaittli
- Department of Pediatrics, University of Utah, Salt Lake City, UT, United States
| | - Tamara J. Stevenson
- Department of Pediatrics, University of Utah, Salt Lake City, UT, United States
| | - Marleen Huijsmans
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Truus E. M. Abbink
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Marjo S. van der Knaap
- Child Neurology, Emma Children’s Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, Netherlands
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Joshua L. Bonkowsky
- Department of Pediatrics, University of Utah, Salt Lake City, UT, United States
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5
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Gupta M, Walters B, Katsara O, Granados Blanco K, Geter P, Schneider R. eIF2Bδ blocks the integrated stress response and maintains eIF2B activity and cancer metastasis by overexpression in breast cancer stem cells. Proc Natl Acad Sci U S A 2023; 120:e2207898120. [PMID: 37014850 PMCID: PMC10104532 DOI: 10.1073/pnas.2207898120] [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: 05/06/2022] [Accepted: 03/08/2023] [Indexed: 04/05/2023] Open
Abstract
Breast cancer (BC) metastasis involves cancer stem cells (CSCs) and their regulation by micro-RNAs (miRs), but miR targeting of the translation machinery in CSCs is poorly explored. We therefore screened miR expression levels in a range of BC cell lines, comparing non-CSCs to CSCs, and focused on miRs that target translation and protein synthesis factors. We describe a unique translation regulatory axis enacted by reduced expression of miR-183 in breast CSCs, which we show targets the eIF2Bδ subunit of guanine nucleotide exchange factor eIF2B, a regulator of protein synthesis and the integrated stress response (ISR) pathway. We report that reduced expression of miR-183 greatly increases eIF2Bδ protein levels, preventing strong induction of the ISR and eIF2α phosphorylation, by preferential interaction with P-eIF2α. eIF2Bδ overexpression is essential for BC cell invasion, metastasis, maintenance of metastases, and breast CSC expansion in animal models. Increased expression of eIF2Bδ, a site of action of the drug ISRIB that also prevents ISR signaling, is essential for breast CSC maintenance and metastatic capacity.
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Affiliation(s)
- Malavika Gupta
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
| | - Beth A. Walters
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
| | - Olga Katsara
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
| | - Karol Granados Blanco
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
| | - Phillip A. Geter
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
| | - Robert J. Schneider
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY10016
- New York University Perlmutter Cancer Center, New York University Grossman School of Medicine, New York, NY10016
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6
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Jiang L, Dong R, Xu M, Liu Y, Xu J, Ma Z, Xia T, Gu X. Inhibition of the integrated stress response reverses oxidative stress damage-induced postoperative cognitive dysfunction. Front Cell Neurosci 2022; 16:992869. [PMID: 36212697 PMCID: PMC9534309 DOI: 10.3389/fncel.2022.992869] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 08/29/2022] [Indexed: 11/29/2022] Open
Abstract
Postoperative cognitive dysfunction (POCD) is a common complication following anesthesia and surgery that might lead to a decline in learning and memory. Oxidative stress damage is one of the pathogenic mechanisms underlying POCD. Recent studies had shown that the integrated stress response (ISR) is closely related to oxidative stress. The core response of the ISR is phosphorylation of eIF2α. Various cellular stress stimuli trigger activation of eIF2α kinases, thus causing phosphorylation of eIF2α. ISR is associated with many neurodegenerative diseases; however, the relationship between POCD and ISR has not been defined. In the present study, the tibias in 4-month-old male C57BL/6 mice were fractured under isoflurane anesthesia to establish the POCD animal model. Cognitive function was assessed by fear conditioning tests and the Y-maze from 3 to 14 days post-surgery. Western blot was used to determine the levels of PeIF2α, eIF2α, ATF4, GADD34, CHOP, BDNF, proBDNF, and p-NR2B expression. The levels of reactive oxygen species (ROS), superoxide dismutase (SOD), and malondialdehyde (MDA) were measured to determine oxidative stress in hippocampal tissues. After tibial fracture surgery in mice, the hippocampus had increased levels of PeIF2α, ATF4, GADD34, and CHOP protein, ROS-positive cells, and average fluorescence intensity, SOD activity was decreased, and the MDA level was increased. The ISR inhibitor, ISRIB, reduced the levels of PeIF2α, ATF4, GADD34, and CHOP protein, and alleviated oxidative stress in the hippocampus of POCD mice. Moreover, ISRIB ameliorated cognitive dysfunction in POCD mice. Our findings suggested that targeting ISR may represent an effective approach to combat POCD.
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Affiliation(s)
- Linhao Jiang
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Rui Dong
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Minhui Xu
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Yujia Liu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Jiyan Xu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Zhengliang Ma
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- *Correspondence: Xiaoping Gu Tianjiao Xia Zhengliang Ma
| | - Tianjiao Xia
- Medical School, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
- *Correspondence: Xiaoping Gu Tianjiao Xia Zhengliang Ma
| | - Xiaoping Gu
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical School of Nanjing University, Nanjing, China
- *Correspondence: Xiaoping Gu Tianjiao Xia Zhengliang Ma
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7
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Witkamp D, Oudejans E, Hu-A-Ng GV, Hoogterp L, Krzywańska AM, Žnidaršič M, Marinus K, de Veij Mestdagh CF, Bartelink I, Bugiani M, van der Knaap MS, Abbink TEM. Guanabenz ameliorates disease in vanishing white matter mice in contrast to sephin1. Ann Clin Transl Neurol 2022; 9:1147-1162. [PMID: 35778832 PMCID: PMC9380178 DOI: 10.1002/acn3.51611] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/02/2022] [Accepted: 06/03/2022] [Indexed: 12/28/2022] Open
Abstract
OBJECTIVE Vanishing white matter (VWM) is a leukodystrophy, characterized by stress-sensitive neurological deterioration and premature death. It is currently without curative treatment. It is caused by bi-allelic pathogenic variants in the genes encoding eukaryotic initiation factor 2B (eIF2B). eIF2B is essential for the regulation of the integrated stress response (ISR), a physiological response to cellular stress. Preclinical studies on VWM mouse models revealed that deregulated ISR is key in the pathophysiology of VWM and an effective treatment target. Guanabenz, an α2-adrenergic agonist, attenuates the ISR and has beneficial effects on VWM neuropathology. The current study aimed at elucidating guanabenz's disease-modifying potential and mechanism of action in VWM mice. Sephin1, an ISR-modulating guanabenz analog without α2-adrenergic agonistic properties, was included to separate effects on the ISR from α2-adrenergic effects. METHODS Wild-type and VWM mice were subjected to placebo, guanabenz or sephin1 treatments. Effects on clinical signs, neuropathology, and ISR deregulation were determined. Guanabenz's and sephin1's ISR-modifying effects were tested in cultured cells that expressed or lacked the α2-adrenergic receptor. RESULTS Guanabenz improved clinical signs, neuropathological hallmarks, and ISR regulation in VWM mice, but sephin1 did not. Guanabenz's effects on the ISR in VWM mice were not replicated in cell cultures and the contribution of α2-adrenergic effects on the deregulated ISR could therefore not be assessed. INTERPRETATION Guanabenz proved itself as a viable treatment option for VWM. The exact mechanism through which guanabenz exerts its ameliorating impact on VWM requires further studies. Sephin1 is not simply a guanabenz replacement without α2-adrenergic effects.
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Affiliation(s)
- Diede Witkamp
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Ellen Oudejans
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Gino V Hu-A-Ng
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Leoni Hoogterp
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Aleksandra M Krzywańska
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Milo Žnidaršič
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Kevin Marinus
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Christina F de Veij Mestdagh
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Imke Bartelink
- Department of Pharmacy and Clinical Pharmacology, Amsterdam UMC, Location VUmc, Amsterdam, The Netherlands
| | - Marianna Bugiani
- Department of Pathology, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands
| | - Marjo S van der Knaap
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
| | - Truus E M Abbink
- Child Neurology, Emma Children's Hospital, Amsterdam Leukodystrophy Center, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands
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8
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The role of eIF2 phosphorylation in cell and organismal physiology: new roles for well-known actors. Biochem J 2022; 479:1059-1082. [PMID: 35604373 DOI: 10.1042/bcj20220068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/21/2022] [Accepted: 04/25/2022] [Indexed: 02/06/2023]
Abstract
Control of protein synthesis (mRNA translation) plays key roles in shaping the proteome and in many physiological, including homeostatic, responses. One long-known translational control mechanism involves phosphorylation of initiation factor, eIF2, which is catalysed by any one of four protein kinases, which are generally activated in response to stresses. They form a key arm of the integrated stress response (ISR). Phosphorylated eIF2 inhibits eIF2B (the protein that promotes exchange of eIF2-bound GDP for GTP) and thus impairs general protein synthesis. However, this mechanism actually promotes translation of certain mRNAs by virtue of specific features they possess. Recent work has uncovered many previously unknown features of this regulatory system. Several studies have yielded crucial insights into the structure and control of eIF2, including that eIF2B is regulated by several metabolites. Recent studies also reveal that control of eIF2 and the ISR helps determine organismal lifespan and surprising roles in sensing mitochondrial stresses and in controlling the mammalian target of rapamycin (mTOR). The latter effect involves an unexpected role for one of the eIF2 kinases, HRI. Phosphoproteomic analysis identified new substrates for another eIF2 kinase, Gcn2, which senses the availability of amino acids. Several genetic disorders arise from mutations in genes for eIF2α kinases or eIF2B (i.e. vanishing white matter disease, VWM and microcephaly, epileptic seizures, microcephaly, hypogenitalism, diabetes and obesity, MEHMO). Furthermore, the eIF2-mediated ISR plays roles in cognitive decline associated with Alzheimer's disease. New findings suggest potential therapeutic value in interfering with the ISR in certain settings, including VWM, for example by using compounds that promote eIF2B activity.
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9
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Regulation and function of elF2B in neurological and metabolic disorders. Biosci Rep 2022; 42:231311. [PMID: 35579296 PMCID: PMC9208314 DOI: 10.1042/bsr20211699] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 04/28/2022] [Accepted: 05/12/2022] [Indexed: 11/27/2022] Open
Abstract
Eukaryotic initiation factor 2B, eIF2B is a guanine nucleotide exchange, factor with a central role in coordinating the initiation of translation. During stress and disease, the activity of eIF2B is inhibited via the phosphorylation of its substrate eIF2 (p-eIF2α). A number of different kinases respond to various stresses leading to the phosphorylation of the alpha subunit of eIF2, and collectively this regulation is known as the integrated stress response, ISR. This targeting of eIF2B allows the cell to regulate protein synthesis and reprogramme gene expression to restore homeostasis. Advances within structural biology have furthered our understanding of how eIF2B interacts with eIF2 in both the productive GEF active form and the non-productive eIF2α phosphorylated form. Here, current knowledge of the role of eIF2B in the ISR is discussed within the context of normal and disease states focusing particularly on diseases such as vanishing white matter disease (VWMD) and permanent neonatal diabetes mellitus (PNDM), which are directly linked to mutations in eIF2B. The role of eIF2B in synaptic plasticity and memory formation is also discussed. In addition, the cellular localisation of eIF2B is reviewed and considered along with the role of additional in vivo eIF2B binding factors and protein modifications that may play a role in modulating eIF2B activity during health and disease.
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10
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Boone M, Wang L, Lawrence RE, Frost A, Walter P, Schoof M. A point mutation in the nucleotide exchange factor eIF2B constitutively activates the integrated stress response by allosteric modulation. eLife 2022; 11:e76171. [PMID: 35416150 PMCID: PMC9132573 DOI: 10.7554/elife.76171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 04/11/2022] [Indexed: 11/13/2022] Open
Abstract
In eukaryotic cells, stressors reprogram the cellular proteome by activating the integrated stress response (ISR). In its canonical form, stress-sensing kinases phosphorylate the eukaryotic translation initiation factor eIF2 (eIF2-P), which ultimately leads to reduced levels of ternary complex required for initiation of mRNA translation. Previously we showed that translational control is primarily exerted through a conformational switch in eIF2's nucleotide exchange factor, eIF2B, which shifts from its active A-State conformation to its inhibited I-State conformation upon eIF2-P binding, resulting in reduced nucleotide exchange on eIF2 (Schoof et al. 2021). Here, we show functionally and structurally how a single histidine to aspartate point mutation in eIF2B's β subunit (H160D) mimics the effects of eIF2-P binding by promoting an I-State like conformation, resulting in eIF2-P independent activation of the ISR. These findings corroborate our previously proposed A/I-State model of allosteric ISR regulation.
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Affiliation(s)
- Morgane Boone
- Howard Hughes Medical Institute, University of California at San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Lan Wang
- Howard Hughes Medical Institute, University of California at San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Rosalie E Lawrence
- Howard Hughes Medical Institute, University of California at San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
- Chan Zuckerberg BiohubSan FranciscoUnited States
| | - Peter Walter
- Howard Hughes Medical Institute, University of California at San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
| | - Michael Schoof
- Howard Hughes Medical Institute, University of California at San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California at San FranciscoSan FranciscoUnited States
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11
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Schoof M, Wang L, Cogan JZ, Lawrence RE, Boone M, Wuerth JD, Frost A, Walter P. Viral evasion of the integrated stress response through antagonism of eIF2-P binding to eIF2B. Nat Commun 2021; 12:7103. [PMID: 34876554 PMCID: PMC8651678 DOI: 10.1038/s41467-021-26164-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/17/2021] [Indexed: 01/07/2023] Open
Abstract
Viral infection triggers activation of the integrated stress response (ISR). In response to viral double-stranded RNA (dsRNA), RNA-activated protein kinase (PKR) phosphorylates the translation initiation factor eIF2, converting it from a translation initiator into a potent translation inhibitor and this restricts the synthesis of viral proteins. Phosphorylated eIF2 (eIF2-P) inhibits translation by binding to eIF2's dedicated, heterodecameric nucleotide exchange factor eIF2B and conformationally inactivating it. We show that the NSs protein of Sandfly Fever Sicilian virus (SFSV) allows the virus to evade the ISR. Mechanistically, NSs tightly binds to eIF2B (KD = 30 nM), blocks eIF2-P binding, and rescues eIF2B GEF activity. Cryo-EM structures demonstrate that SFSV NSs and eIF2-P directly compete, with the primary NSs contacts to eIF2Bα mediated by five 'aromatic fingers'. NSs binding preserves eIF2B activity by maintaining eIF2B's conformation in its active A-State.
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Affiliation(s)
- Michael Schoof
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Lan Wang
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - J Zachery Cogan
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Rosalie E Lawrence
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | - Morgane Boone
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
| | | | - Adam Frost
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Peter Walter
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA.
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA.
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12
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Circir A, Koksal Bicakci G, Savas B, Doken DN, Henden ŞO, Can T, Karaca E, Erson-Bensan AE. A C-term truncated EIF2Bγ protein encoded by an intronically polyadenylated isoform introduces unfavorable EIF2Bγ-EIF2γ interactions. Proteins 2021; 90:889-897. [PMID: 34796993 DOI: 10.1002/prot.26284] [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: 08/16/2021] [Revised: 11/01/2021] [Accepted: 11/15/2021] [Indexed: 11/11/2022]
Abstract
Eukaryotic translation initiates upon recruitment of the EIF2-GTP·Met-tRNAi ternary complex (TC) to the ribosomes. EIF2 (α, β, γ subunits) is a GTPase. The GDP to GTP exchange within EIF2 is facilitated by the guanine nucleotide exchange factor EIF2B (α-ε subunits). During stress-induced conditions, phosphorylation of the α-subunit of EIF2 turns EIF2 into an inhibitor of EIF2B. In turn, inhibition of EIF2B decreases TC formation and triggers the internal stress response (ISR), which determines the cell fate. Deregulated ISR has been linked to neurodegenerative disorders and cancer, positioning EIF2B as a promising therapeutic target. Hence, a better understanding of the mechanisms/factors that regulate EIF2B activity is required. Here, combining transcript and protein level analyses, we describe an intronically polyadenylated (IPA) transcript of EIF2B's γ-subunit. We show that the IPA mRNA isoform is translated into a C-terminus truncated protein. Using structural modeling, we predict that the truncated EIF2Bγ protein has unfavorable interactions with EIF2γ, leading to a potential decrease in the stability of the nonproductive EIF2:EIF2B complex. While we discovered and confirmed the IPA mRNA isoform in breast cancer cells, the expression of this isoform is not cancer-specific and is widely present in normal tissues. Overall, our data show that a truncated EIF2Bγ protein co-exists with the canonical protein and is an additional player to regulate the equilibrium between productive and nonproductive states of the EIF2:EIF2B complex. These results may have implications in stress-induced translation control in normal and disease states. Our combinatorial approach demonstrates the need to study noncanonical mRNA and protein isoforms to understand protein interactions and intricate molecular mechanisms.
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Affiliation(s)
- Ayca Circir
- Department of Biological Sciences, Middle East Technical University (METU), Ankara, Turkey
| | - Gozde Koksal Bicakci
- Department of Biological Sciences, Middle East Technical University (METU), Ankara, Turkey
| | - Busra Savas
- Izmir Biomedicine and Genome Center, Balcova, Izmir, Turkey.,Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Balcova, Izmir, Turkey
| | - Didem Naz Doken
- Department of Biological Sciences, Middle East Technical University (METU), Ankara, Turkey
| | - Şevki Onur Henden
- Department of Computer Engineering, Middle East Technical University (METU), Ankara, Turkey
| | - Tolga Can
- Department of Computer Engineering, Middle East Technical University (METU), Ankara, Turkey.,Cancer System Biology Laboratory (CanSyL), Graduate School of Informatics, Middle East Technical University (METU), Ankara, Turkey
| | - Ezgi Karaca
- Izmir Biomedicine and Genome Center, Balcova, Izmir, Turkey.,Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, Balcova, Izmir, Turkey
| | - Ayse Elif Erson-Bensan
- Department of Biological Sciences, Middle East Technical University (METU), Ankara, Turkey.,Cancer System Biology Laboratory (CanSyL), Graduate School of Informatics, Middle East Technical University (METU), Ankara, Turkey
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13
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Hao Q, Heo JM, Nocek BP, Hicks KG, Stoll VS, Remarcik C, Hackett S, LeBon L, Jain R, Eaton D, Rutter J, Wong YL, Sidrauski C. Sugar phosphate activation of the stress sensor eIF2B. Nat Commun 2021; 12:3440. [PMID: 34103529 PMCID: PMC8187479 DOI: 10.1038/s41467-021-23836-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 05/19/2021] [Indexed: 02/07/2023] Open
Abstract
The multi-subunit translation initiation factor eIF2B is a control node for protein synthesis. eIF2B activity is canonically modulated through stress-responsive phosphorylation of its substrate eIF2. The eIF2B regulatory subcomplex is evolutionarily related to sugar-metabolizing enzymes, but the biological relevance of this relationship was unknown. To identify natural ligands that might regulate eIF2B, we conduct unbiased binding- and activity-based screens followed by structural studies. We find that sugar phosphates occupy the ancestral catalytic site in the eIF2Bα subunit, promote eIF2B holoenzyme formation and enhance enzymatic activity towards eIF2. A mutant in the eIF2Bα ligand pocket that causes Vanishing White Matter disease fails to engage and is not stimulated by sugar phosphates. These data underscore the importance of allosteric metabolite modulation for proper eIF2B function. We propose that eIF2B evolved to couple nutrient status via sugar phosphate sensing with the rate of protein synthesis, one of the most energetically costly cellular processes. The activity of translation initiation factor eIF2B is known to be modulated through stress-responsive phosphorylation of its substrate eIF2. Here, the authors uncover the regulation of eIF2B by the binding of sugar phosphates, suggesting a link between nutrient status and the rate of protein synthesis.
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Affiliation(s)
- Qi Hao
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | - Jin-Mi Heo
- Calico Life Sciences LLC, South San Francisco, CA, USA.,Loxo Oncology at Lilly, South San Francisco, CA, USA
| | | | - Kevin G Hicks
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | | | | | - Sean Hackett
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | - Lauren LeBon
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | - Rinku Jain
- Research & Development, AbbVie, North Chicago, IL, USA
| | - Dan Eaton
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | - Jared Rutter
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA.,Howard Hughes Medical Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
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14
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Schoof M, Boone M, Wang L, Lawrence R, Frost A, Walter P. eIF2B conformation and assembly state regulate the integrated stress response. eLife 2021; 10:65703. [PMID: 33688831 PMCID: PMC7990499 DOI: 10.7554/elife.65703] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 03/09/2021] [Indexed: 12/13/2022] Open
Abstract
The integrated stress response (ISR) is activated by phosphorylation of the translation initiation factor eIF2 in response to various stress conditions. Phosphorylated eIF2 (eIF2-P) inhibits eIF2’s nucleotide exchange factor eIF2B, a twofold symmetric heterodecamer assembled from subcomplexes. Here, we monitor and manipulate eIF2B assembly in vitro and in vivo. In the absence of eIF2B’s α-subunit, the ISR is induced because unassembled eIF2B tetramer subcomplexes accumulate in cells. Upon addition of the small-molecule ISR inhibitor ISRIB, eIF2B tetramers assemble into active octamers. Surprisingly, ISRIB inhibits the ISR even in the context of fully assembled eIF2B decamers, revealing allosteric communication between the physically distant eIF2, eIF2-P, and ISRIB binding sites. Cryo-electron microscopy structures suggest a rocking motion in eIF2B that couples these binding sites. eIF2-P binding converts eIF2B decamers into ‘conjoined tetramers’ with diminished substrate binding and enzymatic activity. Canonical eIF2-P-driven ISR activation thus arises due to this change in eIF2B’s conformational state.
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Affiliation(s)
- Michael Schoof
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States
| | - Morgane Boone
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States
| | - Lan Wang
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States
| | - Rosalie Lawrence
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States.,Chan Zuckerberg Biohub, San Francisco, United States
| | - Peter Walter
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, United States
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15
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Slynko I, Nguyen S, Hamilton EMC, Wisse LE, de Esch IJP, de Graaf C, Bruning JB, Proud CG, Abbink TEM, van der Knaap MS. Vanishing white matter: Eukaryotic initiation factor 2B model and the impact of missense mutations. Mol Genet Genomic Med 2021; 9:e1593. [PMID: 33432707 PMCID: PMC8104162 DOI: 10.1002/mgg3.1593] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 12/12/2020] [Accepted: 12/21/2020] [Indexed: 12/21/2022] Open
Abstract
Background Vanishing white matter (VWM) is a leukodystrophy, caused by recessive mutations in eukaryotic initiation factor 2B (eIF2B)‐subunit genes (EIF2B1–EIF2B5); 80% are missense mutations. Clinical severity is highly variable, with a strong, unexplained genotype–phenotype correlation. Materials and Methods With information from a recent natural history study, we severity‐graded 97 missense mutations. Using in silico modeling, we created a new human eIF2B model structure, onto which we mapped the missense mutations. Mutated residues were assessed for location in subunits, eIF2B complex, and functional domains, and for information on biochemical activity. Results Over 50% of mutations have (ultra‐)severe phenotypic effects. About 60% affect the ε‐subunit, containing the catalytic domain, mostly with (ultra‐)severe effects. About 55% affect subunit cores, with variable clinical severity. About 36% affect subunit interfaces, mostly with severe effects. Very few mutations occur on the external eIf2B surface, perhaps because they have minor functional effects and are tolerated. One external surface mutation affects eIF2B‐substrate interaction and is associated with ultra‐severe phenotype. Conclusion Mutations that lead to (ultra‐)severe disease mostly affect amino acids with pivotal roles in complex formation and function of eIF2B. Therapies for VWM are emerging and reliable mutation‐based phenotype prediction is required for propensity score matching for trials and in the future for individualized therapy decisions.
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Affiliation(s)
- Inna Slynko
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Stephanie Nguyen
- Institute for Photonics and Advanced Sensing (IPAS), School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Eline M C Hamilton
- Department of Child Neurology, Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Lisanne E Wisse
- Department of Child Neurology, Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Iwan J P de Esch
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Chris de Graaf
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - John B Bruning
- Institute for Photonics and Advanced Sensing (IPAS), School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Christopher G Proud
- Hopwood Centre for Neurobiology and Lifelong Health Theme, South Australian Health & Medical Research Institute, Adelaide, SA, Australia.,School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Truus E M Abbink
- Department of Child Neurology, Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Marjo S van der Knaap
- Department of Child Neurology, Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, Amsterdam, the Netherlands.,Department of Functional Genomics, Amsterdam Neuroscience, VU University, Amsterdam, the Netherlands
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16
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Norris K, Hodgson RE, Dornelles T, Allen KE, Abell BM, Ashe MP, Campbell SG. Mutational analysis of the alpha subunit of eIF2B provides insights into the role of eIF2B bodies in translational control and VWM disease. J Biol Chem 2021; 296:100207. [PMID: 33334879 PMCID: PMC7948505 DOI: 10.1074/jbc.ra120.014956] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 12/14/2020] [Accepted: 12/17/2020] [Indexed: 12/17/2022] Open
Abstract
Eukaryotic initiation factor 2B (eIF2B) serves as a vital control point within protein synthesis and regulates translation initiation in response to cellular stress. Mutations within eIF2B result in the fatal disease, leukoencephalopathy with vanishing white matter (VWM). Previous biochemical studies on VWM mutations have illustrated that changes in the activity of eIF2B poorly correlate with disease severity. This suggests that there may be additional characteristics of eIF2B contributing to VWM pathogenesis. Here, we investigated whether the localization of eIF2B to eIF2B bodies was integral for function and whether this localization could provide insight into the pathogenesis of VWM. We demonstrate that the regulatory subunit, eIF2Bα, is required for the assembly of eIF2B bodies in yeast and that loss of eIF2B bodies correlates with an inability of cells to regulate eIF2B activity. Mutational analysis of eIF2Bα showed that missense mutations that disrupt the regulation of eIF2B similarly disrupt the assembly of eIF2B bodies. In contrast, when eIF2Bα mutations that impact the catalytic activity of eIF2B were analyzed, eIF2B bodies were absent and instead eIF2B localized to small foci, termed microfoci. Fluorescence recovery after photobleaching analysis highlighted that within these microfoci, eIF2 shuttles more slowly indicating that formation of eIF2B bodies correlates with full eIF2B activity. When eIF2Bα VWM mutations were analyzed, a diverse impact on localization was observed, which did not seem to correlate with eIF2B activity. These findings provide key insights into how the eIF2B body assembles and suggest that the body is a fundamental part of the translational regulation via eIF2α phosphorylation.
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Affiliation(s)
- Karl Norris
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Rachel E Hodgson
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Tawni Dornelles
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - K Elizabeth Allen
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Ben M Abell
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Mark P Ashe
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Susan G Campbell
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
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17
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Nüske E, Marini G, Richter D, Leng W, Bogdanova A, Franzmann TM, Pigino G, Alberti S. Filament formation by the translation factor eIF2B regulates protein synthesis in starved cells. Biol Open 2020; 9:bio046391. [PMID: 32554487 PMCID: PMC7358136 DOI: 10.1242/bio.046391] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/26/2020] [Indexed: 12/11/2022] Open
Abstract
Cells exposed to starvation have to adjust their metabolism to conserve energy and protect themselves. Protein synthesis is one of the major energy-consuming processes and as such has to be tightly controlled. Many mechanistic details about how starved cells regulate the process of protein synthesis are still unknown. Here, we report that the essential translation initiation factor eIF2B forms filaments in starved budding yeast cells. We demonstrate that filamentation is triggered by starvation-induced acidification of the cytosol, which is caused by an influx of protons from the extracellular environment. We show that filament assembly by eIF2B is necessary for rapid and efficient downregulation of translation. Importantly, this mechanism does not require the kinase Gcn2. Furthermore, analysis of site-specific variants suggests that eIF2B assembly results in enzymatically inactive filaments that promote stress survival and fast recovery of cells from starvation. We propose that translation regulation through filament assembly is an efficient mechanism that allows yeast cells to adapt to fluctuating environments.
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Affiliation(s)
- Elisabeth Nüske
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Guendalina Marini
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Doris Richter
- Department of Cellular Biochemistry Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Weihua Leng
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Aliona Bogdanova
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Titus M Franzmann
- Department of Cellular Biochemistry Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Gaia Pigino
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Simon Alberti
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
- Department of Cellular Biochemistry Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
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18
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Costa-Mattioli M, Walter P. The integrated stress response: From mechanism to disease. Science 2020; 368:368/6489/eaat5314. [PMID: 32327570 DOI: 10.1126/science.aat5314] [Citation(s) in RCA: 654] [Impact Index Per Article: 163.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Protein quality control is essential for the proper function of cells and the organisms that they make up. The resulting loss of proteostasis, the processes by which the health of the cell's proteins is monitored and maintained at homeostasis, is associated with a wide range of age-related human diseases. Here, we highlight how the integrated stress response (ISR), a central signaling network that responds to proteostasis defects by tuning protein synthesis rates, impedes the formation of long-term memory. In addition, we address how dysregulated ISR signaling contributes to the pathogenesis of complex diseases, including cognitive disorders, neurodegeneration, cancer, diabetes, and metabolic disorders. The development of tools through which the ISR can be modulated promises to uncover new avenues to diminish pathologies resulting from it for clinical benefit.
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Affiliation(s)
- Mauro Costa-Mattioli
- Department of Neuroscience, Memory and Brain Research Center, Baylor College of Medicine, Houston, TX, USA.
| | - Peter Walter
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA.
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19
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Marintchev A, Ito T. eIF2B and the Integrated Stress Response: A Structural and Mechanistic View. Biochemistry 2020; 59:1299-1308. [PMID: 32200625 DOI: 10.1021/acs.biochem.0c00132] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The eukaryotic translation initiation factor eIF2 is a GTPase, which brings the initiator Met-tRNAi to the ribosome as the eIF2-GTP·Met-tRNAi ternary complex (TC). TC regeneration is catalyzed by the guanine nucleotide exchange factor (GEF) eIF2B. eIF2 phosphorylation by several stress-induced kinases converts it into a competitive inhibitor of eIF2B. Inhibition of eIF2B activity lowers cellular TC concentrations, which in turn triggers the integrated stress response (ISR). Depending on its degree of activation and duration, the ISR protects the cell from the stress or can itself induce apoptosis. ISR dysregulation is a causative factor in the pathology of multiple neurodegenerative disorders, while ISR inhibitors are neuroprotective. The realization that eIF2B is a promising therapeutic target has triggered significant interest in its structure and its mechanisms of action and regulation. Recently, four groups published the cryo-electron microscopy structures of eIF2B with its substrate eIF2 and/or its inhibitor, phosphorylated eIF2 [eIF2(α-P)]. While all three structures of the nonproductive eIF2B·eIF2(α-P) complex are similar to each other, there is a sharp disagreement between the published structures of the productive eIF2B·eIF2 complex. One group reports a structure similar to that of the nonproductive complex, whereas two others observe a vastly different eIF2B·eIF2 complex. Here, we discuss the recent reports on the structure, function, and regulation of eIF2B; the preclinical data on the use of ISR inhibitors for the treatment of neurodegenerative disorders; and how the new structural and biochemical information can inform and influence the use of eIF2B as a therapeutic target.
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Affiliation(s)
- Assen Marintchev
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, United States
| | - Takuhiro Ito
- RIKEN Center for Biosystems Dynamics Research, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
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20
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Anand AA, Walter P. Structural insights into ISRIB, a memory‐enhancing inhibitor of the integrated stress response. FEBS J 2019; 287:239-245. [DOI: 10.1111/febs.15073] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/01/2019] [Accepted: 09/20/2019] [Indexed: 12/29/2022]
Affiliation(s)
- Aditya A. Anand
- Department of Biochemistry and Biophysics University of California at San Francisco San Francisco CA USA
- Howard Hughes Medical Institute San Francisco CA USA
| | - Peter Walter
- Department of Biochemistry and Biophysics University of California at San Francisco San Francisco CA USA
- Howard Hughes Medical Institute San Francisco CA USA
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21
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Proud CG. Phosphorylation and Signal Transduction Pathways in Translational Control. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033050. [PMID: 29959191 DOI: 10.1101/cshperspect.a033050] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protein synthesis, including the translation of specific messenger RNAs (mRNAs), is regulated by extracellular stimuli such as hormones and by the levels of certain nutrients within cells. This control involves several well-understood signaling pathways and protein kinases, which regulate the phosphorylation of proteins that control the translational machinery. These pathways include the mechanistic target of rapamycin complex 1 (mTORC1), its downstream effectors, and the mitogen-activated protein (MAP) kinase (extracellular ligand-regulated kinase [ERK]) signaling pathway. This review describes the regulatory mechanisms that control translation initiation and elongation factors, in particular the effects of phosphorylation on their interactions or activities. It also discusses current knowledge concerning the impact of these control systems on the translation of specific mRNAs or subsets of mRNAs, both in physiological processes and in diseases such as cancer.
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Affiliation(s)
- Christopher G Proud
- Nutrition & Metabolism, South Australian Health & Medical Research Institute, North Terrace, Adelaide SA5000, Australia; and School of Biological Sciences, University of Adelaide, Adelaide SA5000, Australia
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22
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Gordiyenko Y, Llácer JL, Ramakrishnan V. Structural basis for the inhibition of translation through eIF2α phosphorylation. Nat Commun 2019; 10:2640. [PMID: 31201334 PMCID: PMC6572841 DOI: 10.1038/s41467-019-10606-1] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 05/10/2019] [Indexed: 11/29/2022] Open
Abstract
One of the responses to stress by eukaryotic cells is the down-regulation of protein synthesis by phosphorylation of translation initiation factor eIF2. Phosphorylation results in low availability of the eIF2 ternary complex (eIF2-GTP-tRNAi) by affecting the interaction of eIF2 with its GTP-GDP exchange factor eIF2B. We have determined the cryo-EM structure of yeast eIF2B in complex with phosphorylated eIF2 at an overall resolution of 4.2 Å. Two eIF2 molecules bind opposite sides of an eIF2B hetero-decamer through eIF2α-D1, which contains the phosphorylated Ser51. eIF2α-D1 is mainly inserted between the N-terminal helix bundle domains of δ and α subunits of eIF2B. Phosphorylation of Ser51 enhances binding to eIF2B through direct interactions of phosphate groups with residues in eIF2Bα and indirectly by inducing contacts of eIF2α helix 58–63 with eIF2Bδ leading to a competition with Met-tRNAi. During stress, protein synthesis is inhibited through phosphorylation of the initiation factor eIF2 on its alpha subunit and its interaction with eIF2B. Here the authors describe a structure of the yeast eIF2B in complex with its substrate - the GDP-bound phosphorylated eIF2, providing insights into how phosphorylation results in a tighter interaction with eIF2B.
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Affiliation(s)
- Yuliya Gordiyenko
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - José Luis Llácer
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK. .,Instituto de Biomedicina de Valencia del Consejo Superior de Investigaciones Científicas and CIBERER-ISCIII, Valencia, 46010, Spain.
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
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23
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Hodgson RE, Varanda BA, Ashe MP, Allen KE, Campbell SG. Cellular eIF2B subunit localization: implications for the integrated stress response and its control by small molecule drugs. Mol Biol Cell 2019; 30:942-958. [PMID: 30726166 PMCID: PMC6589909 DOI: 10.1091/mbc.e18-08-0538] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Eukaryotic initiation factor 2 (eIF2) is a G protein critical for translation. It is tightly regulated in the integrated stress response (ISR) via phosphorylation of eIF2α and the subsequent control of eukaryotic initiation factor 2B (eIF2B), a multisubunit guanine nucleotide exchange factor. Through studying the localization of eIF2B subunits, we identified cytoplasmic eIF2B bodies in mammalian cells. We highlight a relationship between body size and the eIF2B subunits localizing to them; larger bodies contain all subunits and smaller bodies contain predominantly catalytic subunits. eIF2 localizes to eIF2B bodies and shuttles within these bodies in a manner that correlates with eIF2B activity. On stress, eIF2α-P localizes predominately to larger bodies and results in a decreased shuttling of eIF2. Interestingly, drugs that inhibit the ISR can rescue eIF2 shuttling in a manner correlating to levels of eIF2α-P. In contrast, smaller bodies show increased eIF2 shuttling in response to stress, which is accompanied by the localization of eIF2Bδ to these bodies, suggesting the formation of a novel trimeric complex of eIF2B. This response is mimicked by ISR-inhibiting drugs, providing insight into their potential mechanism of action. This study provides evidence that the composition and function of mammalian eIF2B bodies are regulated by the ISR and the drugs that control it.
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Affiliation(s)
- Rachel E Hodgson
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield S1 1WB, United Kingdom
| | - Beatriz A Varanda
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield S1 1WB, United Kingdom
| | - Mark P Ashe
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - K Elizabeth Allen
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield S1 1WB, United Kingdom
| | - Susan G Campbell
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield S1 1WB, United Kingdom
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24
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Circadian Proteomic Analysis Uncovers Mechanisms of Post-Transcriptional Regulation in Metabolic Pathways. Cell Syst 2018; 7:613-626.e5. [PMID: 30553726 DOI: 10.1016/j.cels.2018.10.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 08/12/2018] [Accepted: 10/29/2018] [Indexed: 12/20/2022]
Abstract
Transcriptional and translational feedback loops in fungi and animals drive circadian rhythms in transcript levels that provide output from the clock, but post-transcriptional mechanisms also contribute. To determine the extent and underlying source of this regulation, we applied newly developed analytical tools to a long-duration, deeply sampled, circadian proteomics time course comprising half of the proteome. We found a quarter of expressed proteins are clock regulated, but >40% of these do not arise from clock-regulated transcripts, and our analysis predicts that these protein rhythms arise from oscillations in translational rates. Our data highlighted the impact of the clock on metabolic regulation, with central carbon metabolism reflecting both transcriptional and post-transcriptional control and opposing metabolic pathways showing peak activities at different times of day. The transcription factor CSP-1 plays a role in this metabolic regulation, contributing to the rhythmicity and phase of clock-regulated proteins.
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25
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Merrick WC, Pavitt GD. Protein Synthesis Initiation in Eukaryotic Cells. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a033092. [PMID: 29735639 DOI: 10.1101/cshperspect.a033092] [Citation(s) in RCA: 197] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review summarizes our current understanding of the major pathway for the initiation phase of protein synthesis in eukaryotic cells, with a focus on recent advances. We describe the major scanning or messenger RNA (mRNA) m7G cap-dependent mechanism, which is a highly coordinated and stepwise regulated process that requires the combined action of at least 12 distinct translation factors with initiator transfer RNA (tRNA), ribosomes, and mRNAs. We limit our review to studies involving either mammalian or budding yeast cells and factors, as these represent the two best-studied experimental systems, and only include a reference to other organisms where particular insight has been gained. We close with a brief description of what we feel are some of the major unknowns in eukaryotic initiation.
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Affiliation(s)
- William C Merrick
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, United Kingdom
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26
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Pavitt GD. Regulation of translation initiation factor eIF2B at the hub of the integrated stress response. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1491. [PMID: 29989343 DOI: 10.1002/wrna.1491] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 05/08/2018] [Accepted: 05/22/2018] [Indexed: 12/29/2022]
Abstract
Phosphorylation of the translation initiation factor eIF2 is one of the most widely used and well-studied mechanisms cells use to respond to diverse cellular stresses. Known as the integrated stress response (ISR), the control pathway uses modulation of protein synthesis to reprogram gene expression and restore homeostasis. Here the current knowledge of the molecular mechanisms of eIF2 activation and its control by phosphorylation at a single-conserved phosphorylation site, serine 51 are discussed with a major focus on the regulatory roles of eIF2B and eIF5 where a current molecular view of ISR control of eIF2B activity is presented. How genetic disorders affect eIF2 or eIF2B is discussed, as are syndromes where excess signaling through the ISR is a component. Finally, studies into the action of recently identified compounds that modulate the ISR in experimental systems are discussed; these suggest that eIF2B is a potential therapeutic target for a wide range of conditions. This article is categorized under: Translation > Translation Regulation.
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Affiliation(s)
- Graham D Pavitt
- Division Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, UK
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27
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Tsai JC, Miller-Vedam LE, Anand AA, Jaishankar P, Nguyen HC, Renslo AR, Frost A, Walter P. Structure of the nucleotide exchange factor eIF2B reveals mechanism of memory-enhancing molecule. Science 2018; 359:359/6383/eaaq0939. [PMID: 29599213 DOI: 10.1126/science.aaq0939] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022]
Abstract
Regulation by the integrated stress response (ISR) converges on the phosphorylation of translation initiation factor eIF2 in response to a variety of stresses. Phosphorylation converts eIF2 from a substrate to a competitive inhibitor of its dedicated guanine nucleotide exchange factor, eIF2B, thereby inhibiting translation. ISRIB, a drug-like eIF2B activator, reverses the effects of eIF2 phosphorylation, and in rodents it enhances cognition and corrects cognitive deficits after brain injury. To determine its mechanism of action, we solved an atomic-resolution structure of ISRIB bound in a deep cleft within decameric human eIF2B by cryo-electron microscopy. Formation of fully active, decameric eIF2B holoenzyme depended on the assembly of two identical tetrameric subcomplexes, and ISRIB promoted this step by cross-bridging a central symmetry interface. Thus, regulation of eIF2B assembly emerges as a rheostat for eIF2B activity that tunes translation during the ISR and that can be further modulated by ISRIB.
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Affiliation(s)
- Jordan C Tsai
- Howard Hughes Medical Institute, University of California, San Francisco, CA, USA.,Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Lakshmi E Miller-Vedam
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA.,Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Aditya A Anand
- Howard Hughes Medical Institute, University of California, San Francisco, CA, USA.,Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Priyadarshini Jaishankar
- Department of Pharmaceutical Chemistry and Small Molecule Discovery Center, University of California, San Francisco, CA, USA
| | - Henry C Nguyen
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA.,Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Adam R Renslo
- Department of Pharmaceutical Chemistry and Small Molecule Discovery Center, University of California, San Francisco, CA, USA
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA. .,Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Peter Walter
- Howard Hughes Medical Institute, University of California, San Francisco, CA, USA. .,Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
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28
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Wong YL, LeBon L, Edalji R, Lim HB, Sun C, Sidrauski C. The small molecule ISRIB rescues the stability and activity of Vanishing White Matter Disease eIF2B mutant complexes. eLife 2018; 7:32733. [PMID: 29489452 PMCID: PMC5829914 DOI: 10.7554/elife.32733] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 02/12/2018] [Indexed: 12/14/2022] Open
Abstract
eIF2B is a dedicated guanine nucleotide exchange factor for eIF2, the GTPase that is essential to initiate mRNA translation. The integrated stress response (ISR) signaling pathway inhibits eIF2B activity, attenuates global protein synthesis and upregulates a set of stress-response proteins. Partial loss-of-function mutations in eIF2B cause a neurodegenerative disorder called Vanishing White Matter Disease (VWMD). Previously, we showed that the small molecule ISRIB is a specific activator of eIF2B (Sidrauski et al., 2015). Here, we report that various VWMD mutations destabilize the decameric eIF2B holoenzyme and impair its enzymatic activity. ISRIB stabilizes VWMD mutant eIF2B in the decameric form and restores the residual catalytic activity to wild-type levels. Moreover, ISRIB blocks activation of the ISR in cells carrying these mutations. As such, ISRIB promises to be an invaluable tool in proof-of-concept studies aiming to ameliorate defects resulting from inappropriate or pathological activation of the ISR.
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Affiliation(s)
- Yao Liang Wong
- Calico Life Sciences LLC, South San Francisco, United States
| | - Lauren LeBon
- Calico Life Sciences LLC, South San Francisco, United States
| | - Rohinton Edalji
- Discovery, Global Pharmaceutical Research and Development, AbbVie, North Chicago, United States
| | - Hock Ben Lim
- Discovery, Global Pharmaceutical Research and Development, AbbVie, North Chicago, United States
| | - Chaohong Sun
- Discovery, Global Pharmaceutical Research and Development, AbbVie, North Chicago, United States
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29
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Bogorad AM, Lin KY, Marintchev A. eIF2B Mechanisms of Action and Regulation: A Thermodynamic View. Biochemistry 2018; 57:1426-1435. [PMID: 29425030 DOI: 10.1021/acs.biochem.7b00957] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Eukaryotic translation initiation factor 2B (eIF2B) is the guanine nucleotide exchange factor of the GTPase eIF2, which brings the initiator Met-tRNAi to the ribosome in the form of the eIF2-GTP·Met-tRNAi ternary complex (TC). The activity of eIF2B is inhibited by phosphorylation of its substrate eIF2 by several stress-induced kinases, which triggers the integrated stress response (ISR). The ISR plays a central role in maintaining homeostasis in the cell under various stress conditions, and its dysregulation is a causative factor in the pathology of a number of neurodegenerative disorders. Over the past three decades, virtually every aspect of eIF2B function has been the subject of uncertainty or controversy: from the catalytic mechanism of nucleotide exchange, to whether eIF2B only catalyzes nucleotide exchange on eIF2 or also promotes binding of Met-tRNAi to eIF2-GTP to form the TC. Here, we provide the first complete thermodynamic analysis of the process of recycling of eIF2-GDP to the TC. The available evidence leads to the conclusion that eIF2 is channeled from the ribosome (as an eIF5·eIF2-GDP complex) to eIF2B, converted by eIF2B to the TC, which is then channeled back to eIF5 and the ribosome. The system has evolved to be regulated by multiple factors, including post-translational modifications of eIF2, eIF2B, and eIF5, as well as directly by the energy balance in the cell, through the GTP:GDP ratio.
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Affiliation(s)
- Andrew M Bogorad
- Department of Physiology & Biophysics , Boston University School of Medicine , Boston , Massachusetts 02118 , United States
| | - Kai Ying Lin
- Department of Physiology & Biophysics , Boston University School of Medicine , Boston , Massachusetts 02118 , United States
| | - Assen Marintchev
- Department of Physiology & Biophysics , Boston University School of Medicine , Boston , Massachusetts 02118 , United States
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30
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A presumed homologue of the regulatory subunits of eIF2B functions as ribose-1,5-bisphosphate isomerase in Pyrococcus horikoshii OT3. Sci Rep 2018; 8:1891. [PMID: 29382938 PMCID: PMC5789824 DOI: 10.1038/s41598-018-20418-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/17/2018] [Indexed: 02/06/2023] Open
Abstract
The homologues of the regulatory subunits of eukaryotic translation initiation factor 2B (eIF2B) are assumed to be present in archaea. Likewise, an ORF, PH0208 in Pyrococcus horikoshii OT3 have been proposed to encode one of the homologues of regulatory subunits of eIF2B. However, PH0208 protein also shares sequence similarity with a functionally non-related enzyme, ribose-1,5-bisphosphate isomerase (R15Pi), involved in conversion of ribose-1,5-bisphosphate (R15P) to ribulose-1,5-bisphosphate (RuBP) in an AMP-dependent manner. Herein, we have determined the crystal structure of PH0208 protein in order to decipher its true function. Although structurally similar to the regulatory subunits of eIF2B, the ability to bind R15P and RuBP suggests that PH0208 would function as R15Pi. Additionally, this study for the first time reports the binding sites of AMP and GMP in R15Pi. The AMP binding site in PH0208 protein clarified the role of AMP in providing structural stability to R15Pi. The binding of GMP to the 'AMP binding site' in addition to its own binding site indicates that GMP might also execute a similar function, though with less specificity. Furthermore, we have utilized the resemblance between PH0208 and the regulatory subunits of eIF2B to propose a model for the regulatory mechanism of eIF2B in eukaryotes.
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31
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Bogorad AM, Lin KY, Marintchev A. Novel mechanisms of eIF2B action and regulation by eIF2α phosphorylation. Nucleic Acids Res 2017; 45:11962-11979. [PMID: 29036434 PMCID: PMC5714165 DOI: 10.1093/nar/gkx845] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 09/13/2017] [Indexed: 12/15/2022] Open
Abstract
Eukaryotic translation initiation factor 2 (eIF2) is a heterotrimeric GTPase, which plays a critical role in protein synthesis regulation. eIF2-GTP binds Met-tRNAi to form the eIF2-GTP•Met-tRNAi ternary complex (TC), which is recruited to the 40S ribosomal subunit. Following GTP hydrolysis, eIF2-GDP is recycled back to TC by its guanine nucleotide exchange factor (GEF), eIF2B. Phosphorylation of the eIF2α subunit in response to various cellular stresses converts eIF2 into a competitive inhibitor of eIF2B, which triggers the integrated stress response (ISR). Dysregulation of eIF2B activity is associated with a number of pathologies, including neurodegenerative diseases, metabolic disorders, and cancer. However, despite decades of research, the underlying molecular mechanisms of eIF2B action and regulation remain unknown. Here we employ a combination of NMR, fluorescence spectroscopy, site-directed mutagenesis, and thermodynamics to elucidate the mechanisms of eIF2B action and its regulation by phosphorylation of the substrate eIF2. We present: (i) a novel mechanism for the inhibition of eIF2B activity, whereby eIF2α phosphorylation destabilizes an autoregulatory intramolecular interaction within eIF2α; and (ii) the first structural model for the complex of eIF2B with its substrate, eIF2-GDP, reaction intermediates, apo-eIF2 and eIF2-GTP, and product, TC, with direct implications for the eIF2B catalytic mechanism.
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Affiliation(s)
- Andrew M Bogorad
- Boston University School of Medicine, Department of Physiology & Biophysics, Boston, MA 02118, USA
| | - Kai Ying Lin
- Boston University School of Medicine, Department of Physiology & Biophysics, Boston, MA 02118, USA
| | - Assen Marintchev
- Boston University School of Medicine, Department of Physiology & Biophysics, Boston, MA 02118, USA
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32
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Liko I, Allison TM, Hopper JT, Robinson CV. Mass spectrometry guided structural biology. Curr Opin Struct Biol 2016; 40:136-144. [PMID: 27721169 DOI: 10.1016/j.sbi.2016.09.008] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 08/08/2016] [Accepted: 09/14/2016] [Indexed: 10/20/2022]
Abstract
With the convergence of breakthroughs in structural biology, specifically breaking the resolution barriers in cryo-electron microscopy and with continuing developments in crystallography, novel interfaces with other biophysical methods are emerging. Here we consider how mass spectrometry can inform these techniques by providing unambiguous definition of subunit stoichiometry. Moreover recent developments that increase mass spectral resolution enable molecular details to be ascribed to unassigned density within high-resolution maps of membrane and soluble protein complexes. Importantly we also show how developments in mass spectrometry can define optimal solution conditions to guide downstream structure determination, particularly of challenging biomolecules that refuse to crystallise.
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Affiliation(s)
- Idlir Liko
- Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Timothy M Allison
- Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Jonathan Ts Hopper
- Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Carol V Robinson
- Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom.
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33
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Kashiwagi K, Ito T, Yokoyama S. Crystal structure of eIF2B and insights into eIF2-eIF2B interactions. FEBS J 2016; 284:868-874. [PMID: 27627185 DOI: 10.1111/febs.13896] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 08/31/2016] [Accepted: 09/12/2016] [Indexed: 12/20/2022]
Abstract
Eukaryotic translation initiation factor 2B (eIF2B), a heterodecameric complex of two sets of the α, β, γ, δ, and ε subunits, is the guanine nucleotide exchange factor (GEF) specific for eIF2, a heterotrimeric G protein consisting of the α, β, and γ subunits. The eIF2 protein binds GTP on the γ subunits and delivers an initiator methionyl-tRNA (Met-tRNAiMet ) to the ribosome. The GEF activity of eIF2B is inhibited by stress-induced phosphorylation of Ser51 in the α subunit of eIF2, which leads to lower amounts of active eIF2 and a limited quantity of Met-tRNAiMet for the ribosome, resulting in global repression of translation. However, the structural mechanism of the GEF activity inhibition remained enigmatic, and therefore the three-dimensional structure of the entire eIF2B molecule had been awaited. Recently, we determined the crystal structure of Schizosaccharomyces pombe eIF2B. In this Structural Snapshot, we present the structural features of eIF2B and the mechanism underlying the GEF activity inhibition by the phosphorylation of eIF2α, elucidated from structure-based in vitro analyses.
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Affiliation(s)
- Kazuhiro Kashiwagi
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama, Japan
| | - Takuhiro Ito
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama, Japan
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34
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eIF2B: recent structural and functional insights into a key regulator of translation. Biochem Soc Trans 2016; 43:1234-40. [PMID: 26614666 DOI: 10.1042/bst20150164] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The eukaryotic translation initiation factor (eIF) eIF2B is a key regulator of mRNA translation, being the guanine nt exchange factor (GEF) responsible for the recycling of the heterotrimeric G-protein, eIF2, which is required to allow translation initiation to occur. Unusually for a GEF, eIF2B is a multi-subunit protein, comprising five different subunits termed α through ε in order of increasing size. eIF2B is subject to tight regulation in the cell and may also serve additional functions. Here we review recent insights into the subunit organization of the mammalian eIF2B complex, gained both from structural studies of the complex and from studies of mutations of eIF2B that result in the neurological disorder leukoencephalopathy with vanishing white matter (VWM). We will also discuss recent data from yeast demonstrating a novel function of the eIF2B complex key for translational regulation.
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Kashiwagi K, Shigeta T, Imataka H, Ito T, Yokoyama S. Expression, purification, and crystallization of Schizosaccharomyces pombe eIF2B. ACTA ACUST UNITED AC 2016; 17:33-8. [PMID: 27023709 PMCID: PMC4833825 DOI: 10.1007/s10969-016-9203-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 03/16/2016] [Indexed: 11/24/2022]
Abstract
Tight control of protein synthesis is necessary for cells to respond and adapt to environmental changes rapidly. Eukaryotic translation initiation factor (eIF) 2B, the guanine nucleotide exchange factor for eIF2, is a key target of translation control at the initiation step. The nucleotide exchange activity of eIF2B is inhibited by the stress-induced phosphorylation of eIF2. As a result, the level of active GTP-bound eIF2 is lowered, and protein synthesis is attenuated. eIF2B is a large multi-subunit complex composed of five different subunits, and all five of the subunits are the gene products responsible for the neurodegenerative disease, leukoencephalopathy with vanishing white matter. However, the overall structure of eIF2B has remained unresolved, due to the difficulty in preparing a sufficient amount of the eIF2B complex. To overcome this problem, we established the recombinant expression and purification method for eIF2B from the fission yeast Schizosaccharomyces pombe. All five of the eIF2B subunits were co-expressed and reconstructed into the complex in Escherichia coli cells. The complex was successfully purified with a high yield. This recombinant eIF2B complex contains each subunit in an equimolar ratio, and the size exclusion chromatography analysis suggests it forms a heterodecamer, consistent with recent reports. This eIF2B increased protein synthesis in the reconstituted in vitro human translation system. In addition, disease-linked mutations led to subunit dissociation. Furthermore, we crystallized this functional recombinant eIF2B, and the crystals diffracted to 3.0 Å resolution.
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Affiliation(s)
- Kazuhiro Kashiwagi
- Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.,RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan.,RIKEN Center for Life Science Technologies, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan
| | - Tomoaki Shigeta
- Graduate School of Engineering, University of Hyogo, Himeji, 671-2280, Japan
| | - Hiroaki Imataka
- Graduate School of Engineering, University of Hyogo, Himeji, 671-2280, Japan
| | - Takuhiro Ito
- Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. .,RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan. .,RIKEN Center for Life Science Technologies, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan.
| | - Shigeyuki Yokoyama
- Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. .,RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan. .,RIKEN Structural Biology Laboratory, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan.
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36
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Crystal structure of eukaryotic translation initiation factor 2B. Nature 2016; 531:122-5. [DOI: 10.1038/nature16991] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 01/12/2016] [Indexed: 12/15/2022]
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Hearn BR, Jaishankar P, Sidrauski C, Tsai JC, Vedantham P, Fontaine SD, Walter P, Renslo AR. Structure-Activity Studies of Bis-O-Arylglycolamides: Inhibitors of the Integrated Stress Response. ChemMedChem 2016; 11:870-80. [DOI: 10.1002/cmdc.201500483] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 12/15/2015] [Indexed: 12/31/2022]
Affiliation(s)
- Brian R. Hearn
- Department of Pharmaceutical Chemistry and; Small Molecule Discovery Center; University of California; San Francisco CA 94158 USA
| | - Priyadarshini Jaishankar
- Department of Pharmaceutical Chemistry and; Small Molecule Discovery Center; University of California; San Francisco CA 94158 USA
| | - Carmela Sidrauski
- Department of Biochemistry and Biophysics; Howard Hughes Medical Institute; University of California; San Francisco CA 94158 USA
| | - Jordan C. Tsai
- Department of Biochemistry and Biophysics; Howard Hughes Medical Institute; University of California; San Francisco CA 94158 USA
| | - Punitha Vedantham
- Department of Pharmaceutical Chemistry and; Small Molecule Discovery Center; University of California; San Francisco CA 94158 USA
| | - Shaun D. Fontaine
- Department of Pharmaceutical Chemistry and; Small Molecule Discovery Center; University of California; San Francisco CA 94158 USA
| | - Peter Walter
- Department of Biochemistry and Biophysics; Howard Hughes Medical Institute; University of California; San Francisco CA 94158 USA
| | - Adam R. Renslo
- Department of Pharmaceutical Chemistry and; Small Molecule Discovery Center; University of California; San Francisco CA 94158 USA
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38
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Stoichiometry of the eIF2B complex is maintained by mutual stabilization of subunits. Biochem J 2015; 473:571-80. [PMID: 26614765 DOI: 10.1042/bj20150828] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/26/2015] [Indexed: 12/30/2022]
Abstract
The eukaryotic translation initiation factor eIF2B is a multi-subunit complex with a crucial role in the regulation of global protein synthesis in the cell. The complex comprises five subunits, termed α through ε in order of increasing size, arranged as a heterodecamer with two copies of each subunit. Regulation of the co-stoichiometric expression of the eIF2B subunits is crucial for the proper function and regulation of the eIF2B complex in cells. We have investigated the control of stoichiometric eIF2B complexes through mutual stabilization of eIF2B subunits. Our data show that the stable expression of the catalytic eIF2Bε subunit in human cells requires co-expression of eIF2Bγ. Similarly, stable expression of eIF2Bδ requires both eIF2Bβ and eIF2Bγ+ε. The expression of these subunits decreases despite there being no change in either the levels or the translation of their mRNAs. Instead, these subunits are targeted for degradation by the ubiquitin-proteasome system. The data allow us to propose a model for the formation of stoichiometric eIF2B complexes which can ensure their stoichiometric incorporation into the holocomplex.
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Schmidt C, Beilsten-Edmands V, Robinson CV. Insights into Eukaryotic Translation Initiation from Mass Spectrometry of Macromolecular Protein Assemblies. J Mol Biol 2015; 428:344-356. [PMID: 26497764 DOI: 10.1016/j.jmb.2015.10.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/28/2015] [Accepted: 10/14/2015] [Indexed: 02/05/2023]
Abstract
Translation initiation in eukaryotes requires the interplay of at least 10 initiation factors that interact at the different steps of this phase of gene expression. The interactions of initiation factors and related proteins are in general controlled by phosphorylation, which serves as a regulatory switch to turn protein translation on or off. The structures of initiation factors and a complete description of their post-translational modification (PTM) status are therefore required in order to fully understand these processes. In recent years, mass spectrometry has contributed considerably to provide this information and nowadays is proving to be indispensable when studying dynamic heterogeneous protein complexes such as the eukaryotic initiation factors. Herein, we highlight mass spectrometric approaches commonly applied to identify interacting subunits and their PTMs and the structural techniques that allow the architecture of protein complexes to be assessed. We present recent structural investigations of initiation factors and their interactions with other factors and with ribosomes and we assess the models generated. These models allow us to locate PTMs within initiation factor complexes and to highlight possible roles for phosphorylation sites in regulating interaction interfaces.
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Affiliation(s)
- Carla Schmidt
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Victoria Beilsten-Edmands
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
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40
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Kuhle B, Eulig NK, Ficner R. Architecture of the eIF2B regulatory subcomplex and its implications for the regulation of guanine nucleotide exchange on eIF2. Nucleic Acids Res 2015; 43:9994-10014. [PMID: 26384431 PMCID: PMC4787765 DOI: 10.1093/nar/gkv930] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 09/07/2015] [Indexed: 11/14/2022] Open
Abstract
Eukaryal translation initiation factor 2B (eIF2B) acts as guanine nucleotide exchange factor (GEF) for eIF2 and forms a central target for pathways regulating global protein synthesis. eIF2B consists of five non-identical subunits (α-ϵ), which assemble into a catalytic subcomplex (γ, ϵ) responsible for the GEF activity, and a regulatory subcomplex (α, β, δ) which regulates the GEF activity under stress conditions. Here, we provide new structural and functional insight into the regulatory subcomplex of eIF2B (eIF2B(RSC)). We report the crystal structures of eIF2Bβ and eIF2Bδ from Chaetomium thermophilum as well as the crystal structure of their tetrameric eIF2B(βδ)2 complex. Combined with mutational and biochemical data, we show that eIF2B(RSC) exists as a hexamer in solution, consisting of two eIF2Bβδ heterodimers and one eIF2Bα2 homodimer, which is homologous to homohexameric ribose 1,5-bisphosphate isomerases. This homology is further substantiated by the finding that eIF2Bα specifically binds AMP and GMP as ligands. Based on our data, we propose a model for eIF2B(RSC) and its interactions with eIF2 that is consistent with previous biochemical and genetic data and provides a framework to better understand eIF2B function, the molecular basis for Gcn(-), Gcd(-) and VWM/CACH mutations and the evolutionary history of the eIF2B complex.
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Affiliation(s)
- Bernhard Kuhle
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Nora K Eulig
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
| | - Ralf Ficner
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
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41
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Wortham NC, Proud CG. Biochemical effects of mutations in the gene encoding the alpha subunit of eukaryotic initiation factor (eIF) 2B associated with Vanishing White Matter disease. BMC MEDICAL GENETICS 2015; 16:64. [PMID: 26285592 PMCID: PMC4593227 DOI: 10.1186/s12881-015-0204-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/14/2015] [Indexed: 11/10/2022]
Abstract
BACKGROUND Leukoencephalopathy with Vanishing White Matter (VWM) is an autosomal recessive disorder caused by germline mutations in the genes EIF2B1-5, which encode the 5 subunits of the eukaryotic translation initiation factor eIF2B. To date, analysis of the biochemical effects of mutations in the EIF2B2-5 genes has been carried out, but no study has been performed on mutations in the EIF2B1 gene. This gene encodes eIF2Bα, the smallest subunit in eIF2B which has an important role in both the structure and regulation of the eIF2B complex. METHODS eIF2B subunits were overexpressed in HEK293 cells and isolated from the resulting cell lysates by affinity chromatography. Formation of the eIF2B complex and binding of its substrate, eIF2, was assessed by western blot. Assays of the guanine nucleotide exchange (GEF) activity were also carried out. RESULTS Of the 5 eIF2Bα mutations studied, we found 3 that showed loss or reduction of binding of eIF2Bα to the rest of the complex, one with increased GEF activity, and one where no effects on activity or complex formation were observed. CONCLUSIONS This is the first study on eIF2Bα VWM mutations. We show that some mutations cause expected decreases in GEF activity or complex formation, similar to a majority of observed VWM mutations. However, we also observe some unexpected changes which hint at other effects of these mutations on as yet undescribed functions of eIF2B.
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Affiliation(s)
- Noel C Wortham
- Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Highfield Campus, Southampton, SO17 1BJ, UK.
| | - Christopher G Proud
- Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Highfield Campus, Southampton, SO17 1BJ, UK. .,South Australian Health and Medical Research Institute, PO Box 11060, SA5001, Adelaide, Australia.
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42
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eIF2 interactions with initiator tRNA and eIF2B are regulated by post-translational modifications and conformational dynamics. Cell Discov 2015; 1:15020. [PMID: 27462419 PMCID: PMC4860841 DOI: 10.1038/celldisc.2015.20] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 06/12/2015] [Indexed: 12/18/2022] Open
Abstract
Translation of messenger RNA (mRNA) into proteins is key to eukaryotic gene expression and begins when initiation factor-2 (eIF2) delivers methionyl initiator tRNA (Met-tRNAiMet) to ribosomes. This first step is controlled by eIF2B mediating guanine nucleotide exchange on eIF2. We isolated eIF2 from yeast and used mass spectrometry to study the intact complex, and found that eIF2β is the most labile of the three subunits (eIF2α/β/γ). We then compared conformational dynamics of the ternary complex eIF2:GTP:Met-tRNAiMet with apo eIF2 using comparative chemical cross-linking. Results revealed high conformational dynamics for eIF2α in apo eIF2 while in the ternary complex all three subunits are constrained. Novel post-translational modifications identified here in both eIF2 and eIF2B were combined with established sites, and located within protein sequences and homology models. We found clustering at subunit interfaces and highly phosphorylated unstructured regions, at the N-terminus of eIF2β, and also between the eIF2Bε core and catalytic domains. We propose that modifications of these unstructured regions have a key role in regulating interactions between eIF2 and eIF2B, as well as other eIFs.
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43
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Jennings MD, Pavitt GD. A new function and complexity for protein translation initiation factor eIF2B. Cell Cycle 2015; 13:2660-5. [PMID: 25486352 DOI: 10.4161/15384101.2014.948797] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
eIF2B is a multisubunit protein that is critical for protein synthesis initiation and its control. It is a guanine nucleotide exchange factor (GEF) for its GTP-binding protein partner eIF2. eIF2 binds initiator tRNA to ribosomes and promotes mRNA AUG codon recognition. eIF2B is critical for regulation of protein synthesis via a conserved mechanism of phosphorylation of eIF2, which converts eIF2 from a substrate to an inhibitor of eIF2B GEF. In addition, inherited mutations affecting eIF2B subunits cause the fatal disorder leukoencephalopathy with Vanishing White Matter (VWM), also called Childhood Ataxia with Central nervous system Hypomyelination (CACH). Here we review findings which reveal that eIF2B is a decameric protein and also define a new function for the eIF2B. Our results demonstrate that the eIF2Bγ subunit is required for eIF2B to gain access to eIF2•GDP. Specifically it displaces a third translation factor eIF5 (a dual function GAP and GDI) from eIF2•GDP/eIF5 complexes. Thus eIF2B is a GDI displacement factor (or GDF) in addition to its role as a GEF, prompting the redrawing of the eIF2 cycling pathway to incorporate the new steps. In structural studies using mass spectrometry and cross-linking it is shown that eIF2B is a dimer of pentamers and so is twice as large as previously thought. A binding site for GTP on eIF2B was also found, raising further questions concerning the mechanism of nucleotide exchange. The implications of these findings for eIF2B function and for VWM/CACH disease are discussed.
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Affiliation(s)
- Martin D Jennings
- a Faculty of Life Sciences ; The University of Manchester ; Manchester , UK
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44
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Abstract
A drug that affects memory targets a constituent of a cellular stress response mechanism
[Also see Report by
Sekine
et al.
]
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Affiliation(s)
- Alan G. Hinnebusch
- Laboratory of Gene Regulation and Development, National Institutes of Health, Bethesda, MD, USA
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45
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Sekine Y, Zyryanova A, Crespillo-Casado A, Fischer PM, Harding HP, Ron D. Stress responses. Mutations in a translation initiation factor identify the target of a memory-enhancing compound. Science 2015; 348:1027-30. [PMID: 25858979 PMCID: PMC4538794 DOI: 10.1126/science.aaa6986] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/25/2015] [Indexed: 12/20/2022]
Abstract
The integrated stress response (ISR) modulates messenger RNA translation to regulate the mammalian unfolded protein response (UPR), immunity, and memory formation. A chemical ISR inhibitor, ISRIB, enhances cognitive function and modulates the UPR in vivo. To explore mechanisms involved in ISRIB action, we screened cultured mammalian cells for somatic mutations that reversed its effect on the ISR. Clustered missense mutations were found at the amino-terminal portion of the delta subunit of guanine nucleotide exchange factor (GEF) eIF2B. When reintroduced by CRISPR-Cas9 gene editing of wild-type cells, these mutations reversed both ISRIB-mediated inhibition of the ISR and its stimulatory effect on eIF2B GEF activity toward its substrate, the translation initiation factor eIF2, in vitro. Thus, ISRIB targets an interaction between eIF2 and eIF2B that lies at the core of the ISR.
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Affiliation(s)
- Yusuke Sekine
- University of Cambridge, Cambridge Institute for Medical Research (CIMR), the Wellcome Trust MRC Institute of Metabolic Science and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0XY, UK.
| | - Alisa Zyryanova
- University of Cambridge, Cambridge Institute for Medical Research (CIMR), the Wellcome Trust MRC Institute of Metabolic Science and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0XY, UK
| | - Ana Crespillo-Casado
- University of Cambridge, Cambridge Institute for Medical Research (CIMR), the Wellcome Trust MRC Institute of Metabolic Science and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0XY, UK
| | - Peter M Fischer
- Division of Medicinal Chemistry and Structural Biology, School of Pharmacy, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Heather P Harding
- University of Cambridge, Cambridge Institute for Medical Research (CIMR), the Wellcome Trust MRC Institute of Metabolic Science and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0XY, UK
| | - David Ron
- University of Cambridge, Cambridge Institute for Medical Research (CIMR), the Wellcome Trust MRC Institute of Metabolic Science and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0XY, UK.
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46
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Dyachenko A, Wang G, Belov M, Makarov A, de Jong RN, van den Bremer ETJ, Parren PWHI, Heck AJR. Tandem Native Mass-Spectrometry on Antibody–Drug Conjugates and Submillion Da Antibody–Antigen Protein Assemblies on an Orbitrap EMR Equipped with a High-Mass Quadrupole Mass Selector. Anal Chem 2015; 87:6095-102. [DOI: 10.1021/acs.analchem.5b00788] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Andrey Dyachenko
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan
8, 3584 CH, Utrecht, The Netherlands
| | - Guanbo Wang
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan
8, 3584 CH, Utrecht, The Netherlands
| | - Mike Belov
- Thermo Fisher Scientific, Bremen, Germany
| | - Alexander Makarov
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH, Utrecht, The Netherlands
- Thermo Fisher Scientific, Bremen, Germany
| | | | | | - Paul W. H. I. Parren
- Genmab, Utrecht, The Netherlands
- Department
of Immunohematology and Blood Transfusion, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands
| | - Albert J. R. Heck
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan
8, 3584 CH, Utrecht, The Netherlands
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Chorev DS, Ben-Nissan G, Sharon M. Exposing the subunit diversity and modularity of protein complexes by structural mass spectrometry approaches. Proteomics 2015; 15:2777-91. [PMID: 25727951 DOI: 10.1002/pmic.201400517] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 01/08/2015] [Accepted: 02/24/2015] [Indexed: 12/11/2022]
Abstract
Although the number of protein-encoding genes in the human genome is only about 20 000 not far from the amount found in the nematode worm genome, the number of proteins that are translated from these sequences is larger by several orders of magnitude. A number of mechanisms have evolved to enable this diversity. For example, genes can be alternatively spliced to create multiple transcripts; they may also be translated from different alternative initiation sites. After translation, hundreds of chemical modifications can be introduced in proteins, altering their chemical properties, folding, stability, and activity. The complexity is then further enhanced by the various combinations that are generated from the assembly of different subunit variants into protein complexes. This, in turn, confers structural and functional flexibility, and endows the cell with the ability to adapt to various environmental conditions. Therefore, exposing the variability of protein complexes is an important step toward understanding their biological functions. Revealing this enormous diversity, however, is not a simple task. In this review, we will focus on the array of MS-based strategies that are capable of performing this mission. We will also discuss the challenges that lie ahead, and the future directions toward which the field might be heading.
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Affiliation(s)
- Dror S Chorev
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Gili Ben-Nissan
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Michal Sharon
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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48
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Sidrauski C, Tsai JC, Kampmann M, Hearn BR, Vedantham P, Jaishankar P, Sokabe M, Mendez AS, Newton BW, Tang EL, Verschueren E, Johnson JR, Krogan NJ, Fraser CS, Weissman JS, Renslo AR, Walter P. Pharmacological dimerization and activation of the exchange factor eIF2B antagonizes the integrated stress response. eLife 2015; 4:e07314. [PMID: 25875391 PMCID: PMC4426669 DOI: 10.7554/elife.07314] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/13/2015] [Indexed: 12/18/2022] Open
Abstract
The general translation initiation factor eIF2 is a major translational control point. Multiple signaling pathways in the integrated stress response phosphorylate eIF2 serine-51, inhibiting nucleotide exchange by eIF2B. ISRIB, a potent drug-like small molecule, renders cells insensitive to eIF2α phosphorylation and enhances cognitive function in rodents by blocking long-term depression. ISRIB was identified in a phenotypic cell-based screen, and its mechanism of action remained unknown. We now report that ISRIB is an activator of eIF2B. Our reporter-based shRNA screen revealed an eIF2B requirement for ISRIB activity. Our results define ISRIB as a symmetric molecule, show ISRIB-mediated stabilization of activated eIF2B dimers, and suggest that eIF2B4 (δ-subunit) contributes to the ISRIB binding site. We also developed new ISRIB analogs, improving its EC50 to 600 pM in cell culture. By modulating eIF2B function, ISRIB promises to be an invaluable tool in proof-of-principle studies aiming to ameliorate cognitive defects resulting from neurodegenerative diseases.
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Affiliation(s)
- Carmela Sidrauski
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Jordan C Tsai
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Martin Kampmann
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Brian R Hearn
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Punitha Vedantham
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Priyadarshini Jaishankar
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, United States
| | - Aaron S Mendez
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Billy W Newton
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Edward L Tang
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Erik Verschueren
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Jeffrey R Johnson
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Nevan J Krogan
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, United States
| | - Jonathan S Weissman
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Adam R Renslo
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
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49
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Gordiyenko Y, Schmidt C, Jennings MD, Matak-Vinkovic D, Pavitt GD, Robinson CV. eIF2B is a decameric guanine nucleotide exchange factor with a γ2ε2 tetrameric core. Nat Commun 2014; 5:3902. [PMID: 24852487 PMCID: PMC4046112 DOI: 10.1038/ncomms4902] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 04/15/2014] [Indexed: 01/21/2023] Open
Abstract
eIF2B facilitates and controls protein synthesis in eukaryotes by mediating guanine nucleotide exchange on its partner eIF2. We combined mass spectrometry (MS) with chemical cross-linking, surface accessibility measurements and homology modelling to define subunit stoichiometry and interactions within eIF2B and eIF2. Although it is generally accepted that eIF2B is a pentamer of five non-identical subunits (α–ε), here we show that eIF2B is a decamer. MS and cross-linking of eIF2B complexes allows us to propose a model for the subunit arrangements within eIF2B where the subunit assembly occurs through catalytic γ- and ε-subunits, with regulatory subunits arranged in asymmetric trimers associated with the core. Cross-links between eIF2 and eIF2B allow modelling of interactions that contribute to nucleotide exchange and its control by eIF2 phosphorylation. Finally, we identify that GTP binds to eIF2Bγ, prompting us to propose a multi-step mechanism for nucleotide exchange. Eukaryotic Initiation Factor 2 (eIF2) initiates protein synthesis aided by its partner eIF2B, which stimulates guanine nucleotide exchange on eIF2. Here, Gordiyenko et al. show that eIF2B exists as a decamer and propose a model for its subunit arrangement that provides new insight into its function.
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Affiliation(s)
- Yuliya Gordiyenko
- 1] Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK [2] MRC Laboratory of Molecular Biology, University of Cambridge, Francis Crick Avenue, Cambridge CB2 0QH, UK [3]
| | - Carla Schmidt
- 1] Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK [2]
| | - Martin D Jennings
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Dijana Matak-Vinkovic
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Graham D Pavitt
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
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Bogorad AM, Xia B, Sandor DG, Mamonov AB, Cafarella TR, Jehle S, Vajda S, Kozakov D, Marintchev A. Insights into the architecture of the eIF2Bα/β/δ regulatory subcomplex. Biochemistry 2014; 53:3432-45. [PMID: 24811713 PMCID: PMC4045321 DOI: 10.1021/bi500346u] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Eukaryotic translation initiation factor 2B (eIF2B), the guanine nucleotide exchange factor for the G-protein eIF2, is one of the main targets for the regulation of protein synthesis. The eIF2B activity is inhibited in response to a wide range of stress factors and diseases, including viral infections, hypoxia, nutrient starvation, and heme deficiency, collectively known as the integrated stress response. eIF2B has five subunits (α-ε). The α, β, and δ subunits are homologous to each other and form the eIF2B regulatory subcomplex, which is believed to be a trimer consisting of monomeric α, β, and δ subunits. Here we use a combination of biophysical methods, site-directed mutagenesis, and bioinformatics to show that the human eIF2Bα subunit is in fact a homodimer, at odds with the current trimeric model for the eIF2Bα/β/δ regulatory complex. eIF2Bα dimerizes using the same interface that is found in the homodimeric archaeal eIF2Bα/β/δ homolog aIF2B and related metabolic enzymes. We also present evidence that the eIF2Bβ/δ binding interface is similar to that in the eIF2Bα2 homodimer. Mutations at the predicted eIF2Bβ/δ dimer interface cause genetic neurological disorders in humans. We propose that the eIF2B regulatory subcomplex is an α2β2δ2 hexamer, composed of one α2 homodimer and two βδ heterodimers. Our results offer novel insights into the architecture of eIF2B and its interactions with the G-protein eIF2.
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Affiliation(s)
- Andrew M Bogorad
- Department of Physiology and Biophysics, Boston University School of Medicine , Boston, Massachusetts 02118, United States
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