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Ryoo HD. The integrated stress response in metabolic adaptation. J Biol Chem 2024; 300:107151. [PMID: 38462161 PMCID: PMC10998230 DOI: 10.1016/j.jbc.2024.107151] [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: 11/15/2023] [Revised: 02/28/2024] [Accepted: 03/03/2024] [Indexed: 03/12/2024] Open
Abstract
The integrated stress response (ISR) refers to signaling pathways initiated by stress-activated eIF2α kinases. Distinct eIF2α kinases respond to different stress signals, including amino acid deprivation and mitochondrial stress. Such stress-induced eIF2α phosphorylation attenuates general mRNA translation and, at the same time, stimulates the preferential translation of specific downstream factors to orchestrate an adaptive gene expression program. In recent years, there have been significant new advances in our understanding of ISR during metabolic stress adaptation. Here, I discuss those advances, reviewing among others the ISR activation mechanisms in response to amino acid deprivation and mitochondrial stress. In addition, I review how ISR regulates the amino acid metabolic pathways and how changes in the ISR impact the physiology and pathology of various disease models.
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Affiliation(s)
- Hyung Don Ryoo
- Department of Cell Biology, New York University Grossman School of Medicine, New York, New York, USA.
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2
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Boone M, Zappa F. Signaling plasticity in the integrated stress response. Front Cell Dev Biol 2023; 11:1271141. [PMID: 38143923 PMCID: PMC10740175 DOI: 10.3389/fcell.2023.1271141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 11/29/2023] [Indexed: 12/26/2023] Open
Abstract
The Integrated Stress Response (ISR) is an essential homeostatic signaling network that controls the cell's biosynthetic capacity. Four ISR sensor kinases detect multiple stressors and relay this information to downstream effectors by phosphorylating a common node: the alpha subunit of the eukaryotic initiation factor eIF2. As a result, general protein synthesis is repressed while select transcripts are preferentially translated, thus remodeling the proteome and transcriptome. Mounting evidence supports a view of the ISR as a dynamic signaling network with multiple modulators and feedback regulatory features that vary across cell and tissue types. Here, we discuss updated views on ISR sensor kinase mechanisms, how the subcellular localization of ISR components impacts signaling, and highlight ISR signaling differences across cells and tissues. Finally, we consider crosstalk between the ISR and other signaling pathways as a determinant of cell health.
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3
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Ito T, Wuerth JD, Weber F. Protection of eIF2B from inhibitory phosphorylated eIF2: A viral strategy to maintain mRNA translation during the PKR-triggered integrated stress response. J Biol Chem 2023; 299:105287. [PMID: 37742919 PMCID: PMC10616414 DOI: 10.1016/j.jbc.2023.105287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/26/2023] Open
Abstract
The integrated stress response (ISR) protects cells from a variety of insults. Once elicited (e.g., by virus infections), it eventually leads to the block of mRNA translation. Central to the ISR are the interactions between translation initiation factors eIF2 and eIF2B. Under normal conditions, eIF2 drives the initiation of protein synthesis through hydrolysis of GTP, which becomes replenished by the guanine nucleotide exchange factor eIF2B. The antiviral branch of the ISR is activated by the RNA-activated kinase PKR which phosphorylates eIF2, thereby converting it into an eIF2B inhibitor. Here, we describe the recently solved structures of eIF2B in complex with eIF2 and a novel escape strategy used by viruses. While unphosphorylated eIF2 interacts with eIF2B in its "productive" conformation, phosphorylated eIF2 [eIF2(αP)] engages a different binding cavity on eIF2B and forces it into the "nonproductive" conformation that prohibits guanine nucleotide exchange factor activity. It is well established that viruses express so-called PKR antagonists that interfere with double-strand RNA, PKR itself, or eIF2. However recently, three taxonomically unrelated viruses were reported to encode antagonists targeting eIF2B instead. For one antagonist, the S segment nonstructural protein of Sandfly fever Sicilian virus, atomic structures showed that it occupies the eIF2(αP)-binding cavity on eIF2B without imposing a switch to the nonproductive conformation. S segment nonstructural protein thus antagonizes the activity of PKR by protecting eIF2B from inhibition by eIF2(αP). As the ISR and specifically eIF2B are central to neuroprotection and a wide range of genetic and age-related diseases, these developments may open new possibilities for treatments.
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Affiliation(s)
- Takuhiro Ito
- Laboratory for Translation Structural Biology, RIKEN Center for Biosystems Dynamics Research, Yokohama, Japan
| | | | - Friedemann Weber
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, Giessen, Germany.
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4
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Park SH, Helsley RN, Fadhul T, Willoughby JLS, Noetzli L, Tu HC, Solheim MH, Fujisaka S, Pan H, Dreyfuss JM, Bons J, Rose J, King CD, Schilling B, Lusis AJ, Pan C, Gupta M, Kulkarni RN, Fitzgerald K, Kern PA, Divanovic S, Kahn CR, Softic S. Fructose induced KHK-C can increase ER stress independent of its effect on lipogenesis to drive liver disease in diet-induced and genetic models of NAFLD. Metabolism 2023; 145:155591. [PMID: 37230214 PMCID: PMC10752375 DOI: 10.1016/j.metabol.2023.155591] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 05/04/2023] [Accepted: 05/10/2023] [Indexed: 05/27/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform leads to unresolved endoplasmic reticulum (ER) stress when coupled with a HFD intake. Conversely, a liver-specific knockdown of KHK in mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in mice with genetically induced obesity or metabolic dysfunction, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.
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Affiliation(s)
- Se-Hyung Park
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Robert N Helsley
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Taghreed Fadhul
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | | | - Leila Noetzli
- Alnylam Pharmaceuticals Inc., Cambridge, MA 02142, USA
| | - Ho-Chou Tu
- Alnylam Pharmaceuticals Inc., Cambridge, MA 02142, USA
| | - Marie H Solheim
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, 50931 Cologne, Germany
| | - Shiho Fujisaka
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Hui Pan
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Jonathan M Dreyfuss
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Joanna Bons
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Jacob Rose
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Christina D King
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Birgit Schilling
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Aldons J Lusis
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA, USA
| | - Calvin Pan
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA, USA
| | - Manoj Gupta
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Rohit N Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | | | - Philip A Kern
- Department of Medicine, Division of Endocrinology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Senad Divanovic
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - C Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
| | - Samir Softic
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA; Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
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5
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Hicks KG, Cluntun AA, Schubert HL, Hackett SR, Berg JA, Leonard PG, Ajalla Aleixo MA, Zhou Y, Bott AJ, Salvatore SR, Chang F, Blevins A, Barta P, Tilley S, Leifer A, Guzman A, Arok A, Fogarty S, Winter JM, Ahn HC, Allen KN, Block S, Cardoso IA, Ding J, Dreveny I, Gasper WC, Ho Q, Matsuura A, Palladino MJ, Prajapati S, Sun P, Tittmann K, Tolan DR, Unterlass J, VanDemark AP, Vander Heiden MG, Webb BA, Yun CH, Zhao P, Wang B, Schopfer FJ, Hill CP, Nonato MC, Muller FL, Cox JE, Rutter J. Protein-metabolite interactomics of carbohydrate metabolism reveal regulation of lactate dehydrogenase. Science 2023; 379:996-1003. [PMID: 36893255 PMCID: PMC10262665 DOI: 10.1126/science.abm3452] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/07/2023] [Indexed: 03/11/2023]
Abstract
Metabolic networks are interconnected and influence diverse cellular processes. The protein-metabolite interactions that mediate these networks are frequently low affinity and challenging to systematically discover. We developed mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically (MIDAS) to identify such interactions. Analysis of 33 enzymes from human carbohydrate metabolism identified 830 protein-metabolite interactions, including known regulators, substrates, and products as well as previously unreported interactions. We functionally validated a subset of interactions, including the isoform-specific inhibition of lactate dehydrogenase by long-chain acyl-coenzyme A. Cell treatment with fatty acids caused a loss of pyruvate-lactate interconversion dependent on lactate dehydrogenase isoform expression. These protein-metabolite interactions may contribute to the dynamic, tissue-specific metabolic flexibility that enables growth and survival in an ever-changing nutrient environment.
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Affiliation(s)
- Kevin G Hicks
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Ahmad A Cluntun
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Heidi L Schubert
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | | | - Jordan A Berg
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Paul G Leonard
- Core for Biomolecular Structure and Function, University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Institute for Applied Cancer Sciences, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Mariana A Ajalla Aleixo
- Laboratório de Cristalografia de Proteinas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Youjia Zhou
- School of Computing, University of Utah, Salt Lake City, UT, USA
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT, USA
| | - Alex J Bott
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Sonia R Salvatore
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Fei Chang
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Aubrie Blevins
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Paige Barta
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Samantha Tilley
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Aaron Leifer
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Andrea Guzman
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Ajak Arok
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Sarah Fogarty
- 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
| | - Jacob M Winter
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Hee-Chul Ahn
- Integrated Research Institute for Drug Development, College of Pharmacy, Dongguk University-Seoul, Goyang, The Republic of Korea
| | - Karen N Allen
- Department of Chemistry, Boston University, Boston, MA, USA
| | - Samuel Block
- The Koch Institute for Integrative Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Iara A Cardoso
- Laboratório de Cristalografia de Proteinas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Jianping Ding
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Shanghai, China
| | - Ingrid Dreveny
- Biodiscovery Institute, School of Pharmacy, University of Nottingham, Nottingham, UK
| | | | - Quinn Ho
- Department of Biology, Boston University, Boston, MA, USA
| | - Atsushi Matsuura
- Integrated Research Institute for Drug Development, College of Pharmacy, Dongguk University-Seoul, Goyang, The Republic of Korea
| | - Michael J Palladino
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Sabin Prajapati
- Department of Molecular Enzymology, Göttingen Center of Molecular Biosciences, University of Göttingen, Göttingen, Germany
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Pengkai Sun
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Shanghai, China
| | - Kai Tittmann
- Department of Molecular Enzymology, Göttingen Center of Molecular Biosciences, University of Göttingen, Göttingen, Germany
- Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dean R Tolan
- Department of Biology, Boston University, Boston, MA, USA
| | - Judith Unterlass
- Department of Oncology and Pathology, Karolinska Institute, Stockholm, Sweden
| | - Andrew P VanDemark
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Matthew G Vander Heiden
- The Koch Institute for Integrative Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Dana-Farber Cancer Institute, Boston, MA, USA
| | - Bradley A Webb
- Department of Biochemistry, West Virginia University, Morgantown, WV, USA
| | - Cai-Hong Yun
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Pengkai Zhao
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Bei Wang
- School of Computing, University of Utah, Salt Lake City, UT, USA
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT, USA
| | - Francisco J Schopfer
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
- Pittsburgh Heart, Lung, and Blood Vascular Medicine Institute, Pittsburgh, PA, USA
- Pittsburgh Liver Research Center, Pittsburgh, PA, USA
- Center for Metabolism and Mitochondrial Medicine, Pittsburgh, PA, USA
| | - Christopher P Hill
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Maria Cristina Nonato
- Laboratório de Cristalografia de Proteinas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Florian L Muller
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - James E Cox
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, 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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6
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Park SH, Helsley RN, Fadhul T, Willoughby JL, Noetzli L, Tu HC, Solheim MH, Fujisaka S, Pan H, Dreyfuss JM, Bons J, Rose J, King CD, Schilling B, Lusis AJ, Pan C, Gupta M, Kulkarni RN, Fitzgerald K, Kern PA, Divanovic S, Kahn CR, Softic S. Fructose Induced KHK-C Increases ER Stress and Modulates Hepatic Transcriptome to Drive Liver Disease in Diet-Induced and Genetic Models of NAFLD. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.27.525605. [PMID: 36747758 PMCID: PMC9900898 DOI: 10.1101/2023.01.27.525605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform increases endoplasmic reticulum (ER) stress in a dose dependent fashion, so when fructose is coupled with a HFD intake it leads to unresolved ER stress. Conversely, a liver-specific knockdown of KHK in C57BL/6J male mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in genetically obesity ob/ob, db/db and lipodystrophic FIRKO male mice, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.
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Affiliation(s)
- Se-Hyung Park
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Robert N. Helsley
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Taghreed Fadhul
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | | | | | - Ho-Chou Tu
- Alnylam Pharmaceuticals Inc., Cambridge, MA. 02142
| | - Marie H. Solheim
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, 50931 Cologne, Germany
| | - Shiho Fujisaka
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Hui Pan
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA
| | - Jonathan M. Dreyfuss
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA
| | - Joanna Bons
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Jacob Rose
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Christina D. King
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Birgit Schilling
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Aldons J. Lusis
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA USA
| | - Calvin Pan
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA USA
| | - Manoj Gupta
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215
| | - Rohit N. Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215
| | | | - Philip A. Kern
- Department of Medicine, Division of Endocrinology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Senad Divanovic
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - C. Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
| | - Samir Softic
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY. 40536
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7
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Philips O, Sultonova M, Blackmore B, Murphy JP. Understanding emerging bioactive metabolites with putative roles in cancer biology. Front Oncol 2022; 12:1014748. [PMID: 36249070 PMCID: PMC9557195 DOI: 10.3389/fonc.2022.1014748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/13/2022] [Indexed: 11/13/2022] Open
Abstract
Dysregulated metabolism in cancers is, by now, well established. Although metabolic adaptations provide cancers with the ability to synthesize the precursors required for rapid biosynthesis, some metabolites have direct functional, or bioactive, effects in human cells. Here we summarize recently identified metabolites that have bioactive roles either as post-translational modifications (PTMs) on proteins or in, yet unknown ways. We propose that these metabolites could play a bioactive role in promoting or inhibiting cancer cell phenotypes in a manner that is mostly unexplored. To study these potentially important bioactive roles, we discuss several novel metabolomic and proteomic approaches aimed at defining novel PTMs and metabolite-protein interactions. Understanding metabolite PTMs and protein interactors of bioactive metabolites may provide entirely new therapeutic targets for cancer.
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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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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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Kershaw CJ, Jennings MD, Cortopassi F, Guaita M, Al-Ghafli H, Pavitt GD. GTP binding to translation factor eIF2B stimulates its guanine nucleotide exchange activity. iScience 2021; 24:103454. [PMID: 34877508 PMCID: PMC8633983 DOI: 10.1016/j.isci.2021.103454] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/26/2021] [Accepted: 11/11/2021] [Indexed: 01/23/2023] Open
Abstract
eIF2B is the guanine nucleotide exchange factor (GEF) required for cytoplasmic protein synthesis initiation in eukaryotes and its regulation within the integrated stress response (ISR). It activates its partner factor eIF2, thereby promoting translation initiation. Here we provide evidence through biochemical and genetic approaches that eIF2B can bind directly to GTP and this can enhance its rate of GEF activity toward eIF2–GDP in vitro. GTP binds to a subcomplex of the eIF2Bγ and ε subunits. The eIF2Bγ amino-terminal domain shares structural homology with hexose sugar phosphate pyrophosphorylase enzymes that bind specific nucleotides. A K66R mutation in eIF2Bγ is especially sensitive to guanine or GTP in a range of functional assays. Taken together, our data suggest eIF2Bγ may act as a sensor of purine nucleotide availability and thus modulate eIF2B activity and protein synthesis in response to fluctuations in cellular nucleotide levels. eIF2B, the GDP exchange factor for eIF2 in translation and its control, binds GTP GTP binding enhances the rate of eIF2B GEF activity toward eIF2–GDP in vitro A K66R mutation in yeast eIF2Bγ is sensitive to guanine in vivo or GTP in vitro eIF2B may act as a sensor of purine nucleotide availability
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Affiliation(s)
- Christopher J Kershaw
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Martin D Jennings
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Francesco Cortopassi
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Margherita Guaita
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Hawra Al-Ghafli
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
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Schramm F, Borst A, Linne U, Soppa J. Elucidation of the Translation Initiation Factor Interaction Network of Haloferax volcanii Reveals Coupling of Transcription and Translation in Haloarchaea. Front Microbiol 2021; 12:742806. [PMID: 34764944 PMCID: PMC8576121 DOI: 10.3389/fmicb.2021.742806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/29/2021] [Indexed: 02/04/2023] Open
Abstract
Translation is an important step in gene expression. Initiation of translation is rate-limiting, and it is phylogenetically more diverse than elongation or termination. Bacteria contain only three initiation factors. In stark contrast, eukaryotes contain more than 10 (subunits of) initiation factors (eIFs). The genomes of archaea contain many genes that are annotated to encode archaeal homologs of eukaryotic initiation factors (aIFs). However, experimental characterization of aIFs is scarce and mostly restricted to very few species. To broaden the view, the protein-protein interaction network of aIFs in the halophilic archaeon Haloferax volcanii has been characterized. To this end, tagged versions of 14 aIFs were overproduced, affinity isolated, and the co-isolated binding partners were identified by peptide mass fingerprinting and MS/MS analyses. The aIF-aIF interaction network was resolved, and it was found to contain two interaction hubs, (1) the universally conserved factor aIF5B, and (2) a protein that has been annotated as the enzyme ribose-1,5-bisphosphate isomerase, which we propose to rename to aIF2Bα. Affinity isolation of aIFs also led to the co-isolation of many ribosomal proteins, but also transcription factors and subunits of the RNA polymerase (Rpo). To analyze a possible coupling of transcription and translation, seven tagged Rpo subunits were overproduced, affinity isolated, and co-isolated proteins were identified. The Rpo interaction network contained many transcription factors, but also many ribosomal proteins as well as the initiation factors aIF5B and aIF2Bα. These results showed that transcription and translation are coupled in haloarchaea, like in Escherichia coli. It seems that aIF5B and aIF2Bα are not only interaction hubs in the translation initiation network, but also key players in the transcription-translation coupling.
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Affiliation(s)
- Franziska Schramm
- Institute for Molecular Biosciences, Biocentre, Goethe-University, Frankfurt, Germany
| | - Andreas Borst
- Institute for Molecular Biosciences, Biocentre, Goethe-University, Frankfurt, Germany
| | - Uwe Linne
- Mass Spectrometry Facility, Department of Chemistry, Phillipps University Marburg, Marburg, Germany
| | - Jörg Soppa
- Institute for Molecular Biosciences, Biocentre, Goethe-University, Frankfurt, Germany
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