1
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Sekine Y, Houston R, Eckl EM, Fessler E, Narendra DP, Jae LT, Sekine S. A mitochondrial iron-responsive pathway regulated by DELE1. Mol Cell 2023; 83:2059-2076.e6. [PMID: 37327776 PMCID: PMC10329284 DOI: 10.1016/j.molcel.2023.05.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 02/13/2023] [Accepted: 05/22/2023] [Indexed: 06/18/2023]
Abstract
The heme-regulated kinase HRI is activated under heme/iron deficient conditions; however, the underlying molecular mechanism is incompletely understood. Here, we show that iron-deficiency-induced HRI activation requires the mitochondrial protein DELE1. Notably, mitochondrial import of DELE1 and its subsequent protein stability are regulated by iron availability. Under steady-state conditions, DELE1 is degraded by the mitochondrial matrix-resident protease LONP1 soon after mitochondrial import. Upon iron chelation, DELE1 import is arrested, thereby stabilizing DELE1 on the mitochondrial surface to activate the HRI-mediated integrated stress response (ISR). Ablation of this DELE1-HRI-ISR pathway in an erythroid cell model enhances cell death under iron-limited conditions, suggesting a cell-protective role for this pathway in iron-demanding cell lineages. Our findings highlight mitochondrial import regulation of DELE1 as the core component of a previously unrecognized mitochondrial iron responsive pathway that elicits stress signaling following perturbation of iron homeostasis.
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Affiliation(s)
- Yusuke Sekine
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA; Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Ryan Houston
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Eva-Maria Eckl
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Evelyn Fessler
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Derek P Narendra
- Inherited Movement Disorders Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20814, USA
| | - Lucas T Jae
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Shiori Sekine
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA; Division of Cardiology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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2
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Zhang F, Zeng QY, Xu H, Xu AN, Liu DJ, Li NZ, Chen Y, Jin Y, Xu CH, Feng CZ, Zhang YL, Liu D, Liu N, Xie YY, Yu SH, Yuan H, Xue K, Shi JY, Liu TX, Xu PF, Zhao WL, Zhou Y, Wang L, Huang QH, Chen Z, Chen SJ, Zhou XL, Sun XJ. Selective and competitive functions of the AAR and UPR pathways in stress-induced angiogenesis. Cell Discov 2021; 7:98. [PMID: 34697290 PMCID: PMC8547220 DOI: 10.1038/s41421-021-00332-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/31/2021] [Indexed: 12/30/2022] Open
Abstract
The amino acid response (AAR) and unfolded protein response (UPR) pathways converge on eIF2α phosphorylation, which is catalyzed by Gcn2 and Perk, respectively, under different stresses. This close interconnection makes it difficult to specify different functions of AAR and UPR. Here, we generated a zebrafish model in which loss of threonyl-tRNA synthetase (Tars) induces angiogenesis dependent on Tars aminoacylation activity. Comparative transcriptome analysis of the tars-mutant and wild-type embryos with/without Gcn2- or Perk-inhibition reveals that only Gcn2-mediated AAR is activated in the tars-mutants, whereas Perk functions predominantly in normal development. Mechanistic analysis shows that, while a considerable amount of eIF2α is normally phosphorylated by Perk, the loss of Tars causes an accumulation of uncharged tRNAThr, which in turn activates Gcn2, leading to phosphorylation of an extra amount of eIF2α. The partial switchover of kinases for eIF2α largely overwhelms the functions of Perk in normal development. Interestingly, although inhibition of Gcn2 and Perk in this stress condition both can reduce the eIF2α phosphorylation levels, their functional consequences in the regulation of target genes and in the rescue of the angiogenic phenotypes are dramatically different. Indeed, genetic and pharmacological manipulations of these pathways validate that the Gcn2-mediated AAR, but not the Perk-mediated UPR, is required for tars-deficiency induced angiogenesis. Thus, the interconnected AAR and UPR pathways differentially regulate angiogenesis through selective functions and mutual competitions, reflecting the specificity and efficiency of multiple stress response pathways that evolve integrally to enable an organism to sense/respond precisely to various types of stresses.
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Affiliation(s)
- Fan Zhang
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qi-Yu Zeng
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Hao Xu
- Department of Cardiology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ai-Ning Xu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Dian-Jia Liu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Ning-Zhe Li
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yi Chen
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi Jin
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chun-Hui Xu
- CAS Key Laboratory of Tissue Microenvironment and Tumor, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Chang-Zhou Feng
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yuan-Liang Zhang
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Dan Liu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Key Laboratory of Systems Biomedicine, Ministry of Education, Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, China
| | - Na Liu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,CAS Key Laboratory of Tissue Microenvironment and Tumor, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Yin-Yin Xie
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shan-He Yu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hao Yuan
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Kai Xue
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing-Yi Shi
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ting Xi Liu
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.,CAS Key Laboratory of Tissue Microenvironment and Tumor, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Peng-Fei Xu
- Division of Human Reproduction and Developmental Genetics, Women's Hospital, and Institute of Genetics and Department of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Wei-Li Zhao
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi Zhou
- Stem Cell Program, Hematology/Oncology Program at Children's Hospital Boston and Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Lan Wang
- CAS Key Laboratory of Tissue Microenvironment and Tumor, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Qiu-Hua Huang
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhu Chen
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Sai-Juan Chen
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Xiao-Long Zhou
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.
| | - Xiao-Jian Sun
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine (Shanghai), Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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3
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Smyth R, Sun J. Protein Kinase R in Bacterial Infections: Friend or Foe? Front Immunol 2021; 12:702142. [PMID: 34305942 PMCID: PMC8297547 DOI: 10.3389/fimmu.2021.702142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/28/2021] [Indexed: 12/28/2022] Open
Abstract
The global antimicrobial resistance crisis poses a significant threat to humankind in the coming decades. Challenges associated with the development of novel antibiotics underscore the urgent need to develop alternative treatment strategies to combat bacterial infections. Host-directed therapy is a promising new therapeutic strategy that aims to boost the host immune response to bacteria rather than target the pathogen itself, thereby circumventing the development of antibiotic resistance. However, host-directed therapy depends on the identification of druggable host targets or proteins with key functions in antibacterial defense. Protein Kinase R (PKR) is a well-characterized human kinase with established roles in cancer, metabolic disorders, neurodegeneration, and antiviral defense. However, its role in antibacterial defense has been surprisingly underappreciated. Although the canonical role of PKR is to inhibit protein translation during viral infection, this kinase senses and responds to multiple types of cellular stress by regulating cell-signaling pathways involved in inflammation, cell death, and autophagy - mechanisms that are all critical for a protective host response against bacterial pathogens. Indeed, there is accumulating evidence to demonstrate that PKR contributes significantly to the immune response to a variety of bacterial pathogens. Importantly, there are existing pharmacological modulators of PKR that are well-tolerated in animals, indicating that PKR is a feasible target for host-directed therapy. In this review, we provide an overview of immune cell functions regulated by PKR and summarize the current knowledge on the role and functions of PKR in bacterial infections. We also review the non-canonical activators of PKR and speculate on the potential mechanisms that trigger activation of PKR during bacterial infection. Finally, we provide an overview of existing pharmacological modulators of PKR that could be explored as novel treatment strategies for bacterial infections.
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Affiliation(s)
- Robin Smyth
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Jim Sun
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
- Centre for Infection, Immunity and Inflammation, University of Ottawa, Ottawa, ON, Canada
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4
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Yan H, Hales BF. Effects of an Environmentally Relevant Mixture of Organophosphate Esters Derived From House Dust on Endochondral Ossification in Murine Limb Bud Cultures. Toxicol Sci 2021; 180:62-75. [PMID: 33367866 PMCID: PMC7916738 DOI: 10.1093/toxsci/kfaa180] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Organophosphate esters (OPEs) are used widely as flame retardants and plasticizers but much remains unknown about their potential toxicity. Previously, we reported that 4 individual OPEs suppress endochondral ossification in murine limb bud cultures. However, real-life exposure is to complex OPE mixtures. In the present study, we tested the hypothesis that a Canadian household dust-based OPE mixture will affect endochondral ossification in gestation day 13 CD1 mouse embryo limb buds expressing fluorescent markers for the major cell populations involved in the process: collagen type II alpha 1-enhanced cyan fluorescent protein (proliferative chondrocytes), collagen type X alpha 1-mCherry (hypertrophic chondrocytes), and collagen type I alpha 1-yellow fluorescent protein (osteoblasts). Limbs were cultured for 6 days in the presence of vehicle or dilutions of the OPE mixture (1/1 000 000, 1/600 000, and 1/300 000). All 3 OPE mixture dilutions affected cartilage template development and the progression of endochondral ossification, as indicated by the fluorescent markers. The expression of Sox9, the master regulator of chondrogenesis, was unchanged, but the expression of Runx2 and Sp7, which drive chondrocyte hypertrophy and osteoblastogenesis, was dilution-dependently suppressed. RNA-seq revealed that exposure to the 1/300 000 dilution of the OPE mixture for 24 h downregulated 153 transcripts and upregulated 48 others by at least 1.5-fold. Downregulated transcripts were enriched for those related to the immune system and bone formation. In contrast, upregulated transcripts were enriched for those with stress response functions known to be regulated by ATF4 activation. Thus, exposure to the mixture of OPEs commonly found in house dust may have adverse effects on bone formation.
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Affiliation(s)
- Han Yan
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Barbara F Hales
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada
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5
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Meierjohann S. Effect of stress-induced polyploidy on melanoma reprogramming and therapy resistance. Semin Cancer Biol 2021; 81:232-240. [PMID: 33610722 DOI: 10.1016/j.semcancer.2021.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 01/03/2021] [Accepted: 02/09/2021] [Indexed: 12/15/2022]
Abstract
Melanomas and their precursors, the melanocytes, are frequently exposed to UV due to their anatomic location, leading to DNA damage and reactive oxygen stress related harm. Such damage can result in multinucleation or polyploidy, in particularly in presence of mitotic or cell division failure. As a consequence, the cell encounters either of two fates: mitotic catastrophe, resulting in cell death, or survival and recovery, the latter occurring less frequently. However, when cells manage to recover in an polyploid state, they have often acquired new features, which allow them to tolerate and adapt to oncogene- or therapy induced stress. This review focuses on polyploidy inducers in melanoma and their effects on transcriptional reprogramming and phenotypic adaptation as well as the relevance of polyploid melanoma cells for therapy resistance.
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Affiliation(s)
- Svenja Meierjohann
- Institute of Pathology, University of Würzburg, Würzburg, Germany; Comprehensive Cancer Center Mainfranken, University Hospital Würzburg, Würzburg, Germany.
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6
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Clotrimazole inhibits the Wnt/β-catenin pathway by activating two eIF2α kinases: The heme-regulated translational inhibitor and the double-stranded RNA-induced protein kinase. Biochem Biophys Res Commun 2018; 506:183-188. [PMID: 30342850 DOI: 10.1016/j.bbrc.2018.10.053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 10/07/2018] [Indexed: 01/08/2023]
Abstract
The Wnt/β-catenin signaling pathway controls cell proliferation and differentiation, and therefore, when this pathway is excessively activated, it causes tumorigenesis. Our chemical suppressor screening in zebrafish embryos identified antifungal azoles including clotrimazole, miconazole, and itraconazole, as Wnt/β-catenin signaling inhibitors. Here we show the mechanism underlying the Wnt/β-catenin pathway inhibition by antifungal azoles. Clotrimazole reduced β-catenin revels in a proteasome-independent fashion. By gene knockdown of two translational regulators, heme-regulated translational inhibitor and double-stranded RNA-induced protein kinase, we show that they mediate the clotrimazole-induced inhibition of the Wnt/β-catenin pathway. Thus, clotrimazole inhibits the Wnt/β-catenin pathway by decreasing β-catenin protein levels through translational regulation. Antifungal azoles represent genuine candidate compounds for anticancer drugs or chemopreventive agents that reduce adenomatous polyps.
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7
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Ranu RS, Gowda S, Scholthof H, Wu FC, Shepherd RJ. In vitro translation of the full-length RNA transcript of figwort mosaic virus (Caulimovirus). Gene Expr 2018; 5:143-53. [PMID: 8882638 PMCID: PMC6138018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The circular DNA genome of FMV consists of seven tandemly arranged genes placed successively on a full-length RNA transcript that spans the entire circular viral genome. This transcript is a tentative mRNA for at least five of the six major conserved genes of this virus (genes I-V) that are positioned on this transcript. The sixth major gene (gene VI) is expressed as a separate monocistronic transcript. A long 5'-nontranslated leader (598 nucleotides), a small nonconserved gene (VII), and a short intergenic region (57 nucleotides) precede the five major conserved genes (I through V) on the full-length transcript. A reporter gene (CAT), as a separate cistron or fused in-frame, to viral cistrons in various downstream positions in cloned versions of the viral genome was used in a transcription vector to generate artificial full-length transcripts of FMV. When these mRNAs were translated in vitro (rabbit reticulocyte lysate system), the reporter gene was translated efficiently in all positions. Translation of internal native viral gene positioned on the full-length transcript of FMV was also determined (the gene VI product). These observations suggest that the full-length FMV transcript functions as a polycistronic mRNA in plants. Results are best explained on the basis of translational coupling/relay race model.
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Affiliation(s)
- R S Ranu
- Department of Plant Pathology and Weed Science, Colorado State University, Fort Collins 80523, USA
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8
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Ramos-Fernández E, Tajes M, ILL-Raga G, Vargas L, Busquets-García A, Bosch-Morató M, Guivernau B, Valls-Comamala V, Gomis M, Grau C, Fandos C, Rosen MD, Rabinowitz MH, Inestrosa N, Maldonado R, Altafaj X, Ozaita A, Alvarez A, Vicente R, Valverde MA, Muñoz FJ. Glutamatergic stimulation induces GluN2B translation by the nitric oxide-Heme-Regulated eIF2α kinase in cortical neurons. Oncotarget 2016; 7:58876-58892. [PMID: 27557499 PMCID: PMC5312282 DOI: 10.18632/oncotarget.11417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 08/13/2016] [Indexed: 02/06/2023] Open
Abstract
The activation of N-Methyl D-Aspartate Receptor (NMDAR) by glutamate is crucial in the nervous system function, particularly in memory and learning. NMDAR is composed by two GluN1 and two GluN2 subunits. GluN2B has been reported to participate in the prevalent NMDAR subtype at synapses, the GluN1/2A/2B. Here we studied the regulation of GluN2B expression in cortical neurons finding that glutamate up-regulates GluN2B translation through the action of nitric oxide (NO), which induces the phosphorylation of the eukaryotic translation initiation factor 2 α (eIF2α). It is a process mediated by the NO-heme-regulated eIF2α kinase (HRI), as the effect was avoided when a specific HRI inhibitor or a HRI small interfering RNA (siHRI) were used. We found that the expressed GluN2B co-localizes with PSD-95 at the postsynaptic ending, which strengthen the physiological relevance of the proposed mechanism. Moreover the receptors bearing GluN2B subunits upon NO stimulation are functional as high Ca2+ entry was measured and increases the co-localization between GluN2B and GluN1 subunits. In addition, the injection of the specific HRI inhibitor in mice produces a decrease in memory retrieval as tested by the Novel Object Recognition performance. Summarizing our data suggests that glutamatergic stimulation induces HRI activation by NO to trigger GluN2B expression and this process would be relevant to maintain postsynaptic activity in cortical neurons.
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Affiliation(s)
- Eva Ramos-Fernández
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Marta Tajes
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Gerard ILL-Raga
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Lina Vargas
- Cell Signaling Laboratory, Department of Cellular and Molecular Biology, Faculty of Biological Science, Pontificia Universidad Católica, Santiago, Chile
| | - Arnau Busquets-García
- Neuropharmacology Laboratory, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Mònica Bosch-Morató
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Biuse Guivernau
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Victòria Valls-Comamala
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Maria Gomis
- Neuropharmacology Laboratory, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Cristina Grau
- Bellvitge Biomedical Research Institute, Unit of Neuropharmacology and Pain, University of Barcelona, Barcelona, Spain
| | - César Fandos
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Mark D. Rosen
- Janssen Research and Development, L.L.C., San Diego, CA, United States of America
| | | | - Nibaldo Inestrosa
- CARE, Department of Cellular and Molecular Biology, Faculty of Biological Science, Pontificia Universidad Católica, Santiago, Chile
| | - Rafael Maldonado
- Neuropharmacology Laboratory, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Xavier Altafaj
- Bellvitge Biomedical Research Institute, Unit of Neuropharmacology and Pain, University of Barcelona, Barcelona, Spain
| | - Andrés Ozaita
- Neuropharmacology Laboratory, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Alejandra Alvarez
- Cell Signaling Laboratory, Department of Cellular and Molecular Biology, Faculty of Biological Science, Pontificia Universidad Católica, Santiago, Chile
| | - Rubén Vicente
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Miguel A. Valverde
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
| | - Francisco J. Muñoz
- Laboratory of Molecular Physiology, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
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9
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Zhang FL, Shen GM, Liu XL, Wang F, Zhao HL, Yu J, Zhang JW. Hypoxic induction of human erythroid-specific δ-aminolevulinate synthase mediated by hypoxia-inducible factor 1. Biochemistry 2011; 50:1194-202. [PMID: 21207956 DOI: 10.1021/bi101585c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hypoxia-inducible factor 1 (HIF1) is a heterodimeric basic helix-loop-helix transcription factor that regulates many key genes. δ-Aminolevulinate synthase (ALAS) catalyzes the first and rate-limiting reaction in the heme biosynthetic pathway. In this study, we show that hypoxia-induced expression of erythroid-specific ALAS2 is mediated by HIF1 in erythroid cells. Under hypoxic conditions, significantly increased ALAS2 mRNA and protein levels were detected in K562 cells and erythroid induction cultures of CD34+ hematopoietic stem/progenitor cells. Enforced HIF1α expression increased the level of ALAS2 expression, while HIF1α knockdown by RNA interference decreased the level of ALAS2 expression. In silico analysis revealed three potential hypoxia-response elements (HREs) that are located 611, 621, and 741 bp downstream of the ALAS2 gene. The results from reporter gene and mutation analysis suggested that these elements are necessary for a maximal hypoxic response. Chromatin immunoprecipitation and polymerase chain reaction showed that the HREs could be recognized and bound by HIF1α in vivo. These results demonstrate that the upregulation of ALAS2 during hypoxia is directly mediated by HIF1. We hypothesize that HIF1-mediated ALAS2 upregulation promotes erythropoiesis to satisfy the needs of an organism under hypoxic conditions. This may be accomplished via increased heme levels and an interaction between ALAS2 and erythropoietin.
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Affiliation(s)
- Feng-Lin Zhang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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10
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Adachi M, Liu Y, Fujii K, Calderwood SK, Nakai A, Imai K, Shinomura Y. Oxidative stress impairs the heat stress response and delays unfolded protein recovery. PLoS One 2009; 4:e7719. [PMID: 19936221 PMCID: PMC2777389 DOI: 10.1371/journal.pone.0007719] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 10/05/2009] [Indexed: 11/30/2022] Open
Abstract
Background Environmental changes, air pollution and ozone depletion are increasing oxidative stress, and global warming threatens health by heat stress. We now face a high risk of simultaneous exposure to heat and oxidative stress. However, there have been few studies investigating their combined adverse effects on cell viability. Principal Findings Pretreatment of hydrogen peroxide (H2O2) specifically and highly sensitized cells to heat stress, and enhanced loss of mitochondrial membrane potential. H2O2 exposure impaired the HSP40/HSP70 induction as heat shock response (HSR) and the unfolded protein recovery, and enhanced eIF2α phosphorylation and/or XBP1 splicing, land marks of ER stress. These H2O2-mediated effects mimicked enhanced heat sensitivity in HSF1 knockdown or knockout cells. Importantly, thermal preconditioning blocked H2O2–mediated inhibitory effects on refolding activity and rescued HSF1 +/+ MEFs, but neither blocked the effects nor rescued HSF1 -/- MEFs. These data strongly suggest that inhibition of HSR and refolding activity is crucial for H2O2–mediated enhanced heat sensitivity. Conclusions H2O2 blocks HSR and refolding activity under heat stress, thereby leading to insufficient quality control and enhancing ER stress. These uncontrolled stress responses may enhance cell death. Our data thus highlight oxidative stress as a crucial factor affecting heat tolerance.
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Affiliation(s)
- Masaaki Adachi
- Division of Molecular Oncology and Molecular Diagnosis, Sapporo Medical University School of Medicine, Sapporo, Japan.
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Kaneko K, Furuyama K, Aburatani H, Shibahara S. Hypoxia induces erythroid-specific 5-aminolevulinate synthase expression in human erythroid cells through transforming growth factor-β signaling. FEBS J 2009; 276:1370-82. [DOI: 10.1111/j.1742-4658.2009.06878.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Furuyama K, Kaneko K, Vargas PD. Heme as a magnificent molecule with multiple missions: heme determines its own fate and governs cellular homeostasis. TOHOKU J EXP MED 2007; 213:1-16. [PMID: 17785948 DOI: 10.1620/tjem.213.1] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Heme is a prosthetic group of various types of proteins, such as hemoglobin, myoglobin, cytochrome c, cytochrome p450, catalase and peroxidase. In addition, heme is involved in a variety of biological events by modulating the function or the state of hemoproteins. For example, protein synthesis is inhibited in erythroid cells under heme deficiency, as the consequence of the activation of heme-regulated inhibitor (HRI). Iron concentration in the cell is sensed and regulated by the heme-mediated oxidization and subsequent degradation of iron regulatory protein 2 (IRP2). Heme also binds to certain types of potassium channels, thereby inhibiting transmembrane K(+) currents. Importantly, heme determines its own fate; namely, heme regulates its synthesis and degradation through the feedback mechanisms, by which intracellular heme level is precisely maintained. Heme reduces heme synthesis by suppressing the expression of non-specific 5-aminolevulinate synthase (ALAS1) and stimulates heme breakdown by inducing heme oxygenase (HO)-1 expression. ALAS1 and HO-1 are the rate limiting enzymes in heme biosynthesis and catabolism, respectively. Accordingly, under the heme-rich condition, heme binds to cysteine-proline (CP) motifs of ALAS1 and those of transcriptional repressor Bach1, thereby leading to repression of mitochondrial transport of ALAS1 and induction of HO-1 transcription, respectively. Moreover, chemosensing functions of HO-2 containing CP motifs, another isozyme of HO, have been unveiled recently. In this review article, we summarize and update the pleiotropic effects of heme on various biological events and the regulatory network of heme biosynthesis and catabolism.
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Affiliation(s)
- Kazumichi Furuyama
- Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
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BONANOU-TZEDAKI SA, SOHI MK, ARNSTEIN HRV. Regulation of Protein Synthesis in Reticulocyte Lysates. ACTA ACUST UNITED AC 2005. [DOI: 10.1111/j.1432-1033.1981.tb06174.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Hsp90 regulates protein synthesis by activating the heme-regulated eukaryotic initiation factor 2α (eIF-2α) kinase in rabbit reticulocyte lysates. J Biosci 1998. [DOI: 10.1007/bf02936128] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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15
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Heme-regulated eukaryotic initiation factor 2α kinase—A molecular indicator of haemolytic anemia. J Biosci 1997. [DOI: 10.1007/bf02703232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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16
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Association of HSP90 with the heme-regulated eukaryotic initiation factor 2α kinase—A collaboration for regulating protein synthesis. J Biosci 1996. [DOI: 10.1007/bf02703108] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Abstract
The role of heme-regulated eIF-2 alpha kinase (HRI) in the regulation of protein synthesis in rabbit reticulocytes is well documented. Inhibitors of protein synthesis with properties similar to those of HRI have been described in some nonerythroid cell types, but it has not yet been determined whether these eIF-2 alpha kinase activities are mediated by HRI or one or more as yet uncharacterized kinases. We have studied the expression of mRNA, polypeptide, and kinase activities of HRI in various tissues from both nonanemic and anemic rabbits. Our results indicate that HRI is expressed in an erythroid cell-specific manner. HRI is present in the bone marrow and peripheral blood of both nonanemic and anemic rabbits but not in any of the other tissues tested. HRI mRNA is present at low levels in uninduced mouse erythroleukemic (MEL) cells and human K562 cells and accumulates to higher levels upon induction. The accumulation of HRI mRNA in differentiating MEL cells is dependent upon the presence of heme. The addition of 3-amino-1,2,4-triazole (AT), an inhibitor of heme biosynthesis, to the induction medium markedly reduced HRI mRNA accumulation. Simultaneous addition of hemin and AT to the dimethyl sulfoxide induction medium largely prevented the inhibition of HRI mRNA induction by AT. These findings indicate that HRI is expressed in an erythroid cell-specific manner and that the major physiologic role of HRI is in adjusting the synthesis of globins to the availability of heme.
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Crosby JS, Lee K, London IM, Chen JJ. Erythroid expression of the heme-regulated eIF-2 alpha kinase. Mol Cell Biol 1994; 14:3906-14. [PMID: 7910943 PMCID: PMC358757 DOI: 10.1128/mcb.14.6.3906-3914.1994] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The role of heme-regulated eIF-2 alpha kinase (HRI) in the regulation of protein synthesis in rabbit reticulocytes is well documented. Inhibitors of protein synthesis with properties similar to those of HRI have been described in some nonerythroid cell types, but it has not yet been determined whether these eIF-2 alpha kinase activities are mediated by HRI or one or more as yet uncharacterized kinases. We have studied the expression of mRNA, polypeptide, and kinase activities of HRI in various tissues from both nonanemic and anemic rabbits. Our results indicate that HRI is expressed in an erythroid cell-specific manner. HRI is present in the bone marrow and peripheral blood of both nonanemic and anemic rabbits but not in any of the other tissues tested. HRI mRNA is present at low levels in uninduced mouse erythroleukemic (MEL) cells and human K562 cells and accumulates to higher levels upon induction. The accumulation of HRI mRNA in differentiating MEL cells is dependent upon the presence of heme. The addition of 3-amino-1,2,4-triazole (AT), an inhibitor of heme biosynthesis, to the induction medium markedly reduced HRI mRNA accumulation. Simultaneous addition of hemin and AT to the dimethyl sulfoxide induction medium largely prevented the inhibition of HRI mRNA induction by AT. These findings indicate that HRI is expressed in an erythroid cell-specific manner and that the major physiologic role of HRI is in adjusting the synthesis of globins to the availability of heme.
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MESH Headings
- Anemia/enzymology
- Animals
- Blotting, Northern
- Blotting, Western
- Cell Line
- Cells, Cultured
- Erythrocytes/enzymology
- Gene Expression Regulation, Enzymologic
- Heme/pharmacology
- Humans
- Leukemia, Experimental
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive
- Mice
- Organ Specificity
- Polymerase Chain Reaction
- Protein Serine-Threonine Kinases/analysis
- Protein Serine-Threonine Kinases/biosynthesis
- Protein Serine-Threonine Kinases/blood
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- Rabbits
- Tumor Cells, Cultured
- eIF-2 Kinase
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Affiliation(s)
- J S Crosby
- Harvard-M.I.T. Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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19
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Yang J, London I, Chen J. Effects of hemin and porphyrin compounds on intersubunit disulfide formation of heme-regulated eIF-2 alpha kinase and the regulation of protein synthesis in reticulocyte lysates. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)88733-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Affiliation(s)
- C G Proud
- Department of Biochemistry, School of Medical Sciences, University of Bristol, England
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Chen JJ, Throop MS, Gehrke L, Kuo I, Pal JK, Brodsky M, London IM. Cloning of the cDNA of the heme-regulated eukaryotic initiation factor 2 alpha (eIF-2 alpha) kinase of rabbit reticulocytes: homology to yeast GCN2 protein kinase and human double-stranded-RNA-dependent eIF-2 alpha kinase. Proc Natl Acad Sci U S A 1991; 88:7729-33. [PMID: 1679235 PMCID: PMC52376 DOI: 10.1073/pnas.88.17.7729] [Citation(s) in RCA: 161] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have cloned the cDNA of the heme-regulated eIF-2 alpha kinase (HRI) of rabbit reticulocytes. In vitro translation of mRNA transcribed from the HRI cDNA yields a 90-kDa polypeptide that exhibits eIF-2 alpha kinase activity and is recognized by a monoclonal antibody directed against authentic HRI. The open reading frame sequence of the HRI cDNA contains all 11 catalytic domains of protein kinases with consensus sequences of protein-serine/threonine kinases in conserved catalytic domains VI and VIII. The HRI cDNA also contains an insert of approximately 140 amino acids between catalytic domains V and VI. The HRI cDNA coding sequence has extensive homology to GCN2 protein kinase of Saccharomyces cerevisiae and to human double-stranded-RNA-dependent eIF-2 alpha kinase. This observation suggests that GCN2 protein kinase may be an eIF-2 alpha kinase in yeast. In addition, HRI has an unusually high degree of homology to three protein kinases (NimA, Wee1, and CDC2) that are involved in the regulation of the cell cycle.
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Affiliation(s)
- J J Chen
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge
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22
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Pal JK, Chen JJ, London IM. Tissue distribution and immunoreactivity of heme-regulated eIF-2 alpha kinase determined by monoclonal antibodies. Biochemistry 1991; 30:2555-62. [PMID: 1672093 DOI: 10.1021/bi00223a037] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A highly purified preparation of heme-regulated inhibitor (HRI), an eIF-2 alpha kinase, from rabbit reticulocyte lysates has been used for generating monoclonal antibodies (mAB). Two hybridoma clones secreting HRI-specific antibodies (mAB A and mAB F) were obtained. Both antibodies immunoprecipitated biosynthetically labeled as well as phosphorylated HRI in reticulocyte lysates and also recognized denatured HRI in a Western blot. In in vitro protein kinase assays, preincubation of HRI with the antibodies significantly diminished both autokinase and eIF-2 alpha kinase activities. HRI from reticulocyte lysates could be quantitatively removed by immunoprecipitation with mAB F, and such HRI-depleted lysates were able to maintain protein synthesis under conditions of heme deficiency. With these monoclonal antibodies, HRI was detected only in the reticulocytes and bone marrow of anemic rabbits, among several rabbit tissues tested. The antibodies did not detect cross-reacting HRI in rat or human reticulocytes or in mouse erythroleukemic cells or human K562 cells even after induction of differentiation, although eIF-2 alpha kinase activity was detected in them. Polyclonal anti-rabbit HRI antibody detected HRI in rat reticulocytes. However, no cross-reacting HRI was detected by polyclonal antibody in human reticulocytes or other cell types tested. These findings suggest that HRI is not ubiquitous, and may be erythroid-specific, and that it is antigenically different in different species.
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Affiliation(s)
- J K Pal
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge 02139
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Chen JJ, Pal JK, Petryshyn R, Kuo I, Yang JM, Throop MS, Gehrke L, London IM. Amino acid microsequencing of internal tryptic peptides of heme-regulated eukaryotic initiation factor 2 alpha subunit kinase: homology to protein kinases. Proc Natl Acad Sci U S A 1991; 88:315-9. [PMID: 1671169 PMCID: PMC50801 DOI: 10.1073/pnas.88.2.315] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have purified the heme-regulated eukaryotic initiation factor 2 alpha subunit (eIF-2 alpha) kinase (HRI) from rabbit reticulocytes for amino acid microsequencing. This kinase is a single 92-kDa polypeptide and migrates in perfect alignment with 32P-labeled HRI on SDS/PAGE. Its functions of binding ATP and of autophosphorylation and eIF-2 alpha phosphorylation are inhibited by hemin. The amino acid sequences of three tryptic peptides of HRI have been obtained. A search of the data base of the National Biomedical Research Foundation reveals that these amino acid sequences are unique and that two of these three sequences show homology to protein kinases. HRI peptide P-52 contains Asp-Phe-Gly, which is the most highly conserved short stretch of amino acids in catalytic domain VII of protein kinases. HRI peptide P-74 contains the conserved amino acid residues Asp-(Met)-Tyr-Ser-(Val)-Gly-Val found in catalytic domain IX of protein kinases [Hanks, S. K., Quinn, A. M. & Hunter, T. (1988) Science 241, 42-52]. These findings are consistent with the autokinase and eIF-2 alpha kinase activities of HRI. Synthetic HRI peptide P-74 is a very potent inhibitor of eIF-2 alpha phosphorylation by HRI. Since little is known about the function of conserved domain IX, P-74 peptide may be useful in elucidating the role of this domain of protein kinases.
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Affiliation(s)
- J J Chen
- Harvard-MIT Division of Health Sciences, Cambridge, MA 02139
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24
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Evidence for the Association of the Heme-regulated eIF-2α Kinase with the 90-kDa Heat Shock Protein in Rabbit Reticulocyte Lysate in Situ. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84864-0] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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25
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Chen JJ, Yang JM, Petryshyn R, Kosower N, London IM. Disulfide Bond Formation in the Regulation of eIF-2 α Kinase by Heme. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)60568-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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26
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Identification of spectrin-related peptides associated with the reticulocyte heme-controlled alpha subunit of eukaryotic translational initiation factor 2 kinase and of Mr 95,000 peptide that appears to be the catalytic subunit. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47990-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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27
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Rovnak J, Ranu RS. Purification of 2',5'-oligoadenylate synthetase from rabbit reticulocytes. JOURNAL OF INTERFERON RESEARCH 1987; 7:231-41. [PMID: 3611843 DOI: 10.1089/jir.1987.7.231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The 2',5'-oligoadenylate synthetase (2-5A synthetase) from rabbit reticulocytes has been purified to apparent homogeneity. The purification procedure consists of (NH4)2SO4 fractionation (30-50% cut), specific binding of the 2-5A synthetase to and elution from the affinity matrix of polyinosinic-polycytidylic-cellulose, another (NH4)2SO4 precipitation step, and finally chromatography on DEAE-cellulose. Upon electrophoresis in sodium dodecyl sulfate polyacrylamide gel (10%), the purified enzyme migrates as a single polypeptide with an apparent molecular weight of 110,000 daltons. A sedimentation coefficient of 5.8S is obtained by glycerol density gradient centrifugation. The synthesis of 2',5'-oligoadenylate by the purified enzyme is dependent on the presence of double-stranded (ds) RNA, in the absence of which the enzyme is highly unstable. Biochemical characteristics of the purified enzyme have been defined.
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28
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London IM, Levin DH, Matts RL, Thomas NSB, Petryshyn R, Chen JJ. 12 Regulation of Protein Synthesis. CONTROL BY PHOSPHORYLATION PART B - SPECIFIC ENZYMES (II) BIOLOGICAL PROCESSES 1987. [DOI: 10.1016/s1874-6047(08)60263-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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29
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Roberts RC, Ranu RS. Regulation of protein synthesis in rabbit reticulocyte lysates. Requirement of initiation factor eIF-2 holoprotein for substrate specificity of heme-regulated protein kinase. FEBS Lett 1986; 209:162-4. [PMID: 3792542 DOI: 10.1016/0014-5793(86)81103-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The specificity of the heme-regulated protein kinase (HRI) was investigated further by utilizing the isolated 38,000 Da subunit (alpha subunit) polypeptide of eIF-2 as the substrate. For this purpose, the three subunit polypeptides of eIF-2 (38,000 Da, alpha; 50,000 Da, beta; and 52,000 Da, gamma) were resolved by reversed-phase high performance liquid chromatography (HPLC). Results show that HRI is incapable of phosphorylating the 38,000 Da subunit separated from the other two eIF-2 polypeptides. Data suggest that the substrate specificity of HRI is determined by the quaternary structure assumed by the alpha subunit in association with the other two subunits in the eIF-2 holoprotein.
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30
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31
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Thomas NS, Matts RL, Levin DH, London IM. The 60 S ribosomal subunit as a carrier of eukaryotic initiation factor 2 and the site of reversing factor activity during protein synthesis. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39316-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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32
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Majumdar G, Cashel M, Sharma RK. Expression of autophosphorylating protein kinase 500 in normal and neoplastic rat cells. Proc Natl Acad Sci U S A 1985; 82:5035-9. [PMID: 3860843 PMCID: PMC390493 DOI: 10.1073/pnas.82.15.5035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Autophosphorylating protein kinase 500 (AUT-PK 500) is a unique serine protein kinase that was originally purified and characterized from the rat adrenocortical carcinoma. A specific RIA with an assay sensitivity of 10 ng (0.02 pmol) was developed for AUT-PK 500 and applied to normal, embryonic, fetal, neonatal, immortal, and neoplastic tissues and cultured cells. As compared to normal rat tissues, the expression of AUT-PK 500 is elevated 100-fold in spontaneously occurring adrenocortical carcinoma 494, 50- to 60-fold in four chemically induced, rapidly growing hepatomas, 30-fold in the chemically induced mammary carcinoma, 20-fold in the cultured hepatoma cell line, and 4-fold in the Rat I and Rat II established tissue culture cell lines. There was also a 5-fold increase in the enzyme when freshly cultured rat skin epithelial-like cells were established. Furthermore, in vivo studies showed that when the rat liver was chemically transformed into its premalignant altered foci, there was a 7-fold elevation of AUT-PK 500. Embryonic cells and fetal and neonatal tissues contained barely detectable (less than 0.22 micrograms/mg of protein) amounts of the protein kinase. These results suggest that AUT-PK 500 is not involved in the differentiation process during fetal development but may be elevated during early steps of carcinogenesis and is further elevated during later stages.
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33
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The 90-kDa component of reticulocyte heme-regulated eIF-2 alpha (initiation factor 2 alpha-subunit) kinase is derived from the beta subunit of spectrin. Proc Natl Acad Sci U S A 1985; 82:5332-6. [PMID: 2410920 PMCID: PMC390562 DOI: 10.1073/pnas.82.16.5332] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Antibodies from three different lines of monoclonal hybridomas crossreact with both the beta subunit of spectrin and the 90-kDa peptide present in highly purified preparations of the heme-controlled eIF-2 alpha (initiation factor 2 alpha-subunit) kinase from rabbit reticulocytes. Antibodies from two of the three lines enhance the enzymatic activity of the kinase preparation for phosphorylation of the alpha subunit of eukaryotic translational initiation factor 2 (eIF-2) and for phosphorylation of the 100-kDa peptide thought to be a peptide of the kinase that is phosphorylated during its activation. Also, it is shown that both the beta subunit of spectrin and the 90-kDa peptide can be phosphorylated by two protein kinases from reticulocytes, the catalytic subunit of cAMP-dependent protein kinase and a cAMP-independent protein kinase similar to casein kinase II. Furthermore, a phosphorylated 90-kDa peptide can be derived from phosphorylated beta subunit of spectrin by tryptic proteolysis. We conclude that the 90-kDa peptide is derived by proteolysis from the beta subunit of spectrin, probably from its carboxyl terminus, and suggest that the heme-sensitive eIF-2 alpha kinase, like the 56-kDa phosphatase [Wollny, E., Watkins, K., Kramer, G. & Hardesty, B. (1984) J. Biol. Chem. 259, 2484-2492], is associated with an element of the membrane skeleton in intact reticulocytes.
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Salimans M, Goumans H, Amesz H, Benne R, Voorma HO. Regulation of protein synthesis in eukaryotes. Mode of action of eRF, an eIF-2-recycling factor from rabbit reticulocytes involved in GDP/GTP exchange. EUROPEAN JOURNAL OF BIOCHEMISTRY 1984; 145:91-8. [PMID: 6101245 DOI: 10.1111/j.1432-1033.1984.tb08526.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The rate of initiation of protein synthesis appears to be controlled at the level of recycling of eIF-2. In this process a new factor, designated eRF, plays an important role. The factor has been purified from the post-ribosomal supernatant and has been called formerly anti-HRI and anti-inhibitor [Amesz, H., Goumans, H., Haubrich-Morree, Th., Voorma, H.O., and Benne, R. (1979) Eur. J. Biochem. 98, 513-520]. Its effect on the initiation of protein synthesis has been studied in several assays: a small but distinct effect is found in the assay for the formation of a ternary complex between eIF-2, GTP and Met-tRNA; a 4-5-fold stimulation is obtained in assays for 40S preinitiation complex formation and in the methionyl-puromycin reaction. In the latter assay a catalytic use of eIF-2 occurs provided that eRF is present. eRF forms a complex with eIF-2 which results in a decrease of the affinity of eIF-2 for GDP, giving it the properties of a GDP/GTP exchange factor. The model stresses the catalytic use of eIF-2 in initiation provided that conditions are met for GDP/GTP exchange by a transient complex formation between eIF-2 and eRF. On the other hand, it is shown that phosphorylation of eIF-2 by the hemin-regulated inhibitor (HRI) abolishes the recycling of eIF-2, by the formation of another stable complex comprising eIF-2 alpha P, GDP and eRF.
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35
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Harmon CS, Proud CG, Pain VM. Effects of starvation, diabetes and acute insulin treatment on the regulation of polypeptide-chain initiation in rat skeletal muscle. Biochem J 1984; 223:687-96. [PMID: 6210077 PMCID: PMC1144352 DOI: 10.1042/bj2230687] [Citation(s) in RCA: 74] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The rate of protein synthesis in skeletal muscle is greatly decreased in response to diabetes and starvation. Analysis of polyribosome profiles indicates that polypeptide-chain initiation is impaired under these conditions. To identify the step in initiation that is affected, we assayed the incorporation of [35S]methionyl-tRNAfMet into [35S]methionyl-tRNAfMet . 40S-ribosomal-subunit initiation complexes in cell-free extracts based on postmitochondrial supernatants prepared from gastrocnemius muscle. Extracts from either starved or diabetic rats were 30-40% less active in forming these complexes compared with those derived from fed or insulin-maintained controls respectively. This change could be reversed by treatment of either starved or diabetic rats with insulin in vivo 30 min before death. Formation of 40S initiation complexes by extracts from either fed or starved rats could be stimulated by the addition of exogenous purified initiation factor eIF-2, but extracts from starved or diabetic rats were more sensitive than controls to stimulation by low concentrations of the factor. These results provide evidence for the acute regulation by insulin of protein synthesis in skeletal muscle at the level of polypeptide-chain initiation, and suggest that in this tissue, as in certain other eukaryotic systems, control of initiation appears to be mediated by changes in the activity of initiation factor eIF-2.
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36
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Michelson AM, Ernst V, Levin DH, London IM. Effects of glucose 6-phosphate and hemin on activation of heme-regulated eIF-2 alpha kinase in gel-filtered reticulocyte lysates. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)39762-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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37
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Matts RL, London IM. The regulation of initiation of protein synthesis by phosphorylation of eIF-2(alpha) and the role of reversing factor in the recycling of eIF-2. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)39785-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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38
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Knoller S, Kaempfer R. Isolation of a heme-controlled inhibitor of translation that blocks the interaction between messenger rna and eukaryotic initiation factor 2. Biochemistry 1984; 23:2462-9. [PMID: 6477877 DOI: 10.1021/bi00306a022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A heme-controlled inhibitor of translation was isolated from the S-100 of rabbit reticulocytes by a novel procedure including chromatography on double-stranded ribonucleic acid (dsRNA)-cellulose. The inhibitor thus purified is extremely active and functionally resembles previously studied heme-controlled inhibitor preparations in terms of kinetics and extent of inhibition of translation, relief of inhibition by eukaryotic initiation factor 2 (eIF-2), relief of inhibition by 2-aminopurine, and preferential inhibition of alpha-over beta-globin synthesis. The action of this inhibitor on translation is resistant to treatment with bacterial alkaline phosphatase, micrococcal nuclease, or trypsin and to incubation at 95 degrees C, pH 2 or pH 12. The inhibitor not only is retained on DEAE-cellulose, phosphocellulose, and dsRNA-cellulose but also exhibits a high affinity for the dye Cibacron Blue, properties that suggest that it may be a protein. Unlike previously described heme-controlled inhibitor preparations, or preparations that did not pass over dsRNA-cellulose, the inhibitor recovered upon dsRNA-cellulose chromatography does not exhibit eIF-2 kinase activity. The inhibitor does not block ternary complex formation between eIF-2, methionyl-tRNAfMet, and GTP but inhibits the ability of eIF-2 to form a complex with labeled globin mRNA. In the presence of inhibitor, the formation of mRNA/eIF-2 complexes can be restored effectively by an excess of eIF-2 but not by an excess of mRNA. The inhibitor thus appears to block the interaction between eIF-2 and mRNA not by competing with eIF-2 for a binding site on mRNA but, instead, by acting on eIF-2 itself.(ABSTRACT TRUNCATED AT 250 WORDS)
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Ganguly C, Roberts AN, Kuroda Y, Sharma RK. Rat adrenocortical carcinoma 494 autophosphorylating protein kinase, autophosphorylating protein kinase 500. Purification, biochemical and immunological characterization, and substrate specificity. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(18)91108-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Wahba AJ, Woodley CL. Molecular aspects of development in the brine shrimp Artemia. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1984; 31:221-65. [PMID: 6397772 DOI: 10.1016/s0079-6603(08)60379-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Wu JM, Mosca J, Suhadolnik RJ, Ibrahim NG. Some properties of a partially purified inhibitor(s) of protein synthesis from rat-liver mitochondria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 134:365-70. [PMID: 6873068 DOI: 10.1111/j.1432-1033.1983.tb07576.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We have previously described an inactive inhibitor of protein synthesis from rat liver mitochondria and its activation by brief incubation with N-ethylmaleimide [Wu, J. M. and Ibrahim, N.G. (1980) FEBS Lett. 119, 25-28]. To study the mode of action of the mitochondrial translational inhibitor (MTI), the relative distribution of monosomes and polysomes in rabbit reticulocyte lysates has been analysed by sucrose gradient centrifugation. These studies show that MTI causes a significant decrease in the amount of polysomes with marginal effect on the polysome profile. Under identical experimental conditions, addition of partially purified heme-regulated inhibitor results in a complete disaggregation of polysomes. Studies with micrococcal-nuclease-treated rabbit reticulocyte lysates suggest that the primary target of MTI is the inactivation of globin mRNA with relatively little effect on other components of the translational machinery. The inhibitor also degrades poly(U), vesicular stomatis virus mRNA, reovirus mRNA, but appears to be inactive against poly(A), Escherichia coli 16S rRNA, HeLa cell rRNA or chick embryo DNA. Chromatography of MTI on heparin-agarose results in the resolution of at least two inhibitory activities. The first inhibitory activity (eluted with 250 mM KCl) can be reversed (50-70%) with high concentrations of glucose 6-phosphate or MgGTP (0.7 mM or 3.3 mM) whereas the second inhibitory activity can only be partially reversed with poly(A)-rich RNA.
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Matts RL, Levin DH, London IM. Effect of phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 on the function of reversing factor in the initiation of protein synthesis. Proc Natl Acad Sci U S A 1983; 80:2559-63. [PMID: 6573671 PMCID: PMC393865 DOI: 10.1073/pnas.80.9.2559] [Citation(s) in RCA: 111] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The reticulocyte reversing factor (RF) isolated as a complex with eukaryotic initiation factor 2 (eIF-2) acts catalytically in restoring protein synthesis in reticulocyte lysates inhibited by heme deficiency. In reconstituted in vitro assay mixtures containing Mg2+ (0.25-0.5 mM), RF catalyzes the formation of the binary complex (eIF-2-GDP) but this effect is inhibited when eIF-2 is phosphorylated by the heme-regulated kinase for the alpha-subunit of eIF-2 (HRI). More significantly, RF catalyzes the rapid dissociation of (eIF-2-GDP), which permits the exchange of GTP for GDP and, in the presence of Met-tRNAf, promotes the formation of the ternary complex (eIF-2-Met-tRNAf X GTP). However, phosphorylation of the binary complex by HRI prevents its dissociation by RF and, as a consequence, ternary complex formation is inhibited. Our results indicate that phosphorylated binary complex [eIF-2(alpha P).GDP] interacts with RF to form a [RF . eIF-2(alpha P)] that is not readily dissociable. This binding of RF renders it unavailable to catalyze the dissociation of unphosphorylated binary complex, thereby blocking the recycling of eIF-2. Since RF is present in lysates at a limited concentration relative to that of eIF-2, the sequestering of RF in this manner could account for the observation that the phosphorylation of a small proportion of eIF-2 in heme-deficient lysates is sufficient to inhibit protein synthesis.
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Proud CG, Clemens MJ, Pain VM. Regulation of binding of initiator tRNA to eukaryotic initiation factor eIF-2. Effects of the haem-controlled repressor on the kinetics of ternary complex formation. FEBS Lett 1982; 148:214-20. [PMID: 6924897 DOI: 10.1016/0014-5793(82)80810-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ternary complex formation was studied in reticulocyte lysate supernatants and using rat liver eukaryotic initiation factor-2 (eIF-2) preparations. Haem-deficiency reduced the rate of formation of ternary (Met-tRNAf . GTP . eIF-2) complexes by the eIF-2 in reticulocyte supernatants, the reduction being more marked when complex formation was assayed in the absence of GTP-regenerating capacity. Pretreatment with the haem-controlled repressor (HCR) reduced the rate of ternary complex formation by crude (liver) eIF-2. In contrast, complex formation by an almost homogeneous eIF-2 preparation was unaffected by HCR: sensitivity to HCR was however restored by a factor which catalyses exchange of guanine nucleotides bound to eIF-2.
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Petryshyn R, Levin DH, London IM. Regulation of double-stranded RNA-activated eukaryotic initiation factor 2 alpha kinase by type 2 protein phosphatase in reticulocyte lysates. Proc Natl Acad Sci U S A 1982; 79:6512-6. [PMID: 6292906 PMCID: PMC347157 DOI: 10.1073/pnas.79.21.6512] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Protein synthesis initiation in reticulocyte lysates is inhibited by low concentrations (1-20 ng/ml) of double-stranded RNA (ds RNA) due to the activation of a ds RNA-dependent cAMP-independent protein kinase (ds I) that phosphorylates the alpha subunit of the eukaryotic initiation factor eIF-2. In lysates, ds I is present in the latent inactive form and is associated with the ribosome complement. Latent ds I is solubilized by extraction with high-salt buffers and can be purified in its latent form. Activation of purified latent ds I requires ds RNA and ATP and is accompanied by the ds RNA-dependent autophosphorylation of a polypeptide doublet of 70,000 and 72,000 daltons ("70k/72k"), which represent different phosphorylated states of the same polypeptide. These are phosphorylated in the sequence 70k-->72k; increased phosphorylation of 72k is associated with increased ds I activation. Lysates (or Sepharose 6B ribosomes) treated with ds RNA display a similar ds I phosphoprotein profile, and this is accompanied by the phosphorylation of endogenous eIF-2alpha (38,000 daltons). Delayed (32)P pulses in ds RNA-inhibited lysates indicate that the phosphates on ds I and eIF-2alpha turn over. Under defined conditions, activated ds I in lysates is selectively dephosphorylated by endogenous protein phosphatase(s), and this is accompanied by the dephosphorylation of eIF-2alpha. Similarly, purified activated ds I is rapidly dephosphorylated by unfractionated lysate protein phosphatase(s) and by type 2 protein phosphatase but not by type 1 protein phosphatase. The dephosphorylation of ds I occurs in the sequence 72k-->70k and is correlated with ds I inactivation. The heat-stable protein phosphatase inhibitor-2, which selectively blocks type 1 protein phosphatase, does not significantly affect the dephosphorylation of ds I by type 2 protein phosphatase or by unfractionated lysate phosphatases. The data support the conclusion that a ds I phosphatase activity with type 2 characteristics is involved in the regulation of ds I activity.
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Ranu RS. Regulation of protein synthesis in rabbit reticulocyte lysates: effect of of Ca2+, Mg2+, and Mn2+ on self-phosphorylation and heterophosphorylation catalyzed by the heme-regulated and double-stranded-RNA-activated protein kinases. Biosci Rep 1982; 2:813-7. [PMID: 7171744 DOI: 10.1007/bf01114941] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The influence of divalent cations Mg2+, Mn2+, and Ca2+ on the cyclic-AMP-independent protein kinases of the heme-regulated and double-stranded-RNA-activated translational inhibitory protein kinases on self-phosphorylation and heterophosphorylation of the substrate (the 38 000-dalton subunit of initiation factor eIF-2) has been examined. Results show that Mg2+, Mn2+, and Ca2+ affect the activities of these enzymes in the following fashion. Mg2+ supports both self-phosphorylation and heterophosphorylation efficiently. Mn2+ on the other hand supports self-phosphorylation but to a lesser degree the heterophosphorylation. Ca2+ promotes neither self-phosphorylation nor heterophosphorylation.
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Almiş-Kanigür G, Kan B, Kospançali S, Bermek E. A translational inhibitor activated in rabbit reticulocyte lysates under high pO2. FEBS Lett 1982; 145:143-6. [PMID: 6290264 DOI: 10.1016/0014-5793(82)81223-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
An inhibitor of protein synthesis was activated under high oxygen partial pressure (pO2) in hemin-supplemented and glutathione disulfide-free lysates from rabbit reticulocytes. This inhibitor shared some common features with other translational inhibitors from rabbit reticulocytes; that is, hemin-controlled repressor, glutathione disulfide-activated inhibitor and high pressure-activated inhibitor. It caused biphasic kinetics of inhibition which could be potentiated by ATP. Its activation was prevented by cAMP or glucose 6-phosphate. The high pO2-inhibitor could be partially purified from post-ribosomal supernatant containing ribosomal salt wash by precipitation between 0-50% (NH4)2SO4-saturation, Sephadex G-100, and DEAE-cellulose chromatography.
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Wong ST, Mastropaolo W, Henshaw EC. Differential phosphorylation of soluble versus ribosome-bound eukaryotic initiation factor 2 in the Ehrlich ascites tumor cell. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34660-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Leroux A, London IM. Regulation of protein synthesis by phosphorylation of eukaryotic initiation factor 2 alpha in intact reticulocytes and reticulocyte lysates. Proc Natl Acad Sci U S A 1982; 79:2147-51. [PMID: 6954531 PMCID: PMC346147 DOI: 10.1073/pnas.79.7.2147] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Studies in intact rabbit reticulocytes and reticulocyte lysates provide further evidence of a functional role for the phosphorylation of eukaryotic initiation factor 2 alpha (eIF-2 alpha) in the regulation of initiation of protein synthesis in eukaryotic cells. In intact reticulocytes treated with isonicotinic acid hydrazide to inhibit heme synthesis, the phosphorylation of eIF-2 alpha was significantly greater than in control cells. In heme-deficient reticulocyte lysates and in lysates treated with double-stranded RNA, significant phosphorylation of eIF-2 alpha occurred prior to the onset of inhibition of protein synthesis; a large proportion, however, of the total eIF-2 alpha remained unphosphorylated. These findings indicate that a modest concentration of phosphorylated eIF-2 alpha can suffice to inhibit initiation, and they suggest that one of the factors with which eIF-2 must interact may be rate limiting, especially when eIF-2 alpha is phosphorylated.
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Rittschof D, Traugh JA. Identification of casein kinase II and phosphorylated proteins associated with messenger ribonucleoproteins particles from reticulocytes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 123:333-6. [PMID: 7042340 DOI: 10.1111/j.1432-1033.1982.tb19772.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Messenger ribonucleoprotein (mRNP) particles, isolated from reticulocyte polysomes and purified by buoyant density centrifugation in metrizamide, contained an endogenous protein kinase activity. The cyclic-nucleotide-independent protein kinase phosphorylated casein using either ATP or GTP as the phosphoryl donor and had properties similar to casein kinase II, an enzyme previously purified and characterized from the post-ribosomal supernate of reticulocytes. Antibody prepared to casein kinase II was shown to inhibit the protein kinase activity in the mRNP particles. The endogenous enzyme phosphorylated four peptides (Mr 125 000, 107 000, 76 000 and 63 000) in the mRNP particle. Three of the four peptides, plus another (Mr 175 000), were phosphorylated by purified casein kinase II while two peptides (Mr 95 000 and Mr 76 000) were phosphorylated with casein kinase I. The mRNP particles were not substrates for the cAMP-dependent protein kinases.
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