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Landry C, Costanzo J, Mitne-Neto M, Zatz M, Schaffer A, Hatzoglou M, Muotri A, Miranda HC. Mitochondrial dysfunction heightens the integrated stress response to drive ALS pathogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.594000. [PMID: 38798645 PMCID: PMC11118434 DOI: 10.1101/2024.05.13.594000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Vesicle-associated membrane protein-associated protein-B (VAPB) is an ER membrane bound protein. VAPB P56S causes a dominant, familial form of amyotrophic lateral sclerosis (ALS), however, the mechanism through which this mutation causes motor neuron (MN) disease remains unknown. Using inducible wild type (WT) and VAPB P56S expressing iPSC-derived MNs we show that VAPB P56S, but not WT, protein decreased neuronal firing and mitochondrial-ER contact (MERC) with an associated age-dependent decrease in mitochondrial membrane potential (MMP); all typical characteristics of MN-disease. We further show that VAPB P56S expressing iPSC-derived MNs have enhanced age-dependent sensitivity to ER stress. We identified elevated expression of the master regulator of the Integrated Stress Response (ISR) marker ATF4 and decreased protein synthesis in the VAPB P56S iPSC-derived MNs. Chemical inhibition of ISR with the compound, ISRIB, rescued all MN disease phenotype in VAPB P56S MNs. Thus, our results not only support ISR inhibition as a potential therapeutic target for ALS patients, but also provides evidence to pathogenesis.
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2
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Haakonsen DL, Heider M, Ingersoll AJ, Vodehnal K, Witus SR, Uenaka T, Wernig M, Rapé M. Stress response silencing by an E3 ligase mutated in neurodegeneration. Nature 2024; 626:874-880. [PMID: 38297121 PMCID: PMC10881396 DOI: 10.1038/s41586-023-06985-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Accepted: 12/15/2023] [Indexed: 02/02/2024]
Abstract
Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis, yet their prolonged activation induces apoptosis and disrupts organismal health1-3. How stress responses are turned off at the right time and place remains poorly understood. Here we report a ubiquitin-dependent mechanism that silences the cellular response to mitochondrial protein import stress. Crucial to this process is the silencing factor of the integrated stress response (SIFI), a large E3 ligase complex mutated in ataxia and in early-onset dementia that degrades both unimported mitochondrial precursors and stress response components. By recognizing bifunctional substrate motifs that equally encode protein localization and stability, the SIFI complex turns off a general stress response after a specific stress event has been resolved. Pharmacological stress response silencing sustains cell survival even if stress resolution failed, which underscores the importance of signal termination and provides a roadmap for treating neurodegenerative diseases caused by mitochondrial import defects.
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Affiliation(s)
- Diane L Haakonsen
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Michael Heider
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Andrew J Ingersoll
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Kayla Vodehnal
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Samuel R Witus
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Takeshi Uenaka
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Marius Wernig
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Michael Rapé
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA.
- California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.
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3
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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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4
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Yurttas AG, Okat Z, Elgun T, Cifci KU, Sevim AM, Gul A. Genetic deviation associated with photodynamic therapy in HeLa cell. Photodiagnosis Photodyn Ther 2023; 42:103346. [PMID: 36809810 DOI: 10.1016/j.pdpdt.2023.103346] [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: 11/18/2022] [Revised: 02/05/2023] [Accepted: 02/14/2023] [Indexed: 02/22/2023]
Abstract
Photodynamic therapy (PDT) is a method that is used in cancer treatment. The main therapeutic effect is the production of singlet oxygen (1O2). Phthalocyanines for PDT produce high singlet oxygen with absorbers of about 600-700 nm. AIM It is aimed to analyze cancer cell pathways by flow cytometry analysis and cancer-related genes with q-PCR device by applying phthalocyanine L1ZnPC, which we use as photosensitizer in photodynamic therapy, in HELA cell line. In this study, we investigate the molecular basis of L1ZnPC's anti-cancer activity. MATERIAL METHOD The cytotoxic effects of L1ZnPC, a phthalocyanine obtained from our previous study, in HELA cells were evaluated and it was determined that it led to a high rate of death as a result. The result of photodynamic therapy was analyzed using q-PCR. From the data received at the conclusion of this investigation, gene expression values were calculated, and expression levels were assessed using the 2-∆∆Ct method to examine the relative changes in these values. Cell death pathways were interpreted with the FLOW cytometer device. One-Way Analysis of Variance (ANOVA) and the Tukey-Kramer Multiple Comparison Test with Post-hoc Test were used for the statistical analysis. CONCLUSION In our study, it was observed that HELA cancer cells underwent apoptosis at a rate of 80% with drug application plus photodynamic therapy by flow cytometry method. According to q-PCR results, CT values of eight out of eighty-four genes were found to be significant and their association with cancer was evaluated. L1ZnPC is a new phthalocyanine used in this study and our findings should be supported by further studies. For this reason, different analyses are needed to be performed with this drug in different cancer cell lines. In conclusion, according to our results, this drug looks promising but still needs to be analyzed through new studies. It is necessary to examine in detail which signaling pathways they use and their mechanism of action. For this, additional experiments are required.
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Affiliation(s)
- Asiye Gok Yurttas
- Department of Biochemistry, Faculty of Pharmacy, Istanbul Health and Technology University, Istanbul, Turkey.
| | - Zehra Okat
- Department of Biochemistry, Faculty of Medicine, Marmara University, Istanbul, Turkey
| | - Tugba Elgun
- Medical Biology, Faculty of Medicine, Istanbul Biruni University, Istanbul, Turkey
| | - Kezban Ucar Cifci
- Division of Basic Sciences and Health, Hemp Research Institute, Yozgat Bozok University, Yozgat, Turkey; Department of Molecular Medicine, Institute of Health Sciences, University of Health Sciences, Turkey
| | - Altug Mert Sevim
- Department of Chemistry, Istanbul Technical University, Istanbul, Turkey
| | - Ahmet Gul
- Department of Chemistry, Istanbul Technical University, Istanbul, Turkey
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5
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Ricketts MD, Emptage RP, Blobel GA, Marmorstein R. The Heme-Regulated Inhibitor Kinase Requires Dimerization for Heme- Sensing Activity. J Biol Chem 2022; 298:102451. [PMID: 36063997 PMCID: PMC9520036 DOI: 10.1016/j.jbc.2022.102451] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 08/17/2022] [Accepted: 08/19/2022] [Indexed: 11/24/2022] Open
Abstract
The heme-regulated inhibitor (HRI) is a heme-sensing kinase that regulates mRNA translation in erythroid cells. In heme deficiency, HRI is activated to phosphorylate eukaryotic initiation factor 2α and halt production of globins, thus avoiding accumulation of heme-free globin chains. HRI is inhibited by heme via binding to one or two heme-binding domains within the HRI N-terminal and kinase domains. HRI has recently been found to inhibit fetal hemoglobin (HbF) production in adult erythroid cells. Depletion of HRI increases HbF production, presenting a therapeutically exploitable target for the treatment of patients with sickle cell disease or thalassemia, which benefit from elevated HbF levels. HRI is known to be an oligomeric enzyme that is activated through autophosphorylation, although the exact nature of the HRI oligomer, its relation to autophosphorylation, and its mode of heme regulation remain unclear. Here, we employ biochemical and biophysical studies to demonstrate that HRI forms a dimeric species that is not dependent on autophosphorylation, the C-terminal coiled-coil domain in HRI is essential for dimer formation, and dimer formation facilitates efficient autophosphorylation and activation of HRI. We also employ kinetic studies to demonstrate that the primary avenue by which heme inhibits HRI is through the heme-binding site within the kinase domain, and that this inhibition is relatively independent of binding of ATP and eukaryotic initiation factor 2α substrates. Together, these studies highlight the mode of heme inhibition and the importance of dimerization in human HRI heme-sensing activity.
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Affiliation(s)
- M Daniel Ricketts
- Department of Biochemistry and Biophysics and the Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Ryan P Emptage
- Department of Biochemistry and Biophysics and the Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Gerd A Blobel
- Division of Hematology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Ronen Marmorstein
- Department of Biochemistry and Biophysics and the Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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6
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Kalkavan H, Chen MJ, Crawford JC, Quarato G, Fitzgerald P, Tait SWG, Goding CR, Green DR. Sublethal cytochrome c release generates drug-tolerant persister cells. Cell 2022; 185:3356-3374.e22. [PMID: 36055199 PMCID: PMC9450215 DOI: 10.1016/j.cell.2022.07.025] [Citation(s) in RCA: 63] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 04/29/2022] [Accepted: 07/26/2022] [Indexed: 12/19/2022]
Abstract
Drug-tolerant persister cells (persisters) evade apoptosis upon targeted and conventional cancer therapies and represent a major non-genetic barrier to effective cancer treatment. Here, we show that cells that survive treatment with pro-apoptotic BH3 mimetics display a persister phenotype that includes colonization and metastasis in vivo and increased sensitivity toward ferroptosis by GPX4 inhibition. We found that sublethal mitochondrial outer membrane permeabilization (MOMP) and holocytochrome c release are key requirements for the generation of the persister phenotype. The generation of persisters is independent of apoptosome formation and caspase activation, but instead, cytosolic cytochrome c induces the activation of heme-regulated inhibitor (HRI) kinase and engagement of the integrated stress response (ISR) with the consequent synthesis of ATF4, all of which are required for the persister phenotype. Our results reveal that sublethal cytochrome c release couples sublethal MOMP to caspase-independent initiation of an ATF4-dependent, drug-tolerant persister phenotype.
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Affiliation(s)
- Halime Kalkavan
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mark J Chen
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jeremy C Crawford
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Giovanni Quarato
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Patrick Fitzgerald
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Stephen W G Tait
- Cancer Research UK Beatson Institute, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Switchback Road, Glasgow G61 1BD, UK
| | - Colin R Goding
- Ludwig Institute for Cancer Research, Nuffield Department of Clinical Medicine, University of Oxford, Headington, Oxford OX37DQ, UK
| | - Douglas R Green
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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7
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Yerlikaya A. Heme-regulated inhibitor: an overlooked eIF2α kinase in cancer investigations. Med Oncol 2022; 39:73. [PMID: 35568791 DOI: 10.1007/s12032-022-01668-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 01/24/2022] [Indexed: 10/18/2022]
Abstract
Heme-regulated inhibitor (HRI) kinase is a serine-threonine kinase, controlling the initiation of protein synthesis via phosphorylating α subunit of eIF2 on serine 51 residue, mainly in response to heme deprivation in erythroid cells. However, recent studies showed that HRI is also activated by several diverse signals, causing dysregulations in intracellular homeostatic mechanisms in non-erythroid cells. For instance, it was reported that the decrease in protein synthesis upon the 26S proteasomal inhibition by MG132 or bortezomib is mediated by increased eIF2α phosphorylation in an HRI-dependent manner in mouse embryonic fibroblast cells. The increase in eIF2α phosphorylation level through the activation of HRI upon 26S proteasomal inhibition is believed to protect cells against the buildup of misfolded and ubiquitinated proteins, having the potential to trigger the apoptotic response. In contrast, prolonged and sustained HRI-mediated eIF2α phosphorylation can induce cell death, which may involve ATF4 and CHOP expression. Altogether, these studies suggest that HRI-mediated eIF2α phosphorylation may be cytoprotective or cytotoxic depending on the cells, type, and duration of pharmacological agents used. It is thus hypothesized that both HRI activators, inducing eIF2α phosphorylation or HRI inhibitors causing disturbances in eIF2α phosphorylation, may be effective as novel strategies in cancer treatment if the balance in eIF2α phosphorylation is shifted in favor of autophagic or apoptotic response in cancer cells. It is here aimed to review the role of HRI in various biological mechanisms as well as the therapeutic potentials of recently developed HRI activators and inhibitors, targeting eIF2α phosphorylation in cancer cells.
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Affiliation(s)
- Azmi Yerlikaya
- Department of Medical Biology, Faculty of Medicine, Kutahya Health Sciences University, Kutahya, Turkey.
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8
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Abstract
PURPOSE OF REVIEW HRI is the heme-regulated elF2α kinase that phosphorylates the α-subunit of elF2. Although the role of HRI in inhibiting globin synthesis in erythroid cells is well established, broader roles of HRI in translation have been uncovered recently. This review is to summarize the new discoveries of HRI in stress erythropoiesis and in fetal γ-globin expression. RECENT FINDINGS HRI and activating transcription factor 4 (ATF4) mRNAs are highly expressed in early erythroblasts. Inhibition of protein synthesis by HRI-phosphorylated elF2α (elF2αP) is necessary to maintain protein homeostasis in both the cytoplasm and mitochondria. In addition, HRI-elF2αP specifically enhances translation of ATF4 mRNA leading to the repression of mechanistic target of rapamycin complex 1 (mTORC1) signaling. ATF4-target genes are most highly activated during iron deficiency to maintain mitochondrial function, redox homeostasis, and to enable erythroid differentiation. HRI is therefore a master translation regulator of erythropoiesis sensing intracellular heme concentrations and oxidative stress for effective erythropoiesis. Intriguingly, HRI-elF2αP-ATF4 signaling also inhibits fetal hemoglobin production in human erythroid cells. SUMMARY The primary function of HRI is to maintain protein homeostasis accompanied by the induction of ATF4 to mitigate stress. Role of HRI-ATF4 in γ-globin expression raises the potential of HRI as a therapeutic target for hemoglobinopathy.
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Affiliation(s)
- Jane-Jane Chen
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Shuping Zhang
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250062, China
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9
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Sensing, signaling and surviving mitochondrial stress. Cell Mol Life Sci 2021; 78:5925-5951. [PMID: 34228161 PMCID: PMC8316193 DOI: 10.1007/s00018-021-03887-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 06/15/2021] [Accepted: 06/22/2021] [Indexed: 12/11/2022]
Abstract
Mitochondrial fidelity is a key determinant of longevity and was found to be perturbed in a multitude of disease contexts ranging from neurodegeneration to heart failure. Tight homeostatic control of the mitochondrial proteome is a crucial aspect of mitochondrial function, which is severely complicated by the evolutionary origin and resulting peculiarities of the organelle. This is, on one hand, reflected by a range of basal quality control factors such as mitochondria-resident chaperones and proteases, that assist in import and folding of precursors as well as removal of aggregated proteins. On the other hand, stress causes the activation of several additional mechanisms that counteract any damage that may threaten mitochondrial function. Countermeasures depend on the location and intensity of the stress and on a range of factors that are equipped to sense and signal the nature of the encountered perturbation. Defective mitochondrial import activates mechanisms that combat the accumulation of precursors in the cytosol and the import pore. To resolve proteotoxic stress in the organelle interior, mitochondria depend on nuclear transcriptional programs, such as the mitochondrial unfolded protein response and the integrated stress response. If organelle damage is too severe, mitochondria signal for their own destruction in a process termed mitophagy, thereby preventing further harm to the mitochondrial network and allowing the cell to salvage their biological building blocks. Here, we provide an overview of how different types and intensities of stress activate distinct pathways aimed at preserving mitochondrial fidelity.
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10
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Kitajima S, Sun W, Lee KL, Ho JC, Oyadomari S, Okamoto T, Masai H, Poellinger L, Kato H. A KDM6 inhibitor potently induces ATF4 and its target gene expression through HRI activation and by UTX inhibition. Sci Rep 2021; 11:4538. [PMID: 33633164 PMCID: PMC7907191 DOI: 10.1038/s41598-021-83857-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 02/01/2021] [Indexed: 01/31/2023] Open
Abstract
UTX/KDM6A encodes a major histone H3 lysine 27 (H3K27) demethylase, and is frequently mutated in various types of human cancers. Although UTX appears to play a crucial role in oncogenesis, the mechanisms involved are still largely unknown. Here we show that a specific pharmacological inhibitor of H3K27 demethylases, GSK-J4, induces the expression of transcription activating factor 4 (ATF4) protein as well as the ATF4 target genes (e.g. PCK2, CHOP, REDD1, CHAC1 and TRIB3). ATF4 induction by GSK-J4 was due to neither transcriptional nor post-translational regulation. In support of this view, the ATF4 induction was almost exclusively dependent on the heme-regulated eIF2α kinase (HRI) in mouse embryonic fibroblasts (MEFs). Gene expression profiles with UTX disruption by CRISPR-Cas9 editing and the following stable re-expression of UTX showed that UTX specifically suppresses the expression of the ATF4 target genes, suggesting that UTX inhibition is at least partially responsible for the ATF4 induction. Apoptosis induction by GSK-J4 was partially and cell-type specifically correlated with the activation of ATF4-CHOP. These findings highlight that the anti-cancer drug candidate GSK-J4 strongly induces ATF4 and its target genes via HRI activation and raise a possibility that UTX might modulate cancer formation by regulating the HRI-ATF4 axis.
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Affiliation(s)
- Shojiro Kitajima
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore ,grid.26091.3c0000 0004 1936 9959Institute for Advanced Biosciences, Keio University, Kakuganji 246-2, Mizukami, Tsuruoka, Yamagata 997-0052 Japan
| | - Wendi Sun
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore
| | - Kian Leong Lee
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore ,grid.428397.30000 0004 0385 0924Cancer & Stem Cell Biology Programme, Duke-NUS Medical School, 8 College Road, Singapore, 169857 Republic of Singapore
| | - Jolene Caifeng Ho
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore
| | - Seiichi Oyadomari
- grid.267335.60000 0001 1092 3579Institute of Advanced Medical Sciences, Tokushima University, Tokushima, 770-8503 Japan
| | - Takashi Okamoto
- grid.260433.00000 0001 0728 1069Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Science, Mizuho-ku, Nagoya, 467-8601 Japan
| | - Hisao Masai
- grid.272456.0Genome Dynamics Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506 Japan
| | - Lorenz Poellinger
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore ,Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Hiroyuki Kato
- grid.4280.e0000 0001 2180 6431Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore, 117599 Republic of Singapore ,grid.260433.00000 0001 0728 1069Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Science, Mizuho-ku, Nagoya, 467-8601 Japan ,grid.272456.0Genome Dynamics Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506 Japan
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11
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Reovirus and the Host Integrated Stress Response: On the Frontlines of the Battle to Survive. Viruses 2021; 13:v13020200. [PMID: 33525628 PMCID: PMC7910986 DOI: 10.3390/v13020200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/22/2021] [Accepted: 01/26/2021] [Indexed: 12/17/2022] Open
Abstract
Cells are continually exposed to stressful events, which are overcome by the activation of a number of genetic pathways. The integrated stress response (ISR) is a large component of the overall cellular response to stress, which ultimately functions through the phosphorylation of the alpha subunit of eukaryotic initiation factor-2 (eIF2α) to inhibit the energy-taxing process of translation. This response is instrumental in the inhibition of viral infection and contributes to evolution in viruses. Mammalian orthoreovirus (MRV), an oncolytic virus that has shown promise in over 30 phase I–III clinical trials, has been shown to induce multiple arms within the ISR pathway, but it successfully evades, modulates, or subverts each cellular attempt to inhibit viral translation. MRV has not yet received Food and Drug Administration (FDA) approval for general use in the clinic; therefore, researchers continue to study virus interactions with host cells to identify circumstances where MRV effectiveness in tumor killing can be improved. In this review, we will discuss the ISR, MRV modulation of the ISR, and discuss ways in which MRV interaction with the ISR may increase the effectiveness of cancer therapeutics whose modes of action are altered by the ISR.
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12
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Bond S, Lopez-Lloreda C, Gannon PJ, Akay-Espinoza C, Jordan-Sciutto KL. The Integrated Stress Response and Phosphorylated Eukaryotic Initiation Factor 2α in Neurodegeneration. J Neuropathol Exp Neurol 2020; 79:123-143. [PMID: 31913484 DOI: 10.1093/jnen/nlz129] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 11/07/2019] [Indexed: 02/06/2023] Open
Abstract
The proposed molecular mechanisms underlying neurodegenerative pathogenesis are varied, precluding the development of effective therapies for these increasingly prevalent disorders. One of the most consistent observations across neurodegenerative diseases is the phosphorylation of eukaryotic initiation factor 2α (eIF2α). eIF2α is a translation initiation factor, involved in cap-dependent protein translation, which when phosphorylated causes global translation attenuation. eIF2α phosphorylation is mediated by 4 kinases, which, together with their downstream signaling cascades, constitute the integrated stress response (ISR). While the ISR is activated by stresses commonly observed in neurodegeneration, such as oxidative stress, endoplasmic reticulum stress, and inflammation, it is a canonically adaptive signaling cascade. However, chronic activation of the ISR can contribute to neurodegenerative phenotypes such as neuronal death, memory impairments, and protein aggregation via apoptotic induction and other maladaptive outcomes downstream of phospho-eIF2α-mediated translation inhibition, including neuroinflammation and altered amyloidogenic processing, plausibly in a feed-forward manner. This review examines evidence that dysregulated eIF2a phosphorylation acts as a driver of neurodegeneration, including a survey of observations of ISR signaling in human disease, inspection of the overlap between ISR signaling and neurodegenerative phenomenon, and assessment of recent encouraging findings ameliorating neurodegeneration using developing pharmacological agents which target the ISR. In doing so, gaps in the field, including crosstalk of the ISR kinases and consideration of ISR signaling in nonneuronal central nervous system cell types, are highlighted.
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Affiliation(s)
- Sarah Bond
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Claudia Lopez-Lloreda
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Patrick J Gannon
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Cagla Akay-Espinoza
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Kelly L Jordan-Sciutto
- From the Department of Biochemistry and Biophysics (SB); Department of Neuroscience (CL-L); Department of Pharmacology (PG), Perelman School of Medicine; Department of Basic and Translational Sciences (CA-E); and Department of Basic and Translational Sciences (KLJ-S), School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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13
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Heme-regulated eIF2α kinase in erythropoiesis and hemoglobinopathies. Blood 2020; 134:1697-1707. [PMID: 31554636 DOI: 10.1182/blood.2019001915] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 09/11/2019] [Indexed: 12/12/2022] Open
Abstract
As essential components of hemoglobin, iron and heme play central roles in terminal erythropoiesis. The impairment of this process in iron/heme deficiency results in microcytic hypochromic anemia, the most prevalent anemia globally. Heme-regulated eIF2α kinase, also known as heme-regulated inhibitor (HRI), is a key heme-binding protein that senses intracellular heme concentrations to balance globin protein synthesis with the amount of heme available for hemoglobin production. HRI is activated during heme deficiency to phosphorylate eIF2α (eIF2αP), which simultaneously inhibits the translation of globin messenger RNAs (mRNAs) and selectively enhances the translation of activating transcription factor 4 (ATF4) mRNA to induce stress response genes. This coordinated translational regulation is a universal hallmark across the eIF2α kinase family under various stress conditions and is termed the integrated stress response (ISR). Inhibition of general protein synthesis by HRI-eIF2αP in erythroblasts is necessary to prevent proteotoxicity and maintain protein homeostasis in the cytoplasm and mitochondria. Additionally, the HRI-eIF2αP-ATF4 pathway represses mechanistic target of rapamycin complex 1 (mTORC1) signaling, specifically in the erythroid lineage as a feedback mechanism of erythropoietin-stimulated erythropoiesis during iron/heme deficiency. Furthermore, ATF4 target genes are most highly activated during iron deficiency to maintain mitochondrial function and redox homeostasis, as well as to enable erythroid differentiation. Thus, heme and translation regulate erythropoiesis through 2 key signaling pathways, ISR and mTORC1, which are coordinated by HRI to circumvent ineffective erythropoiesis (IE). HRI-ISR is also activated to reduce the severity of β-thalassemia intermedia in the Hbbth1/th1 murine model. Recently, HRI has been implicated in the regulation of human fetal hemoglobin production. Therefore, HRI-ISR has emerged as a potential therapeutic target for hemoglobinopathies.
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Ifhar LS, Ene HM, Ben-Shachar D. Impaired heme metabolism in schizophrenia-derived cell lines and in a rat model of the disorder: Possible involvement of mitochondrial complex I. Eur Neuropsychopharmacol 2019; 29:577-589. [PMID: 30948194 DOI: 10.1016/j.euroneuro.2019.03.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 03/18/2019] [Accepted: 03/22/2019] [Indexed: 02/07/2023]
Abstract
Accumulating data point to heme involvement in neuropsychiatric disorders. Heme plays a role in major cellular processes such as signal transduction, protein complex assembly and regulation of transcription and translation. Its synthesis involves the mitochondria, which dysfunction, specifically that of the complex I (Co-I) of the electron transport chain is involved in the pathophysiology of schizophrenia (SZ). Here we aimed to demonstrate that deficits in Co-I affect heme metabolism. We show a significant decrease in heme levels in Co-I deficient SZ-derived EBV transformed lymphocytes (lymphoblastoid cell lines - LCLs) as compared to healthy subjects-derived cells (n = 9/cohort). Moreover, protein levels assessed by immunoblotting and mRNA levels assessed by qRT-PCR of heme catabolic enzyme, heme Oxygenase 1 (HO-1), and protein levels of heme downstream target phosphorylated eukaryotic initiation factor 2-alpha (Peif2a/eif2a) were significantly elevated in SZ-derived cells. In contrast, protein and mRNA levels of heme synthesis rate limiting enzyme aminolevulinic acid synthase-1 (ALAS1) were unchanged in SZ derived LCLs. In addition, inhibition of Co-I by rotenone in healthy subjects-derived LCLs (n = 4/cohort) exhibited an initial increase followed by a later decrease in heme levels. These findings were associated with opposite changes in heme's downstream target and HO-1 level, similar to our findings in SZ-derived cells. We also show a brain region specific pattern of impairment in Co-I subunits and in HO-1 and PeIF2α/eIF2α in the Poly-IC rat model of SZ (n = 6/cohort). Our results provide evidence for a link between CoI and heme metabolism both in-vitro and in-vivo suggesting its contribution to SZ pathophysiology.
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Affiliation(s)
- Lee S Ifhar
- Laboratory of Psychobiology, Department of Psychiatry, Rambam Health Care Campus, B. Rappaport Faculty of Medicine, Rappaport Family Institute for Research in Medical Sciences, Technion IIT, POB 9649, Haifa 31096 Israel
| | - Hila M Ene
- Laboratory of Psychobiology, Department of Psychiatry, Rambam Health Care Campus, B. Rappaport Faculty of Medicine, Rappaport Family Institute for Research in Medical Sciences, Technion IIT, POB 9649, Haifa 31096 Israel
| | - Dorit Ben-Shachar
- Laboratory of Psychobiology, Department of Psychiatry, Rambam Health Care Campus, B. Rappaport Faculty of Medicine, Rappaport Family Institute for Research in Medical Sciences, Technion IIT, POB 9649, Haifa 31096 Israel.
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Mimura J, Inose-Maruyama A, Taniuchi S, Kosaka K, Yoshida H, Yamazaki H, Kasai S, Harada N, Kaufman RJ, Oyadomari S, Itoh K. Concomitant Nrf2- and ATF4-activation by Carnosic Acid Cooperatively Induces Expression of Cytoprotective Genes. Int J Mol Sci 2019; 20:ijms20071706. [PMID: 30959808 PMCID: PMC6480217 DOI: 10.3390/ijms20071706] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 03/29/2019] [Accepted: 03/30/2019] [Indexed: 12/12/2022] Open
Abstract
Carnosic acid (CA) is a phytochemical found in some dietary herbs, such as Rosmarinus officinalis L., and possesses antioxidative and anti-microbial properties. We previously demonstrated that CA functions as an activator of nuclear factor, erythroid 2 (NF-E2)-related factor 2 (Nrf2), an oxidative stress-responsive transcription factor in human and rodent cells. CA enhances the expression of nerve growth factor (NGF) and antioxidant genes, such as HO-1 in an Nrf2-dependent manner in U373MG human astrocytoma cells. However, CA also induces NGF gene expression in an Nrf2-independent manner, since 50 μM of CA administration showed striking NGF gene induction compared with the classical Nrf2 inducer tert-butylhydroquinone (tBHQ) in U373MG cells. By comparative transcriptome analysis, we found that CA activates activating transcription factor 4 (ATF4) in addition to Nrf2 at high doses. CA activated ATF4 in phospho-eIF2α- and heme-regulated inhibitor kinase (HRI)-dependent manners, indicating that CA activates ATF4 through the integrated stress response (ISR) pathway. Furthermore, CA activated Nrf2 and ATF4 cooperatively enhanced the expression of NGF and many antioxidant genes while acting independently to certain client genes. Taken together, these results represent a novel mechanism of CA-mediated gene regulation evoked by Nrf2 and ATF4 cooperation.
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Affiliation(s)
- Junsei Mimura
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
| | - Atsushi Inose-Maruyama
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
- Department of Microbiology, Tohoku Medical and Pharmaceutical University, Sendai 981-8558, Japan.
| | - Shusuke Taniuchi
- Division of Molecular Biology, Institute of Advanced Medical Sciences, The University of Tokushima, Tokushima 770-8503, Japan.
| | - Kunio Kosaka
- Research and Development Center, Nagase & Co. Ltd., Kobe 651-2241, Japan.
| | - Hidemi Yoshida
- Department of Vascular Biology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
| | - Hiromi Yamazaki
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
| | - Shuya Kasai
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
| | - Nobuhiko Harada
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
- Institute for Animal Experimentation, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan.
| | - Randal J Kaufman
- Degenerative Diseases Research Program, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla, CA 92037, USA.
| | - Seiichi Oyadomari
- Division of Molecular Biology, Institute of Advanced Medical Sciences, The University of Tokushima, Tokushima 770-8503, Japan.
| | - Ken Itoh
- Department of Stress Response Science, Center for Advanced Medical Research, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
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HRI coordinates translation by eIF2αP and mTORC1 to mitigate ineffective erythropoiesis in mice during iron deficiency. Blood 2017; 131:450-461. [PMID: 29101239 DOI: 10.1182/blood-2017-08-799908] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 11/01/2017] [Indexed: 01/08/2023] Open
Abstract
Iron deficiency (ID) anemia is a prevalent disease, yet molecular mechanisms by which iron and heme regulate erythropoiesis are not completely understood. Heme-regulated eIF2α kinase (HRI) is a key hemoprotein in erythroid precursors that sense intracellular heme concentrations to balance globin synthesis with the amount of heme available for hemoglobin production. HRI is activated by heme deficiency and oxidative stress, and it phosphorylates eIF2α (eIF2αP), which inhibits the translation of globin messenger RNAs (mRNAs) and selectively enhances the translation of activating transcription factor 4 (ATF4) mRNA to induce stress response genes. Here, we generated a novel mouse model (eAA) with the erythroid-specific ablation of eIF2αP and demonstrated that eIF2αP is required for induction of ATF4 protein synthesis in vivo in erythroid cells during ID. We show for the first time that both eIF2αP and ATF4 are necessary to promote erythroid differentiation and to reduce oxidative stress in vivo during ID. Furthermore, the HRI-eIF2αP-ATF4 pathway suppresses mTORC1 signaling specifically in the erythroid lineage. Pharmacologic inhibition of mTORC1 significantly increased red blood cell counts and hemoglobin content in the blood, improved erythroid differentiation, and reduced splenomegaly of iron-deficient Hri-/- and eAA mice. However, globin inclusions and elevated oxidative stress remained, demonstrating the essential nonredundant role of HRI-eIF2αP in these processes. Dietary iron repletion completely reversed ID anemia and ineffective erythropoiesis of Hri-/- , eAA, and Atf4-/- mice by inhibiting both HRI and mTORC1 signaling. Thus, HRI coordinates 2 key translation-regulation pathways, eIF2αP and mTORC1, to circumvent ineffective erythropoiesis, highlighting heme and translation in the regulation of erythropoiesis.
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Bhavnani V, Kaviraj S, Panigrahi P, Suresh CG, Yapara S, Pal J. Elucidation of molecular mechanism of stability of the heme-regulated eIF2α kinase upon binding of its ligand, hemin in its catalytic kinase domain. J Biomol Struct Dyn 2017; 36:2845-2861. [PMID: 28814160 DOI: 10.1080/07391102.2017.1368417] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The eIF2α kinase activity of the heme-regulated inhibitor (HRI) is regulated by heme which makes it a unique member of the family of eIF2α kinases. Since heme concentrations create an equilibrium for the kinase to be active/inactive, it becomes important to study the heme binding effects upon the kinase and understanding its mechanism of functionality. In the present study, we report the thermostability achieved by the catalytic kinase domain of HRI (HRI.CKD) upon ligand (heme) binding. Our CD data demonstrates that the HRI.CKD retains its secondary structure at higher temperatures when it is in ligand bound state. HRI.CKD when incubated with hemin loses its monomeric state and attains a higher order oligomeric form resulting in its stability. The HRI.CKD fails to refold into its native conformation upon mutation of H377A/H381A, thereby confirming the necessity of these His residues for correct folding, stability, and activity of the kinase. Though our in silico study demonstrated these His being the ligand binding sites in the kinase insert region, the spectra-based study did not show significant difference in heme affinity for the wild type and His mutant HRI.CKD.
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Affiliation(s)
- Varsha Bhavnani
- a Department of Biotechnology , Savitribai Phule Pune University , Pune , Maharashtra 411007 , India
| | - Swarnendu Kaviraj
- b Vaccine Formulation & Research Centre , Gennova Biopharmaceuticals Limited , Pune , Maharashtra 411057 , India
| | - Priyabrata Panigrahi
- c Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune 411008 , India
| | - C G Suresh
- c Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune 411008 , India
| | - SuneelShekar Yapara
- b Vaccine Formulation & Research Centre , Gennova Biopharmaceuticals Limited , Pune , Maharashtra 411057 , India
| | - Jayanta Pal
- a Department of Biotechnology , Savitribai Phule Pune University , Pune , Maharashtra 411007 , India
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Bhavnani V, Swarnendu K, Savergave L, Raghuwanshi AS, Kumar A, Kumar A, Pal J. HRI, a stress response eIF2α kinase, exhibits structural and functional stability at high temperature and alkaline conditions. Int J Biol Macromol 2016; 95:528-538. [PMID: 27888007 DOI: 10.1016/j.ijbiomac.2016.11.071] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 01/20/2023]
Abstract
The Heme Regulated Inhibitor (HRI) is a key regulator of protein synthesis in mammalian cells. Once activated under heme-deficiency and other stress conditions, it phosphorylates the α subunit of eukaryotic initiation factor 2 (eIF2α) leading to inhibition of protein synthesis. In the present study, our objective was to establish the structural and functional credentials of this kinase so as to qualify it as a stress responsive eIF2α kinase. When the catalytic kinase domain of the HRI (HRI.CKD) protein was subjected to high temperature, 45°C (above mammalian heat shock temperature), it could still phosphorylate the substrate, indicating its potential as a stress response kinase. At a temperature beyond 45°C, loss in secondary structure of the HRI.CKD is attributable to loss of its function. Furthermore, no significant structural changes were observed at the broad pH range of 3.0--10.0. The HRI.CKD incubated at any pH between 8.0-10.0, exhibited more than 60% of its kinase activity, demonstrating structural and functional stability of the kinase at an alkaline pH. These data taken together establish that the structural stability of this kinase at high temperature and alkaline conditions is due to conservation of its secondary structure and that the resulting functional activity qualifies this kinase as a stress responsive kinase.
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Affiliation(s)
- Varsha Bhavnani
- Department of Biotechnology, Savitribai Phule Pune University, Pune, Maharashtra 411007, India
| | - Kaviraj Swarnendu
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Laxman Savergave
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Arjun Singh Raghuwanshi
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Ankit Kumar
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Avinash Kumar
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Jayanta Pal
- Department of Biotechnology, Savitribai Phule Pune University, Pune, Maharashtra 411007, India.
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Biology of Heme in Mammalian Erythroid Cells and Related Disorders. BIOMED RESEARCH INTERNATIONAL 2015; 2015:278536. [PMID: 26557657 PMCID: PMC4628764 DOI: 10.1155/2015/278536] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 06/14/2015] [Indexed: 01/19/2023]
Abstract
Heme is a prosthetic group comprising ferrous iron (Fe(2+)) and protoporphyrin IX and is an essential cofactor in various biological processes such as oxygen transport (hemoglobin) and storage (myoglobin) and electron transfer (respiratory cytochromes) in addition to its role as a structural component of hemoproteins. Heme biosynthesis is induced during erythroid differentiation and is coordinated with the expression of genes involved in globin formation and iron acquisition/transport. However, erythroid and nonerythroid cells exhibit distinct differences in the heme biosynthetic pathway regulation. Defects of heme biosynthesis in developing erythroblasts can have profound medical implications, as represented by sideroblastic anemia. This review will focus on the biology of heme in mammalian erythroid cells, including the heme biosynthetic pathway as well as the regulatory role of heme and human disorders that arise from defective heme synthesis.
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Activation of SsoPK4, an Archaeal eIF2α Kinase Homolog, by Oxidized CoA. Proteomes 2015; 3:89-116. [PMID: 28248264 PMCID: PMC5217372 DOI: 10.3390/proteomes3020089] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 04/30/2015] [Accepted: 05/05/2015] [Indexed: 01/08/2023] Open
Abstract
The eukaryotic protein kinase (ePK) paradigm provides integral components for signal transduction cascades throughout nature. However, while so-called typical ePKs permeate the Eucarya and Bacteria, atypical ePKs dominate the kinomes of the Archaea. Intriguingly, the catalytic domains of the handful of deduced typical ePKs from the archaeon Sulfolobus solfataricus P2 exhibit significant resemblance to the protein kinases that phosphorylate translation initiation factor 2α (eIF2α) in response to cellular stresses. We cloned and expressed one of these archaeal eIF2α protein kinases, SsoPK4. SsoPK4 exhibited protein-serine/threonine kinase activity toward several proteins, including the S. solfataricus homolog of eIF2α, aIF2α. The activity of SsoPK4 was inhibited in vitro by 3ʹ,5ʹ-cyclic AMP (Ki of ~23 µM) and was activated by oxidized Coenzyme A, an indicator of oxidative stress in the Archaea. Activation enhanced the apparent affinity for protein substrates, Km, but had little effect on Vmax. Autophosphorylation activated SsoPK4 and rendered it insensitive to oxidized Coenzyme A.
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Donnelly N, Gorman AM, Gupta S, Samali A. The eIF2α kinases: their structures and functions. Cell Mol Life Sci 2013; 70:3493-511. [PMID: 23354059 PMCID: PMC11113696 DOI: 10.1007/s00018-012-1252-6] [Citation(s) in RCA: 587] [Impact Index Per Article: 53.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 12/16/2012] [Accepted: 12/20/2012] [Indexed: 01/02/2023]
Abstract
Cell signaling in response to an array of diverse stress stimuli converges on the phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2). Phosphorylation of eIF2α on serine 51 results in a severe decline in de novo protein synthesis and is an important strategy in the cell's armory against stressful insults including viral infection, the accumulation of misfolded proteins, and starvation. The phosphorylation of eIF2α is carried out by a family of four kinases, PERK (PKR-like ER kinase), PKR (protein kinase double-stranded RNA-dependent), GCN2 (general control non-derepressible-2), and HRI (heme-regulated inhibitor). Each primarily responds to a distinct type of stress or stresses. Thus, while significant sequence similarity exists between the eIF2α kinases in their kinase domains, underlying their common role in phosphorylating eIF2α, additional unique features determine the regulation of these four proteins, that is, what signals activate them. This review will describe the structure of each eIF2α kinase and discuss how this is linked to their activation and function. In parallel to the general translational attenuation elicited by eIF2α kinase activation the translation of stress-induced mRNAs, most notably activating transcription factor 4 (ATF4) is enhanced and these set in motion cascades of gene expression constituting the integrated stress response (ISR), which seek to remediate stress and restore homeostasis. Depending on the cellular context and concurrent signaling pathways active, however, translational attenuation can also facilitate apoptosis. Accordingly, the role of the kinases in determining cell fate will also be discussed.
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Affiliation(s)
- Neysan Donnelly
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
- Present Address: Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, Munich, 82152 Germany
| | - Adrienne M. Gorman
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Sanjeev Gupta
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Medicine, National University of Ireland, Galway, Ireland
| | - Afshin Samali
- Apoptosis Research Center, National University of Ireland, Galway, Ireland
- School of Natural Sciences, National University of Ireland, Galway, Ireland
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Park SH, Moon Y. Integrated stress response-altered pro-inflammatory signals in mucosal immune-related cells. Immunopharmacol Immunotoxicol 2012; 35:205-14. [PMID: 23237490 DOI: 10.3109/08923973.2012.742535] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Various cells are associated with the integrated stress response (ISR) that leads to translation arrest via phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2. Pathogenic insults or nutritional imbalance in the mucosal tissues including the intestinal, airway, and genitourinary epithelia can cause ISRs, which have been linked to different mucosal inflammatory responses and subsequent systemic diseases. In particular, translational arrest caused by the early recognition of luminal microbes as well as nutritional status allows the human body to mount appropriate responses and maintain homeostasis both at the cellular and systemic levels. However, an over- or reduced ISR can create pathogenic conditions such as inflammation and carcinogenesis. This present review explores the association between eIF2α kinase-linked pathways and mucosal or systemic pro-inflammatory signals activated by xenobiotic insults (such as ones caused by microbes or nutritional abnormalities). Understanding ISR-modulated cellular alterations will provide progressive insights into approaches for treating human mucosal inflammatory and metabolic disorders.
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Affiliation(s)
- Seong-Hwan Park
- Laboratory of Mucosal Exposome and Biomodulation, Department of Microbiology and Immunology, Pusan National University School of Medicine, Yangsan, South Korea
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Dalton LE, Healey E, Irving J, Marciniak SJ. Phosphoproteins in stress-induced disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 106:189-221. [PMID: 22340719 DOI: 10.1016/b978-0-12-396456-4.00003-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The integrated stress response (ISR) is an evolutionarily conserved homeostatic program activated by specific pathological states. These include amino acid deprivation, viral infection, iron deficiency, and the misfolding of proteins within the endoplasmic reticulum (ER), the so-called ER stress. Although apparently disparate, each of these stresses induces phosphorylation of a translation initiation factor, eIF2α, to attenuate new protein translation while simultaneously triggering a transcriptional program. This is achieved by four homologous stress-sensing kinases: GCN2, PKR, HRI, and PERK. In addition to these kinases, mammals possess two specific eIF2α phosphatases, GADD34 and CReP, which play crucial roles in the recovery of protein synthesis following the initial insult. They are not only important in embryonic development but also appear to play important roles in disease, particularly cancer. In this chapter, we discuss each of the eIF2α kinases, in turn, with particular emphasis on their regulation and the new insights provided by recent structural studies. We also discuss the potential for developing novel drug therapies that target the ISR.
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Affiliation(s)
- Lucy E Dalton
- Division of Respiratory Medicine, Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Cambridge, United Kingdom
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Igarashi J, Sasaki T, Kobayashi N, Yoshioka S, Matsushita M, Shimizu T. Autophosphorylation of heme-regulated eukaryotic initiation factor 2α kinase and the role of the modification in catalysis. FEBS J 2011; 278:918-28. [DOI: 10.1111/j.1742-4658.2011.08007.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Correia MA, Sinclair PR, De Matteis F. Cytochrome P450 regulation: the interplay between its heme and apoprotein moieties in synthesis, assembly, repair, and disposal. Drug Metab Rev 2010; 43:1-26. [PMID: 20860521 DOI: 10.3109/03602532.2010.515222] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Heme is vital to our aerobic universe. Heme cellular content is finely tuned through an exquisite control of synthesis and degradation. Heme deficiency is deleterious to cells, whereas excess heme is toxic. Most of the cellular heme serves as the prosthetic moiety of functionally diverse hemoproteins, including cytochromes P450 (P450s). In the liver, P450s are its major consumers, with >50% of hepatic heme committed to their synthesis. Prosthetic heme is the sine qua non of P450 catalytic biotransformation of both endo- and xenobiotics. This well-recognized functional role notwithstanding, heme also regulates P450 protein synthesis, assembly, repair, and disposal. These less well-appreciated aspects are reviewed herein.
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Affiliation(s)
- Maria Almira Correia
- Department of Cellular and Molecular Pharmacology, The Liver Center, University of California, San Francisco, 94158, USA.
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Wiley DJ, Shrestha N, Yang J, Atis N, Dayton K, Schesser K. The activities of the Yersinia protein kinase A (YpkA) and outer protein J (YopJ) virulence factors converge on an eIF2alpha kinase. J Biol Chem 2009; 284:24744-53. [PMID: 19553678 PMCID: PMC2757178 DOI: 10.1074/jbc.m109.010140] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 06/22/2009] [Indexed: 12/23/2022] Open
Abstract
The Yersinia protein kinase A (YpkA) and outer protein J (YopJ) are co-expressed from a single transcript and are injected directly into eukaryotic cells by the plague bacterium Yersinia pestis. When overexpressed in vertebrate or yeast cells, YpkA disrupts the actin-based cytoskeletal system by an unknown mechanism, whereas YopJ obstructs inductive chemokine expression by inhibiting MAPK and NF-kappaB signaling. Previously, we showed that the fission yeast Schizosaccharomyces pombe was sensitive to the kinase activity of YpkA. Here, we screened yeast for cellular processes important for YpkA activity and found that the eIF2alpha kinases mollify the toxicity imparted by the kinase activity of YpkA. Specifically, strains lacking the eIF2alpha kinase Hri2 were particularly sensitive to YpkA. Unexpectedly, the activity of YopJ, which conferred a phenotype consistent with its inhibitory effect on MAPK signaling, was also found to be dependent on Hri2. When expressed in S. pombe, YopJ sensitized cells to osmotic and oxidative stresses through a Hri2-dependent mechanism. However, when co-expressed with YpkA, YopJ protected cells from YpkA-mediated toxicity, and this protection was entirely dependent on Hri2. In contrast, YopJ did not confer protection against the toxic effects of the Yersinia virulence factor YopE. These findings are the first to functionally link YpkA and YopJ and suggest that eIF2alpha kinases, which are critically important in antiviral defenses and protection against environmental stresses, also play a role in bacterial virulence.
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Affiliation(s)
- David J. Wiley
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Niraj Shrestha
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Jing Yang
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Nadege Atis
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Kevin Dayton
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Kurt Schesser
- From the Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida 33136
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27
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Lászlí CF, Wu S. Old target new approach: an alternate NF-kappaB activation pathway via translation inhibition. Mol Cell Biochem 2009; 328:9-16. [PMID: 19224334 PMCID: PMC2740372 DOI: 10.1007/s11010-009-0067-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 02/05/2009] [Indexed: 11/24/2022]
Abstract
Activation of the transcription factor NF-kappaB is a highly regulated multi-level process. The critical step during activation is the release from its inhibitor IkappaB, which as any other protein is under the direct influence of translation regulation. In this review, we summarize in detail the current understanding of the impact of translational regulation on NF-kappaB activation. We illustrate a newly developed mechanism of eIF2alpha kinase-mediated IkappaB depletion and subsequent NF-kappaB activation. We also show that the classical NF-kappaB activation pathways occur simultaneously with, and are complemented by, translational down regulation of the inhibitor molecule IkappaB, the importance of one or the other being shifted in accordance with the type and magnitude of the stressing agent or stimuli.
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Affiliation(s)
- Csaba F. Lászlí
- Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH 45701, USA
| | - Shiyong Wu
- Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH 45701, USA
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28
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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: 142] [Impact Index Per Article: 8.4] [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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29
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Chen JJ. Regulation of protein synthesis by the heme-regulated eIF2alpha kinase: relevance to anemias. Blood 2007; 109:2693-9. [PMID: 17110456 PMCID: PMC1852217 DOI: 10.1182/blood-2006-08-041830] [Citation(s) in RCA: 229] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During erythroid differentiation and maturation, it is critical that the 3 components of hemoglobin, alpha-globin, beta-globin, and heme, are made in proper stoichiometry to form stable hemoglobin. Heme-regulated translation mediated by the heme-regulated inhibitor kinase (HRI) provides one major mechanism that ensures balanced synthesis of globins and heme. HRI phosphorylates the alpha-subunit of eukaryotic translational initiation factor 2 (eLF2alpha) in heme deficiency, thereby inhibiting protein synthesis globally. In this manner, HRI serves as a feedback inhibitor of globin synthesis by sensing the intracellular concentration of heme through its heme-binding domains. HRI is essential not only for the translational regulation of globins, but also for the survival of erythroid precursors in iron deficiency. Recently, the protective function of HRI has also been demonstrated in murine models of erythropoietic protoporphyria and beta-thalassemia. In these 3 anemias, HRI is essential in determining red blood cell size, number, and hemoglobin content per cell. Translational regulation by HRI is critical to reduce excess synthesis of globin proteins or heme under nonoptimal disease states, and thus reduces the severity of these diseases. The protective role of HRI may be more common among red cell disorders.
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Affiliation(s)
- Jane-Jane Chen
- Harvard-Massachusetts Institute of Technology (MIT) Division of Health Sciences and Technology (HST), MIT, Cambridge, MA 02139, USA.
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30
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Mense SM, Zhang L. Heme: a versatile signaling molecule controlling the activities of diverse regulators ranging from transcription factors to MAP kinases. Cell Res 2006; 16:681-92. [PMID: 16894358 DOI: 10.1038/sj.cr.7310086] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Heme (iron protoporphyrin IX) is an essential molecule for numerous living organisms. Not only does it serve as a prosthetic group in enzymes, it also acts as a signaling molecule that controls diverse molecular and cellular processes ranging from signal transduction to protein complex assembly. Deficient heme synthesis or function impacts the hematopoietic, hepatic and nervous systems in humans. Recent studies have revealed a series of heme-regulated transcription factors and signal transducers including Hap1, a heme-activated transcription factor that mediates the effects of oxygen on gene transcription in the yeast Saccharomyces cerevisiae; Bach1, a transcriptional repressor that is negatively regulated by heme in mammalian cells; IRR, an iron regulatory protein that mediates the iron-dependant regulation of heme synthesis in the bacterium Bradyrhizobium japonicum; and heme-regulated inhibitor, an eucaryotic initiation factor 2alpha kinase that coordinates protein synthesis with heme availability in reticulocytes. In this review, we summarize the current knowledge about how heme controls the activity of these transcriptional regulators and signal transducers, and discuss diseases associated with defective heme synthesis, degradation and function.
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Affiliation(s)
- Sarah M Mense
- Department of Environmental Health Sciences, Columbia University, Mailman School of Public Health, New York, NY 10032, USA
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31
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Patterson AD, Hollander MC, Miller GF, Fornace AJ. Gadd34 requirement for normal hemoglobin synthesis. Mol Cell Biol 2006; 26:1644-53. [PMID: 16478986 PMCID: PMC1430266 DOI: 10.1128/mcb.26.5.1644-1653.2006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein encoded by growth arrest and DNA damage-inducible transcript 34 (Gadd34) is associated with translation initiation regulation following certain stress responses. Through interaction with the protein phosphatase 1 catalytic subunit (PP1c), Gadd34 recruits PP1c for the removal of an inhibitory phosphate group on the alpha subunit of elongation initiation factor 2, thereby reversing the shutoff of protein synthesis initiated by stress-inducible kinases. In the absence of stress, the physiologic consequences of Gadd34 function are not known. Initial analysis of Gadd34-null mice revealed several significant findings, including hypersplenism, decreased erythrocyte volume, increased numbers of circulating erythrocytes, and decreased hemoglobin content, resembling some thalassemia syndromes. Biochemical analysis of the hemoglobin-producing reticulocyte (an erythrocyte precursor) revealed that the decreased hemoglobin content in the Gadd34-null erythrocyte is due to the reduced initiation of the globin translation machinery. We propose that an equilibrium state exists between Gadd34/PP1c and the opposing heme-regulated inhibitor kinase during hemoglobin synthesis in the reticulocyte.
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Affiliation(s)
- Andrew D Patterson
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115, USA
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32
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Dar AC, Dever TE, Sicheri F. Higher-order substrate recognition of eIF2alpha by the RNA-dependent protein kinase PKR. Cell 2005; 122:887-900. [PMID: 16179258 DOI: 10.1016/j.cell.2005.06.044] [Citation(s) in RCA: 292] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 05/03/2005] [Accepted: 06/28/2005] [Indexed: 11/18/2022]
Abstract
In response to binding viral double-stranded RNA byproducts within a cell, the RNA-dependent protein kinase PKR phosphorylates the alpha subunit of the translation initiation factor eIF2 on a regulatory site, Ser51. This triggers the general shutdown of protein synthesis and inhibition of viral propagation. To understand the basis for substrate recognition by and the regulation of PKR, we determined X-ray crystal structures of the catalytic domain of PKR in complex with eIF2alpha. The structures reveal that eIF2alpha binds to the C-terminal catalytic lobe while catalytic-domain dimerization is mediated by the N-terminal lobe. In addition to inducing a local unfolding of the Ser51 acceptor site in eIF2alpha, its mode of binding to PKR affords the Ser51 site full access to the catalytic cleft of PKR. The generality and implications of the structural mechanisms uncovered for PKR to the larger family of four human eIF2alpha protein kinases are discussed.
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Affiliation(s)
- Arvin C Dar
- Program in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
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33
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Yun BG, Matts JAB, Matts RL. Interdomain interactions regulate the activation of the heme-regulated eIF2α kinase. Biochim Biophys Acta Gen Subj 2005; 1725:174-81. [PMID: 16109458 DOI: 10.1016/j.bbagen.2005.07.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Revised: 07/25/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
The heme-regulated inhibitor of protein synthesis (HRI) regulates translation through the phosphorylation of the alpha-subunit of eukaryotic initiation factor-2 (eIF 2). While HRI is best known for its activation in response to heme-deficiency, we recently showed that the binding of NO and CO to the N-terminal heme-binding domain (NT-HBD) of HRI activated and suppressed its activity, respectively. Here, we examined the effect of hemin, NO, and CO on the interaction between the NT-HBD and the catalytic domain of HRI (HRI/Delta HBD). Hemin stabilized the interaction of NT-HBD with HRI/Delta HBD, and NO and CO disrupted and stabilized this interaction, respectively. Mutant HRI (Delta H-HRI), lacking amino acids 116-158 from the NT-HBD, was less sensitive to heme-induced inhibition, and mutant NT-HBD lacking these residues did not bind to HRI/Delta HBD. HRI/Delta HBD and Delta H-HRI also activated more readily than HRI in response to heme-deficiency. Thus, HRI's activity is regulated through the modulation of the interaction between its NT-HBD and catalytic domain.
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Affiliation(s)
- Bo-Geon Yun
- Department of Biochemistry and Molecular Biology, Oklahoma State University, 246 NRC, Stillwater, OK 74078-3035, USA
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34
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Han AP, Fleming MD, Chen JJ. Heme-regulated eIF2alpha kinase modifies the phenotypic severity of murine models of erythropoietic protoporphyria and beta-thalassemia. J Clin Invest 2005; 115:1562-70. [PMID: 15931390 PMCID: PMC1136998 DOI: 10.1172/jci24141] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2004] [Accepted: 03/16/2005] [Indexed: 12/31/2022] Open
Abstract
Heme-regulated eIF2alpha kinase (HRI) controls protein synthesis by phosphorylating the alpha-subunit of eukaryotic translational initiation factor 2 (eIF2alpha). In heme deficiency, HRI is essential for translational regulation of alpha- and beta-globins and for the survival of erythroid progenitors. HRI is also activated by a number of cytoplasmic stresses other than heme deficiency, including oxidative stress and heat shock. However, to date, HRI has not been implicated in the pathogenesis of any known human disease or mouse phenotype. Here we report the essential role of HRI in 2 mouse models of human rbc disorders, namely erythropoietic protoporphyria (EPP) and beta-thalassemia. In both cases, lack of HRI adversely modifies the phenotype: HRI deficiency exacerbates EPP and renders beta-thalassemia embryonically lethal. This study establishes the protective function of HRI in inherited rbc diseases in mice and suggests that HRI may be a significant modifier of many rbc disorders in humans. Our findings also demonstrate that translational regulation could play a critical role in the clinical manifestation of rbc diseases.
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Affiliation(s)
- An-Ping Han
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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35
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Igarashi J, Sato A, Kitagawa T, Yoshimura T, Yamauchi S, Sagami I, Shimizu T. Activation of heme-regulated eukaryotic initiation factor 2alpha kinase by nitric oxide is induced by the formation of a five-coordinate NO-heme complex: optical absorption, electron spin resonance, and resonance raman spectral studies. J Biol Chem 2004; 279:15752-62. [PMID: 14752110 DOI: 10.1074/jbc.m310273200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Heme-regulated eukaryotic initiation factor 2alpha kinase (HRI) regulates the synthesis of hemoglobin in reticulocytes in response to heme availability. HRI contains a tightly bound heme at the N-terminal domain. Earlier reports show that nitric oxide (NO) regulates HRI catalysis. However, the mechanism of this process remains unclear. In the present study, we utilize in vitro kinase assays, optical absorption, electron spin resonance (ESR), and resonance Raman spectra of purified full-length HRI for the first time to elucidate the regulation mechanism of NO. HRI was activated via heme upon NO binding, and the Fe(II)-HRI(NO) complex displayed 5-fold greater eukaryotic initiation factor 2alpha kinase activity than the Fe(III)-HRI complex. The Fe(III)-HRI complex exhibited a Soret peak at 418 nm and a rhombic ESR signal with g values of 2.49, 2.28, and 1.87, suggesting coordination with Cys as an axial ligand. Interestingly, optical absorption, ESR, and resonance Raman spectra of the Fe(II)-NO complex were characteristic of five-coordinate NO-heme. Spectral findings on the coordination structure of full-length HRI were distinct from those obtained for the isolated N-terminal heme-binding domain. Specifically, six-coordinate NO-Fe(II)-His was observed but not Cys-Fe(III) coordination. It is suggested that significant conformational change(s) in the protein induced by NO binding to the heme lead to HRI activation. We discuss the role of NO and heme in catalysis by HRI, focusing on heme-based sensor proteins.
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Affiliation(s)
- Jotaro Igarashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
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36
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Lee HC, Hon T, Lan C, Zhang L. Structural environment dictates the biological significance of heme-responsive motifs and the role of Hsp90 in the activation of the heme activator protein Hap1. Mol Cell Biol 2003; 23:5857-66. [PMID: 12897155 PMCID: PMC166322 DOI: 10.1128/mcb.23.16.5857-5866.2003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Heme-responsive motifs (HRMs) mediate heme regulation of diverse regulatory proteins. The heme activator protein Hap1 contains seven HRMs, but only one of them, HRM7, is essential for heme activation of Hap1. To better understand the molecular basis underlying the biological significance of HRMs, we examined the effects of various mutations of HRM7 on Hap1. We found that diverse mutations of HRM7 significantly diminished the extent of Hap1 activation by heme and moderately enhanced the interaction of Hap1 with Hsp90. Furthermore, deletions of nonregulatory sequences completely abolished heme activation of Hap1 and greatly enhanced the interaction of Hap1 with Hsp90. These results show that the biological functions of HRMs and Hsp90 are highly sensitive to structural changes. The unique role of HRM7 in heme activation stems from its specific structural environment, not its mere presence. Likewise, the role of Hsp90 in Hap1 activation is dictated by the conformational or structural state of Hap1, not by the mere strength of Hap1-Hsp90 interaction. It appears likely that HRM7 and Hsp90 act together to promote the Hap1 conformational changes that are necessary for Hap1 activation. Such fundamental mechanisms of HRM-Hsp90 cooperation may operate in diverse regulatory systems to mediate signal transduction.
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Affiliation(s)
- Hee Chul Lee
- Department of Biochemistry, NYU School of Medicine, New York, New York 10016, USA
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37
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Rafie-Kolpin M, Han AP, Chen JJ. Autophosphorylation of threonine 485 in the activation loop is essential for attaining eIF2alpha kinase activity of HRI. Biochemistry 2003; 42:6536-44. [PMID: 12767237 DOI: 10.1021/bi034005v] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In heme deficiency, protein synthesis is inhibited by the activation of the heme-regulated eIF2alpha kinase (HRI) through its multiple autophosphorylation. Autophosphorylation sites in HRI were identified in order to investigate their functions. We found that there were eight major tryptic phosphopeptides of HRI activated in heme deficiency. In this report we focused on the role of autophosphorylation at Thr483 and Thr485 in the activation loop of HRI. Disruption of the autophosphorylation of Thr485, but not Thr483, resulted in a lower autokinase activity and locked Thr485Ala HRI in a hypophosphorylated state. Most importantly, autophosphorylation of Thr485, but not Thr483, was essential for attaining eIF2alpha kinase activity of HRI. In addition, autophosphorylation of Thr485 was necessary for arsenite-induced activation of the eIF2alpha kinase activity of HRI, while autophosphorylation at Thr483 was not required for activation by arsenite. The function of Thr490, another conserved Thr residue in the activation loop of HRI, was also investigated. Mutations of Thr490 to either Ala or Asp resulted in reduced autokinase activity and loss of eIF2alpha kinase activity in heme deficiency or upon arsenite treatment. Since Thr490 was not identified as an autophosphorylated site, it is likely that Thr490 itself might be critical for the catalytic activity of HRI. Importantly, Thr485 was very poorly phosphorylated in Thr490 mutant HRI. Collectively, our results demonstrate that autophosphorylation of Thr485 is essential for the hyperphosphorylation and activation of HRI and is required for the acquisition of the eIF2alpha kinase activity.
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Affiliation(s)
- Maryam Rafie-Kolpin
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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38
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Zhan K, Vattem KM, Bauer BN, Dever TE, Chen JJ, Wek RC. Phosphorylation of eukaryotic initiation factor 2 by heme-regulated inhibitor kinase-related protein kinases in Schizosaccharomyces pombe is important for fesistance to environmental stresses. Mol Cell Biol 2002; 22:7134-46. [PMID: 12242291 PMCID: PMC139816 DOI: 10.1128/mcb.22.20.7134-7146.2002] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein synthesis is regulated by the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) in response to different environmental stresses. One member of the eIF2alpha kinase family, heme-regulated inhibitor kinase (HRI), is activated under heme-deficient conditions and blocks protein synthesis, principally globin, in mammalian erythroid cells. We identified two HRI-related kinases from Schizosaccharomyces pombe which have full-length homology with mammalian HRI. The two HRI-related kinases, named Hri1p and Hri2p, exhibit autokinase and kinase activity specific for Ser-51 of eIF2alpha, and both activities were inhibited in vitro by hemin, as previously described for mammalian HRI. Overexpression of Hri1p, Hri2p, or the human eIF2alpha kinase, double-stranded-RNA-dependent protein kinase (PKR), impeded growth of S. pombe due to elevated phosphorylation of eIF2alpha. Cells from strains with deletions of the hri1(+) and hri2(+) genes, individually or in combination, exhibited a reduced growth rate when exposed to heat shock or to arsenic compounds. Measurements of in vivo phosphorylation of eIF2alpha suggest that Hri1p and Hri2p differentially phosphorylate eIF2alpha in response to these stress conditions. These results demonstrate that HRI-related enzymes are not unique to vertebrates and suggest that these eIF2alpha kinases are important participants in diverse stress response pathways in some lower eukaryotes.
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Affiliation(s)
- Ke Zhan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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39
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Lu L, Han AP, Chen JJ. Translation initiation control by heme-regulated eukaryotic initiation factor 2alpha kinase in erythroid cells under cytoplasmic stresses. Mol Cell Biol 2001; 21:7971-80. [PMID: 11689689 PMCID: PMC99965 DOI: 10.1128/mcb.21.23.7971-7980.2001] [Citation(s) in RCA: 241] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytoplasmic stresses, including heat shock, osmotic stress, and oxidative stress, cause rapid inhibition of protein synthesis in cells through phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) by eIF2alpha kinases. We have investigated the role of heme-regulated inhibitor (HRI), a heme-regulated eIF2alpha kinase, in stress responses of erythroid cells. We have demonstrated that HRI in reticulocytes and fetal liver nucleated erythroid progenitors is activated by oxidative stress induced by arsenite, heat shock, and osmotic stress but not by endoplasmic reticulum stress or nutrient starvation. While autophosphorylation is essential for the activation of HRI, the phosphorylation status of HRI activated by different stresses is different. The contributions of HRI in various stress responses were assessed with the aid of HRI-null reticulocytes and fetal liver erythroid cells. HRI is the only eIF2alpha kinase activated by arsenite in erythroid cells, since HRI-null cells do not induce eIF2alpha phosphorylation upon arsenite treatment. HRI is also the major eIF2alpha kinase responsible for the increased eIF2alpha phosphorylation upon heat shock in erythroid cells. Activation of HRI by these stresses is independent of heme and requires the presence of intact cells. Both hsp90 and hsc70 are necessary for all stress-induced HRI activation. However, reactive oxygen species are involved only in HRI activation by arsenite. Our results provide evidence for a novel function of HRI in stress responses other than heme deficiency.
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Affiliation(s)
- L Lu
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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