1
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Misra J, Carlson KR, Spandau DF, Wek RC. Multiple mechanisms activate GCN2 eIF2 kinase in response to diverse stress conditions. Nucleic Acids Res 2024; 52:1830-1846. [PMID: 38281137 PMCID: PMC10899773 DOI: 10.1093/nar/gkae006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 12/22/2023] [Accepted: 01/02/2024] [Indexed: 01/30/2024] Open
Abstract
Diverse environmental insults induce the integrated stress response (ISR), which features eIF2 phosphorylation and translational control that serves to restore protein homeostasis. The eIF2 kinase GCN2 is a first responder in the ISR that is activated by amino acid depletion and other stresses not directly related to nutrients. Two mechanisms are suggested to trigger an ordered process of GCN2 activation during stress: GCN2 monitoring stress via accumulating uncharged tRNAs or by stalled and colliding ribosomes. Our results suggest that while ribosomal collisions are indeed essential for GCN2 activation in response to translational elongation inhibitors, conditions that trigger deacylation of tRNAs activate GCN2 via its direct association with affected tRNAs. Both mechanisms require the GCN2 regulatory domain related to histidyl tRNA synthetases. GCN2 activation by UV irradiation features lowered amino acids and increased uncharged tRNAs and UV-induced ribosome collisions are suggested to be dispensable. We conclude that there are multiple mechanisms that activate GCN2 during diverse stresses.
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Affiliation(s)
- Jagannath Misra
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
| | - Kenneth R Carlson
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
| | - Dan F Spandau
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
- Department of Dermatology, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
- Richard L. Roudebush Veterans Administration Medical Center, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
| | - Ronald C Wek
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS4067 Indianapolis, Indiana 46202, USA
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2
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Rowland MB, Moore PE, Correll RN. Regulation of cardiac fibroblast cell death by unfolded protein response signaling. Front Physiol 2024; 14:1304669. [PMID: 38283278 PMCID: PMC10811265 DOI: 10.3389/fphys.2023.1304669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/21/2023] [Indexed: 01/30/2024] Open
Abstract
The endoplasmic reticulum (ER) is a tightly regulated organelle that requires specific environmental properties to efficiently carry out its function as a major site of protein synthesis and folding. Embedded in the ER membrane, ER stress sensors inositol-requiring enzyme 1 (IRE1), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6) serve as a sensitive quality control system collectively known as the unfolded protein response (UPR). In response to an accumulation of misfolded proteins, the UPR signals for protective mechanisms to cope with the cellular stress. Under prolonged unstable conditions and an inability to regain homeostasis, the UPR can shift from its original adaptive response to mechanisms leading to UPR-induced apoptosis. These UPR signaling pathways have been implicated as an important feature in the development of cardiac fibrosis, but identifying effective treatments has been difficult. Therefore, the apoptotic mechanisms of UPR signaling in cardiac fibroblasts (CFs) are important to our understanding of chronic fibrosis in the heart. Here, we summarize the maladaptive side of the UPR, activated downstream pathways associated with cell death, and agents that have been used to modify UPR-induced apoptosis in CFs.
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Affiliation(s)
- Mary B. Rowland
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, United States
| | - Patrick E. Moore
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, United States
| | - Robert N. Correll
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, United States
- Center for Convergent Bioscience and Medicine, University of Alabama, Tuscaloosa, AL, United States
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3
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Bahamondes Lorca VA, Wu S. Ultraviolet Light, Unfolded Protein Response and Autophagy †. Photochem Photobiol 2023; 99:498-508. [PMID: 36591940 DOI: 10.1111/php.13777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 12/22/2022] [Indexed: 01/03/2023]
Abstract
The endoplasmic reticulum (ER) plays an important role in the regulation of protein synthesis. Alterations in the folding capacity of the ER induce stress, which activates three ER sensors that mediate the unfolded protein response (UPR). Components of the pathways regulated by these sensors have been shown to regulate autophagy. The last corresponds to a mechanism of self-eating and recycling important for proper cell maintenance. Ultraviolet radiation (UV) is an external damaging stimulus that is known for inducing oxidative stress, and DNA, lipid and protein damage. Many controversies exist regarding the role of UV-inducing ER stress or autophagy. However, a connection between the three of them has not been addressed. In this review, we will discuss the contradictory theories regarding the relationships between UV radiation with the induction of ER stress and autophagy, as well as hypothetic connections between UV, ER stress and autophagy.
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Affiliation(s)
- Verónica A Bahamondes Lorca
- Edison Biotechnology Institute, Ohio University, Athens, OH.,Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Shiyong Wu
- Edison Biotechnology Institute, Ohio University, Athens, OH.,Department of Chemistry and Biochemistry, Ohio University, Athens, OH
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4
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Son J, Mogre S, Chalmers FE, Ibinson J, Worrell S, Glick AB. The Endoplasmic Reticulum Stress Sensor IRE1α Regulates the UV DNA Repair Response through the Control of Intracellular Calcium Homeostasis. J Invest Dermatol 2021; 142:1682-1691.e7. [PMID: 34808241 DOI: 10.1016/j.jid.2021.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 10/28/2021] [Accepted: 11/02/2021] [Indexed: 12/24/2022]
Abstract
The unfolded protein response is activated by UVB irradiation, but the role of a key mediator, IRE1α, is not clear. In this study, we show that mice with an epidermal IRE1α deletion are sensitized to UV with increased apoptosis, rapid loss of UV-induced cyclopyrimidine dimer‒positive keratinocytes, and sloughing of the epidermis. In vitro, Ire1α-deficient keratinocytes have increased UVB sensitivity, reduced cyclopyrimidine dimer repair, and reduced accumulation of γH2AX and phosphorylated ATR, suggesting defective activation of nucleotide excision repair. Knockdown of XBP1 or pharmacologic inhibition of the IRE1α ribonuclease did not phenocopy Ire1α deficiency. The altered UV response was linked to elevated intracellular calcium levels and ROS, and this was due to dysregulation of the endoplasmic reticulum calcium channel InsP3R. Pharmacologic, genetic, and biochemical studies linked the regulation of the Ins3PR, intracellular calcium, and normal UV DNA damage response to CIB1 and the IRE1α‒TRAF2‒ASK1 complex. These results suggest a model where IRE1α activation state drives CIB1 binding either to the InsP3R or ASK1 to regulate endoplasmic reticulum calcium efflux, ROS, and DNA repair responses after UV irradiation.
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Affiliation(s)
- Jeongin Son
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA
| | - Saie Mogre
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA
| | - Fiona E Chalmers
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA
| | - Jack Ibinson
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA
| | - Stephen Worrell
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA
| | - Adam B Glick
- Department of Veterinary and Biomedical Sciences, College of Agricultural Sciences, The Pennsylvania State University, Pennsylvania, USA.
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5
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Miles RR, Amin PH, Diaz MB, Misra J, Aukerman E, Das A, Ghosh N, Guith T, Knierman MD, Roy S, Spandau DF, Wek RC. The eIF2 kinase GCN2 directs keratinocyte collective cell migration during wound healing via coordination of reactive oxygen species and amino acids. J Biol Chem 2021; 297:101257. [PMID: 34597669 PMCID: PMC8554533 DOI: 10.1016/j.jbc.2021.101257] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/20/2021] [Accepted: 09/27/2021] [Indexed: 12/25/2022] Open
Abstract
Healing of cutaneous wounds requires the collective migration of epithelial keratinocytes to seal the wound bed from the environment. However, the signaling events that coordinate this collective migration are unclear. In this report, we address the role of phosphorylation of eukaryotic initiation factor 2 (eIF2) and attendant gene expression during wound healing. Wounding of human keratinocyte monolayers in vitro led to the rapid activation of the eIF2 kinase GCN2. We determined that deletion or pharmacological inhibition of GCN2 significantly delayed collective cell migration and wound closure. Global transcriptomic, biochemical, and cellular analyses indicated that GCN2 is necessary for maintenance of intracellular free amino acids, particularly cysteine, as well as coordination of RAC1-GTP-driven reactive oxygen species (ROS) generation, lamellipodia formation, and focal adhesion dynamics following keratinocyte wounding. In vivo experiments using mice deficient for GCN2 validated the role of the eIF2 kinase during wound healing in intact skin. These results indicate that GCN2 is critical for appropriate induction of collective cell migration and plays a critical role in coordinating the re-epithelialization of cutaneous wounds.
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Affiliation(s)
- Rebecca R Miles
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Parth H Amin
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Miguel Barriera Diaz
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Jagannath Misra
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Erica Aukerman
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Amitava Das
- Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA; Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Nandini Ghosh
- Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA; Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Tanner Guith
- Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA; Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael D Knierman
- Laboratory for Experimental Medicine, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Sashwati Roy
- Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA; Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Dan F Spandau
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Richard L. Roudebush Veterans Administration Medical Center, Indianapolis, Indiana, USA.
| | - Ronald C Wek
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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6
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Wójcik P, Gęgotek A, Žarković N, Skrzydlewska E. Disease-Dependent Antiapoptotic Effects of Cannabidiol for Keratinocytes Observed upon UV Irradiation. Int J Mol Sci 2021; 22:ijms22189956. [PMID: 34576119 PMCID: PMC8470797 DOI: 10.3390/ijms22189956] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 08/28/2021] [Accepted: 09/11/2021] [Indexed: 01/14/2023] Open
Abstract
Although apoptosis of keratinocytes has been relatively well studied, there is a lack of information comparing potentially proapoptotic treatments for healthy and diseased skin cells. Psoriasis is a chronic autoimmune-mediated skin disease manifested by patches of hyperproliferative keratinocytes that do not undergo apoptosis. UVB phototherapy is commonly used to treat psoriasis, although this has undesirable side effects, and is often combined with anti-inflammatory compounds. The aim of this study was to analyze if cannabidiol (CBD), a phytocannabinoid that has anti-inflammatory and antioxidant properties, may modify the proapoptotic effects of UVB irradiation in vitro by influencing apoptotic signaling pathways in donor psoriatic and healthy human keratinocytes obtained from the skin of five volunteers in each group. While CBD alone did not have any major effects on keratinocytes, the UVB treatment activated the extrinsic apoptotic pathway, with enhanced caspase 8 expression in both healthy and psoriatic keratinocytes. However, endoplasmic reticulum (ER) stress, characterized by increased expression of caspase 2, was observed in psoriatic cells after UVB irradiation. Furthermore, decreased p-AKT expression combined with increased 15-d-PGJ2 level and p-p38 expression was observed in psoriatic keratinocytes, which may promote both apoptosis and necrosis. Application of CBD partially attenuated these effects of UVB irradiation both in healthy and psoriatic keratinocytes, reducing the levels of 15-d-PGJ2, p-p38 and caspase 8 while increasing Bcl2 expression. However, CBD increased p-AKT only in UVB-treated healthy cells. Therefore, the reduction of apoptotic signaling pathways by CBD, observed mainly in healthy keratinocytes, suggests the need for further research into the possible beneficial effects of CBD.
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Affiliation(s)
- Piotr Wójcik
- Department of Analytical Chemistry, Medical University of Bialystok, 15-222 Bialystok, Poland; (P.W.); (A.G.)
| | - Agnieszka Gęgotek
- Department of Analytical Chemistry, Medical University of Bialystok, 15-222 Bialystok, Poland; (P.W.); (A.G.)
| | - Neven Žarković
- LabOS, Rudjer Boskovic Institute, 10000 Zagreb, Croatia;
| | - Elżbieta Skrzydlewska
- Department of Analytical Chemistry, Medical University of Bialystok, 15-222 Bialystok, Poland; (P.W.); (A.G.)
- Correspondence: ; Tel.: +48-857485708
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7
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Bahamondes Lorca VA, Wu S. Role of constitutive nitric oxide synthases in the dynamic regulation of the autophagy response of keratinocytes upon UVB exposure. Photochem Photobiol Sci 2021; 19:1559-1568. [PMID: 33030168 DOI: 10.1039/d0pp00280a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultraviolet B (UVB) radiation induces autophagy responses, which play a role in the regulation of the oncogenic processes of irradiated cells. However, the mechanism of autophagy responses post-UVB irradiation remains to be fully elucidated. Previous studies indicate that UVB radiation induces the activation and uncoupling of constitutive nitric oxide synthases (cNOS), which produce nitric oxide and peroxynitrite; both have been shown to regulate autophagy responses. In this study, the UVB-induced autophagy responses were analysed in cell line- and UVB dose-dependent manners, and the role of cNOS in UVB-induced autophagy responses was also studied. Our data showed that UVB induces both autophagosome formation and degradation, and that cNOS is involved in the regulation of autophagy responses post UVB exposure. Both nitric oxide and peroxynitrite, the two products that are produced in cells immediately after UVB exposure, could upregulate autophagy in a dose-dependent manner. Furthermore, cNOS is involved in the UVB-induced downregulation of SQSTM1/p62, a scaffold protein used as a reporter of the autophagy response. However, the cNOS-mediated reduction of SQSTM1/p62 is autophagy-independent post UVB irradiation. Our results indicated that autophagy responses post UVB exposure are a dynamic balance of autophagosome formation and degradation, with cNOS playing a role in the regulation of the balance.
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Affiliation(s)
- Verónica A Bahamondes Lorca
- Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, USA. and Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Shiyong Wu
- Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, USA.
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8
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Sinha NK, Ordureau A, Best K, Saba JA, Zinshteyn B, Sundaramoorthy E, Fulzele A, Garshott DM, Denk T, Thoms M, Paulo JA, Harper JW, Bennett EJ, Beckmann R, Green R. EDF1 coordinates cellular responses to ribosome collisions. eLife 2020; 9:e58828. [PMID: 32744497 PMCID: PMC7486125 DOI: 10.7554/elife.58828] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 08/02/2020] [Indexed: 12/11/2022] Open
Abstract
Translation of aberrant mRNAs induces ribosomal collisions, thereby triggering pathways for mRNA and nascent peptide degradation and ribosomal rescue. Here we use sucrose gradient fractionation combined with quantitative proteomics to systematically identify proteins associated with collided ribosomes. This approach identified Endothelial differentiation-related factor 1 (EDF1) as a novel protein recruited to collided ribosomes during translational distress. Cryo-electron microscopic analyses of EDF1 and its yeast homolog Mbf1 revealed a conserved 40S ribosomal subunit binding site at the mRNA entry channel near the collision interface. EDF1 recruits the translational repressors GIGYF2 and EIF4E2 to collided ribosomes to initiate a negative-feedback loop that prevents new ribosomes from translating defective mRNAs. Further, EDF1 regulates an immediate-early transcriptional response to ribosomal collisions. Our results uncover mechanisms through which EDF1 coordinates multiple responses of the ribosome-mediated quality control pathway and provide novel insights into the intersection of ribosome-mediated quality control with global transcriptional regulation.
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Affiliation(s)
- Niladri K Sinha
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Alban Ordureau
- Department of Cell Biology, Blavatnik Institute of Harvard Medical SchoolBostonUnited States
| | - Katharina Best
- Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität MünchenMunichGermany
| | - James A Saba
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Boris Zinshteyn
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Elayanambi Sundaramoorthy
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San DiegoSan DiegoUnited States
| | - Amit Fulzele
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San DiegoSan DiegoUnited States
| | - Danielle M Garshott
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San DiegoSan DiegoUnited States
| | - Timo Denk
- Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität MünchenMunichGermany
| | - Matthias Thoms
- Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität MünchenMunichGermany
| | - Joao A Paulo
- Department of Cell Biology, Blavatnik Institute of Harvard Medical SchoolBostonUnited States
| | - J Wade Harper
- Department of Cell Biology, Blavatnik Institute of Harvard Medical SchoolBostonUnited States
| | - Eric J Bennett
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San DiegoSan DiegoUnited States
| | - Roland Beckmann
- Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität MünchenMunichGermany
| | - Rachel Green
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of MedicineBaltimoreUnited States
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9
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Hu H, Peng L, Jiang H, Shen H, Zhou P, Gao Y. Silenced CHOP protects pancreatic B‐cell function by targeting peroxisome proliferator‐activated receptor‐γ coactivator‐1α through nuclear factor‐κB signaling pathway in diabetes mellitus. J Cell Biochem 2019; 120:12595-12603. [PMID: 30848505 DOI: 10.1002/jcb.28526] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 12/03/2018] [Accepted: 12/06/2018] [Indexed: 12/25/2022]
Affiliation(s)
- Hao Hu
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
| | - Lingling Peng
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
| | - Haiyan Jiang
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
| | - Haijun Shen
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
| | - Ping Zhou
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
| | - Yunming Gao
- Department of Endocrinology The Second People's Hospital of Lianyungang Lianyungang China
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10
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Grafanaki K, Anastasakis D, Kyriakopoulos G, Skeparnias I, Georgiou S, Stathopoulos C. Translation regulation in skin cancer from a tRNA point of view. Epigenomics 2018; 11:215-245. [PMID: 30565492 DOI: 10.2217/epi-2018-0176] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Protein synthesis is a central and dynamic process, frequently deregulated in cancer through aberrant activation or expression of translation initiation factors and tRNAs. The discovery of tRNA-derived fragments, a new class of abundant and, in some cases stress-induced, small Noncoding RNAs has perplexed the epigenomics landscape and highlights the emerging regulatory role of tRNAs in translation and beyond. Skin is the biggest organ in human body, which maintains homeostasis of its multilayers through regulatory networks that induce translational reprogramming, and modulate tRNA transcription, modification and fragmentation, in response to various stress signals, like UV irradiation. In this review, we summarize recent knowledge on the role of translation regulation and tRNA biology in the alarming prevalence of skin cancer.
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Affiliation(s)
- Katerina Grafanaki
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece.,Department of Dermatology, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Dimitrios Anastasakis
- National Institute of Musculoskeletal & Arthritis & Skin, NIH, 50 South Drive, Room 1152, Bethesda, MD 20892, USA
| | - George Kyriakopoulos
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Ilias Skeparnias
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Sophia Georgiou
- Department of Dermatology, School of Medicine, University of Patras, 26504 Patras, Greece
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11
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Modulation of Protein Synthesis by eIF2α Phosphorylation Protects Cell from Heat Stress-Mediated Apoptosis. Cells 2018; 7:cells7120254. [PMID: 30544621 PMCID: PMC6316477 DOI: 10.3390/cells7120254] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 01/01/2023] Open
Abstract
Global warming poses a considerable threat to human health, necessitating a proper understanding of mechanisms underlying cell death in the pathogenesis of heat-related diseases. Although mechanisms governing cytoplasmic response to heat are well understood, processes regulating cellular response to disruption of proteostasis in the endoplasmic reticulum (ER) due to heat stress remain unclear. The current study reveals that hyperthermic conditions may lead to a disturbance of ER homeostasis, also known as ER stress. Subsequent activation of the unfolded protein response (UPR) resulted in concomitant induction of cell death. Among the three UPR signaling pathways, the eIF2α phosphorylation pathway, and not the IRE1α/ATF6α pathways, is likely the main contributor to cell death under heat stress. Considering the role of eIF2α in translational control, we investigated the protective effect of translation rate on heat stress-mediated cell death. When protein synthesis was attenuated using cycloheximide or homoharringtonine, cell death due to heat stress was significantly reduced. In summation, we propose that transient modulation of protein synthesis by eIF2α phosphorylation has a pivotal role in protecting cells from heat stress-induced apoptosis. Therefore, pharmacological agents that promote eIF2α phosphorylation or reduce ER stress may contribute to the development of promising therapeutic approaches against heat-related diseases.
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12
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Wek RC. Role of eIF2α Kinases in Translational Control and Adaptation to Cellular Stress. Cold Spring Harb Perspect Biol 2018; 10:a032870. [PMID: 29440070 PMCID: PMC6028073 DOI: 10.1101/cshperspect.a032870] [Citation(s) in RCA: 294] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A central mechanism regulating translation initiation in response to environmental stress involves phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α). Phosphorylation of eIF2α causes inhibition of global translation, which conserves energy and facilitates reprogramming of gene expression and signaling pathways that help to restore protein homeostasis. Coincident with repression of protein synthesis, many gene transcripts involved in the stress response are not affected or are even preferentially translated in response to increased eIF2α phosphorylation by mechanisms involving upstream open reading frames (uORFs). This review highlights the mechanisms regulating eIF2α kinases, the role that uORFs play in translational control, and the impact that alteration of eIF2α phosphorylation by gene mutations or small molecule inhibitors can have on health and disease.
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Affiliation(s)
- Ronald C Wek
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126
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13
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Collier AE, Spandau DF, Wek RC. Translational control of a human CDKN1A mRNA splice variant regulates the fate of UVB-irradiated human keratinocytes. Mol Biol Cell 2017; 29:29-41. [PMID: 29118075 PMCID: PMC5746064 DOI: 10.1091/mbc.e17-06-0362] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/20/2017] [Accepted: 11/02/2017] [Indexed: 01/08/2023] Open
Abstract
In response to sublethal ultraviolet B (UVB) irradiation, human keratinocytes transiently block progression of the cell cycle to allow ample time for DNA repair and cell fate determination. These cellular activities are important for avoiding the initiation of carcinogenesis in skin. Central to these processes is the repression of initiation of mRNA translation through GCN2 phosphorylation of eIF2α (eIF2α-P). Concurrent with reduced global protein synthesis, eIF2α-P and the accompanying integrated stress response (ISR) selectively enhance translation of mRNAs involved in stress adaptation. In this study, we elucidated a mechanism for eIF2α-P cytoprotection in response to UVB in human keratinocytes. Loss of eIF2α-P induced by UVB diminished G1 arrest, DNA repair, and cellular senescence coincident with enhanced cell death in human keratinocytes. Genome-wide analysis of translation revealed that the mechanism for these critical adaptive responses by eIF2α-P involved induced expression of CDKN1A encoding the p21 (CIP1/WAF1) protein. We further show that human CDKN1A mRNA splice variant 4 is preferentially translated following stress-induced eIF2α-P by a mechanism mediated in part by upstream ORFs situated in the 5'-leader of CDKN1A mRNA. We conclude that eIF2α-P is cytoprotective in response to UVB by a mechanism featuring translation of a specific splice variant of CDKN1A that facilitates G1 arrest and subsequent DNA repair.
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Affiliation(s)
- Ann E Collier
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Dan F Spandau
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202 .,Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Ronald C Wek
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202
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Chen X, Li L, Xu S, Bu W, Chen K, Li M, Gu H. Ultraviolet B radiation down-regulates ULK1 and ATG7 expression and impairs the autophagy response in human keratinocytes. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017; 178:152-164. [PMID: 29154199 DOI: 10.1016/j.jphotobiol.2017.08.043] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/28/2017] [Accepted: 08/31/2017] [Indexed: 01/06/2023]
Abstract
Autophagy is a self-digestive pathway that helps to maintain cellular homeostasis, and many autophagy-related gene (ATG)s involved the regulation of the autophagy process. Ultraviolet light is a common stressor of skin, but it is unclear how autophagy is regulated after ultraviolet exposure in epidermal keratinocytes. Here, we found that the mRNAs of some key ATG genes such as ULK1, ATG5 and ATG7 exhibited significantly lower levels in the skin tissues of the face and chest with solar ultraviolet exposure, compared with perineal skin. Interestingly, UVB radiation down-regulated the expression of ULK1, ATG3 and ATG7, and it inhibited the autophagy flux via a mechanistic target of rapamycin (MTOR)-independent pathway in human keratinocytes. The inhibition of autophagy in UVB-treated keratinocytes cannot be restored by treatment with the MTOR-dependent autophagy inducer rapamycin. Importantly, UVB treatment perturbs the conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to LC3-II and LC3-II turnover in response to treatment with MTOR inhibitors (Torin 1 and pp242), as well as endoplasmic reticular stress (A23187 and tunicamycin), inositol pathway (L690,330) and autophagy inducers (resveratrol and STF62247). Our study demonstrates that UVB radiation down-regulates several key autophagy-related proteins and impairs the autophagy response in keratinocytes. This study demonstrates a linkage between autophagy and skin disorders associated with ultraviolet exposure.
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Affiliation(s)
- Xu Chen
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China
| | - Li Li
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China
| | - Song Xu
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China
| | - Wenbo Bu
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China
| | - Kun Chen
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China
| | - Min Li
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China.
| | - Heng Gu
- Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Institute of Dermatology, Chinese Academy of Medical Science, Peking Union Medical College, Nanjing, China.
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15
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The leukocyte-associated immunoglobulin (Ig)–like receptor-1 modulating cell apoptosis and inflammatory cytokines secretion in THP-1 cells after Helicobacter pylori infection. Microb Pathog 2017. [DOI: 10.1016/j.micpath.2017.06.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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16
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Collier AE, Wek RC, Spandau DF. Human Keratinocyte Differentiation Requires Translational Control by the eIF2α Kinase GCN2. J Invest Dermatol 2017; 137:1924-1934. [PMID: 28528168 DOI: 10.1016/j.jid.2017.04.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 03/29/2017] [Accepted: 04/26/2017] [Indexed: 10/19/2022]
Abstract
Appropriate and sequential differentiation of keratinocytes is essential for all functions of the human epidermis. Although transcriptional regulation has proven to be important for keratinocyte differentiation, little is known about the role of translational control. A key mechanism for modulating translation is through phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2). A family of different eIF2α kinases function in the integrative stress response to inhibit general protein synthesis coincident with preferential translation of select mRNAs that participate in stress alleviation. Here we demonstrate that translational control through eIF2α phosphorylation is required for normal keratinocyte differentiation. Analyses of polysome profiles revealed that key differentiation genes, including involucrin, are bound to heavy polysomes during differentiation, despite decreased general protein synthesis. Induced eIF2α phosphorylation by the general control nonderepressible 2 (GCN2) protein kinase facilitated translational control and differentiation-specific protein expression during keratinocyte differentiation. Furthermore, loss of GCN2 thwarted translational control, normal epidermal differentiation, and differentiation gene expression in organotypic skin culture. These findings underscore a previously unknown function for GCN2 phosphorylation of eIF2α and translational control in the formation of an intact human epidermis.
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Affiliation(s)
- Ann E Collier
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Ronald C Wek
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
| | - Dan F Spandau
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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17
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Pakos-Zebrucka K, Koryga I, Mnich K, Ljujic M, Samali A, Gorman AM. The integrated stress response. EMBO Rep 2016; 17:1374-1395. [PMID: 27629041 DOI: 10.15252/embr.201642195] [Citation(s) in RCA: 1486] [Impact Index Per Article: 185.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 08/23/2016] [Indexed: 02/06/2023] Open
Abstract
In response to diverse stress stimuli, eukaryotic cells activate a common adaptive pathway, termed the integrated stress response (ISR), to restore cellular homeostasis. The core event in this pathway is the phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α) by one of four members of the eIF2α kinase family, which leads to a decrease in global protein synthesis and the induction of selected genes, including the transcription factor ATF4, that together promote cellular recovery. The gene expression program activated by the ISR optimizes the cellular response to stress and is dependent on the cellular context, as well as on the nature and intensity of the stress stimuli. Although the ISR is primarily a pro-survival, homeostatic program, exposure to severe stress can drive signaling toward cell death. Here, we review current understanding of the ISR signaling and how it regulates cell fate under diverse types of stress.
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Affiliation(s)
- Karolina Pakos-Zebrucka
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Izabela Koryga
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Katarzyna Mnich
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Mila Ljujic
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Afshin Samali
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Adrienne M Gorman
- Apoptosis Research Centre, National University of Ireland Galway, Galway, Ireland School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
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18
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Insulin-like growth factor-1 receptor regulates repair of ultraviolet B-induced DNA damage in human keratinocytes in vivo. Mol Oncol 2016; 10:1245-54. [PMID: 27373487 DOI: 10.1016/j.molonc.2016.06.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 05/24/2016] [Accepted: 06/07/2016] [Indexed: 11/23/2022] Open
Abstract
The activation status of the insulin-like growth factor-1 receptor (IGF-1R) regulates the cellular response of keratinocytes to ultraviolet B (UVB) exposure, both in vitro and in vivo. Geriatric skin is deficient in IGF-1 expression resulting in an aberrant IGF-1R-dependent UVB response which contributes to the development of aging-associated squamous cell carcinoma. Furthermore, our lab and others have reported that geriatric keratinocytes repair UVB-induced DNA damage less efficiently than young adult keratinocytes. Here, we show that IGF-1R activation influences DNA damage repair in UVB-irradiated keratinocytes. Specifically, in the absence of IGF-1R activation, the rate of DNA damage repair following UVB-irradiation was significantly slowed (using immortalized human keratinocytes) or inhibited (using primary human keratinocytes). Furthermore, inhibition of IGF-1R activity in human skin, using either ex vivo explant cultures or in vivo xenograft models, suppressed DNA damage repair. Primary keratinocytes with an inactivated IGF-1R also exhibited lower steady-state levels of nucleotide excision repair mRNAs. These results suggest that deficient UVB-induced DNA repair in geriatric keratinocytes is due in part to silenced IGF-1R activation in geriatric skin and provide a mechanism for how the IGF-1 pathway plays a role in the initiation of squamous cell carcinoma in geriatric patients.
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