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Bindoli A, Rigobello MP. Principles in redox signaling: from chemistry to functional significance. Antioxid Redox Signal 2013; 18:1557-93. [PMID: 23244515 DOI: 10.1089/ars.2012.4655] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Reactive oxygen and nitrogen species are currently considered not only harmful byproducts of aerobic respiration but also critical mediators of redox signaling. The molecules and the chemical principles sustaining the network of cellular redox regulated processes are described. Special emphasis is placed on hydrogen peroxide (H(2)O(2)), now considered as acting as a second messenger, and on sulfhydryl groups, which are the direct targets of the oxidant signal. Cysteine residues of some proteins, therefore, act as sensors of redox conditions and are oxidized in a reversible reaction. In particular, the formation of sulfenic acid and disulfide, the initial steps of thiol oxidation, are described in detail. The many cell pathways involved in reactive oxygen species formation are reported. Central to redox signaling processes are the glutathione and thioredoxin systems controlling H(2)O(2) levels and, hence, the thiol/disulfide balance. Lastly, some of the most important redox-regulated processes involving specific enzymes and organelles are described. The redox signaling area of research is rapidly expanding, and future work will examine new pathways and clarify their importance in cellular pathophysiology.
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Affiliation(s)
- Alberto Bindoli
- Institute of Neuroscience (CNR), Department of Biomedical Sciences, University of Padova, Padova, Italy.
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Zhou Y, Tung HY, Tsai YM, Hsu SC, Chang HW, Kawasaki H, Tseng HC, Plunkett B, Gao P, Hung CH, Vonakis BM, Huang SK. Aryl hydrocarbon receptor controls murine mast cell homeostasis. Blood 2013; 121:3195-204. [PMID: 23462117 PMCID: PMC3630832 DOI: 10.1182/blood-2012-08-453597] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 02/05/2013] [Indexed: 01/29/2023] Open
Abstract
We propose that the aryl hydrocarbon receptor (AhR), a unique chemical sensor, is critical in controlling mast cell differentiation, growth, and function in vitro and in vivo. In antigen-stimulated mast cells, exposure to AhR ligands resulted in a calcium- and reactive oxygen species (ROS)-dependent increase of reversible oxidation in and reduced activity of SHP-2 phosphatase, leading to enhanced mast cell signaling, degranulation, and mediator and cytokine release, as well as the in vivo anaphylactic response. Surprisingly, significant mast cell deficiency was noted in AhR-null mice due to defective calcium signaling and mitochondrial function, concomitant with reduced expression of c-kit and cytosolic STAT proteins, as well as enhanced intracellular ROS and apoptosis. Consequently, AhR-null mast cells responded poorly to stimulation, demonstrating a critical role of AhR signaling in maintaining mast cell homeostasis.
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Affiliation(s)
- Yufeng Zhou
- Johns Hopkins Asthma and Allergy Center, Johns Hopkins University School of Medicine, Baltimore, MD 21224, USA
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53
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Corcoran A, Cotter TG. Redox regulation of protein kinases. FEBS J 2013; 280:1944-65. [PMID: 23461806 DOI: 10.1111/febs.12224] [Citation(s) in RCA: 212] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 02/24/2013] [Accepted: 02/27/2013] [Indexed: 12/30/2022]
Abstract
Reactive oxygen species (ROS) have been long regarded as by-products of a cascade of reactions stemming from cellular oxygen metabolism, which, if they accumulate to toxic levels, can have detrimental effects on cellular biomolecules. However, more recently, the recognition of ROS as mediators of cellular communications has led to their classification as signalling mediators in their own right. The prototypic redox-regulated targets downstream of ROS are the protein tyrosine phosphatases, and the wealth of research that has focused on this area has come to shape our understanding of how redox-signalling contributes to and facilitates protein tyrosine phosphorylation signalling cascades. However, it is becoming increasingly apparent that there is more to this system than simply the negative regulation of protein tyrosine phosphatases. Identification of redox-sensitive kinases such as Src led to the slow emergence of a role for redox regulation of tyrosine kinases. A flow of evidence, which has increased exponentially in recent times as a result of the development of new methods for the detection of oxidative modifications, demonstrates that, by concurrent oxidative activation of tyrosine kinases, ROS fine tune the duration and amplification of the phosphorylation signal. A more thorough understanding of the complex regulatory mechanism of redox-modification will allow targeting of both the production of ROS and their downstream effectors for therapeutic purposes. The present review assesses the most relevant recent literature that demonstrates a role for kinase regulation by oxidation, highlights the most significant findings and proposes future directions for this crucial area of redox biology.
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Affiliation(s)
- Aoife Corcoran
- Tumour Biology Laboratory, Biochemistry Department, Bioscience Research Institute, University College Cork, Ireland
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Othman A, Ahmad S, Megyerdi S, Mussell R, Choksi K, Maddipati KR, Elmarakby A, Rizk N, Al-Shabrawey M. 12/15-Lipoxygenase-derived lipid metabolites induce retinal endothelial cell barrier dysfunction: contribution of NADPH oxidase. PLoS One 2013; 8:e57254. [PMID: 23437353 PMCID: PMC3577708 DOI: 10.1371/journal.pone.0057254] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 01/18/2013] [Indexed: 01/08/2023] Open
Abstract
The purpose of the current study was to evaluate the effect of 12/15- lipoxygenase (12/15-LOX) metabolites on retinal endothelial cell (REC) barrier function. FITC-dextran flux across the REC monolayers and electrical cell-substrate impedance sensing (ECIS) were used to evaluate the effect of 12- and 15-hydroxyeicosatetreanoic acids (HETE) on REC permeability and transcellular electrical resistance (TER). Effect of 12- or 15-HETE on the levels of zonula occludens protein 1 (ZO-1), reactive oxygen species (ROS), NOX2, pVEGF-R2 and pSHP1 was examined in the presence or absence of inhibitors of NADPH oxidase. In vivo studies were performed using Ins2Akita mice treated with or without the 12/15-LOX inhibitor baicalein. Levels of HETE and inflammatory mediators were examined by LC/MS and Multiplex Immunoassay respectively. ROS generation and NOX2 expression were also measured in mice retinas. 12- and 15- HETE significantly increased permeability and reduced TER and ZO-1expression in REC. VEGF-R2 inhibitor reduced the permeability effect of 12-HETE. Treatment of REC with HETE also increased ROS generation and expression of NOX2 and pVEGF-R2 and decreased pSHP1 expression. Treatment of diabetic mice with baicalein significantly decreased retinal HETE, ICAM-1, VCAM-1, IL-6, ROS generation, and NOX2 expression. Baicalein also reduced pVEGF-R2 while restored pSHP1 levels in diabetic retina. Our findings suggest that 12/15-LOX contributes to vascular hyperpermeability during DR via NADPH oxidase dependent mechanism which involves suppression of protein tyrosine phosphatase and activation of VEGF-R2 signal pathway.
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Affiliation(s)
- Amira Othman
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
- Department of Anatomy, Mansoura University, Mansoura, Egypt
| | - Saif Ahmad
- Department of Ophthalmology and Vision Discovery Institute, Medical College of Georgia, Georgia Regents University (GRU), Augusta, Georgia, United States of America
| | - Sylvia Megyerdi
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
| | - Rene Mussell
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
| | - Karishma Choksi
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
| | - Krishna Rao Maddipati
- Department of Pathology, Wayne States University, Detroit, Michigan, United States of America
| | - Ahmed Elmarakby
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University (GRU), Augusta, Georgia, United States of America
| | - Nasser Rizk
- Department of Health Sciences, College of Science, Qatar University, Doha, Qatar
| | - Mohamed Al-Shabrawey
- Department of Oral Biology/Anatomy, College of Dental Medicine, Georgia Regents University (GRU), Augusta, Georgia, United States of America
- Department of Anatomy, Mansoura University, Mansoura, Egypt
- Department of Ophthalmology and Vision Discovery Institute, Medical College of Georgia, Georgia Regents University (GRU), Augusta, Georgia, United States of America
- Vascular Biology Center, Medical College of Georgia, Georgia Regents University (GRU), Augusta, Georgia, United States of America
- * E-mail:
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Sengupta A, Lichti UF, Carlson BA, Cataisson C, Ryscavage AO, Mikulec C, Conrad M, Fischer SM, Hatfield DL, Yuspa SH. Targeted disruption of glutathione peroxidase 4 in mouse skin epithelial cells impairs postnatal hair follicle morphogenesis that is partially rescued through inhibition of COX-2. J Invest Dermatol 2013; 133:1731-41. [PMID: 23364477 PMCID: PMC3652900 DOI: 10.1038/jid.2013.52] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Selenoproteins are essential molecules for the mammalian antioxidant network. We previously demonstrated that targeted loss of all selenoproteins in mouse epidermis disrupted skin and hair development and caused premature death. In the current study we targeted specific selenoproteins for epidermal deletion to determine whether similar phenotypes developed. Keratinocyte-specific knockout mice lacking either the glutathione peroxidase 4 (GPx4) or thioredoxin reductase 1 (TR1) gene were generated by cre-lox technology using K14-cre. TR1 knockout mice had a normal phenotype in resting skin while GPx4 loss in epidermis caused epidermal hyperplasia, dermal inflammatory infiltrate, dysmorphic hair follicles and alopecia in perinatal mice. Unlike epidermal ablation of all selenoproteins, mice ablated for GPx4 recovered after 5 weeks and had a normal lifespan. GPx1 and TR1 were upregulated in the skin and keratinocytes of GPx4 knockout mice. GPx4 deletion reduces keratinocyte adhesion in culture and increases lipid peroxidation and COX-2 levels in cultured keratinocytes and whole skin. Feeding a COX-2 inhibitor to nursing mothers partially prevents development of the abnormal skin phenotype in knockout pups. These data link the activity of cutaneous GPx4 to the regulation of COX-2 and hair follicle morphogenesis and provide insight into the function of individual selenoprotein activity in maintaining cutaneous homeostasis.
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Affiliation(s)
- Aniruddha Sengupta
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
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Böhmer F, Szedlacsek S, Tabernero L, Ostman A, den Hertog J. Protein tyrosine phosphatase structure-function relationships in regulation and pathogenesis. FEBS J 2013; 280:413-31. [PMID: 22682070 DOI: 10.1111/j.1742-4658.2012.08655.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Protein phosphorylation on tyrosine residues is tightly controlled by protein tyrosine phosphatases (PTPs) at multiple levels: spatio-temporal expression, subcellular localization and post-translational modification. Structural and functional analysis of the PTP domains has provided insight into catalysis and regulatory mechanisms that control the enzymatic activity. Understanding the molecular basis of PTP regulation is of fundamental importance to dissect the pleiotropic effect of these enzymes in both health and disease. Here, we review recent insights into the regulation of receptor-like PTPs by extracellular ligands and into regulation by reversible oxidation that impairs catalysis directly. The physiological roles of PTPs are essential in homeostasis in eukaryotic cells and pertubation of their functional attributes causes different disease states. As an example, we discuss recent findings indicating how inappropriate oxidation of PTPs in cancer cells may contribute to cell transformation. On the other hand, PTPs from many pathogens are key virulence factors and manipulate signalling pathways in the host cells to promote invasion and survival of the microorganisms. This research area has received relatively little attention but has advanced remarkably. We review the structural features of pathogenic PTPs, their similarities and differences with eukaryotic PTPs, and the possible exploitation of this knowledge for therapeutic intervention.
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Affiliation(s)
- Frank Böhmer
- Center for Molecular Biomedicine, Jena University Hospital, Jena, Germany
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57
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Parsons ZD, Gates KS. Redox regulation of protein tyrosine phosphatases: methods for kinetic analysis of covalent enzyme inactivation. Methods Enzymol 2013; 528:129-54. [PMID: 23849863 DOI: 10.1016/b978-0-12-405881-1.00008-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Phosphorylation of tyrosine residues is an important posttranslational modification that modulates the function of proteins involved in many important cell signaling pathways. Protein tyrosine kinases and protein tyrosine phosphatases (PTPs) work in tandem to control the phosphorylation status of target proteins. Not surprisingly, the activity of some PTPs is regulated as part of the endogenous cellular mechanisms for controlling the intensity and duration of responses to various stimuli. One important mechanism for the regulation of PTPs involves endogenous production of hydrogen peroxide (H2O2) that inactivates enzymes via covalent modification of an active site cysteine thiolate group. Other endogenous metabolites and xenobiotics that inactivate PTPs via covalent mechanisms also have the potential to modulate signal transduction pathways and may possess either therapeutic or toxic properties. This chapter discusses methods for quantitative kinetic analysis of covalent inactivation of PTPs by small molecules.
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Affiliation(s)
- Zachary D Parsons
- Department of Chemistry, University of Missouri, Columbia, Missouri, USA
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58
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Abstract
BACKGROUND With increasing evidence that hydroperoxides are not only toxic but rather exert essential physiological functions, also hydroperoxide removing enzymes have to be re-viewed. In mammals, the peroxidases inter alia comprise the 8 glutathione peroxidases (GPx1-GPx8) so far identified. SCOPE OF THE REVIEW Since GPxs have recently been reviewed under various aspects, we here focus on novel findings considering their diverse physiological roles exceeding an antioxidant activity. MAJOR CONCLUSIONS GPxs are involved in balancing the H2O2 homeostasis in signalling cascades, e.g. in the insulin signalling pathway by GPx1; GPx2 plays a dual role in carcinogenesis depending on the mode of initiation and cancer stage; GPx3 is membrane associated possibly explaining a peroxidatic function despite low plasma concentrations of GSH; GPx4 has novel roles in the regulation of apoptosis and, together with GPx5, in male fertility. Functions of GPx6 are still unknown, and the proposed involvement of GPx7 and GPx8 in protein folding awaits elucidation. GENERAL SIGNIFICANCE Collectively, selenium-containing GPxs (GPx1-4 and 6) as well as their non-selenium congeners (GPx5, 7 and 8) became key players in important biological contexts far beyond the detoxification of hydroperoxides. This article is part of a Special Issue entitled Cellular functions of glutathione.
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Affiliation(s)
- Regina Brigelius-Flohé
- Department of Biochemistry of Micronutrients, German Institute of Human Nutrition, Nuthetal, Germany.
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59
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Cole-Ezea P, Swan D, Shanley D, Hesketh J. Glutathione peroxidase 4 has a major role in protecting mitochondria from oxidative damage and maintaining oxidative phosphorylation complexes in gut epithelial cells. Free Radic Biol Med 2012; 53:488-97. [PMID: 22634395 DOI: 10.1016/j.freeradbiomed.2012.05.029] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 05/08/2012] [Accepted: 05/08/2012] [Indexed: 02/07/2023]
Abstract
Intake of the micronutrient selenium, which is incorporated into 25 selenoproteins in humans, has been implicated in affecting risk of colorectal cancer. A genetic variant in the gene encoding the selenoprotein glutathione peroxidase 4 (GPX4) has been reported to influence colorectal cancer risk. In this study GPX4 expression was knocked down by 60% using RNA silencing and the effects were investigated using an unbiased transcriptomic analysis. Microarray analysis of the total Caco-2 cell transcriptome was carried out using Illumina HumanHT-12v3 beadchips and the data were validated by real-time PCR. Ingenuity Pathway Analysis showed that the major canonical pathways affected by GPX4 knockdown were oxidative phosphorylation, ubiquinone biosynthesis, and mitochondrial dysfunction and the top two toxicological lists were mitochondrial dysfunction and oxidative stress. Western blotting and real-time PCR confirmed that knockdown affected target genes encoding components of respiratory complexes I, IV, and V as well as the protein apoptosis-inducing factor (AIF). GPX4 knockdown increased levels of mitochondrial reactive oxygen species and oxidized lipid and decreased mitochondrial adenosine triphosphate levels and mitochondrial membrane potential. Time-course experiments showed that changes in AIF expression preceded those in the respiratory complexes. We conclude that in Caco-2 gut epithelial cells GPx4, through effects on AIF, plays a major role in maintaining the oxidative phosphorylation system and protecting mitochondria from oxidative damage.
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Affiliation(s)
- Patience Cole-Ezea
- Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, UK
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60
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Meng FG, Zhang ZY. Redox regulation of protein tyrosine phosphatase activity by hydroxyl radical. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:464-9. [PMID: 22819876 DOI: 10.1016/j.bbapap.2012.06.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/25/2012] [Accepted: 06/30/2012] [Indexed: 01/12/2023]
Abstract
Substantial evidence suggests that transient production of reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) is an important signaling event triggered by the activation of various cell surface receptors. Major targets of H(2)O(2) include protein tyrosine phosphatases (PTPs). Oxidation of the active site Cys by H(2)O(2) abrogates PTP catalytic activity, thereby potentially furnishing a mechanism to ensure optimal tyrosine phosphorylation in response to a variety of physiological stimuli. Unfortunately, H(2)O(2) is poorly reactive in chemical terms and the second order rate constants for the H(2)O(2)-mediated PTP inactivation are ~10M(-1)s(-1), which is too slow to be compatible with the transient signaling events occurring at the physiological concentrations of H(2)O(2). We find that hydroxyl radical is produced from H(2)O(2) solutions in the absence of metal chelating agent by the Fenton reaction. We show that the hydroxyl radical is capable of inactivating the PTPs and the inactivation is active site directed, through oxidation of the catalytic Cys to sulfenic acid, which can be reduced by low molecular weight thiols. We also show that hydroxyl radical is a kinetically more efficient oxidant than H(2)O(2) for inactivating the PTPs. The second-order rate constants for the hydroxyl radical-mediated PTP inactivation are at least 2-3 orders of magnitude higher than those mediated by H(2)O(2) under the same conditions. Thus, hydroxyl radical generated in vivo may serve as a more physiologically relevant oxidizing agent for PTP inactivation. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.
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Affiliation(s)
- Fan-Guo Meng
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA
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61
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Al-Shabrawey M, Ahmad S, Megyerdi S, Othman A, Baban B, Palenski TL, Shin ES, Gurel Z, Hsu S, Sheibani N. Caspase-14: a novel caspase in the retina with a potential role in diabetic retinopathy. Mol Vis 2012; 18:1895-906. [PMID: 22876114 PMCID: PMC3413417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 07/11/2012] [Indexed: 10/27/2022] Open
Abstract
PURPOSE The purpose of this study was to evaluate caspase-14 expression in the retina under normal and diabetic conditions, and to determine whether caspase-14 contributes to retinal microvascular cell death under high glucose conditions. METHODS Quantitative real-time polymerase chain reaction and western blot analysis were used to evaluate caspase-14 expression in retinal cells, including pericytes (PCs), endothelial cells (ECs), astrocytes (ACs), choroidal ECs, and retinal pigment epithelium (RPE) cells. We also determined caspase-14 expression in the retinas of human subjects with or without diabetic retinopathy (DR) and in experimental diabetic mice. Retinal ECs and PCs were infected with adenoviruses expressing human caspase-14 or green fluorescent protein. Caspase-14 expression was also assessed in retinal vascular cells cultured under high glucose conditions. The number of apoptotic cells was determined with terminal deoxynucleotidyl transferase dUTP nick end labeling staining and confirmed by determining the levels of cleaved poly (ADP-ribose) polymerase-1 and caspase-3. RESULTS Our experiments demonstrated that retinal ECs, PCs, ACs, choroidal ECs, and RPE cells expressed caspase-14, and DR was associated with upregulation and/or activation of caspase-14 particularly in retinal vasculature. High glucose induced marked elevation of the caspase-14 level in retinal vascular cells. There was a significant increase in the apoptosis rate and the levels of cleaved poly (ADP-ribose) polymerase-1 and caspase-3 in retinal ECs and PCs overexpressing caspase-14. CONCLUSIONS Our findings indicate that caspase-14 might play a significant role in the pathogenesis of DR by accelerating retinal PC and EC death. Further investigations are required to elaborate the underlying mechanisms.
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Affiliation(s)
- Mohamed Al-Shabrawey
- Department of Oral Biology and Anatomy, Georgia Health Sciences University (GHSU), College of Dental Medicine, Augusta, GA,Ophthalmology and Vision Discovery Institute, GHSU, Medical College of Georgia, Augusta, GA,Department of Anatomy, Mansoura Faculty of Medicine, Mansoura, Egypt
| | - Saif Ahmad
- Ophthalmology and Vision Discovery Institute, GHSU, Medical College of Georgia, Augusta, GA
| | - Sylvia Megyerdi
- Department of Oral Biology and Anatomy, Georgia Health Sciences University (GHSU), College of Dental Medicine, Augusta, GA
| | - Amira Othman
- Department of Oral Biology and Anatomy, Georgia Health Sciences University (GHSU), College of Dental Medicine, Augusta, GA,Department of Anatomy, Mansoura Faculty of Medicine, Mansoura, Egypt
| | - Babak Baban
- Department of Oral Biology and Anatomy, Georgia Health Sciences University (GHSU), College of Dental Medicine, Augusta, GA
| | - Tammy L. Palenski
- Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Eui Seok Shin
- Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Zafer Gurel
- Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Stephen Hsu
- Department of Oral Biology and Anatomy, Georgia Health Sciences University (GHSU), College of Dental Medicine, Augusta, GA
| | - Nader Sheibani
- Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI
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Magnusson LU, Lundqvist A, Asp J, Synnergren J, Johansson CT, Palmqvist L, Jeppsson A, Hultén LM. High expression of arachidonate 15-lipoxygenase and proinflammatory markers in human ischemic heart tissue. Biochem Biophys Res Commun 2012; 424:327-30. [PMID: 22750246 DOI: 10.1016/j.bbrc.2012.06.117] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 06/22/2012] [Indexed: 12/13/2022]
Abstract
A common feature of the ischemic heart and atherosclerotic plaques is the presence of hypoxia (insufficient levels of oxygen in the tissue). Hypoxia has pronounced effects on almost every aspect of cell physiology, and the nuclear transcription factor hypoxia inducible factor-1α (HIF-1α) regulates adaptive responses to low concentrations of oxygen in mammalian cells. In our recent work, we observed that hypoxia increases the proinflammatory enzyme arachidonate 15-lipoxygenase (ALOX15B) in human carotid plaques. ALOX15 has recently been shown to be present in the human myocardium, but the effect of ischemia on its expression has not been investigated. Here we test the hypothesis that ischemia of the heart leads to increased expression of ALOX15, and found an almost 2-fold increase in HIF-1α mRNA expression and a 17-fold upregulation of ALOX15 mRNA expression in the ischemic heart biopsies from patients undergoing coronary bypass surgery compared with non ischemic heart tissue. To investigate the effect of low oxygen concentration on ALOX15 we incubated human vascular muscle cells in hypoxia and showed that expression of ALOX15 increased 22-fold compared with cells incubated in normoxic conditions. We also observed increased mRNA levels of proinflammatory markers in ischemic heart tissue compared with non-ischemic controls. In summary, we demonstrate increased ALOX15 in human ischemic heart biopsies. Furthermore we demonstrate that hypoxia increases ALOX15 in human muscle cells. Our results yield important insights into the underlying association between hypoxia and inflammation in the human ischemic heart disease.
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Affiliation(s)
- Lisa U Magnusson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden
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63
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Metabolism of anandamide into eoxamides by 15-lipoxygenase-1 and glutathione transferases. Lipids 2012; 47:781-91. [PMID: 22684912 DOI: 10.1007/s11745-012-3684-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 05/14/2012] [Indexed: 01/18/2023]
Abstract
Human 15-lipoxygenase-1 (15-LO-1) can metabolize arachidonic acid (ARA) into pro-inflammatory mediators such as the eoxins, 15-hydroperoxyeicosatetraenoic acid (HPETE), and 15-hydroxyeicosatetraenoyl-phosphatidylethanolamine. We have in this study investigated the formation of various lipid hydroperoxide by either purified 15-LO-1 or in the Hodgkin lymphoma cell line L1236, which contain abundant amount of 15-LO-1. Both purified 15-LO-1 and L1236 cells produced lipid hydroperoxides more efficiently when anandamide (AEA) or 2-arachidonoyl-glycerol ester was used as substrate than with ARA. Furthermore, L1236 cells converted AEA to a novel class of cysteinyl-containing metabolites. Based on RP-HPLC, mass spectrometry and comparison to synthetic products, these metabolites were identified as the ethanolamide of the eoxin (EX) C(4) and EXD(4). By using the epoxide EXA(4)-ethanol amide, it was also found that platelets have the capacity to produce the ethanolamide of EXC(4) and EXD(4). We suggest that the ethanolamides of the eoxins should be referred to as eoxamides, in analogy to the ethanolamides of prostaglandins which are named prostamides. The metabolism of AEA into eoxamides might engender molecules with novel biological effects. Alternatively, it might represent a new mechanism for the termination of AEA signalling.
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64
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Takac I, Schröder K, Brandes RP. The Nox family of NADPH oxidases: friend or foe of the vascular system? Curr Hypertens Rep 2012; 14:70-8. [PMID: 22071588 DOI: 10.1007/s11906-011-0238-3] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
NADPH (nicotinamide adenine dinucleotide phosphate) oxidases are important sources of reactive oxygen species (ROS). In the vascular system, ROS can have both beneficial and detrimental effects. Under physiologic conditions, ROS are involved in signaling pathways that regulate vascular tone as well as cellular processes like proliferation, migration and differentiation. However, high doses of ROS, which are produced after induction or activation of NADPH oxidases in response to cardiovascular risk factors and inflammation, contribute to the development of endothelial dysfunction and vascular disease. In vascular cells, the NADPH oxidase isoforms Nox1, Nox2, Nox4, and Nox5 are expressed, which differ in their activity, response to stimuli, and the type of ROS released. This review focuses on the specific role of different NADPH oxidase isoforms in vascular physiology and their potential contributions to vascular diseases.
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Affiliation(s)
- Ina Takac
- Institut für Kardiovaskuläre Physiologie, Fachbereich Medizin der Goethe-Universität, Theodor-Stern-Kai 7, Frankfurt am Main, Germany
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Huang Z, Rose AH, Hoffmann PR. The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities. Antioxid Redox Signal 2012; 16:705-43. [PMID: 21955027 PMCID: PMC3277928 DOI: 10.1089/ars.2011.4145] [Citation(s) in RCA: 523] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dietary selenium (]Se), mainly through its incorporation into selenoproteins, plays an important role in inflammation and immunity. Adequate levels of Se are important for initiating immunity, but they are also involved in regulating excessive immune responses and chronic inflammation. Evidence has emerged regarding roles for individual selenoproteins in regulating inflammation and immunity, and this has provided important insight into mechanisms by which Se influences these processes. Se deficiency has long been recognized to negatively impact immune cells during activation, differentiation, and proliferation. This is related to increased oxidative stress, but additional functions such as protein folding and calcium flux may also be impaired in immune cells under Se deficient conditions. Supplementing diets with above-adequate levels of Se can also impinge on immune cell function, with some types of inflammation and immunity particularly affected and sexually dimorphic effects of Se levels in some cases. In this comprehensive article, the roles of Se and individual selenoproteins in regulating immune cell signaling and function are discussed. Particular emphasis is given to how Se and selenoproteins are linked to redox signaling, oxidative burst, calcium flux, and the subsequent effector functions of immune cells. Data obtained from cell culture and animal models are reviewed and compared with those involving human physiology and pathophysiology, including the effects of Se levels on inflammatory or immune-related diseases including anti-viral immunity, autoimmunity, sepsis, allergic asthma, and chronic inflammatory disorders. Finally, the benefits and potential adverse effects of intervention with Se supplementation for various inflammatory or immune disorders are discussed.
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Affiliation(s)
- Zhi Huang
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA
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66
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Cell transformation by FLT3 ITD in acute myeloid leukemia involves oxidative inactivation of the tumor suppressor protein-tyrosine phosphatase DEP-1/ PTPRJ. Blood 2012; 119:4499-511. [PMID: 22438257 DOI: 10.1182/blood-2011-02-336446] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Signal transduction of FMS-like tyrosine kinase 3 (FLT3) is regulated by protein-tyrosine phosphatases (PTPs). We recently identified the PTP DEP-1/CD148/PTPRJ as a novel negative regulator of FLT3. This study addressed the role of DEP-1 for regulation of the acute myeloid leukemia (AML)-related mutant FLT3 internal tandem duplication (ITD) protein. Our experiments revealed that DEP-1 was expressed but dysfunctional in cells transformed by FLT3 ITD. This was caused by enzymatic inactivation of DEP-1 through oxidation of the DEP-1 catalytic cysteine. In intact cells, including primary AML cells, FLT3 ITD kinase inhibition reactivated DEP-1. DEP-1 reactivation was also achieved by counteracting the high levels of reactive oxygen species (ROS) production detected in FLT3 ITD-expressing cell lines by inhibition of reduced NAD phosphate (NADPH)-oxidases, or by overexpression of catalase or peroxiredoxin-1 (Prx-1). Interference with ROS production in 32D cells inhibited cell transformation by FLT3 ITD in a DEP-1-dependent manner, because RNAi-mediated depletion of DEP-1 partially abrogated the inhibitory effect of ROS quenching. Reactivation of DEP-1 by stable overexpression of Prx-1 extended survival of mice in the 32D cell/C3H/HeJ mouse model of FLT3 ITD-driven myeloproliferative disease. The study thus uncovered DEP-1 oxidation as a novel event contributing to cell transformation by FLT3 ITD.
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Latchoumycandane C, Marathe GK, Zhang R, McIntyre TM. Oxidatively truncated phospholipids are required agents of tumor necrosis factor α (TNFα)-induced apoptosis. J Biol Chem 2012; 287:17693-17705. [PMID: 22433871 DOI: 10.1074/jbc.m111.300012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
TNFα generates reactive oxygen species (ROS) at the cell surface that induce cell death, but how ROS communicate to mitochondria and their specific apoptotic action(s) are both undefined. ROS oxidize phospholipids to hydroperoxides that are friable and fragment adjacent to the (hydro)peroxide function, forming truncated phospholipids, such as azelaoyl phosphatidylcholine (Az-PC). Az-PC is relatively soluble, and exogenous Az-PC rapidly enters cells to damage mitochondrial integrity and initiate intrinsic apoptosis. We determined whether this toxic phospholipid is formed within cells during TNFα stimulation in sufficient quantities to induce apoptosis and if they are essential in TNFα-induced cytotoxicity. We found that TNFα induced ROS formation and phospholipid peroxidation in Jurkat cells, and either chemical interference with NADPH oxidase activity or siRNA suppression of the NADPH oxidase-4 subunit blocked ROS accumulation and phospholipid peroxidation. Mass spectrometry showed that phospholipid peroxides and then Az-PC increased after TNFα exposure, whereas ROS inhibition abolished Az-PC accumulation and TNFα-induced cell death. Glutathione peroxidase-4 (GPx4), which specifically metabolizes lipid hydroperoxides, fell in TNFα-stimulated cells prior to death. Ectopic GPx4 overcame this, reduced peroxidized phospholipid accumulation, blocked Az-PC accumulation, and prevented death. Conversely, GPx4 siRNA knockdown enhanced phospholipid peroxidation, increasing TNFα-stimulated Az-PC formation and apoptosis. Truncated phospholipids were essential elements of TNFα-induced apoptosis because overexpression of PAFAH2 (a phospholipase A(2) that selectively hydrolyzes truncated phospholipids) blocked TNFα-induced Az-PC accumulation without affecting phospholipid peroxidation. PAFAH2 also abolished apoptosis. Thus, phospholipid oxidation and truncation to apoptotic phospholipids comprise an essential element connecting TNFα receptor signaling to mitochondrial damage and apoptotic death.
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Affiliation(s)
- Calivarathan Latchoumycandane
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine, Cleveland, Ohio 44195
| | - Gopal K Marathe
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine, Cleveland, Ohio 44195
| | - Renliang Zhang
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine, Cleveland, Ohio 44195
| | - Thomas M McIntyre
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine, Cleveland, Ohio 44195.
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Andrae N, Kirches E, Hartig R, Haase D, Keilhoff G, Kalinski T, Mawrin C. Sunitinib targets PDGF-receptor and Flt3 and reduces survival and migration of human meningioma cells. Eur J Cancer 2012; 48:1831-41. [PMID: 22391574 DOI: 10.1016/j.ejca.2012.01.032] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 01/16/2012] [Accepted: 01/31/2012] [Indexed: 11/25/2022]
Abstract
The multitargeted tyrosine-kinase inhibitor sunitinib is a highly effective anti-angiogenic and cytostatic agent in the therapy of various tumours. While malignant gliomas have been shown to be responsive to sunitinib, detailed studies analysing human meningiomas are missing. We therefore analysed the effects of sunitinib in two benign (BenMen-1, HBL52) and two malignant (IOMM-Lee, KT21MG) human meningioma cell lines and found that DNA synthesis was significantly (p ≤ 0.001) inhibited following 1, 2 or 5 μM sunitinib, with IC(50) values between 2 and 5 μM in all cell lines. This effect was associated with a G(2)M-arrest at 10 μM for BenMen-1, HBL52 and IOMM-Lee, and 20 μM in KT21MG cells. Nuclear bisbenzimide staining revealed chromatin condensation following treatment with sunitinib concentrations of 10 μM or higher. Corresponding, cell viability assays showed a significant (p ≤ 0.001) short term decrease of viable cells (24h) only for high sunitinib concentrations with IC(50)-values between 10 and 20 μM. However, pre-irradiated meningioma cells (5 Gy) showed a sensitivity shift towards IC(50)-values around 5 μM sunitinib. We also found that 5 μM strongly reduced meningioma cell migration in vitro. Western blot analyses showed abolished platelet derived growth factor receptor (PDGFR)-autophosphorylation after sunitinib. Interestingly, the drug also inhibited the autophosphorylation of the receptor tyrosine kinase fms-like tyrosine kinase 3 (Flt3) in a dose-dependent manner. Taken together, the present data show that micromolar sunitinib has strong cytostatic and anti-migratory effects on human meningioma cells.
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Affiliation(s)
- Nadine Andrae
- Department of Neuropathology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
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Yeung J, Holinstat M. 12-lipoxygenase: a potential target for novel anti-platelet therapeutics. Cardiovasc Hematol Agents Med Chem 2012; 9:154-64. [PMID: 21838667 DOI: 10.2174/187152511797037619] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 07/07/2011] [Indexed: 01/31/2023]
Abstract
Platelets play an essential role in the regulation of hemostasis and thrombosis and controlling their level of activation is central to prevention of occlusive clot formation and stroke. Although a number of anti-platelet targets have been identified to address this issue including COX-1, the P2Y(12) receptor, the integrin αIIbβ3, and more recently the protease-activated receptor-1, these targets often result in a significant increased risk of bleeding which may lead to pathologies as serious as the thrombosis they were meant to treat including intracranial hemorrhage and gastrointestinal bleeding. Therefore, alternative approaches to treat uncontrolled platelet activation are warranted. Platelet-type 12-lipoxygenase is an enzyme which oxidizes the free fatty acid in the platelet resulting in the production of the stable metabolite 12-hydroxyeicosatetraenoic acid (12-HETE). The role of 12-HETE in the platelet has been controversial with reports associating its function as being both anti- and pro-thrombotic. In this review, the role of 12-lipoxygenase and its bioactive metabolites in regulation of platelet reactivity, clot formation, and hemostasis is described. Understanding the mechanisms by which 12-lipoxygenase and its metabolites modulate platelet function may lead to the development of a novel class of anti-platelet therapies targeting the enzyme in order to attenuate injury-induced clot formation, vessel occlusion and pathophysiological shifts in hemostasis.
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Affiliation(s)
- Jennifer Yeung
- Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, PA, USA
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70
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Ostman A, Frijhoff J, Sandin A, Böhmer FD. Regulation of protein tyrosine phosphatases by reversible oxidation. J Biochem 2011; 150:345-56. [PMID: 21856739 DOI: 10.1093/jb/mvr104] [Citation(s) in RCA: 207] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oxidation of the catalytic cysteine of protein-tyrosine phosphatases (PTP), which leads to their reversible inactivation, has emerged as an important regulatory mechanism linking cellular tyrosine phosphorylation and signalling by reactive-oxygen or -nitrogen species (ROS, RNS). This review focuses on recent findings about the involved pathways, enzymes and biochemical mechanisms. Both the general cellular redox state and extracellular ligand-stimulated ROS production can cause PTP oxidation. Members of the PTP family differ in their intrinsic susceptibility to oxidation, and different types of oxidative modification of the PTP catalytic cysteine can occur. The role of PTP oxidation for physiological signalling processes as well as in different pathologies is described on the basis of well-investigated examples. Criteria to establish the causal involvement of PTP oxidation in a given process are proposed. A better understanding of mechanisms leading to selective PTP oxidation in a cellular context, and finding ways to pharmacologically modulate these pathways are important topics for future research.
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Affiliation(s)
- Arne Ostman
- Cancer Center Karolinska, Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden.
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71
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Ufer C, Wang CC. The Roles of Glutathione Peroxidases during Embryo Development. Front Mol Neurosci 2011; 4:12. [PMID: 21847368 PMCID: PMC3148772 DOI: 10.3389/fnmol.2011.00012] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 07/13/2011] [Indexed: 01/31/2023] Open
Abstract
Embryo development relies on the complex interplay of the basic cellular processes including proliferation, differentiation, and apoptotic cell death. Precise regulation of these events is the basis for the establishment of embryonic structures and the organ development. Beginning with fertilization of the oocyte until delivery the developing embryo encounters changing environmental conditions such as varying levels of oxygen, which can give rise to reactive oxygen species (ROS). These challenges are met by the embryo with metabolic adaptations and by an array of anti-oxidative mechanisms. ROS can be deleterious by modifying biological molecules including lipids, proteins, and nucleic acids and may induce abnormal development or even embryonic lethality. On the other hand ROS are vital players of various signaling cascades that affect the balance between cell growth, differentiation, and death. An imbalance or dysregulation of these biological processes may generate cells with abnormal growth and is therefore potentially teratogenic and tumorigenic. Thus, a precise balance between processes generating ROS and those decomposing ROS is critical for normal embryo development. One tier of the cellular protective system against ROS constitutes the family of selenium-dependent glutathione peroxidases (GPx). These enzymes reduce hydroperoxides to the corresponding alcohols at the expense of reduced glutathione. Of special interest within this protein family is the moonlighting enzyme glutathione peroxidase 4 (Gpx4). This enzyme is a scavenger of lipophilic hydroperoxides on one hand, but on the other hand can be transformed into an enzymatically inactive cellular structural component. GPx4 deficiency - in contrast to all other GPx family members - leads to abnormal embryo development and finally produces a lethal phenotype in mice. This review is aimed at summarizing the current knowledge on GPx isoforms during embryo development and tumor development with an emphasis on GPx4.
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Affiliation(s)
- Christoph Ufer
- Institute of Biochemistry, Charité - University Medicine Berlin Berlin, Germany
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Farooqi AA, Waseem S, Riaz AM, Dilawar BA, Mukhtar S, Minhaj S, Waseem MS, Daniel S, Malik BA, Nawaz A, Bhatti S. PDGF: the nuts and bolts of signalling toolbox. Tumour Biol 2011; 32:1057-70. [PMID: 21769672 DOI: 10.1007/s13277-011-0212-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2011] [Accepted: 07/07/2011] [Indexed: 12/16/2022] Open
Abstract
PDGF is a growth factor and is extensively involved in multi-dimensional cellular dynamics. It switches on a plethora of molecules other than its classical pathway. It is engaged in various transitions of development; however, if the unleashed potentials lead astray, it brings forth tumourigenesis. Conventionally, it has been assumed that the components of this signalling pathway show fidelity and act with a high degree of autonomy. However, as illustrated by the PDGF signal transduction, reinterpretation of recent data suggests that machinery is often shared between multiple pathways, and other components crosstalk to each other through multiple mechanisms. It is important to note that metastatic cascade is an intricate process that we have only begun to understand in recent years. Many of the early steps of this PDGF cascade are not readily targetable in the clinic. In this review, we will unravel the paradoxes with reference to mitrons and cellular plasticity and discuss how disruption of signalling cascade triggers cellular proliferation phase transition and metastasis. We will also focus on the therapeutic interventions to counteract resultant molecular disorders.
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Affiliation(s)
- Ammad Ahmad Farooqi
- Institute of Molecular Biology and Biotechnology (IMBB), The University of Lahore, 1 km defence road, Lahore, Pakistan.
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Mannes AM, Seiler A, Bosello V, Maiorino M, Conrad M. Cysteine mutant of mammalian GPx4 rescues cell death induced by disruption of the wild-type selenoenzyme. FASEB J 2011; 25:2135-44. [PMID: 21402720 DOI: 10.1096/fj.10-177147] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Selenoproteins are expressed in many organisms, including bacteria, insects, fish, and mammals. Yet, it has remained obscure why some organisms rely on selenoproteins while others, like yeast and plants, express Cys-containing homologues. This study addressed the possible advantage of selenocysteine (Sec) vs. Cys in the essential selenoprotein glutathione peroxidase 4 (GPx4), using 4-hydroxy-tamoxifen-inducible Cre-excision of loxP-flanked GPx4 alleles in murine cells. Previously, it was shown that GPx4 disruption caused rapid cell death, which was prevented by α-tocopherol. Results presented herein demonstrate that the expression of wild-type (WT) GPx4 and its Sec/Cys (U46C) mutant rescued cell death of GPx4(-/-) cells, whereas the Sec/Ser (U46S) mutant failed. Notably, the specific activity of U46C was decreased by ∼90% and was indistinguishable from U46S-expressing and mock-transfected cells. Hence, the U46C mutant prevented apoptosis despite hardly measurable in vitro activity. Doxycycline-inducible expression revealed that minute amounts of either U46C or WT GPx4 prevented cell death, albeit WT GPx4 was more efficient. Interestingly, at the same expression level, proliferation was promoted in U46C-expressing cells but attenuated in WT-expressing cells. In summary, both catalytic efficiency and the expression level of GPx4 control the balance between cell survival and proliferation.
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Affiliation(s)
- Alexander M Mannes
- Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Clinical Molecular Biology and Tumor Genetics, Munich, Germany
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