201
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Saurin AT, Neubert H, Brennan JP, Eaton P. Widespread sulfenic acid formation in tissues in response to hydrogen peroxide. Proc Natl Acad Sci U S A 2004; 101:17982-7. [PMID: 15604151 PMCID: PMC539740 DOI: 10.1073/pnas.0404762101] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Indexed: 11/18/2022] Open
Abstract
A principal product of the reaction between a protein cysteinyl thiol and hydrogen peroxide is a protein sulfenic acid. Because protein sulfenic acid formation is reversible, it provides a mechanism whereby changes in cellular hydrogen peroxide concentration may directly control protein function. We have developed methods for the detection and purification of proteins oxidized in this way. The methodology is based on the arsenite-specific reduction of protein sulfenic acid under denaturing conditions and their subsequent labeling with biotin-maleimide. Arsenite-dependent signal generation was fully blocked by pretreatment with dimedone, consistent with its reactivity with sulfenic acids to form a covalent adduct that is nonreducible by thiols. The biotin tag facilitates the detection of protein sulfenic acids on Western blots probed with streptavidin-horseradish peroxidase and also their purification by streptavidin-agarose. We have characterized protein sulfenic acid formation in isolated hearts subjected to hydrogen peroxide treatment. We have also purified and identified a number of the proteins that are oxidized in this way by using a proteomic approach. Using Western immunoblotting we demonstrated that a highly significant proportion of some individual proteins (68% of total in one case) form the sulfenic derivative. We conclude that protein sulfenic acids are widespread physiologically relevant posttranslational oxidative modifications that can be detected at basal levels in healthy tissue, and are elevated in response to hydrogen peroxide. These approaches may find widespread utility in the study of oxidative stress, particularly because hydrogen peroxide is used extensively in models of disease or redox signaling.
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Affiliation(s)
- Adrian T Saurin
- Department of Cardiology, Cardiovascular Division, The Rayne Institute, St. Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
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202
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Abstract
Redox reactions pervade living cells. They are central to both anabolic and catabolic metabolism. The ability to maintain redox balance is therefore vital to all organisms. Various regulatory sensors continually monitor the redox state of the internal and external environments and control the processes that work to maintain redox homeostasis. In response to redox imbalance, new metabolic pathways are initiated, the repair or bypassing of damaged cellular components is coordinated and systems that protect the cell from further damage are induced. Advances in biochemical analyses are revealing a range of elegant solutions that have evolved to allow bacteria to sense different redox signals.
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Affiliation(s)
- Jeffrey Green
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
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203
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Dubbs P, Dubbs JM, Tabita FR. Effector-mediated interaction of CbbRI and CbbRII regulators with target sequences in Rhodobacter capsulatus. J Bacteriol 2004; 186:8026-35. [PMID: 15547275 PMCID: PMC529060 DOI: 10.1128/jb.186.23.8026-8035.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Rhodobacter capsulatus, genes encoding enzymes of the Calvin-Benson-Bassham reductive pentose phosphate pathway are located in the cbb(I) and cbb(II) operons. Each operon contains a divergently transcribed LysR-type transcriptional activator (CbbR(I) and CbbR(II)) that regulates the expression of its cognate cbb promoter in response to an as yet unidentified effector molecule(s). Both CbbR(I) and CbbR(II) were purified, and the ability of a variety of potential effector molecules to induce changes in their DNA binding properties at their target promoters was assessed. The responses of CbbR(I) and CbbR(II) to potential effectors were not identical. In gel mobility shift assays, the affinity of both CbbR(I) and CbbR(II) for their target promoters was enhanced in the presence of ribulose-1,5-bisphosphate (RuBP), phosphoenolpyruvate, 3-phosphoglycerate, 2-phosphoglycolate. ATP, 2-phosphoglycerate, and KH(2)PO(4) were found to enhance only CbbR(I) binding, while fructose-1,6-bisphosphate enhanced the binding of only CbbR(II). The DNase I footprint of CbbR(I) was reduced in the presence of RuBP, while reductions in the CbbR(II) DNase I footprint were induced by fructose-1,6-bisphosphate, 3-phosphoglycerate, and KH(2)PO(4). The current in vitro results plus recent in vivo studies suggest that CbbR-mediated regulation of cbb transcription is controlled by multiple metabolic signals in R. capsulatus. This control reflects not only intracellular levels of Calvin-Benson-Bassham cycle metabolic intermediates but also the fixed (organic) carbon status and energy charge of the cell.
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Affiliation(s)
- Padungsri Dubbs
- Department of Microbiology, Mahidol University, Payathai, Thailand
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204
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Abstract
The delicate and dynamic balance of the physiological steady state and its maintenance is well characterized by studies of bacterial stress response. Through the use of genetic analysis, numerous stress regulons, their physiological regulators and their biochemical processes have been delineated. In particular, transcriptionally activated stress regulons are subjects of study and application. These regulons include those that respond to macromolecular damage and toxicity as well as to nutrient starvation. The convenience of reporter gene fusions has allowed the creation of biosensor strains, resulting from the fusion of stress-responsive promoters with a variety of reporter genes. Such cellular biosensors are being used for monitoring dynamic systems and can report the presence of environmental stressors in real time. They provide a greater range of sensitivity, e.g. to sub-lethal concentrations of toxicants, than the simple assessment of cell viability. The underlying physiological context of the reporter strains results in the detection of bioavailable concentrations of both toxicants and nutrients. Culture conditions and host strain genotypes can be customized so as to maximize the sensitivity of the strain for a particular application. Collections of specific strains that are grouped in panels are used to diagnose targets or mode of action for unknown toxicants. Further application in massive by parallel DNA and gene fusion arrays greatly extends the information available for diagnosis of modes of action and may lead to development of novel high-throughput screens. Future studies will include more panels, arrays, as well as single reporter cell detection for a better understanding of the population heterogeneity during stress response. New knowledge of physiology gained from further studies of novel systems, or using innovative methods of analysis, will undoubtedly yield still more useful and informative environmental biosensors.
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Affiliation(s)
- Amy Cheng Vollmer
- Department of Biology, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, USA.
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205
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Lee C, Lee SM, Mukhopadhyay P, Kim SJ, Lee SC, Ahn WS, Yu MH, Storz G, Ryu SE. Redox regulation of OxyR requires specific disulfide bond formation involving a rapid kinetic reaction path. Nat Struct Mol Biol 2004; 11:1179-85. [PMID: 15543158 DOI: 10.1038/nsmb856] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 10/07/2004] [Indexed: 11/08/2022]
Abstract
The Escherichia coli OxyR transcription factor is activated by cellular hydrogen peroxide through the oxidation of reactive cysteines. Although there is substantial evidence for specific disulfide bond formation in the oxidative activation of OxyR, the presence of the disulfide bond has remained controversial. By mass spectrometry analyses and in vivo labeling assays we found that oxidation of OxyR in the formation of a specific disulfide bond between Cys199 and Cys208 in the wild-type protein. In addition, using time-resolved kinetic analyses, we determined that OxyR activation occurs at a rate of 9.7 s(-1). The disulfide bond-mediated conformation switch results in a metastable form that is locally strained by approximately 3 kcal mol(-1). On the basis of these observations we conclude that OxyR activation requires specific disulfide bond formation and that the rapid kinetic reaction path and conformation strain, respectively, drive the oxidation and reduction of OxyR.
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Affiliation(s)
- Cheolju Lee
- Center for Cellular Switch Protein Structure, Korea Research Institute of Bioscience and Biotechnology, 52 Euh-eun-dong, Yuseong-gu, Daejeon 305-806, Korea
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206
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Pan Z, Perez-Polo R. Regulation of γ-glutamylcysteine synthetase activity by nerve growth factor. Int J Dev Neurosci 2004. [DOI: 10.1016/0736-5748(96)00058-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Zhaohui Pan
- University of Texas Medical Branch at Galveston; 301 University Blvd; Galveston TX 77555-0652 U.S.A
| | - Regino Perez-Polo
- University of Texas Medical Branch at Galveston; 301 University Blvd; Galveston TX 77555-0652 U.S.A
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207
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Calabrese V, Stella AMG, Butterfield DA, Scapagnini G. Redox regulation in neurodegeneration and longevity: role of the heme oxygenase and HSP70 systems in brain stress tolerance. Antioxid Redox Signal 2004; 6:895-913. [PMID: 15345150 DOI: 10.1089/ars.2004.6.895] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Efficient functioning of maintenance and repair processes seems to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, which are composed of several genes termed "vitagenes," among these, the heat shock system, a highly conserved mechanism responsible for the preservation and repair of cellular macromolecules, such as proteins, RNAs, and DNA. Recent studies have shown that the heat shock response contributes to establishing a cytoprotective state in a wide variety of human diseases, including ischemia and reperfusion damage, inflammation, cancer, as well as metabolic and neurodegenerative disorders. Recently, the involvement of the heme oxygenase (HO) pathway in antidegenerative mechanisms has received considerable attention, as it has been demonstrated that the expression of HO is closely related to that of amyloid precursor protein. HO induction occurs together with the induction of other heat shock proteins during various physiopathological conditions. The vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, products of HO-catalyzed reaction, represent a protective system potentially active against brain oxidative injury. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Particularly, manipulation of endogenous cellular defense mechanisms, via the heat shock response, through nutritional antioxidants or pharmacological compounds, may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration. Consistently, by maintaining or recovering the activity of vitagenes, it is feasible to delay the aging process and decrease the occurrence of age-related diseases with resulting prolongation of a healthy life span.
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Affiliation(s)
- Vittorio Calabrese
- Section of Biochemistry and Molecular Biology, Department of Chemistry, Faculty of Medicine, University of Catania, Catania, Italy.
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208
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Sahu SN, Acharya S, Tuminaro H, Patel I, Dudley K, LeClerc JE, Cebula TA, Mukhopadhyay S. The bacterial adaptive response gene, barA, encodes a novel conserved histidine kinase regulatory switch for adaptation and modulation of metabolism in Escherichia coli. Mol Cell Biochem 2004; 253:167-77. [PMID: 14619967 DOI: 10.1023/a:1026028930203] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Histidine kinases are important prokaryotic determinants of cellular adaptation to environmental conditions, particularly stress. The highly conserved histidine kinase, BarA, encoded by the bacterial adaptive response gene, barA, is a member of the family of tripartite histidine kinases, and is involved in stress adaptation. BarA has been implicated to play a role during infection of epithelial cells. Homologues and orthologues of BarA have been found in pathogenic yeast, fungi, mould and in plants. The primary aim of this review is to assimilate evidence present in the current literature linking the role of BarA in stress response, and to support it with preliminary experimental evidence indicating that, it is indeed a global response regulator. In particular, the review focuses on the unusual domain structure of the BarA protein, its role in oxidative, weak acid, and osmotic stress responses and its role in biofilm formation. A preliminary genomic approach to identify downstream genes regulated by the BarA signaling pathway, using DNA microarray, is reported. The results demonstrate that BarA plays a global response regulatory role in cell division, carbon metabolism, iron metabolism and pili formation. The evolutionary significance of these types of histidine kinase sensors is reviewed in light of their roles in pathogenesis.
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209
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Poljak A, Dawes IW, Ingelse BA, Duncan MW, Smythe GA, Grant CM. Oxidative damage to proteins in yeast cells exposed to adaptive levels of H(2)O(2). Redox Rep 2004; 8:371-7. [PMID: 14980070 DOI: 10.1179/135100003225003401] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
When yeast cells are exposed to sublethal concentrations of oxidants, they adapt to tolerate subsequent lethal treatments. Here, we show that this adaptation involves tolerance of oxidative damage, rather than protection of cellular constituents. o- and m-tyrosine levels are used as a sensitive measure of protein oxidative damage and we show that such damage accumulates in yeast cells exposed to H(2)O(2) at low adaptive levels. Glutathione represents one of the main cellular protections against free radical attack and has a role in adaptation to oxidative stress. Yeast mutants defective in glutathione metabolism are shown to accumulate significant levels of o- and m-tyrosine during normal aerobic growth conditions.
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Affiliation(s)
- Anne Poljak
- Bioanalytical Mass Spectrometry Facility, Wallace Wurth Building University of New South Wales, Sydney, New South Wales, Australia.
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210
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Verneuil N, Sanguinetti M, Le Breton Y, Posteraro B, Fadda G, Auffray Y, Hartke A, Giard JC. Effects of the Enterococcus faecalis hypR gene encoding a new transcriptional regulator on oxidative stress response and intracellular survival within macrophages. Infect Immun 2004; 72:4424-31. [PMID: 15271899 PMCID: PMC470598 DOI: 10.1128/iai.72.8.4424-4431.2004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In order to identify regulators of the oxidative stress response in Enterococcus faecalis, an important human pathogen, several genes annotated as coding for transcriptional regulators were inactivated by insertional mutagenesis. One mutant, affected in the ef2958 locus (designated hypR [hydrogen peroxide regulator]), appeared to be highly sensitive to oxidative challenge caused by hydrogen peroxide. Moreover, testing of the hypR mutant by using an in vivo-in vitro macrophage infection model resulted in a highly significant reduction in survival compared to the survival of parent strain JH2-2. Northern blot analyses were carried out with probes specific for genes encoding known antioxidant enzymes, and they showed that the ahpCF (alkyl hydroperoxide reductase) transcript was expressed less in mutant cells. Mobility shift protein-DNA binding assays revealed that HypR regulated directly the expression of hypR itself and the ahpCF operon. Our combined results showed that HypR appeared to be directly involved in the expression of ahpCF genes under oxidative stress conditions and suggested that this regulator could contribute to the virulence of E. faecalis.
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Affiliation(s)
- Nicolas Verneuil
- Laboratoire de Microbiologie de l'Environnement, EA 956, USC INRA, IRBA, Université de Caen, 14032 Cannes Cedex, France
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211
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Dantur KI, Pizarro RA. Effect of growth phase on the Escherichia coli response to ultraviolet-A radiation: influence of conditioned media, hydrogen peroxide and acetate. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2004; 75:33-9. [PMID: 15246348 DOI: 10.1016/j.jphotobiol.2004.04.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Revised: 03/26/2004] [Accepted: 04/24/2004] [Indexed: 11/27/2022]
Abstract
The results reported herein indicate that the ultraviolet-A (UVA) radiation-induced effects in Escherichia coli depend on its growth phase. Stationary-phase cells recover faster from a sub-lethal UVA exposure and have a higher resistance to lethal effect of the radiation than exponential growing cells. Although pre-incubation in spent medium supernatant increased the resistance of log-phase cells to lethal UVA effects, this pre-treatment considerably prolonged the duration of the radioinduced sub-lethal growth delay. The aim of the present study was to investigate the effect exerted by the E. coli conditioned media and evaluate the influence of nutritional stress, hydrogen peroxide and acetate. Pre-incubated in conditioned medium, cells in exponential growth phase were irradiated and the induced effects were compared with those found when catalase, high culture densities and acetate were employed. Unexpectedly, the duration of the growth delay in cells submitted to these treatments was shortened in comparison with control cells incubated in conditioned medium with no modifications. Lengthening of the growth delay was mimicked when exponentially growing cells were incubated in fresh medium supplied with 5 microM H(2)O(2). The effects of spent medium on wild type and rpoS mutant strains were similar, indicating that this response is independent of RpoS controlled functions. We assumed that an oxidative component of the spent medium, probably H(2)O(2), could be involved in the observed phenomenon. This effect is specific of E. coli and independent of rpoS.
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Affiliation(s)
- Karina I Dantur
- Departamento de Radiobiología, Comisión Nacional de Energía Atómica, Av. General Paz 1499, 1650 General San Martín, Buenos Aires, Argentina
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212
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Padan E, Tzubery T, Herz K, Kozachkov L, Rimon A, Galili L. NhaA of Escherichia coli, as a model of a pH-regulated Na+/H+antiporter. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1658:2-13. [PMID: 15282168 DOI: 10.1016/j.bbabio.2004.04.018] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2004] [Revised: 03/17/2004] [Accepted: 04/20/2004] [Indexed: 11/18/2022]
Abstract
Na(+)/H(+) antiporters are ubiquitous membrane proteins that are involved in homeostasis of H(+) and Na(+) throughout the biological kingdom. Corroborating their role in pH homeostasis, many of the Na(+)/H(+) antiporter proteins are regulated directly by pH. The pH regulation of NhaA, the Escherichia coli Na(+)/H(+) antiporter (EcNhaA), as of other, both eukaryotic and prokaryotic Na(+)/H(+) antiporters, involves a pH sensor and conformational changes in different parts of the protein that transduce the pH signal into a change in activity. Thus, residues that affect the pH response, the translocation or both activities cluster in separate domains along the antiporter molecules. Importantly, in the NhaA family, these domains are conserved. Helix-packing model of EcNhaA based on cross-linking data suggests, that in the three dimensional structure of NhaA, residues that affect the pH response may be in close proximity, forming a single pH sensitive domain. Therefore, it is suggested that, despite considerable differences in the primary structure of the antiporters from the bacterial NhaA to the mammalian NHEs, their three-dimensional architectures are conserved. Test of this possibility awaits the atomic resolution of the 3D structure of the antiporters.
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Affiliation(s)
- E Padan
- Division of Microbial and Molecular Ecology, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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213
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Toledano MB, Delaunay A, Monceau L, Tacnet F. Microbial H2O2 sensors as archetypical redox signaling modules. Trends Biochem Sci 2004; 29:351-7. [PMID: 15236742 DOI: 10.1016/j.tibs.2004.05.005] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Michel B Toledano
- Laboratoire Stress Oxydants et Cancer, Service de Biologie Moléculaire Systémique, DBJC, DSV, CEA-Saclay, Bâtiment 142, 91191 Gif-sur-Yvette, France.
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214
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Abstract
Reactive (low pKa) cysteine residues in proteins are critical components in redox signaling. A particularly reactive and versatile reversibly oxidized form of cysteine, the sulfenic acid (Cys-SOH), has important roles as a catalytic center in enzymes and as a sensor of oxidative and nitrosative stress in enzymes and transcriptional regulators. Depending on environment, sometimes the sulfenic acid provides a metastable oxidized form, and other times it is a fleeting intermediate giving rise to more stable disulfide, sulfinic acid, or sulfenyl-amide forms.
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Affiliation(s)
- Leslie B Poole
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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215
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Zuber P. Spx-RNA polymerase interaction and global transcriptional control during oxidative stress. J Bacteriol 2004; 186:1911-8. [PMID: 15028674 PMCID: PMC374421 DOI: 10.1128/jb.186.7.1911-1918.2004] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Peter Zuber
- Department of Environmental and Biomolecular Systems, OGI School of Science & Engineering, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
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216
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Oxidative Stress/Antioxidant Status in HeaIth and Disease. OXYGEN/NITROGEN RADICALS 2004. [DOI: 10.1201/b14147-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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217
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Stadtman ER. Cyclic oxidation and reduction of methionine residues of proteins in antioxidant defense and cellular regulation. Arch Biochem Biophys 2004; 423:2-5. [PMID: 14989257 DOI: 10.1016/j.abb.2003.10.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Earl R Stadtman
- Laboratory of Biochemistry, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-8012, USA.
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218
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Abstract
Free radical-derived reactive oxygen species (ROS) are constantly generated in most living tissue and can potentially damage DNA, proteins and lipids. "Oxidative stress" occurs if ROS reach abnormally high concentrations. Harman was the first to propose that the damaging effects of ROS may play a key role in the mechanism of aging. Genetic studies of such distantly related species as C. elegans, Drosophila melanogaster, and mice support this hypothesis. However, ROS are not only a cause of structural damage, but also physiologically important mediators in biological signaling processes. Abnormally high levels of ROS may therefore lead to dysregulation of redox-sensitive signaling pathways. The redox-sensitive targets in these pathways are often signaling proteins with redox-sensitive cysteine residues which are oxidized to sulfenic acid moieties and mixed disulfides, thereby altering the signaling function of the protein. Because the formation of these mixed disulfides can also occur through a prooxidative shift in the intracellular thiol/disulfide redox status (REDST), the respective signaling pathways respond not only to ROS but also to changes in REDST. Information about the concentration of ROS in living tissue is scarce, but aging-related changes in REDST are well documented. Several studies with cell cultures or experimental animals have shown that the oxidative shift in the intracellular glutathione REDST is typically associated with cellular dysfunction. Complementary studies in humans have shown that oxidative changes in the plasma (i.e., extracellular) REDST are correlated with aging-related pathophysiological processes. The available evidence suggests that these changes play a key role in various conditions which limit the human life span. Several attempts have been made to ameliorate the consequences of aging by thiol-containing antioxidants, but this approach requires a detailed knowledge of the effects of thiol-containing antioxidants on cysteine homeostasis, REDST, and redox-sensitive signaling pathways of the host.
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Affiliation(s)
- Wulf Dröge
- Tumor Immunology Program, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
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219
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Zaid T, Srikumar TSN, Benov L. Growth of Escherichia coli in iron-enriched medium increases HPI catalase activity. BMB Rep 2004; 36:608-10. [PMID: 14659082 DOI: 10.5483/bmbrep.2003.36.6.608] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli has two catalases, HPI and HPII. HPI is induced during logarithmic growth in response to low concentrations of hydrogen peroxide. This induction is OxyR-dependent. On the other hand, HPII is not peroxide-inducible but is induced in entry to the stationary phase. We demonstrate here that E. coli displayed higher HPI catalase activity when compared to the cultures that were grown in a normal medium, if grown in a medium supplemented with iron-citrate. Iron supplementation had no effect on HPII catalase. This increase of HPI activity was OxyR-independent and not observed in a Deltafur mutant. The physiological significance of the increase of HPI activity is unclear, but it appears that the katG gene that codes for HPI catalase is among the genes that are regulated by Fur.
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Affiliation(s)
- Tarrik Zaid
- Department of Biochemistry, Faculty of Medicine, Kuwait University, Safat 13110, Kuwait
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220
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González B, Manso R. Induction, modification and accumulation of HSP70s in the rat liver after acute exercise: early and late responses. J Physiol 2004; 556:369-85. [PMID: 14754995 PMCID: PMC1664938 DOI: 10.1113/jphysiol.2003.058420] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Liver cells synthesize HSP72, the cytosolic highly stress-inducible member of the 70 kDa family of heat-shock proteins (HSP70s), in response to acute exercise. This study was aimed at obtaining further insight into the physiological relevance of the hepatic stress response to exercise by investigating the induction and long-term maintenance of increased levels of HSP70s of the HSP and glucose-regulated protein (GRP) families, their post-translational modifications during or after exercise and the possible relation of HSP induction to oxidative stress. In a running rat model, acute exercise activated the synthesis and accumulation of HSP72, GRP75 and GRP78 in liver cells, pointing towards a multifactorial origin of this response. A peak HSP72 accumulation was observed shortly after exercise as a result of transcriptional activation. HSP72 was reduced shortly after exercise preceding the disappearance of its mRNA. Two further waves of HSP72 accumulation peaked 8 and 48 h after exercise without transcriptional activation. A transient increase in the proportion of acidic variants of HSP72 and HSP73 was also observed shortly after exercise as a result, at least in part, of protein phosphorylation. Free and protein-bound lipid peroxidation derivatives (TBARS) showed a tendency to increase in the early post-exercise and the free-to-protein-bound TBARS ratio decreased significantly after 2 h. During the early post-exercise period, protein-bound TBARS correlated positively with HSP72 and 73, but not with GRP75 or GRP78. Altogether, the reported results indicate that the early induction and post-translational modification of HSP70s in liver cells following exercise is a preliminary step of a series of long-lasting HSP70-related events, possibly designed to preserve liver cell homeostasis and to help provide a concerted response of the whole organism to physical stress.
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Affiliation(s)
- Beatriz González
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, E-28049 Cantoblanco, Madrid, Spain.
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221
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Rhoads DM, Vanlerberghe GC. Mitochondria-Nucleus Interactions: Evidence for Mitochondrial Retrograde Communication in Plant Cells. PLANT MITOCHONDRIA: FROM GENOME TO FUNCTION 2004. [DOI: 10.1007/978-1-4020-2400-9_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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222
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Asad NR, Asad LMBO, Almeida CEBD, Felzenszwalb I, Cabral-Neto JB, Leitão AC. Several pathways of hydrogen peroxide action that damage the E. coli genome. Genet Mol Biol 2004. [DOI: 10.1590/s1415-47572004000200026] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
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223
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Cha MK, Kim WC, Lim CJ, Kim K, Kim IH. Escherichia coli periplasmic thiol peroxidase acts as lipid hydroperoxide peroxidase and the principal antioxidative function during anaerobic growth. J Biol Chem 2003; 279:8769-78. [PMID: 14676195 DOI: 10.1074/jbc.m312388200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
To clarify the enzymatic property of Escherichia coli periplasmic thiol peroxidase (p20), the specific peroxidase activity toward peroxides was compared with other bacterial thiol peroxidases. p20 has the most substrate preference and peroxidase activity toward organic hydroperoxide. Furthermore, p20 exerted the most potent lipid peroxidase activity. Despite that the mutation of p20 caused the highest susceptibility toward organic hydroperoxide and heat stress, the cellular level of p20 did not respond to the exposure of oxidative stress. Expression level of p20 during anaerobic growth was sustained at the approximately 50% level compared with that of the aerobic growth. Viability of aerobic p20Delta without glucose was reduced to the approximately 65% level of isogenic strains, whereas viability of aerobic p20Delta with 0.5% glucose supplement was sustained. The deletion of p20 resulted in a gradual loss of the cell viability during anaerobic growth. At the stationary phase, the viability of p20Delta was down to approximately 10% level of parent strains. An analysis of the protein carbonyl contents of p20Delta as a marker for cellular oxidation indicates that severe reduction of viability of anaerobic p20Delta was caused by cumulative oxidative stress. P20Delta showed hypersensitivity toward membrane-soluble organic hydroperoxides. An analysis of protein carbonyl and lipid hydroperoxide contents in the membrane of the stress-imposed p20Delta demonstrates that the severe reduction of viability was caused by cumulative oxidative stress on the membrane. Taken together, present data uncover in vivo function for p20 as a lipid hydroperoxide peroxidase and demonstrate that, as the result, p20 acts as the principal antioxidant in the anaerobic habitats.
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Affiliation(s)
- Mee-Kyung Cha
- Department of Biochemistry, Paichai University, Taejon 302-735, Republic of Korea
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224
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Abstract
Thiol-based regulatory switches play central roles in cellular responses to oxidative stress, nitrosative stress, and changes in the overall thiol-disulfide redox balance. Protein sulfhydryls offer a great deal of flexibility in the different types of modification they can undergo and the range of chemical signals they can perceive. For example, recent work on OhrR and OxyR has clearly established that disulfide bonds are not the only cysteine oxidation products that are likely to be relevant to redox sensing in vivo. Furthermore, different stresses can result in distinct modifications to the same protein; in OxyR it seems that distinct modifications can occur at the same cysteine, and in Yap1 a partner protein ensures that the disulfide bond induced by peroxide stress is different from the disulfide bond induced by other stresses. These kinds of discoveries have also led to the intriguing suggestion that different modifications to the same protein can create multiple activation states and thus deliver discrete regulatory outcomes. In this review, we highlight these issues, focusing on seven well-characterized microbial proteins controlled by thiol-based switches, each of which exhibits unique regulatory features.
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Affiliation(s)
- Mark S B Paget
- Department of Biochemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
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225
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Li W, Bottrill AR, Bibb MJ, Buttner MJ, Paget MSB, Kleanthous C. The Role of zinc in the disulphide stress-regulated anti-sigma factor RsrA from Streptomyces coelicolor. J Mol Biol 2003; 333:461-72. [PMID: 14529630 DOI: 10.1016/j.jmb.2003.08.038] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The regulation of disulphide stress in actinomycetes such as Streptomyces coelicolor is known to involve the zinc-containing anti-sigma factor RsrA that binds and inactivates the redox-regulated sigma factor sigmaR. However, it is not known how RsrA senses disulphide stress nor what role the metal ion plays. Using in vitro assays, we show that while zinc is not required for sigmaR binding it is required for functional anti-sigma factor activity, and that it plays a critical role in modulating the reactivity of RsrA cysteine thiol groups towards oxidation. Apo-RsrA is easily oxidised and, while the Zn-bound form is relatively resistant, the metal ion is readily expelled when the protein is treated with strong oxidants such as diamide. We also show, using a combination of proteolysis and mass spectrometry, that the first critical disulphide to form in RsrA involves Cys11 and one of either Cys41 or Cys44, all previously implicated in metal binding. Circular dichroism spectroscopy was used to follow structural changes during oxidation of RsrA, which indicated that concomitant with formation of this critical disulphide bond is a major restructuring of the protein where its alpha-helical content increases. Our data demonstrate that RsrA can only bind sigmaR in the reduced state and that this state is stabilised by zinc. Redox stress induces disulphide bond formation amongst zinc-ligating residues, expelling the metal ion and stabilising a structure incapable of binding the sigma factor.
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Affiliation(s)
- Wei Li
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
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226
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Nakano S, Küster-Schöck E, Grossman AD, Zuber P. Spx-dependent global transcriptional control is induced by thiol-specific oxidative stress in Bacillus subtilis. Proc Natl Acad Sci U S A 2003; 100:13603-8. [PMID: 14597697 PMCID: PMC263860 DOI: 10.1073/pnas.2235180100] [Citation(s) in RCA: 205] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Spx protein of Bacillus subtilis represses activator-stimulated transcription by interacting with the C-terminal domain of RNA polymerase (RNAP) alpha subunit. Its concentration increases in cells lacking the ATP-dependent protease, ClpXP, resulting in severe effects on growth and developmental processes. Microarray analysis was undertaken to identify genes that are induced or repressed when Spx interacts with RNAP. The induced genes included those encoding products known to function in maintaining thiol homeostasis. Two genes, thioredoxin (trxA) and thioredoxin reductase (trxB), are transcriptionally induced under conditions of thiol-specific oxidative (disulfide) stress by a mechanism involving Spx-RNAP interaction. Disulfide stress also results in an increase in Spx-dependent transcriptional repression. The increase in Spx activity in cells encountering disulfide stress is due in part to a posttranscriptional mechanism of spx control resulting in an increase in Spx concentration. An spx null mutant and a strain bearing an allele of rpoA that prevents Spx-RNAP interaction show hypersensitivity to disulfide stress. From these results, it is proposed that Spx is an activator that mobilizes the operations necessary to reverse the effects of oxidative damage, but it also serves as a negative regulator that causes the postponement of developmental programs and energy-consuming growth-related functions while the cell copes with the period of stress.
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Affiliation(s)
- Shunji Nakano
- Department of Environmental and Biomolecular Systems, OGI School of Science and Engineering, Oregon Health and Science University, Beaverton, OR 97006, USA
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227
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Ahmed S, Adamidis A, Jan LC, Gibbons N, Mattana J. Dexamethasone attenuates oxidation of extracellular matrix proteins by human monocytes. Exp Mol Pathol 2003; 75:137-43. [PMID: 14516775 DOI: 10.1016/s0014-4800(03)00070-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In response to infection or in immune complex-mediated diseases, inflammatory cells may oxidatively damage extracellular matrix (ECM) proteins. In this study we evaluated whether human monocytes could oxidize ECM and whether this could be modulated by exposure to LPS, IgG complexes, and dexamethasone (DEX). Wells in tissue culture plates were coated with the ECM preparation Matrigel. Porous inserts with or without the human monocyte cell line THP-1 were placed into ECM-containing wells and cells were exposed to control conditions or to LPS (10 ng/ml), IgG complexes (200 and 500 microg/ml), or DEX (10(-7) and 10(-6) M). ECM was then subjected to Western blot analysis using an antibody to oxidized protein. In addition, Western blot analysis was carried out on DEX-treated cells to evaluate expression of the NADPH oxidase components p67-phox and gp91-phox. THP-1 cells enhanced ECM oxidation and this effect was augmented by LPS and by IgG aggregates. Preincubation of cells with DEX attenuated ECM oxidation and was also associated with decreased expression of p67-phox and gp91-phox. These findings suggest that human monocytes can oxidize ECM proteins and that this may be modulated by IgG complexes and LPS. Dexamethasone appears to attenuate ECM oxidation and a better understanding of this mechanism might allow for interventions to minimize oxidative damage to ECM proteins by monocytes in infectious and inflammatory states.
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Affiliation(s)
- Shahid Ahmed
- Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, NY 11040, USA
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228
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Alfaro C, Urios A, González MC, Moya P, Blanco M. Screening for metabolites from Penicillium novae-zeelandiae displaying radical-scavenging activity and oxidative mutagenicity: isolation of gentisyl alcohol. Mutat Res 2003; 539:187-94. [PMID: 12948827 DOI: 10.1016/s1383-5718(03)00166-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the search for new natural products with anti-oxidant activity, we have combined the cell-free assay based on the scavenging of the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), with a bioassay that detects oxidative mutagens. This bioassay uses a new Escherichia coli tester strain, IC203, specifically sensitive to oxidative stress due to a deficiency in the OxyR function. OxyR is a redox-sensitive transcriptional activator of genes encoding anti-oxidant enzymes such as catalase and peroxiredoxin alkyl hydroperoxide reductase. The positive response observed in E. coli IC203 with several known anti-oxidants, including cysteine, catechol and ascorbic acid, suggested to us the usefulness of the mutagenicity assay for a rapid screening of anti-oxidant compounds. The extract from Penicillium novae-zeelandiae was found to scavenge the DPPH radical. Subsequently, guided by the DPPH-scavenging assay and the oxidative mutagenesis assay, we isolated and identified three compounds in fractions from that active extract: patulin (1). 3-hydroxybenzyl alcohol (2). and gentisyl alcohol (2,5-dihydroxybenzyl alcohol) (3). Of these, gentisyl alcohol showed both DPPH-scavenging activity and oxidative mutagenicity. This compound also gave rise to intracellular formation of superoxide, evaluated by monitoring the oxidation of dihydroethidium, and was able to inhibit mutagenesis induced by the model oxidant t-butyl hydroperoxide (t-BuOOH).
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Affiliation(s)
- Cristina Alfaro
- Centro de Ecología Química Agrícola, Universidad Politécnica de Valencia, Edificio 9B (Lab 111), Campus de Vera, 46022 Valencia, Spain
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229
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Uprichard SL, Knipe DM. Conformational changes in the herpes simplex virus ICP8 DNA-binding protein coincident with assembly in viral replication structures. J Virol 2003; 77:7467-76. [PMID: 12805446 PMCID: PMC164794 DOI: 10.1128/jvi.77.13.7467-7476.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The herpes simplex virus (HSV) single-stranded DNA-binding protein, ICP8, is required for viral DNA synthesis. Before viral DNA replication, ICP8 colocalizes with other replication proteins at small punctate foci called prereplicative sites. With the onset of viral genome amplification, these proteins become redistributed into large globular replication compartments. Here we present the results of immunocytochemical and biochemical analysis of ICP8 showing that various antibodies recognize distinct forms of ICP8. Using these ICP8-specific antibodies as probes for ICP8 structure, we detected a time-dependent appearance and disappearance of ICP8 epitopes in immunoprecipitation assays. Immunofluorescence staining of ICP8 in cells infected with different HSV mutant viruses as well as cells transfected with a limited number of viral genes demonstrated that these and other antigenic changes occur coincident with ICP8 assembly at intranuclear replication structures. Genetic analysis has revealed a correlation between the ability of various ICP8 mutant proteins to form the 39S epitope and their ability to bind to DNA. These results support the hypothesis that ICP8 undergoes a conformational change upon binding to other HSV proteins and/or to DNA coincident with assembly into viral DNA replication structures.
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Affiliation(s)
- Susan L Uprichard
- Committee on Virology and Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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230
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Díaz-Rosales P, Chabrillón M, Moriñigo MA, Balebona MC. Survival against exogenous hydrogen peroxide of Photobacterium damselae subsp. piscicida under different culture conditions. JOURNAL OF FISH DISEASES 2003; 26:305-308. [PMID: 12962239 DOI: 10.1046/j.1365-2761.2003.00455.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Affiliation(s)
- P Díaz-Rosales
- Department of Microbiology, Faculty of Sciences, University of Málaga, Spain
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231
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Marnett LJ, Riggins JN, West JD. Endogenous generation of reactive oxidants and electrophiles and their reactions with DNA and protein. J Clin Invest 2003; 111:583-93. [PMID: 12618510 PMCID: PMC151910 DOI: 10.1172/jci18022] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Lawrence J Marnett
- Department of Biochemistry, Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Nashville, Tennessee, USA.
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232
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Marnett LJ, Riggins JN, West JD. Endogenous generation of reactive oxidants and electrophiles and their reactions with DNA and protein. J Clin Invest 2003. [DOI: 10.1172/jci200318022] [Citation(s) in RCA: 320] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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233
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Jung IL, Kim IG. Transcription of ahpC, katG, and katE genes in Escherichia coli is regulated by polyamines: polyamine-deficient mutant sensitive to H2O2-induced oxidative damage. Biochem Biophys Res Commun 2003; 301:915-22. [PMID: 12589799 DOI: 10.1016/s0006-291x(03)00064-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polyamines (putrescine and spermidine) are present in almost all living organisms and participate in numerous cellular processes. In this study, we report the protective roles of polyamines against hydrogen peroxide (H2O2)-induced oxidative stress. All of ahpC, katG, and katE genes, known to participate in the antioxidant defense mechanism against H2O2-induced stress in Escherichia coli, failed to induce in the absence of polyamines during normal aerobic growth. The induction of both oxyR and rpoS gene expression, whose products are essential to induce ahpC, katG, and katE genes, was also absolutely dependent on polyamines. Polyamine-deficient E. coli mutant has increased susceptibility to exogenous H2O2, and this cell cytotoxicity was relieved to a wild-type level by addition of putrescine or spermidine (1mM), which restored the transcriptional induction of ahpC, katG, and katE genes. H2O2-removing capacity was measured in the mutant, showing a significantly low H2O2-removing capacity compared to the wild type when polyamines were not present. We concluded that the increased susceptibility of the polyamine-deficient E. coli mutant to H2O2 treatment resulted from an intracellular low level of H2O2-removing capacity through the failure of their regulons, ahpC, katG, and katE induction, as well as the failure of oxyR and rpoS induction.
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Affiliation(s)
- Il Lae Jung
- Department of Radiation Biology, Environmental Radiation Research Group, Korea Atomic Energy Research Institute, P.O. Box 105, 305-600, Yusong Taejon, Republic of Korea
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234
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Affiliation(s)
- Bruce N Ames
- Children's Hospital--Oakland Res Inst, Oakland, CA 94609-1673, USA.
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235
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Bhanoori M, Yellaturu CR, Ghosh SK, Hassid A, Jennings LK, Rao GN. Thiol alkylation inhibits the mitogenic effects of platelet-derived growth factor and renders it proapoptotic via activation of STATs and p53 and induction of expression of caspase1 and p21(waf1/cip1). Oncogene 2003; 22:117-30. [PMID: 12527914 DOI: 10.1038/sj.onc.1206065] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Thiols provide the major intracellular redox milieu and can undergo reversible oxidation and reduction. To understand the role of thiols in redox signaling events, we have studied the effect of N-ethylmaleimide, a specific thiol alkylating agent, on platelet-derived growth factor-BB (PDGF-BB)-induced mitogenesis in vascular smooth muscle cells (VSMC). Thiol alkylation inhibited PDGF-BB-induced expression of the Fos and Jun family proteins and AP-1 activity in VSMC. Thiol alkylation also inhibited PDGF-BB-induced expression of cyclin A and growth in these cells. In contrast, thiol alkylation enhanced and sustained the effect of PDGF-BB on the activation of the Jak STAT pathway, and this event was correlated with inhibition of protein tyrosine phosphatase lB activity. Thiol alkylation via inducing the expression of p21(waf1/cip1) in a STAT1- and p53-dependent manner antagonized the downregulation of this cell cycle inhibitory molecule by PDGF-BB. The inhibition of AP-1 and activation of STATs, particularly STAT1, by thiol alkylation correlated with increased production of active caspase 1 and apoptosis in VSMC. Together, these findings suggest a role for thiols in mediating mitogenic and/or apoptotic signaling events in VSMC. These results also show that a sustained change in the intracellular thiol redox state can convert a mitogen into a death promoter.
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Affiliation(s)
- Manjula Bhanoori
- Department of Pathology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA
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236
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Abstract
Oxidation can damage all biological macromolecules, and the survival of a cell therefore depends on its ability to control the level of oxidants. Microbes possess an astonishing variety of antioxidant defences, ranging from small, oxidant-scavenging molecules to self-regulating, homeostatic gene networks. Most often these antioxidant defences are activated by exposure to specific classes of oxidants. Interestingly, the isolation of pleiotropic mutations that impair or exacerbate the expression of subsets of oxidant-responsive genes led to the identification of global regulators. In a few, well-characterized cases, these regulators can transduce oxidative damage into gene regulation. Recently, the application of genomic tools to study the antioxidant responses of E. coli has both confirmed previous observations and provided evidence for a wealth of putative new anti-oxidant functions. Here, we review the remarkable diversity of antioxidant defence mechanisms, with emphasis on signal transduction by global regulator proteins and the corresponding genetic networks that protect the microbial cell against oxidative stress.
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Affiliation(s)
- Pablo J Pomposiello
- Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA 02115, USA
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237
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Puškarova A, Ferianc P, Kormanec J, Homerova D, Farewell A, Nyström T. Regulation of yodA encoding a novel cadmium-induced protein in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3801-3811. [PMID: 12480884 DOI: 10.1099/00221287-148-12-3801] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bacterial accommodation to moderate concentrations of cadmium is accompanied by transient activation of general stress proteins as well as a sustained induction of other proteins of hitherto unknown functions. One of the latter proteins was previously identified as the product of the Escherichia coli yodA ORF. The yodA ORF encodes 216 aa residues (the YodA protein) and the increased synthesis of YodA during cadmium stress was found probably to be a result of transcriptional activation from one single promoter upstream of the structural yodA gene. Analysis of a transcriptional gene fusion, P(yodA)-lacZ, demonstrated that basal expression of yodA is low during exponential growth and expression is increased greater than 50-fold by addition of cadmium to growing cells. However, challenging cells with additional metals such as zinc, copper, cobalt and nickel did not increase the level of yodA expression. In addition, hydrogen peroxide also increased yodA expression whereas the superoxide-generating agent paraquat failed to do so. Surprisingly, cadmium-induced transcription of yodA is dependent on soxS and fur, but independent of oxyR. Moreover, a double relA spoT mutation abolished induction of yodA during cadmium exposure but ppGpp is not sufficient to induce yodA since expression of the gene is not elevated during stationary phase. After 45 min of cadmium exposure the YodA protein was primarily detected in the cytoplasmic fraction but was later (150 min) found in both the cytoplasmic and periplasmic compartments.
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Affiliation(s)
- A Puškarova
- Institute of Molecular Biology of the Slovak Academy of Sciences, Dúbravská cesta 21, SK-84251 Bratislava, Slovak Republic1
| | - P Ferianc
- Institute of Molecular Biology of the Slovak Academy of Sciences, Dúbravská cesta 21, SK-84251 Bratislava, Slovak Republic1
| | - J Kormanec
- Institute of Molecular Biology of the Slovak Academy of Sciences, Dúbravská cesta 21, SK-84251 Bratislava, Slovak Republic1
| | - D Homerova
- Institute of Molecular Biology of the Slovak Academy of Sciences, Dúbravská cesta 21, SK-84251 Bratislava, Slovak Republic1
| | - A Farewell
- Department of Cell and Molecular Biology, Göteborg University, Medicinaregatan 9C, SE-41390 Göteborg, Sweden2
| | - T Nyström
- Institute of Molecular Biology of the Slovak Academy of Sciences, Dúbravská cesta 21, SK-84251 Bratislava, Slovak Republic1
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238
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Zenteno-Savín T, Clayton-Hernández E, Elsner R. Diving seals: are they a model for coping with oxidative stress? Comp Biochem Physiol C Toxicol Pharmacol 2002; 133:527-36. [PMID: 12458181 DOI: 10.1016/s1532-0456(02)00075-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The diving lifestyle of seals depends upon cardiovascular adjustments that result in frequent vasoconstriction of numerous organs. With the first post-dive breath, reperfusion allows for eliminating accumulated carbon dioxide (CO(2)) and reloading oxygen (O(2)) stores. Reintroduction of oxygenated blood raises the potential for production of reactive oxygen species (ROS) and the possibility that they may overwhelm the antioxidant defenses. This study addresses the question of possible adaptive responses that allow ringed seal (Phoca hispida) tissues to tolerate repeated cycles of ischemia and reperfusion, and thus protect them from oxidative insult. We obtained samples of ringed seal heart, muscle and kidney through the cooperation of native subsistence hunters at Barrow, Alaska. Samples were subjected to oxidative stress by addition of xanthine oxidase. Production of superoxide radical (O(2)(.-)), lipid peroxidation (as determined by the presence of thiobarbituric acid reactive substances, TBARS) and antioxidant capacity (AOX) were quantified by spectrophotometric analysis. Similarly treated pig tissues were anticipated to be more susceptible to oxidative stress. Contrary to expectations, pig tissues revealed less O(2)(.-) and TBARS compared with ringed seal tissues. These results show that ringed seal muscle, heart and kidney can be induced in vitro to generate ROS, and suggest that the living seal's protective defenses may depend upon O(2)(.-) production, similar to the protective effect of experimental preconditioning, or on enhanced intermediate scavenging, as evidenced by the larger AOX found in ringed seal tissues.
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Affiliation(s)
- T Zenteno-Savín
- Centro de Investigaciones Biológicas del Noroeste, S C, Acuacultura y Biotecnologi;a Marina, Apartado Postal 128, La Paz, Baja California Sur, CP 23000, Mexico.
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239
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240
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Helmann JD. OxyR: a molecular code for redox sensing? SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2002; 2002:pe46. [PMID: 12419849 DOI: 10.1126/stke.2002.157.pe46] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Helmann discusses the controversy surrounding the activation of the bacterial redox-regulated transcription factor OxyR. Evidence from different sources, including crystallographic data, has led to opposing models for the chemical changes that activate OxyR. Is it an intramolecular disulfide-linkage? Is it oxidation of a single cysteine residue to a sulfenic acid? Are there different active forms depending on the type of cysteine modification: intramolecular disulfide bond, sulfenic acid, S-nitrosothiol, or mixed disulfide with glutathione? These issues are discussed in the broader context of transcriptional regulation and how particular regulators may activate distinct genetic programs depending on the precise state of the regulator produced in response to environmental cues.
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Affiliation(s)
- John D Helmann
- Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA.
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241
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Yellaturu CR, Bhanoori M, Neeli I, Rao GN. N-Ethylmaleimide inhibits platelet-derived growth factor BB-stimulated Akt phosphorylation via activation of protein phosphatase 2A. J Biol Chem 2002; 277:40148-55. [PMID: 12171932 DOI: 10.1074/jbc.m206376200] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The redox state plays an important role in gene regulation. Thiols maintain the intracellular redox homeostasis. To understand the role of thiols in redox signaling, we have studied the effect of thiol alkylation on platelet-derived growth factor-BB (PDGF-BB)-induced cell survival events in vascular smooth muscle cells. PDGF-BB stimulated Akt phosphorylation predominantly at Ser-473. N-Ethylmaleimide (NEM), a thiol alkylating agent, blocked PDGF-BB-induced Akt phosphorylation without affecting its upstream phosphatidylinositol 3-kinase (PI3K). On the other hand, LY294002 and wortmannin, specific inhibitors of PI3K, prevented PDGF-BB-induced phosphorylation of Akt and its downstream effector molecules, p70S6K, ribosomal protein S6, 4E-BP1, and eIF4E. NEM also abrogated the phosphorylation of p70S6K, ribosomal protein S6, 4E-BP1, and eIF4E induced by PDGF-BB, suggesting that thiol alkylation interferes with the PI3K/Akt pathway at the level of Akt. In addition, NEM blocked PDGF-BB-induced phosphorylation of BAD and forkhead transcription factor FKHR-L1, and these events correlated with increased apoptosis. NEM alone and in concert with PDGF-BB increased reactive oxygen species (ROS) production and protein phosphatase 2A (PP2A) activity in VSMC. The inhibition of PDGF-BB-induced Akt phosphorylation by NEM was completely reversed by PP2A inhibitors fostriecin and okadaic acid, ceramide synthase inhibitor fumonisin B1, and ROS scavenger N-acetylcysteine (NAC). NAC also attenuated the apoptosis induced by NEM, alone or in combination with PDGF-BB. Together, these findings demonstrate for the first time that PP2A mediates thiol alkylation-dependent redox regulation of Akt and cell survival.
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Affiliation(s)
- Chandrahasa R Yellaturu
- Department of Physiology and Center for Vascular Biology, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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242
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Hahn JS, Oh SY, Roe JH. Role of OxyR as a peroxide-sensing positive regulator in Streptomyces coelicolor A3(2). J Bacteriol 2002; 184:5214-22. [PMID: 12218006 PMCID: PMC137946 DOI: 10.1128/jb.184.19.5214-5222.2002] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genes encoding a homolog of Escherichia coli OxyR (oxyR) and an alkyl hydroperoxide reductase system (ahpC and ahpD) have been isolated from Streptomyces coelicolor A3(2). The ahpC and ahpD genes constitute an operon transcribed divergently from the oxyR gene. Expression of both ahpCD and oxyR genes was maximal at early exponential phase and decreased rapidly as cells entered mid-exponential phase. Overproduction of OxyR in Streptomyces lividans conferred resistance against cumene hydroperoxide and H2O2. The oxyR mutant produced fewer ahpCD and oxyR transcripts than the wild type, suggesting that OxyR acts as a positive regulator for their expression. Both oxyR and ahpCD transcripts increased more than fivefold within 10 min of H2O2 treatment and decreased to the normal level in 50 min, with kinetics similar to those of the CatR-mediated induction of the catalase A gene (catA) by H2O2. The oxyR mutant failed to induce oxyR and ahpCD genes in response to H2O2, indicating that OxyR is the modulator for the H2O2-dependent induction of these genes. Purified OxyR protein bound specifically to the intergenic region between ahpC and oxyR, suggesting its direct role in regulating these genes. These results demonstrate that in S. coelicolor OxyR mediates H2O2 induction of its own gene and genes for alkyl hydroperoxide reductase system, but not the catalase gene (catA), unlike in Escherichia coli and Salmonella enterica serovar Typhimurium.
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Affiliation(s)
- Ji-Sook Hahn
- Laboratory of Molecular Microbiology, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea
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243
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Karimpour S, Lou J, Lin LL, Rene LM, Lagunas L, Ma X, Karra S, Bradbury CM, Markovina S, Goswami PC, Spitz DR, Hirota K, Kalvakolanu DV, Yodoi J, Gius D. Thioredoxin reductase regulates AP-1 activity as well as thioredoxin nuclear localization via active cysteines in response to ionizing radiation. Oncogene 2002; 21:6317-27. [PMID: 12214272 DOI: 10.1038/sj.onc.1205749] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2002] [Revised: 05/28/2002] [Accepted: 06/07/2002] [Indexed: 11/09/2022]
Abstract
A recently identified class of signaling factors uses critical cysteine motif(s) that act as redox-sensitive 'sulfhydryl switches' to reversibly modulate specific signal transduction cascades regulating downstream proteins with similar redox-sensitive sites. For example, signaling factors such as redox factor-1 (Ref-1) and transcription factors such as the AP-1 complex both contain redox-sensitive cysteine motifs that regulate activity in response to oxidative stress. The mammalian thioredoxin reductase-1 (TR) is an oxidoreductase selenocysteine-containing flavoprotein that also appears to regulate multiple downstream intracellular redox-sensitive proteins. Since ionizing radiation (IR) induces oxidative stress as well as increases AP-1 DNA-binding activity via the activation of Ref-1, the potential roles of TR and thioredoxin (TRX) in the regulation of AP-1 activity in response to IR were investigated. Permanently transfected cell lines that overexpress wild type TR demonstrated constitutive increases in AP-1 DNA-binding activity as well as AP-1-dependent reporter gene expression, relative to vector control cells. In contrast, permanently transfected cell lines expressing a TR gene with the active site cysteine motif deleted were unable to induce AP-1 activity or reporter gene expression in response to IR. Transient genetic overexpression of either the TR wild type or dominant-negative genes demonstrated similar results using a transient assay system. One mechanism through which TR regulates AP-1 activity appears to involve TRX sub-cellular localization, with no change in the total TRX content of the cell. These results identify a novel function of the TR enzyme as a signaling factor in the regulation of AP-1 activity via a cysteine motif located in the protein.
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Affiliation(s)
- Shervin Karimpour
- Radiation Oncology Branch, Radiation Oncology Sciences Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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244
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Loprasert S, Sallabhan R, Whangsuk W, Mongkolsuk S. The Burkholderia pseudomallei oxyR gene: expression analysis and mutant characterization. Gene 2002; 296:161-9. [PMID: 12383513 DOI: 10.1016/s0378-1119(02)00854-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Burkholderia pseudomallei (Bp) is the causative agent of the life-threatening melioidosis in humans. The global transcription factor oxyR gene was isolated and characterized. It is located between recG, encoding a putative DNA helicase, and katG, encoding a putative catalase-peroxidase. oxyR is expressed as a monocistronic 1 kb mRNA and is induced by oxidative stress compounds. Northern, primer extension, and transcription reporter fusion analyses showed that oxyR mRNA is induced by 0.2 mM menadione, 2 mM paraquat, and 10 mM H(2)O(2). Two knockout mutants of oxyR were constructed, by single- and double-crossover recombination, and found to be hypersensitive to H(2)O(2) and paraquat. Bp lacking OxyR exhibited autoaggregation when cultured in liquid broth and an increased ability to form biofilms in minimal medium, but not in Luria-Bertani broth. The oxyR mutants also have a decreased level of extracellular protease activity. The altered phenotypes of oxyR deficient mutants were complemented when a copy of oxyR was transposed into the mutant chromosomes on the mini-Tn5 transposon.
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Affiliation(s)
- Suvit Loprasert
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.
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245
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Abstract
Heme oxygenase-1 (HO-1) is an inducible stress protein the expression of which can be markedly augmented in eukaryotes by a wide range of substances that cause a transient change in the cellular redox state. The importance of this protein in physiology and disease is underlined by the versatility of HO-1 inducers and the functional role attributed to HO-1 products (carbon monoxide and bilirubin) in conditions that are associated with moderate or severe cellular stress. An intriguing aspect is the recent evidence showing that nitric oxide, a ubiquitous signaling molecule, finely modulates the activation of HO-1 expression. As the effects of oxidative stress on the regulation of the HO-1 gene have been well established and characterized, this review will focus on the biological relevance of redox signals involving nitric oxide and reactive nitrogen species that lead to up-regulation of the HO-1 pathway, with particular emphasis on vascular tissues and the cardiovascular system.
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Affiliation(s)
- Roberto Motterlini
- Vascular Biology Unit, Department of Surgical Research, Northwick Park Institute for Medical Research, Harrow, Middlesex, UK.
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246
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Grimm M, Spiecker M, De Caterina R, Shin WS, Liao JK. Inhibition of major histocompatibility complex class II gene transcription by nitric oxide and antioxidants. J Biol Chem 2002; 277:26460-7. [PMID: 12006557 DOI: 10.1074/jbc.m110538200] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interferon (IFN)-gamma facilitates cellular immune response, in part, by inducing the expression of major histocompatibility complex class II (MHC-II) molecules. We demonstrate that IFN-gamma induces the expression of HLA-DRA in vascular endothelial cells via mechanisms involving reactive oxygen species. IFN-gamma-induced HLA-DRA expression was inhibited by nitric oxide (NO) and antioxidants such as superoxide dismutase, catalase, pyrrolidine dithiocarbamate, and N-acetylcysteine. Nuclear run-on assays demonstrated that NO and antioxidants inhibited IFN-gamma-induced HLA-DRA gene transcription. Transient transfection studies using a fully functional HLA-DRA promoter construct ([-300]DR alpha.CAT) showed that inhibition of endogenous NO synthase activity by N(omega)-monomethyl-l-arginine or addition of exogenous hydrogen peroxide (H(2)O(2)) augmented basal and IFN-gamma-stimulated [-300]DR alpha.CAT activity. However, H(2)O(2) and N(omega)-monomethyl-l-arginine could induce HLA-DRA expression suggesting that H(2)O(2) is a necessary but not a sufficient mediator of IFN-gamma-induced HLA-DRA expression. Electrophoretic mobility shift assay and Western blotting demonstrated that NO and antioxidants had little or no effect on IFN-gamma-induced IRF-1 activation or MHC-II transactivator (CIITA) expression but did inhibit IFN-gamma-induced activation of STAT1 alpha (p91) and Y box transcription factors, NF-Y(A) and NF-Y(B). These results indicate that NO and antioxidants may attenuate vascular inflammation by antagonizing the effects of intracellular reactive oxygen species generation by IFN-gamma, which is necessary for MHC-II gene transcription.
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Affiliation(s)
- Michael Grimm
- Vascular Medicine Unit, Brigham & Women's Hospital and Harvard Medical School, Boston, Masachusetts 02115, USA
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247
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Kaushal D, Schroeder BG, Tyagi S, Yoshimatsu T, Scott C, Ko C, Carpenter L, Mehrotra J, Manabe YC, Fleischmann RD, Bishai WR. Reduced immunopathology and mortality despite tissue persistence in a Mycobacterium tuberculosis mutant lacking alternative sigma factor, SigH. Proc Natl Acad Sci U S A 2002; 99:8330-5. [PMID: 12060776 PMCID: PMC123067 DOI: 10.1073/pnas.102055799] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The pathogenesis of tuberculosis involves multiple phases and is believed to involve both a carefully deployed series of adaptive bacterial virulence factors and inappropriate host immune responses that lead to tissue damage. A defined Mycobacterium tuberculosis mutant strain lacking the sigH-encoded transcription factor showed a distinctive infection phenotype. In resistant C57BL/6 mice, the mutant achieved high bacterial counts in lung and spleen that persisted in tissues in a pattern identical to those of wild-type bacteria. Despite a high bacterial burden, the mutant produced a blunted, delayed pulmonary inflammatory response, and recruited fewer CD4(+) and CD8(+) T cells to the lung in the early stages of infection. In susceptible C3H mice, the mutant again showed diminished immunopathology and was nonlethal at over 170 days after intravenous infection, in contrast to isogenic wild-type bacilli, which killed with a median time to death of 52 days. Complete genomic microarray analysis revealed that M. tuberculosis sigH may mediate the transcription of at least 31 genes directly and that it modulates the expression of about 150 others; the SigH regulon governs thioredoxin recycling and may be involved in the maintenance of intrabacterial reducing capacity. These data show that the M. tuberculosis sigH gene is dispensable for bacterial growth and survival within the host, but is required for the production of immunopathology and lethality. This phenotype demonstrates that beyond an ability to grow and persist within the host, M. tuberculosis has distinct virulence mechanisms that elicit deleterious host responses and progressive pulmonary disease.
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Affiliation(s)
- Deepak Kaushal
- Department of Medicine, Center for Tuberculosis Research, Johns Hopkins School of Medicine, 424 North Bond Street, Baltimore, MD 21231, USA
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248
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Yamamura E, Lee EH, Kuzumaki A, Uematsu N, Nunoshiba T, Kawata M, Yamamoto K. Characterization of spontaneous mutation in the delta soxR and SoxS overproducing strains of Escherichia coli. JOURNAL OF RADIATION RESEARCH 2002; 43:195-203. [PMID: 12238334 DOI: 10.1269/jrr.43.195] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To examine the role of the soxRS regulon in mutagenesis, we characterized the spontaneous mutations occurring in the endogenous tonB gene in the delta soxR strain and the SoxS overproducing strain of Escherichia coli. Neither the delta soxR strain nor the SoxS overproducing strain led to an enhancement or diminishment of the spontaneous mutation frequency. By DNA sequencing, we determined 50 spontaneous mutants from the delta soxR strains, and found that 36% were both base substitutions and IS insertions, 14% frameshifts and 10% deletions. Among the base substitutions, G:C-->T:A transversions and G:C-->A:T transitions predominated, followed by A:T-->T:A transversions. We determined 54 spontaneous mutants from the SoxS overproducing strains, and found that 37% were IS insertions, 31% base substitutions, 17% frameshifts, 9% deletions and 6% duplications. Among the base substitutions, G:C-->T:A transversions dominated, followed by A:T-->T:A transversions and G:C-->A:T transitions. These results were similar to those from the soxRS+ strains. Thus, it is suggested that the soxRS-regulated genes do not play a significant role in the defense against spontaneous mutagenesis.
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Affiliation(s)
- Eiji Yamamura
- Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Miyagi 980-8577, Japan
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249
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Kim SO, Merchant K, Nudelman R, Beyer WF, Keng T, DeAngelo J, Hausladen A, Stamler JS. OxyR: a molecular code for redox-related signaling. Cell 2002; 109:383-96. [PMID: 12015987 DOI: 10.1016/s0092-8674(02)00723-7] [Citation(s) in RCA: 362] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Redox regulation has been perceived as a simple on-off switch in proteins (corresponding to reduced and oxidized states). Using the transcription factor OxyR as a model, we have generated, in vitro, several stable, posttranslational modifications of the single regulatory thiol (SH), including S-NO, S-OH, and S-SG, and shown that each occurs in vivo. These modified forms of OxyR are transcriptionally active but differ in structure, cooperative properties, DNA binding affinity, and promoter activities. OxyR can thus process different redox-related signals into distinct transcriptional responses. More generally, our data suggest a code for redox control through which allosteric proteins can subserve either graded (cooperative) or maximal (noncooperative) responses, and through which differential responsivity to redox-related signals can be achieved.
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Affiliation(s)
- Sung Oog Kim
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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250
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Waldron DE, Owen P, Dorman CJ. Competitive interaction of the OxyR DNA-binding protein and the Dam methylase at the antigen 43 gene regulatory region in Escherichia coli. Mol Microbiol 2002; 44:509-20. [PMID: 11972787 DOI: 10.1046/j.1365-2958.2002.02905.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The antigen 43 surface protein of Escherichia coli is expressed in a phase-variable manner by a mechanism involving alternative activation and repression of transcription of the agn43 gene. The repressor is the OxyR DNA-binding protein, and its binding site was found to be located downstream of the agn43 transcription start site in a region of DNA that encompasses three 5'-GATC-3' sequences that are subject to Dam-mediated DNA methylation. It has been suggested previously that the phase-variable expression of antigen 43 results from a competition between Dam methylase and the OxyR repressor for these sites. The 5'-GATC-3' sequences were inactivated for methylation by site-directed mutagenesis, and all possible combinations of inactive and active sites were assessed for effects on phase-variable expression of the agn43 gene. Inactivation of any 5'-GATC-3' site individually had no effect; at least two sites had to be inactivated to disrupt the normal pattern of expression. Studies of OxyR interaction with agn43 DNA showed that methylation of any two 5'-GATC-3' sites was necessary and sufficient to block binding of the repressor. It was also found that the adenines of the second and third 5'-GATC-3' sites are required for OxyR binding, demonstrating that the sites for Dam methylation and for repressor binding are intimately associated. This is consistent with a competition model in which Dam and OxyR share a preference for specific DNA sequences in the regulatory region of the agn43 gene.
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Affiliation(s)
- Denise E Waldron
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Republic of Ireland
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