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Abstract
SIGNIFICANCE Glutaredoxins (Grxs) are small oxidoreductases of the thioredoxin family of proteins regulating the thiol redox state of several proteins. Thereby, Grxs are key elements in redox signaling. RECENT ADVANCES Redox signaling via protein thiols depends on reversible oxidative modifications induced mainly by reactive oxygen/nitrogen species and glutathione (GSH) in form of its oxidized disulfide or S-nitroso-glutathione. Grxs contribute to redox signaling by the catalysis of glutathionylation, de-glutathionylation, as well as reduction of disulfide bridges via two distinct enzymatic mechanisms. The dithiol mechanism utilizes both active site cysteines to reduce disulfides, whereas the monothiol mechanism utilizes only the N-terminal active site cysteine for the reduction of GSH mixed disulfides. The sphere of action of Grxs continues to grow with the recent identification of novel targets. CRITICAL ISSUES Because of limited methodological tools, the identification of new substrates for oxidoreductases in general is one of the biggest challenges in this research area. FUTURE DIRECTIONS With this review, we provide a condensed summary of the current knowledge of thiol/disulfide exchange reactions catalyzed by Grxs regarding the mechanistic, structural, and functional aspects. The latter will be of high importance for future research directions, gaining novel insights into redox signaling in general, and the role of Grxs in particular.
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Affiliation(s)
- Christopher Horst Lillig
- Institut für Biochemie und Molekularbiologie, Universitätsmedizin Greifswald, Ernst Moritz Arndt-Universität Greifswald, Greifswald, Germany
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52
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Abstract
Grxs (glutaredoxins) are small ubiquitous redox enzymes. They are generally involved in the reduction of oxidative modifications using glutathione. Grxs are not only able to reduce protein disulfides and the low-molecular-mass antioxidant dehydroascorbate, but also represent the major enzyme class responsible for deglutathionylation reactions. Functional proteomics, including interaction studies, comparative activity measurements using heterologous proteins and structural analysis are combined to provide important insights into the crucial function of Grxs in cellular redox networks. Summarizing the current understanding of Grxs, with a special focus on organelle-localized members across species, genus and kingdom boundaries (including cyanobacteria, plants, bacteria, yeast and humans) lead to two different classifications, one according to sequence structure that gives insights into the diversification of Grxs, and another according to function within the cell that provides a basis for assessing the different roles of Grxs.
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53
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Meyer Y, Belin C, Delorme-Hinoux V, Reichheld JP, Riondet C. Thioredoxin and glutaredoxin systems in plants: molecular mechanisms, crosstalks, and functional significance. Antioxid Redox Signal 2012; 17:1124-60. [PMID: 22531002 DOI: 10.1089/ars.2011.4327] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Thioredoxins (Trx) and glutaredoxins (Grx) constitute families of thiol oxidoreductases. Our knowledge of Trx and Grx in plants has dramatically increased during the last decade. The release of the Arabidopsis genome sequence revealed an unexpectedly high number of Trx and Grx genes. The availability of several genomes of vascular and nonvascular plants allowed the establishment of a clear classification of the genes and the chronology of their appearance during plant evolution. Proteomic approaches have been developed that identified the putative Trx and Grx target proteins which are implicated in all aspects of plant growth, including basal metabolism, iron/sulfur cluster formation, development, adaptation to the environment, and stress responses. Analyses of the biochemical characteristics of specific Trx and Grx point to a strong specificity toward some target enzymes, particularly within plastidial Trx and Grx. In apparent contradiction with this specificity, genetic approaches show an absence of phenotype for most available Trx and Grx mutants, suggesting that redundancies also exist between Trx and Grx members. Despite this, the isolation of mutants inactivated in multiple genes and several genetic screens allowed the demonstration of the involvement of Trx and Grx in pathogen response, phytohormone pathways, and at several control points of plant development. Cytosolic Trxs are reduced by NADPH-thioredoxin reductase (NTR), while the reduction of Grx depends on reduced glutathione (GSH). Interestingly, recent development integrating biochemical analysis, proteomic data, and genetics have revealed an extensive crosstalk between the cytosolic NTR/Trx and GSH/Grx systems. This crosstalk, which occurs at multiple levels, reveals the high plasticity of the redox systems in plants.
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Affiliation(s)
- Yves Meyer
- Laboratoire Génome et Développement des Plantes, Université de Perpignan, Perpignan, France
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54
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Abstract
SIGNIFICANCE Parasitic infections continue to be a major problem for global human health. Vaccines are practically not available and chemotherapy is highly unsatisfactory. One approach toward a novel antiparasitic drug development is to unravel pathways that may be suited as future targets. Parasitic organisms show a remarkable diversity with respect to the nature and functions of their main low-molecular-mass antioxidants and many of them developed pathways that do not have a counterpart in their mammalian hosts. RECENT ADVANCES Work of the last years disclosed the individual antioxidants employed by parasites and their distinct pathways. Entamoeba, Trichomonas, and Giardia directly use cysteine as main low-molecular-mass thiol but have divergent cysteine metabolisms. Malarial parasites rely exclusively on cysteine uptake and generate glutathione (GSH) as main free thiol as do metazoan parasites. Trypanosomes and Leishmania have a unique trypanothione-based thiol metabolism but employ individual mechanisms for their cysteine supply. In addition, some trypanosomatids synthesize ovothiol A and/or ascorbate. Various essential parasite enzymes such as trypanothione synthetase and trypanothione reductase in Trypanosomatids and the Schistosoma thioredoxin GSH reductase are currently intensively explored as drug target molecules. CRITICAL ISSUES Essentiality is a prerequisite but not a sufficient property of an enzyme to become a suited drug target. The availability of an appropriate in vivo screening system and many other factors are equally important. FUTURE DIRECTIONS The current organism-wide RNA-interference and proteome analyses are supposed to reveal many more interesting candidates for future drug development approaches directed against the parasite antioxidant defense systems.
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55
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Abstract
SIGNIFICANCE Cysteine residues of proteins participate in the catalysis of biochemical reactions, are crucial for redox reactions, and influence protein structure by the formation of disulfide bonds. Covalent posttranslational modifications (PTMs) of cysteine residues are important mediators of redox regulation and signaling by coupling protein activity to the cellular redox state, and moreover influence stability, function, and localization of proteins. A diverse group of protozoan and metazoan parasites are a major cause of diseases in humans, such as malaria, African trypanosomiasis, leishmaniasis, toxoplasmosis, filariasis, and schistosomiasis. RECENT ADVANCES Human parasites undergo dramatic morphological and metabolic changes while they pass complex life cycles and adapt to changing environments in host and vector. These processes are in part regulated by PTMs of parasitic proteins. In human parasites, posttranslational cysteine modifications are involved in crucial cellular events such as signal transduction (S-glutathionylation and S-nitrosylation), redox regulation of proteins (S-glutathionylation and S-nitrosylation), protein trafficking and subcellular localization (palmitoylation and prenylation), as well as invasion into and egress from host cells (palmitoylation). This review focuses on the occurrence and mechanisms of these cysteine modifications in parasites. CRITICAL ISSUES Studies on cysteine modifications in human parasites are so far largely based on in vitro experiments. FUTURE DIRECTIONS The in vivo regulation of cysteine modifications and their role in parasite development will be of great interest in order to understand redox signaling in parasites.
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Affiliation(s)
- Esther Jortzik
- Interdisciplinary Research Center, Justus Liebig University, Giessen, Germany
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56
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Flohé L. The trypanothione system and its implications in the therapy of trypanosomatid diseases. Int J Med Microbiol 2012; 302:216-20. [PMID: 22889611 DOI: 10.1016/j.ijmm.2012.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Biosynthesis and the use of trypanothione, a redox metabolite of parasitic trypanosomatids, are reviewed here with special emphasis on the development of trypanocidal drugs. This metabolic system is unique to and essential for the protozoal parasites. Selective inhibition of key elements of trypanothione metabolism, therefore, promises eradication of the parasites without affecting the host. Considering the metabolic importance and drugability of system components, inhibition of the enzymes for regeneration and de novo synthesis of trypanothione is rated as the most promising approach, while related peroxidases and redoxins are disregarded as targets because of limited chances to achieve selective inhibition. The organizational need to exploit the accumulating knowledge of trypanosomatid metabolism for medical practice is briefly addressed.
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Affiliation(s)
- Leopold Flohé
- Department of Chemistry, Otto-von-Guericke-Universität, Universitätsplatz 2, 39106 Magdeburg, Germany.
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57
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Leishmania TDR1 structure, a unique trimeric glutathione transferase capable of deglutathionylation and antimonial prodrug activation. Proc Natl Acad Sci U S A 2012; 109:11693-8. [PMID: 22753509 DOI: 10.1073/pnas.1202593109] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Thiol-dependent reductase I (TDR1), an enzyme found in parasitic Leishmania species and Trypanosoma cruzi, is implicated in deglutathionylation and activation of antimonial prodrugs used to treat leishmaniasis. The 2.3 Å resolution structure of TDR1 reveals a unique trimer of subunits each containing two glutathione-S-transferase (GST) domains. The similarities of individual domains and comparisons with GST classes suggest that TDR1 evolved by gene duplication, diversification, and gene fusion; a combination of events previously unknown in the GST protein superfamily and potentially explaining the distinctive enzyme properties of TDR1. The deglutathionylation activity of TDR1 implies that glutathione itself has regulatory intracellular roles in addition to being a precursor for trypanothione, the major low mass thiol present in trypanosomatids. We propose that activation of antiparasite Sb(V)-drugs is a legacy of the deglutathionylation activity of TDR1 and involves processing glutathione adducts with concomitant reduction of the metalloid to active Sb(III) species.
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58
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Ouna BA, Stewart M, Helbig C, Clayton C. The Trypanosoma brucei CCCH zinc finger proteins ZC3H12 and ZC3H13. Mol Biochem Parasitol 2012; 183:184-8. [PMID: 22366391 DOI: 10.1016/j.molbiopara.2012.02.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 02/08/2012] [Accepted: 02/10/2012] [Indexed: 01/07/2023]
Abstract
CCCH-type zinc finger proteins have various roles in RNA metabolism. We here analysed the functional relevance of two such proteins from Trypanosoma brucei, TbZC3H12 and TbZC3H13. Each protein has a single CCCH motif very similar to those seen in metazoan proteins that regulate mRNA degradation. TbZC3H12 is expressed in bloodstream form parasites at low levels. It is phosphorylated, cytosolic and not required for normal growth of cultured bloodstream trypanosomes. RNA interference targeting TbZC3H13, on a TbZC3H12 null background, also had no effect on bloodstream trypanosome growth, but over-expression of tagged TbZC3H13 inhibited procyclic trypanosome growth. Tandem affinity purification of both proteins revealed various interesting potential interactions; specificity was assessed against a list of proteins that were found in 24 other pull-down experiments, which is provided. The conservation of TbZC3H12 in all kinetoplastids, and TbZC3H13 in Salivaria, suggests that the two proteins may be required for optimal growth at some stage of the parasite life-cycle.
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Affiliation(s)
- Benard Aswani Ouna
- Zentrum fur Molekular Biologie Heidelberg, ZMBH-DKFZ Alliance, Im Neuenheimerfeld 282, Heidelberg 69120, Germany
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59
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Zaffagnini M, Bedhomme M, Marchand CH, Couturier JRM, Gao XH, Rouhier N, Trost P, Lemaire SPD. Glutaredoxin s12: unique properties for redox signaling. Antioxid Redox Signal 2012; 16:17-32. [PMID: 21707412 DOI: 10.1089/ars.2011.3933] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
AIMS Cysteines (Cys) made acidic by the protein environment are generally sensitive to pro-oxidant molecules. Glutathionylation is a post-translational modification that can occur by spontaneous reaction of reduced glutathione (GSH) with oxidized Cys as sulfenic acids (-SOH). The reverse reaction (deglutathionylation) is strongly stimulated by glutaredoxins (Grx) and requires a reductant, often GSH. RESULTS Here, we show that chloroplast GrxS12 from poplar efficiently reacts with glutathionylated substrates in a GSH-dependent ping pong mechanism. The pK(a) of GrxS12 catalytic Cys is very low (3.9) and makes GrxS12 itself sensitive to oxidation by H(2)O(2) and to direct glutathionylation by nitrosoglutathione. Glutathionylated-GrxS12 (GrxS12-SSG) is temporarily inactive until it is deglutathionylated by GSH. The equilibrium between GrxS12 and glutathione (E(m(GrxS12-SSG))= -315 mV, pH 7.0) is characterized by K(ox) values of 310 at pH 7.0, as in darkened chloroplasts, and 69 at pH 7.9, as in illuminated chloroplasts. INNOVATION Based on thermodynamic data, GrxS12-SSG is predicted to accumulate in vivo under conditions of mild oxidation of the GSH pool that may occur under stress. Moreover, GrxS12-SSG is predicted to be more stable in chloroplasts in the dark than in the light. CONCLUSION These peculiar catalytic and thermodynamic properties could allow GrxS12 to act as a stress-related redox sensor, thus allowing glutathione to play a signaling role through glutathionylation of GrxS12 target proteins.
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Affiliation(s)
- Mirko Zaffagnini
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, FRE3354 Centre National de la Recherche Scientifique, Institut de Biologie Physico-Chimique, Université Pierre et Marie Curies, Paris, France
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60
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Roldán A, Comini MA, Crispo M, Krauth-Siegel RL. Lipoamide dehydrogenase is essential for both bloodstream and procyclic Trypanosoma brucei. Mol Microbiol 2011; 81:623-39. [DOI: 10.1111/j.1365-2958.2011.07721.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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61
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Hoffmann B, Uzarska MA, Berndt C, Godoy JR, Haunhorst P, Lillig CH, Lill R, Mühlenhoff U. The multidomain thioredoxin-monothiol glutaredoxins represent a distinct functional group. Antioxid Redox Signal 2011; 15:19-30. [PMID: 21299470 DOI: 10.1089/ars.2010.3811] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Monothiol glutaredoxins (Grxs) with a noncanonical CGFS active site are found in all kingdoms of life. They include members with a single domain and thioredoxin-Grx fusion proteins. In Saccharomyces cerevisiae, the multidomain Grx3 and Grx4 play an essential role in intracellular iron trafficking. This crucial task is mediated by an essential Fe/S cofactor. This study shows that this unique physiological role cannot be executed by single domain Grxs, because the thioredoxin domain is indispensable for function in vivo. Mutational analysis revealed that a CPxS active site motif is fully compatible with Fe/S cluster binding on Grx4, while a dithiol active site results in cofactor destabilization and a moderate impairment of in vivo function. These requirements for Fe/S cofactor stabilization on Grx4 are virtually the opposite of those previously reported for single domain Grxs. Grx4 functions as iron sensor for the iron-sensing transcription factor Aft1 in S. cerevisiae. We found that Aft1 binds to a conserved binding site at the C-terminus of Grx4. This interaction is essential for the regulation of Aft1. Collectively, our analysis demonstrates that the multidomain monothiol Grxs form a unique protein family distinct from that of the single domain Grxs.
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Affiliation(s)
- Bastian Hoffmann
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Germany
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62
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Couturier J, Ströher E, Albetel AN, Roret T, Muthuramalingam M, Tarrago L, Seidel T, Tsan P, Jacquot JP, Johnson MK, Dietz KJ, Didierjean C, Rouhier N. Arabidopsis chloroplastic glutaredoxin C5 as a model to explore molecular determinants for iron-sulfur cluster binding into glutaredoxins. J Biol Chem 2011; 286:27515-27. [PMID: 21632542 DOI: 10.1074/jbc.m111.228726] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Unlike thioredoxins, glutaredoxins are involved in iron-sulfur cluster assembly and in reduction of specific disulfides (i.e. protein-glutathione adducts), and thus they are also important redox regulators of chloroplast metabolism. Using GFP fusion, AtGrxC5 isoform, present exclusively in Brassicaceae, was shown to be localized in chloroplasts. A comparison of the biochemical, structural, and spectroscopic properties of Arabidopsis GrxC5 (WCSYC active site) with poplar GrxS12 (WCSYS active site), a chloroplastic paralog, indicated that, contrary to the solely apomonomeric GrxS12 isoform, AtGrxC5 exists as two forms when expressed in Escherichia coli. The monomeric apoprotein possesses deglutathionylation activity mediating the recycling of plastidial methionine sulfoxide reductase B1 and peroxiredoxin IIE, whereas the dimeric holoprotein incorporates a [2Fe-2S] cluster. Site-directed mutagenesis experiments and resolution of the x-ray crystal structure of AtGrxC5 in its holoform revealed that, although not involved in its ligation, the presence of the second active site cysteine (Cys(32)) is required for cluster formation. In addition, thiol titrations, fluorescence measurements, and mass spectrometry analyses showed that, despite the presence of a dithiol active site, AtGrxC5 does not form any inter- or intramolecular disulfide bond and that its activity exclusively relies on a monothiol mechanism.
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Affiliation(s)
- Jérémy Couturier
- Unité Mixte de Recherches 1136, Institut National de la Recherche Agronomique-Nancy Université, Interactions Arbres Microorganismes, Institut Fédératif de Recherche 110 Ecosystèmes Forestiers, Agroressources, Biomolécule et Alimentation, 54506 Vandoeuvre-lès-Nancy Cedex, France
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