RESUMO
H2O2 signals trigger adaptive responses affecting cell division, differentiation, migration, and survival. These signals are transduced by selective oxidation of cysteines on specific target proteins, with redox-sensitive cysteines now identified in many proteins, including both kinases and phosphatases. Assessing the contribution of these oxidation events to cell signalling presents several challenges including understanding how and when the selective oxidation of specific proteins takes place in vivo. In recent years, a combination of biochemical, structural, genetic, and computational approaches in fungi, plants, and animals have revealed different ways in which thiol peroxidases (peroxiredoxins) are bypassed or utilised in relaying these signals. Together, these mechanisms provide a conceptual framework for selectively oxidising proteins that will further advance understanding of how redox modifications contribute to health and disease.
Assuntos
Peróxido de Hidrogênio , Oxirredução , Transdução de Sinais , Animais , Peróxido de Hidrogênio/metabolismo , Humanos , Peroxirredoxinas/metabolismoRESUMO
A critical feature of the cellular antioxidant response is the induction of gene expression by redox-sensitive transcription factors. In many cells, activating these transcription factors is a dynamic process involving multiple redox steps, but it is unclear how these dynamics should be measured. Here, we show how the dynamic profile of the Schizosaccharomyces pombe Pap1 transcription factor is quantifiable by three parameters: signal amplitude, signal time and signal duration. In response to increasing hydrogen peroxide concentrations, the Pap1 amplitude decreased while the signal time and duration showed saturable increases. In co-response plots, these parameters showed a complex, non-linear relationship to the mRNA levels of four Pap1-regulated genes. We also demonstrate that hydrogen peroxide and tert-butyl hydroperoxide trigger quantifiably distinct Pap1 activation profiles and transcriptional responses. Based on these findings, we propose that different oxidants and oxidant concentrations modulate the Pap1 dynamic profile, leading to specific transcriptional responses. We further show how the effect of combination and pre-exposure stresses on Pap1 activation dynamics can be quantified using this approach. This method is therefore a valuable addition to the redox signalling toolbox that may illuminate the role of dynamics in determining appropriate responses to oxidative stress.
Assuntos
Peróxido de Hidrogênio , Oxirredução , Proteínas de Schizosaccharomyces pombe , Schizosaccharomyces , Transdução de Sinais , Proteínas de Schizosaccharomyces pombe/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Schizosaccharomyces/metabolismo , Schizosaccharomyces/genética , Peróxido de Hidrogênio/metabolismo , terc-Butil Hidroperóxido/farmacologia , Proteínas Associadas a Pancreatite/metabolismo , Proteínas Associadas a Pancreatite/genética , Regulação Fúngica da Expressão Gênica , Estresse Oxidativo , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/genética , Oxidantes/farmacologia , Oxidantes/metabolismoRESUMO
Peroxiredoxins (Prdxs) utilize reversibly oxidized cysteine residues to reduce peroxides and promote H2O2 signal transduction, including H2O2-induced activation of P38 MAPK. Prdxs form H2O2-induced disulfide complexes with many proteins, including multiple kinases involved in P38 MAPK signaling. Here, we show that a genetically encoded fusion between a Prdx and P38 MAPK is sufficient to hyperactivate the kinase in yeast and human cells by a mechanism that does not require the H2O2-sensing cysteine of the Prdx. We demonstrate that a P38-Prdx fusion protein compensates for loss of the yeast scaffold protein Mcs4 and MAP3K activity, driving yeast into mitosis. Based on our findings, we propose that the H2O2-induced formation of Prdx-MAPK disulfide complexes provides an alternative scaffold and signaling platform for MAPKK-MAPK signaling. The demonstration that formation of a complex with a Prdx is sufficient to modify the activity of a kinase has broad implications for peroxide-based signal transduction in eukaryotes.
Assuntos
Peroxirredoxinas , Proteínas Quinases p38 Ativadas por Mitógeno , Humanos , Cisteína/metabolismo , Dissulfetos , Peróxido de Hidrogênio/farmacologia , Peróxido de Hidrogênio/metabolismo , Oxirredução , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Peroxirredoxinas/genética , Peroxirredoxinas/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismoRESUMO
Reactive oxygen species (ROS) are physiological mediators of cellular signaling and play potentially damaging roles in human diseases. In this study, we found that the catalytic activity of the Ser/Thr kinase Aurora A was inhibited by the oxidation of a conserved cysteine residue (Cys290) that lies adjacent to Thr288, a critical phosphorylation site in the activation segment. Cys is present at the equivalent position in ~100 human Ser/Thr kinases, a residue that we found was important not only for the activity of human Aurora A but also for that of fission yeast MAPK-activated kinase (Srk1) and PKA (Pka1). Moreover, the presence of this conserved Cys predicted biochemical redox sensitivity among a cohort of human CAMK, AGC, and AGC-like kinases. Thus, we predict that redox modulation of the conserved Cys290 of Aurora A may be an underappreciated regulatory mechanism that is widespread in eukaryotic Ser/Thr kinases. Given the key biological roles of these enzymes, these findings have implications for understanding physiological and pathological responses to ROS and highlight the importance of protein kinase regulation through multivalent modification of the activation segment.
Assuntos
Aurora Quinase A/química , Aurora Quinase A/metabolismo , Evolução Molecular , Animais , Aurora Quinase A/genética , Cisteína/química , Cisteína/genética , Cisteína/metabolismo , Células HeLa , Humanos , Camundongos , OxirreduçãoRESUMO
Endogenous and exogenous stresses elicit transcriptional responses that limit damage and promote cell/organismal survival. Like its mammalian counterparts, hepatocyte nuclear factor 4 (HNF4) and peroxisome proliferator-activated receptor α (PPARα), Caenorhabditis elegans NHR-49 is a well-established regulator of lipid metabolism. Here, we reveal that NHR-49 is essential to activate a transcriptional response common to organic peroxide and fasting, which includes the pro-longevity gene fmo-2/flavin-containing monooxygenase. These NHR-49-dependent, stress-responsive genes are also upregulated in long-lived glp-1/notch receptor mutants, with two of them making critical contributions to the oxidative stress resistance of wild-type and long-lived glp-1 mutants worms. Similar to its role in lipid metabolism, NHR-49 requires the mediator subunit mdt-15 to promote stress-induced gene expression. However, NHR-49 acts independently from the transcription factor hlh-30/TFEB that also promotes fmo-2 expression. We show that activation of the p38 MAPK, PMK-1, which is important for adaptation to a variety of stresses, is also important for peroxide-induced expression of a subset of NHR-49-dependent genes that includes fmo-2. However, organic peroxide increases NHR-49 protein levels, by a posttranscriptional mechanism that does not require PMK-1 activation. Together, these findings establish a new role for the HNF4/PPARα-related NHR-49 as a stress-activated regulator of cytoprotective gene expression.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Jejum/metabolismo , Ácidos Graxos/metabolismo , Fator 4 Nuclear de Hepatócito/genética , Metabolismo dos Lipídeos/imunologia , Receptores Citoplasmáticos e Nucleares/genética , Animais , Proteínas de Caenorhabditis elegans/genética , Estresse Oxidativo , Transdução de SinaisRESUMO
Cellular homoeostatic pathways such as macroautophagy (hereinafter autophagy) are regulated by basic mechanisms that are conserved throughout the eukaryotic kingdom. However, it remains poorly understood how these mechanisms further evolved in higher organisms. Here we describe a modification in the autophagy pathway in vertebrates, which promotes its activity in response to oxidative stress. We have identified two oxidation-sensitive cysteine residues in a prototypic autophagy receptor SQSTM1/p62, which allow activation of pro-survival autophagy in stress conditions. The Drosophila p62 homologue, Ref(2)P, lacks these oxidation-sensitive cysteine residues and their introduction into the protein increases protein turnover and stress resistance of flies, whereas perturbation of p62 oxidation in humans may result in age-related pathology. We propose that the redox-sensitivity of p62 may have evolved in vertebrates as a mechanism that allows activation of autophagy in response to oxidative stress to maintain cellular homoeostasis and increase cell survival.
Assuntos
Autofagia , Proteostase , Espécies Reativas de Oxigênio/metabolismo , Proteína Sequestossoma-1/metabolismo , Sequência de Aminoácidos , Animais , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Células HEK293 , Células HeLa , Humanos , Peróxido de Hidrogênio/farmacologia , Camundongos Knockout , Oxidantes/farmacologia , Oxirredução , Homologia de Sequência de Aminoácidos , Proteína Sequestossoma-1/genéticaRESUMO
SIGNIFICANCE: In 2003, structural studies revealed that eukaryotic 2-Cys peroxiredoxins (Prx) have evolved to be sensitive to inactivation of their thioredoxin peroxidase activity by hyperoxidation (sulfinylation) of their peroxide-reacting catalytic cysteine. This was accompanied by the unexpected discovery, that the sulfinylation of this cysteine was reversible in vivo and the identification of a new enzyme, sulfiredoxin, that had apparently co-evolved specifically to reduce hyperoxidized 2-Cys Prx, restoring their peroxidase activity. Together, these findings have provided the impetus for multiple studies investigating the purpose of this reversible, Prx hyperoxidation. Recent Advances: It has been suggested that inhibition of the thioredoxin peroxidase activity by hyperoxidation can both promote and inhibit peroxide signal transduction, depending on the context. Prx hyperoxidation has also been proposed to protect cells against reactive oxygen species (ROS)-induced damage, by preserving reduced thioredoxin and/or by increasing non-peroxidase chaperone or signaling activities of Prx. CRITICAL ISSUES: Here, we will review the evidence in support of each of these proposed functions, in view of the in vivo contexts in which Prx hyperoxidation occurs, and the role of sulfiredoxin. Thus, we will attempt to explain the basis for seemingly contradictory roles for Prx hyperoxidation in redox signaling. FUTURE DIRECTIONS: We provide a rationale, based on modeling and experimental studies, for why Prx hyperoxidation should be considered a suitable, early biomarker for damaging levels of ROS. We discuss the implications that this has for the role of Prx in aging and the detection of hyperoxidized Prx as a conserved feature of circadian rhythms. Antioxid. Redox Signal. 28, 574-590.
Assuntos
Catálise , Peróxido de Hidrogênio/metabolismo , Chaperonas Moleculares/metabolismo , Peroxirredoxinas/metabolismo , Cisteína/química , Cisteína/metabolismo , Chaperonas Moleculares/química , Oxirredução , Peróxidos/metabolismo , Peroxirredoxinas/química , Espécies Reativas de Oxigênio/metabolismo , Transdução de SinaisRESUMO
ROS (reactive oxygen species) are potentially damaging by-products of aerobic metabolism which, unchecked, can have detrimental effects on cell function. However, it is now widely accepted that, at physiological levels, certain ROS play important roles in cell signaling, acting as second messengers to regulate cell choices that contribute to the development, adaptation and survival of plants and animals. Despite important recent advances in the biochemical tools available to study redox-signaling, the molecular mechanisms underlying most of these responses remain poorly understood, particularly in multicellular organisms. As we will review here, C. elegans has emerged as a powerful animal model to elucidate these and other aspects of redox biology.
Assuntos
Envelhecimento/genética , Caenorhabditis elegans/metabolismo , Longevidade/genética , Espécies Reativas de Oxigênio/metabolismo , Animais , Caenorhabditis elegans/genética , Modelos AnimaisRESUMO
During interactions with its mammalian host, the pathogenic yeast Candida albicans is exposed to a range of stresses such as superoxide radicals and cationic fluxes. Unexpectedly, a nonbiased screen of transcription factor deletion mutants revealed that the phosphate-responsive transcription factor Pho4 is vital for the resistance of C. albicans to these diverse stresses. RNA-Seq analysis indicated that Pho4 does not induce stress-protective genes directly. Instead, we show that loss of Pho4 affects metal cation toxicity, accumulation, and bioavailability. We demonstrate that pho4Δ cells are sensitive to metal and nonmetal cations and that Pho4-mediated polyphosphate synthesis mediates manganese resistance. Significantly, we show that Pho4 is important for mediating copper bioavailability to support the activity of the copper/zinc superoxide dismutase Sod1 and that loss of Sod1 activity contributes to the superoxide sensitivity of pho4Δ cells. Consistent with the key role of fungal stress responses in countering host phagocytic defenses, we also report that C. albicans pho4Δ cells are acutely sensitive to macrophage-mediated killing and display attenuated virulence in animal infection models. The novel connections between phosphate metabolism, metal homeostasis, and superoxide stress resistance presented in this study highlight the importance of metabolic adaptation in promoting C. albicans survival in the host.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição/metabolismo , Adaptação Fisiológica/fisiologia , Candida albicans/genética , Candida albicans/metabolismo , Cobre/metabolismo , Proteínas Fúngicas/metabolismo , Homeostase , Metais , Estresse Oxidativo/fisiologia , Fosfatos , Proteínas de Saccharomyces cerevisiae , Análise de Sequência de RNA , Estresse Fisiológico , Superóxido Dismutase/genética , Superóxido Dismutase-1/metabolismo , Virulência/fisiologiaRESUMO
Peroxiredoxins are highly conserved and abundant peroxidases. Although the thioredoxin peroxidase activity of peroxiredoxin (Prx) is important to maintain low levels of endogenous hydrogen peroxide, Prx have also been shown to promote hydrogen peroxide-mediated signalling. Mitogen activated protein kinase (MAPK) signalling pathways mediate cellular responses to a variety of stimuli, including reactive oxygen species (ROS). Here we review the evidence that Prx can act as both sensors and barriers to the activation of MAPK and discuss the underlying mechanisms involved, focusing in particular on the relationship with thioredoxin.
Assuntos
Peróxido de Hidrogênio/metabolismo , Sistema de Sinalização das MAP Quinases , Peroxirredoxinas/metabolismo , Animais , Humanos , Mamíferos/metabolismo , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Leveduras/metabolismoRESUMO
Peroxiredoxins (Prx) are abundant thiol peroxidases with a conserved anti-ageing role. In contrast to most animals, the nematode worm, Caenorhabditis elegans, encodes a single cytosolic 2-Cys Prx, PRDX-2, rendering it an excellent model for examining how peroxiredoxins affect animal physiology and ageing. Our previous work revealed that, although PRDX-2 protects against the toxicity of peroxides, enigmatically, prdx-2-mutant animals are hyper-resistant to other forms of oxidative stress. Here, we have investigated the basis for this increased resistance. Mammalian FOXO and Nrf2 transcription factors directly promote the expression of a range of detoxification enzymes. We show that the FOXO orthologue, DAF-16, and the Nrf2 orthologue, SKN-1, are required for the increased stress resistance of prdx-2-mutant worms. Our data suggest that PRDX-2 is required for normal levels of insulin secretion and hence the inhibition of DAF-16 and SKN-1 by insulin/IGF-1-like signalling (IIS) under nutrient-rich conditions. Intriguingly, loss of PRDX-2 increases DAF-16 and SKN-1 activities sufficiently to increase arsenite resistance without initiating other IIS-inhibited processes. Together, these data suggest that loss of peroxiredoxin function may increase stress resistance by reducing insulin secretion, but that further changes in insulin signalling are required for the reprogramming of development and fat metabolism. In addition, we reveal that the temperature-dependent prolongevity function of PRDX-2 is required for the extended lifespan associated with several pathways, including further reductions in IIS.
Assuntos
Envelhecimento/genética , Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/genética , Insulina/metabolismo , Longevidade/genética , Peroxirredoxinas/genética , Envelhecimento/metabolismo , Animais , Arsenitos/farmacologia , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Regulação da Expressão Gênica , Secreção de Insulina , Fator de Crescimento Insulin-Like I/genética , Fator de Crescimento Insulin-Like I/metabolismo , Larva/efeitos dos fármacos , Larva/genética , Larva/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Estresse Oxidativo , Peroxirredoxinas/deficiência , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
BACKGROUND: Phase 2 detoxification enzymes provide a vital defence against reactive oxygen species, including xenobiotic metabolites, which cause the oxidative damage involved in drug toxicity and many diseases. Hence, there is great interest in understanding how levels of these enzymes are regulated. CnC transcription factors, such as mammalian Nrf2, drive the expression of phase 2 enzymes and are activated as an important conserved response to oxidative stress and xenobiotics. For instance, the Caenorhabditis elegans Nrf2 orthologue, SKN-1, is activated in response to arsenite by the stress-activated p38-related kinase, PMK-1, leading to increased expression of phase 2 enzymes. Here we have used a genome-wide screening approach to identify other C. elegans genes that are required for stress-induced increases in phase 2 detoxification gene expression. RESULTS: Taking advantage of the elevated phase 2 gene expression in a mutant lacking the peroxidase PRDX-2, we have identified many new genes that are required for stress-induced expression of gcs-1, a phase 2 enzyme critically required for glutathione synthesis. Significantly, these include genes previously implicated in resistance to ionizing radiation, longevity and responses to pathogenic infection. Many of these new candidate activators of gcs-1 are also required for the stress-induced intestinal expression of other phase 2 genes. However, intriguingly, our data suggest other factors may be specifically required for the stress-induced expression of gcs-1. Notably, we demonstrate that the candidate activator TIR-1(SARM1) and the MAPKKK NSY-1(Ask1) are required for the arsenite-induced activation of PMK-1. However, our data suggest that the majority of candidates participate in novel mechanisms to promote gcs-1 expression. For example, the E4 ubiquitin ligase UFD-2(UBE4B) is dispensable for PMK-1 activation but important for maintaining nuclear levels of SKN-1, the stress-induced expression of multiple SKN-1-target genes and oxidative stress resistance. CONCLUSIONS: Here we present the first functional, genome-wide analysis identifying genes that are required for activation of phase 2 detoxification genes in an animal. Our study identifies potential new regulators of Nrf2, reveals that additional mechanisms promote the stress-induced expression of specific phase 2 detoxification genes and provides new insight into the relationships between these universally important stress defences, oxidative stress resistance and aging.
Assuntos
Caenorhabditis elegans/genética , Regulação da Expressão Gênica/genética , Genoma Helmíntico , Estudo de Associação Genômica Ampla , Desintoxicação Metabólica Fase II/genética , Animais , Caenorhabditis elegans/metabolismo , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico , Xenobióticos/metabolismoRESUMO
As a more selectively reactive oxygen species, H2O2 (hydrogen peroxide) has been co-opted as a signalling molecule, but high levels can still lead to lethal amounts of cell damage. 2-Cys Prxs (peroxiredoxins) are ubiquitous thioredoxin peroxidases which utilize reversibly oxidized catalytic cysteine residues to reduce peroxides. As such, Prxs potentially make an important contribution to the repertoire of cell defences against oxidative damage. Although the abundance of eukaryotic 2-Cys Prxs suggests an important role in maintaining cell redox, the surprising sensitivity of their thioredoxin peroxidase activity to inactivation by H2O2 has raised questions as to their role as an oxidative stress defence. Indeed, work in model yeast has led the way in revealing that Prxs do much more than simply remove peroxides and have even uncovered circumstances where their thioredoxin peroxidase activity is detrimental. In the present paper, we focus on what we have learned from studies in the fission yeast Schizosaccharomyces pombe about the different roles of 2-Cys Prxs in responses to H2O2 and discuss the general implications of these findings for other systems.
Assuntos
Peróxido de Hidrogênio/farmacologia , Peroxirredoxinas/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/efeitos dos fármacos , Schizosaccharomyces/metabolismo , Estresse Oxidativo/efeitos dos fármacosRESUMO
Thioredoxins are a class of evolutionarily conserved proteins that have been demonstrated to play a key role in many cellular processes involving redox reactions. We report here the genetic and biochemical characterization of Caenorhabditis elegans TRX-3, the first metazoan thioredoxin with an intestine-specific expression pattern. By using green fluorescent protein reporters we have found that TRX-3 is expressed in both the cytoplasm and the nucleus of intestinal cells, with a prominent localization at the apical membrane. Although intestinal function, reproductive capacity, longevity, and resistance of trx-3 loss-of-function mutants to many stresses are indistinguishable from those of wild-type animals, we have observed a slight reduction in size and a minor reduction in the defecation cycle timing of trx-3 mutants. Interestingly, trx-3 is induced upon infection by Photorhabdus luminescens and Candida albicans, and TRX-3 overexpression provides a modest protection against these pathogens. Together, our data indicate that TRX-3 function in the intestine is dispensable for C. elegans development but may be important to fight specific bacterial and fungal infections.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/genética , Mucosa Intestinal/metabolismo , Tiorredoxinas/biossíntese , Sequência de Aminoácidos , Animais , Longevidade/genética , Especificidade de Órgãos , Oxirredução , Tiorredoxinas/genéticaRESUMO
H2O2 can cause oxidative damage associated with age-related diseases such as diabetes and cancer but is also used to initiate diverse responses, including increased antioxidant gene expression. Despite significant interest, H2O2-signaling mechanisms remain poorly understood. Here, we present a mechanism for the propagation of an H2O2 signal that is vital for the adaptation of the model yeast, Schizosaccharomyces pombe, to oxidative stress. Peroxiredoxins are abundant peroxidases with conserved antiaging and anticancer activities. Remarkably, we find that the only essential function for the thioredoxin peroxidase activity of the Prx Tpx1(hPrx1/2) in resistance to H2O2 is to inhibit a conserved thioredoxin family protein Txl1(hTxnl1/TRP32). Thioredoxins regulate many enzymes and signaling proteins. Thus, our discovery that a Prx amplifies an H2O2 signal by driving the oxidation of a thioredoxin-like protein has important implications, both for Prx function in oxidative stress resistance and for responses to H2O2.
Assuntos
Peróxido de Hidrogênio/farmacologia , Estresse Oxidativo , Peroxirredoxinas/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/metabolismo , Tiorredoxinas/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Peroxirredoxinas/genética , Schizosaccharomyces/efeitos dos fármacos , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe/genética , Tiorredoxinas/genéticaRESUMO
AIMS: As Candida albicans is the major fungal pathogen of humans, there is an urgent need to understand how this pathogen evades toxic reactive oxygen species (ROS) generated by the host immune system. A key regulator of antioxidant gene expression, and thus ROS resistance, in C. albicans is the AP-1-like transcription factor Cap1. Despite this, little is known regarding the intracellular signaling mechanisms that underlie the oxidation and activation of Cap1. Therefore, the aims of this study were; (i) to identify the regulatory proteins that govern Cap1 oxidation, and (ii) to investigate the importance of Cap1 oxidation in C. albicans pathogenesis. RESULTS: In response to hydrogen peroxide (H2O2), but not glutathione-depleting/modifying oxidants, Cap1 oxidation, nuclear accumulation, phosphorylation, and Cap1-dependent gene expression, is mediated by a glutathione peroxidase-like enzyme, which we name Gpx3, and an orthologue of the Saccharomyces cerevisiae Yap1 binding protein, Ybp1. In addition, Ybp1 also functions to stabilise Cap1 and this novel function is conserved in S. cerevisiae. C. albicans cells lacking Cap1, Ybp1, or Gpx3, are unable to filament and thus, escape from murine macrophages after phagocytosis, and also display defective virulence in the Galleria mellonella infection model. INNOVATION: Ybp1 is required to promote the stability of fungal AP-1-like transcription factors, and Ybp1 and Gpx3 mediated Cap1-dependent oxidative stress responses are essential for the effective killing of macrophages by C. albicans. CONCLUSION: Activation of Cap1, specifically by H2O2, is a prerequisite for the subsequent filamentation and escape of this fungal pathogen from the macrophage.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Candida albicans/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas Fúngicas/metabolismo , Peróxido de Hidrogênio/metabolismo , Macrófagos/metabolismo , Transdução de Sinais , Animais , Candida albicans/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Macrófagos/efeitos dos fármacos , Camundongos , Oxirredução , Transdução de Sinais/efeitos dos fármacosRESUMO
Eukaryotic 2-Cys peroxiredoxins (Prx) are abundant antioxidant enzymes whose thioredoxin peroxidase activity plays an important role in protecting against oxidative stress, aging, and cancer. Paradoxically, this thioredoxin peroxidase activity is highly sensitive to inactivation by peroxide-induced Prx hyperoxidation. However, any possible advantage in preventing Prx from removing peroxides under oxidative stress conditions has remained obscure. Here we demonstrate that, in cells treated with hydrogen peroxide, the Prx Tpx1 is a major substrate for thioredoxin in the fission yeast Schizosaccharomyces pombe and, as such, competitively inhibits thioredoxin-mediated reduction of other oxidized proteins. Consequently, we reveal that the hyperoxidation of Tpx1 is critical to allow thioredoxin to act on other substrates ensuring repair of oxidized proteins and cell survival following exposure to toxic levels of hydrogen peroxide. We conclude that the inactivation of the thioredoxin peroxidase activity of Prx is important to maintain thioredoxin activity and cell viability under oxidative stress conditions.
Assuntos
Peróxido de Hidrogênio/farmacologia , Peroxirredoxinas/antagonistas & inibidores , Proteínas de Schizosaccharomyces pombe/antagonistas & inibidores , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/enzimologia , Tiorredoxinas/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Dissulfetos/metabolismo , Técnicas de Inativação de Genes , Peróxido de Hidrogênio/metabolismo , Metionina/análogos & derivados , Metionina/metabolismo , Viabilidade Microbiana , Oxirredução , Estresse Oxidativo , Peroxirredoxinas/genética , Peroxirredoxinas/metabolismo , Schizosaccharomyces/fisiologia , Proteínas de Schizosaccharomyces pombe/genética , Tiorredoxinas/genéticaRESUMO
In this issue of Molecular Cell, Molin et al. (2011) reveal that caloric restriction alleviates PKA-dependent inhibition of sulfiredoxin translation, maintaining the thioredoxin peroxidase activity of a peroxiredoxin and increasing the hydrogen peroxide resistance and replicative life span of Saccharomyces cerevisiae.
RESUMO
MAPK are activated by and orchestrate responses to multiple, diverse stimuli. Although these responses involve the increased phosphorylation of substrate effector proteins, e.g. transcription factors, the mechanisms by which responses are tailored to particular stimuli are unclear. In the fission yeast Schizosaccharomyces pombe, the Sty1 MAPK is crucial for changes in gene expression that allow adaptation to many forms of environmental stress. Here, we have identified two cysteine residues in Sty1, Cys-153 and Cys-158, that are important for hydrogen peroxide-induced gene expression and oxidative stress resistance but not for other functions of Sty1. Many Sty1-dependent changes in gene expression are mediated by the Atf1 transcription factor. In response to stress, Sty1 increases Atf1 levels by (i) promoting increases in atf1 mRNA and by (ii) directly phosphorylating and stabilizing Atf1 protein. Although dispensable for phosphorylation and stabilization of Atf1 protein, we find that both Cys-153 and Cys-158 are required for increases in atf1 mRNA levels and Atf1-dependent gene expression in response to hydrogen peroxide but not osmotic stress. Indeed, our data indicate that oxidation of Sty1, by formation of a disulfide bond between Cys-153 and Cys-158, is important for maintaining atf1 mRNA stability at high concentrations of hydrogen peroxide. Together, these data reveal that redox regulation of cysteine thiols in Sty1 is involved in a stress-specific mechanism regulating transcriptional responses to oxidative stress. Intriguingly, the conservation of these cysteine residues in other MAPK raises the possibility that similar mechanisms may ensure appropriate responses to hydrogen peroxide in other eukaryotes.
Assuntos
Cisteína/metabolismo , Peróxido de Hidrogênio/metabolismo , Proteínas Quinases Ativadas por Mitógeno , Oxidantes/metabolismo , Estresse Oxidativo , Proteínas de Schizosaccharomyces pombe , Transcrição Gênica , Fator 1 Ativador da Transcrição/genética , Fator 1 Ativador da Transcrição/metabolismo , Animais , Regulação Fúngica da Expressão Gênica , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Oxirredução , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilação , Estabilidade de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo , Compostos de Sulfidrila/químicaRESUMO
Oxidative damage caused by reactive oxygen species (ROS) is implicated in many diseases and in aging. Removal of ROS by antioxidant enzymes plays an important part in limiting this damage. For instance, peroxiredoxins (Prx) are conserved, abundant, thioredoxin peroxidase enzymes that function as tumor suppressors. In addition to detoxifying peroxides, studies in single-cell systems have revealed that Prx act as chaperones and redox sensors. However, it is unknown in what manner the different activities of Prx influence stress resistance or longevity in the context of whole animals. Here, we reveal three distinct roles for the 2-Cys Prx, PRDX-2, in the stress resistance of the nematode worm Caenorhabditis elegans. (i) The thioredoxin peroxidase activity of PRDX-2 protects against hydrogen peroxide. (ii) Consistent with a chaperone activity for hyperoxidized PRDX-2, peroxide-induced oxidation of PRDX-2 increases resistance to heat stress. (iii) Unexpectedly, loss of PRDX-2 increases the resistance of C. elegans to some oxidative stress-causing agents, such as arsenite, apparently through a signaling mechanism that increases the levels of other antioxidants and phase II detoxification enzymes. Despite their increased resistance to some forms of oxidative stress, prdx-2 mutants are short-lived. Moreover, intestinal expression of PRDX-2 accounts for its role in detoxification of exogenous peroxide, but not its influence on either arsenite resistance or longevity, suggesting that PRDX-2 may promote longevity and protect against environmental stress through different mechanisms. Together the data reveal that in metazoans Prx act through multiple biochemical activities, and have tissue-specific functions in stress resistance and longevity.