Peroxiredoxins, gerontogenes linking aging to genome instability and cancer

RNA-seq transcriptome and pathway analysis of the medicinal mushroom Lignosus tigris (Polyporaceae) offer insights into its bioactive compounds with anticancer and antioxidant potential

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal mushrooms belonging to the Lignosus spp., colloquially known as Tiger Milk mushrooms (TMMs), are used as traditional medicine by communities across various regions of China and Southeast Asia to enhance immunity and to treat various diseases. At present, three Lignosus species have been identified in Malaysia: L. rhinocerus, L. tigris, and L. cameronensis. Similarities in their macroscopic morphologies and the nearly indistinguishable appearance of their sclerotia often lead to interchangeability between them. Hence, substantiation of their traditional applications via identification of their individual bioactive properties is imperative in ensuring that they are safe for consumption. L. tigris was first identified in 2013. Thus far, studies on L. tigris cultivar sclerotia (Ligno TG-K) have shown that it possesses significant antioxidant activities and has greater antiproliferative action against selected cancer cells in vitro compared to its sister species, L. rhinocerus TM02®. Our previous genomics study also revealed significant genetic dissimilarities between them. Further omics investigations on Ligno TG-K hold immense potential in facilitating the identification of its bioactive compounds and their associated bioactivities.

AIM OF STUDY

The overall aim of this study was to investigate the gene expression profile of Ligno TG-K via de novo RNA-seq and pathway analysis. We also aimed to identify highly expressed genes encoding compounds that contribute to its cytotoxic and antioxidant properties, as well as perform a comparative transcriptomics analysis between Ligno TG-K and its sister species, L. rhinocerus TM02®.

MATERIALS AND METHODS

Total RNA from fresh 3-month-old cultivated L. tigris sclerotia (Ligno TG-K) was extracted and analyzed via de novo RNA sequencing. Expressed genes were analyzed using InterPro and NCBI-Nr databases for domain identification and homology search. Functional categorization based on gene functions and pathways was performed using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Clusters of Orthologous Genes (COG) databases. Selected genes were subsequently subjected to phylogenetic analysis.

RESULTS

Our transcriptomics analysis of Ligno TG-K revealed that 68.06% of its genes are expressed in the sclerotium; 80.38% of these were coding transcripts. Our analysis identified highly expressed transcripts encoding proteins with prospective medicinal properties. These included serine proteases (FPKM = 7356.68), deoxyribonucleases (FPKM = 3777.98), lectins (FPKM = 3690.87), and fungal immunomodulatory proteins (FPKM = 2337.84), all of which have known associations with anticancer activities. Transcripts linked to proteins with antioxidant activities, such as superoxide dismutase (FPKM = 1161.69) and catalase (FPKM = 1905.83), were also highly expressed. Results of our sequence alignments revealed that these genes and their orthologs can be found in other mushrooms. They exhibit significant sequence similarities, suggesting possible parallels in their anticancer and antioxidant bioactivities.

CONCLUSION

This study is the first to provide a reference transcriptome profile of genes expressed in the sclerotia of L. tigris. The current study also presents distinct COG profiles of highly expressed genes in Ligno TG-K and L. rhinocerus TM02®, highlighting that any distinctions uncovered may be attributed to their interspecies variations and inherent characteristics that are unique to each species. Our findings suggest that Ligno TG-K contains bioactive compounds with prospective medicinal properties that warrant further investigations.

CLASSIFICATION

Systems biology and omics.

Glutathione and glutathione-dependent enzymes: From biochemistry to gerontology and successful aging

The tripeptide glutathione (GSH), namely γ-L-glutamyl-L-cysteinyl-glycine, is an ubiquitous low-molecular weight thiol nucleophile and reductant of utmost importance, representing the central redox agent of most aerobic organisms. GSH has vital functions involving also antioxidant protection, detoxification, redox homeostasis, cell signaling, iron metabolism/homeostasis, DNA synthesis, gene expression, cysteine/protein metabolism, and cell proliferation/differentiation or death including apoptosis and ferroptosis. Various functions of GSH are exerted in concert with GSH-dependent enzymes. Indeed, although GSH has direct scavenging antioxidant effects, its antioxidant function is substantially accomplished by glutathione peroxidase-catalyzed reactions with reductive removal of H2O2, organic peroxides such as lipid hydroperoxides, and peroxynitrite; to this antioxidant activity also contribute peroxiredoxins, enzymes further involved in redox signaling and chaperone activity. Moreover, the detoxifying function of GSH is basically exerted in conjunction with glutathione transferases, which have also antioxidant properties. GSH is synthesized in the cytosol by the ATP-dependent enzymes glutamate cysteine ligase (GCL), which catalyzes ligation of cysteine and glutamate forming γ-glutamylcysteine (γ-GC), and glutathione synthase, which adds glycine to γ-GC resulting in GSH formation; GCL is rate-limiting for GSH synthesis, as is the precursor amino acid cysteine, which may be supplemented as N-acetylcysteine (NAC), a therapeutically available compound. After its cell export, GSH is degraded extracellularly by the membrane-anchored ectoenzyme γ-glutamyl transferase, a process occurring, as GSH synthesis and export, in the γ-glutamyl cycle. GSH degradation occurs also intracellularly by the cytoplasmic enzymatic ChaC family of γ-glutamyl cyclotransferase. Synthesis and degradation of GSH, together with its export, translocation to cell organelles, utilization for multiple essential functions, and regeneration from glutathione disulfide by glutathione reductase, are relevant to GSH homeostasis and metabolism. Notably, GSH levels decline during aging, an alteration generally related to impaired GSH biosynthesis and leading to cell dysfunction. However, there is evidence of enhanced GSH levels in elderly subjects with excellent physical and mental health status, suggesting that heightened GSH may be a marker and even a causative factor of increased healthspan and lifespan. Such aspects, and much more including GSH-boosting substances administrable to humans, are considered in this state-of-the-art review, which deals with GSH and GSH-dependent enzymes from biochemistry to gerontology, focusing attention also on lifespan/healthspan extension and successful aging; the significance of GSH levels in aging is considered also in relation to therapeutic possibilities and supplementation strategies, based on the use of various compounds including NAC-glycine, aimed at increasing GSH and related defenses to improve health status and counteract aging processes in humans.

A peroxiredoxin-P38 MAPK scaffold increases MAPK activity by MAP3K-independent mechanisms

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.

Extensive accumulation of misfolded protein aggregates during natural aging and senescence

Accumulation of misfolded protein aggregates is a hallmark event in many age-related protein misfolding disorders, including some of the most prevalent and insidious neurodegenerative diseases. Misfolded protein aggregates produce progressive cell damage, organ dysfunction, and clinical changes, which are common also in natural aging. Thus, we hypothesized that aging is associated to the widespread and progressive misfolding and aggregation of many proteins in various tissues. In this study, we analyzed whether proteins misfold, aggregate, and accumulate during normal aging in three different biological systems, namely senescent cells, Caenorhabditis elegans, and mouse tissues collected at different times from youth to old age. Our results show a significant accumulation of misfolded protein aggregates in aged samples as compared to young materials. Indeed, aged samples have between 1.3 and 2.5-fold (depending on the biological system) higher amount of insoluble proteins than young samples. These insoluble proteins exhibit the typical characteristics of disease-associated aggregates, including insolubility in detergents, protease resistance, and staining with amyloid-binding dye as well as accumulation in aggresomes. We identified the main proteins accumulating in the aging brain using proteomic studies. These results show that the aged brain contain large amounts of misfolded and likely non-functional species of many proteins, whose soluble versions participate in cellular pathways that play fundamental roles in preserving basic functions, such as protein quality control, synapsis, and metabolism. Our findings reveal a putative role for protein misfolding and aggregation in aging.

Metabolomics of blood reveals age-dependent pathways in Parkinson’s Disease

Background

Parkinson’s Disease (PD) is the second most frequent degenerative disorder, the risk of which increases with age. A preclinical PD diagnostic test does not exist. We identify PD blood metabolites and metabolic pathways significantly correlated with age to develop personalized age-dependent PD blood biomarkers.

Results

We found 33 metabolites producing a receiver operating characteristic (ROC) area under the curve (AUC) value of 97%. PCA revealed that they belong to three pathways with distinct age-dependent behavior: glycine, threonine and serine metabolism correlates with age only in PD patients; unsaturated fatty acids biosynthesis correlates with age only in a healthy control group; and, finally, tryptophan metabolism characterizes PD but does not correlate with age.

Conclusions

The targeted analysis of the blood metabolome proposed in this paper allowed to find specific age-related metabolites and metabolic pathways. The model offers a promising set of blood biomarkers for a personalized age-dependent approach to the early PD diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00831-5.

Cellular redox imbalance on the crossroad between mitochondrial dysfunction, senescence, and proliferation

Recent studies demonstrate that redox imbalance of NAD⁺/NADH and NADP⁺/NADPH pairs due to impaired respiration may trigger two “hidden” metabolic pathways on the crossroad between mitochondrial dysfunction, senescence, and proliferation: “β-oxidation shuttle” and “hydride transfer complex (HTC) cycle”. The “β-oxidation shuttle” induces NAD⁺/NADH redox imbalance in mitochondria, while HTC cycle maintains the redox balance of cytosolic NAD⁺/NADH, increasing the redox disbalance of NADP⁺/NADPH. Senescence appears to depend on high cytoplasmic NADH but low NADPH, while proliferation depends on high cytoplasmic NAD⁺ and NADPH that are under mitochondrial control. Thus, activating or deactivating the HTC cycle can be crucial to cell fate – senescence or proliferation. These pathways are a source of enormous cataplerosis. They support the production of large amounts of NADPH and intermediates for lipid synthesis and membrane biogenesis, as well as for DNA synthesis.

Peroxiredoxin-1 Tyr194 phosphorylation regulates LOX-dependent extracellular matrix remodelling in breast cancer

BACKGROUND

Peroxiredoxin 1 (PRDX1) belongs to an abundant family of peroxidases whose role in cancer is still unresolved. While mouse knockout studies demonstrate a tumour suppressive role for PRDX1, in cancer cell xenografts, results denote PRDX1 as a drug target. Probably, this phenotypic discrepancy stems from distinct roles of PRDX1 in certain cell types or stages of tumour progression.

METHODS

We demonstrate an important cell-autonomous function for PRDX1 utilising a syngeneic mouse model (BALB/c) and mammary fibroblasts (MFs) obtained from it.

RESULTS

Loss of PRDX1 in vivo promotes collagen remodelling known to promote breast cancer progression. PRDX1 inactivation in MFs occurs via SRC-induced phosphorylation of PRDX1 TYR194 and not through the expected direct oxidation of CYS52 in PRDX1 by ROS. TYR194-phosphorylated PRDX1 fails to bind to lysyl oxidases (LOX) and leads to the accumulation of extracellular LOX proteins which supports enhanced collagen remodelling associated with breast cancer progression.

CONCLUSIONS

This study reveals a cell type-specific tumour suppressive role for PRDX1 that is supported by survival analyses, depending on PRDX1 protein levels in breast cancer cohorts.

PRDX1 is essential for the viability and maintenance of reactive oxygen species in chicken DT40

Background

Peroxiredoxin 1 (PRDX1) is a member of a ubiquitous family of thiol peroxidases that catalyze the reduction of peroxides, including hydrogen peroxide. It functions as an antioxidant enzyme, similar to catalase and glutathione peroxidase. PRDX1 was recently shown act as a sensor of reactive oxygen species (ROS) and play a role in ROS-dependent intracellular signaling pathways. To investigate its physiological functions, PRDX1 was conditionally disrupted in chicken DT40 cells in the present study.

Results

The depletion of PRDX1 resulted in cell death with increased levels of intracellular ROS. PRDX1-depleted cells did not show the accumulation of chromosomal breaks or sister chromatid exchange (SCE). These results suggest that cell death in PRDX1-depleted cells was not due to DNA damage. 2-Mercaptoethanol protected against cell death in PRDX1-depleted cells and also suppressed elevations in ROS.

Conclusions

PRDX1 is essential in chicken DT40 cells and plays an important role in maintaining intracellular ROS homeostasis (or in the fine-tuning of cellular ROS levels). Cells deficient in PRDX1 may be used as an endogenously deregulated ROS model to elucidate the physiological roles of ROS in maintaining proper cell growth.

Cellular senescence or stemness: hypoxia flips the coin

Cellular senescence is a complex physiological state whose main feature is proliferative arrest. Cellular senescence can be considered the reverse of cell immortalization and continuous tumor growth. However, cellular senescence has many physiological functions beyond being a putative tumor suppressive trait. It remains unknown whether low levels of oxygen or hypoxia, which is a feature of every tissue in the organism, modulate cellular senescence, altering its capacity to suppress the limitation of proliferation. It has been observed that the lifespan of mammalian primary cells is increased under low oxygen conditions. Additionally, hypoxia promotes self-renewal and pluripotency maintenance in adult and embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and cancer stem cells (CSCs). In this study, we discuss the role of hypoxia facilitating senescence bypass during malignant transformation and acquisition of stemness properties, which all contribute to tumor development and cancer disease aggressiveness.

Impact of Hydrogen Peroxide on Protein Synthesis in Yeast

Cells must be able to respond and adapt to different stress conditions to maintain normal function. A common response to stress is the global inhibition of protein synthesis. Protein synthesis is an expensive process consuming much of the cell's energy. Consequently, it must be tightly regulated to conserve resources. One of these stress conditions is oxidative stress, resulting from the accumulation of reactive oxygen species (ROS) mainly produced by the mitochondria but also by other intracellular sources. Cells utilize a variety of antioxidant systems to protect against ROS, directing signaling and adaptation responses at lower levels and/or detoxification as levels increase to preclude the accumulation of damage. In this review, we focus on the role of hydrogen peroxide, H₂O₂, as a signaling molecule regulating protein synthesis at different levels, including transcription and various parts of the translation process, e.g., initiation, elongation, termination and ribosome recycling.

Peroxiredoxins couple metabolism and cell division in an ultradian cycle

Redox cycles have been reported in ultradian, circadian and cell cycle-synchronized systems. Redox cycles persist in the absence of transcription and cyclin-CDK activity, indicating that cells harbor multiple coupled oscillators. Nonetheless, the causal relationships and molecular mechanisms by which redox cycles are embedded within ultradian, circadian or cell division cycles remain largely elusive. Yeast harbor an ultradian oscillator, the yeast metabolic cycle (YMC), which comprises metabolic/redox cycles, transcriptional cycles and synchronized cell division. Here, we reveal the existence of robust cycling of H₂O₂ and peroxiredoxin oxidation during the YMC and show that peroxiredoxin inactivation disrupts metabolic cycling and abolishes coupling with cell division. We find that thiol-disulfide oxidants and reductants predictably modulate the switching between different YMC metabolic states, which in turn predictably perturbs cell cycle entry and exit. We propose that oscillatory H₂O₂-dependent protein thiol oxidation is a key regulator of metabolic cycling and its coordination with cell division.

Coenzyme Q redox signalling and longevity

Mitochondria are the powerhouses of the cell. They produce a significant amount of the energy we need to grow, survive and reproduce. The same system that generates energy in the form of ATP also produces Reactive Oxygen Species (ROS). Mitochondrial Reactive Oxygen Species (mtROS) were considered for many years toxic by-products of metabolism, responsible for ageing and many degenerative diseases. Today, we know that mtROS are essential redox messengers required to determine cell fate and maintain cellular homeostasis. Most mtROS are produced by respiratory complex I (CI) and complex III (CIII). How and when CI and CIII produce ROS is determined by the redox state of the Coenzyme Q (CoQ) pool and the proton motive force (pmf) generated during respiration. During ageing, there is an accumulation of defective mitochondria that generate high levels of mtROS. This causes oxidative stress and disrupts redox signalling. Here, we review how mtROS are generated in young and old mitochondria and how CI and CIII derived ROS control physiological and pathological processes. Finally, we discuss why damaged mitochondria amass during ageing as well as methods to preserve mitochondrial redox signalling with age.

Molecular profiling and functional delineation of peroxiredoxin 3 (HaPrx3) from the big-belly seahorses (Hippocampus abdominalis) and understanding their immunological responses

Peroxiredoxins (Prxs) are ubiquitously expressed antioxidant proteins that can protect aerobic organisms from oxidative stress. Here, we characterized the HaPrx3 homolog at the molecular level from big-belly seahorse (Hippocampus abdominalis) and analyzed its functional activities. The coding sequence of HaPrx3 consists of 726 bp, which encodes 241 amino acids. The predicted molecular weight and theoretical isoelectric point (pI) of HaPrx3 was 26.20 kDa and 7.04, respectively. Multiple sequence alignments revealed that the arrangements of domains, catalytic triads, dimers, and decamer interfaces of HaPrx3 were conserved among Prx sequences of other organisms. According to the phylogenetic analysis, HaPrx3 is clustered with the teleost Prx3 subclade. The highest transcript level of HaPrx3 was detected in the ovary tissue among fourteen healthy fish tissues. The mRNA levels of HaPrx3 in blood and liver tissues were significantly (P < 0.05) upregulated in response to lipopolysaccharide (LPS), polyinosinic-polycytidylic (poly I:C), Edwardsiella tarda, and Streptococcus iniae, suggesting its involvement in immune responses. Under functional properties, insulin disulfide reduction assay confirmed the oxidoreductase activity of recombinant HaPrx3. A cell viability assay and Hoechst staining indicated cell survival ability and reduction of apoptotic activity, respectively. Moreover, a peroxidase activity assay verified peroxidase activity, while a metal-catalyzed oxidation (MCO) assay indicated the DNA protection ability of HaPrx3. Collectively, it is concluded that HaPrx3 may play a significant role in oxidative stress and immune responses against pathogenic infections in big-belly seahorses.

Protein kinase A controls yeast growth in visible light

Background

A wide variety of photosynthetic and non-photosynthetic species sense and respond to light, having developed protective mechanisms to adapt to damaging effects on DNA and proteins. While the biology of UV light-induced damage has been well studied, cellular responses to stress from visible light (400–700 nm) remain poorly understood despite being a regular part of the life cycle of many organisms. Here, we developed a high-throughput method for measuring growth under visible light stress and used it to screen for light sensitivity in the yeast gene deletion collection.

Results

We found genes involved in HOG pathway signaling, RNA polymerase II transcription, translation, diphthamide modifications of the translational elongation factor eEF2, and the oxidative stress response to be required for light resistance. Reduced nuclear localization of the transcription factor Msn2 and lower glycogen accumulation indicated higher protein kinase A (cAMP-dependent protein kinase, PKA) activity in many light-sensitive gene deletion strains. We therefore used an ectopic fluorescent PKA reporter and mutants with constitutively altered PKA activity to show that repression of PKA is essential for resistance to visible light.

Conclusion

We conclude that yeast photobiology is multifaceted and that protein kinase A plays a key role in the ability of cells to grow upon visible light exposure. We propose that visible light impacts on the biology and evolution of many non-photosynthetic organisms and have practical implications for how organisms are studied in the laboratory, with or without illumination.

Antioxidant functions of DHHC3 suppress anti-cancer drug activities

Ablation of protein acyltransferase DHHC3 selectively enhanced the anti-cancer cell activities of several chemotherapeutic agents, but not kinase inhibitors. To understand why this occurs, we used comparative mass spectrometry-based palmitoyl-proteomic analysis of breast and prostate cancer cell lines, ± DHHC3 ablation, to obtain the first comprehensive lists of candidate protein substrates palmitoylated by DHHC3. Putative substrates included 22-28 antioxidant/redox-regulatory proteins, thus predicting that DHHC3 should have antioxidant functions. Consistent with this, DHHC3 ablation elevated oxidative stress. Furthermore, DHHC3 ablation, together with chemotherapeutic drug treatment, (a) elevated oxidative stress, with a greater than additive effect, and (b) enhanced the anti-growth effects of the chemotherapeutic agents. These results suggest that DHHC3 ablation enhances chemotherapeutic drug potency by disabling the antioxidant protections that contribute to drug resistance. Affirming this concept, DHHC3 ablation synergized with another anti-cancer drug, PARP inhibitor PJ-34, to decrease cell proliferation and increase oxidative stress. Hence, DHHC3 targeting can be a useful strategy for selectively enhancing potency of oxidative stress-inducing anti-cancer drugs. Also, comprehensive identification of DHHC3 substrates provides insight into other DHHC3 functions, relevant to in vivo tumor growth modulation.

Redox Post-translational Modifications of Protein Thiols in Brain Aging and Neurodegenerative Conditions-Focus on S-Nitrosation

Reactive oxygen species and reactive nitrogen species (RONS) are by-products of aerobic metabolism. RONS trigger a signaling cascade that can be transduced through oxidation-reduction (redox)-based post-translational modifications (redox PTMs) of protein thiols. This redox signaling is essential for normal cellular physiology and coordinately regulates the function of redox-sensitive proteins. It plays a particularly important role in the brain, which is a major producer of RONS. Aberrant redox PTMs of protein thiols can impair protein function and are associated with several diseases. This mini review article aims to evaluate the role of redox PTMs of protein thiols, in particular S-nitrosation, in brain aging, and in neurodegenerative diseases. It also discusses the potential of using redox-based therapeutic approaches for neurodegenerative conditions.

A scan for genes associated with cancer mortality and longevity in pedigree dog breeds

Selective breeding of the domestic dog (Canis lupus familiaris) rigidly retains desirable features, and could inadvertently fix disease-causing variants within a breed. We combine phenotypic data from > 72,000 dogs with a large genotypic dataset to search for genes associated with cancer mortality and longevity in pedigree dog breeds. We validated previous findings that breeds with higher average body weight have higher cancer mortality rates and lower life expectancy. We identified a significant positive correlation between life span and cancer mortality residuals corrected for body weight, implying that long-lived breeds die more frequently from cancer compared to short-lived breeds. We replicated a number of known genetic associations with body weight (IGF1, GHR, CD36, SMAD2 and IGF2BP2). Subsequently, we identified five genetic variants in known cancer-related genes (located within SIPA1, ADCY7 and ARNT2) that could be associated with cancer mortality residuals corrected for confounding factors. One putative genetic variant was marginally significantly associated with longevity residuals that had been corrected for the effects of body weight; this genetic variant is located within PRDX1, a peroxiredoxin that belongs to an emerging class of pro-longevity associated genes. This research should be considered as an exploratory analysis to uncover associations between genes and longevity/cancer mortality.

Peroxiredoxin promotes longevity and H2O2-resistance in yeast through redox-modulation of protein kinase A

Peroxiredoxins are H2O2 scavenging enzymes that also carry out H2O2 signaling and chaperone functions. In yeast, the major cytosolic peroxiredoxin, Tsa1 is required for both promoting resistance to H2O2 and extending lifespan upon caloric restriction. We show here that Tsa1 effects both these functions not by scavenging H2O2, but by repressing the nutrient signaling Ras-cAMP-PKA pathway at the level of the protein kinase A (PKA) enzyme. Tsa1 stimulates sulfenylation of cysteines in the PKA catalytic subunit by H2O2 and a significant proportion of the catalytic subunits are glutathionylated on two cysteine residues. Redox modification of the conserved Cys243 inhibits the phosphorylation of a conserved Thr241 in the kinase activation loop and enzyme activity, and preventing Thr241 phosphorylation can overcome the H2O2 sensitivity of Tsa1-deficient cells. Results support a model of aging where nutrient signaling pathways constitute hubs integrating information from multiple aging-related conduits, including a peroxiredoxin-dependent response to H2O2.

The Third International Symposium on Fungal Stress - ISFUS

Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in São José dos Campos, São Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.

The role of the redox/miR-6855-3p/PRDX5A axis in reversing SLUG-mediated BRCA2 silencing in breast cancer cells

BACKGROUND

We have previously shown that the zinc finger transcription repressor SNAI2 (SLUG) represses tumor suppressor BRCA2-expression in non-dividing cells by binding to the E2-box upstream of the transcription start site. However, it is unclear how proliferating breast cancer (BC) cells that has higher oxidation state, overcome this repression. In this study, we provide insight into the mechanism of de-silencing of BRCA2 gene expression by PRDX5A, which is the longest member of the peroxiredoxin5 family, in proliferating breast cancer cells.

METHODS

We used cell synchronization and DNA affinity pulldown to analyze PRDX5A binding to the BRCA2 silencer. We used oxidative stress and microRNA (miRNA) treatments to study nuclear localization of PRDX5A and its impact on BRCA2-expression. We validated our findings using mutational, reporter assay, and immunofluorescence analyses.

RESULTS

Under oxidative stress, proliferating BC cells express PRDX5 isoform A (PRDX5A). In the nucleus, PRDX5A binds to the BRCA2 silencer near the E2-box, displacing SLUG and enhancing BRCA2-expression. Nuclear PRDX5A is translated from the second AUG codon in frame to the first AUG codon in the PRDX5A transcript that retains all exons. Mutation of the first AUG increases nuclear localization of PRDX5A in MDA-MB-231 cells, but mutation of the second AUG decreases it. Increased mitronic hsa-miRNA-6855-3p levels under oxidative stress renders translation from the second AUG preferable. Mutational analysis using reporter assay uncovered a miR-6855-3p binding site between the first and second AUG codon in the PRDX5A transcript. miR-6855-3p mimic increases accumulation of nuclear PRDX5A and inhibits reporter gene translation.

CONCLUSION

Oxidative stress increases miR-6855-3p expression and binding to the inter-AUG sequence of the PRDX5A transcript, promoting translation of nuclear PRDX5A. Nuclear PRDX5A relieves SLUG-mediated BRCA2 silencing, resulting in increased BRCA2-expression.

Bisphenol AF compromises blood-testis barrier integrity and sperm quality in mice

The profound influence of environmental chemicals on human health including inducing life-threatening gene mutation has been publicly recognized. Being a substitute for the extensively used endocrine-disrupting chemical BPA, Bisphenol AF (BPAF) has been known as teratogen with developmental toxicities and therefore potentially putting human into the risk of biological hazards. Herein, we deciphered the detrimental effects of BPAF on spermatogenesis and spermiotiliosis in sexual maturity of mice exposing to BPAF (5, 20, 50 mg/kg/d) for consecutive 28 days. BPAF exposure significantly compromises blood-testis barrier integrity and sperm quantity and quality in a dose-dependent manner. Sperms from BPAF exposure mice are featured by severe DNA damage, altered SUMOylation and ubiquitination dynamics and interfered epigenetic inheritance with hypermethylation of H3K27me3 presumably due to the aggregation of cellular reactive oxygen species (ROS). Furthermore, BPAF treatment (50 μM for 24 h) compromises cytoskeleton architecture and tight junction permeability in primary cultured Sertoli cells evidenced by dysfunction of actin regulatory proteins (e.g. Arp3 and Palladin) via activation of ERK signaling, thereby perturbing the privilege microenvironment created by Sertoli cells for spermatogenesis. Overall, our study determines BPAF is deleterious for male fertility, leading to a better appreciation of its toxicological features in our life.

Molecular characterization and functional activity of Prx1 in grass carp (Ctenopharyngodon idella)

Peroxiredoxin (Prx) family are known as an important antioxidant enzyme as the first line of defense against oxidative damage, and also involved in immune responses following viral and bacterial infection. Here, a full-length Prx1 cDNA sequence (CiPrx1) was cloned from grass carp (Ctenopharyngodon idella), which was 1029 bp, including a 5'-terminal untranslated region (UTR) of 121 bp, a 3'-UTR of 272 bp, an open reading frame of 600 bp encoding 199 amino acids with molecular weight of 22.21 kDa and isoelectric point of 6.30. CiPrx1 shares 80.8-99% protein sequence similarity with Prx1 of other fishes. The conserved peroxidase catalytic center "FYPLDFTFVCPTEI" and "GEVCPA" were observed in the sequence of CiPrx1; this indicated that it was a member of 2-Cys Prx. Subcellular localization of CiPrx1 was only strongly distributed in the cytoplasm. Quantitative real-time PCR (RT-qPCR) assays revealed that CiPrx1 mRNA was ubiquitously detected in all tested tissues, and the expression was comparatively high in liver, gill and spleen. Further, the expression of CiPrx1 can be induced by grass carp reovirus (GCRV), lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (Poly I:C) infection in the different tissues. Moreover, the recombinant CiPrx1 (rCiPrx1) protein was found a potential antioxidant enzyme, that could inhibit DNA damage from oxidants. Altogether, our results imply that CiPrx1 is associated with defending against virus and bacteria pathogens and oxidants in grass carp.

Role of Cytosolic 2-Cys Prx1 and Prx2 in Redox Signaling

Peroxiredoxins (Prxs), a family of peroxidases, are reactive oxygen species scavengers that hydrolyze H₂O₂ through catalytic cysteine. Mammalian Prxs comprise six isoforms (typical 2-Cys Prxs; Prx1–4, atypical 2-Cys Prx; Prx5, and 1-Cys Prx; Prx6) that are distributed over various cellular compartments as they are classified according to the position and number of conserved cysteine. 2-Cys Prx1 and Prx2 are abundant proteins that are ubiquitously expressed mainly in the cytosol, and over 90% of their amino acid sequences are homologous. Prx1 and Prx2 protect cells from ROS-mediated oxidative stress through the elimination of H₂O₂ and regulate cellular signaling through redox-dependent mechanism. In addition, Prx1 and Prx2 are able to bind to a diversity of interaction partners to regulate other various cellular processes in cancer (i.e., regulation of the protein redox status, cell growth, apoptosis, and tumorigenesis). Thus, Prx1 and Prx2 can be potential therapeutic targets and it is particularly important to control their level or activity. This review focuses on cytosolic 2-Cys Prx1 and Prx2 and their role in the regulation of redox signaling based on protein-protein interaction.

Mass spectrometry-based proteomics reveals the distinct nature of the skin proteomes of photoaged compared to intrinsically aged skin

OBJECTIVE

With increasing age, skin is subject to alterations in its organization, which impact on its function as well as having clinical consequences. Proteomics is a useful tool for non-targeted, semi-quantitative simultaneous investigation of high numbers of proteins. In the current study, we utilize proteomics to characterize and contrast age-associated differences in photoexposed and photoprotected skin, with a focus on the epidermis, dermal-epidermal junction and papillary dermis.

METHODS

Skin biopsies from buttock (photoprotected) and forearm (photoexposed) of healthy volunteers (aged 18-30 or ≥65 years) were transversely sectioned from the stratum corneum to a depth of 250 μm. Following SDS-PAGE, each sample lane was segmented prior to analysis by liquid chromatography-mass spectrometry/mass spectrometry. Pathway analysis was carried out using Ingenuity IPA.

RESULTS

Comparison of skin proteomes at buttock and forearm sites revealed differences in relative protein abundance. Ageing in skin on the photoexposed forearm resulted in 80% of the altered proteins being increased with age, in contrast to the photoprotected buttock where 74% of altered proteins with age were reduced. Functionally, age-altered proteins in the photoexposed forearm were associated with conferring structure, energy and metabolism. In the photoprotected buttock, proteins associated with gene expression, free-radical scavenging, protein synthesis and protein degradation were most frequently altered.

CONCLUSION

This study highlights the necessity of not considering photoageing as an accelerated intrinsic ageing, but as a distinct physiological process.

Elevated ER stress exacerbates dextran sulfate sodium-induced colitis in PRDX4-knockout mice

BACKGROUND AND AIMS

Peroxiredoxin 4 (PRDX4), a secretory protein that is preferentially retained in the endoplasmic reticulum (ER), is encoded by a gene located on the X chromosome and highly expressed in colonic tissue. In this study, we investigated the role of PRDX4 by means of male PRDX4-knockout (PRDX4^-/y) mice in the development of intestinal inflammation using a dextran sulfate sodium (DSS)-induced colitis model.

MATERIALS AND METHODS

Acute colitis was induced with DSS (2.5% in drinking water) in wild-type (WT) and PRDX4^-/y male C57BL/6 mice. Histological and biochemical analyses were performed on the colonic tissues.

RESULTS

PRDX4 was mainly localized in the colonic epithelial cells in WT mice. The disease activity index (DAI) scores of PRDX4^-/y mice were significantly higher compared to those of WT mice. Specifically, PRDX4^-/y mice showed marked body weight loss and shortening of colon length compared to WT mice, whereas the myeloperoxidase levels were increased in PRDX4^-/y compared to WT mice. In addition, the mRNA expression levels of TNF-α and IFN-γ were significantly higher in the colonic mucosa of PRDX4^-/y compared to WT mice. Moreover, the levels of CHOP and activated caspase 3 were higher in the colonic tissues of PRDX4^-/y compared to WT mice following treatment with DSS. The ER also showed greater expansion in PRDX4^-/y than WT mice, which was consistent with severe ER stress under PRDX4 deficiency.

CONCLUSION

Our results demonstrated that the lack of PRDX4 aggravated the colonic mucosal damage induced by DSS. Because PRDX4 functions as an ER thiol oxidase as well as an antioxidant, DSS induced oxidative damage and ER stress to a greater degree in PRDX4^-/y than WT mice. These findings suggest that PRDX4 may represent a novel therapeutic molecule in intestinal inflammation.

Piecing Together How Peroxiredoxins Maintain Genomic Stability

Peroxiredoxins, a highly conserved family of thiol oxidoreductases, play a key role in oxidant detoxification by partnering with the thioredoxin system to protect against oxidative stress. In addition to their peroxidase activity, certain types of peroxiredoxins possess other biochemical activities, including assistance in preventing protein aggregation upon exposure to high levels of oxidants (molecular chaperone activity), and the transduction of redox signals to downstream proteins (redox switch activity). Mice lacking the peroxiredoxin Prdx1 exhibit an increased incidence of tumor formation, whereas baker's yeast (Saccharomyces cerevisiae) lacking the orthologous peroxiredoxin Tsa1 exhibit a mutator phenotype. Collectively, these findings suggest a potential link between peroxiredoxins, control of genomic stability, and cancer etiology. Here, we examine the potential mechanisms through which Tsa1 lowers mutation rates, taking into account its diverse biochemical roles in oxidant defense, protein homeostasis, and redox signaling as well as its interplay with thioredoxin and thioredoxin substrates, including ribonucleotide reductase. More work is needed to clarify the nuanced mechanism(s) through which this highly conserved peroxidase influences genome stability, and to determine if this mechanism is similar across a range of species.

Downregulation of peroxiredoxin II suppresses the proliferation and metastasis of gastric cancer cells

Peroxiredoxin (Prx) II is an imperative member of the superfamily of peroxidases. It serves an essential role in scavenging organic hydroperoxide and H2O2. It is involved in the development of various malignant tumors. In order to investigate the significance of Prx II expressions level in gastric cancer (GC), downregulation of Prx II was performed to investigate its role in the proliferation and migration of gastric adenocarcinoma cells. In GC cells and 45 GC specimens, the mRNA and protein expression levels of Prx II were determined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. The Prx II expression profile in another 116 GC specimens was also detected with immunohistochemistry (IHC). The changes in the proliferation and migration of MKN45 and MGC-803 cells folllowing transfection with small interfering RNA (siRNA) were detected by cell counting kit (CCK)-8, western blot analysis, and Transwell migration and invasion assays. The results revealed that the expression of Prx II in GC tissues and GC cells were significantly upregulated compared with the normal control. There was a significant association between the expression level of Prx II and various factors, including tumor size, histological differentiation, the depth of invasion, the stage of tumor-node-metastasis (TNM) and lymph node metastasis in GC (P<0.05). Survival in patients with higher Prx II expression was significantly decreased compared with those with lower Prx II expression (P<0.01). Prx II, depth of invasion, lymph node metastasis and distant metastasis were identified as independent prognosis factors of GC (P<0.05). Knockdown of Prx II significantly suppressed the proliferation and the migration of GC cells. These experiments revealed that Prx II promotes the development of GC, affecting the survival of patients with GC.

Identification and characterization of peroxiredoxin 1 from Lateolabrax japonicus under biotic and abiotic stresses

The peroxiredoxins (Prxs) belong to a novel and evolutionarily conserved superfamily, which can protect cells from oxidative damage caused by ROS and play a vital role in immune responses. In the present study, a 995 base pairs (bp) Prx1 cDNA sequence (LjPrx1) with an open reading frame of 594 bp, which encoding 197 amino acid polypeptides was obtained from L. japonicus. Transcriptional expression analysis indicated that the LjPrx1 mRNA was ubiquitously expressed in all tissues tested, while a comparatively high expression level was detected in head-kidney and blood. After the recombinant LjPrx1 protein was acquired using a prokaryotic expression method, the antioxidant activity was assessed by the catalyzing hydrogen peroxide assay method, and the results showed that the recombinant LjPrx1 possessed an antioxidant activity in a temperature-dependent manner. To further study the function roles of LjPrx1 related to biotic and abiotic stresses, the head-kidney and blood were chosen for the following experiments, and a positive correlation between the expression of LjPrx1 and the different stresses was detected using qRT-PCR. In conclusion, this study provides useful information about the role of the LjPrx1 gene in defense against a variety of toxic factors in L. japonicus, which would broaden our current knowledge of Prx1.

Species comparison of liver proteomes reveals links to naked mole-rat longevity and human aging

Background

Mammals display a wide range of variation in their lifespan. Investigating the molecular networks that distinguish long- from short-lived species has proven useful to identify determinants of longevity. Here, we compared the livers of young and old long-lived naked mole-rats (NMRs) and the phylogenetically closely related, shorter-lived, guinea pigs using an integrated omics approach.

Results

We found that NMR livers display a unique expression pattern of mitochondrial proteins that results in distinct metabolic features of their mitochondria. For instance, we observed a generally reduced respiration rate associated with lower protein levels of respiratory chain components, particularly complex I, and increased capacity to utilize fatty acids. Interestingly, we show that the same molecular networks are affected during aging in both NMRs and humans, supporting a direct link to the extraordinary longevity of both species. Finally, we identified a novel detoxification pathway linked to longevity and validated it experimentally in the nematode Caenorhabditis elegans.

Conclusions

Our work demonstrates the benefits of integrating proteomic and transcriptomic data to perform cross-species comparisons of longevity-associated networks. Using a multispecies approach, we show at the molecular level that livers of NMRs display progressive age-dependent changes that recapitulate typical signatures of aging despite the negligible senescence and extraordinary longevity of these rodents.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0547-y) contains supplementary material, which is available to authorized users.

Beyond ROS clearance: Peroxiredoxins in stress signaling and aging

Antioxidants were long predicted to have lifespan-promoting effects, but in general this prediction has not been well supported. While some antioxidants do seem to have a clear effect on longevity, this may not be primarily as a result of their role in the removal of reactive oxygen species, but rather mediated by other mechanisms such as the modulation of intracellular signaling. In this review we discuss peroxiredoxins, a class of proteinaceous antioxidants with redox signaling and chaperone functions, and their involvement in regulating longevity and stress resistance. Peroxiredoxins have a clear role in the regulation of lifespan and survival of many model organisms, including the mouse, Caenorhabditis elegans and Drosophila melanogaster. Recent research on peroxiredoxins - in these models and beyond - has revealed surprising new insights regarding the interplay between peroxiredoxins and longevity signaling, which will be discussed here in detail. As redox signaling is emerging as a potentially important player in the regulation of longevity and aging, increased knowledge of these fascinating antioxidants and their mode(s) of action is paramount.

Redox-sensitive alteration of replisome architecture safeguards genome integrity

DNA replication requires coordination between replication fork progression and deoxynucleotide triphosphate (dNTP)-generating metabolic pathways. We find that perturbation of ribonucleotide reductase (RNR) in humans elevates reactive oxygen species (ROS) that are detected by peroxiredoxin 2 (PRDX2). In the oligomeric state, PRDX2 forms a replisome-associated ROS sensor, which binds the fork accelerator TIMELESS when exposed to low levels of ROS. Elevated ROS levels generated by RNR attenuation disrupt oligomerized PRDX2 to smaller subunits, whose dissociation from chromatin enforces the displacement of TIMELESS from the replisome. This process instantly slows replication fork progression, which mitigates pathological consequences of replication stress. Thus, redox signaling couples fluctuations of dNTP biogenesis with replisome activity to reduce stress during genome duplication. We propose that cancer cells exploit this pathway to increase their adaptability to adverse metabolic conditions.

Hyperoxidation of Peroxiredoxins: Gain or Loss of Function?

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.

RKIP and peroxiredoxin 2 expression predicts the proliferative potential of gastric cancer stem cells

Gastric cancer is associated with a high mortality rate, with the development of gastric cancer stem cells underlying this. Gastric cancer stem cells are responsible for tumor initiation, progression and recurrence. However, the link between gastric cancer and gastric cancer stem cells remains to be fully understood. Murine models mimic a human microenvironment more accurately than in vitro studies and are useful models for understanding the behavior of different markers. The present study compared the expression of cluster of differentiation 44 (CD44), a stem cell marker, with the expression of other cancer-associated markers, including Raf kinase inhibitor protein (RKIP) and peroxiredoxin 2, in different pathological conditions of gastric cancer development using histological, immunohistological and western blot analyses. Initially, the murine model of gastric cancer was established using N-methyl-N-nitrosourea, a chemical carcinogen. Following initiation of cancer, immunohistochemistry was used to compare the expression of CD44, RKIP and peroxiredoxin 2 at different stages of cancer development. The results suggested CD44 and peroxiredoxin 2 expression was upregulated as the tumor progressed. However, expression of RKIP, a metastasis suppressor, was elevated in the initial stage of gastric cancer and suppressed during the aggressive stages. In agreement with previous data suggesting higher expressions of RKIP in the initial stages of cancer and its downregulation in the advanced stage, the results of the present study revealed that RKIP exhibited a negative effect on initial tumor development, and that the downregulation of RKIP in the advanced stages of cancer facilitated CD44 and peroxiredoxin 2 overexpression.

MnTnBuOE-2-PyP protects normal colorectal fibroblasts from radiation damage and simultaneously enhances radio/chemotherapeutic killing of colorectal cancer cells

Manganese porphyrins have been shown to be potent radioprotectors in a variety of cancer models. However, the mechanism as to how these porphyrins protect normal tissues from radiation damage still remains largely unknown. In the current study, we determine the effects of the manganese porphyrin, MnTnBuOE-2-PyP, on primary colorectal fibroblasts exposed to irradiation. We found that 2 Gy of radiation enhances the fibroblasts' ability to contract a collagen matrix, increases cell size and promotes cellular senesence. Treating fibroblasts with MnTnBuOE-2-PyP significantly inhibited radiation-induced collagen contraction, preserved cell morphology and also inhibited cellular senescence. We further showed that MnTnBuOE-2-PyP enhanced the overall viability of the fibroblasts following exposure to radiation but did not protect colorectal cancer cell viability. Specifically, MnTnBuOE-2-PyP in combination with irradiation, caused a significant decrease in tumor clonogenicity. Since locally advanced rectal cancers are treated with chemoradiation therapy followed by surgery and non-metastatic anal cancers are treated with chemoradiation therapy, we also investigated the effects of MnTnBuOE-2-PyP in combination with radiation, 5-fluorouracil with and without Mitomycin C. We found that MnTnBuOE-2-PyP in combination with Mitomycin C or 5-fluorouracil further enhances those compounds' ability to suppress tumor cell growth. When MnTnBuOE-2-PyP was combined with the two chemotherapeutics and radiation, we observed the greatest reduction in tumor cell growth. Therefore, these studies indicate that MnTnBuOE-2-PyP could be used as a potent radioprotector for normal tissue, while at the same time enhancing radiation and chemotherapy treatment for rectal and anal cancers.

Peroxiredoxin-1 promotes cell proliferation and metastasis through enhancing Akt/mTOR in human osteosarcoma cells

Osteosarcoma is characterized by high propensity for metastasis, especially to the lung, which is the main cause of death. Peroxiredoxin-1 (PRDX1) plays significant roles in multiple processes of initiation and progression of tumorogenesis. However, whether PRDX1 participates in metastasis of osteosarcoma remains unknown. Here, we demonstrate that PRDX1 overexpressed in osteosarcoma tissues comparing to adjacent non-tumor tissues. Two independent cohorts of patients showed high level of PRDX1 correlated with clinicopathological features such as larger tumor size and advanced tumor metastasis stage. While patients with high PRDX1 level have poor prognosis. Notably, expression level of PRDX1 especially increased in lung lesion of osteosarcoma patients, indicating that PRDX1 may promote lung metastasis. Ectopic expression of PRDX1 promotes osteosarcoma cell migration and metastasis in vitro and in vivo, whereas knockdown of PRDX1 expression suppresses cell metastatic behaviors such as invasion and migration. Furthermore, we found that PRDX1 promotes cells metastasis through enhancing Akt/mTOR signal pathway. Taken together, our findings prove the important role of PRDX1 in the molecular etiology of osteosarcoma and suggest that PRDX1 may be a novel prognostic biomarker and therapeutic target for osteosarcoma.

Active-site plasticity revealed in the asymmetric dimer of AnPrx6 the 1-Cys peroxiredoxin and molecular chaperone from Anabaena sp. PCC 7210

Peroxiredoxins (Prxs) are vital regulators of intracellular reactive oxygen species levels in all living organisms. Their activity depends on one or two catalytically active cysteine residues, the peroxidatic Cys (C_P) and, if present, the resolving Cys (C_R). A detailed catalytic cycle has been derived for typical 2-Cys Prxs, however, little is known about the catalytic cycle of 1-Cys Prxs. We have characterized Prx6 from the cyanobacterium Anabaena sp. strain PCC7120 (AnPrx6) and found that in addition to the expected peroxidase activity, AnPrx6 can act as a molecular chaperone in its dimeric state, contrary to other Prxs. The AnPrx6 crystal structure at 2.3 Å resolution reveals different active site conformations in each monomer of the asymmetric obligate homo-dimer. Molecular dynamic simulations support the observed structural plasticity. A FSH motif, conserved in 1-Cys Prxs, precedes the active site PxxxTxxCp signature and might contribute to the 1-Cys Prx reaction cycle.

Gene characteristics, immune and stress responses of PmPrx1 in black tiger shrimp (Penaeus monodon): Insights from exposure to pathogenic bacteria and toxic environmental stressors

Peroxiredoxins (Prxs) are ubiquitous, multifunctional and evolutionarily conserved enzymes that can protect cells from oxidative damage caused by ROS and play a vital role in immune responses. Here, a full-length Prx1 cDNA sequence (PmPrx1) was isolated from Penaeus monodon. The PmPrx1 cDNA was 951 base pairs (bp), encoding 198 amino acid polypeptides. The results of qRT-PCR showed that the PmPrx1 mRNA was ubiquitously expressed in all tissues tested and had a comparatively high expression level in immune-associated tissues (gill, hepatopancreas). To explore the immune and anti-stress roles of PmPrx1, the gills and hepatopancreas were chosen as target tissues in Penaeus monodon and were challenged with bacteria (Vibrio harveyi and Streptococcus agalactiae) and toxic environmental stresses. To further clarify the immune function of PmPrx1 after bacterial challenge, the recombinant PmPrx1 protein was acquired using a prokaryotic expression method. The antioxidant activity of the recombinant PmPrx1 was assessed by the catalyzing hydrogen peroxide assay method, and the results showed obvious antioxidant activity in a dose-dependent and temperature-dependent manner. The antimicrobial activity of purified PmPrx1 protein was evaluated and further studied in vitro relying on a bacterial growth inhibition test which was conducted in both liquid and solid cultures. Furthermore, E. coli transferred with pRSET-PmPrx1 was dramatically protected in response to metal toxicity and H₂O₂ oxidative stress. In summary, this study provides useful information about the role of the Prx1 gene in defense against a variety of toxic factors in shrimps that help to further clarify the functional mechanism of Prx.

Proteome Stability as a Key Factor of Genome Integrity

DNA damage is constantly produced by both endogenous and exogenous factors; DNA lesions then trigger the so-called DNA damaged response (DDR). This is a highly synchronized pathway that involves recognition, signaling and repair of the damage. Failure to eliminate DNA lesions is associated with genome instability, a driving force in tumorigenesis. Proteins carry out the vast majority of cellular functions and thus proteome quality control (PQC) is critical for the maintenance of cellular functionality. PQC is assured by the proteostasis network (PN), which under conditions of proteome instability address the triage decision of protein fold, hold, or degrade. Key components of the PN are the protein synthesis modules, the molecular chaperones and the two main degradation machineries, namely the autophagy-lysosome and the ubiquitin-proteasome pathways; also, part of the PN are a number of stress-responsive cellular sensors including (among others) heat shock factor 1 (Hsf1) and the nuclear factor erythroid 2-related factor 2 (Nrf2). Nevertheless, the lifestyle- and/or ageing-associated gradual accumulation of stressors results in increasingly damaged and unstable proteome due to accumulation of misfolded proteins and/or protein aggregates. This outcome may then increase genomic instability due to reduced fidelity in processes like DNA replication or repair leading to various age-related diseases including cancer. Herein, we review the role of proteostatic machineries in nuclear genome integrity and stability, as well as on DDR responses.

Targeted Annotation of S-Sulfonylated Peptides by Selective Infrared Multiphoton Dissociation Mass Spectrometry

Protein S-sulfinylation (R-SO₂^-) and S-sulfonylation (R-SO₃^-) are irreversible oxidative post-translational modifications of cysteine residues. Greater than 5% of cysteines are reported to occupy these higher oxidation states, which effectively inactivate the corresponding thiols and alter the electronic and physical properties of modified proteins. Such higher oxidation states are reached after excessive exposure to cellular oxidants, and accumulate across different disease states. Despite widespread and functionally relevant cysteine oxidation across the proteome, there are currently no robust methods to profile higher order cysteine oxidation. Traditional data-dependent liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods generally miss low-occupancy modifications in complex analyses. Here, we present a data-independent acquisition (DIA) LC/MS-based approach, leveraging the high IR absorbance of sulfoxides at 10.6 μm, for selective dissociation and discovery of S-sulfonated peptides. Across peptide standards and protein digests, we demonstrate selective infrared multiphoton dissociation (IRMPD) of S-sulfonated peptides in the background of unmodified peptides. This selective DIA IRMPD LC/MS-based approach allows identification and annotation of S-sulfonated peptides across complex mixtures while providing sufficient sequence information to localize the modification site.

Tubulin Beta-3 Chain as a New Candidate Protein Biomarker of Human Skin Aging: A Preliminary Study

Skin aging is a complex process, and a lot of efforts have been made to identify new and specific targets that could help to diagnose, prevent, and treat skin aging. Several studies concerning skin aging have analyzed the changes in gene expression, and very few investigations have been performed at the protein level. Moreover, none of these proteomic studies has used a global quantitative labeled proteomic offgel approach that allows a more accurate description of aging phenotype. We applied such an approach on human primary keratinocytes obtained from sun-nonexposed skin biopsies of young and elderly women. A total of 517 unique proteins were identified, and 58 proteins were significantly differentially expressed with 40 that were downregulated and 18 upregulated with aging. Gene ontology and pathway analysis performed on these 58 putative biomarkers of skin aging evidenced that these dysregulated proteins were mostly involved in metabolism and cellular processes such as cell cycle and signaling pathways. Change of expression of tubulin beta-3 chain was confirmed by western blot on samples originated from several donors. Thus, this study suggested the tubulin beta-3 chain has a promising biomarker in skin aging.

Light-sensing via hydrogen peroxide and a peroxiredoxin

Yeast lacks dedicated photoreceptors; however, blue light still causes pronounced oscillations of the transcription factor Msn2 into and out of the nucleus. Here we show that this poorly understood phenomenon is initiated by a peroxisomal oxidase, which converts light into a hydrogen peroxide (H₂O₂) signal that is sensed by the peroxiredoxin Tsa1 and transduced to thioredoxin, to counteract PKA-dependent Msn2 phosphorylation. Upon H₂O₂, the nuclear retention of PKA catalytic subunits, which contributes to delayed Msn2 nuclear concentration, is antagonized in a Tsa1-dependent manner. Conversely, peroxiredoxin hyperoxidation interrupts the H₂O₂ signal and drives Msn2 oscillations by superimposing on PKA feedback regulation. Our data identify a mechanism by which light could be sensed in all cells lacking dedicated photoreceptors. In particular, the use of H₂O₂ as a second messenger in signalling is common to Msn2 oscillations and to light-induced entrainment of circadian rhythms and suggests conserved roles for peroxiredoxins in endogenous rhythms.

While yeasts lack dedicated photoreceptors, they nonetheless possess metabolic rhythms responsive to light. Here the authors find that light signalling in budding yeast involves the production of H₂O₂, which in turn regulates protein kinase A through a peroxiredoxin-thioredoxin redox relay.

Graded Response of the Multifunctional 2-Cysteine Peroxiredoxin, CgPrx, to Increasing Levels of Hydrogen Peroxide in Corynebacterium glutamicum

AIMS

Eukaryotic typical 2-cysteine (Cys) peroxiredoxins (Prxs) are multifunctional proteins subjected to complex regulation and play important roles in oxidative stress resistance, hydrogen peroxide (H₂O₂) signaling modulation, aging, and cancer, but the information on the biochemical functions and regulation mechanisms of prokaryotic atypical 2-Cys Prxs is largely lacking.

RESULTS

In this study, we show that at low peroxide concentrations, the atypical 2-Cys Prx in Corynebacterium glutamicum (CgPrx) mainly exists as monomers and displays thioredoxin (Trx)-dependent peroxidase activity. Moderate oxidative stress causes reversible S-mycothiolation of the H₂O₂-sensing Cys63 residue, which keeps CgPrx exclusively in dimer form with neither peroxidase nor chaperone activity. Then, the increased levels of H₂O₂ could act as a messenger to oxidize the redox-sensitive regulator hydrogen peroxide-inducible gene activator, leading to activation of expression of the more efficient mycothiol peroxidase and catalase to eliminate excessive peroxide. If oxidative stress is too severe, the H₂O₂-sensing Cys63 becomes hyperoxidized to sulfonic acid, which irreversibly inactivates the peroxidase activity, and most of CgPrx will be converted to multimeric chaperones for salvage of damaged proteins.

INNOVATION

We demonstrate for the first time that atypical 2-Cys CgPrx acts as both a Trx-dependent peroxidase and a molecular chaperone and plays a regulatory role in modulating the peroxide-mediated signaling cascades.

CONCLUSION

These results reveal that CgPrx functions as a multifunctional protein crucial for adapting appropriate responses to different levels of oxidative challenge in C. glutamicum. Antioxid. Redox Signal. 26, 1-14.

Happily (n)ever after: Aging in the context of oxidative stress, proteostasis loss and cellular senescence

Aging is a complex phenomenon and its impact is becoming more relevant due to the rising life expectancy and because aging itself is the basis for the development of age-related diseases such as cancer, neurodegenerative diseases and type 2 diabetes. Recent years of scientific research have brought up different theories that attempt to explain the aging process. So far, there is no single theory that fully explains all facets of aging. The damage accumulation theory is one of the most accepted theories due to the large body of evidence found over the years. Damage accumulation is thought to be driven, among others, by oxidative stress. This condition results in an excess attack of oxidants on biomolecules, which lead to damage accumulation over time and contribute to the functional involution of cells, tissues and organisms. If oxidative stress persists, cellular senescence is a likely outcome and an important hallmark of aging. Therefore, it becomes crucial to understand how senescent cells function and how they contribute to the aging process. This review will cover cellular senescence features related to the protein pool such as morphological and molecular hallmarks, how oxidative stress promotes protein modifications, how senescent cells cope with them by proteostasis mechanisms, including antioxidant enzymes and proteolytic systems. We will also highlight the nutritional status of senescent cells and aged organisms (including human clinical studies) by exploring trace elements and micronutrients and on their importance to develop strategies that might increase both, life and health span and postpone aging onset.

Transition steps in peroxide reduction and a molecular switch for peroxide robustness of prokaryotic peroxiredoxins

In addition to their antioxidant function, the eukaryotic peroxiredoxins (Prxs) facilitate peroxide-mediated signaling by undergoing controlled inactivation by peroxide-driven over-oxidation. In general, the bacterial enzyme lacks this controlled inactivation mechanism, making it more resistant to high H₂O₂ concentrations. During peroxide reduction, the active site alternates between reduced, fully folded (FF), and oxidized, locally unfolded (LU) conformations. Here we present novel insights into the divergence of bacterial and human Prxs in robustness and sensitivity to inactivation, respectively. Structural details provide new insights into sub-steps during the catalysis of peroxide reduction, enabling the transition from an FF to a LU conformation. Complementary to mutational and enzymatic results, these data unravel the essential role of the C-terminal tail of bacterial Prxs to act as a molecular switch, mediating the transition from an FF to a LU state. In addition, we propose that the C-terminal tail has influence on the propensity of the disulphide bond formation, indicating that as a consequence on the robustness and sensitivity to over-oxidation. Finally, a physical linkage between the catalytic site, the C-terminal tail and the oligomer interface is described.

SIRT2 Deacetylates and Inhibits the Peroxidase Activity of Peroxiredoxin-1 to Sensitize Breast Cancer Cells to Oxidant Stress-Inducing Agents

SIRT2 is a protein deacetylase with tumor suppressor activity in breast and liver tumors where it is mutated; however, the critical substrates mediating its antitumor activity are not fully defined. Here we demonstrate that SIRT2 binds, deacetylates, and inhibits the peroxidase activity of the antioxidant protein peroxiredoxin (Prdx-1) in breast cancer cells. Ectopic overexpression of SIRT2, but not its catalytically dead mutant, increased intracellular levels of reactive oxygen species (ROS) induced by hydrogen peroxide, which led to increased levels of an overoxidized and multimeric form of Prdx-1 with activity as a molecular chaperone. Elevated levels of SIRT2 sensitized breast cancer cells to intracellular DNA damage and cell death induced by oxidative stress, as associated with increased levels of nuclear FOXO3A and the proapoptotic BIM protein. In addition, elevated levels of SIRT2 sensitized breast cancer cells to arsenic trioxide, an approved therapeutic agent, along with other intracellular ROS-inducing agents. Conversely, antisense RNA-mediated attenuation of SIRT2 reversed ROS-induced toxicity as demonstrated in a zebrafish embryo model system. Collectively, our findings suggest that the tumor suppressor activity of SIRT2 requires its ability to restrict the antioxidant activity of Prdx-1, thereby sensitizing breast cancer cells to ROS-induced DNA damage and cell cytotoxicity. Cancer Res; 76(18); 5467-78. ©2016 AACR.

Predicting and Understanding the Enzymatic Inhibition of Human Peroxiredoxin 5 by 4-Substituted Pyrocatechols by Combining Funnel Metadynamics, Solution NMR, and Steady-State Kinetics

Funnel metadynamics is a kind of computational simulation used to enhance the sampling of protein-ligand binding events in solution. By characterization of the binding interaction events, an estimated absolute binding free energy can be calculated. Nuclear magnetic resonance and funnel metadynamics were used to evaluate the binding of pyrocatechol derivatives (catechol, 4-methylcatechol, and 4-tert-butylcatechol) to human peroxiredoxin 5. Human peroxiredoxins are peroxidases involved in cellular peroxide homeostasis. Recently, overexpressed or suppressed peroxiredoxin levels have been linked to various diseases. Here, the catechol derivatives were found to be inhibitors against human peroxiredoxin 5 through a partial mixed type noncompetitive mechanism. Funnel metadynamics provided a microscopic model for interpreting the inhibition mechanism. Correlations were observed between the inhibition constants and the absolute binding free energy. Overall, this study showcases the fact that funnel metadynamics simulations can be employed as a preliminary approach to gain an in-depth understanding of potential enzyme inhibitors.

Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed

Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage.

Identification of proteins that are differentially expressed in brains with Alzheimer's disease using iTRAQ labeling and tandem mass spectrometry

Alzheimer's disease is one of the leading causes of dementia in the elderly. It is considered the result of complex events involving both genetic and environmental factors. To gain further insights into this complexity, we quantitatively analyzed the proteome of cortex region of brains from patients diagnosed with Alzheimer's disease, using a bottom-up proteomics approach. We identified 721 isobaric-tagged polypeptides. From this universe, 61 were found overexpressed and 69 subexpressed in three brains with Alzheimer's disease in comparison to a normal brain. We determined that the most affected processes involving the overexpressed polypeptides corresponded to ROS and stress responses. For the subexpressed polypeptides, the main processes affected were oxidative phosphorylation, organellar acidification and cytoskeleton. We used Drosophila to validate some of the hits, particularly those non-previously described as connected with the disease, such as Sideroflexin and Phosphoglucomutase-1. We manipulated their homolog genes in Drosophila models of Aβ- and Tau-induced pathology. We found proteins that can either modify Aβ toxicity, Tau toxicity or both, suggesting specific interactions with different pathways. This approach illustrates the potential of Drosophila to validate hits after MS studies and suggest that model organisms should be included in the pipeline to identify relevant targets for Alzheimer's disease.

BIOLOGICAL SIGNIFICANCE

We report a set of differentially expressed proteins in three Alzheimer's disease brains in comparison to a normal brain. Our analyses allowed us to identify that the main affected pathways were ROS and stress responses, oxidative phosphorylation, organellar acidification and cytoskeleton. We validated some identified proteins using genetic models of Amyloid-β and Tau-induced pathology in Drosophila melanogaster. With this approach, Sideroflexin and Phosphoglucomutase-1 were identified as novel proteins connected with Alzheimer's disease.