Heavy metal exposure induces Yap1 and Hac1 mediated derepression of GSH1 and KAR2 by Tup1-Cyc8 complex

Dissecting the role of mitogen-activated protein kinase Hog1 in yeast flocculation

Living organisms are frequently exposed to multiple biotic and abiotic stress forms during their lifetime. Organisms cope with stress conditions by regulating their gene expression programs. In response to different environmental stress conditions, yeast cells activate different tolerance mechanisms, many of which share common signaling pathways. Flocculation is one of the key mechanisms underlying yeast survival under unfavorable environmental conditions, and the Tup1-Cyc8 corepressor complex is a major regulator of this process. Additionally, yeast cells can utilize different mitogen-activated protein kinase (MAPK) pathways to modulate gene expression during stress conditions. Here, we show that the high osmolarity glycerol (HOG) MAPK pathway is involved in the regulation of yeast flocculation. We observed that the HOG MAPK pathway was constitutively activated in flocculating cells, and found that the interaction between phosphorylated Hog1 and the FLO genes promoter region increased significantly upon sodium chloride exposure. We found that treatment of cells with cantharidin decreased Hog1 phosphorylation, causing a sharp reduction in the expression of FLO genes and the flocculation phenotype. Similarly, deletion of HOG1 in yeast cells reduced flocculation. Altogether, our results suggest a role for HOG MAPK signaling in the regulation of FLO genes and yeast flocculation.

ER stress-induced transcriptional response reveals tolerance genes in yeast

Saccharomyces cerevisiae is important for protein secretion studies, yet the complexities of protein synthesis and secretion under endoplasmic reticulum (ER) stress conditions remain not fully understood. ER stress, triggered by alterations in the ER protein folding environment, poses substantial challenges to cells, especially during heterologous protein production. In this study, we used RNA-seq to analyze the transcriptional responses of yeast strains to ER stress induced by reagents such as tunicamycin (Tm) or dithiothreitol (DTT). Our gene expression analysis revealed several crucial genes, such as HMO1 and BIO5, that are involved in ER-stress tolerance. Through metabolic engineering, the best engineered strain R23 with HMO1 overexpression and BIO5 deletion, showed enhanced ER stress tolerance and improved protein folding efficiency, leading to a 2.14-fold increase in α-amylase production under Tm treatment and a 2.04-fold increase in cell density under DTT treatment. Our findings contribute to the understanding of cellular responses to ER stress and provide a basis for further investigations into the mechanisms of ER stress at the cellular level.

Pollutants to pathogens: The role of heavy metals in modulating TGF-β signaling and lung cancer risk

Lung cancer is a malignant tumor that develops in the lungs due to the uncontrolled growth of aberrant cells. Heavy metals, such as arsenic, cadmium, mercury, and lead, are metallic elements characterized by their high atomic weights and densities. Anthropogenic activities, such as industrial operations and pollution, have the potential to discharge heavy metals into the environment, hence presenting hazards to ecosystems and human well-being. The TGF-β signalling pathways have a crucial function in controlling several cellular processes, with the ability to both prevent and promote tumor growth. TGF-β regulates cellular responses by interacting in both canonical and non-canonical signalling pathways. Research employing both in vitro and in vivo models has shown that heavy metals may trigger TGF-β signalling via complex molecular pathways. Experiments conducted in a controlled laboratory environment show that heavy metals like cadmium and arsenic may directly bind to TGF-β receptors, leading to alterations in their structure that enable the receptor to be phosphorylated. Activation of this route sets in motion subsequent signalling cascades, most notably the canonical Smad pathway. The development of lung cancer has been linked to heavy metals, which are ubiquitous environmental pollutants. To grasp the underlying processes, it is necessary to comprehend their molecular effect on TGF-β pathways. With a particular emphasis on its consequences for lung cancer, this abstract delves into the complex connection between exposure to heavy metals and the stimulation of TGF-β signalling.

Unveiling the super tolerance of Candida nivariensis to oxidative stress: insights into the involvement of a catalase

Yeast cells involved in fermentation processes face various stressors that disrupt redox homeostasis and cause cellular damage, making the study of oxidative stress mechanisms crucial. In this investigation, we isolated a resilient yeast strain, Candida nivariensis GXAS-CN, capable of thriving in the presence of high concentrations of H2O2. Transcriptomic analysis revealed the up-regulation of multiple antioxidant genes in response to oxidative stress. Deletion of the catalase gene Cncat significantly impacted H2O2-induced oxidative stress. Enzymatic analysis of recombinant CnCat highlighted its highly efficient catalase activity and its essential role in mitigating H2O2. Furthermore, over-expression of CnCat in Saccharomyces cerevisiae improved oxidative resistance by reducing intracellular ROS accumulation. The presence of multiple stress-responsive transcription factor binding sites at the promoters of antioxidative genes indicates their regulation by different transcription factors. These findings demonstrate the potential of utilizing the remarkably tolerant C. nivariensis GXAS-CN or enhancing the resistance of S. cerevisiae to improve the efficiency and cost-effectiveness of industrial fermentation processes.IMPORTANCEEnduring oxidative stress is a crucial trait for fermentation strains. The importance of this research is its capacity to advance industrial fermentation processes. Through an in-depth examination of the mechanisms behind the remarkable H2O2 resistance in Candida nivariensis GXAS-CN and the successful genetic manipulation of this strain, we open the door to harnessing the potential of the catalase CnCat for enhancing the oxidative stress resistance and performance of yeast strains. This pioneering achievement creates avenues for fine-tuning yeast strains for precise industrial applications, ultimately leading to more efficient and cost-effective biotechnological processes.

Systematic analysis of tup1 and cyc8 mutants reveals distinct roles for TUP1 and CYC8 and offers new insight into the regulation of gene transcription by the yeast Tup1-Cyc8 complex

The Tup1-Cyc8 complex in Saccharomyces cerevisiae was one of the first global co-repressors of gene transcription discovered. However, despite years of study, a full understanding of the contribution of Tup1p and Cyc8p to complex function is lacking. We examined TUP1 and CYC8 single and double deletion mutants and show that CYC8 represses more genes than TUP1, and that there are genes subject to (i) unique repression by TUP1 or CYC8, (ii) redundant repression by TUP1 and CYC8, and (iii) there are genes at which de-repression in a cyc8 mutant is dependent upon TUP1, and vice-versa. We also reveal that Tup1p and Cyc8p can make distinct contributions to commonly repressed genes most likely via specific interactions with different histone deacetylases. Furthermore, we show that Tup1p and Cyc8p can be found independently of each other to negatively regulate gene transcription and can persist at active genes to negatively regulate on-going transcription. Together, these data suggest that Tup1p and Cyc8p can associate with active and inactive genes to mediate distinct negative and positive regulatory roles when functioning within, and possibly out with the complex.

Variation of the toxicity caused by key contaminants in industrial wastewater along the treatment train of Fenton-activated sludge-advanced oxidation processes

Industrial wastewater contains a mixture of refractory and hazardous pollutants that have comprehensive toxic effects. We investigated the treatment of a long-chain industrial wastewater treatment train containing Fenton, biological anoxic/oxic (AO), and heterogeneous ozone catalytic oxidation (HOCO) processes, and evaluated their detoxification effect based on the analysis of the genic toxicity of some key contaminants. The results showed that although the effluent met the discharge standard in terms of traditional quality parameters, the long-chain treatment process could not effectively detoxify the industrial wastewater. The analysis results of summer samples showed that the Fenton process increased the total toxicity and genotoxicity of the organics, concerned metals, and non-volatile pollutants, whereas the A/O process increased the toxicity of the organics and non-volatile pollutants, and the HOCO process led to higher toxicity caused by metals and non-volatile pollutants. The outputs of the winter samples indicated that the Fenton process reduced the total toxicity and genotoxicity caused by non-volatile pollutants but increased that of the organics and concerned metals. The effect of the A/O process on the effluent toxicity in winter was the same as that in summer, whereas the HOCO process increased the total toxicity and genotoxicity of the metals in winter samples. Correlation analysis showed that various toxicity stresses were significantly correlated with the variation of these key pollutants in wastewater. Our results could provide a reference for the optimization of industrial wastewater treatment plants (IWTPs) by selecting more suitable treatment procedures to reduce the toxicity of different contaminants.

YAP1 silencing attenuated lung injury/fibrosis but worsened diaphragmatic function by regulating oxidative stress and inflammation response in mice

Oxidative stress is a crucial mechanism in the pathophysiology of lung injury/fibrosis and diaphragmatic dysfunction. Yes-associated protein 1 (YAP1) is a key oxidative stress response regulator. However, how lung injury/fibrosis and the subsequent YAP1 silencing treatment affect diaphragmatic function remains largely uncharacterized. In this study, mice models of acute lipopolysaccharide (LPS) and paraquat exposure were used to establish acute lung injury and chronic pulmonary fibrosis. AT2 and C2C12 cells were co-cultured under LPS and paraquat challenge. YAP1 was interfered with shRNA given in vivo and verteporfin administration in vitro. Pulmonary histology, contractile properties, and cross-sectional areas (CSAs) of the diaphragm and gastrocnemius were evaluated. Histological and biochemical analyses were performed for targeted biomarker determination. We found that LPS and paraquat caused significant lung injury/fibrosis and significantly reduced the diaphragmatic-specific force and CSAs compared with the control. YAP1 silencing alleviated inflammatory cell infiltration or collagen deposition in the lungs yet worsened the already impaired diaphragmatic function by increasing inflammatory cytokines (IL-6 and TNF-α), mitochondrial reactive oxidative species (ROS) emission, protein degradation (Murf-1, atrogin-1, and calpain), and decreasing antioxidant capabilities (superoxide dismutase 2 and glutathione peroxidase). No significant improvements were observed in diaphragmatic function by transient YAP1 knockdown in the gastrocnemius. In vitro, LPS- or paraquat-caused cytotoxicity in AT2 cells was mostly alleviated by verteporfin in a concentration that was 20-fold higher than that in C2C12 cells (20 and 1 μg/mL, respectively). Finally, 0.5 μg/mL of verteporfin significantly ameliorated hydrogen peroxide-induced proteolytic activity and antioxidant enzyme suppression in C2C12 cells, whereas 2 μg/mL of verteporfin deteriorated the same. Collectively, lung injury/fibrosis adversely affects the diaphragm. YAP1 inhibition alleviates lung injury/fibrosis but worsens diaphragmatic function potentially by enhancing inflammatory cytokines and ROS-mediated protein degradation. This disparity might be attributed to differences in susceptibility to YAP1 inhibition between muscles and the lungs.

Fecal microbiome transplantation attenuates manganese-induced neurotoxicity through regulation of the apelin signaling pathway by inhibition of autophagy in mouse brain

Manganese (Mn) is a common environmental pollutant. Mn exposure can lead to neurodegenerative diseases resembling Parkinson's disease, and has become a major public health concern. However, the mechanism of Mn-induced neurotoxicity in the brain is not clear. Fecal microbiome transplantation (FMT) may alleviate the neurotoxicity of Mn exposure by remodeling the gut microbiota. In this study, MnCl₂ (manganese chloride) was administered to mice as in drinking water (Mn: 200 mg/L), and fecal matter from donor mice was administered by oral gavage every other day to the recipient mice. The Mn exposure model (Mn group) and FMT model (Mn+FMT group) were established and analyzed 5 weeks post-exposure. The Wipi1 gene exhibited the most significant increase associated with Mn exposure and Mn+FMT treatment groups based on transcriptome analysis. Combined analysis of transcriptomics and proteomics demonstrated that the apelin signaling pathway is the main pathway affected by FMT during Mn exposure. Immunofluorescence and Western blot showed that the expression of key proteins (Beclin-1, LC-3B, and PINK1) associated with autophagy in the hippocampus was robustly activated in the Mn exposure group, but attenuation was observed in Mn+FMT mice, suggesting a critical role of autophagy in neurotoxicity induced by Mn exposure. Our research provides evidence for the neurotoxic effects of Mn exposure through autophagy activation and provides an underlying mechanism of FMT protection against Mn-induced neurotoxicity through regulation of the apelin signaling pathway.