Peroxisomal catalases from the yeasts Pichia pastoris and Kluyveromyces lactis as models for oxidative damage in higher eukaryotes

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.

Antifungal activity of the repurposed drug disulfiram against Cryptococcus neoformans

Fungal infections have become clinically challenging owing to the emergence of drug resistance in invasive fungi and the rapid increase in the number of novel pathogens. The development of drug resistance further restricts the use of antifungal agents. Therefore, there is an urgent need to identify alternative treatments for Cryptococcus neoformans (C. neoformans). Disulfiram (DSF) has a good human safety profile and promising applications as an antiviral, antifungal, antiparasitic, and anticancer agent. However, the effect of DSF on Cryptococcus is yet to be thoroughly investigated. This study investigated the antifungal effects and the mechanism of action of DSF against C. neoformans to provide a new theoretical foundation for the treatment of Cryptococcal infections. In vitro studies demonstrated that DSF inhibited Cryptococcus growth at minimum inhibitory concentrations (MICs) ranging from 1.0 to 8.0 μg/mL. Combined antifungal effects have been observed for DSF with 5-fluorocytosine, amphotericin B, terbinafine, or ketoconazole. DSF exerts significant protective effects and synergistic effects combined with 5-FU for Galleria mellonella infected with C. neoformans. Mechanistic investigations showed that DSF dose-dependently inhibited melanin, urease, acetaldehyde dehydrogenase, capsule and biofilm viability of C. neoformans. Further studies indicated that DSF affected C. neoformans by interfering with multiple biological pathways, including replication, metabolism, membrane transport, and biological enzyme activity. Potentially essential targets of these pathways include acetaldehyde dehydrogenase, catalase, ATP-binding cassette transporter (ABC transporter), and iron-sulfur cluster transporter. These findings provide novel insights into the application of DSF and contribute to the understanding of its mechanisms of action in C. neoformans.

Highly efficient expression and secretion of human lysozyme using multiple strategies in Pichia pastoris

BACKGROUND

Human lysozyme (hLYZ), an emerging antibacterial agent, has extensive application in the food and pharmaceutical industries. However, the source of hLYZ is particularly limited.

RESULTS

To achieve highly efficient expression and secretion of hLYZ in Pichia pastoris, multiple strategies including G418 sulfate screening, signal sequence optimization, vacuolar sorting receptor VPS10 disruption, and chaperones/transcription factors co-expression were applied. The maximal enzyme activity of extracellular hLYZ in a shaking flask was 81,600 ± 5230 U mL-1 , which was about five times of original strain. To further reduce the cost, the optimal medium RDMY was developed and the highest hLYZ activity reached 352,000 ± 16,696.5 U mL-1 in a 5 L fermenter.

CONCLUSION

This research provides a very useful and cost-effective approach for the hLYZ production in P. pastoris and can also be applied to the production of other recombinant proteins.

Anti-Sporotrichotic Activity, Lambert-W Inhibition Kinetics and 3D Structural Characterization of Sporothrix schenckii Catalase as Target of Glucosinolates from Moringa oleifera

Most human fungal infections exhibit significant defensive oxidative stress responses, which contribute to their pathogenicity. An important component of these reactions is the activation of catalase for detoxification. To discover new antifungal chemicals, the antifungal activity of methanol extracts of Moringa oleifera from two commercial products (Akuanandi and Mas Lait) was investigated. The methanolic extracts’ activity against Sporothrix schenckii was determined using an assay for minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC). The MIC concentrations varied between 0.5 μg/mL and 8 μg/mL. Akuanandi extract had the lowest MIC (0.5 μg/mL) and MLC (1 μg/mL) values. M. oleifera methanolic extracts were tested for catalase inhibition. The Ki values of the M. oleifera extract against S. schenckii catalase (SsCAT) was found to be 0.7 μg/mL for MOE-AK and 0.08 μg/mL for MOE-ML. Catalase’s 3D structure in SsCAT is unknown. The homology of SsCAT was modeled with an in silico study using a 3D structure from SWISS MODEL and validation the predicted 3D structure was carried out using PROCHECK and MolProbity. Docking simulations were used to analyze protein interactions using Pymol, PoseView, and PLIP. The results revealed that M. oleifera glucosinolates interacts with SsCAT. A molecular interaction analysis revealed two inhibitor compounds (glucosinalbin and glucomoringin) with high binding affinity to key allosteric-site residues. The binding energies revealed that glucosinalbin and glucomoringin bind with high affinity to SsCAT (docking energy values: −9.8 and −9.0 kcal/mol, respectively). The findings of this study suggest that glucosinolates derived from M. oleifera could be used instead of synthetic fungicides to control S. schenckii infections. We hope that the findings of this work will be valuable for developing and testing novel natural anti-sporothrix therapeutic agents in the future.

Post-translational modifications of proteins associated with yeast peroxisome membrane: An essential mode of regulatory mechanism

Peroxisomes are single membrane‐bound organelles important for the optimum functioning of eukaryotic cells. Seminal discoveries in the field of peroxisomes are made using yeast as a model. Several proteins required for the biogenesis and function of peroxisomes are identified to date. As with proteins involved in other major cellular pathways, peroxisomal proteins are also subjected to regulatory post‐translational modifications. Identification, characterization and mapping of these modifications to specific amino acid residues on proteins are critical toward understanding their functional significance. Several studies have tried to identify post‐translational modifications of peroxisomal proteins and determine their impact on peroxisome structure and function. In this manuscript, we provide an overview of the various post‐translational modifications that govern the peroxisome dynamics in yeast.

Oxidative stress tolerance contributes to heterologous protein production in Pichia pastoris

BACKGROUND

Pichia pastoris (syn. Komagataella phaffii) is an important yeast system for heterologous protein expression. A robust P. pastoris mutant with oxidative and thermal stress cross-tolerance was acquired in our previous study. The robust mutant can express a 2.5-fold higher level of lipase than its wild type (WT) under methanol induction conditions.

RESULTS

In this study, we found that the robust mutant not only can express a high level of lipase, but also can express a high level of other heterogeneous proteins (e.g., green fluorescence protein) under methanol induction conditions. Additionally, the intracellular reactive oxygen species (ROS) levels in the robust mutant were lower than that in the WT under methanol induction conditions. To figure out the difference of cellular response to methanol between the WT and the robust mutant, RNA-seq was detected and compared. The results of RNA-seq showed that the expression levels of genes related to antioxidant, MAPK pathway, ergosterol synthesis pathway, transcription factors, and the peroxisome pathway were upregulated in the robust mutant compared to the WT. The upregulation of these key pathways can improve the oxidative stress tolerance of strains and efficiently eliminate cellular ROS. Hence, we inferred that the high heterologous protein expression efficiency in the robust mutant may be due to its enhanced oxidative stress tolerance. Promisingly, we have indeed increased the expression level of lipase up to 1.6-fold by overexpressing antioxidant genes in P. pastoris.

CONCLUSIONS

This study demonstrated the impact of methanol on the expression levels of genes in P. pastoris and emphasized the contribution of oxidative stress tolerance on heterologous protein expression in P. pastoris. Our results shed light on the understanding of protein expression mechanism in P. pastoris and provided an idea for the rational construction of robust yeast with high expression ability.

Augmented peroxisomal ROS buffering capacity renders oxidative and thermal stress cross-tolerance in yeast

Background

Thermotolerant yeast has outstanding potential in industrial applications. Komagataella phaffii (Pichia pastoris) is a common cell factory for industrial production of heterologous proteins.

Results

Herein, we obtained a thermotolerant K. phaffii mutant G14 by mutagenesis and adaptive evolution. G14 exhibited oxidative and thermal stress cross-tolerance and high heterologous protein production efficiency. The reactive oxygen species (ROS) level and lipid peroxidation in G14 were reduced compared to the parent. Oxidative stress response (OSR) and heat shock response (HSR) are two major responses to thermal stress, but the activation of them was different in G14 and its parent. Compared with the parent, G14 acquired the better performance owing to its stronger OSR. Peroxisomes, as the main cellular site for cellular ROS generation and detoxification, had larger volume in G14 than the parent. And, the peroxisomal catalase activity and expression level in G14 was also higher than that of the parent. Excitingly, the gene knockdown of CAT encoding peroxisomal catalase by dCas9 severely reduced the oxidative and thermal stress cross-tolerance of G14. These results suggested that the augmented OSR was responsible for the oxidative and thermal stress cross-tolerance of G14. Nevertheless, OSR was not strong enough to protect the parent from thermal stress, even when HSR was initiated. Therefore, the parent cannot recover, thereby inducing the autophagy pathway and resulting in severe cell death.

Conclusions

Our findings indicate the importance of peroxisome and the significance of redox balance in thermotolerance of yeasts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01623-1.

Multi-Faceted Systems Biology Approaches Present a Cellular Landscape of Phenolic Compound Inhibition in Saccharomyces cerevisiae

Synthetic biology has played a major role in engineering microbial cell factories to convert plant biomass (lignocellulose) to fuels and bioproducts by fermentation. However, the final product yield is limited by inhibition of microbial growth and fermentation by toxic phenolic compounds generated during lignocellulosic pre-treatment and hydrolysis. Advances in the development of systems biology technologies (genomics, transcriptomics, proteomics, metabolomics) have rapidly resulted in large datasets which are necessary to obtain a holistic understanding of complex biological processes underlying phenolic compound toxicity. Here, we review and compare different systems biology tools that have been utilized to identify molecular mechanisms that modulate phenolic compound toxicity in Saccharomyces cerevisiae. By focusing on and comparing functional genomics and transcriptomics approaches we identify common mechanisms potentially underlying phenolic toxicity. Additionally, we discuss possible ways by which integration of data obtained across multiple unbiased approaches can result in new avenues to develop yeast strains with a significant improvement in tolerance to phenolic fermentation inhibitors.