Abstract
Protein phosphatase Z1 (Ppz1) has been shown to take part in important physiological functions in fungi including a contribution to virulence of Candida albicans. Although its involvement in the oxidative stress response has also been documented, the exact mechanism of action of its protective effect against oxidative damage remains unknown. By developing a pipeline to analyze the biophysical properties of the cell membrane in fungi, we demonstrate that the plasma membrane of Ppz1-KO Candida albicans displays increased sensitivity to tert-butyl-hydroperoxide-induced oxidative damage. In particular, the response to the oxidizing agent, characterized by increased lipid peroxidation, reduced lipid order, and inhibited lateral mobility of plasma membrane components, is significantly more pronounced in the Ppz1-KO C. albicans strain than in the wild-type counterpart. Remarkably, membrane constituents became almost completely immobile in the phosphatase deletion mutant exposed to oxidative stress. Furthermore, moderately elevated membrane lipid peroxidation accompanied by the aforementioned changes in the biophysical characteristics of the plasma membrane are already detectable in untreated Ppz1-KO cells indicating latent membrane damage even in the absence of oxidative stress. In conclusion, the hypersensitivity of cells lacking Ppz1 to oxidative damage establishes that potential Ppz1 inhibitors may synergize with oxidizing agents in prospective anti-fungal combination therapies.
Highlights
Candida albicans is an innocuous yeast species present in the micro biome of more than half of healthy adults [1]
Upregulation of genes involved in oxidative processes, enhanced activity of several oxidative enzymes, an elevated ratio of oxidized to reduced glutathione and an increase in reactive oxygen species (ROS) were observed in the phosphatase deletion mutant C. albicans implying that an oxidative stress response was primed [17,22]
Two strains of Candida albicans were applied in the experiments: the control QMY23 (WT) with the genotype his1Δ/his1Δ, leu2Δ:C. dublin iensis HIS1/leu2Δ:C. maltose LEU2, URA3/ura3Δ:imm434, IRO1/iro1Δ: imm434 [35] and the protein phosphatase-knockout (KO) with the ge notype ura3Δ-iro1Δ:imm434/URA3-IRO1, his1Δ/his1Δ, leu2Δ/leu2Δ, ppz1Δ:C. dubliniensis HIS1/ppz1Δ:C. maltosa LEU2 [16]
Summary
Candida albicans is an innocuous yeast species present in the micro biome of more than half of healthy adults [1]. Many currently available anti-fungal drugs affect the yeast cell membrane, since its unique sterol component, ergosterol, presents an ideal target [4]. Increases [3,11], there is a pressing need for new drug targets Protein phosphatases present such a possible target due to their diversity stemming from convergent evolution [12]. Upregulation of genes involved in oxidative processes, enhanced activity of several oxidative enzymes, an elevated ratio of oxidized to reduced glutathione and an increase in reactive oxygen species (ROS) were observed in the phosphatase deletion mutant C. albicans implying that an oxidative stress response was primed [17,22]. TBOOH (i) modifies membrane lipid composition [30,31]; (ii) increases ROS concentration [30]; (iii) induces the antioxidative defense system [32,33,34]; and (iv) stimulates cyanide-sensitive respiration in fungi [33]
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