Global Transcriptome Profile of Cryptococcus neoformans during Exposure to Hydrogen Peroxide Induced Oxidative Stress

Abstract

The ability of the opportunistic fungal pathogen Cryptococcus neoformans to resist oxidative stress is one of its most important virulence related traits. To cope with the deleterious effect of cellular damage caused by the oxidative burst inside the macrophages, C. neoformans has developed multilayered redundant molecular responses to neutralize the stress, to repair the damage and to eventually grow inside the hostile environment of the phagosome. We used microarray analysis of cells treated with hydrogen peroxide (H2O2) at multiple time points in a nutrient defined medium to identify a transcriptional signature associated with oxidative stress. We discovered that the composition of the medium in which fungal cells were grown and treated had a profound effect on their capacity to degrade exogenous H2O2. We determined the kinetics of H2O2 breakdown by growing yeast cells under different conditions and accordingly selected an appropriate media composition and range of time points for isolating RNA for hybridization. Microarray analysis revealed a robust transient transcriptional response and the intensity of the global response was consistent with the kinetics of H2O2 breakdown by treated cells. Gene ontology analysis of differentially expressed genes related to oxidation-reduction, metabolic process and protein catabolic processes identified potential roles of mitochondrial function and protein ubiquitination in oxidative stress resistance. Interestingly, the metabolic pathway adaptation of C. neoformans to H2O2 treatment was remarkably distinct from the response of other fungal organisms to oxidative stress. We also identified the induction of an antifungal drug resistance response upon the treatment of C. neoformans with H2O2. These results highlight the complexity of the oxidative stress response and offer possible new avenues for improving our understanding of mechanisms of oxidative stress resistance in C. neoformans.

The Cch1-Mid1 High-Affinity Calcium Channel Contributes to the Virulence of Cryptococcus neoformans by Mitigating Oxidative Stress

“…2A, the cch1⌬ mid1⌬ double mutant was as defective as the cch1⌬ strains in the presence of FCCP. This result was consistent with the protective role of Cch1 during oxidative stress, since mitochondrial functions are important for oxidative stress resistance in C. neoformans (26). A likely scenario for the resistance of the cch1⌬ mid1⌬ strain to oxidative stress would be the existence of a compensatory mechanism that is activated in the absence of both Mid1 and Cch1 under H 2 O 2 and paraquat stress but not with FCCP.…”

“…Next we sought to resolve the physiological implication of the Mid1-Ccp1 genetic interaction. In C. neoformans, cytochrome c peroxidase (Ccp1) is known to protect against external oxidative stressinducing agents (25,26). It has been shown that treating cells with antimycin A inhibits the cytochrome c pathway and leads to the production of free radicals (26).…”

Rewiring of Signaling Networks Modulating Thermotolerance in the Human Pathogen Cryptococcus neoformans

“…Notably, the expression of SRX1, which encodes a sulfiredoxin, was downregulated by HSF1 overexpression (Table S11). We recently showed that SRX1 is rapidly induced by peroxide stress and required for the recycling of peroxiredoxin (Tsa1) and oxidative stress response and adaptation (Upadhya et al 2013a). The qRT-PCR analysis confirmed that basal SRX1 expression levels were reduced by HSF1 overexpression ( Figure 7A).…”

ALL2 , a Homologue of ALL1 , Has a Distinct Role in Regulating pH Homeostasis in the Pathogen Cryptococcus neoformans

“…Iron catalyzes the generation of hydroxyl radicals from oxidant precursors, such as superoxide anions and hydrogen peroxide (40). Gene ontology analysis of differentially expressed genes has shown that adaptation of C. neoformans to H 2 O 2 treatment is distinct from the response of other fungal organisms to oxidative stress (41). One reason for this is that C. neoformans is encapsulated and both the size and the biophysical properties of the exo-PS of C. neoformans affect its resistance to oxidative stress (13,17).…”