Candida albicans(C. albicans) biofilms exhibit enhanced resistance to conventional antifungal agents; however, the underlying pathogenic mechanisms warrant deeper exploration. Protein phosphatase 2A (PP2A), especially its catalytic activity, is crucial for maintaining physiological balance. This study focused on the role of the PP2A catalytic subunit coding genePPH21in biofilm formation and drug resistance ofC. albicans. The mutant strain (pph21Δ/Δ) was generated and identified. The oxidative stress was detected by the reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). The autophagic activity was evaluated, and the autophagosomes were observed by transmission electron microscopy (TEM). The biofilm formation was measured by XTT reduction assay, crystal violet (CV) staining, and scanning electron microscopy (SEM). The susceptibility to antifungal agents was examined by XTT reduction assay and spot assay. Additionally, the antioxidant N-acetylcysteine (NAC) was applied to clarify the regulatory effect ofC. albicansautophagy on oxidative stress. The pathogenicity ofPPH21in oralC. albicansinfection was evaluated through in vivo experiments. We found thatPPH21deletion led to increased oxidative stress and autophagic activities, but it can be reversed by the application of NAC. Moreover,PPH21deletion also impaired the biofilm formation ability and reduced resistance to antifungal agents. Our findings revealed thatPPH21is involved in both virulence and stress adaptation ofC. albicans.
Objectives Candida albicans ( C. albicans ) biofilms are well-known to be resistantto various antifungal agents. Autophagy is crucial for adapting to changes in nutrition conditions. Protein phosphatase 2A (PP2A) is prominent in regulating physiological processes, possibly related to autophagy-related (ATG) protein phosphorylation. This study hypothesizes that PP2A affects biofilm formation and drug resistance of C. albicans via autophagy induction. Materials and methods The expressions of PP2A catalytic subunit coding gene PPH21 were compared. The mutant strain ( pph21 Δ/Δ) was constructed and the biofilm was treated with autophagy activator (rapamycin, Rap). The biofilm formation, drug susceptibility and oxidative stress levels were examined. The autophagic activity was detected, along with the autophagosomes observed. The therapeutic efficacy of the antifungal agents was estimated on the mice model of C. albicans oral infection. Results PPH21 was associated with C. albicans biofilm formation and drug resistance. Autophagy activation by rapamycin can induce increased autophagy levels, while it was hindered in pph21 Δ/Δ. Besides, the protein levels of Atg13 and Atg1 were significantly down-regulated in pph21 Δ/Δ+Rap ( P < .01), along with its decreased regulatory capacity to oxidative stress. Autophagy activation can promote biofilm formation and improve drug resistance, while the absence of PPH21 may prevent the enhancement of drug resistance. Autophagy activation reduced the efficacy of antifungal agents in treating oral C. albicans infection in mice, among which pph21 Δ/Δ presented better therapeutic effects. Conclusion PP2A is important in the autophagy induction of C. albicans by participating in Atg13 phosphorylation, followed by Atg1 activation, further affecting its biofilm formation and drug resistance. Clinical relevance PP2A-induced autophagy may be a potential regulatory mechanism of C. albicans drug resistance. This appears to be a promising therapeutic strategy for managing C. albicans -related infectious diseases.
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