Arthrocolins Synergizing with Fluconazole Inhibit Fluconazole-Resistant Candida albicans by Increasing Riboflavin Metabolism and Causing Mitochondrial Dysfunction and Autophagy

Antifungal Activity, Synergism with Fluconazole or Amphotericin B and Potential Mechanism of Direct Current against Candida albicans Biofilms and Persisters

Candida albicans, as a notorious fungal pathogen, is associated with high morbidity and mortality worldwide due to its ability to form biofilms and persisters that can withstand currently available antifungals. Direct current (DC) has demonstrated a promising antimicrobial effect and synergistic effect with antimicrobials against various infections. Here, we first found DC exerted a killing effect on C. albicans planktonic and biofilm cells. Moreover, DC showed a synergistic effect with fluconazole (FLC) and amphotericin B (AMB). Notably, near-to-complete eradication of AMB-tolerant C. albicans biofilm persisters was achieved upon DC treatment. Next, the mechanism of action of DC was explored through mapping the genes and proteomic profiles of DC-treated C. albicans. The multi-omics analysis, quantitative real-time PCR and assay of reactive oxygen species (ROS) demonstrated DC exerted an antifungal effect on C. albicans by increasing cellular oxidative stress. As revealed by multiple analyses (e.g., protein assay based on absorbance at 280 nm and rhodamine 6G assay), DC was able to enhance membrane permeability, inhibit drug efflux and increase cellular FLC/AMB concentration of C. albicans, thereby mediating its synergism with the antifungals. Furthermore, DC inhibited superoxide dismutase 2 (SOD2) expression and manganese-containing SOD (Mn SOD) activity, leading to ROS production and enhanced killing of C. albicans biofilm persisters. The current findings demonstrate that the adjunctive use of DC in combination with antifungals is a promising strategy for effective control of C. albicans infections and management of antifungal resistance/tolerance in Candida biofilms.

AoRab7A interacts with AoVps35 and AoVps41 to regulate vacuole assembly, trap formation, conidiation, and functions of proteasomes and ribosomes in Arthrobotrys oligospora

Rab GTPases regulate vesicle trafficking in organisms and play crucial roles in growth and development. Arthrobotrys oligospora is a ubiquitous nematode-trapping (NT) fungus, it can form elaborate traps to capture nematodes. Our previous study found that deletion of Aorab7A abolished the trap formation and sporulation. Here, we investigated the regulatory mechanism of AoRab7A using transcriptomic, biochemical, and phenotypic comparisons. Transcriptome analysis, yeast library screening, and yeast two-hybrid assay identified two vacuolar protein sorting (Vps) proteins, AoVps41 and AoVps35, as putative targets of AoRab7A. The deletion of Aovps41 and Aovps35 caused considerable defects in multiple phenotypic traits, such as conidiation and trap formation. We further found a close connection between AoRab7A and Vps proteins in vesicle-vacuole fusion, which triggered vacuolar fragmentation. Further transcriptome analysis showed that AoRab7A and AoVps35 play essential roles in many cellular processes and components including proteasomes, autophagy, fatty acid degradation, and ribosomes in A. oligospora. Furthermore, we verified that AoRab7A, AoVps41, and AoVps35 are involved in ribosome and proteasome functions. The absence of these proteins inhibited the biosynthesis of nascent proteins and enhanced ubiquitination. Our findings suggest that AoRab7A interacts with AoVps41 and AoVps35 to mediate vacuolar fusion and influence lipid droplet accumulation, autophagy, and stress response. These proteins are especially required for the conidiation and trap development of A. oligospora.