Mitochondrial targeting of Candida albicans SPFH proteins and requirement of stomatins for SDS-induced stress tolerance

ABSTRACT The SPFH (stomatin, prohibitin, flotillin, and HflK/HflC) protein superfamily is conserved across all domains of life. Fungal SPFH proteins are required for respiration, stress adaptation, and membrane scaffolding. In the yeast Candida albicans, stomatin-like protein 3 (Slp3) forms punctate foci at the plasma membrane, and SLP3 overexpression causes cell death following exposure to the surfactant, SDS, and the oxidative stressor, H2O2. Here, we sought to determine the cellular localization and functionally characterize stomatin-like protein 2 (Slp2), prohibitin-1 (Phb1), prohibitin-2 (Phb2), and prohibitin-12 (Phb12) in C. albicans. Cytological and western blotting results showed that Slp2-Gfp/Rfp and prohibitin-Gfp fusion proteins localize to the mitochondrion in yeast cells. Growth assay results did not identify any respiration defects in a panel of stomatin and prohibitin mutant strains, suggesting that SPFH respiratory function has diverged in C. albicans from other model eukaryotes. However, a slp2Δ/Δ/slp3Δ/Δ double mutant strain grew poorly in the presence of 0.08% SDS, accumulated intracellular reactive oxidative species, and displayed aberrant ergosterol distribution in the plasma membrane. These phenotypes were not observed in slp2Δ/Δ or slp3Δ/Δ single mutants, indicating a possible indirect genetic interaction between SLP2 and SLP3. In addition, slp2Δ/Δ and slp2Δ/Δ/slp3Δ/Δ mutant strains were slightly resistant to the antifungal drug, fluconazole. Collectively, these findings reveal the cellular localization of Slp2, Phb1, Phb2, and Phb12, highlight the significance of stomatins in C. albicans SDS stress tolerance, and, for the first time, associate stomatins with antifungal resistance.IMPORTANCEStomatins and prohibitins coordinate respiration and stress adaptation in fungi. Invasive mycoses caused by Candida albicans are a significant cause of morbidity, and candidemia patients show high mortality rates worldwide. Mitochondria are essential for C. albicans commensalism and virulence, and mitochondrial proteins are targets for antifungal interventions. C. albicans encodes five SPFH proteins: two stomatin-like proteins and three prohibitins. We have previously shown that Slp3 is important for C. albicans adaptation to various types of environmental stress. Moreover, synthetic compounds that bind to mammalian prohibitins inhibit C. albicans filamentation and are fungicidal. However, there is limited information available regarding the remaining SPFH proteins. Our findings show that mitochondrial localization of SPFH proteins is conserved in C. albicans. In addition, we demonstrate the importance of stomatins in plasma membrane and mitochondrial stress tolerance.