A live-cell ergosterol reporter for visualization of the effects of fluconazole on the human fungal pathogen Candida albicans

Ergosterol, an essential plasma membrane amphipathic lipid, is a major component of the fungal plasma membrane. Most fungal pathogens are susceptible to azole drugs that target ergosterol biosynthesis, and resistance/tolerance to azoles is increasingly problematic. Candida albicans is the most prevalent etiology of candidiasis, and, in this fungal pathogen, ergosterol-rich sub-domains are likely to include sphingolipids, as well as specific membrane proteins, such as multidrug transporters. To investigate the dynamics of ergosterol during the cell cycle and whether drug treatment affects these dynamics in this opportunistic pathogen, we adapted the D4H (domain 4 of the perfringolysin O bacterial toxin) reporter for studying sterol-rich membrane domains. We show that D4H provides a direct readout for the cellular effects of fluconazole and that highly polarized ergosterol is not critical for budding or filamentous growth.