Changes in Ergosterol Biosynthesis Alter the Response to Cycloheximide, 4-Nitroquinoline-N-Oxide, Weak Organic Acids, and Virulence in Candida glabrata.

The ERG6 gene encodes the sterol C24-methyltransferase converting zymosterol to fecosterol in the ergosterol biosynthetic pathway. Here, we extend the results of functional analysis of the CgERG6 gene, which was previously shown to modulate drug susceptibility in Candida glabrata mutant cells, by demonstrating that its deletion leads to increased susceptibility to cycloheximide, 4-nitroquinoline-N-oxide and weak organic acids, and such effects are associated with attenuated virulence. Together with abrogated efflux of drug substrates by CgCdr1p and CgPdr12p, the Cgerg6Δ mutation leads to reduced cell surface hydrophobicity and decreased virulence of the mutant cells of C. glabrata. The absence of CgErg6p impacts the lipid organization and function of the plasma membrane, resulting in non-specific permeability and abrogation of normal function of membrane-bound proteins accompanied by decreased virulence in Cgerg6Δ cells. Galleria mellonella larvae were used as a non-vertebrate animal host model to determine differences in the virulence potential of C. glabrata strains (parental strain and the Cgerg6Δ deletion mutant). We found that Cgerg6Δ mutant strain attenuated in virulence caused 25-30% survival of larvae compared with parental strain.