E1210, a New Broad-Spectrum Antifungal, Suppresses Candida albicans Hyphal Growth through Inhibition of Glycosylphosphatidylinositol Biosynthesis

Abstract

ABSTRACTContinued research toward the development of new antifungals that act via inhibition of glycosylphosphatidylinositol (GPI) biosynthesis led to the design of E1210. In this study, we assessed the selectivity of the inhibitory activity of E1210 againstCandida albicansGWT1(Orf19.6884) protein,Aspergillus fumigatusGWT1(AFUA_1G14870) protein, and humanPIG-Wprotein, which can catalyze the inositol acylation of GPI early in the GPI biosynthesis pathway, and then we assessed the effects of E1210 on keyC. albicansvirulence factors. E1210 inhibited the inositol acylation activity ofC. albicansGwt1p andA. fumigatusGwt1p with 50% inhibitory concentrations (IC50s) of 0.3 to 0.6 μM but had no inhibitory activity against human Pig-Wp even at concentrations as high as 100 μM. To confirm the inhibition of fungal GPI biosynthesis, expression ofALS1protein, a GPI-anchored protein, on the surfaces ofC. albicanscells treated with E1210 was studied and shown to be significantly lower than that on untreated cells. However, theALS1protein levels in the crude extract and theRHO1protein levels on the cell surface were found to be almost the same. Furthermore, E1210 inhibited germ tube formation, adherence to polystyrene surfaces, and biofilm formation ofC. albicansat concentrations above its MIC. These results suggested that E1210 selectively inhibited inositol acylation of fungus-specific GPI which would be catalyzed by Gwt1p, leading to the inhibition of GPI-anchored protein maturation, and also that E1210 suppressed the expression of some important virulence factors ofC. albicans, through its GPI biosynthesis inhibition.