Fluconazole-induced actin cytoskeleton remodeling requires phosphatidylinositol 3-phosphate 5-kinase in the pathogenic yeast Candida glabrata

Known azole antifungal resistance mechanisms include mitochondrial dysfunction and overexpression of the sterol biosynthetic target enzyme and multidrug efflux pumps. Here, we identify, through a genetic screen, the vacuolar membrane-resident phosphatidylinositol 3-phosphate 5-kinase (CgFab1) to be a novel determinant of azole tolerance. We demonstrate for the first time that fluconazole promotes actin cytoskeleton reorganization in the emerging, inherently less azole-susceptible fungal pathogen Candida glabrata, and genetic or chemical perturbation of actin structures results in intracellular sterol accumulation and azole susceptibility. Further, CgFAB1 disruption impaired vacuole homeostasis and actin organization, and the F-actin-stabilizing compound jasplakinolide rescued azole toxicity in cytoskeleton defective-mutants including the Cgfab1 Delta mutant. In vitro assays revealed that the actin depolymerization factor CgCof1 binds to multiple lipids including phosphatidylinositol 3,5-bisphosphate. Consistently, CgCof1 distribution along with the actin filament-capping protein CgCap2 was altered upon both CgFAB1 disruption and fluconazole exposure. Altogether, these data implicate CgFab1 in azole tolerance through actin network remodeling. Finally, we also show that actin polymerization inhibition rendered fluconazole fully and partially fungicidal in azole-susceptible and azole-resistant C. glabrata clinical isolates, respectively, thereby, underscoring the role of fluconazole-effectuated actin remodeling in azole resistance.