title: UPC2 is universally essential for azole antifungal resistance in Candida albicans.
abstract: In Candida albicans, the transcription factor Upc2 is central to the regulation of ergosterol biosynthesis. UPC2-activating mutations contribute to azole resistance, whereas disruption increases azole susceptibility. In the present study, we investigated the relationship of UPC2 to fluconazole susceptibility, particularly in azole-resistant strains. In addition to the reduced fluconazole MIC previously observed with UPC2 disruption, we observed a lower minimum fungicidal concentration (MFC) for a upc2Δ/Δ mutant than for its azole-susceptible parent, SC5314. Moreover, the upc2Δ/Δ mutant was unable to grow on a solid medium containing 10 μg/ml fluconazole and exhibited increased susceptibility and a clear zone of inhibition by Etest. Time-kill analysis showed higher fungistatic activity against the upc2Δ/Δ mutant than against SC5314. UPC2 disruption in strains carrying specific resistance mutations also resulted in reduced MICs and MFCs. UPC2 disruption in a highly azole resistant clinical isolate containing multiple resistance mechanisms likewise resulted in a reduced MIC and MFC. This mutant was unable to grow on a solid medium containing 10 μg/ml fluconazole and exhibited increased susceptibility and a clear zone of inhibition by Etest. Time-kill analysis showed increased fungistatic activity against the upc2Δ/Δ mutant in the resistant background. Microarray analysis showed attenuated induction by fluconazole of genes involved in sterol biosynthesis, iron transport, or iron homeostasis in the absence of UPC2. Taken together, these data demonstrate that the UPC2 transcriptional network is universally essential for azole resistance in C. albicans and represents an attractive target for enhancing azole antifungal activity.
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Vasicek
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Berkow
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Flowers
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Katherine S
authors.initials: KS
authors.lastname: Barker
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA Department of Pediatrics, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA Children's Foundation Research Center at Le Bonheur Children's Medical Center, Memphis, Tennessee, USA progers3@uthsc.edu.
authors.forename: P David
authors.initials: PD
authors.lastname: Rogers
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects / Q000378:metabolism*; D025141:Drug Resistance, Fungal / Q000235:genetics*; D015725:Fluconazole / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000935:Antifungal Agents; D005656:Fungal Proteins; D014157:Transcription Factors; D015725:Fluconazole