title: Candida glabrata erg1 mutant with increased sensitivity to azoles and to low oxygen tension.
abstract: A Candida glabrata erg1 (Cgerg1) mutant, CgTn201S, was identified by transposon mutagenesis and by increased fluconazole susceptibility. CgERG1 encodes a 489-amino-acid protein which, on the basis of its homology with Saccharomyces cerevisiae ERG1, is a squalene epoxidase essential for ergosterol synthesis. Interruption following codon 475 of CgErg1p decreased the ergosterol content by 50%; caused accumulation of the squalene precursor; increased the levels of susceptibility to fluconazole, itraconazole, and terbinafine; increased the level of resistance to amphotericin B; increased the levels of rhodamine 6G and [(3)H]-fluconazole uptake; reduced the level of growth; and blocked growth under conditions of low oxygen tension. In addition, CgTn201S efficiently took up exogenous cholesterol from cholesterol-containing serum. Cholesterol constituted 34% of the extractable sterols in CgTn201S when it was grown aerobically on serum-containing medium. Under the same conditions, C. albicans contained only 0.1 to 1.2% cholesterol. Exogenous sterols also restored growth under conditions of low oxygen tension. Finally, complementation of the Cgerg1 mutation restored the levels of [(3)H]fluconazole uptake and drug susceptibility to wild-type levels.
authors.affiliation: Clinical Mycology Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Clinical Center NIH, Bethesda, MD 20892, USA.
authors.forename: Huei-Fung
authors.initials: HF
authors.lastname: Tsai
authors.forename: Martin
authors.initials: M
authors.lastname: Bard
authors.forename: Koichi
authors.initials: K
authors.lastname: Izumikawa
authors.forename: Anna A
authors.initials: AA
authors.lastname: Krol
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Sturm
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Culbertson
authors.forename: Charles A
authors.initials: CA
authors.lastname: Pierson
authors.forename: John E
authors.initials: JE
authors.lastname: Bennett
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology*; D001393:Azoles / Q000378:metabolism / Q000494:pharmacology*; D041221:Candida glabrata / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D025141:Drug Resistance, Fungal; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D015725:Fluconazole / Q000378:metabolism / Q000494:pharmacology; D005456:Fluorescent Dyes; D005816:Genetic Complementation Test; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics*; D010100:Oxygen / Q000494:pharmacology*; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D015221:Potassium Channels / Q000235:genetics*; D024642:Potassium Channels, Voltage-Gated; D012235:Rhodamines; D013185:Squalene / Q000378:metabolism; D013261:Sterols / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D001393:Azoles; D004251:DNA Transposable Elements; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D005456:Fluorescent Dyes; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012235:Rhodamines; D013261:Sterols; C026188:rhodamine 6G; D013185:Squalene; D015725:Fluconazole; D002784:Cholesterol; D010100:Oxygen