title: A sterol-regulatory element binding protein is required for cell polarity, hypoxia adaptation, azole drug resistance, and virulence in Aspergillus fumigatus.
abstract: At the site of microbial infections, the significant influx of immune effector cells and the necrosis of tissue by the invading pathogen generate hypoxic microenvironments in which both the pathogen and host cells must survive. Currently, whether hypoxia adaptation is an important virulence attribute of opportunistic pathogenic molds is unknown. Here we report the characterization of a sterol-regulatory element binding protein, SrbA, in the opportunistic pathogenic mold, Aspergillus fumigatus. Loss of SrbA results in a mutant strain of the fungus that is incapable of growth in a hypoxic environment and consequently incapable of causing disease in two distinct murine models of invasive pulmonary aspergillosis (IPA). Transcriptional profiling revealed 87 genes that are affected by loss of SrbA function. Annotation of these genes implicated SrbA in maintaining sterol biosynthesis and hyphal morphology. Further examination of the SrbA null mutant consequently revealed that SrbA plays a critical role in ergosterol biosynthesis, resistance to the azole class of antifungal drugs, and in maintenance of cell polarity in A. fumigatus. Significantly, the SrbA null mutant was highly susceptible to fluconazole and voriconazole. Thus, these findings present a new function of SREBP proteins in filamentous fungi, and demonstrate for the first time that hypoxia adaptation is likely an important virulence attribute of pathogenic molds.
authors.affiliation: Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT, USA.
authors.forename: Sven D
authors.initials: SD
authors.lastname: Willger
authors.forename: Srisombat
authors.initials: S
authors.lastname: Puttikamonkul
authors.forename: Kwang-Hyung
authors.initials: KH
authors.lastname: Kim
authors.forename: James B
authors.initials: JB
authors.lastname: Burritt
authors.forename: Nora
authors.initials: N
authors.lastname: Grahl
authors.forename: Laurel J
authors.initials: LJ
authors.lastname: Metzler
authors.forename: Robert
authors.initials: R
authors.lastname: Barbuch
authors.forename: Martin
authors.initials: M
authors.lastname: Bard
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Lawrence
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cramer
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001232:Aspergillus fumigatus / Q000472:pathogenicity*; D001393:Azoles / Q000493:pharmacokinetics*; D016764:Cell Polarity; D004351:Drug Resistance; D005656:Fungal Proteins / Q000502:physiology; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D000860:Hypoxia; D051379:Mice; D008815:Mice, Inbred Strains; D051779:Sterol Regulatory Element Binding Proteins / Q000502:physiology*; D014158:Transcription, Genetic; D014774:Virulence
chemical_list: D001393:Azoles; D005656:Fungal Proteins; D051779:Sterol Regulatory Element Binding Proteins