title: Erg4A and Erg4B Are Required for Conidiation and Azole Resistance via Regulation of Ergosterol Biosynthesis in Aspergillus fumigatus.
abstract: Ergosterol, a fungus-specific sterol enriched in cell plasma membranes, is an effective antifungal drug target. However, current knowledge of the ergosterol biosynthesis process in the saprophytic human fungal pathogen Aspergillus fumigatus remains limited. In this study, we found that two endoplasmic reticulum-localized sterol C-24 reductases encoded by both erg4A and erg4B homologs are required to catalyze the reaction during the final step of ergosterol biosynthesis. Loss of one homolog of Erg4 induces the overexpression of the other one, accompanied by almost normal ergosterol synthesis and wild-type colony growth. However, double deletions of erg4A and erg4B completely block the last step of ergosterol synthesis, resulting in the accumulation of ergosta-5,7,22,24(28)-tetraenol, a precursor compound of ergosterol. Further studies indicate that erg4A and erg4B are required for conidiation but not for hyphal growth. Importantly, the Δerg4A Δerg4B mutant still demonstrates wild-type virulence in a compromised mouse model but displays remarkable increased susceptibility to antifungal azoles. Our data suggest that inhibitors of Erg4A and Erg4B may serve as effective candidates for adjunct antifungal agents with azoles.
  
  
  
  Knowledge of the ergosterol biosynthesis pathway in the human opportunistic pathogen A. fumigatus is useful for designing and finding new antifungal drugs. In this study, we demonstrated that the endoplasmic reticulum-localized sterol C-24 reductases Erg4A and Erg4B are required for conidiation via regulation of ergosterol biosynthesis. Moreover, inactivation of both Erg4A and Erg4B results in hypersensitivity to the clinical guideline-recommended antifungal drugs itraconazole and voriconazole. Therefore, our finding indicates that inhibition of Erg4A and Erg4B might be an effective approach for alleviating A. fumigatus infection.
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, China.
authors.forename: Nanbiao
authors.initials: N
authors.lastname: Long
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, China.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Dermatology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China.
authors.forename: Qiuqiong
authors.initials: Q
authors.lastname: Zeng
authors.affiliation: Department of Dermatology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Sang
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, China linglu@njnu.edu.cn.
authors.forename: Ling
authors.initials: L
authors.lastname: Lu
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D001228:Aspergillosis / Q000188:drug therapy / Q000382:microbiology; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D025141:Drug Resistance, Fungal / Q000235:genetics*; D004875:Ergosterol / Q000096:biosynthesis*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D006801:Humans; D017964:Itraconazole / Q000494:pharmacology*; D051379:Mice; D008826:Microbial Sensitivity Tests; D010088:Oxidoreductases / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development*; D065819:Voriconazole / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D029701:Saccharomyces cerevisiae Proteins; D017964:Itraconazole; D010088:Oxidoreductases; C070590:ERG4 protein, S cerevisiae; D065819:Voriconazole; D004875:Ergosterol
keywords: Aspergillus fumigatus; azoles; ergosterol biosynthesis; sterol C-24 reductase