title: Sterol biosynthesis is required for heat resistance but not extracellular survival in leishmania.
abstract: Sterol biosynthesis is a crucial pathway in eukaryotes leading to the production of cholesterol in animals and various C24-alkyl sterols (ergostane-based sterols) in fungi, plants, and trypanosomatid protozoa. Sterols are important membrane components and precursors for the synthesis of powerful bioactive molecules, including steroid hormones in mammals. Their functions in pathogenic protozoa are not well characterized, which limits the development of sterol synthesis inhibitors as drugs. Here we investigated the role of sterol C14α-demethylase (C14DM) in Leishmania parasites. C14DM is a cytochrome P450 enzyme and the primary target of azole drugs. In Leishmania, genetic or chemical inactivation of C14DM led to a complete loss of ergostane-based sterols and accumulation of 14-methylated sterols. Despite the drastic change in lipid composition, C14DM-null mutants (c14dm(-)) were surprisingly viable and replicative in culture. They did exhibit remarkable defects including increased membrane fluidity, failure to maintain detergent resistant membrane fraction, and hypersensitivity to heat stress. These c14dm(-) mutants showed severely reduced virulence in mice but were highly resistant to itraconazole and amphotericin B, two drugs targeting sterol synthesis. Our findings suggest that the accumulation of toxic sterol intermediates in c14dm(-) causes strong membrane perturbation and significant vulnerability to stress. The new knowledge may help improve the efficacy of current drugs against pathogenic protozoa by exploiting the fitness loss associated with drug resistance.
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, Texas, United States of America.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, Saint Louis, Missouri, United States of America.
authors.forename: Fong-Fu
authors.initials: FF
authors.lastname: Hsu
authors.affiliation: Department of Physics, Texas Tech University, Lubbock, Texas, United States of America.
authors.forename: Eda
authors.initials: E
authors.lastname: Baykal
authors.affiliation: Department of Physics, Texas Tech University, Lubbock, Texas, United States of America.
authors.forename: Juyang
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, Texas, United States of America.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003902:Detergents / Q000494:pharmacology; D004875:Ergosterol / Q000031:analogs & derivatives / Q000378:metabolism; D056890:Eukaryota / Q000378:metabolism*; D005110:Extracellular Space; D005260:Female; D006358:Hot Temperature; D006967:Hypersensitivity / Q000378:metabolism / Q000382:microbiology; D007891:Leishmania / Q000378:metabolism*; D008807:Mice, Inbred BALB C; D013261:Sterols / Q000096:biosynthesis*; D014774:Virulence / Q000502:physiology
chemical_list: D003902:Detergents; D013261:Sterols; C015190:ergostane; D004875:Ergosterol