title: Molecular basis for fungicidal action of neothyonidioside, a triterpene glycoside from the sea cucumber, Australostichopus mollis.
abstract: Neothyonidioside is a triterpene glycoside (TG) isolated from the sea cucumber, Australostichopus mollis, that is potently cytotoxic to S. cerevisiae, but does not permeabilize cellular membranes. We mutagenized S. cerevisiae and isolated a neothionidioside-resistant (neo(R)) strain. Using synthetic genetic array mapping and sequencing, we identified NCP1 as the resistance locus. Quantitative HPLC revealed that neo(R)/ncp1 mutants have reduced ergosterol content. Ergosterol added to growth media reversed toxicity, demonstrating that neothionidioside binds directly to ergosterol, similar to the polyene natamycin. Ergosterol synthesis inhibitors ketoconazole and atorvastatin conferred resistance to neothionidioside in a dose-dependent manner showing that a threshold ergosterol concentration is required for toxicity. A genome-wide screen of deletion mutants against neothionidioside revealed hypersensitivity of many of the component genes in the ESCRT complexes relating to multivesicular body formation. Confocal microscopy of cells stained with a vital dye showed blockage at this step. Thus, we propose neothionidioside may affect membrane curvature and fusion capability in the endosome-vacuole pathway.
authors.affiliation: Victoria University of Wellington, Kelburn Parade, Kelburn, Wellington, New Zealand.
authors.forename: Ploi
authors.initials: P
authors.lastname: Yibmantasiri
authors.forename: Dora C
authors.initials: DC
authors.lastname: Leahy
authors.forename: Bede P
authors.initials: BP
authors.lastname: Busby
authors.forename: Stephan Andreas
authors.initials: SA
authors.lastname: Angermayr
authors.forename: Alice G
authors.initials: AG
authors.lastname: Sorgo
authors.forename: Kristina
authors.initials: K
authors.lastname: Boeger
authors.forename: Rosemary
authors.initials: R
authors.lastname: Heathcott
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Barber
authors.forename: Greta
authors.initials: G
authors.lastname: Moraes
authors.forename: James H
authors.initials: JH
authors.lastname: Matthews
authors.forename: Peter T
authors.initials: PT
authors.lastname: Northcote
authors.forename: Paul H
authors.initials: PH
authors.lastname: Atkinson
authors.forename: David S
authors.initials: DS
authors.lastname: Bellows
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D025141:Drug Resistance, Fungal / Q000235:genetics; D004875:Ergosterol / Q000378:metabolism / Q000494:pharmacology; D006027:Glycosides / Q000494:pharmacology*; D018613:Microscopy, Confocal; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012616:Sea Cucumbers / Q000737:chemistry / Q000378:metabolism*; D014315:Triterpenes / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D006027:Glycosides; D029701:Saccharomyces cerevisiae Proteins; D014315:Triterpenes; C573010:neothyonidioside; D004875:Ergosterol