title: The haploinsufficiency profile of α-hederin suggests a caspofungin-like antifungal mode of action.
abstract: The leaves of common ivy (Hedera helix) contain the cytotoxic saponin α-hederin, which is inhibitory to Candida albicans at low concentrations. To investigate the mode of action of α-hederin, a haploinsufficiency screen was carried out using a library of 1152 Saccharomyces cerevisiae deletion strains. An ethanol ivy extract containing α-hederin was used in the initial screen to reduce the amount of compound required. Strains exhibiting disproportionately low growth were then examined in more detail by comparing growth curves in the presence and absence of α-hederin. This approach identified three hypersensitive strains carrying gene deletions for components of the transcription related proteins SWI/SNF, RNA polymerase II and the RSC complex. Saponin cytotoxicity is often attributed to membrane damage, however α-hederin did not induce hypersensitivity with an aminophospholipid translocase deletion strain that is frequently hypersensitive to membrane damaging agents. The haploinsufficiency profile of α-hederin is most similar to that reported for drugs such as caspofungin that inhibit synthesis of the fungal cell wall. Screening with plant extracts rather than isolated compounds, provides a valuable shortcut in haploinsufficiency screening provided hypersensitive strains are then confirmed as such using purified active principles.
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK. Electronic address: t.prescott@kew.org.
authors.forename: Thomas A K
authors.initials: TA
authors.lastname: Prescott
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Luke P
authors.initials: LP
authors.lastname: Rigby
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Veitch
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Monique S J
authors.initials: MS
authors.lastname: Simmonds
mesh_terms: D000935:Antifungal Agents / Q000302:isolation & purification / Q000494:pharmacology*; D000077336:Caspofungin; D054714:Echinocandins / Q000494:pharmacology*; D017353:Gene Deletion; D057895:Haploinsufficiency / Q000235:genetics; D035981:Hedera / Q000737:chemistry*; D055666:Lipopeptides; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics; D012503:Saponins / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D010936:Plant Extracts; D012503:Saponins; C010177:beta-hederin; D009828:Oleanolic Acid; D000077336:Caspofungin
keywords: Caspofungin; Haploinsufficiency screen; Hedera helix; Ivy; Mode of action; SWI/SNF; Yeast deletion; α-Hederin