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Identification and Mode of Action of a Plant Natural Product Targeting Human Fungal Pathogens

Dorsaz, Stephane and Snäka, Tiia and Favre-Godal, Quentin and Maudens, Pierre and Boulens, Nathalie and Furrer, Pascal and Nejad Ebrahimi, Samad Nejad and Hamburger, Matthias and Allémann, Eric and Gindro, Katia and Ferreira Queiroz, Emerson and Riezman, Howard and Wolfender, Jean-Luc and Sanglard, Dominique. (2017) Identification and Mode of Action of a Plant Natural Product Targeting Human Fungal Pathogens. Antimicrobial Agents and Chemotherapy, 61 (9). e00829-1.

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Abstract

Candida albicans is a major cause of fungal diseases in humans, and its resistance to available drugs is of concern. In an attempt to identify novel antifungal agents, we initiated a small-scale screening of a library of 199 natural plant compounds (i.e., natural products [NPs]). In vitro susceptibility profiling experiments identified 33 NPs with activity against C. albicans (MIC50s ≤ 32 μg/ml). Among the selected NPs, the sterol alkaloid tomatidine was further investigated. Tomatidine originates from the tomato (Solanum lycopersicum) and exhibited high levels of fungistatic activity against Candida species (MIC50s ≤ 1 μg/ml) but no cytotoxicity against mammalian cells. Genome-wide transcriptional analysis of tomatidine-treated C. albicans cells revealed a major alteration (upregulation) in the expression of ergosterol genes, suggesting that the ergosterol pathway is targeted by this NP. Consistent with this transcriptional response, analysis of the sterol content of tomatidine-treated cells showed not only inhibition of Erg6 (C-24 sterol methyltransferase) activity but also of Erg4 (C-24 sterol reductase) activity. A forward genetic approach in Saccharomyces cerevisiae coupled with whole-genome sequencing identified 2 nonsynonymous mutations in ERG6 (amino acids D249G and G132D) responsible for tomatidine resistance. Our results therefore unambiguously identified Erg6, a C-24 sterol methyltransferase absent in mammals, to be the main direct target of tomatidine. We tested the in vivo efficacy of tomatidine in a mouse model of C. albicans systemic infection. Treatment with a nanocrystal pharmacological formulation successfully decreased the fungal burden in infected kidneys compared to the fungal burden achieved by the use of placebo and thus confirmed the potential of tomatidine as a therapeutic agent.
Faculties and Departments:05 Faculty of Science > Departement Pharmazeutische Wissenschaften > Pharmazie > Pharmazeutische Biologie (Hamburger)
UniBasel Contributors:Hamburger, Matthias
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society for Microbiology
ISSN:0066-4804
e-ISSN:1098-6596
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:09 May 2018 07:04
Deposited On:09 May 2018 07:04

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