Multiple unbiased approaches identify oxidosqualene cyclase as the molecular target of a promising anti-leishmanial.

Luciana S Paradela, Richard J Wall, Sandra Carvalho, Giulia Chemi, Victoriano Corpas-Lopez, Eoin Moynihan, Davide Bello, Stephen Patterson, Maria Lucia S Güther, Alan H Fairlamb, Michael A J Ferguson, Fabio Zuccotto, Julio Martin*, Ian H Gilbert, Susan Wyllie.

*Global Health R&D, GlaxoSmithKline, Tres Cantos 28760, Spain.

Cell Chem Biol. 2021 Feb 26:S2451-9456(21)00093-3. doi: 10.1016/j.chembiol.2021.02.008. Epub ahead of print. PMID: 33691122

Abstract
Phenotypic screening identified a benzothiophene compound with activity against Leishmania donovani, the causative agent of visceral leishmaniasis. Using multiple orthogonal approaches, oxidosqualene cyclase (OSC), a key enzyme of sterol biosynthesis, was identified as the target of this racemic compound and its enantiomers. Whole genome sequencing and screening of a genome-wide overexpression library confirmed that OSC gene amplification is associated with resistance to compound 1. Introduction of an ectopic copy of the OSC gene into wild-type cells reduced susceptibility to these compounds confirming the role of this enzyme in resistance. Biochemical analyses demonstrated the accumulation of the substrate of OSC and depletion of its product in compound (S)-1-treated-promastigotes and cell-free membrane preparations, respectively. Thermal proteome profiling confirmed that compound (S)-1 binds directly to OSC. Finally, modeling and docking studies identified key interactions between compound (S)-1 and the LdOSC active site. Strategies to improve the potency for this promising anti-leishmanial are proposed.