A yeast-based drug discovery platform to identify Plasmodium falciparum type II NADH dehydrogenase inhibitors.

Conventional methods utilizing in vitro protein activity assay or in vivo parasite survival to screen for malaria inhibitors suffer from high experimental background and/or inconvenience. Here we introduce a yeast-based system to facilitate chemical screen for specific protein or pathway inhibitors. The platform comprises several isogeneic Pichia strains that only differ in the target of interest, so that a compound which inhibits one strain but not the other is implicated in working specifically against the target. We used Plasmodium falciparum NDH2(PfNDH2), a type II NADH dehydrogenase, as a proof of principle to show how well this works. Three isogenic Pichia strains harboring respectively exogeneously introduced PfNDH2, its own complex I (a type I NADH dehydrogenase), and PfNDH2 with its own complex I were constructed. In a pilot screen of more than2000 compounds, we identified a highly specific inhibitor that acts on PfNDH2. This compound poorly inhibit the parasites at the asexual blood stage, however, is highly effective in repressing oocyst maturation in the mosquito stage. Our results demonstrate that the yeast cell based screen platform is feasible, efficient, economical and with very low background noise. Similar strategies could be extended to the functional screen for interacting molecules of other targets.