The heme A synthase Cox15, as a target of redox-active 3-benzylmenadiones with antiparasitic activity.

Chagas disease, caused by Trypanosoma cruzi, is a neglected parasitic infection. The very limited arsenal of anti-T. cruzi treatments calls for the development of new drugs. Recently, a library of 3-benzylmenadione derivatives was synthesized, with cruzidione being the most efficient and specific compound against the parasite. To decipher its mode of action, we used the yeast Saccharomyces cerevisiae as a model. Evidence pinpointed at the heme A synthase Cox15 as a primary target of cruzidione: (i) a mutation in Cox15 (i.e., S429F) renders the yeast cells highly sensitive to the drug, (ii) treatment with cruzidione led to the loss of cytochrome c oxidase, an enzyme that relies on heme A as an essential cofactor, and (iii) replacement of the yeast Cox15 by T. cruzi enzyme resulted in a high sensitivity to cruzidione. We then investigated the effect of cruzidione in T. cruzi and observed a significant reduction in the heme contents, most likely involving the inhibition of the heme A synthase. This, in turn, led to a decrease in O2 consumption by the parasite. Finally, using the yeast model, we showed that, similar to what we previously found for the antimalarial benzylmenadione plasmodione, NADH-dehydrogenase plays a key role in cruzidione bioactivation. We proposed that the reduced benzoylmenadione metabolites, produced by the reaction with NADH-dehydrogenase, act as Cox15 inhibitors. This study, through the identification of the mode of action of cruzidione, highlighted Cox15 as a novel target for antiparasitic drugs.