Identification of Plasmodium falciparum Mitochondrial Malate: Quinone Oxidoreductase Inhibitors from the Pathogen Box.

Xinying Wang,Francisco Javier Gamo Benito,Endah Dwi Hartuti,Hiroyuki Saimoto,Shigeharu Harada,Kiyoshi Kita,Yoh-Ichi Watanabe,Yukiko Miyazaki,Tomoo Shiba,Tomoyoshi Nozaki,Jeremy Nicholas Burrows,Daniel Ken Inaoka

doi:10.3390/genes10060471

Abstract

Malaria is one of the three major global health threats. Drug development for malaria, especially for its most dangerous form caused by Plasmodium falciparum, remains an urgent task due to the emerging drug-resistant parasites. Exploration of novel antimalarial drug targets identified a trifunctional enzyme, malate quinone oxidoreductase (MQO), located in the mitochondrial inner membrane of P. falciparum (PfMQO). PfMQO is involved in the pathways of mitochondrial electron transport chain, tricarboxylic acid cycle, and fumarate cycle. Recent studies have shown that MQO is essential for P. falciparum survival in asexual stage and for the development of experiment cerebral malaria in the murine parasite P. berghei, providing genetic validation of MQO as a drug target. However, chemical validation of MQO, as a target, remains unexplored. In this study, we used active recombinant protein rPfMQO overexpressed in bacterial membrane fractions to screen a total of 400 compounds from the Pathogen Box, released by Medicines for Malaria Venture. The screening identified seven hit compounds targeting rPfMQO with an IC50 of under 5 μM. We tested the activity of hit compounds against the growth of 3D7 wildtype strain of P. falciparum, among which four compounds showed an IC50 from low to sub-micromolar concentrations, suggesting that PfMQO is indeed a potential antimalarial drug target.

Highlights

Malaria has been a constant threat and a tremendous burden to public health
The atovaquone-resistant parasite has been reported to carry mutations in the cytochrome b gene coded by the mitochondrial genome, we have shown that those mutant parasites cannot spread due to an inability to develop into an oocyst inside the mosquito [10,11] indicating that mitochondrial function is important to the viability and growth of Plasmodium parasites at all life cycle stages
We focused on 400 compounds from the Pathogen Box released by Medicines for Malaria Venture (MMV) to test their potency against both the recombinant

Summary

Introduction

Malaria has been a constant threat and a tremendous burden to public health. In spite of effort spent in the control of malaria, the disease still caused 219 million cases and 435,000 deaths in 2017, according to a recent report issued by the World Health Organization [1]. Development of a high-throughput screening system largely accelerates the steps of antimalarial drug discovery. Almost 30,000 compounds identified in these screenings were reported to selectively inhibit the growth of the cultured asexual blood stage (ABS) Plasmodium falciparum, providing excellent starting points for the discovery of new antimalarial drugs [3,4,5]. To overcome the increasing drug-resistance problem, exploration of new compounds against novel targets is of great importance. This relies on a good understanding of the parasite physiology of each life cycle stage at the molecular level [6]

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