Siccanin Is a Dual-Target Inhibitor of Plasmodium falciparum Mitochondrial Complex II and Complex III

An overview on the antimalarial activity of 1,2,4-trioxanes, 1,2,4-trioxolanes and 1,2,4,5-tetraoxanes

The demand for novel, fast-acting, and effective antimalarial medications is increasing exponentially. Multidrug resistant forms of malarial parasites, which are rapidly spreading, pose a serious threat to global health. Drug resistance has been addressed using a variety of strategies, such as targeted therapies, the hybrid drug idea, the development of advanced analogues of pre-existing drugs, and the hybrid model of resistant strains control mechanisms. Additionally, the demand for discovering new potent drugs grows due to the prolonged life cycle of conventional therapy brought on by the emergence of resistant strains and ongoing changes in existing therapies. The 1,2,4-trioxane ring system in artemisinin (ART) is the most significant endoperoxide structural scaffold and is thought to be the key pharmacophoric moiety required for the pharmacodynamic potential of endoperoxide-based antimalarials. Several derivatives of artemisinin have also been found as potential treatments for multidrug-resistant strain in this area. Many 1,2,4-trioxanes, 1,2,4-trioxolanes, and 1,2,4,5-tetraoxanes derivatives have been synthesised as a result, and many of these have shown promise antimalarial activity both in vivo and in vitro against Plasmodium parasites. As a consequence, efforts to develop a functionally straight-forward, less expensive, and vastly more effective synthetic pathway to trioxanes continue. This study aims to give a thorough examination of the biological properties and mode of action of endoperoxide compounds derived from 1,2,4-trioxane-based functional scaffolds. The present system of 1,2,4-trioxane, 1,2,4-trioxolane, and 1,2,4,5-tetraoxane compounds and dimers with potentially antimalarial activity will be highlighted in this systematic review (January 1963-December 2022).

Special Issue "Drug Candidates for the Treatment of Infectious Diseases"

Infectious diseases encompass a range of conditions stemming from parasites [...].

Expression and copper binding studies of a Plasmodium falciparum protein with Cox19 copper binding motifs

Copper can exist in an oxidized and a reduced form, which enables the metal to play essential roles as a catalytic co-factor in redox reactions in many organisms. Copper confers redox activity to the terminal electron transport chain cytochrome c oxidase protein. Cytochrome c oxidase in yeast obtains copper for the Cu_B site in the Cox1 subunit from Cox11 in association with Cox19. When copper is chelated in growth medium, Plasmodium falciparum parasite development in infected red blood cells is inhibited and excess copper is toxic for the parasite. The gene of a 26 kDa Plasmodium falciparum PfCox19 protein with two Cx₉C Cox19 copper binding motifs, was cloned and expressed as a 66 kDa fusion protein with maltose binding protein and affinity purified (rMBP-PfCox19). rMBP-PfCox19 bound copper measured by: a bicinchoninic acid release assay; an in vivo bacterial host growth inhibition assay; ascorbate oxidation inhibition and differential scanning fluorimetry. The native protein was detected by antibodies raised against rMBP-PfCox19. PfCox19 binds copper and is predicted to associate with PfCox11 in the insertion of copper into the Cu_B site of Plasmodium cytochrome c oxidase. Characterisation of the proteins involved in Plasmodium spp. copper metabolism will help us understand the role of cytochrome c oxidase and this essential metal in Plasmodium homeostasis.

Plasmodium Parasite Malate-Quinone Oxidoreductase Functionally Complements a Yeast Deletion Mutant of Mitochondrial Malate Dehydrogenase

The emergence of drug-resistant variants of malaria-causing Plasmodium parasites is a life-threatening problem worldwide. Investigation of the physiological function of individual parasite proteins is a prerequisite for a deeper understanding of the metabolic pathways required for parasite survival and therefore a requirement for the development of novel antimalarials. A Plasmodium membrane protein, malate-quinone oxidoreductase (MQO), is thought to contribute to the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC) and is an antimalarial drug target. However, there is little information on its expression and function. Here, we investigated the function of Plasmodium falciparum MQO (PfMQO) in mitochondria using a yeast heterologous expression system. Using a yeast deletion mutant of mitochondrial malate dehydrogenase (MDH1), which is expected to be functionally similar to MQO, as a background strain, we successfully constructed PfMQO-expressing yeast. We confirmed that expression of PfMQO complemented the growth defect of the MDH1 deletion, indicating that PfMQO can adopt the metabolic role of MDH1 in energy transduction for growth in the recombinant yeast. Analysis of cell fractions confirmed that PfMQO was expressed and enriched in yeast mitochondria. By measuring MQO activity, we also confirmed that PfMQO expressed in yeast mitochondria was active. Measurement of oxygen consumption rates showed that mitochondrial respiration was driven by the TCA cycle through PfMQO. In addition, we found that MQO activity was enhanced when intact mitochondria were sonicated, indicating that the malate binding site of PfMQO is located facing the mitochondrial matrix. IMPORTANCE We constructed a model organism to study the physiological role and function of P. falciparum malate-quinone oxidoreductase (PfMQO) in a yeast expression system. PfMQO is actively expressed in yeast mitochondria and functions in place of yeast mitochondrial malate dehydrogenase, which catalyzes the oxidation of malate to oxaloacetate in the TCA cycle. The catalytic site for the oxidation of malate in PfMQO, which is a membrane-bound protein, faces into the mitochondrial matrix, not the mitochondrial inner membrane space. Our findings clearly show that PfMQO is a TCA cycle enzyme and is coupled with the ETC via ubiquinone reduction.