Yeast Model Uncovers Dual Roles of Mitochondria in the Action of Artemisinin

Abstract

Artemisinins, derived from the wormwood herb Artemisia annua, are the most potent antimalarial drugs currently available. Despite extensive research, the exact mode of action of artemisinins has not been established. Here we use yeast, Saccharamyces cerevisiae, to probe the core working mechanism of this class of antimalarial agents. We demonstrate that artemisinin's inhibitory effect is mediated by disrupting the normal function of mitochondria through depolarizing their membrane potential. Moreover, in a genetic study, we identify the electron transport chain as an important player in artemisinin's action: Deletion of NDE1 or NDI1, which encode mitochondrial NADH dehydrogenases, confers resistance to artemisinin, whereas overexpression of NDE1 or NDI1 dramatically increases sensitivity to artemisinin. Mutations or environmental conditions that affect electron transport also alter host's sensitivity to artemisinin. Sensitivity is partially restored when the Plasmodium falciparum NDI1 ortholog is expressed in yeast ndi1 strain. Finally, we showed that artemisinin's inhibitory effect is mediated by reactive oxygen species. Our results demonstrate that artemisinin's effect is primarily mediated through disruption of membrane potential by its interaction with the electron transport chain, resulting in dysfunctional mitochondria. We propose a dual role of mitochondria played during the action of artemisinin: the electron transport chain stimulates artemisinin's effect, most likely by activating it, and the mitochondria are subsequently damaged by the locally generated free radicals.

Artemisia annua mutant impaired in artemisinin synthesis demonstrates importance of nonenzymatic conversion in terpenoid metabolism

“…Together, these findings highlight the importance of nonenzymatic conversions in terpenoid metabolism of A. annua glandular secretory trichomes. These findings, together with the observation that artemisinin is known to be cytotoxic to various cell types (4,33,34), suggest a functional requirement for the specialized subapical cavity as a location for both chemical conversion and storage. It also highlights the challenges of producing certain types of plant natural products in microbial systems that lack this level of structural complexity and the need for more research into the compartmentation of metabolic processes in plant production systems.…”

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

“…However, it is important to note that target identification is not absolutely necessary for the successful discovery and development of a new malaria drug. For example, atovaquone was originally thought to target dihydroorate dehydrogenase, but it actually targets a cytochrome (19), and the target of artemisinin is still not completely clear (11). However, target identification is an important step in any comprehensive development of antimalarial genomic studies.…”

“…The parasite's folate metabolism is targeted by the antifolates (sulfadoxine-pyrimethamine and dapsone), and its mitochondria are targeted by atovaquone (6). In addition to these targets, artemisinin, or more likely an artemisinin-derived molecule, probably targets the sarcoand/or endoplasmic reticulum Ca 2ϩ ATPase (11). The P. falciparum genome has been sequenced, revealing over 5,500 genes of P. falciparum that surely contain a large, though admittedly unknown, number of targets that are suitable for small-molecule intervention (9).…”

The Antimalarial Drug Quinine Disrupts Tat2p-mediated Tryptophan Transport and Causes Tryptophan Starvation

“…Consequently, the yeast deletion strains have been used previously to identify genetic defects that in humans could be the basis for the sensitivities of certain individuals to antimicrobial drugs (12,20). In this study, we applied this approach to the problem of adverse reactions to a major antimalarial drug for the first time, noting that similar approaches have been exploited recently for mode of action discovery with certain other antimalarials (17,21). Our analysis led to the key finding that yeast trp mutants (which rely on an exogenous supply of Trp, like mammals) are quinine-hypersensitive, and that quinine specifically obstructs Trp acquisition by cells.…”