title: Artemisinins target the SERCA of Plasmodium falciparum.
abstract: Artemisinins are extracted from sweet wormwood (Artemisia annua) and are the most potent antimalarials available, rapidly killing all asexual stages of Plasmodium falciparum. Artemisinins are sesquiterpene lactones widely used to treat multidrug-resistant malaria, a disease that annually claims 1 million lives. Despite extensive clinical and laboratory experience their molecular target is not yet identified. Activated artemisinins form adducts with a variety of biological macromolecules, including haem, translationally controlled tumour protein (TCTP) and other higher-molecular-weight proteins. Here we show that artemisinins, but not quinine or chloroquine, inhibit the SERCA orthologue (PfATP6) of Plasmodium falciparum in Xenopus oocytes with similar potency to thapsigargin (another sesquiterpene lactone and highly specific SERCA inhibitor). As predicted, thapsigargin also antagonizes the parasiticidal activity of artemisinin. Desoxyartemisinin lacks an endoperoxide bridge and is ineffective both as an inhibitor of PfATP6 and as an antimalarial. Chelation of iron by desferrioxamine abrogates the antiparasitic activity of artemisinins and correspondingly attenuates inhibition of PfATP6. Imaging of parasites with BODIPY-thapsigargin labels the cytosolic compartment and is competed by artemisinin. Fluorescent artemisinin labels parasites similarly and irreversibly in an Fe2+-dependent manner. These data provide compelling evidence that artemisinins act by inhibiting PfATP6 outside the food vacuole after activation by iron.
authors.affiliation: Department of Cellular and Molecular Medicine, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: U
authors.initials: U
authors.lastname: Eckstein-Ludwig
authors.forename: R J
authors.initials: RJ
authors.lastname: Webb
authors.forename: I D A
authors.initials: ID
authors.lastname: Van Goethem
authors.forename: J M
authors.initials: JM
authors.lastname: East
authors.forename: A G
authors.initials: AG
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Kimura
authors.forename: P M
authors.initials: PM
authors.lastname: O'Neill
authors.forename: P G
authors.initials: PG
authors.lastname: Bray
authors.forename: S A
authors.initials: SA
authors.lastname: Ward
authors.forename: S
authors.initials: S
authors.lastname: Krishna
mesh_terms: D000818:Animals; D037621:Artemisinins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology; D009865:Oocytes; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D037621:Artemisinins; D007502:Iron Chelating Agents; D019284:Thapsigargin; D007501:Iron; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D005947:Glucose; D003676:Deferoxamine