Phytol distribution in malaria parasites

Abstract

One of the most promising targets for malaria drug design is the isoprenoid metabolism. Isoprenoid biosynthesis depends on the methylerythritol 4-phosphate (MEP) pathway, located in a modified plastid organelle called apicoplast. Isoprenoids produced by this pathway are used for isoprenylation of several metabolites and proteins. Former observations from our group demonstrated the plasmodial biosynthesis of phytyl pyrophosphate (PPP) from geranylgeranyl pyrophosphate (GGPP), and its respective alcohols, phytol (POH) from geranylgeraniol (GGOH). We also characterized the parasitic biosynthesis of phytylated and geranylgeranylated naphtoquinones. Furthermore, exogenous POH and PPP can be covalently attached to proteins clusters. These results add phytylation as a novel posttranslational modification of proteins. Proteomic and bioinformatic approaches revealed that phytylated proteins are involved in parasitic intracellular trafficking. Antiplasmodial activity of the specific MEP pathway inhibitor, fosmidomycin and the ribosomal inhibitor, tetracycline is attenuated by exogenous POH. Previously, similar rescue-effects were observed by several unsaturated isoprenoid precursors such as isoprene and various unsaturated oligoprenyl pyrophosphates and isoprenoid alcohols. Despite the effects observed in vitro, it is unlikely to occur in vivo since those metabolites are not readily available in the host plasma. However, POH is naturally present in blood and thus, exogenous incorporation from plasma may be a plausible resistance mechanism to fosmidomycin. Despite of the evidence of incorporation of exogenous POH into malaria parasites, it is still unknown the mechanism of interconversion of POH in its active form, PPP. This project is aimed to investigate the presence of the mechanism of POH rescues malaria parasites from the effects of fosmidomycin. Furthermore, this project is aimed to create knockout parasites for POH kinase and explore this enzymatic step as a drug target to render more effective the fosmidomicyn-based treatment. (AU)