Résumé
The malaria parasite, Plasmodium falciparum, develops and multiplies in the human erythrocyte. Phospholipids (PLs) are essential for P. falciparum growth, and phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) represent over 95 % of its PLs in which PC is the most abundant. These PLs are synthesized de novo by several metabolic pathways which coexist. Although most of the genes and related enzymes of the PLs biosynthesis pathways are characterized, little is known about their regulation and contribution to PLs metabolism at the parasite’s intraerythrocytic stages. Our project aims to break down these aspects to improve the identification of key targets for the development of new antimalarial drugs. In this context, we used deuterated precursors of PLs including serine-d3, ethanolamine-d4, choline-d13 and C16:0-13C2-lysophosphatidylcholine-d9 to follow and quantify simultaneously their incorporation in the intermediate metabolites and the final PLs by metabolomics. First, we demonstrate that at least 65% of PC comes from LPC against 6% from free choline, the rest being supplied via transverse pathways (ethanolamine and serine or RBC). Then, we show that LPC is cleaved prior its incorporation as choline into PC and as palmitic acid into all PLs. Furthermore, we studied the contribution of the two first enzymes involved in PC biosynthesis using conditional KO mutants of Pfck and Pfcct genes. The absence of PfCK induces 90% of parasite death after the first cycle, indicating a limited compensation by alternative pathways. The 10% remaining parasites exhibit halved PC content and a lower growth rate likely due to the drop in PC biosynthesis. In contrast with PfCK, PfCCT is essential for the parasite survival, this highlights the role of PfPMT that likely ensure parasite survival of PfCK∆ but not PfCCT∆. These results show the complexity of Plasmodium PLs metabolism, and suggest good perspectives to develop PfCCT inhibitors as antimalarial.