Abstract
Phospholipids (PLs) are essential for Plasmodium falciparum growth and transmission, their biosynthesis is therefore considered as a putative target to develop new atypical antimalarials. Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) represent over 95 % of P. falciparum PLs in which PC is the most abundant. These PLs are biosynthesized by three distinct pathways, which can be used for the biosynthesis of PC, highlighting thus its key role in the growth of the parasite. Although most genes coding for enzymes of the PLs biosynthesis pathways were characterized, little is known about their regulation and contribution to PLs metabolism at the intraerythrocytic stages of the parasite. 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, P. falciparum-infected red blood cells (iRBC) were fed with precursors of PLs including serine-d3 (Ser-d3), ethanolamine-d4 (Etn-d4), choline-d13 (Cho-d13) and lysophosphatidylcholine (LPC-d913C2) to easily track their incorporation into PLs and their biosynthetic intermediates by metabolomics. First, we demonstrate that instead of choline, the parasite uses mainly LPC as a precursor for PC biosynthesis and that LPC-d913C2 is cleaved and incorporated as choline and palmitic acid into PC and all PLs, respectively. The same approach was used to study a constitutive knock-out (KO) mutant of the phosphoethanolamine methyltransferase gene (PfPMT∆). This mutant lacks the PfPMT enzyme which bridges both CDP-Cho-dependent and CDP-Etn-dependent Kennedy pathways for PC and PE biosynthesis. Although this mutation is not lethal, the infection rate of PfPMT∆ is lower than wild-type 3D7 strain and our lipidomics results suggest that compensatory effects occur in the PLs metabolism of PfPMT∆. Furthermore, we have generated conditional KO mutants of PfCK and PfCCT genes, coding for the two first enzymes of the PC biosynthetic pathway. Our results indicate that both PfCK and PfCCT are essential for parasite survival. Lipidomics will be applied to analyze early responses induced by the drastic loss of PfCK and PfCCT before the delayed death of these parasites. These results suggest that the development of PfCK and especially PfCCT inhibitors is a promising strategy to fight malaria by inhibiting PLs biosynthesis.