Laboratory of Pathogens and Host Immunity

Research projects – Team 2

Theme 1: DECIPHERING THE PLASMODIUM PHOSPHOLIPID METABOLISM.

Group leader : Pr. Rachel CERDAN

PIs: Rachel Cerdan, Sharon Wein, Kai Wengelnik

Phospholipids (PLs) are essential components of biological membranes. The malaria parasite Plasmodium falciparum, uses its own metabolic machinery to synthetized PLs through a complex network of metabolic pathways. The most abundant PLs in the P. falciparum infected red blood cell are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI) and they constitute the bulk of the lipids that form parasite membranes.

1- Based on lipidomics we recently obtained a comprehensive overview of the metabolism of the main PLs in P. falciparum. Our data raised new questions about the sources of PLs, the links between the multiple pathways and the existence of some specific enzymatic steps.

Our objective is to identify the bottlenecks, the compensatory effects and the interplay between the different PL pathways by lipidomic studies using deuterium-labelled precursors. The findings will allow us to select new therapeutic targets.

We previously identified the enzyme CCT (CTP:phosphocholine cytidylyltransferase) in the PC biosynthesis pathway as promising potential target. Our team determined the 3D structures of the PfCCT catalytic domain in the absence and in the presence of its substrates and its product. OU goal is to identify and to optimize new PfCCT specific inhibitors with antimalarial activity using an integrated target-based approach combining screening of ligands and 3D structure determination.

2- Phosphoinositides (PPIs), the phosphorylated derivatives of PI, are quantitatively minor PLs with important functions in intracellular signalling and membrane identity. We identified the PPIs present in P. falciparum-infected erythrocytes and produced a catalogue of enzymes and binding proteins that are predicted in the Plasmodium proteome.

Our objective is to characterise lipid kinases, lipid phosphatases and PPI-binding proteins and to evaluate their potential as future drug targets.

Theme 2: The genetic landscape of DNA replication in Plasmodium falciparum

Group leader : Dr. Ana Rita GOMES

DNA replication is a process essential to life. However, mechanisms of genome duplication present a high level of diversity across the tree of life. Although the mechanisms governing this ubiquitous process have been extensively studied in model systems such as yeast or mammalian cells, these systems cover only a fraction of the existing biodiversity and are thus not suitable models for more divergent eukaryotes. The Apicomplexa phylum comprises divergent single-celled eukaryotic organisms with significant clinical relevance, such as Plasmodium parasites, the causative agent of malaria. The development of better and targeted strategies that will efficiently block the development of the parasite has become urgent with the recent emergence of drug resistance to the last efficacious antimalarials.

The pathogenicity of Plasmodium is, in part, linked to its high multiplication rate during vegetative growth within the human host. During this cycle the parasite’s genomic content undergoes several DNA replication rounds, within an enclosed nucleus, after which newly formed, non-condensed, nuclei are segregated into daughter cells, in a process termed schizogony. Currently, we lack basic knowledge such as a clear definition of the parasite’s replicative cycle, how it is regulated and to what extent general eukaryotic DNA replication principles apply to this organism.

Our goal is to perform the first comprehensive study of DNA replication factors and initiation mechanisms in Plasmodium falciparum, the deadliest human parasite. We will achieve this through the following aims:

(1) Identify and characterise factors orchestrating initiation of DNA replication;

(2) Study the genetic landscape of origins of replication;

(3) Explore the genomic determinants of origin specification.

Theme 3: Development of new compounds and evaluation of their antimalarial potential

Project 1: Development of purine analogues as potent antimalarial compounds.

PIs: Rachel Cerdan, Sharon Wein

We have identified a novel series of AcycloNucleoside Phosphonates (ANPs) with significant antimalarial activity in vitro against asexual blood stages and efficacy in vivo (P. vinckei- and P. berghei-infected mice). The lead compound shows an antimalarial activity in the nanomolar range with a very high selectivity index. ANPs are structurally unrelated to existing drugs and they have an original mode of action.

Our first objectives are:

  • to optimize the lead compound of this class and to design an orally administrable molecule that is suitable to be developed in the preclinical phase.

  • to assess the inhibitory potential of the compound on the different stages of the life cycle of the Plasmodium parasite.

  • to decipher its mode of action by identifying and validating its therapeutic target.

Project 2: Evaluation of a new principle of antimalarial strategy through the chemical activation of the host cell specific mechano-sensitive ion channel Piezo1.

PI: Kai Wengelnik

Piezo channels are mechanosensitive cation channels of higher eukaryotic organisms that are absent from Plasmodium species or other apicomplexan parasites. Red blood cells (RBCs) express only the Piezo1 channel. A link between Piezo1 function and malaria infection has first been shown using a mouse model. The protective phenotype has been linked to the hydration status of the RBCs. Most interestingly, this study also identified a new polymorphism in human Piezo1 that is very abundant in healthy people of African origin (about 30% of carriers). This polymorphism confers a reduction in RBC infection rates by P. falciparum in in vitro cultures. Currently very few compounds have been described to interfere with Piezo1 function, the most widely used being the Piezo1 activator Yoda1.

The aims of our project are the following:

  • Characterisation of the protective effect of Piezo1 activation through chemical stimulation on falciparum infection.
  • Identification and selection of new Piezo1 activators with potent antimalarial activity.
  • Evaluation whether the chemical activation of Piezo1 of the human RBC could serve as a new principle of antimalarial strategy since we are targeting a host cell protein and not the parasite itself.