No abstract

The sexual phase of the malaria parasite Plasmodium falciparum is accompanied by the coordinated expression of stagespecific adhesive proteins. Among these are six secreted proteins with multiple adhesion domains, termed P. falciparum LCCL domain-containing protein (PfCCp) proteins, which are expressed in the parasitophorous vacuole of the differentiating gametocytes and which are later associated with macrogametes. Although the majority of the PfCCp proteins are implicated in parasite development in the mosquito vector, their functions remain unknown. In the present study we investigated the molecular interactions between the PfCCp proteins during gametocyte development and emergence. Using five different gene-disruptant parasite lines, we show that the lack of one PfCCp protein leads to the loss of other PfCCp family members. Co-immunoprecipitation assays on gametocyte lysates revealed formation of complexes involving all PfCCp proteins, and affinity chromatography co-elution binding assays with recombinant PfCCp domains further indicated direct binding between distinct adhesion domains. PfCCp-coated latex beads bind to newly formed macrogametes but not to gametocytes or older macrogametes 6 or 24 h post-activation. In view of these data, we propose that the PfCCp proteins form multi-protein complexes that are exposed during gametogenesis, thereby mediating cell contacts of macrogametes.

This paper describes the synthesis of a new class of peptidomimetic cysteine protease inhibitors based on a 1,4-benzodiazepine scaffold and on an electrophilic vinyl sulfone moiety. The former was introduced internally to a peptide sequence that mimics the fragment D-Ser-Gly; the latter was built on the P1-P1' site and reacts as a classical "Michael acceptor", leading to an alkylated enzyme by irreversible addition of the thiol group of the active site cysteine. The introduction of the vinyl sulfone moiety has been accomplished by olefin cross-metathesis, a powerful tool for the formation of carbon-carbon double bonds. New compounds 2-3 have been proven to be potent and selective inhibitors of falcipain-2, a cysteine protease isolated from Plasmodium falciparum, displaying antiplasmodial activity.

A series of etacrynic acid derivatives was synthesized and screened for their in vitro activity against Plasmodium falciparum, as well as their activity against recombinantly expressed falcipain-2 and -3. The two most active compounds of the series displayed IC50 values of 9.0 and 18.8 μM against Plasmodia.