Sexual Stage Adhesion Proteins Form Multi-protein Complexes in the Malaria Parasite Plasmodium falciparum

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.

Sex-Specific Biology of the Human Malaria Parasite Revealed from the Proteomes of Mature Male and Female Gametocytes

“…Of the six LCCL domain-containing proteins, three (PbCCp2, PbCCp4 and PbFNPA) were not identified in P. berghei, whereas all PfCCps except PfCCp4 were identified in P. falciparum (supplemental Table S8D). This is in agreement with previous studies, which showed translational repression of PbCCps in P. berghei but not in P. falciaprum (76,77). Taken together, these results highlighted considerable differences in the gametocyte proteomes between these two parasite species.…”

The development of malaria parasites in the mosquito midgut

“…Several proteins have been linked to microgamete attachment to macrogametes, including the LCCL‐domain proteins (termed CCp proteins in P . falciparum ) and the six‐cys motif proteins Ps47, Ps48/45 and Ps230 (van Dijk et al ., 2001; Pradel et al ., 2004; van Schaijk et al ., 2006; Simon et al ., 2009, 2016). The latter two are considered as promising candidates for transmission blocking vaccines (reviewed in Pradel, 2007).…”

“…It has recently been shown that in P . falciparum Ps230, Ps48/45 and the six CCp proteins assemble to multi‐protein complexes, which are linked via P25 to the macrogamete surface (Simon et al ., 2009, 2016; reviewed in Kuehn et al ., 2010). …”

Lysine Acetylation in Sexual Stage Malaria Parasites Is a Target for Antimalarial Small Molecules

“…During gametocytogenesis and transmission, P. falciparum parasites express new sets of genes and proteins likely to be important for sexual development, survival, and reproduction in the mosquito vector (12)(13)(14)(15)(16)(17)(18)(19). For example, gametocyte maturation and gametocytogenesis are accompanied by the coordinated expression of adhesive proteins, such as the epidermal growth factor domain-containing proteins P. falciparum s25 (Pfs25) and P. falciparum s28 (Pfs28), the 6-Cys proteins P. falciparum s230 (Pfs230) and P. falciparum s48/45 (Pfs48/45), and the LCCL domain-containing P. falciparum CCp (PfCCp) proteins (20)(21)(22)(23). Recent work has also identified the P. falciparum gametocyte development 1 (Pfgdv1) gene as being critical for gametocyte production (24).…”