The role of the scaffolding protein WLP1 in maintaining multiprotein complexes of malaria gametocytes

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The human malaria parasite Plasmodium falciparum displays a remarkable number of adhesive proteins on its plasma membrane, which are particularly important for the invasion and transmission stages of the pathogen. The majority of these adhesion proteins assemble to multi-protein complexes (MPCs), like the merozoite surface protein 1 adhesion complex and the apical membrane antigen 1/Rhoptry neck-complex, which are located on the merozoite surface and essential for red blood cell infection. Another well-studied MPC associates with the plasma membrane of gametocytes, sexual precursor cells that are formed during human-to-mosquito transmission of the parasite. The gametocyte-specific adhesion complex is composed of the six LCCL-domain (PfCCp) proteins and the cysteine-rich motif proteins Pfs230 and Pf48/45, all of which are ascribed crucial roles for sexual reproduction and further development of the parasite in the mosquito. In a recent study, we identified a novel interaction partner of the PfCCp-based complex, the WD40-repeat protein-like protein PfWLP1. WD40 domains are highly conserved in eukaryotes and act as scaffolds to facilitate protein interactions, among others during cytoskeleton stabilization. Due to their important functions particularly for proliferating cells, human WD40-repeat proteins are currently explored in cancer therapy. In P. falciparum, in-silico analyses identified 80 putative WD40-repeat proteins with PfWLP1 being specific to the genus Plasmodium. PfWLP1 is highly expressed in the P. falciparum gametocytes, where it co-localizes with microtubules underneath the plasma membrane. The protein is further associated with the PfCCp-based MPCs and the loss of PfWLP1 in transgenic parasites results in instability of these complexes. In view of our current data, we hypothesize that PfWLP1 acts as a scaffold linking the peripheral PfCCp-based MPCs to the intracellular cytoskeleton, thereby maintaining the stability of the complex. In this study we aim to uncover the role of PfWLP1 in MPC maintenance by 1) functionally characterizing WLP1 during gametocyte maturation and gametogenesis using gene-knockdown approaches; 2) deciphering the composition of the PfWLP1-regulated MPCs via BioID methods; and 3) investigating the interdependence between PfWLP1 and selected cytoskeletal elements in corresponding gene-knockdown and gene-knockout lines. Data gained by this study will provide in-depth knowledge on the highly interwoven network of structural elements and adhesive peripheral complexes that are needed to maintain the integrity of malaria gametocytes. Moreover, the project will shed light on the novel scaffolding protein PfWLP1 as a key player of malaria parasite transmission.