Expression And Function Analysis Of Plasmodium Falciparum Rhoptry Neck Protein3

Malaria is one of the most prevalent and deadly global infectious diseases, morethan half of the world’s population is at the risk of infection. Among the five parasitescausing malaria in humans, Plasmodium falciparum is the species responsible for thehighest morbidity. Different strategies to eradicate this disease have been designed,however, the safe and effective malaria vaccine is one of the most important means toprevent the parasite infection. Merozoite surface proteins and some rhoptry andmicronemal proteins have been considered as vaccine targets, since they are exposedto the immune system during the invasion of red blood cells.The process of merozoite invasion into the erythrocyte is complex and multistep,There is growing evidence to suggest that proteins secreted from organelles (rhoptryand micronemes) play key roles in this process. Recently, three of P. falciparumproteins (PfRON2,4and5) were found to be located in the rhoptry neck and interactwith the micronemal protein apical membrane antigen1(PfAMA1) to form a movingjunction complex that play key roles in the process of invasion erythrocyte. However,Recent results suggest that PfRON3partakes in the novel PfRON complex formation(PfRON2,3, and4), but not in the moving junction complex (PfRON2,4,5, andPfAMA1). The function of PfRON3in the process of invasion erythrocyte have yet tobe characterized.The expression of PfRON3was analysed via real-time quantitative PCR, and therecombinant PfRON3proteins were generated with an Escherichia coli expressionsystem. The expression of PfRON3protein was analysed via Western blot assay. Thesubcellular localization of PfRON3was assessed with immunoelectron microscopyand immunofluorescence assay (IFA). The native and recombinant PfRON3proteinwere used to test the erythrocyte-binding activity and the heparin binding assay wereused recombinant PfRON3protein. The recognition PfRON3by malaria immune serawas analysed with an enzyme-linked immunosorbent assay (ELISA) and invasioninhibition assays were carried out with PfRON3-specific antibodies. The data of this study indicate that PfRON3was primarily expressed during thelate trophozoite stage, with a peak in transcription levels at40hours post-invasion.The subcellular localization of PfRON3was confirmed that it is a merozoite rhoptrybulb protein. The native and recombinant PfRON3could bind to erythrocytesuggested that PfRON3contains a region that mediates the interaction betweenmerozoites and human erythrocytes. PfRON3could bind to heparin specificallysuggested that PfRON3would be likely to mediates the erythrocyte invasion bybingding glycosaminoglycans. PfRON3is recognized by the antibodies of individualsliving in malaria endemic areas and PfRON3-specifc antibodies could inhibit theparasite invasion into erythrocytes suggested PfRON3as an important immunogenduring parasite infection.In conclusion, the data of this study indicate that PfRON3is an important proteinfunctioning in P. falciparum and could be a potential malaria vaccine candidate.