Plasmodial ortholog of Toxoplasma gondii rhoptry neck protein 3 is localized to the rhoptry body.
The proteins in apical organelles of Plasmodium falciparum merozoite play an important role in invasion into erythrocytes. Several rhoptry neck (RON) proteins have been identified in rhoptry proteome of the closely-related apicomplexan parasite, Toxoplasma gondii. Recently, three of P. falciparum proteins orthologous to TgRON proteins, PfRON2, 4 and 5, were found to be located in the rhoptry neck and interact with the micronemal protein apical membrane antigen 1 (PfAMA1) to form a moving junction complex that helps the invasion of merozoite into erythrocyte. However, the other P. falciparum RON proteins have yet to be characterized. Here, we determined that "PFL2505c" (hereafter referred to as pfron3) is the ortholog of the tgron3 in P. falciparum and characterized its protein expression profile, subcellular localization, and complex formation. Protein expression analysis revealed that PfRON3 was expressed primarily in late schizont stage parasites. Immunofluorescence microscopy (IFA) showed that PfRON3 localizes in the apical region of P. falciparum merozoites. Results from immunoelectron microscopy, along with IFA, clarified that PfRON3 localizes in the rhoptry body and not in the rhoptry neck. Even after erythrocyte invasion, PfRON3 was still detectable at the parasite ring stage in the parasitophorous vacuole. Moreover, co-immunoprecipitation studies indicated that PfRON3 interacts with PfRON2 and PfRON4, but not with PfAMA1. These results suggest that PfRON3 partakes in the novel PfRON complex formation (PfRON2, 3, and 4), but not in the moving junction complex (PfRON2, 4, 5, and PfAMA1). The novel PfRON complex, as well as the moving junction complex, might play a fundamental role in erythrocyte invasion by merozoite stage parasites.
Cell-Free Science and Technology Research Center, Ehime University, Matsuyama, Ehime 790-8577, Japan.
Daisuke
D
Ito
Eun-Taek
ET
Han
Satoru
S
Takeo
Amporn
A
Thongkukiatkul
Hitoshi
H
Otsuki
Motomi
M
Torii
Takafumi
T
Tsuboi
D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D047468:Immunoprecipitation; D052940:Merozoites / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D015388:Organelles / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity*; D015800:Protozoan Proteins / Q000276:immunology / Q000378:metabolism*; D052939:Schizonts / Q000378:metabolism; D014122:Toxoplasma
C506564:AMA1 protein, Toxoplasma gondii; D000953:Antigens, Protozoan; D015800:Protozoan Proteins