Rhoptry neck protein RON2 forms a complex with microneme protein AMA1 in Plasmodium falciparum merozoites

Parasitol Int. 2008 Oct 7. [Epub ahead of print]

Rhoptry neck protein RON2 forms a complex with microneme protein AMA1 in Plasmodium falciparum merozoites

Cao J, Kaneko O, Thongkukiatkul A, Tachibana M, Otsuki H, Gao Q, Tsuboi T, Torii M.

Department of Molecular Parasitology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan; Malaria Department, Jiangsu Institute of Parasitic Diseases, Meiyuan, Wuxi, Jiangsu 214064, People's Republic of China.

Erythrocyte invasion is an essential step in the establishment of host infection by malaria parasites, and is a major target of intervention strategies that attempt to control the disease. Recent proteome analysis of the closely-related apicomplexan parasite, Toxoplasma gondii, revealed a panel of novel proteins (RONs) located at the neck portion of the rhoptries. Three of these proteins, RON2, RON4, and RON5 have been shown to form a complex with the microneme protein Apical Membrane Protein 1 (AMA1). This complex, termed the Moving Junction complex, localizes at the interface of the parasite and the host cell during the invasion process. Here we characterized a RON2 ortholog in Plasmodium falciparum. PfRON2 transcription peaked at the mature schizont stage and was expressed at the neck portion of the rhoptry in the merozoite. Co-immunoprecipitation of PfRON2, PfRON4 and PfAMA1 indicated that the complex formation is conserved between T. gondii and P. falciparum, suggesting that co-operative function of the rhoptry and microneme proteins is a common mechanism in apicomplexan parasites during host cell invasion. PfRON2 possesses a region displaying homology with the rhoptry body protein PfRhopH1/Clag, a component of the RhopH complex. However, here we present co-immunoprecipitation studies which suggest that PfRON2 is not a component of the RhopH complex and has an independent role. Nucleotide polymorphism analysis suggested that PfRON2 was under diversifying selective pressure. This evidence suggests that RON2 appears to have a fundamental role in host cell invasion by apicomplexan parasites, and is a potential target for malaria intervention strategies.

PMID: 18952195 [PubMed - as supplied by publisher]