title: Variant proteins of the Plasmodium falciparum RIFIN family show distinct subcellular localization and developmental expression patterns.
abstract: In order to avoid immune recognition in favor of a chronic infection, the malaria parasite Plasmodium falciparum has developed means to express clonally variant antigens at the surface of the infected erythrocyte (IE). Proteins of the var and rif multicopy gene families, encoding PfEMP1 and RIFINs, respectively, have been implicated in these processes. Here, we studied members of the latter family and present data revealing different subcellular localization patterns for RIFIN variants belonging to two distinct subgroups, which have been designated A- and B-type RIFINs. While A-type RIFINs were found to be associated with the parasite and transported to the surface of infected erythrocytes via Maurer's clefts, B-type RIFINs appeared to be mostly retained inside the parasite. However, expression of both subtypes does not seem to be mutually exclusive. Moreover, both A- and B-type variants were also expressed in the merozoite, present either in the apical region (A-type) or in the cytosol (B-type). The presence of RIFINs in merozoites suggests that antigenic variation in P. falciparum is not only restricted to parasite-derived proteins at the IE surface, but the phenomenon also prevails in other life cycle stages. Interestingly, some RIFIN variants were detected only in intracellular stages and not in merozoites, pointing to differential developmental expression patterns for distinct members of this large protein family.
authors: Bernhard-Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, 20359, Hamburg, Germany.
authors: Michaela
authors: M
authors: Petter
authors: Malin
authors: M
authors: Haeggström
authors: Ayman
authors: A
authors: Khattab
authors: Victor
authors: V
authors: Fernandez
authors: Mo-Quen
authors: MQ
authors: Klinkert
authors: Mats
authors: M
authors: Wahlgren
mesh_terms: D000818:Animals; D000940:Antigenic Variation; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000469:parasitology; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D005810:Multigene Family; D010963:Plasmodium falciparum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000953:Antigens, Protozoan; D015800:Protozoan Proteins