SURFIN is a polymorphic antigen expressed on Plasmodium falciparum merozoites and infected erythrocytes.
The surfaces of the infected erythrocyte (IE) and the merozoite, two developmental stages of malaria parasites, expose antigenic determinants to the host immune system. We report on surface-associated interspersed genes (surf genes), which encode a novel polymorphic protein family, SURFINs, present on both IEs and merozoites. A SURFIN expressed in 3D7 parasites, SURFIN4.2, was identified by mass spectrometric analysis of peptides cleaved off the surface of live IEs with trypsin. SURFINs are encoded by a family of 10 surf genes, including three predicted pseudogenes, located within or close to the subtelomeres of five of the chromosomes. SURFINs show structural and sequence similarities with exported surface-exposed proteins (PvSTP1, PkSICAvar, PvVIR, Pf332, and PfEMP1) of several Plasmodium species. SURFIN4.2 of a parasite other than 3D7 (FCR3S1.2) showed polymorphisms in the extracellular domain, suggesting sequence variability between genotypes. SURFIN4.2 not only was found cotransported with PfEMP1 and RIFIN to the IE surface, but also accumulated in the parasitophorous vacuole. In released merozoites, SURFIN4.2 was present in an amorphous cap at the parasite apex, where it may be involved in the invasion of erythrocytes. By exposing shared polymorphic antigens on IEs and merozoites, the parasite may coordinate the antigenic composition of these attachment surfaces during growth in the bloodstream.
Winter
Gerhard
G
Microbiology and Tumorbiology Center, Karolinska Institutet, SE-17177 Stockholm, Sweden.
Kawai
Satoru
S
Haeggström
Malin
M
Kaneko
Osamu
O
von Euler
Anne
A
Kawazu
Shin-ichiro
S
Palm
Daniel
D
Fernandez
Victor
V
Wahlgren
Mats
M
D000818:Animals; D000953:Antigens, Protozoan / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D004912:Erythrocytes / Q000276:immunology / Q000378:metabolism* / Q000469:parasitology; D005786:Gene Expression Regulation / Q000276:immunology; D017125:Genes, Protozoan / Q000235:genetics / Q000276:immunology*; D005838:Genotype; D006790:Host-Parasite Interactions / Q000235:genetics / Q000276:immunology; D006801:Humans; D016778:Malaria, Falciparum / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000276:immunology; D010963:Plasmodium falciparum / Q000276:immunology / Q000378:metabolism*; D011110:Polymorphism, Genetic / Q000276:immunology; D014617:Vacuoles / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D000953:Antigens, Protozoan; D008565:Membrane Proteins; C503134:SURFIN 4.2 protein, Plasmodium falciparum