title: MSP8 is a non-essential merozoite surface protein in Plasmodium falciparum.
abstract: MSP8 is a recently identified merozoite surface protein that shares similar structural features with the leading vaccine candidate MSP1. Both proteins contain two C-terminal epidermal growth factor (EGF)-like domains, a glycosylphosphatidylinositol (GPI) anchor attachment sequence and undergo proteolytic processing. By double recombination, we have disrupted the MSP8 gene in P. falciparum 3D7 parasites, and confirmed integration by southern hybridisation and PCR. Western blot analysis of lysates from asynchronous cultures and isolated merozoites demonstrated the absence of MSP8 in two cloned knockout lines. There was no significant difference in growth rate observed between 3D7 and the cloned DeltaMSP8 lines. Thus, unlike MSP1, MSP8 is not required for asexual stage parasite growth and replication in vitro. Further analysis of the cloned lines showed that loss of MSP8 had no effect on the levels of expression of other merozoite surface proteins including MSP1-5, 7 and 10. Stage-specific immunoblots showed that MSP8 expression commences in late rings and extends throughout the rest of the erythrocytic life cycle in the 3D7 parent line, but is absent from all stages in the DeltaMSP8 transfectants.
authors.affiliation: Department of Microbiology and the Victorian Bioinformatics Consortium, Monash University, Clayton, Vic. 3800, Australia. casilda.black@med.monash.edu.au
authors.forename: Casilda G
authors.initials: CG
authors.lastname: Black
authors.forename: Tieqiao
authors.initials: T
authors.lastname: Wu
authors.forename: Lina
authors.initials: L
authors.lastname: Wang
authors.forename: Agnieszka E
authors.initials: AE
authors.lastname: Topolska
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D004912:Erythrocytes / Q000469:parasitology; D005455:Fluorescent Antibody Technique; D008018:Life Cycle Stages; D010963:Plasmodium falciparum / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
chemical_list: D000953:Antigens, Protozoan; D015800:Protozoan Proteins; C431669:merozoite surface protein 8, Plasmodium