title: Genetic ablation of a Maurer's cleft protein prevents assembly of the Plasmodium falciparum virulence complex.
abstract: The malaria parasite Plasmodium falciparum assembles knob structures underneath the erythrocyte membrane that help present the major virulence protein, P. falciparum erythrocyte membrane protein-1 (PfEMP1). Membranous structures called Maurer's clefts are established in the erythrocyte cytoplasm and function as sorting compartments for proteins en route to the RBC membrane, including the knob-associated histidine-rich protein (KAHRP), and PfEMP1. We have generated mutants in which the Maurer's cleft protein, the ring exported protein-1 (REX1) is truncated or deleted. Removal of the C-terminal domain of REX1 compromises Maurer's cleft architecture and PfEMP1-mediated cytoadherance but permits some trafficking of PfEMP1 to the erythrocyte surface. Deletion of the coiled-coil region of REX1 ablates PfEMP1 surface display, trapping PfEMP1 at the Maurer's clefts. Complementation of mutants with REX1 partly restores PfEMP1-mediated binding to the endothelial cell ligand, CD36. Deletion of the coiled-coil region or complete deletion of REX1 is tightly associated with the loss of a subtelomeric region of chromosome 2, encoding KAHRP and other proteins. A KAHRP-green fluorescent protein (GFP) fusion expressed in the REX1-deletion parasites shows defective trafficking. Thus, loss of functional REX1 directly or indirectly ablates the assembly of the P. falciparum virulence complex at the surface of host erythrocytes.
authors.affiliation: La Trobe Institute for Molecular Science, Department of Biochemistry and Centre of Excellence for Coherent X-ray Science, La Trobe University, Vic. 3086, Australia. mwadixon@gmail.com
authors.forename: Matthew W A
authors.initials: MW
authors.lastname: Dixon
authors.forename: Shannon
authors.initials: S
authors.lastname: Kenny
authors.forename: Paul J
authors.initials: PJ
authors.lastname: McMillan
authors.forename: Eric
authors.initials: E
authors.lastname: Hanssen
authors.forename: Katharine R
authors.initials: KR
authors.lastname: Trenholme
authors.forename: Donald L
authors.initials: DL
authors.lastname: Gardiner
authors.forename: Leann
authors.initials: L
authors.lastname: Tilley
mesh_terms: D018955:CD36 Antigens / Q000378:metabolism; D002448:Cell Adhesion; D042783:Endothelial Cells / Q000378:metabolism; D004912:Erythrocytes / Q000469:parasitology; D005816:Genetic Complementation Test; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000235:genetics* / Q000378:metabolism*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism*; D017384:Sequence Deletion; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D018955:CD36 Antigens; D008565:Membrane Proteins; D010455:Peptides; D015800:Protozoan Proteins; C541886:REX1 protein, Plasmodium falciparum; D037521:Virulence Factors; C085731:erythrocyte membrane protein 1, Plasmodium falciparum; C042968:knob protein, Plasmodium falciparum