title: Parasite-encoded Hsp40 proteins define novel mobile structures in the cytosol of the P. falciparum-infected erythrocyte.
abstract: Plasmodium falciparum is predicted to transport over 300 proteins to the cytosol of its chosen host cell, the mature human erythrocyte, including 19 members of the Hsp40 family. Here, we have generated transfectant lines expressing GFP- or HA-Strep-tagged versions of these proteins, and used these to investigate both localization and other properties of these Hsp40 co-chaperones. These fusion proteins labelled punctate structures within the infected erythrocyte, initially suggestive of a Maurer's clefts localization. Further experiments demonstrated that these structures were distinct from the Maurer's clefts in protein composition. Transmission electron microscopy verifies a non-cleft localization for HA-Strep-tagged versions of these proteins. We were not able to label these structures with BODIPY-ceramide, suggesting a lower size and/or different lipid composition compared with the Maurer's clefts. Solubility studies revealed that the Hsp40-GFP fusion proteins appear to be tightly associated with membranes, but could be released from the bilayer under conditions affecting membrane cholesterol content or organization, suggesting interaction with a binding partner localized to cholesterol-rich domains. These novel structures are highly mobile in the infected erythrocyte, but based on velocity calculations, can be distinguished from the 'highly mobile vesicles' previously described. Our study identifies a further extra-parasitic structure in the P. falciparum-infected erythrocyte, which we name 'J-dots' (as their defining characteristic so far is the content of J-proteins). We suggest that these J-dots are involved in trafficking of parasite-encoded proteins through the cytosol of the infected erythrocyte.
authors.affiliation: Department of Parasitology, Faculty of Biology, Philipps University Marburg, Marburg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Külzer
authors.forename: Melanie
authors.initials: M
authors.lastname: Rug
authors.forename: Klaus
authors.initials: K
authors.lastname: Brinkmann
authors.forename: Ping
authors.initials: P
authors.lastname: Cannon
authors.forename: Alan
authors.initials: A
authors.lastname: Cowman
authors.forename: Klaus
authors.initials: K
authors.lastname: Lingelbach
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Blatch
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Maier
authors.forename: Jude M
authors.initials: JM
authors.lastname: Przyborski
mesh_terms: D003600:Cytosol / Q000469:parasitology*; D004912:Erythrocytes / Q000469:parasitology*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006388:Hemagglutinins / Q000235:genetics / Q000378:metabolism; D006790:Host-Parasite Interactions; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D010963:Plasmodium falciparum / Q000472:pathogenicity*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods; D019809:Streptavidin / Q000235:genetics / Q000378:metabolism
chemical_list: D050956:HSP40 Heat-Shock Proteins; D006388:Hemagglutinins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D019809:Streptavidin