title: Whole cell imaging reveals novel modular features of the exomembrane system of the malaria parasite, Plasmodium falciparum.
abstract: During its intra-erythrocytic development Plasmodium falciparum establishes a membrane network beyond its own limiting membrane in the cytoplasm of its host. These membrane structures play an important role in the trafficking of virulence proteins to the erythrocyte surface, however their ultrastructure is only partly defined and there is on-going debate regarding their origin, organisation and connectivity. We have used two whole cell imaging modalities to explore the topography of parasitised erythrocytes. Three-dimensional structured illumination microscopy provides resolution beyond the optical diffraction limit and permits analysis of fluorescently labelled whole cells. Immunoelectron tomography offers the possibility of high resolution imaging of individual ultrastructural features in a cellular context. Combined with serial sectioning and immunogold labelling, this technique permits precise mapping of whole cell architecture. We show that the P. falciparum exported secretory system comprises a series of modular units, comprising flattened cisternae, known as Maurer's clefts, tubular connecting elements, two different vesicle populations and electron-dense structures that have fused with the erythrocyte membrane. The membrane network is not continuous, pointing to an important role for vesicle-mediated transport in the delivery of cargo to different destinations in the host cell.
authors.affiliation: Department of Biochemistry and Center of Excellence for Coherent X-ray Science, La Trobe University, Melbourne, VIC 3086, Australia. E.Hanssen@latrobe.edu.au
authors.forename: Eric
authors.initials: E
authors.lastname: Hanssen
authors.forename: Peter
authors.initials: P
authors.lastname: Carlton
authors.forename: Samantha
authors.initials: S
authors.lastname: Deed
authors.forename: Nectarios
authors.initials: N
authors.lastname: Klonis
authors.forename: John
authors.initials: J
authors.lastname: Sedat
authors.forename: Joe
authors.initials: J
authors.lastname: DeRisi
authors.forename: Leann
authors.initials: L
authors.lastname: Tilley
mesh_terms: D000818:Animals; D002462:Cell Membrane; D055032:Electron Microscope Tomography; D004910:Erythrocyte Membrane / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology* / Q000648:ultrastructure*; D006790:Host-Parasite Interactions; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D008854:Microscopy, Electron; D010963:Plasmodium falciparum / Q000472:pathogenicity / Q000648:ultrastructure*; D015800:Protozoan Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure*; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D037521:Virulence Factors