title: Characterization of a novel organelle in Toxoplasma gondii with similar composition and function to the plant vacuole.
abstract: Toxoplasma gondii belongs to the phylum Apicomplexa and is an important cause of congenital disease and infection in immunocompromised patients. Like most apicomplexans, T. gondii possesses several plant-like features, such as the chloroplast-like organelle, the apicoplast. We describe and characterize a novel organelle in T. gondii tachyzoites, which is visible by light microscopy and possesses a broad similarity to the plant vacuole. Electron tomography shows the interaction of this vacuole with other organelles. The presence of a plant-like vacuolar proton pyrophosphatase (TgVP1), a vacuolar proton ATPase, a cathepsin L-like protease (TgCPL), an aquaporin (TgAQP1), as well as Ca(2+)/H(+) and Na(+)/H(+) exchange activities, supports similarity to the plant vacuole. Biochemical characterization of TgVP1 in enriched fractions shows a functional similarity to the respective plant enzyme. The organelle is a Ca(2+) store and appears to have protective effects against salt stress potentially linked to its sodium transport activity. In intracellular parasites, the organelle fragments, with some markers colocalizing with the late endosomal marker, Rab7, suggesting its involvement with the endocytic pathway. Studies on the characterization of this novel organelle will be relevant to the identification of novel targets for chemotherapy against T. gondii and other apicomplexan parasites as well.
authors.affiliation: Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Kildare
authors.initials: K
authors.lastname: Miranda
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Pace
authors.forename: Roxana
authors.initials: R
authors.lastname: Cintron
authors.forename: Juliany C F
authors.initials: JC
authors.lastname: Rodrigues
authors.forename: Jianmin
authors.initials: J
authors.lastname: Fang
authors.forename: Alyssa
authors.initials: A
authors.lastname: Smith
authors.forename: Peter
authors.initials: P
authors.lastname: Rohloff
authors.forename: Elvis
authors.initials: E
authors.lastname: Coelho
authors.forename: Felix
authors.initials: F
authors.lastname: de Haas
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Isabelle
authors.initials: I
authors.lastname: Coppens
authors.forename: L David
authors.initials: LD
authors.lastname: Sibley
authors.forename: Silvia N J
authors.initials: SN
authors.lastname: Moreno
mesh_terms: D017920:Antiporters / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D055032:Electron Microscope Tomography; D004705:Endocytosis; D008853:Microscopy; D009997:Osmotic Pressure; D010944:Plants / Q000648:ultrastructure; D017494:Proton Pumps / Q000378:metabolism; D015800:Protozoan Proteins / Q000032:analysis; D012964:Sodium / Q000378:metabolism; D013312:Stress, Physiological; D014122:Toxoplasma / Q000502:physiology* / Q000648:ultrastructure*; D014617:Vacuoles / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D017920:Antiporters; D017494:Proton Pumps; D015800:Protozoan Proteins; D012964:Sodium; D002118:Calcium
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