title: Immunolocalization of an osteopontin-like protein in dense granules of Toxoplasma gondii tachyzoites and its association with the parasitophorous vacuole.
abstract: Toxoplasma gondii is an apicomplexan parasite infecting a broad host range, including humans. The parasite invades host cell by active penetration with the participation of its secretory organelles proteins during this process. Until now, only a limited number of secretory proteins have been discovered, and the effectors molecules involved in parasite invasion and survival are not well understood. Osteopontin (OPN) is a multifunctional glycophosphoprotein, secreted by different cell types, which is involved in various physiological and pathological events including cell signaling and survival. For the first time we demonstrated in this work by immunofluorescence and immunoelectron microscopy approaches the localization of an OPN-like protein in dense granules of extracellular T. gondii tachyzoites. Western blotting and RT-PCR confirmed this protein expression by the parasites. Our results also showed, after macrophage invasion, an intense positive labeling for OPN-like protein at the sub-apical portion of tachyzoites, the site of dense granules secretion, and the localization of this protein at the parasitophorous vacuole membrane. These data suggest that dense granules secrete an OPN-like protein, and we speculate that this protein participates during the parasite interaction process with host cells and parasitophorous vacuole formation.
authors.affiliation: Laboratório Cultura de Células, Departamento de Histologia e Embriologia, IB, Universidade do Estado do Rio de Janeiro, UERJ, Av. Prof. Manoel de Abreu 444, Rio de Janeiro, RJ, Brazil.
authors.forename: Erika
authors.initials: E
authors.lastname: Cortez
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Stumbo
authors.forename: Roberta
authors.initials: R
authors.lastname: Saldanha-Gama
authors.forename: Christina Gaspar
authors.initials: CG
authors.lastname: Villela
authors.forename: Christina
authors.initials: C
authors.lastname: Barja-Fidalgo
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Rodrigues
authors.forename: Maria
authors.initials: M
authors.lastname: das Graças Henriques
authors.forename: Marlene
authors.initials: M
authors.lastname: Benchimol
authors.forename: Helene S
authors.initials: HS
authors.lastname: Barbosa
authors.forename: Luis Cristóvão
authors.initials: LC
authors.lastname: Porto
authors.forename: Laís
authors.initials: L
authors.lastname: Carvalho
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003594:Cytoplasmic Granules / Q000737:chemistry*; D015870:Gene Expression; D007425:Intracellular Membranes / Q000737:chemistry; D017737:Macrophages, Peritoneal / Q000469:parasitology; D051379:Mice; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D053495:Osteopontin / Q000032:analysis*; D015800:Protozoan Proteins / Q000032:analysis*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014122:Toxoplasma / Q000737:chemistry*; D014617:Vacuoles / Q000737:chemistry* / Q000469:parasitology*
chemical_list: D015800:Protozoan Proteins; D012333:RNA, Messenger; D053495:Osteopontin