title: ROP18 is a rhoptry kinase controlling the intracellular proliferation of Toxoplasma gondii.
abstract: Toxoplasma gondii is an obligate intracellular parasite for which the discharge of apical organelles named rhoptries is a key event in host cell invasion. Among rhoptry proteins, ROP2, which is the prototype of a large protein family, is translocated in the parasitophorous vacuole membrane during invasion. The ROP2 family members are related to protein-kinases, but only some of them are predicted to be catalytically active, and none of the latter has been characterized so far. We show here that ROP18, a member of the ROP2 family, is located in the rhoptries and re-localises at the parasitophorous vacuole membrane during invasion. We demonstrate that a recombinant ROP18 catalytic domain (amino acids 243-539) possesses a protein-kinase activity and phosphorylate parasitic substrates, especially a 70-kDa protein of tachyzoites. Furthermore, we show that overexpression of ROP18 in transgenic parasites causes a dramatic increase in intra-vacuolar parasite multiplication rate, which is correlated with kinase activity. Therefore, we demonstrate, to our knowledge for the first time, that rhoptries can discharge active protein-kinases upon host cell invasion, which can exert a long-lasting effect on intracellular parasite development and virulence.
authors.affiliation: UMR 5539, Centre National de la Recherche Scientifique, Université de Montpellier 2, Montpellier, France.
authors.forename: Hiba
authors.initials: H
authors.lastname: El Hajj
authors.forename: Maryse
authors.initials: M
authors.lastname: Lebrun
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Arold
authors.forename: Henri
authors.initials: H
authors.lastname: Vial
authors.forename: Gilles
authors.initials: G
authors.lastname: Labesse
authors.forename: Jean François
authors.initials: JF
authors.lastname: Dubremetz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000502:physiology*; D015800:Protozoan Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D012542:Scattering, Radiation; D014122:Toxoplasma / Q000254:growth & development* / Q000472:pathogenicity; D014617:Vacuoles / Q000469:parasitology; D014774:Virulence; D014965:X-Rays
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins; C090555:ROP 2 protein, Toxoplasma gondii; D011494:Protein Kinases