title: Identification of a type IV secretion substrate of Brucella abortus that participates in the early stages of intracellular survival.
abstract: Brucella abortus, the aetiological agent of bovine brucellosis, is an intracellular pathogen whose virulence is completely dependent on a type IV secretion system. This secretion system translocates effector proteins into the host cell to modulate the intracellular fate of the bacterium in order to establish a secure niche were it actively replicates. Although much has been done in understanding how this secretion system participates in the virulence process, few effector proteins have been identified to date. We describe here the identification of a type IV secretion substrate (SepA) that is only present in Brucella spp. and has no detectable homology to known proteins. This protein is secreted in a virB-dependent manner in a two-step process involving a periplasmic intermediate and secretion is necessary for its function. The deletion mutant showed a defect in the early stages of intracellular replication in professional and non-professional phagocytes although it invades the cells more efficiently than the wild-type parental strain. Our results indicate that, even though the mutant was more invasive, it had a defect in excluding the lysosomal marker Lamp-1 and was inactivated more efficiently during the early phases of the intracellular life cycle.
authors.affiliation: Instituto de Investigaciones Biotecnológicas 'Dr. Rodolfo A. Ugalde', Instituto Tecnológico de Chascomús, IIB-INTECH, CONICET, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Döhmer
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Valguarnera
authors.forename: Cecilia
authors.initials: C
authors.lastname: Czibener
authors.forename: Juan E
authors.initials: JE
authors.lastname: Ugalde
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D002003:Brucella abortus / Q000235:genetics / Q000472:pathogenicity*; D002006:Brucellosis / Q000382:microbiology / Q000473:pathology; D002460:Cell Line; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006367:HeLa Cells; D006801:Humans; D051907:Lysosomal Membrane Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D037521:Virulence Factors / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D051907:Lysosomal Membrane Proteins; D037521:Virulence Factors; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1