title: Chlamydia trachomatis secretion of hypothetical protein CT622 into host cell cytoplasm via a secretion pathway that can be inhibited by the type III secretion system inhibitor compound 1.
abstract: Using antibodies raised with C. trachomatis fusion proteins, we localized a hypothetical protein encoded by the ORF ct622 in the cytoplasm of C. trachomatis-infected mammalian cells. The detection was specific since the antibody labelling of CT622 protein was removed by preabsorption with CT622 but not other fusion proteins. We similarly confirmed that CT621, a known secretion protein encoded by a hypothetical ORF downstream of ct622, was secreted into host cell cytosol. Proteins CT622 and CT621 displayed a similar secretion pattern, with both intra-inclusion and host cell cytosol localization, that was distinct from that of CPAF (chlamydial protease/proteasome-like activity factor). However, the expression and secretion kinetics differed significantly between CT622 and CT621: CT622 mRNA was detected at 2 h, protein at 6 h and secretion of protein into host cell cytoplasm at 36 h post-infection, while CT621 mRNA was detected at 8 h, protein at 16 h and secretion at 24 h. The secretion of both CT622 and CT621 was blocked by N'-(3,5-dibromo-2-hydroxybenzylidene)-4-nitrobenzohydrazide (compound 1), an inhibitor known to target the type III secretion system of bacteria. These results suggest that CT621 and CT622 may fulfil different functions during chlamydial intracellular growth. Further characterization of these proteins may generate important information for understanding chlamydial pathogenesis.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: Siqi
authors.initials: S
authors.lastname: Gong
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Lei
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: Xiaotong
authors.initials: X
authors.lastname: Chang
authors.affiliation: Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Belland
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhong
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002692:Chlamydia trachomatis / Q000187:drug effects / Q000378:metabolism* / Q000472:pathogenicity*; D003593:Cytoplasm / Q000737:chemistry / Q000382:microbiology; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000737:chemistry* / Q000382:microbiology*; D020869:Gene Expression Profiling; D006367:HeLa Cells; D006801:Humans; D006834:Hydrazines / Q000378:metabolism; D055571:Secretory Pathway / Q000187:drug effects; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D006834:Hydrazines; C515036:N'-(3,5-dibromo-2-hydroxybenzylidene)-4-nitrobenzohydrazide; D037521:Virulence Factors