Type III secretion genes identify a putative virulence locus of <i>Chlamydia</i>

Hsia, Ru-ching; Pannekoek, Yvonne; Ingerowski, Eric; Bavoil, Patrik M.

doi:10.1046/j.1365-2958.1997.4701834.x

Cited by 175 publications

(137 citation statements)

References 61 publications

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“…The analysis also predicts that the C-terminal helix has an extended conformation that is highly reminiscent of the MxiH structure (11,12). Based on these predictions and in accordance with current chlamydial T3SS nomenclature, we tentatively designated CT666 as CdsF (for contact-dependent secretion protein F) (26).…”

Section: Resultsmentioning

confidence: 96%

“…It is clear, for example, that Chlamydia spp. express a type III secretion system (T3SS), which is active at all stages of the developmental cycle (18,26). The T3SS is essential for virulence and is used by a variety of gram-negative human pathogens, including Yersinia spp., Shigella spp., Salmonella spp., pathogenic Escherichia coli, and Pseudomonas spp., to mediate delivery of bacterial "effector" proteins directly into the host cell cytosol.…”

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confidence: 99%

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Bioinformatic and Biochemical Evidence for the Identification of the Type III Secretion System Needle Protein ofChlamydia trachomatis

et al. 2008

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Chlamydia spp. express a functional type III secretion system (T3SS) necessary for pathogenesis and intracellular growth. However, certain essential components of the secretion apparatus have diverged to such a degree as to preclude their identification by standard homology searches of primary protein sequences. One example is the needle subunit protein. Electron micrographs indicate that chlamydiae possess needle filaments, and yet database searches fail to identify a SctF homologue. We used a bioinformatics approach to identify a likely needle subunit protein for Chlamydia. Experimental evidence indicates that this protein, designated CdsF, has properties consistent with it being the major needle subunit protein. CdsF is concentrated in the outer membrane of elementary bodies and is surface exposed as a component of an extracellular needle-like projection. During infection CdsF is detectible by indirect immunofluorescence in the inclusion membrane with a punctuate distribution adjacent to membrane-associated reticulate bodies. Biochemical cross-linking studies revealed that, like other SctF proteins, CdsF is able to polymerize into multisubunit complexes. Furthermore, we identified two chaperones for CdsF, termed CdsE and CdsG, which have many characteristics of the Pseudomonas spp. needle chaperones PscE and PscG, respectively. In aggregate, our data are consistent with CdsF representing at least one component of the extended Chlamydia T3SS injectisome. The identification of this secretion system component is essential for studies involving ectopic reconstitution of the Chlamydia T3SS. Moreover, we anticipate that CdsF could serve as an efficacious target for anti-Chlamydia neutralizing antibodies.

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Section: Resultsmentioning

confidence: 96%

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confidence: 99%

Bioinformatic and Biochemical Evidence for the Identification of the Type III Secretion System Needle Protein ofChlamydia trachomatis

et al. 2008

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“…On the other hand, there is now accumulating evidence that pathogens harbour type III secretion systems that deliver effector proteins or enzymes essential for survival within cells. Four putative type III secretion genes from C. psittaci have recently been proposed to encode virulence factors because of sequence similarities to effector proteins of other bacteria (Hsia et al, 1997). Although export of these proteins to their ®nal destination (i.e.…”

Section: Discussionmentioning

confidence: 99%

Characterization and intracellular trafficking pattern of vacuoles containing Chlamydia pneumoniae in human epithelial cells

1999

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SummaryChlamydiae are obligate intracellular pathogens that reside within a membrane-bound vacuole throughout their developmental cycle. In this study, the intraphagosomal pH of Chlamydia pneumoniae (Cpn) was qualitatively assessed, and the intracellular fate of the pathogen-containing vacuole and its interaction with endocytic organelles in human epithelial cells were analysed using conventional immuno¯uores-cence and confocal microscopy. The pH-sensitive probes acridine orange (AO), LysoTracker (LyT) and DAMP did not accumulate in the bacterial inclusion. In addition, exposure of cells to ba®lomycin A1 (BafA1), a potent acidi®cation inhibitor, did not inhibit or delay chlamydial growth. The chlamydial compartment was not accessible to the¯uid-phase tracer Texas Red (TR)-dextran and did not exhibit any level of staining for the late endosomal marker cation-independent mannose-6-phosphate receptor (Ci-M6PR) or for the lysosomal-associated membrane proteins (LAMP-1 and -2) and CD63. In addition, transferrin receptor (TfR)-enriched vesicles were observed close to Cpn vacuoles, potentially indicating a speci®c translocation of these organelles through the cytoplasm to the vicinity of the vacuole. We conclude that Cpn, like other chlamydial spp., circumvents the host endocytic pathway and inhabits a non-acidic vacuole, which is dissociated from late endosomes and lysosomes, but selectively accumulates early endosomes.

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“…Genome sequencing of chlamydiae has determined that the organism encodes the structural components for a complete type III secretion apparatus (41)(42)(43). Type III injectosomes may provide the route by which chlamydia-derived proteins enter the host cell cytoplasm, similar to that exploited by Shigella flexneri and Salmonella typhimurium (44), and modulate cellular responses such as those involved in the activation of caspase-1 and secretion of IL-18.…”

Section: Discussionmentioning

confidence: 99%

Chlamydia trachomatis Infection of Epithelial Cells Induces the Activation of Caspase-1 and Release of Mature IL-18

Shen

Brunham

2000

The Journal of Immunology

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Th1 cells that secrete IFN-γ are particularly important in protective immunity against intracellular pathogens, including chlamydiae, and IL-18 together with IL-12 are strong inducers of IFN-γ secretion by CD4 T cells. Because epithelial cells are known to synthesize IL-18, we investigated the effects of Chlamydia trachomatis infection of human epithelial cell lines on IL-18 secretion. We confirmed that several human epithelial cell lines constitutively express pro-IL-18 and that C. trachomatis infection causes cells to secrete mature IL-18. This was observed for several different serovars and biovars of C. trachomatis. Chlamydia-induced secretion of IL-18 from epithelial cells was regulated at the posttranscriptional level and was dependent on the activation of caspase-1. IL-1α or other secreted factor(s) from chlamydia-infected epithelial cells as well as chlamydial structural component(s) were not involved in inducing IL-18 secretion. Activation of caspase-1 and increased secretion of mature IL-18 was correlated with chlamydial, but not with host protein synthesis. In contrast to epithelial cell lines, fibroblast cell lines constitutively expressed much lower levels of pro-IL-18 and did not secrete mature IL-18 after chlamydial infection even though caspase-1 was activated. Taken together, the results suggest that a chlamydia-derived factor(s) is essential for the secretion of mature IL-18 through caspase-1 activation in infected epithelial cells.

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Type III secretion genes identify a putative virulence locus of Chlamydia

Cited by 175 publications

References 61 publications

Bioinformatic and Biochemical Evidence for the Identification of the Type III Secretion System Needle Protein ofChlamydia trachomatis

Bioinformatic and Biochemical Evidence for the Identification of the Type III Secretion System Needle Protein ofChlamydia trachomatis

Characterization and intracellular trafficking pattern of vacuoles containing Chlamydia pneumoniae in human epithelial cells

Chlamydia trachomatis Infection of Epithelial Cells Induces the Activation of Caspase-1 and Release of Mature IL-18

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