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  • Blackwell Science Ltd  (14)
  • Springer  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Phosphorylation of tyrosine 972 of the Helicobacter pylori CagA protein is essential for induction of a scattering phenotype in gastric epithelial cells (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori colonizes the human stomach and is the causative agent of a variety of gastric diseases. After bacterial attachment, the H. pylori CagA protein is translocated into gastric epithelial cells and tyrosine phosphorylated. This process is associated with characteristic cytoskeletal rearrangements, resulting in a scatter factor-like (‘hummingbird’) phenotype. In this study, using a cagA mutant complemented with wild-type cagA and transiently expressing CagA in AGS cells, we have demonstrated that translocated CagA is necessary for rearrangements of the actin cytoskeleton to occur. Anti-phosphotyrosine immunoblotting studies and treatment of infected cells with phosphotyrosine kinase inhibitors suggested that not only translocation but also phosphorylation of CagA is important in this process. Transient expression of CagA–green fluorescent protein (GFP) fusion proteins and two-dimensional gel electrophoresis of CagA protein species demonstrated tyrosine phosphorylation in the C-terminus. Site-directed mutagenesis of CagA revealed that tyrosine residue 972 is essential for induction of the cellular phenotype. We have also demonstrated that translocation and phosphorylation of CagA is necessary but not sufficient for induction of the hummingbird phenotype in AGS cells, indicating the involvement of as yet unidentified bacterial factor(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02649.x
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  • 2
    Electronic Resource
    Electronic Resource
    Helicobacter pylori induces but survives the extracellular release of oxygen radicals from professional phagocytes using its catalase activity (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 38 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori can colonize the gastric epithelium of humans, leading to the induction of an intense inflammatory response with the infiltration of mainly polymorphonuclear leucocytes (PMNs) and monocytes. These professional phagocytes appear to be a primary cause of the damage to surface epithelial layers, and probably contribute to the pathogenesis associated with persistent H. pylori infections. We have shown previously that H. pylori adheres to professional phagocytes, but is not engulfed efficiently, suggesting an antiphagocytic escape mechanism that is dependent on the pathogen's type IV secretion system. Here, we show that H. pylori induces the generation and extracellular release of oxygen metabolites as a consequence of its attachment to phagocytic cells, but is capable of surviving this response. The catalase activity of H. pylori is apparently essential for survival at the phagocytes' cell surface. Opsonization of H. pylori leads to an increased burst, and the inhibition of bacterial protein synthesis to a decreased one. Ca2+ concentration, cytoskeleton rearrangement and protein kinase C (PKC) are involved in the H. pylori-induced oxidative burst in both monocytes and PMNs. This survival phenomenon has important implications for both the persistence of this important pathogen and the host tissue damage that accompanies persistent H. pylori infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02114.x
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  • 3
    Electronic Resource
    Electronic Resource
    Helicobacter pylori inhibits phagocytosis by professional phagocytes involving type IV secretion components (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Gastric infections by Helicobacter pylori are characteristically associated with an intense inflammation and infiltration of mainly polymorphonuclear lymphocytes (PMNs) and monocytes. The inflammatory response by infiltrated immune cells appears to be a primary cause of the damage to surface epithelial layers and may eventually result in gastritis, peptic ulcer, gastric cancer and/or MALT-associated gastric lymphoma. Our analysis of the interaction between H. pylori and PMNs and monocytes revealed that H. pylori inhibits its own uptake by these professional phagocytes. To some degree, this effect resembles antiphagocytosis by Yersinia enterocolitica. Increasing numbers of bacteria associated per cell are more efficient at blocking their own engulfment. In H. pylori, bacterial protein synthesis is necessary to block phagocytic uptake, as shown by the time and concentration dependence of the bacteriostatic protein synthesis inhibitor chloramphenicol. Furthermore, H. pylori appears broadly to inhibit the phagocytic function of monocytes and PMNs, as infection with H. pylori abrogates the phagocytes' ability to engulf latex beads or adherent Neisseria gonorrhoeae cells. This antiphagocytic phenotype depends on distinct virulence (vir) genes, such as virB7 and virB11, encoding core components of a putative type IV secretion apparatus. Our data indicate that H. pylori exhibits an antiphagocytic activity that may play an essential role in the immune escape of this persistent pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02089.x
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  • 4
    Electronic Resource
    Electronic Resource
    Potential role of two Helicobacter pylori relaxases in DNA transfer? (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01086.x
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  • 5
    Electronic Resource
    Electronic Resource
    PilC of Neisseria meningitidis is involved in class II pilus formation and restores pilus assembly, natural transformation competence and adherence to epithelial cells in PilC-deficient gonococci (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Type 4 pili produced by the pathogenic Neisseria species constitute primary determinants for the adherence to host tissues. In addition to the major pilin subunit (PilE), neisserial pili contain the variable PilC proteins represented by two variant gene copies in most pathogenic Neisseria isolates. Based upon structural differences in the conserved regions of PilE, two pilus classes can be distinguished in Neisseria meningitidis. For class I pili found in both Neisseria gonorrhoeae and N. meningitidis, PilC proteins have been implicated in pilus assembly, natural transformation competence and adherence to epithelial cells. In this study, we used primers specific for the pilC2 gene of N. gonorrhoeae strain MS11 to amplify, by the polymerase chain reaction, and clone a homologous pilC gene from N. meningitidis strain A1493 which produces class II pili. This gene was sequenced and the deduced amino acid sequence showed 75.4% and 73.8% identity with the gonococcal PilC1 and PilC2, respectively. These values match the identity value of 74.1% calculated for the two N. gonorrhoeae MS11 PilC proteins, indicating a horizontal relationship between the N. gonorrhoeae and N. meningitidispilC genes. We provide evidence that PilC functions in meningococcal class II pilus assembly and adherence. Furthermore, expression of the cloned N. meningitidis pilC gene in a gonococcal pilC1,2 mutant restores pilus assembly, adherence to ME-180 epithelial cells, and transformation competence to the wild-type level. Thus, PilC proteins exhibit indistinguishable functions in the context of class I and class II pili.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2631630.x
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  • 6
    Electronic Resource
    Electronic Resource
    Opa binding to cellular CD66 receptors mediates the transcellular traversal of Neisseria gonorrhoeae across polarized T84 epithelial cell monolayers (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have analysed the capacity of the 11 phase-variable, opacity-associated (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to mediate traversal across polarized monolayers of the human colonic carcinoma T84 cell line. Gonococci expressing either the heparan sulphate proteoglycan (HSPG) binding Opa protein (Opa50) or no Opa protein (Opa−) did not interact with the apical pole of T84 monolayers, whereas the 10 variant Opa proteins previously shown to bind CD66 receptors were found to mediate efficient gonococcal adherence and transepithelial traversal. Consistent with this, T84 cells were shown by reverse transcriptase–polymerase chain reaction (RT–PCR) and immunoblotting to co-express CD66a (BGP), CD66c (NCA) and CD66e (CEA). The recruitment of CD66 receptors by Opa-expressing gonococci indicates their involvement in mediating adherence to the surface of T84 cells, and these bacterial interactions could be inhibited completely using polyclonal antibodies cross-reacting with all of the CD66 proteins co-expressed on T84 cells. Consistent results were obtained when Opa proteins were expressed in Escherichia coli, suggesting that the Opa–CD66 interaction is sufficient to mediate bacterial traversal. Transcytosis of Opa-expressing N. gonorrhoeae or E. coli did not disrupt the barrier function of infected monolayers, as indicated by a sustained transepithelial electrical resistance (TEER) throughout the course of infection, and confocal laser scanning and electron microscopy both suggest a transcellular rather than a paracellular route of traversal across the monolayers. Parallels between the results seen here and previous work done with organ cultures confirm that T84 monolayers provide a valid model for studying neisserial interactions with the mucosal surface, and suggest that CD66 receptors contribute to this process in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01102.x
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  • 7
    Electronic Resource
    Electronic Resource
    A novel peptidoglycan-linked lipoprotein (ComL) that functions in natural transformation competence of Neisseria gonorrhoeae (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A novel peptidoglycan-linked lipoprotein (ComL) has been identified which is required for efficient transformation of Neisseria gonorrhoeae by species-related DNA. Although most mutations in comL appear to be lethal, transposon shuttle mutagenesis was successful in generating a single viable comL mutant of N. gonorrhoeae strain MS11. This mutant, N457, exhibits a cratered and crinkled colony morphology and grows slower than wild-type MS11. However, as indicated by electron microscopy, this retardation is due to a small bacterial size rather than to a decreased generation time of the mutant bacteria. Complementation of N457 with an intact comL gene via the Hermes shuttle system fully reconstitutes bacterial size, colony morphology, and transformation competence of the wild-type strain. comL is a single-copy gene and maps downstream of the previously described comA gene It is transcribed in the opposite direction, probably using the same transcriptional terminator. ComL has a predicted size of 29 kDa and is synthesized in Escherichia coli under the control of its native promoter, which is highly conserved with the E. coli promoter consensus sequence. The 5′ end of the coding sequence reveals a lipoprotein secretion signal shown to be functional by gene fusion with alkaline phosphatase (phoA′ ). In E. coli, cloned ComL can be labelled with [3H]-palmitic acid, thus demonstrating its lipoproteinaceous nature. Palmitoylated ComL appears to be covalently bound to the murein sacculus of E. coli and N. gonorrhoeae since it resists boiling in 4% sodium dodecyl sulphate and is released only by lysozyme treatment. Homologous counterparts of the comL gene are found in Neisseriameningitidis as well as in several non-pathogenic Neisseria species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.457984.x
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  • 8
    Electronic Resource
    Electronic Resource
    Common structural features of IgA1 protease-like outer membrane protein autotransporters (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020378.x
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  • 9
    Electronic Resource
    Electronic Resource
    Mutagenesis of the Neisseria gonorrhoeae porin reduces invasion in epithelial cells and enhances phagocyte responsiveness (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Porin (PorB), the major outer membrane protein of Neisseria gonorrhoeae, has been implicated in pathogenesis previously. However, the fact that porin deletion mutants are not viable has complicated investigations. Here, we describe a method of manipulating the porin gene site-specifically. N. gonorrhoeae MS11, which harbours the porB1B (P.1B) porin allele, was used to generate mutants carrying deletions in the surface loops 1 and 5. An 11-amino-acid deletion in loop 1 impaired Opa50-dependent invasion into human Chang epithelial cells, whereas loop 5 deletion exhibited no apparent phenotype. In a second approach, the complete gonococcal porB1B was replaced by the porBNla gene of Neisseria lactamica. Such mutants were unable to induce efficient uptake by epithelial cells but induced an enhanced respiratory response in HL60 phagocytic cells. The increased respiratory burst was accompanied by an enhanced phagocytic uptake of the mutant compared with the wild-type strain. Our data extend previous evidence for multiple central functions of PorB in the infection process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01230.x
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  • 10
    Electronic Resource
    Electronic Resource
    Differential Opa specificities for CD66 receptors influence tissue interactions and cellular response to Neisseria gonorrhoeae (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 26 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ability of all 11 variable opacity (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to interact directly with the five CD66 antigens was determined. Transfected HeLa cell lines expressing individual CD66 antigens were infected with recombinant N. gonorrhoeae and Escherichia coli strains expressing defined Opas. Based upon the ability of these bacteria to bind and invade and to isolate specifically CD66 antigens from detergent-soluble extracts of the corresponding cell lines, distinct specificity groups of Opa interaction with CD66 were seen. Defining these specificity groups allowed us to assign a specific function for CD66a in the Opa-mediated interaction of gonococci with two different target cell types, which are both known to co-express multiple CD66 antigens. The competence of individual Opas to interact with CD66a was strictly correlated with their ability to induce an oxidative response by polymorphonuclear neutrophils. The same Opa specificity was observed for the level of gonococcal binding to primary endothelial cells after stimulation with TNFα, which was shown to increase the expression of CD66a rather than CD66e. As CD66e alone is expressed on other target tissues of gonococcal pathogenicity, Opa variation probably contributes to the cell tropism displayed by gonococci.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.6342006.x
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