GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Aflagellated mutants of Helicobacter pylori generated by genetic transformation of naturally competent strains using transposon shuttle mutagenesis (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Three out of 10 Helicobacter pylori clinical isolates were found to be naturally competent for genetic transformation to streptomycin resistance by chromosomal DNA extracted from a spontaneous streptomycin-resistant H. pylori mutant. The frequency of transformation varied between 5 × 10−4 and 4 × 10−6, depending on the H. pylori isolate used. Transposon shuttle mutagenesis based on this natural competence was established using the flagellin gene flaA as the target. The cloned flaA gene was interrupted by insertion of TnMax1, a mini-Tn1721 transposon carrying a modified chloramphenicol-acetyltransferase gene, the catGC cassette. Natural transformation of competent H. pylori strains with plasmid constructs harbouring a catGC-inactivated flaA gene resulted in chloramphenicol-resistant transformants at an average frequency of 4 × 10−5. Southern hybridization experiments confirmed the replacement of the chromosomal H. pylori flaA gene by the cat-inactivated cloned gene copy via homologous recombination resulting in allelic exchange. Phenotypic characterization of the mutants demonstrated the absence of flagella under the electron microscope and the loss of bacterial motility. Immunoblots of cell lysates of the H. pylori mutants with an antiserum raised against the C-terminal portion of recombinant H. pylori major flagellin (FlaA) confirmed the absence of the 54kDa FlaA protein. This efficient transposon shuttle mutagenesis procedure for H. pylori based on natural competence opens up new possibilities for the genetic assessment of putative H. pylori virulence determinants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01618.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Generalized transposon shuttle mutagenesis in Neisseria gonorrhoeae: a method for isolating epithelial cell invasion-defective mutants (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 12 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: One requirement for the invasion of, and tight adherence to, human epitheiial cells by Neisseria gonorrhoeae is the synthesis of distinct opacity (Opa) outer membrane proteins, encoded by a family of phase-variable chromosomal genes. However, cloning and surface expression of invasion-promoting Opas in Escherichia coli is not sufficient for the efficient invasion of epithelial cells: additional factors besides Opa may be involved in this process. Using the phoA mini-transposon TnMax4, a library of gonococcal mutants affected in the expression of genes encoding exported proteins was generated through shuttle mutagenesis. Of a total of 608 PhoA+ plasmid clones identified in E. coli E145 approximately 40% were used successfully in transforming N. gonorrhoeae and in activating the corresponding chromosomal genes. Gonococci producing the invasion-promoting Opa50 served as the genetic background to identify 51 mutants unable to enter Chang human epithelial cells. We expect some of these mutations affect the interaction of N. gonorrhoeae with epithelial cells directly, while other mutants may carry defects in general house-keeping, secretory and/or regulatory determinants. In some mutants the loss of invasiveness appears to be due to a negative dominant effect of the PhoA+ fusions produced in these mutants. Some of the identified genes display a phase-variation phenomenon in E. coli and several genes are found in multiple copies in N. gonorrhoeae and/or present only in pathogenic Neisseria species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb01068.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    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
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Neisseria gonorrhoeae reverse transcriptase activity does not mediate pilin gene conversion (1997)
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 24 (1997), 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.1365-2958.1997.3681707.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Interaction of two variable proteins (PilE and PilC) required for pilus-mediated adherence of Neisseria gonorrhoeae to human epithelial cells (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Pili confer the initial ability of Neisseria gonorrhoeae to bind to epithelial cells. Pilin (PilE), the major pilus subunit, and a minor protein termed PilC, reportedly essential for pilus biogenesis, undergo intra-strain phase and structural variation. We demonstrate here that at least two different adherence properties are associated with the gonococcal pili: one is specific for erythrocytes, which is virtually unaffected by PilE variation, and another is specific for epithelial cells, and is modulated in response to the variation of PilE. Based on this finding, mutants of a recA - strain were selected that had lost the ability to bind to human cornea epithelial cells (A-) but retained the ability to form pili (P+) and to agglutinate human erythrocytes (H+). The adherence-negative mutants failed to produce detectable levels of PMC1 or PilC2 proteins, representing pilC phase variants generated in the absence of RecA. The A-pilC phase variants were indistinguishable from their A+parents and spontaneous A+ revertants with regard to the amount of PilE produced and its electrophoretic mobility, the degrees of piliation and haemagglutination, and the pilE nucleotide sequence. These data demonstrate a central role for PilC in pilus-mediated adherence of N. gonorrhoeae to human epithelial cells and further indicate that neither PNC1 nor PilC2 is obligatory for the assembly of gonococcal pili.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb02211.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Tetrapac (tpc), a novel genotype of Neisseria gonorrhoeae affecting epithelial cell invasion, natural transformation competence and cell separation (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We characterized a novel mutant phenotype (tetrapac, tpc) of Neisseria gonorrhoeae (Ngo) associated with a distinctive rough-colony morphology and bacterial growth in clusters of four. This phenotype, suggesting a defect in cell division, was isolated from a mutant library of Ngo MS11 generated with the phoA minitransposon TnMax4. The tpc mutant shows a 30% reduction in the overall murein hydrolase activity using Escherichia coli murein as substrate. Tetrapacs can be resolved by co-cultivation with wild-type Ngo, indicating that Tpc is a diffusible protein. Interestingly, Tpc is absolutely required for the natural transformation competence of piliated Ngo. Mutants in tpc grow normally, but show a ∼ 10-fold reduction in their ability to invade human epithelial cells. The tpc sequence reveals an open reading frame of ∼1 kb encoding a protein (Tpc) of 37kDa. The primary gene product exhibits an N-terminal leader sequence typical of lipoproteins, but palmitoylation of Tpc could not be demonstrated. The ribosomal binding site of tpc is immediately downstream of the translational stop codon of the folC gene coding for an enzyme involved in folic acid biosynthesis and one-carbon metabolism. The tpc gene is probably co-transcribed from the folC promoter and a promoter located within the folC gene. The latter promoter sequence shares significant homology with E. coli gearbox consensus promoters. All three mutant phenotypes, i.e. the cell separation defect, the transformation deficiency and the defect in cell invasion can be restored by complementation of the mutant with an intact tpc gene. To some extent the tcp phenotype is reminiscent of iap in Listeria, lytA in Streptococcus pneumoniae and lyt in Bacillus subtilis, all of which are considered to represent murein hydrolase defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02479.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...