Systematic mutagenesis of the <i>Helicobacter pylori cag</i> pathogenicity island: essential genes for CagA translocation in host cells and induction of interleukin‐8

Fischer, Wolfgang; Puls, Jürgen; Buhrdorf, Renate; Gebert, Bettina; Odenbreit, Stefan; Haas, Rainer

doi:10.1046/j.1365-2958.2003.03406.x

Cited by 98 publications

(199 citation statements)

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“…Coupling proteins are thought to recruit their cognate effector proteins to the secretion apparatus, thus conferring substrate specificity upon the secretion process (Gilmour et al ., 2003; Llosa et al ., 2003). As the H. pylori coupling protein homologue Cagβ (HP524) is dispensable for Cag‐dependent IL‐8 induction and therefore for building up the secretion apparatus, but necessary for CagA translocation (Fischer et al ., 2001), a similar role in recognition of the CagA translocation signal might be expected.…”

Section: Discussionmentioning

confidence: 99%

“…The purified fusion protein was used to raise the polyclonal rabbit antiserum AK268. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and Western blotting was performed as described (Fischer et al ., 2001). For the development of Western blots, nitrocellulose filters were blocked with 3% BSA in TBS (50 mM Tris‐HCl, pH 7.5, 150 mM NaCl) and incubated with the respective antisera at a dilution of 1:1000–1:5000.…”

Section: Methodsmentioning

confidence: 99%

“…It is currently unknown what the exact function of the CagA protein in the infectious process is, but the presence of the cag pathogenicity island encoding both the Cag type IV secretion apparatus and the CagA protein is a feature of the so‐called type I H. pylori strains, which are correlated with the development of more severe forms of disease such as peptic ulcers, mucosa‐associated lymphoid tissue (MALT) lymphoma or adenocarcinoma (Peek and Blaser, 2002; Suerbaum and Michetti, 2002; Blaser and Atherton, 2004; Rieder et al ., 2005). The Cag type IV secretion system does not contain readily identifiable homologues to all VirB/D4 components, but 18 genes on the cag pathogenicity island have been identified as necessary for CagA translocation (Fischer et al ., 2001). Of these, only 14 genes seem to encode components of the secretion apparatus, as they are necessary for another Cag‐induced phenotype, the induction of interleukin (IL)‐8 secretion from epithelial cells.…”

Section: Introductionmentioning

confidence: 99%

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A C‐terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein

Hohlfeld¹,

Pattis²,

Puls³

et al. 2006

Molecular Microbiology

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108

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SummaryType IV secretion systems are increasingly recognized as important virulence determinants of Gramnegative bacterial pathogens. While the examination of several type IV-secreted proteins suggested that their secretion depends on C-terminal signals, the nature of these signals and their conservation among different systems remain unclear. Here, we have characterized the secretion signal of the Helicobacter pylori CagA protein, which is translocated by the Cag type IV secretion apparatus into eucaryotic cells. The production of fusion proteins of CagA and green fluorescent protein (GFP) did not result in translocation of GFP to epithelial cells, but a fusion of GFP with the CagA C-terminus exerted a dominant-negative effect upon wild-type CagA translocation. We show that CagA translocation depends on the presence of its 20 C-terminal amino acids, containing an array of positively charged residues. Interestingly, these positive charges are neither necessary nor sufficient for CagA translocation, but replacing the C-terminal region of CagA with that of other type IV-secreted proteins reconstitutes CagA translocation competence. Using a novel type IV translocation assay with a phosphorylatable peptide tag, we show that removal of the Nterminal part of the CagA protein renders the protein translocation-incompetent as well. Thus, the Cag type IV secretion system seems to diverge from other systems not only with respect to its composition and architecture, but also in terms of substrate recognition and transport.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A C‐terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein

Hohlfeld¹,

Pattis²,

Puls³

et al. 2006

Molecular Microbiology

Self Cite

108

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“…The cag PAI‐encoded factor CagD was investigated and its crystal structure was determined [27]. In contradiction with previous findings [28], CagD was identified as an essential component of the T4SS that is required for CagA translocation into host epithelial cells, although not absolutely necessary for pilus assembly.…”

Section: Helicobacter Pylori Virulence Factorsmentioning

confidence: 98%

Pathogenesis of Helicobacter pylori Infection

2009

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Helicobacter pylori induces chronic inflammation of the gastric mucosa, but only a proportion of infected individuals develop peptic ulcer disease or gastric carcinoma. Reasons underlying these observations include differences in bacterial pathogenicity as well as in host susceptibility. Numerous studies published in the last year provided new insight into H. pylori virulence factors, their interaction with the host and consequences in pathogenesis. These include the role of bacterial genetic diversity in host colonization and persistence, outer membrane proteins and modulation of adhesin expression, new aspects of VacA functions, and CagA and its phosphorylation‐dependent and ‐independent cellular effects. This article will also review the recent novel findings on the interactions of H. pylori with diverse host epithelial signaling pathways and events involved in the initiation of carcinogenesis, including genetic instability and dysregulation of DNA repair.

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“…This inflammatory response appears to be mediated by TLR2, because the neutrophil‐activating protein of H. pylori induces IL‐12 and IL‐23 production from antigen‐presenting cells via activation of TLR2 64 . Production of IL‐8 is also upregulated by H. pylori in a TLR2‐dependent manner 65 . Cytotoxin‐associated gene A (Cag A), a virulence factor of H. pylori associated with higher rates of ulcers, precancerous change and gastric cancer, 66 has been shown to cause higher levels of IL‐8 production.…”

Section: Tlrs In the Pathogenesis Of Human Diseasementioning

confidence: 99%

Toll‐like receptors and their role in gastrointestinal disease

Testro

Visvanathan

2009

J of Gastro and Hepatol

122

109

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The innate immune response to invading pathogens is centred upon a family of non-clonal, germline-encoded pattern recognition receptors (PRRs), the Toll-like receptors (TLRs). These provide specificity for a vast range of microbial pathogens, and offer an immediate anti-microbial response system. Thirteen mammalian TLRs have been described; 10 are expressed in humans, each responsible for the recognition of distinct, invariant microbial structures originating from bacteria, viruses, fungi and protozoa. The two most thoroughly studied are TLR4 and TLR2, the PRRs for Gram-negative and Gram-positive bacterial products, respectively. TLR4 is also the major receptor recognising endogenous ligands released from damaged or dying cells. Activation of a TLR by its relevant ligand rapidly ignites a complex intracellular signaling cascade that ultimately results in upregulation of inflammatory genes and production of proinflammatory cytokines, interferons and recruitment of myeloid cells. It also stimulates expression, upon antigen presenting cells, of co-stimulatory molecules required to induce an adaptive immune response. Whilst a robust TLR response is critical for survival and defence against invading pathogens, inappropriate signaling in response to alterations in the local microflora environment can be detrimental. Such 'unhelpful TLR responses' could form the basis for a large number of gastrointestinal and liver disorders, including inflammatory bowel disease, viral hepatitis, autoimmune liver diseases and hepatic fibrosis. As our understanding of TLRs expands, the pathogenesis of a number of gastrointestinal disorders will be further elucidated, and this offers potential for specific therapies aimed directly at TLR signaling.

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Systematic mutagenesis of the Helicobacter pylori cag pathogenicity island: essential genes for CagA translocation in host cells and induction of interleukin‐8

Cited by 98 publications

References 1 publication

A C‐terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein

A C‐terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein

Pathogenesis of Helicobacter pylori Infection

Toll‐like receptors and their role in gastrointestinal disease

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