2004 Fiscal Year Final Research Report Summary
The studies of Helicobacter pylori on the functions of effector protein and the mechanisms of gastric mucosa infection.
| Project/Area Number |
15390141
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Bacteriology (including Mycology)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SASAKAWA Chihiro The University of Tokyo, The Institute of Medical Science, Professor, 医科学研究所, 教授 (70114494)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Helicobacter pylori / Pathogenicity / Stomach / Secretion system / CagA |
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| Research Abstract |
1.To investigate the type IV secretion system (TFSS) apparatus on the surface of Helicobacter pylori, we focused on Cag-related proteins such as Hp0532 (VirB7), Hp0528 (VirB9) and Hp0527 (VirB10), since the proteins were all postulated to be associated with the outer membrane based on the localization of the corresponding homologous proteins of the TFSS of Agrobactenum tumefaciens. To investigate the protein localization in H.pylori, we prepared polyclonal antibodies against each of the Cag proteins. The filamentous structures on bacterium were found to be associated with the major components of TFSS by immunofluorescence and immunogold electron microscopy. Our results thus provide for the first time direct evidence that the H.pylori TFSS apparatus is a filamentous macromolecular complex protruding from the bacterial envelope [Cell.Microbiol.(2003) 5, 395-404].
2.H.pylori deliver the CagA protein into host cells and are associated with peptic ulcer disease and gastric carcinoma. Injecte
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d CagA targets several host proteins including Grb2, SHP-2 and Csk, that are linked to changes in the structure and function of gastric epithelial cells. We identified that CagA binds Crk adaptor proteins, and its interaction plays a critical role in promoting cell scattering. The responses induced by H.pylori infection were significantly diminished when blocked Crk function by the over expression of dominant negative Crk or by the knockdown of endogenous Crk with RNAi treatment. The similar inhibitory effects were also observed when inhibited H-Ras, Rap1 or Rac1 involving in downstream of Crk signaling. Thus, the versatile Crk-mediated CagA activity can commit various signaling pathways in gastric epithelium.
3.We investigated the apoptosis of gastric epithelial cells infected with H, pylori and found that CagA that were injected into the host cell could prevent the infected cells from apoptosis. By using the various kinase inhibitors and siRNA techniques, it was suggested that the MAPK activation of infected cells by CagA could associate with the inhibitory effects of apoptosis.
These data suggest that CagA protein could induce the up regulation of signal cascade of the infected cells during long-term H.pylori infection, that would be unbalanced programd cell death and proliferation of the normal gastric cells, leading to the onset and malignancy of various gastric diseases. Less
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