中华医学杂志（英文版）Issue(9)：1330-1333,4.
Biological activity of the virulence factor cagA of Helicobacter pylori
Biological activity of the virulence factor cagA of Helicobacter pylori
摘要
Abstract
Background China is one of the countries with the highest incidence of H. Pylori and more than 9090 isolates possessed the cagA gene. This study was to evaluate the biological activity of the H.pylori virulence factor cagA isolated from Chinese patients. Methods cagA DNA fragments were amplified from the genomic DNA and subsequently cloned into the mammalian expression vector for cell transfection and DNA sequencing. cagA protein, phosphorylated-tyrosine cagA and the complex of cagA precipitated with SHP-2 were identified respectively by western blot in the crude cell lysate from conditionally immortalized gastric epithelial cells at 48 hours after transfection with cagA DNA. In addition, the ability of induction of scattering phenotype was examined after transient expression of cagA in AGS cells. Results The C-terminal half of cagA contained only one repeated sequence and three tandem five-amino-acid motifs glutamic acid-proline-isoleucine-tyrosine-alanine (EPIYA). Moreover, the amino acid sequence of D2 region in repeated sequence was aspartic acid-phenylanaline-aspartic acid (D-F-D) which was significantly distinguished from the three repeated sequences and aspartic acid-aspartic adid-leucine (D-D-L) in the western standard strain NCTC11637. Western blot revealed that cagA became phosphorylated in tyrosine site and bound with SHP-2 after transient expression of cagA DNA in gastric epithelial cells. Transient expression of cagA in AGS cells showed that cagA was able to induce the elongation phenotype although to a lesser extent than western strains. Conclusions cagA perturbs cell signaling pathways by binding with SHP-2. However, significant difference exists in amino acid sequence and biological function of cagA in Chinese compared with those of western countries.关键词
Helicobacter pylori/cagA/tyrosine phosphorylation/tyrosine phosphatase 2 containing src homology 2/pathogenesisKey words
Helicobacter pylori/cagA/tyrosine phosphorylation/tyrosine phosphatase 2 containing src homology 2/pathogenesis分类
医药卫生引用本文复制引用
朱永良,郑树,钱可大,方平楚..Biological activity of the virulence factor cagA of Helicobacter pylori[J].中华医学杂志（英文版）,2004,(9):1330-1333,4.基金项目
This work was supported by grants from 863 National Foundation (2001AA227111) and 973 National Foundation (G1998051200). （2001AA227111）
