ABSTRACT
<p><b>BACKGROUND</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>
Subject(s)
Humans , Amino Acid Sequence , Antigens, Bacterial , Chemistry , Physiology , Bacterial Proteins , Chemistry , Physiology , Blotting, Western , Cells, Cultured , Gastric Mucosa , Intracellular Signaling Peptides and Proteins , Molecular Sequence Data , Phenotype , Phosphorylation , Protein Tyrosine Phosphatase, Non-Receptor Type 11 , Protein Tyrosine Phosphatases , Metabolism , Repetitive Sequences, Amino Acid , Signal TransductionABSTRACT
<p><b>OBJECTIVE</b>To investigate the distribution of babA2 cagA and vacA genotypes of Helicobacter pylori (Hp) in chronic gastritis and peptic ulcer and to discuss the relationship between babA2, cagA and vacA genotypes of Hp and chronic gastritis and peptic ulcer.</p><p><b>METHODS</b>babA2, cagA genotypes and vacA subtype of 58 Hp strains isolated from patients of Zhejiang province with chronic gastritis or peptic ulcer were tested by polymerase chain reaction.</p><p><b>RESULTS</b>The positive rates of babA2, cagA, vacAs1a, vacA m1 and vacA m2 of 58 Hp strains were 87.9%, 100%, 93.1%, 1.7% and 65.5%, respectively. There were no significant differences between the positive rates of babA2, vacA s1a and vacA m2 genes of Hp strains isolated from patients with chronic gastritis and peptic ulcer.</p><p><b>CONCLUSION</b>The genotypes of Hp isolated from patients of Zhejiang province were predominatly babA2 positive, cagA positive and vacA s1a/m2. The relationships between babA2, cagA and vacA genotypes of Hp and chronic gastritis and peptic ulcer can not be identified.</p>