Helicobacter pylori CagA protein can be tyrosine phosphorylated in gastric epithelial cells |
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| Authors: | Asahi M Azuma T Ito S Ito Y Suto H Nagai Y Tsubokawa M Tohyama Y Maeda S Omata M Suzuki T Sasakawa C |
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| Affiliation: | Faculty of Nursing and Welfare, Fukui Prefectural University, Fukui 910-1195, Japan. asahi@fpu.ac.jp |
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| Abstract: | ![]()
Attachment of Helicobacter pylori to gastric epithelial cells induces various cellular responses, including the tyrosine phosphorylation of an unknown 145-kD protein and interleukin 8 production. Here we show that this 145-kD protein is the cagA product of H. pylori, an immunodominant, cytotoxin-associated antigen. Epithelial cells infected with various H. pylori clinical isolates resulted in generation of tyrosine-phosphorylated proteins ranging from 130 to 145 kD in size that were also induced in vitro by mixing host cell lysate with bacterial lysate. When epithelial cells were infected with [(35)S]methionine-labeled H. pylori, a radioactive 145-kD protein was detected in the immunoprecipitates with antiphosphotyrosine antibody or anti-CagA (cytotoxin-associated gene A) antibody. Consistently, the 145-kD protein recognized by the anti-CagA and antiphosphotyrosine antibodies was induced in epithelial cells after infection of wild-type H. pylori but not the cagA::Km mutant. Furthermore, the amino acid sequence of the phosphorylated 145-kD protein induced by H. pylori infection was identical to the H. pylori CagA sequence. These results reveal that the tyrosine-phosphorylated 145-kD protein is H. pylori CagA protein, which may be delivered from attached bacteria into the host cytoplasm. The identification of the tyrosine-phosphorylated protein will thus provide further insights into understanding the precise roles of CagA protein in H. pylori pathogenesis. |
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| Keywords: | bacterial infection bacterial adhesion bacterial protein protein tyrosine kinase signal transduction |
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