The Journal of Experimental Medicine
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© The Rockefeller University Press, 0022-1007/2000/2/593/ $5.00
The Journal of Experimental Medicine, Volume 191, Number 4, February 21, 2000 593-602

Original Article

Helicobacter pylori CagA Protein Can Be Tyrosine Phosphorylated in Gastric Epithelial Cells

Momoyo Asahia, Takeshi Azumab, Shigeji Itob, Yoshiyuki Itob, Hiroyuki Sutob, Yukifumi Nagaic, Misao Tsubokawad, Yumi Tohyamae, Shin Maedaf, Masao Omataf, Toshihiko Suzukig, and Chihiro Sasakawag
a Faculty of Nursing and Welfare, Fukui Prefectural University, Fukui 910-1195, Japan
b Second Department of Internal Medicine, Fukui Medical University, Fukui 910-1193, Japan
c Department of Biology, Fukui Medical University, Fukui 910-1193, Japan
d Tsubokawa Clinic, Fukui 910-0854, Japan
e Department of Laboratory Medicine and Clinical Sciences, Faculty of Medicine, Kyoto University, Kyoto 606-8397, Japan
f Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Tokyo 113, Japan
g Department of Bacteriology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan

Correspondence to: Momoyo Asahi, Faculty of Nursing and Welfare, Fukui Prefectural University, 4-1-1 Kenjojima, Matsuoka-cho, Yoshida-gun, Fukui 910-1195, Japan. Tel:81-776-61-6000 Fax:81-776-61-6016 E-mail:asahi{at}fpu.ac.jp.

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 [35S]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.

Key Words: bacterial infection, bacterial adhesion, bacterial protein, protein tyrosine kinase, signal transduction


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