Analysis of translocation of the CagA protein and induction of a scattering phenotype in AGS cells infected with Helicobacter pylori.

OBJECTIVE To investigate whether the presence of structured CagA proteins in Western- and Eastern-type Helicobacter pylori (H. pylori) induces different incidences of gastric diseases. METHODS CagA and phosphorylated CagA were expressed in AGS gastric epithelial cells infected with wild type and mutant strains. The ability of individual CagA was determined by immunoprecipitation and Western blot assay. Morphological changes of these cells were observed under microscope to evaluate the appearance of elongation hummingbird phenotype. RESULTS The sizes of CagA proteins in different strains were different, and no phosphorylated CagA proteins were detected in wild-type strains. Meanwhile, the kinetics of CagA status in AGS infected with H. pylori was detected. The molecular weight of phosphorylated CagA with the same size of CagA proteins in H. pylori was different in infections with different wild-type strains. CagA and phosphorylated CagA increased in a time-dependent manner after the infection. The hummingbird phenotype with H. pylori for time-course was observed under microscope. Instead of HPK5 strain, the wild-type 26695 strain induced hummingbird phenotype in a time-dependent manner. CONCLUSION Translocation and phosphorylation of CagA are necessary, but not sufficient, for the induction of hummingbird phenotype in AGS cells.