Figure 5.

H. pylori infection of MKN28 cells results in reduced levels of p120 tyrosine phosphorylation. (A) MKN28 cells were cocultured with H. pylori strain 7.13 (MOI = 100) or medium alone. At defined time points, total protein was extracted, subjected to immunoprecipitation with an anti-p120 antibody (pp120), and analyzed by Western blot by using a total anti-phosphotyrosine antibody (pY99) or anti-phosphoantibodies specific to the p120 tyrosine residues 228, 96, or 291. Experiments were performed on at least three occasions. A representative blot is shown. Anti-p120 blots (pp120) served as normalization controls for MKN28 viability under different experimental conditions. As a negative control, 500 μg of total protein from uninfected and infected samples taken 6 h after infection was subjected to immunoprecipitation with an anti-c-myc antibody (9E10). (B) Densitometric analysis of multiple Western blot repetitions performed on at least three occasions. Graph represents percent total tyrosine phosphorylation as determined by Western blotting with pY99 antibody in infected versus uninfected cells. Error bars, SEM. *p < 0.05, **p < 0.001 versus uninfected cells treated with medium alone.