Inactivation of Helicobacter pylori cagA gene affects motility

The cytotoxin-associated protein CagA is a Helicobacter pylori immunodominant antigen whose gene resides in the cag pathogenicity island. Our purpose was to determine if the disruption or deletion of cagA gene could have an effect on the expression of other proteins at the proteome level. We analyzed two H. pylori strains, 328 and G27 wild-type, bearing the cag pathogenicity island, and their respective isogenic cagA(-) mutants.

The proteomes of two H. pylori strains (328 and its isogenic mutant SPM328_DeltacagA) were resolved by two-dimensional electrophoresis and the digitalized images obtained were analysed both quantitatively and qualitatively. Peculiar spots of each strain were identified by mass spectrometry or by Western blotting.

The comparison between the proteome expression of an H. pylori cagA(+) strain and an isogenic mutant strain where the cagA gene was disrupted showed that, as well as the lack of expression of CagA, both flagellin A and flagellin B expressions were significantly decreased. The cagA(-) isogenic mutant was nonmotile. G27_DeltacagA, in which CagA was inactivated by gene deletion, was nonmotile as well respecting to motile G27 wild-type strain. Moreover, reintroduction of cagA in G27_DeltacagA restored motility.

Our results suggest that CagA could quantitatively influence flaA and flaB transcription or their subsequent translation and/or correct folding.