Abstract
The vacuolating cytotoxin (VacA) is one of the major virulence factors of Helicobacter pylori (H. pylor), which may cause chronic gastritis, peptic ulcer and gastric cancer. In this study, p37, the principle catalytic domain of VacA was manipulated and expressed in Chinese hamster ovary cells (CHO-K1) to identify the mammalian cellular targets of the virulence factor. The p37 gene, derived from H. pylori strain 26695, was cloned into a mammalian expression vector pEGFP-N3 in a manner that p37 was expressed as a chimeric protein of green fluorescent protein (GFP). It was found that expression of p37-GFP, which localized mainly in the cytoplasm, was accompanied with a significant reduction of cell viability as determined by trypan blue exclusion assay. This observation was further supported by cell proliferation assay and the other analyses more specific to apoptosis. Deletion of the N-terminal 32 residues of p37 significantly abrogated the cytotoxicity of p37. This is consistent with the previous observation by other investigators that the N-terminal region is required for cytotoxicity of VacA. Furthermore, p37 but not the N-terminal truncate version, in the immunoprecipitation experiment, could interact with a cellular target with 70 kDa in molecular weight. In conclusion, p37 of VacA may interact with intracellular protein(s) and induce cell apoptosis.