The Cell-Specific Phenotype of the Polymorphic vacA Midregion Is Independent of the Appearance of the Cell Surface Receptor Protein Tyrosine Phosphatase β

ABSTRACT There are two alleles, m1 and m2, of the midregion of the vacuolating cytotoxin gene (vacA) of Helicobacter pylori which code for toxins with different cell specificities. Here we describe the construction of five chimeric strains in which regions of vacA were exchanged between the two genotypes. By analyzing the toxicity of these strains for HeLa and RK13 cells we have confirmed that a 148-amino-acid region determines the phenotypic differences between the two forms of the protein and that this entire region is important for cytotoxicity. Furthermore, we have used our chimeric strains to investigate whether variations in the midregion of VacA have an effect on phorbol 12-myristate 13-acetate (PMA)-induced VacA sensitivity in HL-60 cells. The PMA-induced VacA sensitivity of HL-60 cells has been previously associated with the appearance of the cell surface receptor protein tyrosine phosphatase beta (RPTPβ). Our data indicate that both the m1 and m2 forms of VacA are able to utilize RPTPβ, and the cell-specific phenotype of the midregion is independent of the presence of RPTPβ. It appears that another as-yet-unidentified receptor exists in HL-60 cells that accounts for the m2 phenotype in this cell line. Also, by studying the effect of PMA on levels of RPTPβ in other cell lines and toxicity of VacA in these cell lines we have shown that RPTPβ does not play a major role in the vacuolation of HeLa cells.