ABSTRACT
Phorbol 12-myristate 13-acetate (PMA) induces differentiation of human leukemic HL-60 cells into cells with macrophage-like characteristics and enhances the susceptibility of HL-60 cells to the Helicobacter pylori VacA toxin (de Bernard, M., Moschioni., M., Papini, E., Telford, J. L., Rappuoli, R., and Montecucco, C. (1998) FEBS Lett. 436, 218-222). We examined the mechanism by which HL-60 cells acquire sensitivity to VacA, in particular, looking for expression of RPTPbeta, a VacA-binding protein postulated to be the VacA receptor (Yahiro, K., Niidome, T., Kimura, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Imagawa, K., Wada, A., Moss, J., and Hirayama, T. (1999) J. Biol. Chem. 274, 36693-36699). PMA induced expression of RPTPbeta mRNA and protein as determined by RNase protection assay and indirect immunofluorescence studies, respectively. Vitamin D(3) and interferon-gamma, which stimulate differentiation of HL-60 cells into monocyte-like cells, also induced VacA sensitivity and expression of RPTPbeta mRNA, whereas 1. 2% Me(2)SO and retinoic acid, which stimulated the maturation of HL-60 into granulocyte-like cells, did not. RPTPbeta antisense oligonucleotide inhibited induction of VacA sensitivity and expression of RPTPbeta. Double immunostaining studies also indicated that newly expressed RPTPbeta colocalized with VacA in PMA-treated HL-60 cells. In agreement with these data, BHK-21 cells, which are insensitive to VacA, when transfected with the RPTPbeta cDNA, acquired VacA sensitivity. All data are consistent with the conclusion that acquisition of VacA sensitivity by PMA-treated HL-60 cells results from induction of RPTPbeta, a protein that functions as the VacA receptor.
Subject(s)
Bacterial Proteins/toxicity , Cell Differentiation/physiology , Gene Expression Regulation , Helicobacter pylori , Nerve Tissue Proteins/genetics , Protein Tyrosine Phosphatases/genetics , Vacuoles/drug effects , Cell Differentiation/drug effects , Cell Survival/drug effects , Cholecalciferol/pharmacology , HL-60 Cells , Humans , Interferon-gamma/pharmacology , Kinetics , Oligonucleotides, Antisense/pharmacology , Receptor-Like Protein Tyrosine Phosphatases, Class 5 , Receptors, Cell Surface/genetics , Tetradecanoylphorbol Acetate/pharmacology , Thionucleotides/pharmacology , Transcription, Genetic , Tretinoin/pharmacologyABSTRACT
To investigatie a potential mechanism of how Helicobacter pylori establishes infection, we purified a lot of vacuolating toxin (VacA) from supernatant of H. pylori ATCC49503 (tox+ strain 60190). We used an antibody which was prepared by immunizing rabbits with a synthetic peptide consisting of 16 amino acids reflecting a portion (Glu69-Arg83) of amino acid sequence of Vac A. VacA caused vacuoles in human gastric cancer cell lines AZ-521 AGS, and monkey kidney cell line COS-7, but not human promyeloblastic cell line HL-60. By immunoprecipitation analysis using anti VacA antibody, a biotinylated cell surface protein of 140kDa (p140) was precipitated only when the lysates of VacA-susceptible cells were incubated with VacA but not with inactivated VacA, indicating the association of p140 with VacA.
Subject(s)
Bacterial Proteins/metabolism , Bacterial Toxins/metabolism , Helicobacter pylori/metabolism , Membrane Proteins/metabolism , Stomach Neoplasms/metabolism , Animals , HL-60 Cells , Haplorhini , Humans , Protein Binding , Rabbits , Tumor Cells, CulturedABSTRACT
To characterize Ser1029 in STaR at a consensus sequence of phosphorylation site by PKC, two mutants of mS1029A with replacement of Ser1029 to Ala1029 and C delta 1029 lacking 22 amino acids including Ser1029 were prepared. Preincubation of the wild type-STaR (wt-STaR) transfectant with 1 microM PMA caused additional STa-mediated guanylyl cyclase (GC) activation compared to control, whereas the mS1029A- and C delta 1029-transfected cells did not show a similar enhanced GC activation by PMA. After metabolic labeling with [32P]phosphate, transfected cells with wt-STaR and mutants were incubated with 1 microM PMA. Subsequent 32P-radiolabeled proteins were immunoprecipitated using anti-STaR antibody, and analyzed by autoradiography after separation on SDS-PAGE. The immunoprecipitated wt-STaR but not mS1029A and C delta 1029 had a significant radioactivity. These results suggest that the effect of PMA on wt-STaR transfectants may be caused by phosphorylation of Ser1029. The C delta 1012 mutant, with further truncation (Gln1012-Phe1050) of the carboxy terminus, did not show STa-mediated GC activation. Based on these data, these 17 amino acids (Gln1012-Ala1028), essential for signaling of GC activation by STa, have an abundance of basic amino acids which might be functionally influenced by phosphorylation of Ser1029.
