Clustering of Helicobacter pylori VacA in Lipid Rafts, Mediated by Its Receptor, Receptor-Like Protein Tyrosine Phosphatase β, Is Required for Intoxication in AZ-521 Cells

Helicobacter pylori VacA Enhances Prostaglandin E 2 Production through Induction of Cyclooxygenase 2 Expression via a p38 Mitogen-Activated Protein Kinase/Activating Transcription Factor 2 Cascade in AZ-521 Cells

“…We found recently that NPPB, which disrupts anion channels, or bafilomycin A1, which is a vacuolar-type H ϩ -ATPase inhibitor, inhibited VacA internalization followed by vacuolation but did not inhibit translocation of VacA to lipid rafts or VacA-induced activation of p38 MAP kinase in AZ-521 cells. In contrast, PI-PLC, which removes glycosylphosphatidylinositol (GPI)-anchored proteins, inhibited VacA translocation to lipid rafts, p38 MAP kinase activation, VacA internalization, and VacA-induced vacuolation (34). Consistent with the inhibition of p38 MAP kinase activation by PI-PLC treatment, PI-PLC inhibited VacA-induced COX-2 expression, whereas NPPB and bafilomycin A1 had no effect (Fig.…”

Helicobacter pylori VacA Induces Programmed Necrosis in Gastric Epithelial Cells

“…Most previous research on VacA-induced cell death was done with AGS or MKN28 human gastric epithelial cell lines or HeLa cells (16,30,44,54,70). Another human gastric epithelial cell line, AZ-521, has also been used extensively for studies of VacA, and several putative VacA receptors have been identified using this cell line (20,28,53,73,74). Previous studies have not investigated whether there are substantial differences in the susceptibility of different gastric cell lines to VacAinduced cell death.…”

“…The secreted 88-kDa VacA protein forms anion-selective membrane channels in planar lipid bilayers (18,50,64), and consequently, VacA is classified as a pore-forming toxin. Multiple receptors for VacA have been identified, including sphingomyelin, receptor protein-tyrosine phosphatase alpha ␣ (RPTP␣), and RPTP␤ on the surface of gastric epithelial cells and ␤2 integrin on the surface of T cells (28,35,53,62,73,74). Upon internalization by cells, VacA localizes to endosomal compartments (31) as well as to mitochondria (3,7,21,27,30,70).…”

“…AZ-521 cells have been used in previous studies for the identification of several VacA receptors and for studies of cellular alterations caused by VacA (20,28,53,(73)(74)(75). In the current study, we undertook an in-depth study of the process by which VacA causes death of these cells.…”

Ceramide and Toll-Like Receptor 4 Are Mobilized into Membrane Rafts in Response to Helicobacter pylori Infection in Gastric Epithelial Cells

“…With H. pylori, previous studies have shown that cholesterol-rich microdomains are required for VacA binding, delivery, and intoxication of cells (20,28,41,48). Our previous studies demonstrated that translocation of CagA and the internalization of H. pylori in gastric epithelial cells are reduced significantly upon treatment of cells with M␤CD, thereby decreasing the pathogenesis induced by this bacterium (30,32).…”