, 2008). Translocation of CagA and by which induced IL-8 production in infected AGS cells is also blocked by cholesterol depletion (Lai et al., 2008; Murata-Kamiya et al., 2010). The presence of a single Glu-Pro-Ile-Tyr-Ala (EPIYA) motif in the C-terminal region of CagA was shown to be crucial for membrane localization (Higashi et al., 2005). Delivery of CagA with more phosphorylation motifs was found to induce a higher level of phosphorylation in epithelial
cells, which may therefore influence Caspase activity the severity of the clinical outcomes (Argent et al., 2004). However, the detailed role of lipid rafts in membrane tethering of CagA remains to be elucidated. In this study, we investigated the effects of various CagA truncation mutants on the association between CagA and lipid rafts and on IL-8 induction. Our results provide evidence that the CagA C-terminal EPIYA-containing region is targeted to membrane rafts, which allows CagA-mediated induction of IL-8. Helicobacter pylori 26695 (ATCC 700392) was used as a reference strain and contains a cagA gene with three C-terminal EPIYA motifs (ABC-type) (Higashi et al., 2005). Clinical strain v669 was isolated from a patient with gastric cancer and contains a cagA gene with four C-terminal EPIYA motifs (AABD-type) (Lai et al., 2002). Helicobacter pylori strains
were recovered from frozen stocks on Brucella blood agar plates (Becton Dickinson). Construction of the cagA (∆CagA) and cagE (∆CagE) knockout strains were performed using the kanamycin resistance cassette (Kmr) from pACYC177 and the erythromycin resistance cassette (Eryr) from pE194, buy Venetoclax respectively, by the natural transformation method as we described previously (Lai et al., 2008). PCR and western blot analysis were employed to confirm the correct insertion of antibiotic resistance cassettes into the target genes. Various expression constructs encoding CagA truncation mutants were generated based on the H. pylori 26695 cagA sequence and v669 as illustrated in Fig. 3a. cagA fragments were amplified using PCR from H. pylori 26695 and v669 genomic DNA as described previously (Lai et al., crotamiton 2002). The CagA-ΔN mutant
was generated from strain 26695 by amplification of sequence encoding amino acids 645–1186 using primers CagA-CTD59F and CagA-CTDR (Table 1). The primers used for PCR introduced a BamHI site at the 5′ end and an XbaI site at the 3′ end. The BamHI–XbaI fragment was then ligated into pEF1 expression vector (Invitrogen). Similar procedures were used to obtain the 669CagA-ΔN mutant from strain v669 using primers CagA-CTD59F and CagA-CTDR. To generate the CagA-ΔC mutant, a fragment encoding amino acids 1–358 was amplified using primers CagA1-F and CagA-1R. The primers used for PCR introduced a BamHI site at the 5′ end and an EcoRI site at the 3′ end. The BamHI–EcoRI fragment was then inserted into pEF1 to derive pEF1-CagA1. A fragment encoding amino acids 357–707 was amplified using primers CagA2F and CagA2R.
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