5, first row). An analogous pattern was seen for CagA-∆N-transfected cells (Fig. 5, second row). In cells transfected with CagA-∆C, an evident cytoplasmic distribution of CagA (red) was seen. On the other hand, hardly any GM1 co-localized signal was detected in the plasma membrane (Fig. 5, third row). These observations support that CagA CTD
containing the EPIYA repeats is important for CagA tethering to the membrane raft microdomains. Several lines of evidence suggest that tethering of CagA to membrane-associated components is crucial for its subsequent functions: (i) following H. pylori infection, translocated CagA binds to raft-associated SFKs and undergoes tyrosine phosphorylation in the EPIYA motifs (Stein et al., 2002); (ii) CagA associates with the epithelial tight-junction scaffolding protein ZO-1 (Amieva selleck chemicals llc et al.,
2003); (iii) CagA interacts with membrane-externalized phosphatidylserine (PS) to initiate its entry into cells in epithelial cells (Murata-Kamiya et al., 2010); and (iv) depletion of cellular cholesterol blocks internalization of CagA into host cells (Lai et al., 2008). Of note, those identified CagA partners including c-Src (Lai et al., 2008), ZO-1 (Nusrat et al., 2000), and PS (Pike et al., 2002) have been click here shown to associate with DRMs. In addition to CagA, the H. pylori TFSS component CagL was found to bind and activate α5β1 integrin (Kwok et al., 2007), which is abundantly localized in cholesterol-rich microdomains (Leitinger & Hogg, 2002). This interaction was further demonstrated to trigger the delivery of peptidoglycans
across the cell membrane, resulting in the induction of NF-κB and IL-8 responses in the epithelial cells (Hutton et al., 2010). Collectively, these results suggest that TFSS, as well as internalized CagA, can reside primarily in cholesterol-enriched microdomains, where they interact old with various signaling molecules, inducing multiple cellular responses, including IL-8 secretion, cell motility, proliferation, and polarity. Our study shows that the CTD of CagA containing EPIYA repeats, either ABC-type (Western type) or AABD-type (East Asian type), is important for raft tethering and for IL-8 induction in AGS cells. Mutants that lacked the CTD lost their normal ability to associate with membrane rafts, in accord with the finding from Higashi et al. (Higashi et al., 2005). In polarized madin-darby kidney cells (MDCK), however, the N-terminal rather than the C-terminal region of CagA tethered to the cell–cell junctions (Bagnoli et al., 2005). Of note, a recent report using polarized and non-polarized cells to demonstrate that CagA utilized at least two distinct mechanisms for membrane association, relying on the status of epithelial polarity (Murata-Kamiya et al., 2010).