Activation of the Unfolded Protein Response Is Required for Defenses against Bacterial Pore-Forming Toxin In Vivo
Figure 6
Schematic illustrating relationship between p38 MAPK, ire-1-xbp-1, and PFT defense pathways.
PFTs at the cell surface of epithelial cells activate p38 MAPK that activates IRE-1 that induces splicing of xbp-1, which then turns on defense against PFTs. Residual activation of xbp-1 targets in the absence of the p38 MAPK pathway suggests there might be p38-independent activation of the ire-1-xbp-1 pathway in response to PFT as well (not shown). Independent of IRE-1 activation, p38 MAPK can also activate TTM-2 and other PFT defenses. Tunicamycin, which causes the accumulation of unfolded proteins in the ER, activates IRE-1 via a mechanism independent of the PFT and p38 MAPK.