based on the fact that activation of the ire-1-xbp-1 pathway leads to increased phospholipid biogenesis [34] . It is possible that the defensive role of the ire-1-xbp-1 pathway is to produce phospholipids that play a protective role against PFTs. Consistent with this, it has been shown that inhibiting the activation of SREBPs, the central regulators of membrane biogenesis, leads to hypersensitivity of mammalian cells to the PFT aerolysin [35] .