The cyctoprotective endoplasmic reticulum (ER) stress mechanism [32]. The cyctoprotective endoplasmic reticulum (ER) stress mechanism [32]. BiP: immunoglobulin heavy chain-binding protein / 78 kDa glucose-regulated protein; IRE1: inositol-requiring protein 1; ATF: activating transcription factor; PERK: protein kinase R-like endoplasmic reticulum kinase; eIF: elongation initiation factor; XBP1: X-box binding protein 1; ERAD: ER-associated protein degradation; ROS: reactive oxygen species. Andreas Günther et al. Eur Respir Rev 2012;21:152-160 ©2012 by European Respiratory Society