Fig. 1.

Schema of endoplasmic reticulum (ER) stress and unfolded protein response (UPR) signaling. Activation of the UPR leads to a transient translational inhibition, followed by the activation of transcription of ER molecular chaperones and the degradation of the unfolded proteins accumulated in the ER [ER-associated degradation (ERAD)]. If these strategies fail, cells undergo ER stress-induced apoptosis. Ask1 apoptosis signal-regulating kinase 1, ATF4 activating transcription factor 4, CHOP C/EBP homologous protein, JNK c-jun N-terminal kinase, RIP regulated intramembrane proteolysis, TRAF2 TNF receptor-associated factor 2, XBP1 X-box binding protein 1, P phosphorylation