The endoplasmic reticulum (ER) is a continuous membrane system within the cytoplasm of eukaryotic cells. It is an important site for the synthesis, folding, modification, and transport of proteins. Perturbation of ER homeostasis through the accumulation of unfolded or misfolded proteins results in a stress condition, i.e., ER stress, and activates unfolded protein response (UPR). ER UPR (UPRER) instigates transcriptional and translational responses to relieve ER stress.

In animals, the ER UPR signaling pathway is initiated by three membrane-associated stress sensor proteins: inositol requiring enzyme 1α/β (IRE1), PKR-like ER kinase (PERK), and activating transcription factor 6α/β (ATF6). https://www.cd-biosciences...