Molecules and Cells

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Fig. 1.

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Fig. 1. The endoplasmic reticulum (ER) is an essential organelle for protein synthesis, folding, and modification. The ER also plays important roles in lipid biosynthesis, calcium storage, and detoxification. ER homeostasis is disturbed by physiological and pharmacological stressors, and the resulting accumulations of misfolded proteins cause ER stress. ER stress triggers the UPR, which is an adaptive cellular response that is mediated by the three mammalian UPR transducers IRE1, PERK, and ATF6. Under conditions of ER stress, these proteins have various signal-mediated transcriptional effects that ameliorate ER stress. Proteins that are induced by IRE1, PERK, and ATF6 are involved in protein folding and ER expansion, and some attenuate protein translation. In addition, the UPR induces ERAD, which mediates degradation of unfolded proteins by proteasome. Under overwhelming conditions of ER stress, the UPR initiates apoptosis. IRE1, inositol-requiring enzyme 1; PERK, protein kinase R-like ER kinase; ATF6, activating transcription factor 6; ERAD, ER-associated degradation.
Mol. Cells 2018;41:705~716 https://doi.org/10.14348/molcells.2018.0241
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