The endoplasmic reticulum (ER) is the site of synthesis and folding of membrane and secretory proteins. Stringent quality control ensures that only correctly folded proteins exit the ER, while unfolded or misfolded proteins are retained and degraded. A number of biochemical and physiological stimuli can lead to the accumulation of aberrantly folded proteins in the ER. To cope with the stress of accumulated misfolded proteins, the ER has evolved highly intricate and specific pathways involving the cytosol and nucleus, known as the unfolded protein response (UPR)....