ERN1 and Alzheimer disease: The levels of UPR-related proteins such as chaperone binding immunoglobulin protein (BiP), phosphorylated inositol-requiring enzyme 1 (p-IRE1α), p-eIF2α, activating transcription factor 4 (ATF4), or CHOP in AD mouse model were not significantly elevated as compared to the non-transgenic control mice.