EIF2AK2 and nutritional deficiency disease: Hulmi et al. (78) found that UPR/ER pathway indicators such as activated transcription factor-6 (ATF6), inositol requirement protein (IRE) 1α, and protein kinase R (PKR) -like endoplasmic reticulum kinase (PERK) protein were increased and muscle strength was decreased in a mouse model of malnutrition.