It has been reported that eIF2α is phosphorylated by not only PERK activation during ER stress, but also other stress-response signaling molecules, such as general control nonderepressible 2, under conditions of amino acid starvation [55, 56], heme-regulated eIF2α kinase during iron deficiency [57], and protein kinase RNA during viral infection [58–60]. Here, EIF2AK4 is linked to nutritional disorder.