EIF2AK4 and viral infectious disease: Besides ER stress, eIF2α phosphorylation serves as the regulatory hub of the so-called integrated stress response, which can also be initiated by three other serine/threonine eIF2α kinases in response to distinct stimuli including viral infection (via the double-stranded RNA-activated protein kinase, a.k.a. PKR), amino acid deprivation (via the general control nonderepressible 2, a.k.a. GCN2), and heme deficiency (via the heme-regulated eIF2α kinase, a.k.a. HRI) [6, 29].