EIF2AK4 and viral infectious disease: Four distinct serine/threonine kinases can perform the eIF2α phosphorylation: PKR (interferon-induced double-stranded RNA-dependent eIF2α kinase, induced by viral infection), PERK (PKR-like endoplasmic reticulum resident kinase, induced by endoplasmic reticulum stress), GCN2 (general control nonderepressible 2, induced by amino acid starvation), and HRI (heme-regulated inhibitor kinase, induced by heme deficiency but also by various other stressors) (Costa-Mattioli and Walter, 2020; Bilen et al., 2022).