EIF2AK3 and viral infectious disease: Some members of this family of environmental stress sensors are: (i) PKR, a double strand RNA-dependent kinase, activated with viral infections, heat, and UV radiation; (ii) PERK/PEK, an ER protein that is active in response to the accumulation of misfolded proteins in the ER; (iii) GCN2, a sensor of intracellular amino acid levels that responds to amino acid deprivation; (iv) HRI, a hemo-regulated kinase that ensures the synthesis of globin chains and hemo during erythrocytes maturation.