The integrated stress response (ISR) is one of the most conserved cellular stress responses during mitochondrial dysfunction. The keys in the activation of ISR are the phosphorylation of eIF2α and subsequent induction of ATF4. The phosphorylation of eIF2α is caused by the activation of four specific serine/threonine kinases, which are Heme Regulated Inhibitor (HRI), Protein Kinase Ribonucleic…