Eukaryotic translation initiation factor 2-alpha kinase 3 (PERK) (PERK)

The GRP78-PERK pathway is a fundamental branch of the Unfolded Protein Response (UPR) that monitors and responds to endoplasmic reticulum (ER) stress. Under homeostatic conditions, the ER chaperone GRP78 (also known as BiP) remains bound to the luminal domain of the sensor kinase PERK (Eukaryotic translation initiation factor 2-alpha kinase 3), maintaining it in an inactive monomeric state (UniProt: P11021). Upon the accumulation of unfolded proteins, GRP78 dissociates from PERK to assist in protein folding, which triggers PERK dimerization and autophosphorylation. Activated PERK then phosphorylates the alpha subunit of eukaryotic initiation factor 2 (eIF2-alpha), causing a global inhibition of protein translation to reduce the ER workload while selectively promoting the translation of stress-adaptive genes such as ATF4 (UniProt: Q9NZJ5; PubMed: 32051602). This pathway is a major therapeutic target in oncology and neurology. Cancer cells often hijack the GRP78-PERK axis to survive the proteotoxic stress of hypoxic and nutrient-poor microenvironments, making PERK inhibition a strategy to selectively trigger apoptosis in tumors (PubMed: 23676665). Conversely, chronic activation of this pathway in neurodegenerative diseases like Alzheimer's and Parkinson's contributes to synaptic loss through prolonged translation attenuation. Despite its promise, systemic inhibition of PERK poses significant safety challenges, notably pancreatic toxicity and hyperglycemia, as PERK is essential for the health of insulin-secreting beta cells (PubMed: 23056100). Consequently, drug development has expanded to include downstream modulators like the integrated stress response inhibitor ISRIB, which may offer a wider therapeutic window.

Other names

GRP78-PERK pathwayEIF2AK3Protein kinase RNA-like endoplasmic reticulum kinasePRKR-like endoplasmic reticulum kinase78 kDa glucose-regulated protein (GRP78)Binding immunoglobulin protein (BiP)HSPA5-EIF2AK3 axis

Small molecule inhibition of the PERK kinase catalytic domain prevents the phosphorylation of eIF2-alpha, thereby blocking the integrated stress response and sensitizing stressed cells to apoptosis.