EIF2AK3

EIF2AK3 Background

Eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3), also known as PERK (protein kinase R (PKR)-like endoplasmic reticulum kinase) ^[1], is one of the eIF2α kinases (EIF2AKs), a family of four distinct serine-threonine kinases ^[2]. PERK is an endoplasmic reticulum (ER) transmembrane protein. Its N-terminal region is important for dimerization, regulation, and association with ER chaperone, including immunoglobulin binding protein (BiP) and HspA5 ^{[3]. While its C-terminal region is cytosolic and contains Kinase Domains (KDs) with autophosphorylation sites [3]. Under normal physiological conditions, Bip binds to IRE-1, activating transcription factor-6α (ATF6α), and PERK, rendering them inactive. Following the accumulation of misfolded/unfolded proteins within the ER, Bip dissociates from the three ER sensor proteins, thereby leading to their activation and subsequent induction of the unfolded protein response (UPR) [4][13]. Upon induction of the UPR, PERK autoactivates by homodimerization and autophosphorylation [5][6]. Activated PERK phosphorylates the alpha subunit of the eukaryotic initiation factor 2 (eIF2α) which blocks "cap-dependent" protein synthesis but results in the preferential translation of ATF4, a transcription factor that upregulates the proapoptotic transcription factor CHOP (CAAT/enhancer-binding protein homologous protein) and genes required to restore normal ER function [7]. So transient PERK activation is protective. However, chronic ER stress and sustained PERK activation can be detrimental to cell health. Unresolved UPR and protracted ER stresses cause sustained activation of eIF2α phosphorylation and CHOP induction, resulting in ER stress-triggered apoptosis involving the induction of BH3 domain-only proteins BIK and BIM [8][9] as well as the death receptor DR5 [10] and the activation of the intrinsic pathway of apoptosis including the caspase-9/caspase-3/caspase-7 caspase cascade [11]. Many diseases are related to PERK over-activation, suggesting that small molecule PERK inhibitors may provide new opportunities for treating cancer and neurodegenerative diseases [12].}

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