PERK phosphorylation on tyrosine 561 delays ER stress‐induced PERK activation

The PKR‐like endoplasmic reticulum (ER) kinase (PERK) is an ER transmembrane ser/thr protein kinase that plays an essential role in mediating the unfolded protein response (UPR) activated during stress conditions in the ER lumen. The importance of PERK in pancreatic beta‐cell homeostasis is demonstrated in Wolcott‐ Rallison syndrome, a neonatal or early infancy form of insulin‐dependent diabetes in humans with inactivating mutations in the PERK gene. In this study, we provide strong evidence that PERK is phosphorylated on tyrosine 561 (Y561) in pervanadate‐treated MIN6 cells, a mouse pancreatic beta cell line in culture. In addition, we demonstrate that increased phosphorylation of PERK on Y561 delays PERK activation in response to pharmacological agents that induce ER stress. Interestingly, we discovered that the adaptor protein Nck1 directly interacts with PERK phosphorylated on Y561 through its SH2 domain. Finally, using recombinant wild‐type and kinase dead PERK proteins, our data strongly suggest that PERK phosphorylation on Y561 is dependent on PERK kinase activity. All together, our results indicate that PERK phosphorylation on Y561 and binding to Nck1 play an important role in regulating PERK activity. Supported by the Canadian Diabetes Association.