The EIF2alpha Kinases PERK and PKR Activate Glycogen Synthase Kinase 3 to Promote the Proteasomal Degradation of P53

Phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) is mediated by a family of kinases that respond to various forms of environmental stress. The eIF2alpha kinases are critical for mRNA translation, cell proliferation, and apoptosis. Activation of the tumor suppressor p53 results in cell cycle arrest and apoptosis in response to various types of stress. We previously showed that, unlike the majority of stress responses that stabilize and activate p53, induction of endoplasmic reticulum stress leads to p53 degradation through an Mdm2-dependent mechanism. Here, we demonstrate that the endoplasmic reticulum-resident eIF2alpha kinase PERK mediates the proteasomal degradation of p53 independently of translational control. This role is not specific for PERK, because the eIF2alpha kinase PKR also promotes p53 degradation in response to double-stranded RNA. We further establish that the eIF2alpha kinases induce glycogen synthase kinase 3 to promote the nuclear export and proteasomal degradation of p53. Our findings reveal a novel cross-talk between the eIF2alpha kinases and p53 with implications in cell proliferation and tumorigenesis.