P68 RNA Helicase Mediates PDGF-Induced Epithelial Mesenchymal Transition by Displacing Axin from β-Catenin

SummaryThe nuclear p68 RNA helicase (referred to as p68) is a prototypical member of the DEAD box family of RNA helicases. The protein plays a very important role in early organ development. In the present study, we characterized the tyrosine phosphorylation of p68 under platelet-derived growth factor (PDGF) stimulation. We demonstrated that tyrosine phosphorylation of p68 at Y593 mediated PDGF-stimulated epithelial-mesenchymal transition (EMT). We showed that PDGF treatment led to phosphorylation of p68 at Y593 in the cell nucleus. The Y593-phosphorylated p68 (referred to as phosphor-p68) promotes β-catenin nuclear translocation via a Wnt-independent pathway. The phosphor-p68 facilitates β-catenin nuclear translocation by blocking phosphorylation of β-catenin by GSK-3β and displacing Axin from β-catenin. The β-catenin nuclear translocation and subsequent interaction with the LEF/TCF was required for the EMT process. These data demonstrated a novel mechanism of phosphor-p68 in mediating the growth factor-induced EMT and uncovered a new pathway to promote β-catenin nuclear translocation.