Activation of E3 ubiquitin ligase WWP2 by non‐receptor tyrosine kinase ACK1

Abstract WW domain containing E3 ubiquitin protein ligase 2 (WWP2) is a member of the NEDD4 E3 ubiquitin ligase family. WWP2 ligase activity is regulated by the 2, 3‐linker auto‐inhibition. Tyrosine phosphorylation of the 2, 3‐linker was identified as an activating means for releasing the auto‐inhibition of WWP2. However, the tyrosine kinase (TK) for the phosphorylation and activation remains unknown. In this report, we have found that non‐receptor TK ACK1 binds to the WW3 domain of WWP2 and phosphorylates WWP2. ACK1 phosphorylates WWP2 at the 2, 3‐linker and partially activates the ubiquitination ligase activity. Unexpectedly, tyrosine phosphorylation of the 2, 3‐linker seems not a major mode for activation of WWP2, as ACK1 causes much higher activation of the 2, 3‐linker tyrosine phosphorylation defective mutants of WWP2 than that of wild‐type WWP2. Furthermore, epidermal growth factor (EGF) stimulates tyrosine phosphorylation of WWP2 and this EGF‐stimulated phosphorylation of WWP2 is mediated by ACK1. Finally, knockdown of WWP2 by shWWP2 inhibits the EGF‐dependent cell proliferation of lung cancer A549 cells, suggesting that WWP2 may function in the EGFR signaling in lung cancer progression. Taken together, our findings have revealed a novel mechanism underlying activation of WWP2.