Neddylation is essential for ß-catenin degradation in Wnt signaling pathway.

ABSTRACT

ß-Catenin is a central component in the Wnt signaling pathway; its degradation has been tightly connected to ubiquitylation, but it is rarely examined by loss-of-function assays. Here we observe that endogenous ß-catenin is not stabilized upon ubiquitylation depletion by a ubiquitylation inhibitor, TAK-243. We demonstrate that N-terminal phosphorylated ß-catenin is quickly and strongly stabilized by a specific neddylation inhibitor, MLN4924, in all examined cell types, and that ß-catenin and TCF4 interaction is strongly enhanced by inhibition of neddylation but not ubiquitylation. We also confirm that the E3 ligase ß-TrCP2, but not ß-TrCP1, is associated with neddylation and destruction of ß-catenin. GSK3ß and adenomatous polyposis coli (APC) are not required for ß-catenin neddylation but essential for its subsequent degradation. Our findings not only clarify the process of ß-catenin modification and degradation in the Wnt signaling pathway but also highlight the importance of reassessing previously identified ubiquitylation substrates.