Nek2 phosphorylates and stabilizes ß-catenin at mitotic centrosomes downstream of Plk1.

ABSTRACT

ß-Catenin is a multifunctional protein with critical roles in cell-cell adhesion, Wnt signaling, and the centrosome cycle. Whereas the regulation of ß-catenin in cell-cell adhesion and Wnt signaling are well understood, how ß-catenin is regulated at the centrosome is not. NIMA-related protein kinase 2 (Nek2), which regulates centrosome disjunction/splitting, binds to and phosphorylates ß-catenin. Using in vitro and cell-based assays, we show that Nek2 phosphorylates the same regulatory sites in the N-terminus of ß-catenin as glycogen synthase kinase 3ß (GSK3ß), which are recognized by a specific phospho-S33/S37/T41 antibody, as well as additional sites. Nek2 binding to ß-catenin appears to inhibit binding of the E3 ligase ß-TrCP and prevents ß-catenin ubiquitination and degradation. Thus ß-catenin phosphorylated by Nek2 is stabilized and accumulates at centrosomes in mitosis. We further show that polo-like kinase 1 (Plk1) regulates Nek2 phosphorylation and stabilization of ß-catenin. Taken together, these results identify a novel mechanism for regulating ß-catenin stability that is independent of GSK3ß and provide new insight into a pathway involving Plk1, Nek2, and ß-catenin that regulates the centrosome cycle.