Mbom Bertrade C, Siemers Kathleen A, Ostrowski Maggie A, Nelson W James, Barth Angela I M
Department of Biology, Stanford University, Stanford, CA 94305 Department of Chemical Engineering, Stanford University, Stanford, CA 94305 Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305.
Mol Biol Cell. 2014 Apr;25(7):977-91. doi: 10.1091/mbc.E13-06-0349. Epub 2014 Feb 5.
β-Catenin is a multifunctional protein with critical roles in cell-cell adhesion, Wnt signaling, and the centrosome cycle. Whereas the regulation of β-catenin in cell-cell adhesion and Wnt signaling are well understood, how β-catenin is regulated at the centrosome is not. NIMA-related protein kinase 2 (Nek2), which regulates centrosome disjunction/splitting, binds to and phosphorylates β-catenin. Using in vitro and cell-based assays, we show that Nek2 phosphorylates the same regulatory sites in the N-terminus of β-catenin as glycogen synthase kinase 3β (GSK3β), which are recognized by a specific phospho-S33/S37/T41 antibody, as well as additional sites. Nek2 binding to β-catenin appears to inhibit binding of the E3 ligase β-TrCP and prevents β-catenin ubiquitination and degradation. Thus β-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 β-catenin. Taken together, these results identify a novel mechanism for regulating β-catenin stability that is independent of GSK3β and provide new insight into a pathway involving Plk1, Nek2, and β-catenin that regulates the centrosome cycle.
β-连环蛋白是一种多功能蛋白质，在细胞间黏附、Wnt信号传导和中心体周期中发挥关键作用。虽然β-连环蛋白在细胞间黏附及Wnt信号传导中的调控机制已得到充分了解，但它在中心体中的调控方式尚不清楚。与NIMA相关的蛋白激酶2（Nek2）可调节中心体分离/分裂，它能与β-连环蛋白结合并使其磷酸化。通过体外实验和基于细胞的分析，我们发现Nek2磷酸化β-连环蛋白N端的位点与糖原合酶激酶3β（GSK3β）相同，这些位点可被一种特异性磷酸化S33/S37/T41抗体识别，此外还有其他位点。Nek2与β-连环蛋白的结合似乎会抑制E3连接酶β-TrCP的结合，并阻止β-连环蛋白的泛素化和降解。因此，被Nek2磷酸化的β-连环蛋白得以稳定，并在有丝分裂时在中心体积累。我们进一步表明，polo样激酶1（Plk1）可调节Nek2对β-连环蛋白的磷酸化及稳定性。综上所述，这些结果确定了一种独立于GSK3β的调节β-连环蛋白稳定性的新机制，并为涉及Plk1、Nek2和β-连环蛋白的调节中心体周期的信号通路提供了新见解。
