Fumoto Katsumi, Kadono Moe, Izumi Nanae, Kikuchi Akira
Department of Biochemistry, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
EMBO Rep. 2009 Jun;10(6):606-13. doi: 10.1038/embor.2009.45. Epub 2009 Apr 24.
Axin is known to have an important role in the degradation of beta-catenin in the Wnt pathway. Here, we reveal a new function of Axin at the centrosome. Axin was localized to the centrosome in various cell lines and formed a complex with gamma-tubulin. Knockdown of Axin reduced the localization of gamma-tubulin and gamma-tubulin complex protein 2-components of the gamma-tubulin ring complex-to the centrosome and the centrosomal microtubule nucleation activity after treatment with nocodazole. These phenotypes could not be rescued by the reduction in the levels of beta-catenin. Although the expression of Axin rescued these phenotypes in Axin-knockdown cells, overexpression of Axin2, which is highly homologous to Axin, could not. Axin2 was also localized to the centrosome, but it did not form a complex with gamma-tubulin. These results suggest that Axin, but not Axin2, is involved in microtubule nucleation by forming a complex with gamma-tubulin at the centrosome.
已知Axin在Wnt信号通路中β-连环蛋白的降解过程中发挥重要作用。在此,我们揭示了Axin在中心体的一项新功能。Axin在多种细胞系中定位于中心体,并与γ-微管蛋白形成复合物。在用诺考达唑处理后,敲低Axin会降低γ-微管蛋白和γ-微管蛋白复合物蛋白2(γ-微管蛋白环复合物的组成成分)在中心体的定位以及中心体微管成核活性。这些表型不能通过降低β-连环蛋白的水平来挽救。尽管Axin的表达可挽救Axin敲低细胞中的这些表型,但与Axin高度同源的Axin2的过表达却不能。Axin2也定位于中心体,但它不与γ-微管蛋白形成复合物。这些结果表明,Axin而非Axin2通过在中心体与γ-微管蛋白形成复合物参与微管成核。