Axin localizes to the centrosome and is involved in microtubule nucleation

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.