Fumoto K, Lee P-C, Saya H, Kikuchi A
Department of Biochemistry, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
Oncogene. 2008 Jul 24;27(32):4478-87. doi: 10.1038/onc.2008.92. Epub 2008 Apr 7.
Glycogen synthase kinase-3 (GSK-3beta) regulates microtubule dynamics and cellular polarity through phosphorylating various microtubule associating proteins and plus-end tracking proteins. Although it was also reported that GSK-3beta is inactivated by protein kinase B at the spindle poles, functions and targets of GSK-3beta in the mitotic phase are unknown. Here, we identified Aurora-A-interacting protein (AIP), a negative regulator of Aurora-A, as a binding partner of GSK-3beta. AIP was colocalized with Aurora-A and GSK-3beta to the spindle poles in metaphase, and its depletion in cells stabilized and activated Aurora-A in early mitotic phase and caused mitotic cell arrest. Treatment of the cells with a GSK-3beta inhibitor reduced the protein level of Aurora-A and this reduction was suppressed by AIP knockdown. AIP was phosphorylated by GSK-3beta, and an AIP mutant in which the GSK-3beta phosphorylation site was mutated could bind and downregulate Aurora-A more efficiently. These results suggest that GSK-3beta modulates the early mitotic Aurora-A level through binding and phosphorylating AIP.
糖原合酶激酶-3（GSK-3β）通过磷酸化各种微管相关蛋白和正端追踪蛋白来调节微管动力学和细胞极性。尽管也有报道称GSK-3β在纺锤体极被蛋白激酶B失活，但其在有丝分裂期的功能和靶点尚不清楚。在此，我们鉴定出极光激酶A相互作用蛋白（AIP），一种极光激酶A的负调节因子，作为GSK-3β的结合伴侣。在中期，AIP与极光激酶A和GSK-3β共定位于纺锤体极，其在细胞中的缺失在有丝分裂早期稳定并激活了极光激酶A，并导致有丝分裂细胞停滞。用GSK-3β抑制剂处理细胞降低了极光激酶A的蛋白水平，而这种降低被AIP敲低所抑制。AIP被GSK-3β磷酸化，并且其中GSK-3β磷酸化位点发生突变的AIP突变体能够更有效地结合并下调极光激酶A。这些结果表明，GSK-3β通过结合和磷酸化AIP来调节有丝分裂早期极光激酶A的水平。
