Phosphorylation by glycogen synthase kinase-3 controls c-Myc proteolysis and subnuclear localization
Phosphorylation by glycogen synthase kinase-3 controls c-Myc proteolysis and subnuclear localization
复制标题
DOI：
10.1074/jbc.m310722200
复制
发表时间：
2003-12-19
影响因子：
4.8
通讯作者：
Hann, SR
中科院分区：
文献类型：
--
作者：
Gregory, MA;Qi, Y;Hann, SR
C-Myc蛋白是一种转录因子，是细胞生长和增殖的中央调节因子。Thr-58是c-Myc的主要磷酸化位点，也是Burkitt‘s和其他侵袭性人类淋巴瘤的突变热点，表明Thr-58的磷酸化限制了c-Myc的致癌潜力。苏氨酸受体-58的突变也与c-Myc蛋白稳定性增加有关。在这里，我们表明，锂抑制糖原合成酶激酶-3(GSK-3)的活性增加了c-Myc的稳定性，并在体内抑制了c-Myc的磷酸化，特别是在Thr-58。反之，过表达GSK-3α或GSK-3β可增强Thr-58的磷酸化和c-Myc的泛素化。综上所述，这些观察表明，GSK-3介导的Thr-58的磷酸化通过泛素途径促进c-Myc的快速蛋白分解。此外，我们证明了GSK-3在体内和体外都与c-Myc结合，并且GSK-3与c-Myc在细胞核内共存，有力地证明了GSK-3是c-Myc Thr-58激酶。我们发现，缺少c-Myc的N端100个氨基酸的c-MycS不能与GSK-3结合；然而，Thr-58磷酸化所必需的启动磷酸化位点Ser-62的突变不会破坏GSK-3的结合。最后，我们发现Thr-58的磷酸化改变了c-Myc的亚核定位，与GSK-3一起增强了它对离散核体的定位。
The c-Myc protein is a transcription factor that is a central regulator of cell growth and proliferation. Thr-58 is a major phosphorylation site in c-Myc and is a mutational hotspot in Burkitt's and other aggressive human lymphomas, indicating that Thr-58 phosphorylation restricts the oncogenic potential of c-Myc. Mutation of Thr-58 is also associated with increased c-Myc protein stability. Here we show that inhibition of glycogen synthase kinase-3 (GSK-3) activity with lithium increases c-Myc stability and inhibits phosphorylation of c-Myc specifically at Thr-58 in vivo. Conversely, overexpression of GSK-3alpha or GSK-3beta enhances Thr-58 phosphorylation and ubiquitination of c-Myc. Together, these observations suggest that phosphorylation of Thr-58 mediated by GSK-3 facilitates c-Myc rapid proteolysis by the ubiquitin pathway. Furthermore, we demonstrate that GSK-3 binds c-Myc in vivo and in vitro and that GSK-3 colocalizes with c-Myc in the nucleus, strongly arguing that GSK-3 is the c-Myc Thr-58 kinase. We found that c-MycS, which lacks the N-terminal 100 amino acids of c-Myc, is unable to bind GSK-3; however, mutation of Ser-62, the priming phosphorylation site necessary for Thr-58 phosphorylation, does not disrupt GSK-3 binding. Finally, we show that Thr-58 phosphorylation alters the subnuclear localization of c-Myc, enhancing its localization to discrete nuclear bodies together with GSK-3.