Stabilization of Mdm2 via decreased ubiquitination is mediated by protein kinase B/Akt-dependent phosphorylation
Stabilization of Mdm2 via decreased ubiquitination is mediated by protein kinase B/Akt-dependent phosphorylation
复制标题
DOI：
10.1074/jbc.m404936200
复制
发表时间：
2004-08-20
影响因子：
4.8
通讯作者：
Hemmings, BA
中科院分区：
文献类型：
--
作者：
Feng, JH;Tamaskovic, R;Hemmings, BA
当磷脂酰亚脂3'-OH激酶/蛋白激酶B (PKB) Akt通路被激活时，肿瘤抑制因子p53通常被抑制。细胞内p53水平由E3泛素连接酶Mdm2控制。在这里，我们发现PKB通过磷酸化Mdm2在Ser（166）和Ser（188）上抑制Mdm2的自泛素化。胰岛素样生长因子-1刺激人胚胎肾293细胞，以磷脂酰亚胺苷3′-OH激酶依赖的方式增加了丝氨酸（166）和丝氨酸（188）上的Mdm2磷酸化，磷脂酰亚胺苷3′-OH激酶抑制剂LY-294002处理人胚胎肾293和COS-1细胞，导致蛋白酶体介导的Mdm2降解。将组成型活性的PKB与Mdm2一起引入细胞，诱导Mdm2在Ser（166）和Ser（188）位点磷酸化，并稳定Mdm2蛋白。此外，缺乏PKBalpha的小鼠胚胎成纤维细胞显示Mdm2蛋白水平降低，同时p53和p21（Cip1）升高，导致紫外线照射后细胞凋亡急剧增加。此外，在多种人类肿瘤细胞中，PKB的激活与Mdm2磷酸化和稳定性相关。这些发现表明PKB在Mdm2的调控中起关键作用。p53信号通路调控Mdm2稳定性。
The tumor suppressor p53 is commonly inhibited under conditions in which the phosphatidylinositide 3'-OH kinase/protein kinase B (PKB) Akt pathway is activated. Intracellular levels of p53 are controlled by the E3 ubiquitin ligase Mdm2. Here we show that PKB inhibits Mdm2 self-ubiquitination via phosphorylation of Mdm2 on Ser(166) and Ser(188). Stimulation of human embryonic kidney 293 cells with insulin-like growth factor-1 increased Mdm2 phosphorylation on Ser(166) and Ser(188) in a phosphatidylinositide 3'-OH kinase-dependent manner, and the treatment of both human embryonic kidney 293 and COS-1 cells with phosphatidylinositide 3'-OH kinase inhibitor LY-294002 led to proteasome-mediated Mdm2 degradation. Introduction of a constitutively active form of PKB together with Mdm2 into cells induced phosphorylation of Mdm2 at Ser(166) and Ser(188) and stabilized Mdm2 protein. Moreover, mouse embryonic fibroblasts lacking PKBalpha displayed reduced Mdm2 protein levels with a concomitant increase of p53 and p21(Cip1), resulting in strongly elevated apoptosis after UV irradiation. In addition, activation of PKB correlated with Mdm2 phosphorylation and stability in a variety of human tumor cells. These findings suggest that PKB plays a critical role in controlling of the Mdm2.p53 signaling pathway by regulating Mdm2 stability.