Phosphorylation of p27Kip1 regulates assembly and activation of cyclin D1-Cdk4
Phosphorylation of p27Kip1 regulates assembly and activation of cyclin D1-Cdk4
复制标题
DOI：
10.1128/mcb.02300-07
复制
发表时间：
2008-10-01
影响因子：
5.3
通讯作者：
Slingerland, Joyce M.
中科院分区：
文献类型：
--
作者：
Larrea, Michelle D.;Liang, Jiyong;Slingerland, Joyce M.
p27介导Cdk 2抑制，并且也在细胞周期蛋白D1-Cdk 4复合物中发现。目前的数据支持的作用，p27在组装的D-型细胞周期蛋白-Cdk复合物，并表明，细胞周期蛋白D1-Cdk 4-p27组装和激酶激活调节p27磷酸化。先前的工作表明，p27可以被蛋白激酶B/Akt（PKB/Akt）在T157和T198处磷酸化。在这里，我们发现PKB激活和p27 pT 157和p27 pT 198的出现先于p27-cyclin D1-Cdk 4在早期G（1）的装配。PI 3 K/PKB抑制迅速减少p27 pT 157和p27 pT 198，并解离细胞p27-细胞周期蛋白D1-Cdk 4。在T157和T198处缺乏磷酸化的突变型p27等位基因产物与细胞周期蛋白D1和Cdk 4的结合较差。细胞p27 pT 157和p27 pT 198与Cdk 4共沉淀，但在Cdk 2复合物中未检测到。在体外将p27加入到重组细胞周期蛋白D1和Cdk 4中，导致细胞周期蛋白D1-Cdk 4-p27复合物的形成。p27磷酸化PKB增加p27-细胞周期蛋白D1-Cdk 4组装在体外，但产生失活的Cdk 4。相反，Src预处理p27不影响p27-cyclin D1-Cdk 4复合物的形成。然而，Src处理导致p27的酪氨酸磷酸化和组装的细胞周期蛋白D1-Cdk 4-p27复合物的催化活化。因此，虽然PKB依赖的p27磷酸化似乎增加细胞周期蛋白D1-Cdk 4-p27组装或稳定这些复合物在体外，细胞周期蛋白D1-Cdk 4-p27激活需要p27的酪氨酸磷酸化。PKB和Abl或Src家族激酶在癌症中的组成性激活将驱动p27磷酸化，增加细胞周期蛋白D1-Cdk 4组装和激活，并降低p27的细胞周期蛋白E-Cdk 2抑制功能。Src和PI 3 K/PKB抑制剂的联合治疗可能会逆转这一过程。
p27 mediates Cdk2 inhibition and is also found in cyclin D1-Cdk4 complexes. The present data support a role for p27 in the assembly of D-type cyclin-Cdk complexes and indicate that both cyclin D1-Cdk4-p27 assembly and kinase activation are regulated by p27 phosphorylation. Prior work showed that p27 can be phosphorylated by protein kinase B/Akt (PKB/Akt) at T157 and T198. Here we show that PKB activation and the appearance of p27pT157 and p27pT198 precede p27-cyclin D1-Cdk4 assembly in early G(1). PI3K/PKB inhibition rapidly reduced p27pT157 and p27pT198 and dissociated cellular p27-cyclin D1-Cdk4. Mutant p27 allele products lacking phosphorylation at T157 and T198 bound poorly to cellular cyclin D1 and Cdk4. Cellular p27pT157 and p27pT198 coprecipitated with Cdk4 but were not detected in Cdk2 complexes. The addition of p27 to recombinant cyclin D1 and Cdk4 led to cyclin D1-Cdk4-p27 complex formation in vitro. p27 phosphorylation by PKB increased p27-cyclin D1-Cdk4 assembly in vitro but yielded inactive Cdk4. In contrast, Src pretreatment of p27 did not affect p27-cyclin D1-Cdk4 complex formation. However, Src treatment led to tyrosine phosphorylation of p27 and catalytic activation of assembled cyclin D1-Cdk4-p27 complexes. Thus, while PKB-dependent p27 phosphorylation appears to increase cyclin D1-Cdk4-p27 assembly or stabilize these complexes in vitro, cyclin D1-Cdk4-p27 activation requires the tyrosine phosphorylation of p27. Constitutive activation of PKB and Abl or Src family kinases in cancers would drive p27 phosphorylation, increase cyclin D1-Cdk4 assembly and activation, and reduce the cyclin E-Cdk2 inhibitory function of p27. Combined therapy with both Src and PI3K/PKB inhibitors may reverse this process.