Mechanism of activation of protein kinase B by insulin and IGF-1
Mechanism of activation of protein kinase B by insulin and IGF-1
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DOI：
10.1002/j.1460-2075.1996.tb01045.x
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发表时间：
1996-12-02
期刊：
影响因子：
11.4
通讯作者：
Hemmings, BA
中科院分区：
文献类型：
--
作者：
Alessi, DR;Andjelkovic, M;Hemmings, BA
在L6肌管中，胰岛素激活内源性蛋白激酶BA(也称为RAC/Akt激酶)活性12倍，而在转染293细胞后，PKBα被胰岛素和IGF-1分别激活20倍和50倍。在这两个细胞中，PKBα的激活伴随着它在Thr308和Ser473处的磷酸化，与激活一样，这两个残基的磷酸化被磷脂酰肌醇3-激酶抑制剂Wortmannin阻止，Thr308和/或Ser473突变为Ala或Asp，并分析突变的PKBα分子的活性。MAPKAP激酶-2化学计量比磷酸化Ser473后，体外检测野生型和突变型PKBα的活性。这些实验表明，胰岛素或胰岛素样生长因子-1(IGF-1)激活PKBα是Thr308和Ser473磷酸化的结果，这两个残基的磷酸化是产生高水平PKBα活性的关键，体内Thr308的磷酸化不依赖于Ser373的磷酸化，反之亦然。我们提出了一个模型，在这个模型中，在胰岛素/胰岛素样生长因子-1刺激的细胞中，蛋白激酶Bα被磷酸化并被上游激酶激活(S)。
Insulin activated endogenous protein kinase Ba (also known as RAC/Akt kinase) activity 12-fold in L6 myotubes, while after transfection into 293 cells PKB alpha was activated 20- and 50-fold in response to insulin and IGF-1 respectively. In both cells, the activation of PKB alpha was accompanied by its phosphorylation at Thr308 and Ser473 and, like activation, phosphorylation of both of these residues was prevented by the phosphatidylinositol 3-kinase inhibitor wortmannin, Thr308 and/or Ser473 were mutated to Ala or Asp and activities of mutant PKB alpha molecules were analysed after transfection into 293 cells, The activity of wildtype and mutant PKB alpha was also measured in vitro after stoichiometric phosphorylation of Ser473 by MAPKAP kinase-2. These experiments demonstrated that activation of PKB alpha by insulin or insulin-like growth factor-1 (IGF-1) results from phosphorylation of both Thr308 and Ser473, that phosphorylation of both residues is critical to generate a high level of PKB alpha activity and that the phosphorylation of Thr308 in vivo is not dependent on phosphorylation of Ser373 or vice versa. We propose a model whereby PKB alpha becomes phosphorylated and activated in insulin/IGF-1-stimulated cells by an upstream kinase(s).