Resistance of Akt kinases to dephosphorylation through ATP-dependent conformational plasticity
Resistance of Akt kinases to dephosphorylation through ATP-dependent conformational plasticity
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DOI：
10.1073/pnas.1109879108
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发表时间：
2011-11-15
影响因子：
11.1
通讯作者：
Feldman, Arthur M.
中科院分区：
文献类型：
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作者：
Chan, Tung O.;Zhang, Jin;Feldman, Arthur M.
Akt激酶激活环中的苏氨酸残基（Akt 1中的T308）磷酸化是肿瘤中经常观察到的Akt活性失调的先决条件。体内Akt磷酸化通过激酶和磷酸酶的相反活性来平衡。在这里，我们描述了靶向Akt激酶的细胞膜显着降低的敏感性磷酸化Akt蛋白磷酸酶2A去磷酸化。这种效应被ATP或ATP竞争性抑制剂占据ATP结合口袋放大。突变分析显示，Akt 1中的R273和Akt 2中相应的R274对于保护激活环中的T308免于去磷酸化是必需的。因此，Akt激酶的核苷酸结合口袋的占据使得限制磷酸酶进入并维持Akt磷酸化的分子内相互作用成为可能。这一机制为ATP竞争性抑制剂A-443654诱导的Akt过度磷酸化提供了一种解释。磷酸酶抗性的缺乏进一步有助于深入了解人类Akt 2 R274 H错义突变可能导致常染色体显性糖尿病的机制。
Phosphorylation of a threonine residue (T308 in Akt1) in the activation loop of Akt kinases is a prerequisite for deregulated Akt activity frequently observed in neoplasia. Akt phosphorylation in vivo is balanced by the opposite activities of kinases and phosphatases. Here we describe that targeting Akt kinase to the cell membrane markedly reduced sensitivity of phosphorylated Akt to dephosphorylation by protein phosphatase 2A. This effect was amplified by occupancy of the ATP binding pocket by either ATP or ATP-competitive inhibitors. Mutational analysis revealed that R273 in Akt1 and the corresponding R274 in Akt2 are essential for shielding T308 in the activation loop against dephosphorylation. Thus, occupancy of the nucleotide binding pocket of Akt kinases enables intramolecular interactions that restrict phosphatase access and sustain Akt phosphorylation. This mechanism provides an explanation for the "paradoxical" Akt hyperphosphorylation induced by ATP-competitive inhibitor, A-443654. The lack of phosphatase resistance further contributes insight into the mechanism by which the human Akt2 R274H missense mutation may cause autosomal-dominant diabetes mellitus.