Genentech Inc., South San Francisco, CA 94080, USA.
Sci Signal. 2012 May 8;5(223):ra37. doi: 10.1126/scisignal.2002618.
The protein serine-threonine kinase Akt undergoes a substantial conformational change upon activation, which is induced by the phosphorylation of two critical regulatory residues, threonine 308 and serine 473. Paradoxically, treating cells with adenosine 5'-triphosphate (ATP)-competitive inhibitors of Akt results in increased phosphorylation of both residues. We show that binding of ATP-competitive inhibitors stabilized a conformation in which both phosphorylated sites were inaccessible to phosphatases. ATP binding also produced this protection of the phosphorylated sites, whereas interaction with its hydrolysis product adenosine 5'-diphosphate (ADP) or allosteric Akt inhibitors resulted in increased accessibility of these phosphorylated residues. ATP-competitive inhibitors mimicked ATP by targeting active Akt. Forms of Akt activated by an oncogenic mutation or myristoylation were more potently inhibited by the ATP-competitive inhibitors than was wild-type Akt. These data support a new model of kinase regulation, wherein nucleotides modulate an on-off switch in Akt through conformational changes, which is disrupted by ATP-competitive inhibitors.
蛋白丝氨酸苏氨酸激酶 Akt 在激活时会发生显著的构象变化，这种变化是由两个关键调节残基丝氨酸 308 和苏氨酸 473 的磷酸化诱导的。矛盾的是，用 Akt 的 ATP 竞争性抑制剂处理细胞会导致这两个残基的磷酸化程度增加。我们表明，ATP 竞争性抑制剂的结合稳定了一种构象，其中两个磷酸化位点都无法被磷酸酶作用。ATP 结合也产生了对磷酸化位点的这种保护，而与它的水解产物腺苷 5'-二磷酸（ADP）或别构 Akt 抑制剂的相互作用导致这些磷酸化残基更容易被接近。ATP 竞争性抑制剂通过靶向活性 Akt 模拟 ATP。致癌突变或豆蔻酰化激活的 Akt 形式比野生型 Akt 更容易被 ATP 竞争性抑制剂抑制。这些数据支持激酶调节的新模型，其中核苷酸通过构象变化调节 Akt 的开-关开关，而 ATP 竞争性抑制剂会破坏这种开关。
