From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110
J Biol Chem. 2018 Aug 31;293(35):13401-13414. doi: 10.1074/jbc.RA118.004139. Epub 2018 Jul 11.
The epidermal growth factor (EGF) receptor is a classical receptor tyrosine kinase with an extracellular ligand-binding domain and an intracellular kinase domain. Mutations in the EGF receptor have been shown to drive uncontrolled cell growth and are associated with a number of different tumors. Two different types of ATP-competitive EGF receptor tyrosine kinase inhibitors have been identified that bind to either the active (type I) or inactive (type II) conformation of the kinase domain. Despite the fact that both types of inhibitors block tyrosine kinase activity, they exhibit differential efficacies in different tumor types. Here, we show that in addition to inhibiting kinase activity, these inhibitors allosterically modulate ligand binding. Our data suggest that the conformations of the EGF receptor extracellular domain and intracellular kinase domain are coupled and that these conformations exist in equilibrium. Allosteric regulators, such as the small-molecule tyrosine kinase inhibitors, as well as mutations in the EGF receptor itself, shift the conformational equilibrium among the active and inactive species, leading to changes in EGF receptor-binding affinity. Our studies also reveal unexpected positive cooperativity between EGF receptor subunits in dimers formed in the presence of type II inhibitors. These findings indicate that there is strong functional coupling between the intracellular and extracellular domains of this receptor. Such coupling may impact the therapeutic synergy between small-molecule tyrosine kinase inhibitors and monoclonal antibodies .
表皮生长因子（EGF）受体是一种经典的受体酪氨酸激酶，具有细胞外配体结合域和细胞内激酶域。已经表明，EGF 受体的突变会导致不受控制的细胞生长，并与许多不同的肿瘤有关。已经鉴定出两种不同类型的 ATP 竞争性 EGF 受体酪氨酸激酶抑制剂，它们分别与激酶域的活性（I 型）或无活性（II 型）构象结合。尽管这两种类型的抑制剂都能阻断酪氨酸激酶的活性，但它们在不同的肿瘤类型中表现出不同的疗效。在这里，我们表明，除了抑制激酶活性外，这些抑制剂还通过变构调节配体结合。我们的数据表明，EGF 受体细胞外域和细胞内激酶域的构象是耦合的，并且这些构象处于平衡状态。变构调节剂，如小分子酪氨酸激酶抑制剂，以及 EGF 受体自身的突变，会改变活性和非活性物种之间的构象平衡，从而导致 EGF 受体结合亲和力的变化。我们的研究还揭示了在 II 型抑制剂存在下形成的二聚体中 EGF 受体亚基之间出乎意料的正协同作用。这些发现表明，该受体的细胞内和细胞外结构域之间存在很强的功能耦合。这种耦合可能会影响小分子酪氨酸激酶抑制剂和单克隆抗体之间的治疗协同作用。
