Understanding EGF receptor activation by growth factors and oncogenic mutations

表皮生长因子受体(Egfr)是一种典型的受体酪氨酸激酶。 (RTK)。作为第一批配体诱导二聚的单一跨膜结构域受体之一 据报道，对于EGFR(和其他RTK)的“传统”观点是一个二进制的“关”/“开”开关。我们以前的 相反，与最近对类似受体的研究一起，他们认为这种类型的受体发出的信号 更“分级”--而且EGFR和其他受体可以区分不同的配体。的确， 我们发现不同的EGFR激活配体可以诱导具有不同结构的受体二聚体。 不同的信号动力学和细胞结果的正交性。值得注意的是，定义该物种的关键残基 这些二聚体的结构差异与细胞外EGFR突变的热点一致 在胶质母细胞瘤中。因此，我们在这里假设，GBM中的EGFR突变可能至少部分发挥了 通过改变对不同EGFR配体的信号反应的性质来发挥作用。这将打开 如果抗体或其他药物能够发展成能够纠正癌症中的EGFR信号的可能性 通过与G蛋白偶联的偏向激动剂类比，将它们重新编程为“变构微处理器” 感受器。 胶质母细胞瘤和肺癌对EGFR抑制剂的原发耐药性是一个重要的临床问题 这限制了现有的EGFR靶向酪氨酸激酶抑制剂(TKI)的成功。静态结构视图 对于TKI抑制不同基因的相对能力，激酶结构域并不能提供令人满意的解释 变种--原发抗性和突变体选择性(例如奥西美替尼)的起源不清楚 很难解决。新的获得性TKI抵抗案例也遭遇了同样的问题。我们的研究使用 氢-氚交换质谱仪(HDX-MS)和酶学的结合表明，关键可能是 在于突变和TKI本身对结构动力学的影响--特别是在 第三代共价EGFR抑制剂在多个步骤中与其靶标相关联的情况。 在此背景下，该提案的关键总体目标是确定EGFR变体的特定行为 在癌症中发现，这可以解释它们信号特性的改变和对抑制剂敏感性的改变。我们申请 一系列生物物理、结构、生化和细胞方法，用于在几个 分辨率级别。除了回答EGFR的关键机制问题外，我们的结果还应该说明 潜在的治疗干预新途径。我们的具体目标是提出以下问题： 1 EGFR家族成员中与疾病相关的胞外突变如何影响信号特异性 那动力学呢？ 结构动力学能解释肺组织中19号外显子EGFR变异体对初级激酶抑制物的耐药性吗？ 癌症和第三代共价抑制剂的选择性？

The epidermal growth factor receptor (EGFR) is often described as a ‘prototypic’ receptor tyrosine kinase (RTK). As one of the first single transmembrane domain receptors for which ligand-induced dimerization was reported, the ‘traditional’ view of EGFR (and other RTKs) has been of a binary ‘off’/‘on’ switch. Our previous work, together with recent work on similar receptors, instead argues that signaling by receptors of this type is much more ‘graded’ – and that EGFR and other receptors can discriminate between different ligands. Indeed, we showed that different EGFR-activating ligands can induce receptor dimers with distinct structures – leading to different signaling kinetics and orthogonal cellular outcomes. Remarkably, the key residues that define the differences between the structures of these dimers coincide with the hotspots for extracellular EGFR mutations in glioblastoma. We therefore hypothesize here that EGFR mutations in GBM may exert at least part of their effect by altering the nature of the signaling response to different EGFR ligands. This would open the possibility of ‘correcting’ EGFR signaling in cancer if antibodies or other agents could be developed to reprogram them as ‘allosteric microprocessors’ by analogy with biased agonists for G-protein coupled receptors. Primary resistance to EGFR inhibitors in glioblastoma and in lung cancer is an important clinical problem that limits success with existing EGFR-targeted tyrosine kinase inhibitors (TKIs). Static structural views of kinase domains have not allowed satisfying explanations for the relative abilities of TKIs to inhibit different variants – leaving the origins of primary resistance and of mutant selectivity (e.g. of osimertinib) unclear and difficult to solve. New instances of acquired TKI resistance suffer from the same problem. Our studies using hydrogen-deuterium exchange mass spectrometry (HDX-MS) alongside enzymology suggest that the key may lie in the effects of both the mutations and the TKIs themselves on structural dynamics – particularly in the case of 3rd generation covalent EGFR inhibitors that associate with their targets in multiple steps. With this background, the key overall goal of this proposal is to identify specific behavior of EGFR variants seen in cancer that can explain their altered signaling properties and altered sensitivity to inhibitors. We apply a range of biophysical, structural, biochemical, and cellular approaches to interrogate signaling at several levels of resolution. In addition to answering key mechanistic questions for EGFR, our results should illuminate potential new avenues for therapeutic intervention. Our Specific Aims ask the following questions: 1 How do disease-associated extracellular mutations in EGFR family members affect signaling specificity and kinetics? 2 Can structural dynamics explain primary kinase inhibitor resistance of exon 19 EGFR variants in lung cancer, and selectivity of 3rd generation covalent inhibitors?