Intrinsic Disorder and Agonist Bias in EGF Receptor Signaling

摘要 表皮生长因子受体（EGFR）是一种细胞表面受体酪氨酸激酶，经常突变或过度表达。 在多种肿瘤中表达。EGF对受体的刺激导致其细胞内 酪氨酸激酶，使其本质上无序的C末端尾部的多个酪氨酸自磷酸化。 这些磷酸酪氨酸作为含有SH 2和PTB结构域的蛋白质的结合位点， EGF的作用SH 2和PTB结构域通过短线性基序识别它们的结合位点 其中pTyr被嵌入。在初步的实验中，我们发现这些区域之外的区域 短基序有助于SH 2和PTB结构域蛋白的结合。进一步证明了 SH 2结构域与EGFR尾结合的更远距离序列来自我们的初步研究。 计算机模拟研究表明，当Grb 2 SH 2结构域与Tyr-1068结合时， EGFR自身磷酸化的主要位点Tyr-1148周围的蛋白质与EGFR的次级结合相互作用， 在SH 2域上的表面。这种相互作用限制了Tyr-1148与其伴侣蛋白结合的可用性。 因此，我们假设远离pTyr基序的尾部区域参与SH 2的结合 结构域蛋白，这些扩展的相互作用修改了尾巴的构象系综， 它与其他伙伴以整体变构的形式互动的能力。 EGFR可以被七种不同配体中的任何一种激活，这可以引起不同的长期免疫反应。 生物学效应作用于同一细胞。用两种不同的配体刺激同一细胞， 会导致两种完全不同的生物学结果。我们已经证明了不同的能力， 不同的配体以诱导受体同源和异源二聚化并结合下游信号蛋白。 在初步研究中，我们还记录了它们刺激糖酵解通量的能力差异，这是一个关键因素。 快速生长细胞的代谢特征。已知不同的肿瘤优先通过 结构上不同形式的EGFR并表达不同的EGFR配体。在许多情况下，临床 结果显示与表达的配体相关。我们假设， 不同的致癌EGFR在功能上是不同的，EGFR变体和配体的某些组合 比其他人更能转化。我实验室的目标是阐明 通过受体酪氨酸激酶的潜在信号传导，并将其应用于了解突变EGFR如何诱导 肿瘤的这项建议的具体目标是：1.确定酪氨酸间序列如何调节 SH 2结构域蛋白与EGFR的C-末端尾的结合;和，2）鉴定功能差异 在致癌EGFR及其对EGFR激动剂的反应中， 建立和维护。

Abstract The EGF receptor (EGFR) is a cell surface receptor tyrosine kinase that is frequently mutated or over- expressed in a variety of tumors. Stimulation of the receptor by EGF leads to the activation of its intracellular tyrosine kinase which autophosphorylates multiple tyrosines on its intrinsically-disordered C-terminal tail. These phosphotyrosines serve as binding sites for the SH2 and PTB domain-containing proteins that mediate the downstream effects of EGF. SH2 and PTB domains recognize their binding sites via a short linear motif in which the pTyr is embedded. In preliminary experiments, we have found that regions well outside of these short motifs contribute to the binding of SH2 and PTB domain proteins. Further evidence for the importance of more distant sequences in the binding of SH2 domains to the EGFR tail was derived from our preliminary computer modeling studies that show that when the Grb2 SH2 domain is bound to Tyr-1068, the sequence surrounding Tyr-1148, the major site of autophosphorylation of the EGFR, interacts with a secondary binding surface on the SH2 domain. This interaction limits the availability of Tyr-1148 to bind to its partner proteins. We therefore hypothesize that regions of the tail distant from the pTyr motif participate in the binding of SH2 domain proteins and that these extended interactions modify the conformational ensemble of the tail and alter its ability to interact with other partners in a form of ensemble allostery. The EGFR can be activated by any one of seven different ligands, which can elicit different long-term biological effects when applied to the same cell. Stimulation of the same cell with two different ligands can give rise to two completely different biological outcomes. We have demonstrated differences in the ability of different ligands to induce receptor homo- and hetero-dimerization and to bind downstream signaling proteins. In preliminary studies, we have also documented differences in their ability to stimulate glycolytic flux, a key metabolic feature of rapidly growing cells. Different tumors are known to be preferentially transformed by structurally different forms of the EGFR and to express different EGFR ligands. In many instances, clinical outcome has been shown to correlate with which ligand is expressed. We hypothesize that the structurally diverse oncogenic EGFRs are functionally different and that certain combinations of EGFR variant and ligand are more transforming than others. The goal of my laboratory is to elucidate the fundamental principles underlying signaling via receptor tyrosine kinases and to apply this to understand how mutant EGFRs induce tumors. The specific aims of this proposal are to: 1. Determine how inter-tyrosine sequences modulate the binding of SH2 domain proteins to the C-terminal tail of the EGFR; and, 2) Identify functional differences among oncogenic EGFRs and their response to EGFR agonists that are relevant to how transformation is established and maintained.