EGFR in a sticky situation: probing structural transitions in dimerized receptors

描述(申请人提供)：令人信服的证据表明，目前的表皮生长因子受体(EGFR)信号的结构模型是不完整的，因为它们不能解释呈现负合作配体结合的细胞中不活跃的、预先组装的受体二聚体的数量。因此，EGFR信号不是通过简单的配体诱导的二聚化进行的，而是涉及受体二聚体的配体依赖的变构调节。这项提案描述了我将如何(I)获得对预先组装的EGFR二聚体的透彻结构的了解，(Ii)确定将受体二聚体在‘OFF’和‘ON’状态之间切换的构象变化，以及(Iii)研究被广泛讨论的EGFR癌基因突变和配体特定的‘ON’状态差异化地调节信号输出的可能性。我的初步数据显示，高度同源的线虫EGFR是结构性二聚体，它绕过了与人类EGFR相关的技术挑战，并提供了一个独特而直接的机会来回答这些重要的机制问题。由于过量的EGFR信号导致许多人类癌症，这一结果将为设计新一代更智能的EGFR靶向癌症疗法提供概念框架。

DESCRIPTION (provided by applicant): Compelling evidence suggests that current structural models of epidermal growth factor receptor (EGFR) signaling are incomplete, as they cannot account for the population of inactive, pre-assembled receptor dimers in cells that exhibit negatively cooperative ligand binding. Thus, rather than proceeding through simple ligand- induced dimerization, EGFR signaling involves the ligand-dependent allosteric regulation of receptor dimers. This proposal describes how I will (i) obtain a thorough structural understanding of pre-assembled EGFR dimers, (ii) identify the conformational changes that switch receptor dimers between the 'off' and 'on' states, and (iii) investigate the much-discussed possibilities of oncogenic mutation- and ligand-specific 'on' states of EGFR that differentially modulate signaling output. My preliminary data shows that the highly-homologous C. elegans EGFR is constitutively dimeric, which circumvents technical challenges associated with human EGFR and provides a unique and straightforward opportunity to answer these important mechanistic questions. Since excessive EGFR signaling drives many human cancers, the results will provide the conceptual framework for designing a new generation of 'smarter' EGFR-targeted cancer therapies.