应用膜蛋白纳米组装研究EGFR/HER2过表达致癌的分子机理与结构

Epidermal growth factor receptor (EGFR) and its homologs (HER2,HER3, and HER4) belong to receptor tyrosine kinase (RTK) superfamily. They regulate important cellular functions, including cell growth, differentiation,and proliferation. Dysregulation of these receptor transmembrane signaling, either by mutation or by overexpression, leads to tumorgenesis. Therefore, they are validated therapeutic targets in the treatment of various cancers, such as lung and breast cancer. Although significant progress had been achieved in understanding the basis for oncogenesis associated with EGFR kinase mutation, less is known about how the transmembrane signaling is dysregulated by EGFR/HER2 overexpression, and how EGFR/HER2 overexpression contribute to oncogenesis and drug resistance. This proposal aims to 1) apply newly developed lipid nanodisc technique to functionally reconstitute high density EGFR or HER2 complexes into lipid membrane, and 2) study the basis for following open questions: how does EGFR/HER2 overexpression cause the dysregulation of receptor transmembrane signaling? how do therapeutic antibodies targeting EGFR or HER2 extracellular domain modulate receptor transmembrane signaling? and how do these antibodies coordinate with kinase inhibitors through lipid membrane in combinational therapy? These studies are of conceptional importance in understanding the biology of RTK transmembrane signaling. They also have implications in novel therapeutic development targeting EGFR or HER2 overexpression in cancer.

EGFR(表皮生长因子受体）及其同源蛋白HER2, HER3, HER4是调控细胞生长与分化的重要酪氨酸激酶受体。这些受体的突变或过表达将引起激酶活性的失调，并导致包括肺癌与乳腺癌在内的各种癌症。因此，这些受体是治疗癌症的重要药物靶底。目前对于EGFR激酶突变所引起的激酶活性失控及其致癌机理已有较深入地研究，但对于由EGFR或HER2过表达所引发的跨膜信号变化，相应的分子结构，及由此导致的癌症发生与耐药性产生的分子机理均所知甚少，在临床上也缺乏有效的靶向性药物或治疗窗口。本项目旨在应用纳米磷脂盘技术在体外脂膜环境下重构EGFR或HER2过表达的功能性膜蛋白复合物，并以此为基础应用电镜、生物物理、生物化学和细胞生物学综合手段研究由EGFR或HER2过表达引起的跨膜信号传导失调及其致癌的分子结构与机理。我们还将进一步阐明针对这一失调信号的抗体药物和抗体药物/激酶抑制剂结合的组合疗法的作用机制。

表皮生长因子受体家族成员EGFR和HER2参与多种细胞生物学功能调控。由这两个受体的过表达或激活突变导致的功能性失调与多种癌症的发生、发展、转移密切相关。但目前为止，对于这些只具有单次跨膜螺旋的受体的全长结构、这些受体如何通过单次跨膜螺旋实现跨膜信号传导、以及靶向这些受体的药物联合作用的效能与机理等问题均不甚明了。在基金委的资助下，我们对于上述问题进行了研究，并取得了如下进展：.1、利用冷冻电镜研究了全长EGFR在磷脂纳米盘中的结构，发现在脂膜中，结合配体的EGFR的胞内域相对于其胞外域存在连续的构象/取向变化。.2、利用荧光蛋白互补技术研究了EGFR/HER2跨膜信号偶联以及靶向二者的抗体药物与激酶抑制剂的协同/拮抗作用及其分子机理。.3、设计、开发了靶向EGFR致癌相关构象的模块化诊疗探针.4、阐明了经典酪氨酸激酶受体PDGFRβ的别构激活机理