Janes P W, Daly R J, deFazio A, Sutherland R L
Cancer Biology Division, Garvan Institute of Medical Research, St Vincent's Hospital, Sydney, NSW, Australia.
Oncogene. 1994 Dec;9(12):3601-8.
The c-erbB-2 proto-oncogene encodes a receptor tyrosine kinase (RTK) closely related to the epidermal growth factor receptor (EGFR). Overexpression of erbB-2 occurs in approximately 20% of human breast tumours, where increased expression correlates with poor patient prognosis. The EGFR is coupled to the Ras signalling pathway by interaction with the adaptor protein Grb2, and Sos, a Ras GDP-GTP exchange factor. In this study, activation of the erbB-2 receptor and its association with Grb2 and Sos was investigated in breast cancer cell lines which overexpress erbB-2. The receptor was found to be tyrosine phosphorylated in all cell lines in which it is overexpressed. Western blotting of Grb2 and Sos immuneprecipitates from such cells revealed co-precipitation of erbB-2, demonstrating association of the Grb2/Sos complex with erbB-2 in vivo. Furthermore, a fusion protein containing only the SH2 domain of Grb2 bound to erbB-2 immobilized on nitrocellulose, indicating that association with Grb2 is direct and mediated by the SH2 domain of Grb2. The degree of association between the erbB-2 receptor and Grb2 in vivo was related to erbB-2 overexpression, and MAP kinase, which functions downstream from Ras, displayed markedly increased activity in cell lines overexpressing erbB-2. These results demonstrate that erbB-2 is coupled to Ras signalling via the Grb2/Sos complex, and that overexpression of this receptor in breast cancer cells leads to amplification of the Ras signalling pathway.
c-erbB-2原癌基因编码一种与表皮生长因子受体（EGFR）密切相关的受体酪氨酸激酶（RTK）。erbB-2在约20%的人类乳腺肿瘤中过度表达，其表达增加与患者预后不良相关。EGFR通过与衔接蛋白Grb2以及Ras GDP-GTP交换因子Sos相互作用，与Ras信号通路偶联。在本研究中，在过表达erbB-2的乳腺癌细胞系中研究了erbB-2受体的激活及其与Grb2和Sos的关联。发现在所有过表达该受体的细胞系中，该受体均发生酪氨酸磷酸化。对来自此类细胞的Grb2和Sos免疫沉淀产物进行蛋白质印迹分析，结果显示erbB-2共沉淀，这表明在体内Grb2/Sos复合物与erbB-2有关联。此外，一种仅包含Grb2的SH2结构域的融合蛋白与固定在硝酸纤维素膜上的erbB-2结合，这表明与Grb2的关联是直接的，且由Grb2的SH2结构域介导。erbB-2受体与Grb2在体内的关联程度与erbB-2的过表达有关，并且在Ras下游起作用的丝裂原活化蛋白激酶（MAP激酶）在过表达erbB-2的细胞系中活性显著增加。这些结果表明，erbB-2通过Grb2/Sos复合物与Ras信号通路偶联，并且该受体在乳腺癌细胞中的过表达导致Ras信号通路的放大。
