ISOLATION AND CHARACTERIZATION OF THE EGF RECEPTOR PUTATIVE SUBSTRATE, EPS8

表皮生长因子（EGF）与其受体的结合激活了表皮生长因子受体。 受体的酪氨酸激酶活性。 后来。受激 受体磷酸化自身和其他细胞内蛋白质。 这些 细胞内蛋白质统称为EGF受体酪氨酸 激酶底物 开发了一种分离这些底物的方法 并获得了几个cDNA克隆。 表皮生长因子（EGF） 受体途径底物从NIH/3 T3细胞cDNA文库中获得。 之一 这些克隆eps 8编码97 kDa的蛋白质。 结果表明，eps 8 也被激活的EGF受体酪氨酸激酶磷酸化 与其他酪氨酸激酶一样。 eps 8与EGF受体结合。 尽管缺少SH 2结构域。 进一步确定， eps 8的区域对于其与EGF受体的相互作用是重要的。 重组eps 8在成纤维细胞或造血细胞中的过表达 增加细胞对促有丝分裂作用的反应和敏感性， EGF。 因此，eps 8可能参与EGF的转导。 信号. 序列分析显示eps 8中存在SH 3结构域。 A 65 kDa 鉴定了与eps 8的SH 3结构域结合的蛋白，并显示 这种蛋白质主要分布在细胞核中， cell.

Binding of epidermal growth factor (EGF) to its receptor activates the receptor's tyrosine kinase activity. Subsequently. the stimulated receptor phosphorylates itself and other intracellular proteins. These intracellular proteins are collectively termed EGF receptor tyrosine kinase substrates. A method was developed to isolate these substrates and several cDNA clones were obtained. They were designated eps for EGF receptor pathway substrate. from an NIH/3T3 cell cDNA library. One of these clones, eps8, encodes a protein of 97 kDa. It was shown that eps8 was phosphorylated by the activated EGF receptor tyrosine kinase as well as by other tyrosine kinases. eps8 binds to the EGF receptor directly. despite the absence of a SH2 domain. It was further determined that the regions of eps8 are important for its interaction with the EGF receptor. Overexpression of recombinant eps8 in fibroblasts or hematopoietic cells increases the cells response and sensitivity to the mitogenic action of EGF. Therefore, eps8 is likely involved in the transduction of EGF signals. Sequence analysis revealed a SH3 domain in eps8. A 65 kDa protein was identified that binds to the SH3 domain of eps8 and showed that this protein is mainly distributed in the nuclear fraction of the cell.