MITOGENIC SIGNALLING ERBB/EGFR FAMILY AND ITS ROLE IN NEOPLASIA

我们最近分离出了erbB/EGF受体的第三个成员 并将其命名为erbB-3。基于结构和 一种与之密切相关的跨膜酪氨酸激酶的生化特性 对于EGFR和erbB-2蛋白，我们研究了erbB-3 蛋白质具有生长因子受体的功能。在缺少 特异性的erbB-3配体，我们设计了一种包含 EGFR的胞外区和erbB-3的胞内区 蛋白。转染NIH/3T3细胞后的表达 载体和标记的选择，我们可以证明erbB-3 信号功能是配体反应的，如EGF依赖所示 嵌合受体的酪氨酸磷酸化和有丝分裂活性。在……里面 此外，观察到高水平的erbB-3磷酸酪氨酸。 某些人乳腺肿瘤细胞系显示出结构性激活 人类肿瘤中erbB-3信号转导功能的研究检测erbB-3 体内酪氨酸磷酸化，我们已经鉴定了条件培养液 从具有可能的erbB-3特异性配体活性的细胞系中分离出来。正在进行中 这一活性的蛋白质纯化是目前研究的重点。 一种erbB-3特异性配体的功能和分子特征。 此外，细胞质信号通路在erbB-3信号中起重要作用 利用嵌合的EGFR/erbB-3研究了信号转导 转染者。

We have recently isolated a third member of the erbB/EGF receptor subfamily and designated it as erbB-3. Based upon structural and biochemical features of a transmembrane tyrosine kinase closely related to the EGFR and erbB-2 proteins, we investigated whether the erbB-3 protein functions as a growth factor receptor. In the absence of a specific erbB-3 ligand we engineered a chimeric receptor containing the extracellular domain of the EGFR and the cytoplasmic domain of the erbB-3 protein. Following transfection of NIH/3T3 cells with the expression vector and marker selection, we could demonstrate that the erbB-3 signalling function is ligand responsive as indicated by EGF-dependent tyrosine phosphorylation and mitogenicity of the chimeric receptor. In addition, the observation of high erbB-3 phosphotyrosine levels in certain human breast tumor cell lines suggested constitutive activation of the erbB-3 signalling function in human neoplasia. Measuring erbB-3 tyrosine phosphorylation in vivo, we have identified conditioned medium from cells lines with putative erbB-3 specific ligand activity. Ongoing studies focus on the protein purification of this activity for the functional and molecular characterization of an erbB-3 specific ligand. Furthermore, cytoplasmic signalling pathways important in erbB-3 signal transduction are investigated employing the chimeric EGFR/erbB-3 transfectants.