MITOGENIC SIGNALLING ERBB/EGFR FAMILY AND ITS ROLE IN NEOPLASIA

我们最近分离了erbB/EGF受体的第三个成员， 并将其命名为erbB-3。 基于结构和 一种与酪氨酸蛋白激酶密切相关的跨膜酪氨酸激酶的生物化学特征 EGFR和erbB-2蛋白，我们研究了是否erbB-3 蛋白质作为生长因子受体发挥作用。 在没有 特异性erbB-3配体，我们设计了一种嵌合受体， EGFR的细胞外结构域和erbB-3的细胞质结构域 蛋白 转染NIH/3 T3细胞后， 载体和标记选择，我们可以证明erbB-3 信号传导功能是配体响应性的，如EGF依赖性 嵌合受体的酪氨酸磷酸化和促有丝分裂性。 在 此外，观察到高erbB-3磷酸酪氨酸水平， 某些人乳腺肿瘤细胞系提示组成性激活 erbB-3在人类肿瘤中的信号功能。 测量erbB-3 在体内酪氨酸磷酸化，我们已经确定了条件培养基 来自具有推定的erbB-3特异性配体活性的细胞系。 正在进行 研究集中在这种活性的蛋白质纯化上， erbB-3特异性配体的功能和分子表征。 此外，在erbB-3信号传导中重要的细胞质信号传导途径 使用嵌合EGFR/erbB-3研究转导 转染子

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.