STAT5b, a mediator of synergism between c-Src and the epidermal growth factor receptor
STAT5b, a mediator of synergism between c-Src and the epidermal growth factor receptor
复制标题
DOI：
10.1074/jbc.m207289200
复制
发表时间：
2003-01-17
影响因子：
4.8
通讯作者：
Silva, CM
中科院分区：
文献类型：
--
作者：
Kloth, MT;Laughlin, KK;Silva, CM
表皮生长因子受体(EGFR)的过度表达及其与酪氨酸激酶c-Src的关系与细胞增殖和肿瘤发生有关。以往的研究表明，EGFR和c-Src的共同过表达和联合导致了c-Src介导的EGFR酪氨酸845的磷酸化，Tyr(845)突变会抑制表皮生长因子(EGF)诱导的DNA合成。在这里，我们研究了信号转导和转录激活因子(STAT5b)在人乳腺肿瘤细胞系和小鼠成纤维细胞模型(C3H10T1/2)中由EGFR和c-Src过表达调控的信号通路中的作用。我们证明：1)EGF激活STAT5b需要EGFR的过表达，2)c-Src的共同过表达不会导致EGF诱导的STAT5b的激活，但会增强在EGFR过表达的细胞中看到的激活，以及3)EGF诱导的STAT5b的酪氨酸磷酸化需要EGFR的Tyr845。此外，在EGFR过表达的背景下，激酶缺陷的c-Src的稳定过表达导致EGF响应的STAT5b的酪氨酸磷酸化减少，并且EGF诱导的STAT5b的转录激活更显著地降低，这表明c-Src在STAT5b的生理作用中起着不可或缺的作用。使用显性负的STAT5b，我们提供了证据表明，这样的生理作用之一是介导EGF诱导的DNA合成。最后，使用定点酪氨酸突变体表明，EGF诱导的STAT5b的磷酸化不仅涉及其转录激活所需的STAT5b的699酪氨酸，而且还涉及先前发现的STAT5b C末端的三个酪氨酸(Tyr(725)/Tyr(740)/Tyr(743))。
Overexpression of the epidermal growth factor receptor (EGFR) and its association with the tyrosine kinase, c-Src, is correlated with increased cellular proliferation and tumorigenesis. Previous studies have shown that EGFR and c-Src co-overexpression and association leads to the c-Src-mediated phosphorylation of tyrosine 845 of the EGFR and that mutation of Tyr(845) ablates epidermal growth factor (EGF)-induced DNA synthesis. Here, we investigate the contribution of the signal transducers and activators of transcription (STAT5b) in the signaling pathways regulated by EGFR and c-Src overexpression in human breast tumor cell lines as well as in a mouse fibroblast model (C3H10T1/2). We demonstrate that 1) activation of STAT5b by EGF requires overexpression of the EGFR, 2) co-overexpression of c-Src alone does not result in EGF-induced activation of STAT5b but enhances that seen in EGFR-overexpressing cells, and 3) EGF-induced tyrosine phosphorylation of STAT5b requires Tyr845 of the EGFR. Furthermore, the stable overexpression of a kinase-defective c-Src in the context of EGFR overexpression results in a decrease in the tyrosine phosphorylation of STAT5b in response to EGF and a more dramatic decrease in EGF-induced transcriptional activation of STAT5b, suggesting an integral role for c-Src in the physiological actions of STAT5b. Using a dominant negative STAT5b, we provide evidence that one such physiological action is to mediate EGF-induced DNA-synthesis. Finally, the use of site-specific tyrosine mutants demonstrates that EGF-induced phosphorylation of STAT5b involves not only tyrosine 699 of STAT5b, which is required for its transcriptional activation, but also three previously identified tyrosines in the C terminus of STAT5b (Tyr(725)/Tyr(740)/Tyr(743)).