Estrogen is known to participate in growth and development in various tissues. And all these cellular functions are mediated through estrogen receptor (ER) that is a nuclear transcription factor. Estrogen binding to the ER triggers a series of molecular events culminating in the activation or repression of target genes. All the physiological functions of estrogen can be attributed to the activated ER that acts as a transcription factor as well as the signaling pathsways that are induced or activated by estrogen. However, to date, the effects of estrogen on cellular signaling pathways are still unclear. Previously, it was demonstrated that tyrosine kinase inhibitors could block estrogen-induced mitogenesis. And upon estrogen stimulation, enhanced tyrosyl phosphorylation of total cellular proteins was detected. There were reports indicating the activiation of c-Src enzymatic activity, the enhancement of tyrosyl phopsphorylation of Shc and the activation of Ras/MAPK in response to estrogen. However, what happened to the other important tyrosine kinase, FAK, was still obscure. In the process of investigating the signaling pathways induced by estrogen, we unexpectedly observed that FAK was induced after estrogen treatment. To further study the phenomenon and its implicated significance, we are interested to design mammalian DNA expression constructs and generate cells overexpressing FAK to investigate the participation of FAK in estrogen-induced signaling.
