Improta-Brears T, Whorton A R, Codazzi F, York J D, Meyer T, McDonnell D P
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4686-91. doi: 10.1073/pnas.96.8.4686.
Estrogens and growth factors such as epidermal growth factor (EGF) act as mitogens promoting cellular proliferation in the breast and in the reproductive tract. Although it was considered originally that these agents manifested their mitogenic actions through separate pathways, there is a growing body of evidence suggesting that the EGF and estrogen-mediated signaling pathways are intertwined. Indeed, it has been demonstrated recently that 17beta-estradiol (E2) can induce a rapid activation of mitogen-activated protein kinase (MAPK) in mammalian cells, an event that is independent of both transcription and protein synthesis. In this study, we have used a pharmacological approach to dissect this novel pathway in MCF-7 breast cancer cells and have determined that in the presence of endogenous estrogen receptor, activation of MAPK by E2 is preceded by a rapid increase in cytosolic calcium. The involvement of intracellular calcium in this process was supported by the finding that the presence of EGTA and Ca2+-free medium did not affect the activation of MAPK by E2 and, additionally, that this response was blocked by the addition of the intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate. Cumulatively, these data indicate that the estrogen receptor, in addition to functioning as a transcription factor, is also involved, through a nongenomic mechanism, in the regulation of both intracellular calcium homeostasis and MAPK-signaling pathways. Although nongenomic actions of estrogens have been suggested by numerous studies in the past, the ability to link estradiol and the estrogen receptor to a well defined signaling pathway strongly supports a physiological role for this activity.
雌激素和诸如表皮生长因子（EGF）等生长因子作为促细胞分裂剂，可促进乳腺和生殖道中的细胞增殖。尽管最初认为这些因子通过不同途径发挥其促有丝分裂作用，但越来越多的证据表明，EGF和雌激素介导的信号通路相互交织。事实上，最近已证明17β-雌二醇（E2）可在哺乳动物细胞中诱导丝裂原活化蛋白激酶（MAPK）的快速激活，这一事件与转录和蛋白质合成均无关。在本研究中，我们采用药理学方法剖析MCF-7乳腺癌细胞中的这一新通路，并确定在内源性雌激素受体存在的情况下，E2对MAPK的激活之前，胞质钙会快速增加。细胞内钙参与这一过程得到以下发现的支持：EGTA和无钙培养基的存在并不影响E2对MAPK的激活，此外，添加细胞内钙螯合剂1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸可阻断这一反应。累积起来，这些数据表明雌激素受体除了作为转录因子发挥作用外，还通过非基因组机制参与细胞内钙稳态和MAPK信号通路的调节。尽管过去众多研究已提示雌激素存在非基因组作用，但将雌二醇和雌激素受体与明确的信号通路联系起来的能力有力地支持了该活性的生理作用。
