Coleman Kevin M, Dutertre Martin, El-Gharbawy Abeer, Rowan Brian G, Weigel Nancy L, Smith Carolyn L
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030-3498, USA.
J Biol Chem. 2003 Apr 11;278(15):12834-45. doi: 10.1074/jbc.M212312200. Epub 2003 Jan 31.
Although increases in intracellular cAMP can stimulate estrogen receptor-alpha (ER alpha) activity in the absence of exogenous hormone, no studies have addressed whether ER beta can be similarly regulated. In transient transfections, forskolin plus 3-isobutyl-1-methylxanthine (IBMX), which increases intracellular cAMP, stimulated the transcriptional activities of both ER alpha and ER beta. This effect was blocked by the protein kinase A inhibitor H89 (N-(2-(p-bromocinnamylamino)-ethyl)-5-isoquinolinesulfonamide) and was dependent on an estrogen response element. A 12-O-tetradecanoylphorbol-13-acetate response element (TRE) located 5' to the estrogen response element was necessary for cAMP-dependent activation of gene expression by ER beta but not ER alpha, indicating that the former subtype requires a functional interaction with TRE-interacting factor(s) to stimulate transcription. Both p160 and CREB-binding protein coactivators stimulated cAMP-induced ER alpha and ER beta transcriptional activity. However, mutation of the two cAMP-inducible SRC-1 phosphorylation sites important for cAMP activation of chicken progesterone receptor or all seven known SRC-1 phosphorylation sites did not specifically impair cAMP activation of ER alpha. The E/F domains of ER alpha are sufficient for activation by forskolin/IBMX, and this is accompanied by an increase in receptor phosphorylation. In contrast, cAMP signaling reduces the phosphorylation of the corresponding region of ER beta, and this correlates with the lack of forskolin/IBMX stimulated transcriptional activity. Our data suggest that cAMP activation of ER alpha transcriptional activity is associated with receptor instead of SRC-1 phosphorylation. Moreover, differences in the cofactor requirements, domains of ER alpha and ER beta sufficient for forskolin/IBMX activation, and the effect of cAMP on receptor phosphorylation indicate that this signaling pathway utilizes distinct mechanisms to stimulate ER alpha and ER beta transcriptional activity.
尽管在没有外源性激素的情况下，细胞内cAMP的增加可刺激雌激素受体α（ERα）的活性，但尚无研究探讨ERβ是否能受到类似的调节。在瞬时转染中，可增加细胞内cAMP的福斯高林加3 - 异丁基 - 1 - 甲基黄嘌呤（IBMX）刺激了ERα和ERβ的转录活性。这种效应被蛋白激酶A抑制剂H89（N - （2 - （对溴肉桂酰胺基） - 乙基） - 5 - 异喹啉磺酰胺）阻断，并且依赖于雌激素反应元件。位于雌激素反应元件5'端的12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯反应元件（TRE）对于ERβ而非ERα的cAMP依赖性基因表达激活是必需的，这表明前一种亚型需要与TRE相互作用因子进行功能性相互作用以刺激转录。p160和CREB结合蛋白共激活因子均刺激了cAMP诱导的ERα和ERβ转录活性。然而，对鸡孕酮受体cAMP激活重要的两个cAMP诱导型SRC - 1磷酸化位点或所有七个已知的SRC - 1磷酸化位点发生突变，并未特异性损害ERα的cAMP激活。ERα的E/F结构域足以被福斯高林/IBMX激活，并且这伴随着受体磷酸化的增加。相比之下，cAMP信号传导降低了ERβ相应区域的磷酸化，这与缺乏福斯高林/IBMX刺激的转录活性相关。我们的数据表明，ERα转录活性的cAMP激活与受体而非SRC - 1磷酸化相关。此外，辅因子需求、福斯高林/IBMX激活所需的ERα和ERβ结构域以及cAMP对受体磷酸化的影响方面的差异表明，该信号通路利用不同机制来刺激ERα和ERβ转录活性。
