Han Sang Jun, Begum Khurshida, Foulds Charles E, Hamilton Ross A, Bailey Suzanna, Malovannaya Anna, Chan Doug, Qin Jun, O'Malley Bert W
Department of Molecular and Cellular Biology (S.J.H., K.B., C.E.F., R.A.H, S.B., A.M., D.C., J.Q., B.W.O.), And Center for Molecular Discovery, Verna and Marrs McLean, Department of Biochemistry and Molecular Biology (A.M., D.C., J.Q.), Baylor College of Medicine, Houston, Texas.
Department of Molecular and Cellular Biology (S.J.H., K.B., C.E.F., R.A.H, S.B., A.M., D.C., J.Q., B.W.O.), And Center for Molecular Discovery, Verna and Marrs McLean, Department of Biochemistry and Molecular Biology (A.M., D.C., J.Q.), Baylor College of Medicine, Houston, Texas
Mol Pharmacol. 2016 Jan;89(1):14-26. doi: 10.1124/mol.115.100925. Epub 2015 Oct 20.
The conjugated estrogen /: bazedoxifene tissue-selective estrogen complex (TSEC) is designed to minimize the undesirable effects of estrogen in the uterus and breast tissues and to allow the beneficial effects of estrogen in other estrogen-target tissues, such as the bone and brain. However, the molecular mechanism underlying endometrial and breast safety during TSEC use is not fully understood. Estrogen receptor α (ERα)-estrogen response element (ERE)-DNA pull-down assays using HeLa nuclear extracts followed by mass spectrometry-immunoblotting analyses revealed that, upon TSEC treatment, ERα interacted with transcriptional repressors rather than coactivators. Therefore, the TSEC-mediated recruitment of transcriptional repressors suppresses ERα-mediated transcription in the breast and uterus. In addition, TSEC treatment also degraded ERα protein in uterine tissue and breast cancer cells, but not in bone cells. Interestingly, ERα-ERE-DNA pull-down assays also revealed that, upon TSEC treatment, ERα interacted with the F-box protein 45 (FBXO45) E3 ubiquitin ligase. The loss-of- and gain-of-FBXO45 function analyses indicated that FBXO45 is involved in TSEC-mediated degradation of the ERα protein in endometrial and breast cells. In preclinical studies, these synergistic effects of TSEC on ERα inhibition also suppressed the estrogen-dependent progression of endometriosis. Therefore, the endometrial and breast safety effects of TSEC are associated with synergy between the selective recruitment of transcriptional repressors to ERα and FBXO45-mediated degradation of the ERα protein.
共轭雌激素/巴多昔芬组织选择性雌激素复合物（TSEC）旨在将雌激素对子宫和乳腺组织的不良影响降至最低，并使雌激素在其他雌激素靶组织（如骨骼和大脑）中发挥有益作用。然而，TSEC使用过程中子宫内膜和乳腺安全性的分子机制尚未完全明确。利用HeLa细胞核提取物进行雌激素受体α（ERα）-雌激素反应元件（ERE）-DNA下拉试验，随后进行质谱免疫印迹分析，结果显示，经TSEC处理后，ERα与转录抑制因子而非共激活因子相互作用。因此，TSEC介导的转录抑制因子募集抑制了乳腺和子宫中ERα介导的转录。此外，TSEC处理还使子宫组织和乳腺癌细胞中的ERα蛋白降解，但在骨细胞中未出现这种情况。有趣的是，ERα-ERE-DNA下拉试验还显示，经TSEC处理后，ERα与F盒蛋白45（FBXO45）E3泛素连接酶相互作用。FBXO45功能缺失和功能获得分析表明，FBXO45参与TSEC介导的子宫内膜和乳腺细胞中ERα蛋白的降解。在临床前研究中，TSEC对ERα抑制的这些协同作用也抑制了子宫内膜异位症的雌激素依赖性进展。因此，TSEC的子宫内膜和乳腺安全作用与ERα选择性募集转录抑制因子和FBXO45介导的ERα蛋白降解之间的协同作用有关。
