Department of Biochemistry and Molecular Biology, Capital Medical University, No. 10 Xitoutiao, You An Men, Beijing 100069, People's Republic of China.
Endocrinology. 2011 Dec;152(12):4537-49. doi: 10.1210/en.2011-1207. Epub 2011 Oct 11.
Expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) can be induced by estrogens at the posttranscriptional level. However, the molecular mechanism of the process is unclear. In this study, we found that the C terminus (CT) of PTEN is indispensable for 17-β-estradiol (E2)-increased PTEN expression. Therefore, we screened for PTEN-CT-associated proteins using a glutathione-S-transferase pull-down approach in combination with mass spectrometry-based proteomic analyses. Our experiments led to the identification of Na(+)/H(+) exchanger regulatory factor 1 (NHERF1) as a major PTEN-CT binding partner. The first postsynaptic density protein-95/Discslarge/zonula occludens-1 homology domain of NHERF1 and the last four amino acids of PTEN were found to be key determinants of this interaction. By associating with PTEN, NHERF1 could enhance PTEN protein expression by retention of PTEN turnover, as demonstrated by NHERF1 overexpression and small interfering RNA-mediated knockdown experiments, respectively. Furthermore, NHERF1 inhibited ubiquitination of the PTEN protein upon competition with binding of PTEN to neural precursor cell expressed, developmentally down-regulated 4, an ubiquitin E3 ligase. E2 strongly induced the expression of NHERF1 and PTEN only in estrogen receptor (ER)-positive cells but not in ER-negative cells. ICI182780, an ER-specific inhibitor, decreased the expression of both NHERF1 and PTEN, and ICI182780 pretreatment also retarded E2-increased PTEN expression in ER-MDA-MB-231 cells. In both ER-MDA-MB-231 and MCF-7 cells, E2 failed to increase PTEN expression when NHERF1 was knocked down. Taken together, these are the first results that present a possible mechanism for E2-increased PTEN expression. In this process, E2 first induces NHERF1 expression by activating the ER. Upon competition with neural precursor cell expressed, developmentally down-regulated 4, NHERF1 then interacts with PTEN to inhibit PTEN degradation, through an ubiquitination-dependent pathway. This in turn leads to the increase of PTEN expression at the protein level.
磷酸酶与张力蛋白同源物基因缺失的染色体 10 号（PTEN）的表达可通过雌激素在转录后水平诱导。然而，这个过程的分子机制尚不清楚。在这项研究中，我们发现 PTEN 的 C 端（CT）对于 17-β-雌二醇（E2）增加 PTEN 表达是必不可少的。因此，我们使用谷胱甘肽 S-转移酶下拉方法结合基于质谱的蛋白质组学分析筛选与 PTEN-CT 相关的蛋白。我们的实验导致鉴定出钠离子/氢离子交换调节因子 1（NHERF1）作为主要的 PTEN-CT 结合伴侣。NHERF1 的第一个后突触密度蛋白 95/Discslarge/zonula occludens-1 同源结构域和 PTEN 的最后四个氨基酸被发现是这种相互作用的关键决定因素。通过与 PTEN 结合，NHERF1 可以通过保留 PTEN 周转来增强 PTEN 蛋白表达，这分别通过 NHERF1 的过表达和小干扰 RNA 介导的敲低实验证明。此外，NHERF1 抑制了 PTEN 蛋白的泛素化，这是通过与 PTEN 与神经前体细胞表达的、发育下调 4 竞争结合来实现的，神经前体细胞表达的、发育下调 4 是一种泛素 E3 连接酶。E2 仅在雌激素受体（ER）阳性细胞中强烈诱导 NHERF1 和 PTEN 的表达，而在 ER 阴性细胞中则不诱导。ICI182780，一种 ER 特异性抑制剂，降低了 NHERF1 和 PTEN 的表达，ICI182780 预处理也延缓了 ER-MDA-MB-231 细胞中 E2 增加的 PTEN 表达。在 ER-MDA-MB-231 和 MCF-7 细胞中，当 NHERF1 被敲低时，E2 未能增加 PTEN 表达。总的来说，这些是首次提出 E2 增加 PTEN 表达的可能机制的结果。在这个过程中，E2 首先通过激活 ER 诱导 NHERF1 表达。与神经前体细胞表达的、发育下调 4 竞争后，NHERF1 与 PTEN 相互作用，通过泛素化依赖途径抑制 PTEN 降解，从而导致 PTEN 蛋白水平表达增加。
