Induction of hTERT expression and phosphorylation by estrogen via Akt cascade in human ovarian cancer cell lines
Induction of hTERT expression and phosphorylation by estrogen via Akt cascade in human ovarian cancer cell lines
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DOI：
10.1038/sj.onc.1207582
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发表时间：
2004-06-03
期刊：
影响因子：
8
通讯作者：
Murata, Y
中科院分区：
文献类型：
--
作者：
Kimura, A;Ohmichi, M;Murata, Y
我们研究了雌激素调节Caov-3人卵巢癌细胞系端粒酶活性的机制，该细胞系表达ER，以确定该调节是否影响端粒酶催化亚基（hTERT）的表达和/或磷酸化。17 β-雌二醇（E-2）诱导端粒酶活性和hTERT表达。使用荧光素酶报告质粒含有hTERT启动子的各种片段的瞬时表达试验表明，雌激素反应元件似乎是部分负责E-2诱导的hTERT启动子的激活。无论是用磷脂酰肌醇3-激酶（PI 3 K）抑制剂LY 294002预处理，还是用显性阴性Akt转染，都减弱了E-2诱导的hTERT启动子的激活。此外，雌激素通过Akt级联反应诱导IkappaB抑制蛋白磷酸化，与NF κ B显性负性亚基共转染减弱了ERE缺失的hTERT启动子对E2的反应。E2还以Akt依赖的方式诱导hTERT磷酸化、14-3-3蛋白和NF κ B与hTERT的结合以及hTERT在核内的聚集。这些结果表明，E-2诱导端粒酶活性不仅通过ERE依赖性机制和PI 3 K/Akt/NF κ B级联对hTERT进行转录调节，而且通过Akt依赖性hTERT磷酸化进行转录后调节。因此，Akt的磷酸化是E-2诱导人卵巢癌细胞端粒活性的关键事件。
We examined the mechanism by which estrogen regulates telomerase activity in Caov-3 human ovarian cancer cell lines, which express ER, to determine whether the regulation affects the expression and/or phosphorylation of the telomerase catalytic subunit (hTERT). 17beta-Estradiol (E-2) induced telomerase activity and hTERT expression. Transient expression assays using luciferase reporter plasmids containing various fragments of hTERT promoter showed that the estrogen-responsive element appeared to be partially responsible for the E-2-induced activation of the hTERT promoter. Either pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, or transfection with a dominant-negative Akt attenuated the E-2-induced activation of the hTERT promoter. In addition, estrogen induced the phosphorylation Of IkappaB inhibitor protein via the Akt cascade, and cotransfection with a dominant-negative subunit of NFkappaB attenuated the response of the ERE-deleted hTERT promoter to E-2-Moreover, E2 induced the phosphorylation of hTERT, the association of 14-3-3 protein and NFkappaB with hTERT, and nuclear accumulation of hTERT in an Akt-dependent manner. These results indicate that E-2 induces telomerase activity not only by transcriptional regulation of hTERT via an ERE-dependent mechanism and a PI3K/Akt/NFkappaB cascade, but also by post-transcriptional regulation via Akt-dependent phosphorylation of hTERT. Thus, the phosphorylation of Akt is a key event in the induction of telomeras activity by E-2 in human ovarian cancer cells.