Keratin 18 attenuates estrogen receptor alpha-mediated signaling by sequestering LRP16 in cytoplasm.
Keratin 18 attenuates estrogen receptor alpha-mediated signaling by sequestering LRP16 in cytoplasm.
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角蛋白 18 通过将 LRP16 隔离在细胞质中来减弱雌激素受体 α 介导的信号传导
DOI：
10.1186/1471-2121-10-96
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发表时间：
2009-12-26
期刊：
影响因子：
--
通讯作者：
Han W
中科院分区：
文献类型：
--
作者：
Meng Y;Wu Z;Yin X;Zhao Y;Chen M;Si Y;Yang J;Fu X;Han W
乳腺癌的发生往往与雌激素受体α(ERα)的过度激活及其辅活化子的过度表达有关。LRP16既是ERα靶基因，又是ERα共激活因子，在乳腺癌细胞ERα活化和增殖中发挥重要作用。然而，对该辅活化子蛋白功能可用性的调节尚不清楚。酵母双杂交筛选、GST下拉和免疫共沉淀(CoIP)鉴定胞质中间丝蛋白K18(K18)是一种与LRP16相互作用的新蛋白。荧光分析表明，GFP标记的LRP16主要定位于模拟转染组MCF-7细胞的胞核中，而主要存在于K18转染组的细胞质中。免疫印迹分析显示，高表达K18的细胞胞浆LRP16含量显着增加，而核表达水平降低。相反，下调MCF-7细胞内源性K18的表达显著降低LRP16的胞浆水平，增加胞核的水平。CoIP未检测到K18和ERα之间的任何相互作用，但K18在MCF-7细胞中的异位表达显著减弱了LRP16与ERα的联系，减弱了ERα激活的报告基因活性，并通过抑制ERα的募集而减少了雌激素刺激的靶基因的表达。BrdU掺入实验表明，K18过表达抑制了雌激素诱导的MCF7细胞进入S期的增加。相比之下，K18基因在MCF-7细胞中的敲除显著增加了ERα介导的信号转导，并促进了细胞周期的进展。K18可以有效地结合和隔离胞浆中的LRP16，从而减弱ERα介导的信号最终输出和雌激素刺激的MCF-7乳腺癌细胞的细胞周期进展。K18的缺失增加了LRP16对ERα的功能利用率，并促进了ERα阳性乳腺肿瘤细胞的增殖。K18在调节ERα信号通路中起着重要的作用。
Oncogenesis in breast cancer is often associated with excess estrogen receptor α(ERα) activation and overexpression of its coactivators. LRP16 is both an ERα target gene and an ERα coactivator, and plays a crucial role in ERα activation and proliferation of MCF-7 breast cancer cells. However, the regulation of the functional availability of this coactivator protein is not yet clear. Yeast two-hybrid screening, GST pulldown and coimmunoprecipitation (CoIP) identified the cytoplasmic intermediate filament protein keratin 18 (K18) as a novel LRP16-interacting protein. Fluorescence analysis revealed that GFP-tagged LRP16 was primarily localized in the nuclei of mock-transfected MCF-7 cells but was predominantly present in the cytoplasm of K18-transfected cells. Immunoblotting analysis demonstrated that the amount of cytoplasmic LRP16 was markedly increased in cells overexpressing K18 whereas nuclear levels were depressed. Conversely, knockdown of endogenous K18 expression in MCF-7 cells significantly decreased the cytoplasmic levels of LRP16 and increased levels in the nucleus. CoIP failed to detect any interaction between K18 and ERα, but ectopic expression of K18 in MCF-7 cells significantly blunted the association of LRP16 with ERα, attenuated ERα-activated reporter gene activity, and decreased estrogen-stimulated target gene expression by inhibiting ERα recruitment to DNA. Furthermore, BrdU incorporation assays revealed that K18 overexpression blunted the estrogen-stimulated increase of S-phase entry of MCF-7 cells. By contrast, knockdown of K18 in MCF-7 cells significantly increased ERα-mediated signaling and promoted cell cycle progression. K18 can effectively associate with and sequester LRP16 in the cytoplasm, thus attenuating the final output of ERα-mediated signaling and estrogen-stimulated cell cycle progression of MCF-7 breast cancer cells. Loss of K18 increases the functional availability of LRP16 to ERα and promotes the proliferation of ERα-positive breast tumor cells. K18 plays an important functional role in regulating the ERα signaling pathway.
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DOI：
10.1186/bcr1748
发表时间：
2007
期刊：
Breast cancer research : BCR
影响因子：
--
作者：
Fowler AM;Alarid ET
通讯作者：
Alarid ET
DOI：
10.1083/jcb.110.4.1199
发表时间：
1990-04
期刊：
The Journal of cell biology
影响因子：
--
作者：
Hatzfeld M;Weber K
通讯作者：
Weber K
影响因子：
4.8
作者：
Aguiar, RCT;Takeyama, K;Shipp, MA
通讯作者：
Shipp, MA
影响因子：
4.8
作者：
Bocchinfuso, WP;Lindzey, JK;Korach, KS
通讯作者：
Korach, KS
DOI：
10.1083/jcb.200103078
发表时间：
2001-10-29
期刊：
The Journal of cell biology
影响因子：
--
作者：
Inada H;Izawa I;Nishizawa M;Fujita E;Kiyono T;Takahashi T;Momoi T;Inagaki M
通讯作者：
Inagaki M