Zhuang Ting, Yu Sifan, Zhang Lichen, Yang Huijie, Li Xin, Hou Yingxiang, Liu Zhenhua, Shi Yuanyuan, Wang Weilong, Yu Na, Li Anqi, Li Xuefeng, Li Xiumin, Niu Gang, Xu Juntao, Hasni Muhammad Sharif, Mu Kun, Wang Hui, Zhu Jian
Research Center for Immunology, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, Henan, China.
Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, Xinxiang Medical University, Xinxiang, Henan, China.
Oncotarget. 2017 Aug 19;8(44):77137-77151. doi: 10.18632/oncotarget.20368. eCollection 2017 Sep 29.
Estrogen receptor α is expressed in the majority of breast cancers and promotes estrogen-dependent cancer progression. In our study, we identified the novel E3 ubiquitin ligase SHARPIN function to facilitate ERα signaling. SHARPIN is highly expressed in human breast cancer and correlates with ERα protein level by immunohistochemistry. SHARPIN expression level correlates with poor prognosis in ERα positive breast cancer patients. SHARPIN depletion based RNA-sequence data shows that ERα signaling is a potential SHARPIN target. SHARPIN depletion significantly decreases ERα protein level, ERα target genes expression and estrogen response element activity in breast cancer cells, while SHARPIN overexpression could reverse these effects. SHARPIN depletion significantly decreases estrogen stimulated cell proliferation in breast cancer cells, which effect could be further rescued by ERα overexpression. Further mechanistic study reveals that SHARPIN mainly localizes in the cytosol and interacts with ERα both in the cytosol and the nuclear. SHARPIN regulates ERα signaling through protein stability, not through gene expression. SHARPIN stabilizes ERα protein via prohibiting ERα protein poly-ubiquitination. Further study shows that SHARPIN could facilitate the mono-ubiquitinaiton of ERα at K302/303 sites and facilitate ERE luciferase activity. Together, our findings propose a novel ERα modulation mechanism in supporting breast cancer cell growth, in which SHARPIN could be one suitable target for development of novel therapy for ERα positive breast cancer.
雌激素受体α在大多数乳腺癌中表达，并促进雌激素依赖性癌症进展。在我们的研究中，我们确定了新型E3泛素连接酶SHARPIN促进雌激素受体α（ERα）信号传导的功能。SHARPIN在人类乳腺癌中高表达，并且通过免疫组织化学与ERα蛋白水平相关。SHARPIN表达水平与ERα阳性乳腺癌患者的不良预后相关。基于SHARPIN缺失的RNA序列数据表明，ERα信号传导是SHARPIN的一个潜在靶点。SHARPIN缺失显著降低乳腺癌细胞中ERα蛋白水平、ERα靶基因表达和雌激素反应元件活性，而SHARPIN过表达可逆转这些效应。SHARPIN缺失显著降低雌激素刺激的乳腺癌细胞增殖，ERα过表达可进一步挽救这种效应。进一步的机制研究表明，SHARPIN主要定位于细胞质中，并在细胞质和细胞核中与ERα相互作用。SHARPIN通过蛋白质稳定性而非基因表达来调节ERα信号传导。SHARPIN通过阻止ERα蛋白多聚泛素化来稳定ERα蛋白。进一步研究表明，SHARPIN可促进ERα在K302/303位点的单泛素化，并促进雌激素反应元件荧光素酶活性。总之，我们的研究结果提出了一种支持乳腺癌细胞生长的新型ERα调节机制，其中SHARPIN可能是开发ERα阳性乳腺癌新疗法的一个合适靶点。
