SHARPIN stabilizes estrogen receptor α and promotes breast cancer cell proliferation

// Ting Zhuang 1, 2, * , Sifan Yu 1, 2, 3 * , Lichen Zhang 1, 2, 4 * , Huijie Yang 1, 2 , Xin Li 1, 2 , Yingxiang Hou 1, 2 , Zhenhua Liu 1, 2, 5 , Yuanyuan Shi 1, 2 , Weilong Wang 6, 7 , Na Yu 6, 7 , Anqi Li 1, 2, 8 , Xuefeng Li 9 , Xiumin Li 6, 7 , Gang Niu 10, 11, 12 , Juntao Xu 10, 11, 12 , Muhammad Sharif Hasni 12, 13 , Kun Mu 14 , Hui Wang 1, 2 and Jian Zhu 1, 2, 15 1 Research Center for Immunology, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, Henan, China 2 Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, Xinxiang Medical University, Xinxiang, Henan, China 3 Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Department of Renal Cancer and Melanoma, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing, China 4 Laboratory of Genetic Regulators in the Immune System, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, Henan, China 5 Synthetic Biology Remaking Engineering and Application Laboratory, School of Life Sciences and Technology, Xinxiang Medical University, Xinxiang, Henan, China 6 Department of Gastroenterology, The Third Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan, China 7 Center for Cancer Research, Xinxiang Medical University, Xinxiang, Henan, China 8 School of International Education, Xinxiang Medical University, Xinxiang, Henan, China 9 Department of Medical Oncology, The First Affiliated Hospital, University of South China, Hengyang, Hunan, China 10 Department of Cancer genomics, LemonData biotech (Shenzhen) Ltd, Shenzhen, Guangdong, China 11 Phil Rivers Technology (Beijing) Ltd. Beijing, China 12 Institute of Biochemistry University of Balochistan, Quetta, Pakistan 13 Department of Hematology and Transfusion Medicine, Lund University, Lund, Sweden 14 Department of Pathology, School of Medicine, Shandong University, Jinan, Shandong, China 15 Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA * Ting Zhuang, Sifan Yu and Lichen Zhang contribute equally to this study Correspondence to: Jian Zhu, email: jian.zhu@utsouthwestern.edu Ting Zhuang, email: zhuangting_83@qq.com Hui Wang, email: wanghui@xxmu.edu.cn Kun Mu, email: mukun@sdu.edu.cn Keywords: SHARPIN, ER alpha, breast cancer, ubiquitination, protein stability Received: May 17, 2017      Accepted: June 29, 2017      Published: August 19, 2017 ABSTRACT 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.