Article

RNF6 promotes myeloma cell proliferation and survival by inducing glucocorticoid receptor polyubiquitination

Ying Ren1, Xin Xu1, Chen-yu Mao2, Kun-kun Han1, Yu-jia Xu1, Bi-yin Cao1, Zu-bin Zhang1, Gautam Sethi3, Xiao-wen Tang4, Xin-liang Mao1,4,5
1 Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China
2 School of Medicine, South University of Science and Technology, Shenzhen 518055, China
3 Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
4 National Clinical Research Center for Hematologic Diseases, Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215100, China
5 Protein Modification and Degradation Key Lab of Guangzhou and Guangdong, School of Basic Medical Sciences, Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou 511436, China
Correspondence to: Xiao-wen Tang: xwtang1020@163.com, Xin-liang Mao: xinliangmao@gzhmu.edu.cn,
DOI: 10.1038/s41401-019-0309-6
Foundation:
multiple myeloma; RNF6; glucocorticoid receptor; ubiquitin-proteasome pathway; apoptosis; dexamethasone,
Received: 13 June 2019
Accepted: 12 September 2019
Advance online: 23 October 2019

Abstract

RNF6, a RING-type ubiquitin ligase, has been identified as an oncogene in various cancers but its role in multiple myeloma (MM) remains elusive. In the present study we first showed that the expression levels of RNF6 in MM were significantly elevated compared with the bone marrow cells of healthy donors. Overexpression of RNF6 in LP1 and PRMI-8266 MM cell lines promoted cell proliferation, whereas knockdown of RNF6 led to apoptosis of MM cells. Furthermore, we revealed that RNF6, as a ubiquitin ligase, interacted with glucocorticoid receptor (GR) and induced its K63-linked polyubiquitination. Different from current knowledge, RNF6 increased GR stability at both endogenous and exogenous contexts. Such an action greatly promoted GR transcriptional activity, which was confirmed by luciferase assays and by the increased expression levels of prosurvival genes including Bcl-xL and Mcl-1, two typical downstream genes of the GR pathway. Consistent with these findings, ectopic expression of RNF6 in MM cells conferred resistance to dexamethasone, a typical anti-myeloma agent. In conclusion, we demonstrate that RNF6 promotes MM cell proliferation and survival by inducing atypical polyubiquitination to GR, and RNF6 could be a promising therapeutic target for the treatment of MM.
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