Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 21, 2015; 21(15): 4517-4525
Published online Apr 21, 2015. doi: 10.3748/wjg.v21.i15.4517
MicroRNA-185-5p mediates regulation of SREBP2 expression by hepatitis C virus core protein
Min Li, Qi Wang, Shun-Ai Liu, Jin-Qian Zhang, Wei Ju, Min Quan, Sheng-Hu Feng, Jin-Ling Dong, Ping Gao, Jun Cheng
Min Li, Sheng-Hu Feng, Jin-Ling Dong, Jun Cheng, Beijing Ditan Hospital, Teaching Hospital of Peking University, Beijing 100015, China
Qi Wang, Shun-Ai Liu, Jin-Qian Zhang, Wei Ju, Min Quan, Ping Gao, Jun Cheng, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
Author contributions: Li M performed the majority of experiments and analyzed the data; Wang Q, Liu SA and Zhang JQ provided vital reagents and analytical tools; Wang Q and Cheng J designed the research; Ju W, Dong JL and Gao P performed some of the molecular experiments; Quan M analyzed the data; Li M wrote the manuscript; and Feng SH revised the manuscript.
Supported by Medical Specialty Development Projects of Beijing Municipal Administration of Hospitals, No. ZYLX201402; Ministry of Education of The People’s Republic of China, No. 20121107110012; Beijing Municipal Commission of Education, No. 11320016; and Collaborative Innovation Center of Infectious Diseases and Beijing Key Laboratory of Emerging Infectious Diseases, Beijing, China.
Ethics approval: This study did not involve any animal experiments or human specimens, and thus was exempted from ethical review according to the Beijing Ditan Hospital Affiliated to the Capital University of Medical Sciences, Human Research Management Stipulation.
Institutional animal care and use committee: Not applicable.
Conflict-of-interest: The authors declare that there are no conflicts of interest in this study.
Data sharing: Technical appendix, statistical code, and dataset available from the corresponding author at jun.cheng.ditan@gmail.com. No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Jun Cheng, MD, PhD, EMBA, Professor, Beijing Ditan Hospital, Teaching Hospital of Peking University, 8 East Jingshun St., Beijing 100015, China. jun.cheng.ditan@gmail.com
Telephone: +86-10-84322006 Fax: +86-10-84397196
Received: November 26, 2014
Peer-review started: November 27, 2014
First decision: December 11, 2014
Revised: December 29, 2014
Accepted: February 5, 2015
Article in press: February 5, 2015
Published online: April 21, 2015
Abstract

AIM: To investigate the molecular mechanism for regulation of cholesterol metabolism by hepatitis C virus (HCV) core protein in HepG2 cells.

METHODS: HCV genotype 1b core protein was cloned and expressed in HepG2 cells. The cholesterol content was determined after transfection. The expression of sterol regulatory element binding protein 2 (SREBP2) and the rate-limiting enzyme in cholesterol synthesis (HMGCR) was measured by quantitative real-time PCR and immunoblotting after transfection. The effects of core protein on the SREBP2 promoter and 3’-untranslated region were analyzed by luciferase assay. We used different target predictive algorithms, microRNA (miRNA) mimics/inhibitors, and site-directed mutation to identify a putative target of a particular miRNA.

RESULTS: HCV core protein expression in HepG2 cells increased the total intracellular cholesterol level (4.05 ± 0.17 vs 6.47 ± 0.68, P = 0.001), and this increase corresponded to an increase in SREBP2 and HMGCR mRNA levels (P = 0.009 and 0.037, respectively) and protein expression. The molecular mechanism study revealed that the HCV core protein increased the expression of SREBP2 by enhancing its promoter activity (P = 0.004). In addition, miR-185-5p expression was tightly regulated by the HCV core protein (P = 0.041). Moreover, overexpression of miR-185-5p repressed the SREBP2 mRNA level (P = 0.022) and protein expression. In contrast, inhibition of miR-185-5p caused upregulation of SREBP2 protein expression. miR-185-5p was involved in the regulation of SREBP2 expression by HCV core protein.

CONCLUSION: HCV core protein disturbs the cholesterol homeostasis in HepG2 cells via the SREBP2 pathway; miR-185-5p is involved in the regulation of SREBP2 by the core protein.

Keywords: Cholesterol, Hepatitis C virus core protein, miR-185-5p, Steatosis, Sterol response element binding proteins

Core tip: In this study, we investigated the regulation relationship between hepatitis C virus (HCV) core protein and sterol regulatory element binding protein 2 (SREBP2). The microRNA miR-185-5p was confirmed in the regulation of SERBP2 expression, and it was the target for HCV core protein. The regulation relationship between HCV core, miR-185-5p and SREBP2 was established at transcriptional, post-transcriptional, and translational levels.