Hepatitis B Virus-induced hFGL2 Transcription Is Dependent on c-Ets-2 and MAPK Signal Pathway

Meifang Han,Weiming Yan,Wei Guo,Dong Xi,Yaoyong Zhou,Weina Li,Sui Gao,Mingfeng Liu,Gary Levy,Xiaoping Luo,Qin Ning

doi:10.1074/jbc.m806769200

Abstract

Fibrinogen-like protein 2 (FGL2)/fibroleukin plays a pivotal role in the pathogenesis of experimental and human fulminant and chronic viral hepatitis. To define the transcription factor(s) and upstream signal transduction pathways involved in the transcription of human FGL2 (hFGL2) in response to hepatitis B (HB) virus, hepatitis B core (HBc), hepatitis B virus S protein (HBs), or hepatitis B virus X protein (HBx) protein, expression plasmids were cotransfected with an hFGL2 promoter luciferase reporter construct into Chinese hamster ovary and HepG2 cells, respectively. HBc and HBx proteins, but not HBs protein, enhanced hFGL2 transcription in both cell lines. A strong regulatory region from -712 to -568 (relative to the transcriptional starting site) was shown to be responsible for hFGL2 gene transcription in response to both HBc and HBx proteins. c-Ets-2 was shown to be translocated to the nucleus in association with hFGL2 expression in response to both HBc and HBx proteins. Short hairpin RNA (shRNA) interference of c-Ets-2 expression inhibited hFGL2 gene transcription by 64.8 and 60.0% in response to HBc and HBx, respectively. c-Ets-2 protein was highly expressed in peripheral blood mononuclear cells from patients with severe chronic hepatitis B (CHB) in contrast to patients with mild CHB. Increased phosphorylation of ERK and JNK was detected in peripheral blood mononuclear cells from patients with severe CHB. ERK inhibitor PD098059 or ERK shRNA abolished the nuclear c-Ets-2 DNA binding activity and hFGL2 induction in response to HBc, whereas JNK inhibitor SP600125 or JNK shRNA abolished the nuclear c-Ets-2 DNA binding activity and hFGL2 induction in response to HBx. In conclusion, HBc and HBx proteins enhance transcription of hFGL2 through c-Ets-2 dependent on MAPK signal pathways.

Highlights

Fibrinogen-like protein 2 (FGL2)/fibroleukin, known as fgl2 prothrombinase, has been cloned and identified to belong to the fibrinogen protein superfamily
Previous work has demonstrated that mFGL2/human FGL2 (hFGL2) selective expression in the liver plays a pivotal role in the pathogenesis of both experimental and human fulminant viral hepatitis and severe chronic hepatitis B (CHB) (15–20), and genetic interference of Mouse Fgl2 (mFgl2) gene leads to significant increase of survival for mice with fulminant viral hepatitis (21). mFgl2 and hFGL2 gene expression is confined to macrophages, lymphocytes, and endothelial cells of
To determine the mechanism of hFGL2 expression in response to Hepatitis B virus (HBV) proteins, CHO and HepG2 cells were transfected with the hFGL2 promoter construct hfgl2p(Ϫ1334)LUC

Summary

Introduction

Fibrinogen-like protein 2 (FGL2)/fibroleukin, known as fgl prothrombinase, has been cloned and identified to belong to the fibrinogen protein superfamily. Previous work has demonstrated that mFGL2/hFGL2 selective expression in the liver plays a pivotal role in the pathogenesis of both experimental and human fulminant viral hepatitis and severe chronic hepatitis B (CHB) (15–20), and genetic interference of mFgl gene leads to significant increase of survival for mice with fulminant viral hepatitis (21). The expression of mFgl mRNA transcription and protein is induced by IFN-␥ in macrophages and TNF-␣ in endothelial cells, respectively (24). It has been reported that the nucleocapsid protein of mouse hepatitis virus 3 (MHV-3) induces transcription of mFgl and invokes hepatic nuclear factor 4␣ in mFgl gene expression (20, 25). We demonstrated increased c-Ets-2 expression and activity of ERK and JNK in PBMC in association with severe CHB viral infection

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Results

Conclusion