Glucose-regulated protein 78 is an intracellular antiviral factor against hepatitis B virus.
Hepatitis B virus (HBV) infection is a global public health problem that plays a crucial role in the pathogenesis of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. However, the pathogenesis of HBV infection and the mechanisms of host-virus interactions are still elusive. In this study, two-dimensional gel electrophoresis and mass spectrometry-based comparative proteomics were applied to analyze the host response to HBV using an inducible HBV-producing cell line, HepAD38. Twenty-three proteins were identified as differentially expressed with glucose-regulated protein 78 (GRP78) as one of the most significantly up-regulated proteins induced by HBV replication. This induction was further confirmed in both HepAD38 and HepG2 cells transfected with HBV-producing plasmids by real time RT-PCR and Western blotting as well as in HBV-infected human liver biopsies by immunohistochemistry. Knockdown of GRP78 expression by RNA interference resulted in a significant increase of both intracellular and extracellular HBV virions in the transient HBV-producing HepG2 cells concomitant with enhanced levels of hepatitis B surface antigen and e antigen in the culture medium. Conversely overexpression of GRP78 in HepG2 cells led to HBV suppression concomitant with induction of the positive regulatory circuit of GRP78 and interferon-beta1 (IFN-beta1). In this connection, the IFN-beta1-mediated 2',5'-oligoadenylate synthetase and RNase L signaling pathway was noted to be activated in GRP78-overexpressing HepG2 cells. Moreover GRP78 was significantly down-regulated in the livers of chronic hepatitis B patients after effective anti-HBV treatment (p = 0.019) as compared with their counterpart pretreatment liver biopsies. In conclusion, the present study demonstrates for the first time that GRP78 functions as an endogenous anti-HBV factor via the IFN-beta1-2',5'-oligoadenylate synthetase-RNase L pathway in hepatocytes. Induction of hepatic GRP78 may provide a novel therapeutic approach in treating HBV infection.
Ma
Yan
Y
Stanley Ho Center for Emerging Infectious Diseases, School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China.
Yu
Jun
J
Chan
Henry L Y
HL
Chen
Yang-chao
YC
Wang
Hua
H
Chen
Ying
Y
Chan
Chu-yan
CY
Go
Minnie Y Y
MY
Tsai
Sau-na
SN
Ngai
Sai-ming
SM
To
Ka-fai
KF
Tong
Joanna H M
JH
He
Qing-Yu
QY
Sung
Joseph J Y
JJ
Kung
Hsiang-fu
HF
Cheng
Christopher H K
CH
He
Ming-liang
ML
D000998:Antiviral Agents / Q000737:chemistry*; D001706:Biopsy; D015153:Blotting, Western; D002460:Cell Line; D003470:Culture Media; D015180:Electrophoresis, Gel, Two-Dimensional; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006509:Hepatitis B / Q000378:metabolism / Q000821:virology; D006515:Hepatitis B virus / Q000378:metabolism*; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D016899:Interferon-beta / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000998:Antiviral Agents; D003470:Culture Media; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D016899:Interferon-beta