Mitogen-activated protein kinase signalling pathways triggered by the hepatitis C virus envelope protein E2: implications for the prevention of infection.
OBJECTIVE
Hepatitis C virus (HCV) is a major pathogenic factor of liver diseases. During HCV infection, interaction of the envelope protein E2 of the virion, with target cells, is a crucial process for viral penetration into the cell and its propagation. We speculate that such interaction may trigger early signalling events required for HCV infection.


METHODS
Human liver cell line L-02 was treated with HCV E2. The kinase phosphorylation levels of mitogen-activated protein kinase (MAPK) signalling pathways in the treated cells were analyzed by Western blotting. The proliferation of the E2-treated cells was evaluated by MTT assay.


RESULTS
HCV E2 was shown to be an efficient activator for MAPK pathways. Levels of phosphorylation of upstream kinases Raf-1 and MEK1/2 were seen to be elevated following E2 treatment and similarly, phosphorylation levels of downstream kinases MAPK/ERK and p38 MAPK also increased in response to E2 treatment, and specificity of kinase activation by E2 was confirmed. E2-induced MAPK/ERK activation was inhibited by the MEK1/2 inhibitor U0126 in a concentration-dependent manner. Blockage of relevant cellular receptors reduced activation of Raf-1, MEK1/2, MAPK/ERK and p38 MAPK by E2, indicating efflux of the E2 signal from extracellular to the intracellular spaces. Thus, kinase cascades of MAPK pathways were continuously affected by E2 presence. Moreover, enhancement of cell proliferation by E2 appeared to be associated with the dynamic phosphorylation of MAPK/ERK and p38 MAPK.


CONCLUSIONS
These results suggest that MAPK signalling pathways triggered by E2 may be a potential target for prevention of HCV infection.
Zhao
L-J
LJ
Department of Microbiology, State Key Laboratory of Medical Immunology, Second Military Medical University, Shanghai, China.
Zhao
P
P
Chen
Q-L
QL
Ren
H
H
Pan
W
W
Qi
Z-T
ZT
D015703:Antigens, CD / Q000378:metabolism; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006526:Hepatitis C / Q000517:prevention & control; D006801:Humans; D008099:Liver / Q000201:enzymology / Q000378:metabolism / Q000821:virology*; D020935:MAP Kinase Signaling System; D009570:Nitriles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011973:Receptors, LDL / Q000378:metabolism; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D015703:Antigens, CD; D002070:Butadienes; C554798:CD81 protein, human; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D011973:Receptors, LDL; D060225:Tetraspanin 28; C113580:U 0126; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases