The hepatitis C virus NS2 protein is an inhibitor of CIDE-B-induced apoptosis.
Chronic hepatitis C virus (HCV) infection frequently leads to liver cancer. To determine the viral factor(s) potentially involved in viral persistence, we focused our work on NS2, a viral protein of unknown function. To assign a role for NS2, we searched for cellular proteins that interact with NS2. Performing a two-hybrid screen on a human liver cDNA library, we found that NS2 interacted with the liver-specific pro-apoptotic CIDE-B protein. Binding specificity of NS2 for CIDE-B was confirmed by cell-free assays associated with colocalization studies and coprecipitation experiments on human endogenous CIDE-B. CIDE-B, a member of the novel CIDE family of apoptosis-inducing factors, has been reported to show strong cell death-inducing activity in its C-terminal domain. We show that this CIDE-B killing domain is involved in the NS2 interaction. NS2 binding was sufficient to inhibit CIDE-B-induced apoptosis because an NS2 deletion mutant unable to interact with CIDE-B in vitro lost its capacity to interfere with CIDE-B cell death activity. Although it has been reported that CIDE-B-induced apoptosis is characterized by mitochondrial localization, the precise apoptotic mechanism remained unknown. Here, we show that CIDE-B induced cell death in a caspase-dependent manner through cytochrome c release from mitochondria. Furthermore, we found that NS2 counteracted the cytochrome c release induced by CIDE-B. In vivo, the CIDE-B protein level was extremely low in adenovirus-infected transgenic mice expressing the HCV polyprotein compared with that in wild-type mice. We suggest that NS2 interferes with the CIDE-B-induced death pathway and participates in HCV strategies to subvert host cell defense.
Erdtmann
Lars
L
INSERM U522, Hôpital de Pontchaillou, 35033 Rennes Cedex, France. lars.erdtmann@univ-rennes1.fr
Franck
Nathalie
N
Lerat
Hervé
H
Le Seyec
Jacques
J
Gilot
David
D
Cannie
Isabelle
I
Gripon
Philippe
P
Hibner
Urszula
U
Guguen-Guillouzo
Christiane
C
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D019556:COS Cells; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D016296:Mutagenesis; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D020798:Two-Hybrid System Techniques; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C112511:CIDEB protein, human; D003574:Cytochrome c Group; D008164:Luminescent Proteins; C097010:NS2 protein, Hepatitis C virus; D011506:Proteins; D011994:Recombinant Proteins; D017361:Viral Nonstructural Proteins; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase; D001616:beta-Galactosidase; D020169:Caspases