The NS3 protein of hepatitis C virus induces caspase-8-mediated apoptosis independent of its protease or helicase activities.
Apoptosis has been implicated in the pathogenesis of hepatitis C virus (HCV)-related disease. Here, we show that expression of HCV NS3, or the NS2/NS3 precursor protein, in mammalian cells results in induction of apoptosis and activation of caspases. HCV NS3-induced apoptosis was blocked by a caspase-8, but not a caspase-9-specific inhibitor. HCV NS3 coimmunoprecipitated with caspase-8, but not with other caspases or with FADD. Coexpression of HCV NS3 and caspase-8 resulted in aggregation of the caspase in punctate structures that colocalized with HCV NS3. Cell lines stably expressing low levels HCV NS3 showed increased sensitivity to Fas-induced cell death. Point mutations of NS3 showed that the pro-apoptotic function of the protein is distinct from its protease and helicase activities. These findings suggest that HCV NS3 promotes caspase-8 induced apoptosis at a pathway site distal to FADD, and that flavivirus NS3 may represent a new class of pro-apoptotic proteins.
Medical Virology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA.
Elena A
EA
Prikhod'ko
Grigori G
GG
Prikhod'ko
Richard M
RM
Siegel
Peter
P
Thompson
Marian E
ME
Major
Jeffrey I
JI
Cohen
D000818:Animals; D017209:Apoptosis; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002522:Chlorocebus aethiops; D004265:DNA Helicases / Q000378:metabolism; D004789:Enzyme Activation; D016174:Hepacivirus / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism; D020365:RNA Helicases / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D053181:Caspase 8; D020169:Caspases; D004265:DNA Helicases; D010447:Peptide Hydrolases; D020365:RNA Helicases; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C505530:CASP8 protein, human