Hepatitis C virus nonstructural protein 5A inhibits tumor necrosis factor-alpha-mediated apoptosis in Huh7 cells.
To analyze the influence of hepatitis C virus nonstructural protein 5A (NS5A) on apoptosis, we established Huh7 cells that stably express NS5A, and induced apoptosis using tumor necrosis factor (TNF)-alpha. The viability of control Huh7 cells was reduced to 40%, compared with untreated cells, after TNF-alpha treatment, whereas that of Huh7-NS5A cells was reduced only to 80%. DNA fragmentation also decreased to <50% in Huh7-NS5A compared with control cells. Nuclear factor-kappaB activation was the same in both cell types, whereas caspase-8, -9, and -3 activity was decreased in Huh7-NS5A cells, compared with control cells, which indicates that the inhibition of caspase-8 activation is responsible for the antiapoptotic effect of the NS5A protein. The coexpression of NS5A did not inhibit apoptosis induced by caspase-8 or Fas-associating death domain protein expression. These findings suggest that the NS5A protein inhibits the apoptotic effect of TNF-alpha upstream of caspase-8 in the apoptosis cascade.
Miyasaka
Yuka
Y
Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
Enomoto
Nobuyuki
N
Kurosaki
Masayuki
M
Sakamoto
Naoya
N
Kanazawa
Nobuhiko
N
Kohashi
Takahiro
T
Ueda
Eri
E
Maekawa
Shinya
S
Watanabe
Hideki
H
Izumi
Namiki
N
Sato
Chifumi
C
Watanabe
Mamoru
M
D017209:Apoptosis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000502:physiology; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D044943:Fatty Acid Desaturases / Q000502:physiology; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism; D006526:Hepatitis C / Q000473:pathology; D022781:Hepatocytes / Q000166:cytology; D006801:Humans; D016328:NF-kappa B / Q000502:physiology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D020320:Oligoribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction / Q000276:immunology*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000502:physiology*; D012324:RNA-Dependent RNA Polymerase
D029681:Arabidopsis Proteins; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003609:Dactinomycin; D044943:Fatty Acid Desaturases; D016328:NF-kappa B; D019384:Nucleic Acid Synthesis Inhibitors; D020320:Oligoribonucleotides, Antisense; D014409:Tumor Necrosis Factor-alpha; D017361:Viral Nonstructural Proteins; C084083:Fad7 protein, Arabidopsis; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase; C505530:CASP8 protein, human; C506433:CASP9 protein, human