Langat flavivirus protease NS3 binds caspase-8 and induces apoptosis.
The flavivirus NS3 protein plays an important role in the cleavage and processing of the viral polyprotein and in the synthesis of the viral RNA. NS3 recruits NS2B and NS5 proteins to form complexes possessing protease and replicase activities through protease and nucleoside triphosphatase/helicase domains. We have found that NS3 also induces apoptosis. Expression of the Langat (LGT) virus NS3 protein resulted in a cleavage of cellular DNA and reduced the viability of cells. Coexpression of NS3 with apoptotic inhibitors (CrmA and P35) and addition of caspase peptide substrates (Z-VAD-FMK and Z-IETD-FMK) to NS3-transfected cells blocked NS3-induced apoptosis. In cotransfection experiments, NS3 bound to caspase-8 and enhanced caspase-8-mediated apoptosis. NS3 and caspase-8 colocalized in the cytoplasm of transfected cells. Deletion analysis demonstrated that at least two regions of NS3 contribute to its apoptotic activities. The protease and helicase domains are each able to bind to caspase-8, while the protease domain alone induces apoptosis. The protease domain and tetrahelix region of the helicase domain are required for NS3 to augment caspase-8-mediated apoptosis. Thus, the LGT virus NS3 protein is a multifunctional protein that binds to caspase-8 and induces apoptosis.
Prikhod'ko
Grigori G
GG
Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. PrikhodkoG@usa.redcross.org
Prikhod'ko
Elena A
EA
Pletnev
Alexander G
AG
Cohen
Jeffrey I
JI
D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D004669:Encephalitis Viruses, Tick-Borne / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D051379:Mice; D020365:RNA Helicases; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases; D014407:Tumor Cells, Cultured; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D020365:RNA Helicases; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C060028:NS3 protein, flavivirus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse