A wide range of NS3/4A protease catalytic efficiencies in HCV-infected individuals.
The hepatitis C virus (HCV) NS3/4A protease acts as an antagonist of virus-induced interferon (IFN) regulatory factor (IRF)-3 activation and IFN-beta expression. The NS3/4A protease performs this function by cleaving Cardif and TRIF proteins to block retinoic-acid-inducible gen I (RIG-I) and toll-like receptor (TLR)-3 signaling, respectively. NS3/4A protease inhibition can prevent Cardif and/or TRIF inactivation during HCV infection, thereby maintaining the innate immune response. Thus, differences in NS3/4A protease catalytic efficiency could be related to viral pathogenicity. In this study, we analyzed the catalytic efficiency of the most abundant NS3/4A protease isolated from each of 12 individuals infected with HCV genotypes 1b, 1a, 3a, 4a or 4d. A diversity of NS3/4A protease catalytic efficiencies (up to a six-fold difference) was found in the analyzed samples. The genotype 1b NS3/4A proteases displayed the highest catalytic efficiencies. However, within this genotype up to three-fold differences were observed. Cross-genotypic interactions between the NS3 protease domain and the NS4A cofactor peptide were also investigated. Overall, catalytic efficiencies of NS3 proteases cross-interacting with NS4A cofactors from heterologous genotypes were as efficient as the homologous NS3/4A interactions. Of the 28 heterologous interactions tested, only 6 resulted in deleterious or nonfunctional enzymes. Nonfunctional interactions were not genotype-specific, suggesting that enhancement of NS3 catalytic efficiency by the NS4A cofactor depends on a few specific amino acid residues. Characterization of the proteolytic activities of individual NS3/4A proteases should provide clues for understanding HCV-host interactions, as well as assisting in the development of new classes of NS3/4A protease inhibitors.
Franco
Sandra
S
Fundacio irsiCaixa, Universitat Autònoma de Barcelona (UAB), Spain.
Clotet
Bonaventura
B
Martínez
Miguel Angel
MA
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D014644:Genetic Variation; D016174:Hepacivirus / Q000502:physiology*; D006526:Hepatitis C / Q000821:virology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C455041:NS4A cofactor peptide, Hepatitis C virus