TY  - JOUR
A1  - Dultz, Georg
A1  - Srikakulam, Sanjay K.
A1  - Konetschnik, Michael
A1  - Shimakami, Tetsuro
A1  - Doncheva, Nadezhda T.
A1  - Dietz, Julia
A1  - Sarrazin, Christoph
A1  - Biondi, Ricardo M.
A1  - Zeuzem, Stefan
A1  - Tampé, Robert
A1  - Kalinina, Olga V.
A1  - Welsch, Christoph
T1  - Epistatic interactions promote persistence of NS3-Q80K in HCV infection by compensating for protein folding instability
T2  - Journal of biological chemistry
N2  - The Q80K polymorphism in the NS3-4A protease of the hepatitis C virus is associated with treatment failure of direct-acting antiviral agents. This polymorphism is highly prevalent in genotype 1a infections and stably transmitted between hosts. Here, we investigated the underlying molecular mechanisms of evolutionarily conserved coevolving amino acids in NS3-Q80K and revealed potential implications of epistatic interactions in immune escape and variants persistence. Using purified protein, we characterized the impact of epistatic amino acid substitutions on the physicochemical properties and peptide cleavage kinetics of the NS3-Q80K protease. We found that Q80K destabilized the protease protein fold (p < 0.0001). Although NS3-Q80K showed reduced peptide substrate turnover (p < 0.0002), replicative fitness in an H77S.3 cell culture model of infection was not significantly inferior to the WT virus. Epistatic substitutions at residues 91 and 174 in NS3-Q80K stabilized the protein fold (p < 0.0001) and leveraged the WT protease stability. However, changes in protease stability inversely correlated with enzymatic activity. In infectious cell culture, these secondary substitutions were not associated with a gain of replicative fitness in NS3-Q80K variants. Using molecular dynamics, we observed that the total number of residue contacts in NS3-Q80K mutants correlated with protein folding stability. Changes in the number of contacts reflected the compensatory effect on protein folding instability by epistatic substitutions. In summary, epistatic substitutions in NS3-Q80K contribute to viral fitness by mechanisms not directly related to RNA replication. By compensating for protein-folding instability, epistatic interactions likely protect NS3-Q80K variants from immune cell recognition.
KW  - hepatitis C virus
KW  - serine protease (NS3-4A)
KW  - protein folding
KW  - protein evolution
KW  - viral fitness
KW  - immune escape
KW  - resistance mutation
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/77974
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-779744
SN  - 0021-9258
VL  - 297.2021
IS  - 3, art. 101031
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -