Dataset Information

Domain 2 of Hepatitis C Virus Protein NS5A Activates Glucokinase and Induces Lipogenesis in Hepatocytes.

ABSTRACT: Hepatitis C virus (HCV) relies on cellular lipid metabolism for its replication, and actively modulates lipogenesis and lipid trafficking in infected hepatocytes. This translates into an intracellular accumulation of triglycerides leading to liver steatosis, cirrhosis and hepatocellular carcinoma, which are hallmarks of HCV pathogenesis. While the interaction of HCV with hepatocyte metabolic pathways is patent, how viral proteins are able to redirect central carbon metabolism towards lipogenesis is unclear. Here, we report that the HCV protein NS5A activates the glucokinase (GCK) isoenzyme of hexokinases through its D2 domain (NS5A-D2). GCK is the first rate-limiting enzyme of glycolysis in normal hepatocytes whose expression is replaced by the hexokinase 2 (HK2) isoenzyme in hepatocellular carcinoma cell lines. We took advantage of a unique cellular model specifically engineered to re-express GCK instead of HK2 in the Huh7 cell line to evaluate the consequences of NS5A-D2 expression on central carbon and lipid metabolism. NS5A-D2 increased glucose consumption but decreased glycogen storage. This was accompanied by an altered mitochondrial respiration, an accumulation of intracellular triglycerides and an increased production of very-low density lipoproteins. Altogether, our results show that NS5A-D2 can reprogram central carbon metabolism towards a more energetic and glycolytic phenotype compatible with HCV needs for replication.

SUBMITTER: Perrin-Cocon L

PROVIDER: S-EPMC8780509 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Domain 2 of Hepatitis C Virus Protein NS5A Activates Glucokinase and Induces Lipogenesis in Hepatocytes.

Perrin-Cocon Laure L Kundlacz Cindy C Jacquemin Clémence C Hanoulle Xavier X Aublin-Gex Anne A Figl Marianne M Manteca Jeremy J André Patrice P Vidalain Pierre-Olivier PO Lotteau Vincent V Diaz Olivier O

International journal of molecular sciences 20220114 2

Hepatitis C virus (HCV) relies on cellular lipid metabolism for its replication, and actively modulates lipogenesis and lipid trafficking in infected hepatocytes. This translates into an intracellular accumulation of triglycerides leading to liver steatosis, cirrhosis and hepatocellular carcinoma, which are hallmarks of HCV pathogenesis. While the interaction of HCV with hepatocyte metabolic pathways is patent, how viral proteins are able to redirect central carbon metabolism towards lipogenesis ...[more]

PMID: 35055105

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Project description:The propagation of the hepatitis C virus (HCV) is regulated in part by the phosphorylation of its nonstructural protein NS5A that undergoes sequential phosphorylation on several highly conserved serine residues and switches from a hypo- to a hyperphosphorylated state. Previous studies have shown that NS5A sequential phosphorylation requires NS3 encoded on the same NS3-NS4A-NS4B-NS5A polyprotein. Subtle mutations in NS3 without affecting its protease activity could affect NS5A phosphorylation. Given the ATPase domain in the NS3 COOH terminus, we tested whether NS3 participates in NS5A phosphorylation similarly to the nucleoside diphosphate kinase-like activity of the rotavirus NSP2 nucleoside triphosphatase (NTPase). Mutations in the NS3 ATP-binding motifs blunted NS5A hyperphosphorylation and phosphorylation at serines 225, 232, and 235, whereas a mutation in the RNA-binding domain did not. The phosphorylation events were not rescued with wild-type NS3 provided in trans. When provided with an NS3 ATPase-compatible ATP analog, N6-benzyl-ATP-γ-S, thiophosphorylated NS5A was detected in the cells expressing the wild-type NS3-NS5B polyprotein. The thiophosphorylation level was lower in the cells expressing NS3-NS5B with a mutation in the NS3 ATP-binding domain. In vitro assays with a synthetic peptide and purified wild-type NS3 followed by dot blotting and mass spectrometry found weak NS5A phosphorylation at serines 222 and 225 that was sensitive to an inhibitor of casein kinase Iα but not helicase. When casein kinase Iα was included in the assay, much stronger phosphorylation was observed at serines 225, 232, and 235. We concluded that NS5A sequential phosphorylation requires the ATP-binding domain of the NS3 helicase and that casein kinase Iα is a potent NS5A kinase. IMPORTANCE For more than 20 years, NS3 was known to participate in NS5A sequential phosphorylation. In the present study, we show for the first time that the ATP-binding domain of NS3 is involved in NS5A phosphorylation. In vitro assays showed that casein kinase Iα is a very potent kinase responsible for NS5A phosphorylation at serines 225, 232, and 235. Our data suggest that ATP binding by NS3 probably results in conformational changes that recruit casein kinase Iα to phosphorylate NS5A, initially at S225 and subsequently at S232 and S235. Our discovery reveals intricate requirements of the structural integrity of NS3 for NS5A hyperphosphorylation and HCV replication.

Project description:Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is a phosphoprotein that plays key, yet poorly defined, roles in both virus genome replication and virion assembly/release. It has been proposed that differential phosphorylation could act as a switch to regulate the various functions of NS5A; however, the mechanistic details of the role of this posttranslational modification in the virus life cycle remain obscure. We previously reported (D. Ross-Thriepland, J. Mankouri, and M. Harris, J Virol 89:3123-3135, 2015, doi:10.1128/JVI.02995-14) a role for phosphorylation at serine 225 (S225) of NS5A in the regulation of JFH-1 (genotype 2a) genome replication. A phosphoablatant (S225A) mutation resulted in a 10-fold reduction in replication and a perinuclear restricted distribution of NS5A, whereas the corresponding phosphomimetic mutation (S225D) had no phenotype. To determine the molecular mechanisms underpinning this phenotype we conducted a label-free proteomics approach to identify cellular NS5A interaction partners. This analysis revealed that the S225A mutation disrupted the interactions of NS5A with a number of cellular proteins, in particular the nucleosome assembly protein 1-like protein 1 (NAP1L1), bridging integrator 1 (Bin1, also known as amphiphysin II), and vesicle-associated membrane protein-associated protein A (VAP-A). These interactions were validated by immunoprecipitation/Western blotting, immunofluorescence, and proximity ligation assay. Importantly, small interfering RNA (siRNA)-mediated knockdown of NAP1L1, Bin1 or VAP-A impaired viral genome replication and recapitulated the perinuclear redistribution of NS5A seen in the S225A mutant. These results demonstrate that S225 phosphorylation regulates the interactions of NS5A with a defined subset of cellular proteins. Furthermore, these interactions regulate both HCV genome replication and the subcellular localization of replication complexes.IMPORTANCE Hepatitis C virus is an important human pathogen. The viral nonstructural 5A protein (NS5A) is the target for new antiviral drugs. NS5A has multiple functions during the virus life cycle, but the biochemical details of these roles remain obscure. NS5A is known to be phosphorylated by cellular protein kinases, and in this study, we set out to determine whether this modification is required for the binding of NS5A to other cellular proteins. We identified 3 such proteins and show that they interacted only with NS5A that was phosphorylated on a specific residue. Furthermore, these proteins were required for efficient virus replication and the ability of NS5A to spread throughout the cytoplasm of the cell. Our results help to define the function of NS5A and may contribute to an understanding of the mode of action of the highly potent antiviral drugs that are targeted to NS5A.

Dataset Information

Domain 2 of Hepatitis C Virus Protein NS5A Activates Glucokinase and Induces Lipogenesis in Hepatocytes.

Publications

Domain 2 of Hepatitis C Virus Protein NS5A Activates Glucokinase and Induces Lipogenesis in Hepatocytes.

Similar Datasets

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