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.

Hexokinases in cancer and other pathologies

“…In general, hexokinase expression or activity is upregulated in cells and tissues undergoing immune responses, such as lipopolysaccharide (LPS)-stimulated macrophages ( Tan et al., 2015 ), osteoarthritis synovial tissue ( Bao et al., 2022 ), and hepatitis C virus-infected liver cells ( Perrin-Cocon et al., 2022 ). This upregulation contributes to glycolysis enhancement, thus supporting the cells with energy and metabolic intermediates for activities related to immune responses, including cytokine production, endocytosis, and antigen presentation.…”

Rôle du métabolisme cellulaire dans le contrôle des hépatites virales chroniques

“…En parallèle, la glycolyse est activée, ce qui permet de maintenir les niveaux intracellulaires d'ATP, mais aussi d'alimenter l'ensemble des voies anaboliques nécessaires à la réplication virale. Le VHC active également la glucokinase (GCK) et induit l'activité de la pyruvate déshydrogénase kinase (PDK), deux enzymes limitantes, à l'entrée et en aval de la glycolyse [5,6]. Le virus est également capable d'induire l'expression d'enzymes de la gluconéogenèse, comme la phosphoénolpyruvate carboxykinase, ou de moduler la signalisation du récepteur de l'insuline, induisant ainsi une résistance de l'hépatocyte à cette hormone [7,8].…”

What role for cellular metabolism in the control of hepatitis viruses?

“…The downregulation of cell surface expression of GLUT2 is also observed during infection ( 92 ). Meanwhile, we recently described that the HCV protein NS5A enhances glycolysis through a direct interaction with hexokinases, thereby altering the catalytic parameters of these enzymes ( 93 , 94 ). Interestingly this enhancement of the glycolytic flux induced by NS5A does not result in the accumulation of glycogen suggesting a more complex rewiring of intracellular intermediate metabolites than expected in hepatocytes facing an increased glycolysis.…”