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INVOLVEMENT OF AKT IN THE UP-REGULATION OF FATTY ACID SYNTHASE PROMOTER BY HCV-3A CORE PROTEIN
C Jackel-Cram, L Babiuk, Q Liu
Vaccine & Infectious Disease Organization, University of Saskatchewan, Saskatoon
BACKGROUND: Hepatitis C virus genotype-3a (HCV-3a) is directly linked to the development of steatosis, or fatty liver. Previously, we studied the effects of HCV-3a core protein on the promoter activity of fatty acid synthase (FAS), a major enzyme involved in de novo lipid synthesis. We determined that the HCV-3a core protein up-regulated the FAS promoter almost 2-fold higher than HCV-1b core protein. The signal transduction pathways responsible for FAS up-regulation by HCV-3a core protein are not understood.
Purpose: To further investigate the role of the HCV-3a core protein in altering FAS promoter activity by examining its effect on Akt, an important cell signaling protein.
METHOD: Chinese Hamster Ovary (CHO) cells were transiently transfected with HCV-1b or -3a core proteins and a luciferase reporter plasmid containing the FAS promoter. A plasmid expressing a dominant negative form of Akt was used in the transfection to inhibit intracellular Akt activity. Alternatively, cells were treated with LY294002, an inhibitor of PI3K and Akt, for 6 hours prior to harvesting. Harvested cells were lysed and measured for luciferase activity from the FAS promoter.
RESULTS: Both the dominant negative Akt and the PI3K/Akt inhibitor LY294002 were able to prevent up-regulation of FAS transcription by HCV-3a core protein. Up-regulation of FAS by HCV-1b core and control levels of FAS transcription were not affected.
CONCLUSIONS: Akt is a critical protein kinase involved in many cellular pathways including cell survival and insulin signaling. These results indicate a possible role for HCV-3a core protein in regulating Akt activity and downstream pathways, especially those involved in regulation of lipogenic gene expression.
Funded by the National Canadian Research Training Program in Hepatitis C