1887

Abstract

Hepatitis C virus genotype-3a (HCV-3a) is directly linked to the development of steatosis. We previously showed that, through sterol regulatory element binding protein-1 (SREBP-1), HCV-3a core protein upregulates the promoter activity of fatty acid synthase, a major enzyme involved in lipid synthesis. In this study, we investigated whether HCV-3a core can activate SREBP-1 and studied the role of phosphoinositide 3-kinase (PI3K)–Akt-2 pathway in modulating SREBP-1 activity by HCV-3a core. To determine whether HCV-3a core could activate SREBP-1, the level of mature SREBP-1 was analysed by Western blotting. Our results showed that the level of mature SREBP-1 was enhanced by HCV-3a core protein after transient expression and in the chimeric HCV-3a core/1b replicon cells in comparison to controls. To investigate the role of the PI3K–Akt-2 pathway in SREBP-1 activation by HCV-3a core, PI3K and Akt-2 activity was inhibited by using the chemical inhibitor LY294002, a dominant-negative Akt-2 plasmid, or knockdown of Akt-2 by small hairpin RNA. Our results showed that inhibition of PI3K and Akt-2 was associated with reduced SREBP-1 activation by HCV-3a core. These results indicate a role for PI3K and Akt-2 in increasing SREBP-1 activity by HCV-3a core protein and provide a mechanism of steatosis caused by HCV.

Loading

Article metrics loading...

/content/journal/jgv/10.1099/vir.0.017418-0
2010-06-01
2024-12-09
Loading full text...

Full text loading...

/deliver/fulltext/jgv/91/6/1388.html?itemId=/content/journal/jgv/10.1099/vir.0.017418-0&mimeType=html&fmt=ahah

References

  1. Abid, K., Pazienza, V., de Gottardi, A., Rubbia-Brandt, L., Conne, B., Pugnale, P., Rossi, C., Mangia, A. & Negro, F.(2005). An in vitro model of hepatitis C virus genotype 3a-associated triglycerides accumulation. J Hepatol 42, 744–751.[CrossRef] [Google Scholar]
  2. Amemiya-Kudo, M., Shimano, H., Hasty, A. H., Yahagi, N., Yoshikawa, T., Matsuzaka, T., Okazaki, H., Tamura, Y., Iizuka, Y. & other authors(2002). Transcriptional activities of nuclear SREBP-1a, -1c, and -2 to different target promoters of lipogenic and cholesterogenic genes. J Lipid Res 43, 1220–1235. [Google Scholar]
  3. Amoroso, P., Rapicetta, M., Tosti, M. E., Mele, A., Spada, E., Buonocore, S., Lettieri, G., Pierri, P., Chionne, P. & other authors(1998). Correlation between virus genotype and chronicity rate in acute hepatitis C. J Hepatol 28, 939–944.[CrossRef] [Google Scholar]
  4. Bengoechea-Alonso, M. T. & Ericsson, J.(2007). SREBP in signal transduction: cholesterol metabolism and beyond. Curr Opin Cell Biol 19, 215–222.[CrossRef] [Google Scholar]
  5. Bengoechea-Alonso, M. T. & Ericsson, J.(2009). A phosphorylation cascade controls the degradation of active SREBP1. J Biol Chem 284, 5885–5895.[CrossRef] [Google Scholar]
  6. Brazil, D. P., Yang, Z. Z. & Hemmings, B. A.(2004). Advances in protein kinase B signalling: AKTion on multiple fronts. Trends Biochem Sci 29, 233–242.[CrossRef] [Google Scholar]
  7. Brown, M. S., Ye, J., Rawson, R. B. & Goldstein, J. L.(2000). Regulated intramembrane proteolysis: a control mechanism conserved from bacteria to humans. Cell 100, 391–398.[CrossRef] [Google Scholar]
  8. Brownlie, R., Zhu, J., Allan, B., Mutwiri, G. K., Babiuk, L. A., Potter, A. & Griebel, P.(2009). Chicken TLR21 acts as a functional homologue to mammalian TLR9 in the recognition of CpG oligodeoxynucleotides. Mol Immunol 46, 3163–3170.[CrossRef] [Google Scholar]
  9. Castera, L., Hezode, C., Roudot-Thoraval, F., Lonjon, I., Zafrani, E. S., Pawlotsky, J. M. & Dhumeaux, D.(2004). Effect of antiviral treatment on evolution of liver steatosis in patients with chronic hepatitis C: indirect evidence of a role of hepatitis C virus genotype 3 in steatosis. Gut 53, 420–424.[CrossRef] [Google Scholar]
  10. Cho, H., Mu, J., Kim, J. K., Thorvaldsen, J. L., Chu, Q., Crenshaw, E. B., III, Kaestner, K. H., Bartolomei, M. S., Shulman, G. I. & Birnbaum, M. J.(2001). Insulin resistance and a diabetes mellitus-like syndrome in mice lacking the protein kinase Akt2 (PKBβ). Science 292, 1728–1731.[CrossRef] [Google Scholar]
  11. Du, X., Kristiana, I., Wong, J. & Brown, A. J.(2006). Involvement of Akt in ER-to-Golgi transport of SCAP/SREBP: a link between a key cell proliferative pathway and membrane synthesis. Mol Biol Cell 17, 2735–2745.[CrossRef] [Google Scholar]
  12. Engelman, J. A.(2009). Targeting PI3K signalling in cancer: opportunities, challenges and limitations. Nat Rev Cancer 9, 550–562.[CrossRef] [Google Scholar]
  13. Engelman, J. A., Luo, J. & Cantley, L. C.(2006). The evolution of phosphatidylinositol 3-kinases as regulators of growth and metabolism. Nat Rev Genet 7, 606–619. [Google Scholar]
  14. Fang, G., Weiser, B., Visosky, A., Moran, T. & Burger, H.(1999). PCR-mediated recombination: a general method applied to construct chimeric infectious molecular clones of plasma-derived HIV-1 RNA. Nat Med 5, 239–242.[CrossRef] [Google Scholar]
  15. Gottwein, J. M., Scheel, T. K., Hoegh, A. M., Lademann, J. B., Eugen-Olsen, J., Lisby, G. & Bukh, J.(2007). Robust hepatitis C genotype 3a cell culture releasing adapted intergenotypic 3a/2a (S52/JFH1) viruses. Gastroenterology 133, 1614–1626.[CrossRef] [Google Scholar]
  16. Graham, F. L. & van der Eb, A. J.(1973). A new technique for the assay of infectivity of human adenovirus 5 DNA. Virology 52, 456–467.[CrossRef] [Google Scholar]
  17. Hawkins, J. L., Robbins, M. D., Warren, L. C., Xia, D., Petras, S. F., Valentine, J. J., Varghese, A. H., Wang, I. K., Subashi, T. A. & other authors(2008). Pharmacologic inhibition of site 1 protease activity inhibits sterol regulatory element-binding protein processing and reduces lipogenic enzyme gene expression and lipid synthesis in cultured cells and experimental animals. J Pharmacol Exp Ther 326, 801–808.[CrossRef] [Google Scholar]
  18. Horton, J. D., Goldstein, J. L. & Brown, M. S.(2002). SREBPs: activators of the complete program of cholesterol and fatty acid synthesis in the liver. J Clin Invest 109, 1125–1131.[CrossRef] [Google Scholar]
  19. Hourioux, C., Patient, R., Morin, A., Blanchard, E., Moreau, A., Trassard, S., Giraudeau, B. & Roingeard, P.(2007). The genotype 3-specific hepatitis C virus core protein residue phenylalanine 164 increases steatosis in an in vitro cellular model. Gut 56, 1302–1308.[CrossRef] [Google Scholar]
  20. Ikeda, M., Yi, M., Li, K. & Lemon, S. M.(2002). Selectable subgenomic and genome-length dicistronic RNAs derived from an infectious molecular clone of the HCV-N strain of hepatitis C virus replicate efficiently in cultured Huh7 cells. J Virol 76, 2997–3006.[CrossRef] [Google Scholar]
  21. Jackel-Cram, C., Babiuk, L. A. & Liu, Q.(2007). Up-regulation of fatty acid synthase promoter by hepatitis C virus core protein: genotype-3a core has a stronger effect than genotype-1b core. J Hepatol 46, 999–1008. [Google Scholar]
  22. Kotzka, J., Muller-Wieland, D., Koponen, A., Njamen, D., Kremer, L., Roth, G., Munck, M., Knebel, B. & Krone, W.(1998). ADD1/SREBP-1c mediates insulin-induced gene expression linked to the MAP kinase pathway. Biochem Biophys Res Commun 249, 375–379.[CrossRef] [Google Scholar]
  23. Kumar, D., Farrell, G. C., Fung, C. & George, J.(2002). Hepatitis C virus genotype 3 is cytopathic to hepatocytes: reversal of hepatic steatosis after sustained therapeutic response. Hepatology 36, 1266–1272.[CrossRef] [Google Scholar]
  24. Latasa, M. J., Moon, Y. S., Kim, K. H. & Sul, H. S.(2000). Nutritional regulation of the fatty acid synthase promoter in vivo: sterol regulatory element binding protein functions through an upstream region containing a sterol regulatory element. Proc Natl Acad Sci U S A 97, 10619–10624.[CrossRef] [Google Scholar]
  25. Lohmann, V., Hoffmann, S., Herian, U., Penin, F. & Bartenschlager, R.(2003). Viral and cellular determinants of hepatitis C virus RNA replication in cell culture. J Virol 77, 3007–3019.[CrossRef] [Google Scholar]
  26. Lu, M. & Shyy, J. Y.(2006). Sterol regulatory element-binding protein 1 is negatively modulated by PKA phosphorylation. Am J Physiol Cell Physiol 290, C1477–C1486.[CrossRef] [Google Scholar]
  27. Mannova, P. & Beretta, L.(2005). Activation of the N-Ras-PI3K-Akt-mTOR pathway by hepatitis C virus: control of cell survival and viral replication. J Virol 79, 8742–8749.[CrossRef] [Google Scholar]
  28. Negro, F.(2006). Mechanisms and significance of liver steatosis in hepatitis C virus infection. World J Gastroenterol 12, 6756–6765. [Google Scholar]
  29. Oem, J. K., Jackel-Cram, C., Li, Y. P., Zhou, Y., Zhong, J., Shimano, H., Babiuk, L. A. & Liu, Q.(2008). Activation of sterol regulatory element-binding protein 1c and fatty acid synthase transcription by hepatitis C virus non-structural protein 2. J Gen Virol 89, 1225–1230.[CrossRef] [Google Scholar]
  30. Park, C. Y., Jun, H. J., Wakita, T., Cheong, J. H. & Hwang, S. B.(2009). Hepatitis C virus nonstructural 4B protein modulates sterol regulatory element-binding protein signaling via the AKT pathway. J Biol Chem 284, 9237–9246.[CrossRef] [Google Scholar]
  31. Patton, H. M., Patel, K., Behling, C., Bylund, D., Blatt, L. M., Vallee, M., Heaton, S., Conrad, A., Pockros, P. J. & McHutchison, J. G.(2004). The impact of steatosis on disease progression and early and sustained treatment response in chronic hepatitis C patients. J Hepatol 40, 484–490. [Google Scholar]
  32. Pazienza, V., Clement, S., Pugnale, P., Conzelmann, S., Pascarella, S., Mangia, A. & Negro, F.(2009). Gene expression profile of Huh-7 cells expressing hepatitis C virus genotype 1b or 3a core proteins. Liver Int 29, 661–669.[CrossRef] [Google Scholar]
  33. Pietschmann, T., Lohmann, V., Kaul, A., Krieger, N., Rinck, G., Rutter, G., Strand, D. & Bartenschlager, R.(2002). Persistent and transient replication of full-length hepatitis C virus genomes in cell culture. J Virol 76, 4008–4021.[CrossRef] [Google Scholar]
  34. Pietschmann, T., Kaul, A., Koutsoudakis, G., Shavinskaya, A., Kallis, S., Steinmann, E., Abid, K., Negro, F., Dreux, M. & other authors(2006). Construction and characterization of infectious intragenotypic and intergenotypic hepatitis C virus chimeras. Proc Natl Acad Sci U S A 103, 7408–7413.[CrossRef] [Google Scholar]
  35. Piodi, A., Chouteau, P., Lerat, H., Hezode, C. & Pawlotsky, J. M.(2008). Morphological changes in intracellular lipid droplets induced by different hepatitis C virus genotype core sequences and relationship with steatosis. Hepatology 48, 16–27.[CrossRef] [Google Scholar]
  36. Porstmann, T., Griffiths, B., Chung, Y. L., Delpuech, O., Griffiths, J. R., Downward, J. & Schulze, A.(2005). PKB/Akt induces transcription of enzymes involved in cholesterol and fatty acid biosynthesis via activation of SREBP. Oncogene 24, 6465–6481. [Google Scholar]
  37. Poynard, T., Ratziu, V., McHutchison, J., Manns, M., Goodman, Z., Zeuzem, S., Younossi, Z. & Albrecht, J.(2003a). Effect of treatment with peginterferon or interferon alfa-2b and ribavirin on steatosis in patients infected with hepatitis C. Hepatology 38, 75–85. [Google Scholar]
  38. Poynard, T., Yuen, M. F., Ratziu, V. & Lai, C. L.(2003b). Viral hepatitis C. Lancet 362, 2095–2100.[CrossRef] [Google Scholar]
  39. Punga, T., Bengoechea-Alonso, M. T. & Ericsson, J.(2006). Phosphorylation and ubiquitination of the transcription factor sterol regulatory element-binding protein-1 in response to DNA binding. J Biol Chem 281, 25278–25286.[CrossRef] [Google Scholar]
  40. Raghow, R., Yellaturu, C., Deng, X., Park, E. A. & Elam, M. B.(2008). SREBPs: the crossroads of physiological and pathological lipid homeostasis. Trends Endocrinol Metab 19, 65–73.[CrossRef] [Google Scholar]
  41. Roth, G., Kotzka, J., Kremer, L., Lehr, S., Lohaus, C., Meyer, H. E., Krone, W. & Muller-Wieland, D.(2000). MAP kinases Erk1/2 phosphorylate sterol regulatory element-binding protein (SREBP)-1a at serine 117 in vitro. J Biol Chem 275, 33302–33307.[CrossRef] [Google Scholar]
  42. Rubbia-Brandt, L., Quadri, R., Abid, K., Giostra, E., Male, P. J., Mentha, G., Spahr, L., Zarski, J. P., Borisch, B. & other authors(2000). Hepatocyte steatosis is a cytopathic effect of hepatitis C virus genotype 3. J Hepatol 33, 106–115.[CrossRef] [Google Scholar]
  43. Sheikh, M. Y., Choi, J., Qadri, I., Friedman, J. E. & Sanyal, A. J.(2008). Hepatitis C virus infection: molecular pathways to metabolic syndrome. Hepatology 47, 2127–2133.[CrossRef] [Google Scholar]
  44. Shimano, H., Horton, J. D., Shimomura, I., Hammer, R. E., Brown, M. S. & Goldstein, J. L.(1997). Isoform 1c of sterol regulatory element binding protein is less active than isoform 1a in livers of transgenic mice and in cultured cells. J Clin Invest 99, 846–854.[CrossRef] [Google Scholar]
  45. Street, A., Macdonald, A., Crowder, K. & Harris, M.(2004). The hepatitis C virus NS5A protein activates a phosphoinositide 3-kinase dependent survival signalling cascade. J Biol Chem 279, 12232–12241.[CrossRef] [Google Scholar]
  46. Taniguchi, C. M., Kondo, T., Sajan, M., Luo, J., Bronson, R., Asano, T., Farese, R., Cantley, L. C. & Kahn, C. R.(2006). Divergent regulation of hepatic glucose and lipid metabolism by phosphoinositide 3-kinase via Akt and PKCλ/ζ. Cell Metab 3, 343–353.[CrossRef] [Google Scholar]
  47. Waris, G., Felmlee, D. J., Negro, F. & Siddiqui, A.(2007). Hepatitis C virus induces proteolytic cleavage of sterol regulatory element binding proteins and stimulates their phosphorylation via oxidative stress. J Virol 81, 8122–8130.[CrossRef] [Google Scholar]
  48. Yap, T. A., Garrett, M. D., Walton, M. I., Raynaud, F., de Bono, J. S. & Workman, P.(2008). Targeting the PI3K-AKT-mTOR pathway: progress, pitfalls, and promises. Curr Opin Pharmacol 8, 393–412.[CrossRef] [Google Scholar]
/content/journal/jgv/10.1099/vir.0.017418-0
Loading
/content/journal/jgv/10.1099/vir.0.017418-0
Loading

Data & Media loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error