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[Effects of hepatitis C virus proteins on the interferon-stimulated signal transduction]
1Department of Analytical Health Science, Tokyo Medical and Dental University.
Abstract:
The mutation number in the interferon sensitivity determining region(ISDR) (aa2209-2248) in the nonstructural 5A(NS5A) region of hepatitis C virus(HCV) has been shown to correlate with the sensitivity of the virus to interferon treatment. To clearify this mechanism, the functions of the NS5A protein have extensively been studied. The NS5A protein has been shown to be phosphorylated. The NS5A protein 1) is a transactivator, 2) represses the expression of interferon-stimulated genes, 3) binds with PKR, an interferon-stimulated gene, and inhibits its activity, and 4) may inhibit interferon-induced apoptosis of HCV-infected hepatocytes. These effects of the NS5A are different depending on the ISDR types. The E2 protein also can bind with PKR and inhibits its activity. These mechanisms may explain the low responsiveness of HCV to interferon treatment and the difference in the sensitivity to interferon among the genotypes and ISDR types.
Insights
Hepatitis C virus (HCV) nonstructural 5A (NS5A) protein mutations in the ISDR influence interferon treatment sensitivity. NS5A
Area of Science:
- Virology
- Immunology
- Hepatitis C Research
Background:
- The interferon sensitivity determining region (ISDR) in hepatitis C virus (HCV) nonstructural 5A (NS5A) protein is crucial for treatment response.
- Understanding NS5A protein functions is key to clarifying mechanisms of interferon resistance in HCV infection.
Purpose of the Study:
- To elucidate the functional mechanisms of the NS5A protein in relation to interferon sensitivity in HCV.
- To investigate how NS5A protein functions, influenced by ISDR types, affect viral response to interferon therapy.
Main Methods:
- Extensive study of NS5A protein functions, including its phosphorylation status.
- Analysis of NS5A's role as a transactivator and its interaction with interferon-stimulated genes and PKR.
Main Results:
- NS5A protein exhibits multiple functions: transactivation, repression of interferon-stimulated genes, and inhibition of PKR activity.
- These NS5A functions vary based on different ISDR types, impacting HCV's response to interferon.
- The E2 protein also interacts with PKR, potentially contributing to interferon resistance.
Conclusions:
- NS5A protein's diverse functions and ISDR variations contribute significantly to HCV's low responsiveness to interferon treatment.
- These findings explain differential sensitivity to interferon among HCV genotypes and ISDR types.