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A Protocol for Analyzing Hepatitis C Virus Replication
Published on: June 26, 2014
Determinants of hepatitis C virus p7 ion channel function and drug sensitivity identified in vitro
Corine StGelais1, Toshana L Foster, Mark Verow
1Institute of Molecular and Cellular Biology, Astbury Centre for Structural Molecular Biology, Leeds, West Yorkshire, United Kingdom.
Abstract:
Hepatitis C virus (HCV) chronically infects 170 million individuals, causing severe liver disease. Although antiviral chemotherapy exists, the current regimen is ineffective in 50% of cases due to high levels of innate virus resistance. New, virus-specific therapies are forthcoming although their development has been slow and they are few in number, driving the search for new drug targets. The HCV p7 protein forms an ion channel in vitro and is critical for the secretion of infectious virus. p7 displays sensitivity to several classes of compounds, making it an attractive drug target. We recently demonstrated that p7 compound sensitivity varies according to viral genotype, yet little is known of the residues within p7 responsible for channel activity or drug interactions. Here, we have employed a liposome-based assay for p7 channel function to investigate the genetic basis for compound sensitivity. We demonstrate using chimeric p7 proteins that neither the two trans-membrane helices nor the p7 basic loop individually determines compound sensitivity. Using point mutation analysis, we identify amino acids important for channel function and demonstrate that null mutants exert a dominant negative effect over wild-type protein. We show that, of the three hydrophilic regions within the amino-terminal trans-membrane helix, only the conserved histidine at position 17 is important for genotype 1b p7 channel activity. Mutations predicted to play a structural role affect both channel function and oligomerization kinetics. Lastly, we identify a region at the p7 carboxy terminus which may act as a specific sensitivity determinant for the drug amantadine.
Insights
Hepatitis C virus (HCV) p7 protein
Area of Science:
- Virology
- Molecular Biology
- Drug Discovery
Background:
- Hepatitis C virus (HCV) affects 170 million people globally, causing significant liver disease.
- Current antiviral therapies are only effective in 50% of cases due to drug resistance.
- The HCV p7 protein, essential for virus secretion, is a potential drug target due to its ion channel activity and compound sensitivity.
Purpose of the Study:
- To investigate the genetic basis of compound sensitivity in the Hepatitis C virus p7 protein.
- To identify specific amino acid residues responsible for p7 channel function and drug interactions.
- To understand how p7 mutations affect channel activity and drug sensitivity across different viral genotypes.
Main Methods:
- Utilized a liposome-based assay to study p7 ion channel function.
- Employed chimeric p7 proteins to analyze the roles of different protein domains.
- Conducted point mutation analysis to identify critical amino acids.
- Investigated the effects of mutations on channel function, oligomerization, and drug sensitivity.
Main Results:
- Neither the transmembrane helices nor the basic loop alone determined p7 compound sensitivity.
- Identified specific amino acids crucial for p7 channel function; null mutants showed dominant negative effects.
- The conserved histidine at position 17 in the N-terminal transmembrane helix is vital for genotype 1b p7 channel activity.
- Mutations affecting p7 structure impacted both channel function and oligomerization kinetics.
- A region at the p7 carboxy terminus was identified as a potential determinant for amantadine sensitivity.
Conclusions:
- Specific residues within the Hepatitis C virus p7 protein are critical for its ion channel function and sensitivity to antiviral compounds.
- Understanding these genetic determinants can guide the development of more effective, genotype-specific HCV therapies.
- The p7 carboxy terminus may represent a novel target for drugs like amantadine, offering new avenues for HCV treatment.
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