Hepatitis C Virus NS3/4A Protease and the Intracellular Antiviral Response: Mapping Complex Virus-Host Interactions
| dc.contributor.advisor | Gale, Michael, Jr. | en |
| dc.creator | Johnson, Cynthia L. | en |
| dc.date.accessioned | 2010-07-12T18:27:30Z | |
| dc.date.available | 2010-07-12T18:27:30Z | |
| dc.date.issued | 2009-06-17 | |
| dc.description.abstract | Virus infection triggers an innate immune response characterized by host cell production of interferon (IFN). Intermediates of viral replication, including dsRNA, initiate a signaling cascade that is amplified within the cell and alerts neighboring cells of viral invaders. Recognition of dsRNA intermediates occurs through retinoic acid inducible gene-I (RIG-I). RIG-I elicits an antiviral state by binding to the IFN-beta Promoter Stimulator-1 (IPS-1) adaptor protein, activating the latent downstream transcription factors IRF-3 and NF-kappaB. These transcription factors bind to the promoter region of effector genes including IFN-beta, producing an antiviral amplification loop within and around the infected cell. This response is critical for immunity to infection. Hepatitis C virus (HCV) is a serious global health problem with 170 million people chronically infected. HCV persistence is linked to viral regulation of innate host defenses by the nonstructural 3/4A protein complex (NS3/4A) cleavage of IPS-1. NS3 structural composition includes an amino-terminal serine protease and a carboxy-terminal RNA helicase. A structure-function analysis of NS3/4A truncation and deletion mutations was conducted. Mutants lacking the helicase domain retained the ability to control RIG-I signaling, but this regulation was abrogated by truncation of the protease domain. Furthermore, treatment of HCV-infected cells with a NS3/4A protease inhibitor prevented IPS-1 proteolysis, restored RIG-I signaling, and decreased viral protein levels. These results indicate that the NS3/4A protease domain alone can target IPS-1 on the mitochondrial membrane. Current dogma holds that NS3/4A is located on the endoplasmic reticulum, thus the mechanism of NS3/4A targeting IPS-1, a mitochondrial membrane protein, remains unexplained. We have shown that NS3/4A distributes on mitochondria independently of the previously identified NS4A membrane localization motif, in a manner dependent on the first twenty amino acids of the NS3 protease domain. The functional domains of IPS-1 that direct the immune response have not been elucidated. We conducted a structure-function study of IPS-1 that revealed distinct processes of IRF-3 and NF-kappaB activation. Mutational analyses further identified areas of IPS-1 critical for mitochondrial localization, dimerization, and uncoupling IRF-3 and NF-kappaB signaling. These findings improve our understanding of IPS-1 function in innate immunity to virus infection. | en |
| dc.format.digitalOrigin | born digital | en |
| dc.format.medium | Electronic | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.oclc | 754190787 | |
| dc.identifier.uri | https://hdl.handle.net/2152.5/561 | |
| dc.language.iso | en | en |
| dc.subject | Signal Transduction | en |
| dc.subject | Hepatitis C, Chronic | en |
| dc.subject | Hepacivirus | en |
| dc.subject | Peptide Hydrolases | en |
| dc.title | Hepatitis C Virus NS3/4A Protease and the Intracellular Antiviral Response: Mapping Complex Virus-Host Interactions | en |
| dc.type | Thesis | en |
| dc.type.genre | dissertation | en |
| dc.type.material | Text | en |
| thesis.date.available | 2011-06-17 | |
| thesis.degree.department | Graduate School of Biomedical Sciences | en |
| thesis.degree.discipline | Molecular Microbiology | en |
| thesis.degree.grantor | UT Southwestern Medical Center | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |