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Dissertation
Modes of action of two newly identified interferon-induced antiviral proteins, IFITM3 and GBP5, against vesicular stomatitis virus infection
Doctor of Philosophy (Ph.D.), Drexel University
May 2010
DOI:
https://doi.org/10.17918/00009519
Abstract
Type I interferon (IFN-[alpha]/[beta]) plays an essential role in eliminating, or at the very least, controlling the severity of, viral infections in vertebrates. Treatment of cells with IFN-[alpha] typically induces hundreds of IFN-stimulated genes (ISGs) which work cooperatively to inhibit virus infections. However, only a handful of these ISGs have been implicated in direct antiviral action. In our search for novel IFN-induced proteins that may mediate the antiviral function of the cytokines against flaviviruses, we discovered that GBP5, a member of the IFN-induced guanylate binding protein (GBP) family, and IFITM2 and IFITM3, members of the IFN-induced tramsmembrane (IFITM) protein family, were able to inhibit infection of two medically important flaviviruses, West Nile virus and dengue virus, upon expression in HEK293 cells. In order to dissect their antiviral mechanisms, we further demonstrated that GBP5, IFITM2, IFITM3, as well as another recently identified IFN-induced antiviral protein, tetherin (BST-2), potently inhibited vesicular stomatitis virus (VSV) infection. Using this well-studied virus infection system, we showed that the antiviral activity of GBP5 relies on its putative GTPase activity, as well as its putative isoprenylation sequence. In addition, we provide strong evidence suggesting that GBP5 inhibited VSV genome replication, but not virus binding and entry into host cells. In contrast, we found that while both IFITMs and tetherin are plasma membrane proteins, IFITMs inhibited VSV infection by disrupting virus entry into cells, while tetherin inhibited virion particle release from infected cells. Through our mutagenesis studies, which involved the shuffling of structural domains between IFITM3 and IFITM1, we discovered that both the N-terminal 21 amino acid extension and C-terminal transmembrane region of IFITM3 are essential for its antiviral activity. The mutagenesis strategy was determined based on the observation that IFITM1 did not elicit an antiviral activity against VSV, yet shares 70% amino acid identity with IFITM3. In conclusion, our work reveals the distinct antiviral mechanisms of two newly identified antiviral ISGs, whose novel function will help to better understand how the innate immune system works to control of virus infection.
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Details
- Title
- Modes of action of two newly identified interferon-induced antiviral proteins, IFITM3 and GBP5, against vesicular stomatitis virus infection
- Creators
- Jessica Weidner
- Contributors
- Ju-Tao Guo (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- x, 158 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Drexel University
- Other Identifier
- 991021888976904721