Biomedical Sciences ETDs

Author

Jessica Smith

Publication Date

7-1-2008

Abstract

Human papillomaviruses (HPVs) are small, nonenveloped double stranded DNA viruses that display a strict species and cell type tropism for human epithelial cells. The association between high-risk HPV types and cervical cancer is well established. Additionally, HPVs have been implicated as cofactors in development of several other epithelial cancer types. The difficulty associated with producing infectious HPV stocks, coupled with the complexity of detecting infection using standard virological methods has hindered research into some basic aspects of HPV biology. Recent advances have allowed for the production of high yield stocks of HPV particles for use in infectivity studies and has facilitated research on HPV cellular entry. Using a combination of fluorescent tracking and infectivity studies, we have elucidated the infectious entry pathway and trafficking of HPV31 particles following internalization into human (HKs). Upon initial attachment, HPV31 associates with lipid rafts before internalization via caveolae, a process that is dependent on dynamin-2. Virions are observed trafficking through caveosomes before transport to the endosomal pathway in a Rab5-dependent fashion. Progression through the endosomal pathway results in exposure to decreasing pH, which promotes conformational changes in the virion capsid. These changes are associated with escape of the viral genome and/or genome-L2 complex to the cytoplasm, an event necessary for trafficking to the nucleus and production of viral transcripts. This pathway represents a unique viral trafficking route. In addition to entry and trafficking events of HPV31, the research presented here elucidates signaling cascades induced during HPV31 attachment to cells and internalization, as well as cytoskeletal rearrangements observed during these events. Signaling through protein tyrosine phosphatases was found to regulate microtubule reorganization that is required for association of HPV31 particles with lipid rafts. Following lipid raft localization, several classes of cellular signaling are activated. Tyrosine kinase and phosphatidyl-inositol-3 kinase activation was found to be required for actin cytoskeletal rearrangements that result in filopodia formation at the cell surface. Retrograde transport of virions along filopodial projections suggests that these structures play a role in facilitating uptake of virions from the extracellular matrix of host cells and increase infection efficiency of HPV31.

Keywords

papillomavirus, virus entry, caveolae, rab gtpase, filopodia

Sponsors

NIH T32 training grant NIH CA85747 UNM Cancer Research and Treatment Center

Document Type

Dissertation

Language

English

Degree Name

Biomedical Sciences

Level of Degree

Doctoral

Department Name

Biomedical Sciences Graduate Program

First Advisor

Ozbun, Michelle

First Committee Member (Chair)

Ozbun, Michelle

Second Committee Member

Hjelle, Brian

Third Committee Member

Wheeler, Cosette

Fourth Committee Member

Chackerian, Bryce

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