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The Effect of Viral Envelope Glycoproteins on Extracellular Vesicle Communication and Function

Troyer, Zach Andrew
http://orcid.org/0000-0002-1821-7334
http://rave.ohiolink.edu/etdc/view?acc_num=case1627312642031895

Abstract Details

2021, Doctor of Philosophy, Case Western Reserve University, Molecular Virology.
Extracellular vesicles (EVs) are lipid-bilayer enclosed, cell-derived nanoparticles released constitutively by most cells. EVs carry proteins and nucleic acids from their cells of origin, facilitating intercellular communication through a variety of different pathways. These include signaling through cellular receptors, triggering immune responses, and delivering bioactive cargos after EV internalization. Viruses share many characteristics with EVs, including size, structure, and biogenesis pathways. Virally infected cells continue to release EVs, resulting in the production of virus-induced EVs that carry viral elements like proteins or RNAs. Viral fusion proteins – viral envelope glycoproteins that mediate virus/cell membrane fusion – are often incorporated by virus-induced EVs. In this work, we investigated the effect that viral fusion protein incorporation has on EV communication and functionality. First, we investigated the spike protein of the current pandemic virus SARS-CoV-2. Interestingly, we found that EVs released from spike expressing cells did incorporate this type I viral fusion protein. These spike(+) EVs displayed the spike protein in a conformation available for antibody binding, allowing the EVs to serve as decoy targets for neutralizing antibodies. This held true with both convalescent patient serum and a commercial neutralizing antibody, with the effect of reducing virus neutralization and increasing infection. The second component of this work concerned the development of EV/cell membrane fusion assays to monitor EV cargo delivery. This EV communication pathway is particularly important in disease, where EVs are thought to be capable of influencing cells through membrane fusion and delivery of bioactive cargos to cell cytosol. We successfully developed two EV fusion assays, based on delivery of the proteins beta-lactamase and Cre-recombinase. In the third and final component of this work, we utilized these fusion assays to investigate the incidence of EV/cell membrane fusion and cargo delivery. Surprisingly, we found that most EVs were incapable of fusion. Supplementation of EVs with viral fusion proteins, however, could confer fusogenicity to EVs. These viral fusion proteins could originate from circulating viruses, or endogenous retroviral elements encoded in the human genome. These findings alter the current understanding of EV-mediated intercellular communication, demonstrating that captured viral proteins play a significant functional role.
John Tilton, M.D. (Advisor)
Alan Levine, Ph.D. (Committee Chair)
Alex Huang, M.D./Ph.D. (Committee Member)
Scott Sieg, Ph.D. (Committee Member)
232 p.
Biomedical Research; Molecular Biology; Virology
extracellular vesicles; viruses; viral fusion proteins; glycoproteins; SARS-CoV-2; COVID-19; neutralizing antibodies; spike; VSV-G; Syncytin-1; HERV; endogenous retrovirus; fusion; membrane; signaling; intercellular communication

Recommended Citations

Citations

  • Troyer, Z. A. (2021). The Effect of Viral Envelope Glycoproteins on Extracellular Vesicle Communication and Function [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1627312642031895

    APA Style (7th edition)

  • Troyer, Zach. The Effect of Viral Envelope Glycoproteins on Extracellular Vesicle Communication and Function. 2021. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1627312642031895.

    MLA Style (8th edition)

  • Troyer, Zach. "The Effect of Viral Envelope Glycoproteins on Extracellular Vesicle Communication and Function." Doctoral dissertation, Case Western Reserve University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1627312642031895

    Chicago Manual of Style (17th edition)

case1627312642031895
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.