To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress
abstract: Cell death is a powerful tool through which organisms can inhibit the spread of viruses by preventing their replication. In this work, I used viral and chemical stressors to elucidate the mechanisms by which one anti-viral system might be activated over another, focusing on the programmabl...
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ndltd-asu.edu-item-504602018-10-02T03:01:04Z To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress abstract: Cell death is a powerful tool through which organisms can inhibit the spread of viruses by preventing their replication. In this work, I used viral and chemical stressors to elucidate the mechanisms by which one anti-viral system might be activated over another, focusing on the programmable death pathway necroptosis and Protein Kinase R (PKR). PKR can detect viral dsRNA and trigger antiviral effects such as cessation of translation and induction of programmed death. Necroptosis is a rapid cellular death that can be induced via sensors such as DNA-dependent activator of IFN-regulatory factors (DAI), also known as Z-DNA-binding protein 1 (ZBP1). DAI contains a Z-form nucleic acid (ZNA) binding domain. E3, the primary vaccinia virus (VACV) interferon resistance protein, contains a similar domain in its amino terminus. We have previously reported this domain to be necessary for the inhibition of both PKR activation and DAI/ZBP1-mediated necroptosis. Monkeypox virus is a reemerging human pathogen. Despite a partial amino-terminal deletion in its E3 homolog, it does not activate PKR. In chapter 2, I show that MPXV produces less dsRNA than VACV, which could explain how the virus avoids activating PKR. The amino-terminus of vaccinia is associated with ZNA binding, inhibition of PKR, and inhibition of necroptosis. To determine the roles of PKR inhibition and ZNA binding in necroptosis inhibition, I characterized the VACV mutants Za(ADAR1)-E3, which binds ZNA but does not inhibit PKR, and E3:Y48A, which cannot bind ZNA. I found that while Za(ADAR1)-E3 fails to induce necroptosis, E3:Y48A does not activate PKR but does induce necroptosis. This suggests that Z-form nucleic acid binding is not necessary for vaccinia E3-mediated inhibition of PKR, nor is the inhibition of PKR sufficient for the inhibition of necroptosis. Finally, all known ZNA-binding proteins have immune functions and home to stress granules. I asked if stress granule formation alone could lead to necroptosis. I found that in L929 cells sodium arsenite, a known inducer of stress granules, could trigger DAI-dependent necroptosis. This suggests that DAI/ZBP1 is not necessarily a sensor of viral ligands but perhaps is a sensor of stress signals brought about by infection. Dissertation/Thesis Johnson, Brian Patrick (Author) Jacobs, Bertram L (Advisor) Blattman, Joseph N (Committee member) Langland, Jeffrey O (Committee member) Stout, Valerie G (Committee member) Arizona State University (Publisher) Virology Cellular biology Cell Death Monkeypox Necroptosis Poxvirus Vaccinia eng 136 pages Doctoral Dissertation Biological Design 2018 Doctoral Dissertation http://hdl.handle.net/2286/R.I.50460 http://rightsstatements.org/vocab/InC/1.0/ 2018 |
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language |
English |
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Doctoral Thesis |
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Virology Cellular biology Cell Death Monkeypox Necroptosis Poxvirus Vaccinia |
spellingShingle |
Virology Cellular biology Cell Death Monkeypox Necroptosis Poxvirus Vaccinia To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
description |
abstract: Cell death is a powerful tool through which organisms can inhibit the spread of viruses by preventing their replication. In this work, I used viral and chemical stressors to elucidate the mechanisms by which one anti-viral system might be activated over another, focusing on the programmable death pathway necroptosis and Protein Kinase R (PKR). PKR can detect viral dsRNA and trigger antiviral effects such as cessation of translation and induction of programmed death. Necroptosis is a rapid cellular death that can be induced via sensors such as DNA-dependent activator of IFN-regulatory factors (DAI), also known as Z-DNA-binding protein 1 (ZBP1). DAI contains a Z-form nucleic acid (ZNA) binding domain. E3, the primary vaccinia virus (VACV) interferon resistance protein, contains a similar domain in its amino terminus. We have previously reported this domain to be necessary for the inhibition of both PKR activation and DAI/ZBP1-mediated necroptosis.
Monkeypox virus is a reemerging human pathogen. Despite a partial amino-terminal deletion in its E3 homolog, it does not activate PKR. In chapter 2, I show that MPXV produces less dsRNA than VACV, which could explain how the virus avoids activating PKR.
The amino-terminus of vaccinia is associated with ZNA binding, inhibition of PKR, and inhibition of necroptosis. To determine the roles of PKR inhibition and ZNA binding in necroptosis inhibition, I characterized the VACV mutants Za(ADAR1)-E3, which binds ZNA but does not inhibit PKR, and E3:Y48A, which cannot bind ZNA. I found that while Za(ADAR1)-E3 fails to induce necroptosis, E3:Y48A does not activate PKR but does induce necroptosis. This suggests that Z-form nucleic acid binding is not necessary for vaccinia E3-mediated inhibition of PKR, nor is the inhibition of PKR sufficient for the inhibition of necroptosis.
Finally, all known ZNA-binding proteins have immune functions and home to stress granules. I asked if stress granule formation alone could lead to necroptosis. I found that in L929 cells sodium arsenite, a known inducer of stress granules, could trigger DAI-dependent necroptosis. This suggests that DAI/ZBP1 is not necessarily a sensor of viral ligands but perhaps is a sensor of stress signals brought about by infection. === Dissertation/Thesis === Doctoral Dissertation Biological Design 2018 |
author2 |
Johnson, Brian Patrick (Author) |
author_facet |
Johnson, Brian Patrick (Author) |
title |
To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
title_short |
To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
title_full |
To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
title_fullStr |
To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
title_full_unstemmed |
To Explode or to Implode: How Cells Decide Between Apoptosis and Necroptosis Following Viral or Chemical Stress |
title_sort |
to explode or to implode: how cells decide between apoptosis and necroptosis following viral or chemical stress |
publishDate |
2018 |
url |
http://hdl.handle.net/2286/R.I.50460 |
_version_ |
1718756995076456448 |