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Characterization of the roles of two regulators of virus infection: Gp78 and BPIFB3

Jacobs, Jana (2014) Characterization of the roles of two regulators of virus infection: Gp78 and BPIFB3. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Over the course of the viral life cycle many host cell factors act to either restrict or facilitate viral infection. Identification of these factors gives insight into the cell biology and virology of viral infection, perhaps even leading to identification of therapeutic targets. A highly efficient and un-biased method for identifying these factors is high-throughput RNAi screening. Our lab previously conducted such a screen in search of host cell factors that regulate enterovirus infection, and this dissertation describes characterization of two screen ‘hits’: Gp78, whose depletion restricted enterovirus infection, and BPIFB3, whose depletion enhanced enterovirus infection. In aim 1 we show that the E3 ubiquitin ligase Gp78 is a regulator of the retinoic acid-inducible gene 1 (RIG-I)-like receptor (RLR) antiviral signaling pathway. We show that depletion of Gp78 results in enhancement of type I interferon (IFN) signaling, restricting RNA virus infection. Mechanistically, we show that Gp78 modulates type I IFN induction by altering both the expression and signaling of the mitochondria-localized RLR adaptor mitochondrial antiviral signaling (MAVS). Our data implicate two parallel pathways by which Gp78 regulates MAVS signaling—one pathway requires its E3 ubiquitin ligase activity to directly degrade MAVS, whereas the other pathway occurs independently of these activities, but requires association between the Gp78 RING domain and MAVS. In aim 2, we characterize the role of bactericidal permeability-increasing protein (BPI) fold-containing family B member 3 (BPIFB3), a member of the lipid-binding antimicrobial BPI/lipopolysaccharide (LPS) binding protein (LBP) family of proteins, in viral infection. We show that BPIFB3 is ER-localized, and examination of ER morphology upon BPIFB3 depletion shows that it is involved in maintenance of ER architecture. We further show that ER-regulated calcium homeostasis is also disrupted in the absence of BPIFB3. Examination of the role of BPIFB3 in viral infection led to the finding that depletion of BPIFB3 enhances VSV-induced syncytia formation. The increase in syncytia could be correlated with an observed increase in endosome/lysosome number and size, although concrete evidence to support this connection is lacking at this time. Lastly, we show that BPIFB3 plays a role in infection of a diverse panel of viruses, all of which require host-derived membranes for their life cycles. Taken together, our data show that BPIFB3 is a novel component of the ER that is responsible for maintenance of ER morphology, and that depletion of BPIFB3 affects replication of viruses that utilize host-derived ER membranes or trafficking for their life cycles. This project is significant to public health because it furthers understanding of virus-host cell interaction, which is crucial for development of efficient and targeted anti-viral therapeutics.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Jacobs, Janajlj64@pitt.eduJLJ64
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCoyne, Carolyn Bcoynec2@pitt.eduCOYNEC2
Committee MemberSarkar, Saumendra Nsaumen@pitt.eduSAUMEN
Committee MemberReinhart, Todd A.reinhar@pitt.eduREINHAR
Committee MemberAyyavoo, Velpandivelpandi@pitt.eduVELPANDI
Date: 27 June 2014
Date Type: Publication
Defense Date: 9 April 2014
Approval Date: 27 June 2014
Submission Date: 7 April 2014
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 139
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Infectious Diseases and Microbiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: viral infection, innate immunity, virus-host cell interaction
Date Deposited: 27 Jun 2014 19:19
Last Modified: 15 Nov 2016 14:18


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