Date of Award

Fall 12-2023

Degree Type

Dissertation

Degree Name

PhD Molecular Bioscience

Department

Biology

Advisor

Daniel Brian Nichols, Ph.D.

Committee Member

Tinchun Chu, Ph.D.

Committee Member

Jessica Cottrell, Ph.D.

Committee Member

Constantine Bitsaktsis, Ph.D.

Committee Member

Brianne Barker, Ph.D.

Keywords

Molluscum contagiosum virus; cGAS; STING; TBK1; Hsp90; interferon β

Abstract

Molluscum contagiosum virus (MCV) is the sole member of its genus within the Poxviridae family. MCV is a dermatotropic virus that causes persistent infections that manifest as skin papules. MCV encodes a vast array of immune evasion molecules, many of which have yet to be functionally characterized. The MC159 and MC160 proteins are two homologs that MCV uses to evade the host immune response. Both of these proteins have been described in their functions in tumor necrosis factor(TNF)-induced apoptosis and TNF-induced nuclear factor κB (NF-κB) signaling and recently in mitochondrial antiviral signaling (MAVS) protein-mediated interferon regulatory factor (IRF) signaling of interferon-β (IFN-β). Here, I describe both MCV homologs in a new context, the perturbation of cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING)-mediated IFN-β activity. MC160 expression but, not the expression of MC159 dampens cGAS/STING-mediated induction of type 1 IFN in HEK 293T cells. I attribute MC160’s novel ability to block cGAS/STING-induction of type 1 IFNs to the reduction of both K63-linked ubiquitination and phosphorylation of TANK-binding kinase-1 (TBK1). Further, in cells expressing the MC160 protein, the ubiquitination of STING was also reduced. Immunoblotting showed consistent reductions in the protein expression of total TBK1, phosphoTBK1 and convincing reductions in the protein expression of STING and cGAS. Co-immunoprecipitations found that MC160 interacts with TBK1 and preliminarily may interact with STING. Additionally, both of the death effector domains (DEDs) of MC160 were required for the reduction of cGAS/STING-mediated IFN-β activity. Our model indicates that the MC160 protein targets the TBK1 signaling complex, which is indicated in many innate immune signaling pathways like the aforementioned cGAS/STING signaling pathway, MDA5/RIG-I/MAVS, non-canonical NF-κB signaling, and possibly TBK1-mediated xenophagy.

Download

Available for download on Monday, October 24, 2033

Share

COinS