Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Biological and Environmental Sciences

Specialization

Cell & Molecular Biology

Department

Cell & Molecular Biology

First Advisor

Alan L. Rothman

Abstract

Dengue virus (DENV) infection is the most prevalent arthropod-borne virus disease. There are estimated 100 million symptomatic cases of dengue disease per year worldwide. A lack of effective antiviral therapies or vaccines makes DENV infections a major global health concern. Therefore, understanding the viral and host factors contributing to the disease pathogenesis is critical. DENV has been shown to effectively counteract host innate immune mechanisms. In particular, DENV protease, NS3 has emerged as an inhibitor of host cellular signaling by targeting crucial host proteins. Here we identified RIPK1 as a novel target of DENV NS3. RIPK1 is a central mediator of innate immune regulation downstream of TNFR1, TLR3, TLR4, RIG-I, and MDA-5. The outcomes of RIPK1-mediated inflammatory signaling include NF-kB and MAPK activation and IRF3/IRF7 phosphorylation. RIPK1 also regulates cell death signaling by modulating extrinsic apoptosis and necroptosis.

We observed that RIPK1 levels were significantly decreased in numerous cell types with DENV infection. DENV NS3 was responsible for decreased RIPK1 levels as shown by overexpression experiments. NS3 protease activity was fundamental for this effect, because the overexpression of a catalytically inactive protease mutant (NS2B3-S135A) did not result in a significant RIPK1 reduction. Additionally, both wild type and protease mutant NS3 physically interacted with RIPK1 as shown by coimmunoprecipitation experiments. Consequently, DENV inhibited NF-kB activation downstream of TNFR1 and TLR3 receptors by targeting RIPK1. Furthermore, we detected that DENV did not induce necroptosis and further suppressed TNFR1- induced necroptosis. Our findings add RIPK1 to the list of host proteins targeted by DENV NS3 and expand the knowledge of strategies used by DENV to evade innate immune responses. Manipulation of host cell RIPK1 signaling by DENV may contribute to disease pathogenesis.

Available for download on Sunday, August 15, 2021

Share

COinS