Viperin binds STING and enhances the type‐I interferon response following dsDNA detection

Abstract

Viperin is an interferon‐inducible protein that is pivotal for eliciting an effective immune response against an array of diverse viral pathogens. Here we describe a mechanism of viperin’s broad antiviral activity by demonstrating the protein’s ability to synergistically enhance the innate immune dsDNA signaling pathway to limit viral infection. Viperin co‐localized with the key signaling molecules of the innate immune dsDNA sensing pathway, STING and TBK1; binding directly to STING and inducing enhanced K63‐linked polyubiquitination of TBK1. Subsequent analysis identified viperin’s necessity to bind the cytosolic iron‐sulfur assembly component 2A, to prolong its enhancement of the type‐I interferon response to aberrant dsDNA. Here we show that viperin facilitates the formation of a signaling enhanceosome, to coordinate efficient signal transduction following activation of the dsDNA signaling pathway, which results in an enhanced antiviral state. We also provide evidence for viperin’s radical SAM enzymatic activity to self‐limit its immunomodulatory functions. These data further define viperin’s role as a positive regulator of innate immune signaling, offering a mechanism of viperin’s broad antiviral capacity.

The Antiviral Enzyme, Viperin, Activates Protein Ubiquitination by the E3 Ubiquitin Ligase, TRAF6

“…In addition to synthesizing ddhCTP, viperin interacts with a wide range of cellular and viral proteins. − This extensive network of protein–protein interactions remains poorly understood but constitutes an equally important aspect of the enzyme’s antiviral properties. In many cases, it appears that viperin exerts its antiviral effects by facilitating the degradation of cellular and viral proteins important for viral replication .…”

Lipid Droplet Motility Increases Following Viral Immune Stimulation

“…Organelle-organelle communication is critical for the transfer of proteins and lipids to fuel cellular events, and following detection of invading viral nucleic acid by sentinel innate immune receptors, important adaptor proteins within this pathway come together to form enhansosomes. Multiple proteins involved in the antiviral response have been shown to facilitate enhansosome formation with the LD as a platform, and it is possible that LD movement might facilitate this activity [25,26,47]. Additionally, recent work has demonstrated that LDs move away from mitochondrial contacts following detection of bacterial LPS by sentinel innate immune receptors, towards intracellular bacteria, facilitating a cellular anti-bacterial response, perhaps indicating that LD movement is critical following pathogen infection to ensure a good outcome for the host cell.…”

“…This accumulation of LDs has been shown to drive an enhanced immune response in respect to viral infection, and to alter LD-mitochondrial interactions which underpin metabolic changes in the cell [21,23,24]. Additionally, it has recently been demonstrated that the LD resident protein, viperin, interacts with STING, likely on the Golgi and the ER, as well as TRAF6 and IRAK1 in the TLR7/9 pathways [25,26]. It is possible that the LD is involved in multiple organelle interactions that may facilitate and underpin a successful antiviral response following cellular infection.…”

Viperin has species-specific roles in response to herpes simplex virus infection

“…The rest of DNA fragments with deletions of different regions of viperin, including the deletion of residues 9 to 42 (Δ9–42), 71 to 182 (Δ71–182) and 218 to 361 (Δ218–361), were amplified from the resulting full-length mouse viperin plasmid (p3xFLAG-viperin) and the amplicons then were digested with corresponding restriction enzymes, followed by ligation with p3xFLAG-CMV-14 vector linearized by Kpn I and Xba I enzymes. Human viperin-GFP-c1 or pGFP-c1 empty vector [ 33 ] was supplied by K. Helbig. Specific guide RNA targeting viperin (5′-CACCGTGTCATTAATCGCTTCAACG-3′ and 5′-AAACCGTTGAAGCGATTAATGACAC-3′) was inserted into a lentiCRISPR v2 vector containing mCherry coding sequence in the Th111I enzyme cutting site.…”