Pseudorabies virus tegument protein UL13 recruits RNF5 to inhibit STING-mediated antiviral immunity

Abstract

Pseudorabies virus (PRV) has evolved various immune evasion mechanisms that target host antiviral immune responses. However, it is unclear whether and how PRV encoded proteins modulate the cGAS-STING axis for immune evasion. Here, we show that PRV tegument protein UL13 inhibits STING-mediated antiviral signaling via regulation of STING stability. Mechanistically, UL13 interacts with the CDN domain of STING and recruits the E3 ligase RING-finger protein 5 (RNF5) to promote K27-/K29-linked ubiquitination and degradation of STING. Consequently, deficiency of RNF5 enhances host antiviral immune responses triggered by PRV infection. In addition, mutant PRV lacking UL13 impaired in antagonism of STING-mediated production of type I IFNs and shows attenuated pathogenicity in mice. Our findings suggest that PRV UL13 functions as an antagonist of IFN signaling via a novel mechanism by targeting STING to persistently evade host antiviral responses.

Pseudorabies Virus Tegument Protein UL13 Suppresses RLR-Mediated Antiviral Innate Immunity through Regulating Receptor Transcription

“…The role of the PRV tegument protein UL13 has been indicated in the suppression of host antiviral immune responses [ 24 , 29 ]. To confirm the suppressive effect of UL13 on RLR-mediated IFN-I signaling, we generated stable HEK293T cells ectopically expressing Flag-tagged UL13 (UL13-HEK293T cells).…”

“…HEK293T cells, PK-15 cells, and BHK-21 cells were purchased from the American Type Culture Collection (ATCC, Manassas, VA, USA). Stable PK-15 cells ectopically expressing PRV UL13 (UL13-PK-15 cells), along with control cells, were generated previously [ 24 ]. Cells were maintained in Dulbecco’s minimal essential medium (DMEM) (Gibco, New York, NY, USA) containing 10% fetal bovine serum (FBS) (Biological Industries, Israel) and 1% penicillin–streptomycin (Gibco, New York, NY, USA) at 37 °C in 5% CO 2 .…”

“…PRV (Bartha-K61 strain) was purchased from the China Veterinary Culture Collection Center (Cat# CVCC AV249, Beijing, China), and was purified in BHK-21 cells. The PRV-∆UL13 recombinant strain was generated previously [ 24 ]. The wild-type PRV (PRV-WT) and PRV-∆UL13 PRV strains were amplified and titrated in PK-15 cells using standard protocols.…”

“…Stable cell lines were generated as described previously [ 24 ]. Briefly, lentiviral particles were produced in HEK293T cells transfected with two packaging plasmids (psPAX2 and pVSVG) and an empty vector or pCDH-Flag-UL13 plasmid using Lipofectamine 2000 (Invitrogen).…”

“…UL13, a serine/threonine protein kinase, is an important immune escape protein of PRV. Recent reports have found that the PRV tegument protein UL13 acts as an antagonist of cGAS-STING-mediated IFN-β production [ 24 , 25 ]. However, whether UL13 regulates the RLR pathway remains unknown.…”