USP18 positively regulates innate antiviral immunity by promoting K63-linked polyubiquitination of MAVS

Jinxiu Hou,Yi Zheng,Huiqing Liu,Fan Yi,Bingyu Liu,Chengjiang Gao,Ze Zhao,Lei Zhang,Chunhong Ma,Lulu Han

doi:10.1038/s41467-021-23219-4

Abstract

Activation of MAVS, an adaptor molecule in Rig-I-like receptor (RLR) signaling, is indispensable for antiviral immunity, yet the molecular mechanisms modulating MAVS activation are not completely understood. Ubiquitination has a central function in regulating the activity of MAVS. Here, we demonstrate that a mitochondria-localized deubiquitinase USP18 specifically interacts with MAVS, promotes K63-linked polyubiquitination and subsequent aggregation of MAVS. USP18 upregulates the expression and production of type I interferon following infection with Sendai virus (SeV) or Encephalomyocarditis virus (EMCV). Mice with a deficiency of USP18 are more susceptible to RNA virus infection. USP18 functions as a scaffold protein to facilitate the re-localization of TRIM31 and enhances the interaction between TRIM31 and MAVS in mitochondria. Our results indicate that USP18 functions as a post-translational modulator of MAVS-mediated antiviral signaling.

Highlights

Activation of mitochondrial antiviral signaling protein (MAVS), an adaptor molecule in Rig-I-like receptor (RLR) signaling, is indispensable for antiviral immunity, yet the molecular mechanisms modulating MAVS activation are not completely understood
Since MAVS is localized in the outer membrane of mitochondria and is extensively regulated by ubiquitination modification, we speculated DUBs present in mitochondria could cooperate with E3 ubiquitin ligase to tightly regulate the ubiquitination level of MAVS
We found Ubiquitin-specific peptidase 18 (USP18) significantly enhanced, rather than reduced, the polyubiquitination level of MAVS compared to other DUBs (Fig. 1b)

Summary

Results

We observed that the protein level of USP18 was enhanced in mitochondria rather than ER following RNA virus infection (Fig. 1f) These data demonstrated that USP18 is a mitochondrion-associated protein, likely involved in the regulation of antiviral innate immunity through promoting MAVS ubiquitination. We found that pretreatment of MEF cells with mouse recombinant IFN-β led to an enhanced difference between Usp18+/+ and Usp18−/− cells following SeV infection (Fig. 2g) These data suggest type I IFN and IFNAR partially contribute to the regulatory effect of USP18 on RLR-mediated signaling. Since MAVS is localized in mitochondria, we further isolated the mitochondrial fraction and observed an enhanced interaction between MAVS and USP18 in mitochondria following SeV infection (Fig. 4h) Together, these results suggested that USP18 primarily targets MAVS in the RLR signaling pathway.

Spleen

Discussion

Methods