RND3 restricts encephalomyocarditis virus replication by promoting IKKε ubiquitination and type I interferon production.

Encephalomyocarditis virus (EMCV), one of the most important picornaviruses, infects many mammalian species and causes encephalitis, myocarditis, neurologic diseases, and diabetes, but the host factors that restrict infection and replication of the virus remain poorly understood. RND3, a member of the Rho GTPase family, is involved in the regulation of actin cytoskeleton dynamics, migration, and proliferation; however, its role in antiviral innate immunity is not clear. Herein, we revealed that the host restriction factor for EMCV replication, RND3, positively regulates type I interferon (IFN-I) induction. We showed that RND3 enhances the production of IFN-β and IFN-stimulated genes, leading to the attenuation of EMCV propagation. Mechanistically, RND3 specifically interacts with IκB kinase epsilon (IKKε) and promotes the TRIM21-mediated K63-linked ubiquitination of IKKε. However, RND3 expression is inhibited by EMCV, establishing a negative regulatory feedback loop. Taken together, these findings provide insight into the molecular mechanisms by which RND3 promotes IFN-I production by targeting IKKε to inhibit viral replication. IMPORTANCE: Host cell restriction factors perform key antiviral functions during viral infection. Herein, we demonstrate that RND3 is a host restriction factor in EMCV infection that plays a role in the antiviral signaling pathway. We found that RND3 is involved in the type I IFN pathway by interacting with IKKε, which negatively regulates EMCV transmission. However, EMCV infection effectively reduces RND3 expression in cells. Collectively, these results reveal the role of RND3 in the IFN pathway and identify potential targets for controlling EMCV infection.