MARCH8 promotes the proteasomal degradation of foot-and-mouth disease virus VP1, VP2, and VP3 to negatively regulate viral replication.

The host cell membrane-associated RING-CH8 protein (MARCH8) functions as an antiviral host factor by targeting viral envelope glycoproteins. Foot-and-mouth disease virus (FMDV) is a non-enveloped, positive-sense, single-stranded RNA virus. The potential impact of MARCH8 on FMDV replication remains uncertain. Here, we found that the overexpression of MARCH8 significantly inhibited FMDV replication in a dose-dependent manner. Conversely, the knockdown of MARCH8 facilitated FMDV replication. Specifically, MARCH8 interacted with VP1, VP2, and VP3, mediating their degradation in a proteasome-dependent manner. MARCH8 catalyzed the K33-linked polyubiquitination of VP1, VP2, and VP3. Moreover, the Lys210 residue of VP1, the Lys63 residue of VP2, and the Lys118 residue of VP3 were identified as critical target sites for MARCH8-mediated degradation. Overall, we conclude that MARCH8 is an intrinsic antiviral factor against FMDV.