S-palmitoylation of the viral Nsp10 by ZDHHC7 restricts PRRSV replication but is counteracted by Nsp2, Nsp4 and GP5

Reversible S-palmitoylation, initiated by the Zinc finger aspartate-histidine-histidine-cysteine domain (ZDHHC) proteins and erased by the de-palmitoylases, plays an important role in the antiviral immune pathway. Our previous screening identified ZDHHC7 as a potent restriction factor for PRRSV. However, the mechanisms underlying ZDHHC7-mediated suppression of PRRSV replication remains unclear. Here, we showed that PRRSV RNA replication is impaired by ZDHHC7 in an acyltransferase-dependent manner. This antiviral effect was achieved by S-palmitoylation of Nsp10 (Nonstructural protein 10), which weakened the binding between viral RNA and Nsp10. By cleaving porcine ZDHHC7 at E226, PRRSV Nsp4 impaired the S-palmitoylation of Nsp10, STING, and MAVS. Additionally, the cleaved fragments did not inhibit PRRSV multiplication, whereas the cleavage-resistant mutant ZDHHC7-E226A exhibited enhanced antiviral activity. Finally, we demonstrated that PRRSV Nsp2 and GP5 (glycoprotein 5) induce the transcription of APT1 (Acyl-protein thioesterase 1) through the transcription factor NFATC3 to reverse the S-palmitoylation level of Nsp10. Collectively, this work uncovers the antagonistic strategy employed by PRRSV to dampen the antiviral function of ZDHHC7, which deepens our understanding of the immune evasion mechanisms during PRRSV infection.