Porcine reproductive and respiratory syndrome (
PRRS) is a highly
infectious disease caused by
PRRS virus (PRRSV) that causes great economic losses to the swine industry worldwide. PRRSV has been recognized to modulate the host
antiviral interferon (IFN) response and downstream
interferon-stimulated gene expression to intercept the
antiviral effect of host cells. Guanylate-
binding proteins (GBPs) are IFN-inducible
GTPases that exert broad
antiviral activity against several
DNA and RNA viruses, of which GBP1 is considered to play a pivotal role. However, the role of GBP1 in PRRSV replication remains unknown. The present study showed that overexpression of GBP1 notably inhibited PRRSV
infection, while the knockdown of endogenous GBP1 promoted PRRSV
infection. The K51 and R48 residues of GBP1 were essential for the suppression of PRRSV replication. Furthermore, GBP1 abrogated PRRSV replication by disrupting normal fibrous actin structures, which was indispensable for effective PRRSV replication. By using a co-immunoprecipitation assay, we found that GBP1 interacted with the non-structural
protein 4 (nsp4)
protein of PRRSV, and this interaction was mapped to the N-terminal globular
GTPase domain of GBP1 and
amino acids 1-69 of nsp4. PRRSV
infection significantly downregulated GBP1
protein expression in Marc-145 cells, and nsp4, a 3C-like
serine proteinase, was responsible for GBP1 cleavage, and the cleaved site was located at
glutamic acid 338 of GBP1. Additionally, the anti-PRRSV activity of GBP1 was antagonized by nsp4. Taken together, these findings expand our understanding of the sophisticated interaction between PRRSV and host cells, PRRSV pathogenesis and its mechanisms of evading the host immune response.