SRCAP is involved in porcine reproductive and respiratory syndrome virus activated Notch signaling pathway

Porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of porcine reproductive and respiratory syndrome (PRRS); a disease of pigs, which results in great economic losses in the pork industry. The non-structural protein 4 (Nsp4), a 3C-like serine protease responsible for most non-structural protein processing, plays an essential role in PRRSV infection. We used label-free quantitative proteomics to elucidate the Nsp4 interactome and SRCAP was identified as one of the interactors. SRCAP facilitated PRRSV infection by activating non-canonical Notch signaling. The ATPase I-IV domain in SRCAP and the (122)VITEA(126) in Nsp4 were identified as the interacting sites. The infection of recovered mutant rTA-12/5A ((122)AAAAA(126)) could not activate Notch signaling. The results indicated that (122)VITEA(126) in Nsp4 were key sites to determine the function of SRCAP and their interaction. A function of Nsp4 in activating the Notch signaling pathway was discovered. Block Notch signaling pathway could inhibit PRRSV infection both in vitro and in vivo which may lead to the development of novel therapeutic antiviral strategies. IMPORTANCE In the present study, the interactome of the NSP4 originating from PRRSV was studied and SRCAP was confirmed as one of the interactors. Mechanism study showed the interaction of Nsp4 and SRCAP was found to facilitate PRRSV infection by activating non-canonical Notch signaling. ATPase I -IV domain in SRCAP and the (122)VITEA(126) in Nsp4 were identified as the interacting sites that demined the activating of Notch signaling. Block Notch signaling pathway could inhibit PRRSV infection in vitro and in vivo which may be a new target for antiviral drug development.