Integrin αVβ3 mediates porcine deltacoronavirus infection and inflammatory response through activation of the FAK-PI3K-AKT-nf-κB signalling pathway.

Porcine deltacoronavirus (PDCoV) is an emerging porcine enteropathogenic coronavirus that causes acute watery diarrhoea in piglets, resulting in significant economic losses to the global swine industry. However, the underlying mechanism of PDCoV infection is not well defined, which seriously hinders the development of effective drugs and vaccines. Integrins (ITG) are heterodimeric transmembrane glycoproteins that play important roles in the life cycle of many viruses. In the current study, the viral entry pathways of PDCoV were explored and the role of ITGαVβ3 was investigated during PDCoV infection. Our results showed that the lysosomal acidification inhibitor bafilomycin-A1 (Baf-A1) significantly reduced PDCoV infection, while exogenous protease facilitated PDCoV infection and even allowed PDCoV entry to bypass the endosomal pathway, suggesting PDCoV entry into cells via the endocytic pathway and the exogenous protease-mediated pathway simultaneously. Furthermore, ITGαVβ3 was identified to be involved in PDCoV infection, especially during viral entry stages. PDCoV infection triggers the activation of the focal adhesion kinase (FAK)-phosphatidylinositol 3-kinase (PI3K)-serine/threonine-specific protein kinase (AKT) signalling pathway, and this activation is ITGαVβ3-dependent, suggesting that the activation of the FAK-PI3K-AKT signalling pathway during PDCoV infection is mediated by ITGαVβ3. Our results further demonstrated that PDCoV infection induced the expression of inflammatory cytokines, which was mediated by activation of the ITGαVβ3-FAK-PI3K-AKT-nuclear transcription factor-κB (NF-κB) signalling pathway. Overall, the results revealed that ITGαVβ3 is an essential host factor for PDCoV infection and can serve as a supplementary receptor to facilitate PDCoV infection, which can help us to explore the molecular mechanism of PDCoV infection.