Integrin β3, a RACK1 interacting protein, is required for porcine reproductive and respiratory syndrome virus infection and NF-κB activation in Marc-145 cells
Porcine reproductive and respiratory syndrome virus (PRRSV) is the pathogen of porcine reproductive and respiratory syndrome (PRRS), which is one of the most economically harmful diseases in modern pig production worldwide. Receptor of activated protein C kinase 1 (RACK1) was previously shown to be indispensable for the PRRSV replication and NF-{kappa}B activation in Marc-145 cells. Here we identified a membrane protein, integrin {beta}3 (ITGB3), as a RACK1-interacting protein. PRRSV infection in Marc-145 cells upregulated the ITGB3 expression. Abrogation of ITGB3 by siRNA knockdown or antibody blocking inhibited PRRSV infection and NF-{kappa}B activation, while on the other hand, overexpression of ITGB3 enhanced PRRSV infection and NF-{kappa}B activation. Furthermore, inhibition of ITGB3 alleviated the cytopathic effects and reduced the TCID50 titer in Marc-145 cells. We also showed that RACK1 and ITGB3 were NF-{kappa}B target genes during PRRSV infection, and that they regulate each other. Our data indicate that ITGB3, presumably as a co-receptor, plays an imperative role for PRRSV infection and NF-{kappa}B activation in Marc-145 cells. PRRSV infection activates a positive feedback loop involving the activation of NF-{kappa}B and upregulation of ITGB3 and RACK1 in Marc-145 cells. The findings would advance our elaborated understanding of the molecular host-pathogen interaction mechanisms underlying PRRSV infection in swine and suggest ITGB3 and NF-{kappa}B signaling pathway as potential therapeutic targets for PRRS control. IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) is one of the pathogens in pig production worldwide. Several cell surface receptors, such as heparan sulphate, sialoadhesin, vimentin and CD163, were identified to be involved in PRRSV infection in porcine alveolar macrophages (PAMs). We identified a cell surface protein, integrin {beta}3 (ITGB3), as an interacting protein with receptor of activated protein C kinase 1 (RACK1) from Marc-145 cells. ITGB3 interacts with RACK1 and facilitates PRRSV infection and NF-{kappa}B activation in Marc-145 cells, presumably as a co-receptor of CD136 or vimentin. Both ITGB3 and RACK1 were NF-{kappa}B target genes, and they regulate each other. The activation of NF-{kappa}B and the transcription of its downstream genes are beneficial for PRRSV infection/replication. The novel findings would advance our elaborated understanding of the molecular host-pathogen interaction mechanisms underlying PRRSV infection in swine and suggest ITGB3-RACK1-NF-{kappa}B axis as a potential therapeutic target for PRRS control.