Enterovirus 71 2C Protein Inhibits TNF-α-Mediated Activation of NF-κB by Suppressing IκB Kinase β Phosphorylation

Enterovirus 71 (EV71), a single, positive-stranded RNA virus, has been regarded as the most important neurotropic enterovirus after the eradication of the poliovirus. EV71 infection can cause hand, foot, and mouth disease or herpangina. Cytokine storm with elevated levels of proinflammatory and inflammatory cytokines, including TNF-alpha, has been proposed to explain the pathogenesis of EV71-induced disease. TNF-alpha-mediated NF-kappa B signaling pathway plays a key role in inflammatory response. We hypothesized that EV71 might also moderate host inflammation by interfering with this pathway. In this study, we tested this hypothesis and identified EV71 2C protein as an antagonist of TNF-alpha-mediated activation of NF-kappa B signaling pathway. Expression of 2C protein significantly reduced TNF-alpha-mediated NF-kappa B activation in 293T cells as measured by gene reporter and gel mobility shift assays. Furthermore, overexpression of TNFR-associated factor 2-, MEK kinase 1-, I kappa B kinase (IKK)alpha-, or IKK beta-induced NF-kappa B activation, but not constitutively active mutant of IKK beta (IKK beta SS/EE)-induced NF-kappa B activation, was inhibited by 2C protein. These data together suggested that the activation of IKK beta is most likely targeted by 2C; this notion was further strengthened by immunoblot detection of IKK beta phosphorylation and I kappa B alpha phosphorylation and degradation. Coimmunoprecipitation and colocalization of 2C and IKK beta expressed in mammalian cells provided compelling evidence that 2C interacts with IKK beta. Collectively, our data indicate that EV71 2C protein inhibits IKK beta activation and thus blocks NF-kappa B activation. The Journal of Immunology, 2011, 187: 2202-2212.