Systems-based Analysis of RIG-I-dependent Signaling Identifies KHSRP as an Inhibitor of RIG-I Receptor Activation

摘要

Retinoic acid inducible gene-I (RIG-I) receptor recognizes 5′-triphosphorylated RNA and triggers a signaling cascade that results in the induction of type-I IFN-dependent responses. Its precise regulation represents a pivotal balance between antiviral defenses and autoimmunity. To elucidate cellular cofactors that regulate RIG-I signaling, we performed two global RNAi analyses to identify both positive and negative regulatory nodes operating on the signaling pathway during virus infection. These factors were integrated with experimentally and computationally derived interactome data to build a RIG-I protein interaction network. Our analysis revealed diverse cellular processes, including the unfolded protein response, WNT signaling, and RNA metabolism, as critical cellular components governing innate responses to non-self RNA species. Importantly, we identified K-Homology Splicing Regulatory Protein (KHSRP) as a negative regulator of this pathway. We find that KHSRP associates with the regulatory domain of RIG-I to maintain the receptor in an inactive state and attenuate it’s sensing of viral RNA (vRNA). Consistent with increased RIG-I antiviral signaling in the absence of KHSRP, viral replication is reduced when KHSRP expression is knocked down both in vitro and in vivo. Taken together, these data indicate that KHSRP functions as a checkpoint regulator of the innate immune response to pathogen challenge.