YWHAZ downregulated innate immune responses to RNA viruses by inhibiting the IRF3 signaling pathway

Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta polypeptide (YWHAZ) is a member of the YWHA/14-3-3 family. YWHAZ is highly conserved in mammalian cells and generally mediates signal transduction through direct interactions with target proteins. YWHAZ has been reported as a crucial regulator of tumor immunity, inflammation, and apoptosis pathways. However, the precise role of YWHAZ in regulating host antiviral immune responses is not fully understood. Here, our study revealed that YWHAZ negatively regulated type 1 interferon (type 1 IFN) production in response to RNA viruses. Overexpression of YWHAZ inhibited type 1 IFN production triggered by RNA viruses, whereas knockout of YWHAZ increased type 1 IFN production. Mechanistically, YWHAZ interacted with IRF3 and suppressed the nuclear translocation of IRF3 by directly inhibiting IRF3 phosphorylation-dependent dimerization and disrupting the KPNA3-IRF3 interaction. Our findings demonstrated that YWHAZ played a crucial role in regulating IRF3-mediated type 1 IFN production. IMPORTANCE: The activation of IRF3 induced by RIG-I-like receptors is pivotal for type 1 interferon (IFN) production in antiviral immunity. Virus infection leads to type 1 IFN production through inducing the dimerization and subsequent nuclear translocation of IRF3. Following its activation, IRF3 must be tightly regulated to prevent a dysregulated or excessive immune response. Here, we first found that YWHAZ, a member of the 14-3-3 protein family, is a negative regulator of type 1 IFN production by targeting IRF3 signaling. YWHAZ is bound to IRF3 to inhibit the formation of the TBK1-IRF3 complex, the phosphorylation and dimerization of IRF3, as well as the subsequent nuclear translocation. YWHAZ also impeded the KPNA3-IRF3 interaction by binding to KPNA3, thereby inhibiting IRF3 nuclear translocation. The aa 124-184 in YWHAZ was critical for YWHAZ-mediated suppression of type 1 IFNs. These findings reveal the mechanism by which YWHAZ promotes RNA virus replication, thereby advancing our understanding of how YWHAZ mediates innate immune responses.