Nipah virus matrix protein promotes NF-κB activation by targeting multiple signaling modulators.

The Nipah virus (NiV) matrix (M) protein, essential for viral assembly, has been increasingly recognized for its potential immunomodulatory functions. However, its role in modulating the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway-a central regulator of inflammation and innate immunity-remains poorly defined. Here, we demonstrate that NiV-M significantly promotes activation of the classical NF-κB pathway. Our data showed that NiV-M interacts with multiple cellular signaling molecules of the NF-κB pathway, including tripartite motif containing 25 (TRIM25), inhibitor of nuclear factor kappa-B kinase subunit alpha (IKKα), nuclear factor of kappa light polypeptide gene enhancer in B-cell inhibitor alpha (IκBα), and the p65 subunit of NF-κB. Further analyses revealed that NiV-M enhanced the E3 ubiquitin ligase activity of TRIM25, facilitating its interaction with both retinoic acid-inducible gene I (RIG-I) and TNF receptor-associated factor 2 (TRAF2), thereby promoting K63-linked ubiquitination of RIG-I and TRAF2. Moreover, NiV-M strengthened the interaction between IKKα and IKKβ, leading to enhanced IKK complex activity and accelerated degradation of IκBα. In addition, NiV-M promoted phosphorylation and nuclear translocation of p65, thereby amplifying NF-κB-driven gene expression. In summary, our results demonstrate a multifaceted strategy by which NiV-M regulates the NF-κB pathway, a mechanism that may contribute to NiV pathogenesis via inflammatory dysregulation. These findings suggest potential therapeutic approaches for alleviating symptoms associated with immunopathology of NiV by targeting virus-host interactions.IMPORTANCEThis study reveals a previously unknown role of the Nipah virus matrix (M) protein in driving excessive inflammation, a key factor in the virus's high mortality. We discovered that the M protein acts as a master switch, hijacking a central human immune pathway (NF-κB) at multiple points to trigger a "cytokine storm." This explains how the virus causes severe tissue damage and organ failure in infected individuals. By identifying the specific human proteins targeted by the M protein, our work establishes that this viral component functions not only in viral assembly but also in the dysregulation of host inflammatory responses, thereby providing a new perspective on its potential contribution to severe NiV-associated disease. These findings open new avenues for treating NiV infections by developing drugs that target these interactions, potentially controlling the devastating inflammation rather than just the virus itself.