The Mechanism Research Of UBXN1Rugulating NF-κB Signaling

NF-κBsignaling is important in a variety of cellular processes includingcell growth, immune responses and cytokine induction. Hyperactivaction of NF-κB is closely related to diverse types of cancer, autoimmune diseases andchronic inflammatory syndromes.Currently, the NF-κB activation process hasbeen extensively studied, but how NF-κB isinactivated is still unclear. Therefore,to explore the inactivation mechanism of NF-κB signaling has become a newdirection of research on related diseases treatment.ubiquitination is important in NF-κB signaling. Ubituitin binding proteinsare a kind of important ubiquitination regulatory protein. UBA-containingproteins are the largest group of ubiquitination regulatory proteins.Whereas howTNFα-triggered signaling isfinely tuned by UBA-containing proteins is not fullyelucidated.So we developed a siRNA library to target all UBA-containing genesin human genome and performed high-throughput siRNA screen to find newregulators of NF-κB signaling. We identified a novelubiquitination regulatoryprotein UBXN1as a negative regulator of NF-κB signaling.UBXN1was first identified as an ubiquitin binding protein (Y33K). Recentresearch found that UBXN1was strongly induced and bound to MAVS,interfered with intracellularMAVS oligomerization, and disrupted theMAVS/TRAF3/TRAF6signalosomefollowing viral infectionserving as a brake toprevent excessive RLRsignaling. However, thefunction and mechanism ofUBXN1inTNFα-triggeredNF-κB signaling islargely unknown.Here, we find that depletionof UBXN1enhances TNFα-inducedluciferaseactivityand promptsTNFα-inducedIκBαdegradation, whereas overexpression ofUBXN1has the opposite effects. Furthermore, UBXN1strongly inhibitsTRADD-, TRAF2-, RIPK1-but not TAK1-, IKKβss/ee-, p65-induced NF-κBactivation, which indicates that UBXN1may function at TAK1upstream level.Moreover, we demonstrate that UBXN1interacts with E3ligase cIAPs by Co-IP assay. Consistently, overexpression of UBXN1interferes with TNFR1complexassembly and RIPK1ubiquitination by competing for E3ligases cIAPs fromTRAF2. These findings reveala probable role of UBXN1in the modulationofexcessive immune response triggered byTNFα.