CSN-associated c-Cbl control alternative NF-κB/RelB activity in Helicobacter pylori infection.

TheThe colonization of the gastric epithelium with Helicobacter pylori elicits a robust nuclear factor kappa-light chain enhancer of activated B cells (NF-κB)-dependent inflammatory response. The bacterial effector molecule adenosine diphosphate-glycero-β-D-manno-heptose (ADP-heptose) triggers both the classical and alternative NF-κB pathways almost simultaneously leading to activation of the transcription factor heterodimers p50/RelA and p52/RelB. Previous studies have demonstrated that the COP9 signalosome complex (CSN) plays an important role in regulating the classical NF-κB pathway through deneddylation of the E3 ligase Skp1-Cullin1-F-Box-β-TRCP (SCFβ-TRCP), while the influence of the CSN on the alternative NF-κB pathway remains unclear. Here, we show that CSN-dependent deneddylation of Cullin-1 controls via the classical NF-κB signaling pathway the upregulation of RelB mRNA and protein expression, enhancing the nuclear translocation of RelB. These findings are supported by the fact that ADP-heptose induces RelB expression in 2D mucosoids derived from 3D organoids from gastric antral glands of the stomach. Blocking neddylation and the activity of SCFβ-TRCP by treatment with the NEDD8-activating enzyme inhibitor MLN4924 prior to H. pylori infection, stabilized IκBα as well as p100 and suppressed RelA and RelB nuclear translocation. Therefore, our data show that CSN-dependent regulation of SCFβ-TRCP controls classical NF-κB signaling and consequently contributes to RelB nuclear translocation and alternative NF-κB activity. For the termination of alternative NF-κB activity, the CSN serves as a hub between constitutively associated c-Cbl and nuclear RelB, allowing c-Cbl-mediated ubiquitinylation of nuclear RelB following H. pylori infection.