GSK-3β controls NF-kappaB activity via IKKγ/NEMO

The NF-kappa B signaling pathway is central for the innate immune response and its deregulation is found in multiple disorders such as autoimmune, chronic inflammatory and metabolic diseases. IKK gamma/NEMO is essential for NF-kappa B activation and NEMO dysfunction in humans has been linked to so-called progeria syndromes, which are characterized by advanced ageing due to age-dependent inflammatory diseases. It has been suggested that glycogen synthase kinase-3 beta (GSK-3 beta) participates in NF-kappa B regulation but the exact mechanism remained incompletely understood. In this study, we identified NEMO as a GSK-3 beta substrate that is phosphorylated at serine 8, 17, 31 and 43 located within its N-terminal domain. The kinase forms a complex with wild-type NEMO while point mutations of NEMO at the specific serines abrogated GSK-3 beta binding and subsequent phosphorylation of NEMO resulting in its destabilization. However, K63-linked polyubiquitination was augmented in mutated NEMO explaining an increased binding to IKK alpha and IKK beta. Even I kappa B alpha was found degraded. Still, TNF alpha-stimulated NF-kappa B activation was impaired pointing towards an un-controlled signalling process. Our data suggest that GSK-3 beta is critically important for ordered NF-kappa B signalling through modulation of NEMO phosphorylation.