IKKβ mediates homeostatic function in inflammation via competitively phosphorylating AMPK and IκBα

Inhibitor of nuclear factor kappa-B kinase subunit beta(IKKβ)is one of important kinases in inflammation to phosphorylate inhibitor of nuclear factor kappa-B(IκBα)and then activate nuclear factor kappa-B(NF-κB).Inhibition of IKKβhas been a therapeutic strategy for inflammatory and autoimmune diseases.Here we report that IKKβis constitutively activated in healthy donors and healthy Ikkβ^(C46A)(cysteine 46 mutated to alanine)knock-in mice although they possess intensive IKKβ-IκBα-NF-κB signaling activation.These indicate that IKKβactivation probably plays homeostatic role instead of causing inflammation.Compared to IkkβWTlittermates,lipopolysaccharides(LPS)could induce high mortality rate in Ikkβ^(C46A) mice which is correlated to breaking the homeostasis by intensively activating p-IκBα-NF-κB signaling and inhibiting phosphorylation of 5’adenosine monophosphate-activated protein kinase(p-AMPK)expression.We then demonstrated that IKKβkinase domain(KD)phosphorylates AMPKa1 via interacting with residues Thr183,Ser184,and Thr388,while IKKβhelix-loop-helix motifs is essential to phosphorylate IκBαaccording to the previous reports.Kinase assay further demonstrated that IKKβsimultaneously catalyzes phosphorylation of AMPK and IκBαto mediate homeostasis.Accordingly,activation of AMPK rather than inhibition of IKKβcould substantially rescue LPS-induced mortality in Ikkβ^(C46A) mice by rebuilding the homeostasis.We conclude that IKKβactivates AMPK to restrict inflammation and IKKβmediates homeostatic function in inflammation via competitively phosphorylating AMPK and IκBα.