Fig. 4. The catalytically active IKK complex is required to suppress accumulation of NIK.

(A) WT, IKKα^KO, NEMO^KO, and IKKβ^KO MEFs were either untreated (−) or incubated with LIGHT for 12 hours (+) before cell lysates were analyzed by Western blotting with antibodies against the indicated proteins. (B) The indicated MEF cell lines were either untreated (−) or were stimulated with LIGHT (L) or anti-LTβR antibody (Ab) for 12 hours before cell lysates were analyzed by Western blotting with antibodies against the indicated proteins. Active IKK was detected with an antibody specific for phosphorylated IKKα/β (p-IKKα/β). (C) WT, IKKβ^KO, and IKKβ^KO MEFs retrovirally transduced with LZRS or LZRS expressing either IKKβ^WT or a catalytically inactive mutant IKKβ (IKKβ^K44M) were either untreated (−) or incubated with LIGHT for 12 hours (+) before cell lysates were analyzed by Western blotting with antibodies against the indicated proteins. Western blots are representative of four independent experiments.