NEMO ensures signaling specificity of the pleiotropic IKKβ by directing its kinase activity toward IκBα.
Besides activating NFκB by phosphorylating IκBs, IKKα/IKKβ kinases are also involved in regulating metabolic insulin signaling, the mTOR pathway, Wnt signaling, and autophagy. How IKKβ enzymatic activity is targeted to stimulus-specific substrates has remained unclear. We show here that NEMO, known to be essential for IKKβ activation by inflammatory stimuli, is also a specificity factor that directs IKKβ activity toward IκBα. Physical interaction and functional competition studies with mutant NEMO and IκB proteins indicate that NEMO functions as a scaffold to recruit IκBα to IKKβ. Interestingly, expression of NEMO mutants that allow for IKKβ activation by the cytokine IL-1, but fail to recruit IκBs, results in hyperphosphorylation of alternative IKKβ substrates. Furthermore IKK's function in autophagy, which is independent of NFκB, is significantly enhanced without NEMO as IκB scaffold. Our work establishes a role for scaffolds such as NEMO in determining stimulus-specific signal transduction via the pleiotropic signaling hub IKK.
Signaling Systems Laboratory, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0375, USA.
Bärbel
B
Schröfelbauer
Smarajit
S
Polley
Marcelo
M
Behar
Gourisankar
G
Ghosh
Alexander
A
Hoffmann
D016475:3T3 Cells; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D057809:HEK293 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D007375:Interleukin-1 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D015398:Signal Transduction
D020672:I-kappa B Proteins; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; C514981:NEMO protein, mouse; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D000072000:NF-KappaB Inhibitor alpha; D051550:I-kappa B Kinase