Sensing of Lys 63-linked polyubiquitination by NEMO is a key event in NF-kappaB activation [corrected]

Nat Cell Biol. 2006 Apr;8(4):398-406. doi: 10.1038/ncb1384. Epub 2006 Mar 19.

Abstract

The transcription factor NF-kappaB is sequestered in the cytoplasm in a complex with IkappaB. Almost all NF-kappaB activation pathways converge on IkappaB kinase (IKK), which phosphorylates IkappaB resulting in Lys 48-linked polyubiquitination of IkappaB and its degradation. This allows migration of NF-kappaB to the nucleus where it regulates gene expression. IKK has two catalytic subunits, IKKalpha and IKKbeta, and a regulatory subunit, IKKgamma or NEMO. NEMO is essential for NF-kappaB activation, and NEMO dysfunction in humans is the cause of incontinentia pigmenti and hypohidrotic ectodermal dysplasia and immunodeficiency (HED-ID). The recruitment of IKK to occupied cytokine receptors, and its subsequent activation, are dependent on the attachment of Lys 63-linked polyubiquitin chains to signalling intermediates such as receptor-interacting protein (RIP). Here, we show that NEMO binds to Lys 63- but not Lys 48-linked polyubiquitin, and that single point mutations in NEMO that prevent binding to Lys 63-linked polyubiquitin also abrogates the binding of NEMO to RIP in tumour necrosis factor (TNF)-alpha-stimulated cells, the recruitment of IKK to TNF receptor (TNF-R) 1, and the activation of IKK and NF-kappaB. RIP is also destabilized in the absence of NEMO binding and undergoes proteasomal degradation in TNF-alpha-treated cells. These results provide a mechanism for NEMO's critical role in IKK activation, and a key to understanding the link between cytokine-receptor proximal signalling and IKK and NF-kappaB activation.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Biosensing Techniques*
  • Electrophoretic Mobility Shift Assay
  • HeLa Cells
  • Humans
  • I-kappa B Kinase / genetics*
  • I-kappa B Kinase / metabolism
  • Immunoprecipitation
  • Lysine / genetics
  • Lysine / metabolism*
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • Point Mutation
  • Protein-Serine-Threonine Kinases / metabolism
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Receptors, Tumor Necrosis Factor, Type I / metabolism
  • Saccharomyces cerevisiae
  • Signal Transduction
  • Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / metabolism
  • Tumor Necrosis Factor-alpha / pharmacology
  • Two-Hybrid System Techniques
  • Ubiquitin / metabolism*

Substances

  • IKBKG protein, human
  • NF-kappa B
  • Receptors, Tumor Necrosis Factor, Type I
  • Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
  • Tumor Necrosis Factor-alpha
  • Ubiquitin
  • Protein-Serine-Threonine Kinases
  • RIPK1 protein, human
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • I-kappa B Kinase
  • Lysine