IKAP is a scaffold protein of the IkappaB kinase complex

Nature. 1998 Sep 17;395(6699):292-6. doi: 10.1038/26254.


The transcription factor NF-kappaB coordinates the activation of numerous genes in response to pathogens and pro-inflammatory cytokines, and is, therefore, vital in the development of acute and chronic inflammatory diseases. NF-kappaB is activated by phsophorylation of its inhibitory subunit, IkappaB-alpha, on serine residues 32 and 36 by cytokine-activated IKB kinases (IKKs); this phosphorylation precedes rapid degradation of IkappaB. IKK-alpha and IKK-beta isozymes are found in large complexes of relative molecular mass 700,000-900,000 (M(r) 70K-90K), but little is known about other components that organize and regulate these complexes. IKK-alpha was independently discovered as a NF-kappaB-inducing kinase (NIK)-associated protein in a yeast two-hybrid screen, and IKK-beta was also identified by homology screening. It is, however, unknown whether NIK is part of the IKK complex. Here we isolate large, interleukin-1-inducible IKK complexes that contain NIK, IKK-alpha, IKK-beta, IkappaB-alpha, NF-kappaB/RelA and a protein of M(r) 150K. This latter component is a new protein, termed IKK-complex-associated protein (IKAP), which can bind NIK and IKKs and assemble them into an active kinase complex. We show that IKAP is a scaffold protein and a regulator for three different kinases involved in pro-inflammatory cytokine signalling.

MeSH terms

  • Amino Acid Sequence
  • Carrier Proteins / genetics
  • Carrier Proteins / isolation & purification
  • Carrier Proteins / metabolism*
  • Cell Line, Transformed
  • Cloning, Molecular
  • Enzyme Induction
  • I-kappa B Kinase
  • Interleukin-1 / metabolism
  • Molecular Sequence Data
  • Nuclear Matrix / enzymology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / chemistry*
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Transcriptional Elongation Factors
  • Tumor Necrosis Factor-alpha / metabolism


  • Carrier Proteins
  • Elp1 protein, human
  • Interleukin-1
  • Transcriptional Elongation Factors
  • Tumor Necrosis Factor-alpha
  • Protein-Serine-Threonine Kinases
  • I-kappa B Kinase

Associated data

  • GENBANK/AF044195