title: Regulation of Ikappa B kinase (IKK)gamma /NEMO function by IKKbeta -mediated phosphorylation.
abstract: The IkappaB kinase (IKK) complex includes the catalytic components IKKalpha and IKKbeta in addition to the scaffold protein IKKgamma/NEMO. Increases in the activity of the IKK complex result in the phosphorylation and subsequent degradation of IkappaB and the activation of the NF-kappaB pathway. Recent data indicate that the constitutive activation of the NF-kappaB pathway by the human T-cell lymphotrophic virus, type I, Tax protein leads to enhanced phosphorylation of IKKgamma/NEMO by IKKbeta. To address further the significance of IKKbeta-mediated phosphorylation of IKKgamma/NEMO, we determined the sites in IKKgamma/NEMO that were phosphorylated by IKKbeta, and we assayed whether IKKgamma/NEMO phosphorylation was involved in modulating IKKbeta activity. IKKgamma/NEMO is rapidly phosphorylated following treatment of cells with stimuli such as tumor necrosis factor-alpha and interleukin-1 that activate the NF-kappaB pathway. By using both in vitro and in vivo assays, IKKbeta was found to phosphorylate IKKgamma/NEMO predominantly in its carboxyl terminus on serine residue 369 in addition to sites in the central region of this protein. Surprisingly, mutation of these carboxyl-terminal serine residues increased the ability of IKKgamma/NEMO to stimulate IKKbeta kinase activity. These results indicate that the differential phosphorylation of IKKgamma/NEMO by IKKbeta and perhaps other kinases may be important in regulating IKK activity.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, Harold Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Shashi
authors.initials: S
authors.lastname: Prajapati
authors.forename: Richard B
authors.initials: RB
authors.lastname: Gaynor
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: D010750:Phosphoproteins; D011994:Recombinant Proteins; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse