Multiple structural domains within I kappa B alpha are required for its inducible degradation by both cytokines and phosphatase inhibitors.
Activation of the transcription factor NF-kappa B by various cellular stimuli involves phosphorylation and subsequent degradation of its inhibitor I kappa B alpha. Both the cytokine tumor necrosis factor alpha (TNF-alpha) and the phosphatase inhibitor calyculin A have been shown to induce rapid phosphorylation and degradation of I kappa B alpha. In the present study, we demonstrate that TNF-alpha and calyculin A stimulate similar although not identical pattern of I kappa B alpha phosphorylation, as demonstrated by phosphopeptide mapping. Interestingly, phosphorylation of I kappa B alpha induced by both inducers involves serine-32 and serine-36 of I kappa B alpha. Furthermore, TNF-alpha- and calyculin A-induced degradation of I kappa B alpha appears to require the same structural domains within I kappa B alpha. In addition to the N-terminal phosphorylation sites and the C-terminal sequences, each of the five ankyrin-like repeats of I kappa B alpha is critically required for the inducible degradation of this NF-kappa B inhibitor. Together, these studies suggest that degradation of I kappa B alpha by both cytokines and phosphatase inhibitors is regulated by site-specific phosphorylation and requires multiple structural domains.
Good
L F
LF
Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey Medical Center 17033, USA.
Maggirwar
S B
SB
Kealiher
A
A
Uhlik
M
M
Sun
S C
SC
D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000939:Epitopes; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D007700:Kinetics; D008387:Marine Toxins; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D010080:Oxazoles / Q000494:pharmacology*; D010748:Phosphopeptides / Q000737:chemistry / Q000302:isolation & purification; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine; D014162:Transfection; D014357:Trypsin; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D000939:Epitopes; D020672:I-kappa B Proteins; D008387:Marine Toxins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D010080:Oxazoles; D010748:Phosphopeptides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D012694:Serine; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D014357:Trypsin