Phosphorylation of IkappaB-alpha inhibits its cleavage by caspase CPP32 in vitro.
IkappaB proteins function as direct regulators of Rel/NF-kappaB transcription complexes. We show that the cell-death protease CPP32 (caspase-3) in vitro specifically cleaved chicken and human IkappaB-alpha at a conserved Asp-Ser sequence. This cleavage site appears to be identical to the site at which chicken IkappaB-alpha is cleaved in vivo in temperature-sensitive v-Rel-transformed chicken spleen cells undergoing apoptosis. Other caspases, namely interleukin-1beta-converting enzyme (caspase-1) and Ich-1 (caspase-2), did not cleave IkappaB-alpha. CPP32 also cleaved mammalian IkappaB-beta in vitro at the analogous Asp-Ser sequence. Cleavage of IkappaB-alpha by CPP32 was blocked by serine phosphorylation of IkappaB-alpha. Cleavage of IkappaB-alpha by a CPP32- like protease could generate a constitutive inhibitor of Rel transcription complexes. This report provides evidence for a direct biochemical interaction between the NF-kappaB signaling pathway and a cell-death protease signaling pathway.
Barkett
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Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
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Horvitz
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Gilmore
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D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases; D002460:Cell Line; D002645:Chickens; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism*; D006801:Humans; D020672:I-kappa B Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D009857:Oncogenes / Q000187:drug effects; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects
D004268:DNA-Binding Proteins; D004792:Enzyme Precursors; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha; D001224:Aspartic Acid; D012694:Serine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases