Sphingomyelinase activates proteolytic I kappa B-alpha degradation in a cell-free system.
Tumor necrosis factor (TNF) is one of the most potent physiological inducers of the nuclear transcription factor kappa B (NF-kappa B). A key event in the activation of NF-kappa B is the rapid release of the inhibitory subunit I kappa B-alpha. Various inhibitors of serine-like proteases are shown to block TNF-mediated NF-kappa B activation as well as the disappearance of I kappa B-alpha immunoreactivity in primary murine T lymphocytes and in various human leukemic cell lines. The protease inhibitors did not block TNF-induced activation of either phosphatidylcholine-specific phospholipase C or acidic sphingomyelinase (SMase), indicating that the putative protease operates rather downstream of TNF signal transduction processes. I kappa B-alpha degradation could be directly induced by addition of sphingomyelinase or synthetic ceramide to a cell-free system, indicating a stringent coupling of SMase to the NF-kappa B activation pathway. SMase-induced I kappa B-alpha degradation was suppressed by the protease inhibitor dichloroisocoumarin. Together, the data suggest that a TNF-responsive sphingomyelinase triggers the rapid degradation of I kappa B-alpha through a serine-like protease, which appears to be crucial to the control of NF-kappa B activation.
Machleidt
T
T
Institut für Mikrobiologie und Hygiene, Technische Universität, München, Germany.
Wiegmann
K
K
Henkel
T
T
Schütze
S
S
Baeuerle
P
P
Krönke
M
M
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002474:Cell-Free System; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D020672:I-kappa B Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D009838:Oligodeoxyribonucleotides; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D009838:Oligodeoxyribonucleotides; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D013108:Sphingomyelin Phosphodiesterase