title: Tumor necrosis factor induces ceramide oscillations and negatively controls sphingolipid synthases by caspases in apoptotic Kym-1 cells.
abstract: The role, origin, and mode of action of the lipid messenger ceramide in programmed cell death and its linkage to receptor-associated apoptotic signal proteins is still unresolved. We show here in Kym-1 rhabdomyosarcoma cells that tumor necrosis factor (TNF)-induced apoptosis is preceded by a multiphasic increase in intracellular ceramide levels. Distinct enzymes were found to contribute to three waves of ceramide, neutral sphingomyelinase, ceramide synthase, and acid sphingomyelinase, with peak activities at 1-2, 40, and around 200 min, respectively, the latter coinciding with progression to irreversible damage. In parallel with ceramide generation, TNF-mediated inhibition of glucosylceramide and sphingomyelin (SM) synthase prevents the immediate metabolization of this lipid mediator. In the presence of benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-fmk) or benzyloxycarbonyl-Asp-Glu-Val-Asp-chloromethyl ketone (Z-DEVD-cmk), a broad spectrum and a caspase 3-selective inhibitor, respectively, glucosylceramide and SM synthase activity remains unaffected by TNF, and intracellular ceramide accumulation is not observed. Our results show that several lipid enzymes contribute to generation of ceramide in response to TNF and identify glucosylceramide and SM synthase as important regulators of the kinetics and magnitude of intracellular ceramide accumulation. As glucosylceramide and SM synthase activity is caspase-sensitive, our data suggest a novel functional link between caspase(s) and ceramide during apoptotic processes.
authors.affiliation: Institute of Cell Biology and Immunology, University of Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Bourteele
authors.forename: A
authors.initials: A
authors.lastname: Hausser
authors.forename: H
authors.initials: H
authors.lastname: Döppler
authors.forename: J
authors.initials: J
authors.lastname: Horn-Müller
authors.forename: C
authors.initials: C
authors.lastname: Röpke
authors.forename: G
authors.initials: G
authors.lastname: Schwarzmann
authors.forename: K
authors.initials: K
authors.lastname: Pfizenmaier
authors.forename: G
authors.initials: G
authors.lastname: Müller
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000633:toxicity; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism* / Q000633:toxicity; D004789:Enzyme Activation; D005456:Fluorescent Dyes / Q000633:toxicity; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D010088:Oxidoreductases / Q000096:biosynthesis; D010507:Periodicity; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D012208:Rhabdomyosarcoma / Q000378:metabolism*; D015398:Signal Transduction; D013107:Sphingolipids / Q000096:biosynthesis; D013108:Sphingomyelin Phosphodiesterase / Q000096:biosynthesis; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D002518:Ceramides; D005456:Fluorescent Dyes; D013107:Sphingolipids; D014409:Tumor Necrosis Factor-alpha; C037974:N-(7-(4-nitrobenzo-2-oxa-1,3-diazole))-6-aminocaproyl sphingosine; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D011065:Poly(ADP-ribose) Polymerases; D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases; D009327:4-Chloro-7-nitrobenzofurazan