title: Role of an acidic compartment in tumor-necrosis-factor-alpha-induced production of ceramide, activation of caspase-3 and apoptosis.
abstract: Tumor necrosis factor-alpha (TNF-alpha) apoptosis by recruiting a complex of cytosolic proteins at its plasma membrane receptor. Among them is caspase-8, an interleukin-1beta-converting enzyme (ICE)-like protease that initiates an amplified protease cascade to activate the cell-death machinery. The latter comprises at least caspase-3 and caspase-7, which execute cell death by cleaving numerous protein substrates, including poly(ADP-ribose) polymerase. In addition, TNF-alpha stimulates the production of ceramide, which also activates the death machinery. Whether the signaling pathways elicited by caspase-8 and ceramide proceed independently or intersect at a specific subcellular site is unknown. Using the lysosomotropic agent NH4Cl and the vesicularization inhibitor brefeldin A, we show here the convergence of TNF-alpha-induced death signaling on an acidic, subcellular compartment reminiscent of lysosomes. This compartment generates at least two signaling pathways that account for the caspase-3 activation and apoptosis induced by TNF-alpha, one involving ceramide and caspase-unrelated adapter molecules and another involving yet unknown lysosomal mediators. The apoptosis inhibitor Bcl-2 specifically acts on the ceramide-activated pathway to block caspase-3 activation and apoptosis. The latter result explains why Bcl-2 only partially blocks TNF-alpha-induced apoptosis.
authors.affiliation: Institute of Biochemistry, University of Fribourg, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Monney
authors.forename: R
authors.initials: R
authors.lastname: Olivier
authors.forename: I
authors.initials: I
authors.lastname: Otter
authors.forename: B
authors.initials: B
authors.lastname: Jansen
authors.forename: G G
authors.initials: GG
authors.lastname: Poirier
authors.forename: C
authors.initials: C
authors.lastname: Borner
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D020126:Brefeldin A; D053148:Caspase 3; D020169:Caspases; D002451:Cell Compartmentation / Q000187:drug effects*; D003517:Cyclopentanes / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D011992:Endosomes / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D003517:Cyclopentanes; D015853:Cysteine Proteinase Inhibitors; C064769:N-acetylsphingosine; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; C103712:benzyloxycarbonyl-valyl-alanyl-aspartyl-fluoromethane; D000643:Ammonium Chloride; D020126:Brefeldin A; D011065:Poly(ADP-ribose) Polymerases; D013108:Sphingomyelin Phosphodiesterase; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D013110:Sphingosine