TNF-receptor I defective in internalization allows for cell death through activation of neutral sphingomyelinase.
The cytoplasmic tail of the tumor necrosis factor receptor I (TNF-RI) contains several functionally distinct domains involved in apoptotic signaling. Mutants of TNF-RI carrying deletions of the death domain (DD), internalization domain (TRID), and neutral sphingomyelinase domain (NSD), respectively, retransfected in cells devoid of TNF-RI and TNF-RII, constituted distinct tools to evaluate the specific role of each domain in downstream apoptotic signaling events. Deletion of DD abolishes activation of caspase-3 and -9 and apoptosis following treatment with TNF because of blocked assembly of the DISC. Nevertheless, TNF-RI DeltaTRID, though lacking a DISC, still allows for residual activation of caspase-3 followed by cell death, although caspase-9 activation was not detected. This activity of caspase-3 is probably due to activation of neutral sphingomyelinase (N-SMase). Increased activity of this enzyme was detected in cells expressing TNF-RI DeltaTRID following treatment with TNF, but not in any other cell line investigated. N-SMase is activated by factor associated with N-SMase (FAN). Because TNF-RI DeltaTRID is retained at the cell surface, FAN may interact with the mutated receptor for a prolonged amount of time, thereby overactivating N-SMase. Double deletion of TRID and NSD abolished caspase-3 activation and apoptosis, confirming this hypothesis.
Neumeyer
Jens
J
Institute of Immunology, University Hospital of Schleswig-Holstein Campus Kiel, Michaelisstr. 5, D-24105 Kiel, Germany.
Hallas
Cora
C
Merkel
Oliver
O
Winoto-Morbach
Supandi
S
Jakob
Marten
M
Thon
Lutz
L
Adam
Dieter
D
Schneider-Brachert
Wulf
W
Schütze
Stefan
S
D020816:Amino Acid Motifs; D000818:Animals; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000235:genetics; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics; D053418:Death Domain Receptor Signaling Adaptor Proteins; D004789:Enzyme Activation; D005347:Fibroblasts; D017353:Gene Deletion; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000235:genetics; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002518:Ceramides; D004268:DNA-Binding Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; C486432:Dedd protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; C491112:Nsmaf protein, mouse; D034741:RNA, Small Interfering; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D013108:Sphingomyelin Phosphodiesterase; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases