Dominant-negative FADD inhibits TNFR60-, Fas/Apo1- and TRAIL-R/Apo2-mediated cell death but not gene induction.
Fas/Apo1 and other cytotoxic receptors of the tumor necrosis factor receptor (TNFR) family contain a cytoplasmic death domain (DD) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] that activates the apoptotic process by interacting with the DD-containing adaptor proteins TNFR-associated DD protein (TRADD) [12] [13] and Fas-associated DD protein (FADD/MORT1) [14] [15], leading to the activation of cysteine proteases of the caspase family [16]. Stimulation of Fas/Apo1 leads to the formation of a receptor-bound death-inducing signaling complex (DISC), consisting of FADD and two different forms of caspase-8 [17] [18] [19]. Transient expression of a dominant-negative mutant of FADD impairs TNFR60-mediated and Fas/Apo1-mediated apoptosis [13] [20], but has no effect on TNF-related apoptosis-inducing ligand (TRAIL/Apo2L)-induced cell death [7] [8] [9] [10] [21]. To study the function of FADD in DD-receptor signaling in more detail, we established HeLa cells that stably expressed a green fluorescent protein (GFP)-tagged dominant-negative mutant of FADD, GFP-DeltaFADD. Interestingly, expression of this mutant inhibited cell death induced by TNFR60, Fas/Apo1 and TRAIL-R/Apo2. In addition, GFP-DeltaFADD did not interfere with TNF-mediated gene induction or with activation of NF-kappaB or Jun N-terminal kinase (JNK), demonstrating that FADD is part of the TNFR60-initiated apoptotic pathway but does not play a role in TNFR60-mediated gene induction. Fas/Apo1-mediated activation of JNK was unaffected by the expression of GFP-DeltaFADD, suggesting that in Fas/Apo1 signaling the apoptotic pathway and the activation of JNK diverge at a level proximal to the receptor, upstream of or parallel to FADD.
Wajant
H
H
Institute of Cell Biology and Immunology, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany. harald.wajant@po.uni-stuttgart.de
Johannes
F J
FJ
Haas
E
E
Siemienski
K
K
Schwenzer
R
R
Schubert
G
G
Weiss
T
T
Grell
M
M
Scheurich
P
P
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D019014:fas Receptor / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; C505639:TNFRSF10B protein, human; D019014:fas Receptor