Two adjacent trimeric Fas ligands are required for Fas signaling and formation of a death-inducing signaling complex.
The membrane-bound form of Fas ligand (FasL) signals apoptosis in target cells through engagement of the death receptor Fas, whereas the proteolytically processed, soluble form of FasL does not induce cell death. However, soluble FasL can be rendered active upon cross-linking. Since the minimal extent of oligomerization of FasL that exerts cytotoxicity is unknown, we engineered hexameric proteins containing two trimers of FasL within the same molecule. This was achieved by fusing FasL to the Fc portion of immunoglobulin G1 or to the collagen domain of ACRP30/adiponectin. Trimeric FasL and hexameric FasL both bound to Fas, but only the hexameric forms were highly cytotoxic and competent to signal apoptosis via formation of a death-inducing signaling complex. Three sequential early events in Fas-mediated apoptosis could be dissected, namely, receptor binding, receptor activation, and recruitment of intracellular signaling molecules, each of which occurred independently of the subsequent one. These results demonstrate that the limited oligomerization of FasL, and most likely of some other tumor necrosis factor family ligands such as CD40L, is required for triggering of the signaling pathways.
Holler
Nils
N
Institute of Biochemistry, BIL Biomedical Research Center, University of Lausanne, Switzerland.
Tardivel
Aubry
A
Kovacsovics-Bankowski
Magdalena
M
Hertig
Sylvie
S
Gaide
Olivier
O
Martinon
Fabio
F
Tinel
Antoine
A
Deperthes
David
D
Calderara
Silvio
S
Schulthess
Therese
T
Engel
Jürgen
J
Schneider
Pascal
P
Tschopp
Jürg
J
D048868:Adaptor Proteins, Signal Transducing; D052242:Adiponectin; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001402:B-Lymphocytes / Q000378:metabolism; D023201:CD40 Ligand / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins; D019281:Dimerization; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D019014:fas Receptor / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D052242:Adiponectin; D002352:Carrier Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; C505533:FADD protein, human; C505661:FASLG protein, human; C505534:Fadd protein, mouse; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; C505658:Fasl protein, mouse; D007074:Immunoglobulin G; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D011506:Proteins; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; D019014:fas Receptor; D023201:CD40 Ligand; D003094:Collagen; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases