A death effector domain chain DISC model reveals a crucial role for caspase-8 chain assembly in mediating apoptotic cell death.
Formation of the death-inducing signaling complex (DISC) is a critical step in death receptor-mediated apoptosis, yet the mechanisms underlying assembly of this key multiprotein complex remain unclear. Using quantitative mass spectrometry, we have delineated the stoichiometry of the native TRAIL DISC. While current models suggest that core DISC components are present at a ratio of 1:1, our data indicate that FADD is substoichiometric relative to TRAIL-Rs or DED-only proteins; strikingly, there is up to 9-fold more caspase-8 than FADD in the DISC. Using structural modeling, we propose an alternative DISC model in which procaspase-8 molecules interact sequentially, via their DED domains, to form a caspase-activating chain. Mutating key interacting residues in procaspase-8 DED2 abrogates DED chain formation in cells and disrupts TRAIL/CD95 DISC-mediated procaspase-8 activation in a functional DISC reconstitution model. This provides direct experimental evidence for a DISC model in which DED chain assembly drives caspase-8 dimerization/activation, thereby triggering cell death.
MRC Toxicology Unit, Hodgkin Building, P.O. Box 138, Lancaster Road, Leicester LE1 9HN, UK.
Laura S
LS
Dickens
Robert S
RS
Boyd
Rebekah
R
Jukes-Jones
Michelle A
MA
Hughes
Gemma L
GL
Robinson
Louise
L
Fairall
John W R
JW
Schwabe
Kelvin
K
Cain
Marion
M
Macfarlane
D017209:Apoptosis; D053181:Caspase 8 / Q000378:metabolism*; D045744:Cell Line, Tumor; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D013058:Mass Spectrometry / Q000379:methods; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000737:chemistry; D019014:fas Receptor / Q000737:chemistry
D053418:Death Domain Receptor Signaling Adaptor Proteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D019014:fas Receptor; D053181:Caspase 8