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- Title
Molecular basis of death effector domain chain assembly and its role in caspase-8 activation.
- Authors
Singh, Nitu; Hassan, Ali; Bose, Kakoli
- Abstract
Assembly of a death-inducing signaling complex is a key event in the extrinsic apoptotic pathway, enabling activation of the caspase cascade and subsequent cell death. However, the molecular events governing DISC assembly have remained largely elusive because of the lack of information on mechanism and specificity regulating the death effector domain (DED)-DED interaction network. Using molecular modeling, mutagenesis, and biochemical and ex vivo experiments, we identified the precise binding interface and hot spots crucial for intermolecular DED chain assembly. Mutation of key interface residues (Leu42/Phe45) in procaspase-8 DED-A completely abrogated DED chain formation in HEK293 cells and prevented its association with FADD. A significant 2.6-3.6-fold reduction in procaspase-8 activation was observed in functional cell-death assays after substitution of the interfacial residues. Based on our results we propose a new model for DISC formation that refines the current understanding of the activation mechanism. Upon stimulation, FADD self-associates weakly via reciprocal interaction between helices a1/a4 and a2/a3 of the DED to form an oligomeric signaling platform that provides a stage for the initial recruitment of procaspase-8 through direct interaction with a1/a4 of DED-A, followed by sequential interaction mediated by helices a2/a5 of DED-B, to form the procaspase-8 DED chain that is crucial for its activation and subsequent cell death.--Singh, N., Hassan, A., Bose, K. Molecular basis of death effector domain chain assembly and its role in caspase-8 activation.
- Subjects
CASPASES; APOPTOSIS; CELLULAR signal transduction; MOLECULAR models; LEUCINE; AMINO acid residues
- Publication
FASEB Journal, 2016, Vol 30, Issue 1, p186
- ISSN
0892-6638
- Publication type
Article
- DOI
10.1096/fj.15-272997