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|Title:||Co-operative and Hierarchical Binding of c-FLIP and Caspase-8: A Unified Model Defines How c-FLIP Isoforms Differentially Control Cell Fate|
|Authors:||Hughes, Michelle A.|
Powley, Ian R.
Schwabe, John W. R.
|Publisher:||Elsevier (Cell Press)|
|Citation:||Molecular Cell, 2016, 61 (6), pp. 834-849|
|Abstract:||The death-inducing signaling complex (DISC) initiates death receptor-induced apoptosis. DISC assembly and activation are controlled by c-FLIP isoforms, which function as pro-apoptotic (c-FLIPL only) or anti-apoptotic (c-FLIPL/c-FLIPS) regulators of procaspase-8 activation. Current models assume that c-FLIP directly competes with procaspase-8 for recruitment to FADD. Using a functional reconstituted DISC, structure-guided mutagenesis, and quantitative LC-MS/MS, we show that c-FLIPL/S binding to the DISC is instead a co-operative procaspase-8-dependent process. FADD initially recruits procaspase-8, which in turn recruits and heterodimerizes with c-FLIPL/S via a hierarchical binding mechanism. Procaspase-8 activation is regulated by the ratio of unbound c-FLIPL/S to procaspase-8, which determines composition of the procaspase-8:c-FLIPL/S heterodimer. Thus, procaspase-8:c-FLIPL exhibits localized enzymatic activity and is preferentially an activator, promoting DED-mediated procaspase-8 oligomer assembly, whereas procaspase-8:c-FLIPS lacks activity and potently blocks procaspase-8 activation. This co-operative hierarchical binding model explains the dual role of c-FLIPL and crucially defines how c-FLIP isoforms differentially control cell fate.|
|Rights:||Copyright © the authors, 2016. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.|
|Appears in Collections:||Published Articles, Dept. of Molecular and Cell Biology|
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