title: Intra- and interdimeric caspase-8 self-cleavage controls strength and timing of CD95-induced apoptosis.
abstract: Apoptosis in response to the ligand CD95L (also known as Fas ligand) is initiated by caspase-8, which is activated by dimerization and self-cleavage at death-inducing signaling complexes (DISCs). Previous work indicated that the degree of substrate cleavage by caspase-8 determines whether a cell dies or survives in response to a death stimulus. To determine how a death ligand stimulus is effectively translated into caspase-8 activity, we assessed this activity over time in single cells with compartmentalized probes that are cleaved by caspase-8 and used multiscale modeling to simultaneously describe single-cell and population data with an ensemble of single-cell models. We derived and experimentally validated a minimal model in which cleavage of caspase-8 in the enzymatic domain occurs in an interdimeric manner through interaction between DISCs, whereas prodomain cleavage sites are cleaved in an intradimeric manner within DISCs. Modeling indicated that sustained membrane-bound caspase-8 activity is followed by transient cytosolic activity, which can be interpreted as a molecular timer mechanism reflected by a limited lifetime of active caspase-8. The activation of caspase-8 by combined intra- and interdimeric cleavage ensures weak signaling at low concentrations of CD95L and strongly accelerated activation at higher ligand concentrations, thereby contributing to precise control of apoptosis.
authors.affiliation: 1Department for Bioinformatics and Functional Genomics, Division of Theoretical Bioinformatics, German Cancer Research Center (DKFZ), Institute for Pharmacy and Molecular Biotechnology (IPMB) and BioQuant, Heidelberg University, Heidelberg 69120, Germany.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Kallenberger
authors.forename: Joël
authors.initials: J
authors.lastname: Beaudouin
authors.forename: Juliane
authors.initials: J
authors.lastname: Claus
authors.forename: Carmen
authors.initials: C
authors.lastname: Fischer
authors.forename: Peter K
authors.initials: PK
authors.lastname: Sorger
authors.forename: Stefan
authors.initials: S
authors.lastname: Legewie
authors.forename: Roland
authors.initials: R
authors.lastname: Eils
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D053181:Caspase 8 / Q000737:chemistry / Q000378:metabolism*; D003198:Computer Simulation; D003600:Cytosol / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D019281:Dimerization; D053222:Fas Ligand Protein / Q000378:metabolism*; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008954:Models, Biological; D015398:Signal Transduction / Q000502:physiology*; D059010:Single-Cell Analysis
chemical_list: D053418:Death Domain Receptor Signaling Adaptor Proteins; D053222:Fas Ligand Protein; D053181:Caspase 8