Cryo-EM Structure of Caspase-8 Tandem DED Filament Reveals Assembly and Regulation Mechanisms of the Death-Inducing Signaling Complex

Mol Cell. 2016 Oct 20;64(2):236-250. doi: 10.1016/j.molcel.2016.09.009. Epub 2016 Oct 13.

Abstract

Caspase-8 activation can be triggered by death receptor-mediated formation of the death-inducing signaling complex (DISC) and by the inflammasome adaptor ASC. Caspase-8 assembles with FADD at the DISC and with ASC at the inflammasome through its tandem death effector domain (tDED), which is regulated by the tDED-containing cellular inhibitor cFLIP and the viral inhibitor MC159. Here we present the caspase-8 tDED filament structure determined by cryoelectron microscopy. Extensive assembly interfaces not predicted by the previously proposed linear DED chain model were uncovered, and were further confirmed by structure-based mutagenesis in filament formation in vitro and Fas-induced apoptosis and ASC-mediated caspase-8 recruitment in cells. Structurally, the two DEDs in caspase-8 use quasi-equivalent contacts to enable assembly. Using the tDED filament structure as a template, structural analyses reveal the interaction surfaces between FADD and caspase-8 and the distinct mechanisms of regulation by cFLIP and MC159 through comingling and capping, respectively.

Keywords: DED; DISC; FADD; Fas; MC159; cFLIP; caspase-8; death domain; filament; vFLIP.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Apoptosis / drug effects
  • Binding Sites
  • CARD Signaling Adaptor Proteins
  • CASP8 and FADD-Like Apoptosis Regulating Protein / chemistry*
  • CASP8 and FADD-Like Apoptosis Regulating Protein / genetics
  • CASP8 and FADD-Like Apoptosis Regulating Protein / metabolism
  • Caspase 8 / chemistry*
  • Caspase 8 / genetics
  • Caspase 8 / metabolism
  • Cryoelectron Microscopy
  • Cytoskeletal Proteins / chemistry
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Death Domain Receptor Signaling Adaptor Proteins / chemistry*
  • Death Domain Receptor Signaling Adaptor Proteins / genetics
  • Death Domain Receptor Signaling Adaptor Proteins / metabolism
  • Death Effector Domain
  • Fas-Associated Death Domain Protein / chemistry*
  • Fas-Associated Death Domain Protein / genetics
  • Fas-Associated Death Domain Protein / metabolism
  • Gene Expression
  • Humans
  • Jurkat Cells
  • Plasmids / chemistry
  • Plasmids / metabolism
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transfection
  • Viral Proteins / chemistry*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism
  • fas Receptor / pharmacology

Substances

  • CARD Signaling Adaptor Proteins
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Cytoskeletal Proteins
  • Death Domain Receptor Signaling Adaptor Proteins
  • FADD protein, human
  • FAS protein, human
  • Fas-Associated Death Domain Protein
  • PYCARD protein, human
  • Recombinant Fusion Proteins
  • Viral Proteins
  • fas Receptor
  • viral FLIP protein, Molluscum contagiosum virus
  • CASP8 protein, human
  • Caspase 8