Activity of caspase-8 Determines Plasticity Between Cell Death Pathways

Nature. 2019 Nov;575(7784):679-682. doi: 10.1038/s41586-019-1752-8. Epub 2019 Nov 13.

Abstract

Caspase-8 is a protease with both pro-death and pro-survival functions: it mediates apoptosis induced by death receptors such as TNFR11, and suppresses necroptosis mediated by the kinase RIPK3 and the pseudokinase MLKL2-4. Mice that lack caspase-8 display MLKL-dependent embryonic lethality4, as do mice that express catalytically inactive CASP8(C362A)5. Casp8C362A/C362AMlkl-/- mice die during the perinatal period5, whereas Casp8-/-Mlkl-/- mice are viable4, which indicates that inactive caspase-8 also has a pro-death scaffolding function. Here we show that mutant CASP8(C362A) induces the formation of ASC (also known as PYCARD) specks, and caspase-1-dependent cleavage of GSDMD and caspases 3 and 7 in MLKL-deficient mouse intestines around embryonic day 18. Caspase-1 and its adaptor ASC contributed to the perinatal lethal phenotype because a number of Casp8C362A/C362AMlkl-/-Casp1-/- and Casp8C362A/C362AMlkl-/-Asc-/- mice survived beyond weaning. Transfection studies suggest that inactive caspase-8 adopts a distinct conformation to active caspase-8, enabling its prodomain to engage ASC. Upregulation of the lipopolysaccharide sensor caspase-11 in the intestines of both Casp8C362A/C362AMlkl-/- and Casp8C362A/C362AMlkl-/-Casp1-/- mice also contributed to lethality because Casp8C362A/C362AMlkl-/-Casp1-/-Casp11-/- (Casp11 is also known as Casp4) neonates survived more often than Casp8C362A/C362AMlkl-/-Casp1-/- neonates. Finally, Casp8C362A/C362ARipk3-/-Casp1-/-Casp11-/- mice survived longer than Casp8C362A/C362AMlkl-/-Casp1-/-Casp11-/- mice, indicating that a necroptosis-independent function of RIPK3 also contributes to lethality. Thus, unanticipated plasticity in death pathways is revealed when caspase-8-dependent apoptosis and MLKL-dependent necroptosis are inhibited.

MeSH terms

  • Animals
  • CARD Signaling Adaptor Proteins / metabolism
  • Caspase 8 / genetics
  • Caspase 8 / metabolism*
  • Cell Death / genetics*
  • Female
  • Gene Expression Regulation
  • HEK293 Cells
  • Humans
  • Intestinal Mucosa / cytology*
  • Intestinal Mucosa / enzymology
  • Kaplan-Meier Estimate
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mutation
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism

Substances

  • CARD Signaling Adaptor Proteins
  • Pycard protein, mouse
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Ripk3 protein, mouse
  • Caspase 8