A Non-canonical PDK1-RSK Signal Diminishes Pro-caspase-8-Mediated Necroptosis Blockade

Mol Cell. 2020 Oct 15;80(2):296-310.e6. doi: 10.1016/j.molcel.2020.09.004. Epub 2020 Sep 25.

Abstract

Necroptosis induction in vitro often requires caspase-8 (Casp8) inhibition by zVAD because pro-Casp8 cleaves RIP1 to disintegrate the necrosome. It has been unclear how the Casp8 blockade of necroptosis is eliminated naturally. Here, we show that pro-Casp8 within the necrosome can be inactivated by phosphorylation at Thr265 (pC8T265). pC8T265 occurs in vitro in various necroptotic cells and in the cecum of TNF-treated mice. p90 RSK is the kinase of pro-Casp8. It is activated by a mechanism that does not need ERK but PDK1, which is recruited to the RIP1-RIP3-MLKL-containing necrosome. Phosphorylation of pro-Casp8 at Thr265 can substitute for zVAD to permit necroptosis in vitro. pC8T265 mimic T265E knockin mice are embryonic lethal due to unconstrained necroptosis, and the pharmaceutical inhibition of RSK-mediated pC8T265 diminishes TNF-induced cecum damage and lethality in mice by halting necroptosis. Thus, phosphorylation of pro-Casp8 at Thr265 by RSK is an intrinsic mechanism for passing the Casp8 checkpoint of necroptosis.

Keywords: PDK1; TNF; caspase-8; necroptosis; necrosome; p90 RSK; phosphorylation; zVAD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Phosphoinositide-Dependent Protein Kinases / metabolism*
  • Animals
  • Caspase 8 / metabolism*
  • Cecum / injuries
  • Cecum / pathology
  • Cell Line
  • Embryo, Mammalian / metabolism
  • Embryonic Development / drug effects
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Humans
  • Mice, Inbred C57BL
  • Mutation / genetics
  • Necroptosis* / drug effects
  • Organ Specificity
  • Phosphorylation / drug effects
  • Phosphothreonine / metabolism
  • Protein Kinases / metabolism
  • Ribosomal Protein S6 Kinases, 90-kDa / antagonists & inhibitors
  • Ribosomal Protein S6 Kinases, 90-kDa / metabolism*
  • Signal Transduction* / drug effects
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Tumor Necrosis Factor-alpha
  • Phosphothreonine
  • MLKL protein, mouse
  • Protein Kinases
  • 3-Phosphoinositide-Dependent Protein Kinases
  • Pdpk1 protein, mouse
  • Ribosomal Protein S6 Kinases, 90-kDa
  • Extracellular Signal-Regulated MAP Kinases
  • Caspase 8