MK2 Phosphorylates RIPK1 to Prevent TNF-Induced Cell Death

Mol Cell. 2017 Jun 1;66(5):698-710.e5. doi: 10.1016/j.molcel.2017.05.003. Epub 2017 May 11.

Abstract

TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.

Keywords: IAPs; MK2; RIPK1; TNF; caspase-8; cell death; complex-II; cytokine; necroptosis; p38.

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Caspase 8 / metabolism
  • Dose-Response Relationship, Drug
  • Fas-Associated Death Domain Protein / metabolism
  • HT29 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • MAP Kinase Kinase Kinases / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mitogen-Activated Protein Kinase 14 / metabolism
  • Multiprotein Complexes
  • NF-kappa B / metabolism
  • Necrosis
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Interference
  • Receptor-Interacting Protein Serine-Threonine Kinases / genetics
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism*
  • Signal Transduction / drug effects
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • Fadd protein, mouse
  • Fas-Associated Death Domain Protein
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • NF-kappa B
  • Tumor Necrosis Factor-alpha
  • MAP-kinase-activated kinase 2
  • Protein-Serine-Threonine Kinases
  • RIPK1 protein, human
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Ripk1 protein, mouse
  • Mitogen-Activated Protein Kinase 14
  • MAP Kinase Kinase Kinases
  • MAP kinase kinase kinase 7
  • Casp8 protein, mouse
  • Caspase 8