Cellular IAPs inhibit a cryptic CD95-induced cell death by limiting RIP1 kinase recruitment

J Cell Biol. 2009 Dec 28;187(7):1037-54. doi: 10.1083/jcb.200904158.

Abstract

A role for cellular inhibitors of apoptosis (IAPs [cIAPs]) in preventing CD95 death has been suspected but not previously explained mechanistically. In this study, we find that the loss of cIAPs leads to a dramatic sensitization to CD95 ligand (CD95L) killing. Surprisingly, this form of cell death can only be blocked by a combination of RIP1 (receptor-interacting protein 1) kinase and caspase inhibitors. Consistently, we detect a large increase in RIP1 levels in the CD95 death-inducing signaling complex (DISC) and in a secondary cytoplasmic complex (complex II) in the presence of IAP antagonists and loss of RIP1-protected cells from CD95L/IAP antagonist-induced death. Cells resistant to CD95L/IAP antagonist treatment could be sensitized by short hairpin RNA-mediated knockdown of cellular FLICE-inhibitory protein (cFLIP). However, only cFLIP(L) and not cFLIP(S) interfered with RIP1 recruitment to the DISC and complex II and protected cells from death. These results demonstrate a fundamental role for RIP1 in CD95 signaling and provide support for a physiological role of caspase-independent death receptor-mediated cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Chloromethyl Ketones / pharmacology
  • Animals
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis*
  • CASP8 and FADD-Like Apoptosis Regulating Protein / metabolism
  • CASP8 and FADD-Like Apoptosis Regulating Protein / physiology
  • Caspase Inhibitors
  • Cysteine Proteinase Inhibitors / pharmacology
  • Death Domain Receptor Signaling Adaptor Proteins / metabolism
  • Fas Ligand Protein / metabolism
  • GTPase-Activating Proteins / metabolism*
  • Humans
  • Inhibitor of Apoptosis Proteins / metabolism
  • Inhibitor of Apoptosis Proteins / physiology*
  • Mice
  • Nuclear Pore Complex Proteins / metabolism*
  • Protein Isoforms / metabolism
  • RNA-Binding Proteins / metabolism*
  • Signal Transduction
  • fas Receptor / metabolism
  • fas Receptor / physiology*

Substances

  • AGFG1 protein, human
  • Amino Acid Chloromethyl Ketones
  • Apoptosis Regulatory Proteins
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Caspase Inhibitors
  • Cysteine Proteinase Inhibitors
  • Death Domain Receptor Signaling Adaptor Proteins
  • Fas Ligand Protein
  • GTPase-Activating Proteins
  • Inhibitor of Apoptosis Proteins
  • Nuclear Pore Complex Proteins
  • Protein Isoforms
  • RNA-Binding Proteins
  • Ralbp1 protein, mouse
  • benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
  • fas Receptor