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Activation of death-inducing signaling complex (DISC) by pro-apoptotic C-terminal fragment of RIP

J W Kim1, E J Choi, C O Joe

  • 1Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea.

Oncogene
|September 26, 2000
PubMed

Insights

Tumor necrosis factor receptor 1 (TNFR1) signaling activates NF-kappaB and apoptosis. Caspase-8 cleavage of receptor interacting protein (RIP) during apoptosis reduces RIP

Area of Science:

  • Cellular signaling pathways
  • Apoptosis and cell death mechanisms
  • Molecular biology

Background:

  • Tumor necrosis factor receptor 1 (TNFR1) mediates opposing signals for NF-kappaB activation and apoptosis.
  • Receptor interacting protein (RIP) is a key cytosolic protein associated with TNFR1 signaling.
  • Caspase-8 plays a critical role in initiating apoptosis.

Purpose of the Study:

  • To investigate the role of receptor interacting protein (RIP) cleavage by caspase-8 in TNF-induced apoptosis and NF-kappaB activation.
  • To elucidate the mechanism by which the C-terminal fragment of RIP influences TNFR1 signaling.
  • To understand how RIP cleavage impacts the balance between apoptosis and NF-kappaB activation.

Main Methods:

  • Site-directed mutagenesis to create an uncleavable RIP mutant (RIPD324A).
  • Ectopic expression of RIP fragments in cells.
  • Analysis of NF-kappaB activation using reporter assays.
  • Assessment of apoptosis through cell death assays.
  • Co-immunoprecipitation to study protein-protein interactions.

Main Results:

  • Proteolytic cleavage of RIP by caspase-8 during TNF-induced apoptosis abrogates RIP's stimulatory role on NF-kappaB activation.
  • An uncleavable RIP mutant (RIPD324A) exhibited reduced apoptosis but enhanced NF-kappaB activation compared to wild-type RIP.
  • The pro-apoptotic C-terminal fragment of RIP inhibited TNF-induced NF-kappaB activation by suppressing IKKbeta activity.
  • The C-terminal fragment of RIP enhanced TNFR1 association with TRADD and FADD, promoting caspase-8 activation and apoptosis.

Conclusions:

  • The C-terminal fragment of RIP, generated by caspase-8, activates the death-inducing signaling complex (DISC).
  • This fragment attenuates NF-kappaB activation, thereby amplifying caspase-8 activation and downstream apoptotic events.
  • RIP cleavage by caspase-8 represents a critical regulatory point controlling the switch between survival (NF-kappaB) and death (apoptosis) signaling pathways initiated by TNFR1.

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