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Measuring Composition of CD95 Death-Inducing Signaling Complex and Processing of Procaspase-8 in this Complex
07:17

Measuring Composition of CD95 Death-Inducing Signaling Complex and Processing of Procaspase-8 in this Complex

Published on: August 2, 2021

Cellular FLICE-inhibitory protein splice variants inhibit different steps of caspase-8 activation at the CD95

A Krueger1, I Schmitz, S Baumann

  • 1Tumor Immunology Program, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.

The Journal of Biological Chemistry
|March 30, 2001
PubMed

Insights

Cellular FLICE-inhibitory proteins (c-FLIP) variants differentially regulate caspase-8 activation in the CD95 death-inducing signaling complex (DISC). c-FLIP(L) allows partial processing, while c-FLIP(S) completely inhibits caspase-8 activation, impacting apoptosis.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Apoptosis Research

Background:

  • CD95 (APO-1/Fas) receptor stimulation initiates apoptosis via the death-inducing signaling complex (DISC).
  • Procaspase-8 activation within the DISC is a critical step in initiating apoptosis.
  • Cellular FLICE-inhibitory proteins (c-FLIP) are key regulators that can inhibit this apoptotic pathway.

Purpose of the Study:

  • To investigate the differential mechanisms by which c-FLIP long (c-FLIP(L)) and c-FLIP short (c-FLIP(S)) splice variants inhibit procaspase-8 activation at the DISC.
  • To elucidate the specific cleavage steps of procaspase-8 affected by each c-FLIP variant.

Main Methods:

  • Stable transfection of BJAB cells with c-FLIP(S) and c-FLIP(L) variants.
  • Analysis of procaspase-8 processing and activation within the DISC upon CD95 stimulation.
  • Utilized various c-FLIP mutants, including p43-c-FLIP(L) and a nonprocessable c-FLIP(L) mutant, to dissect functional roles.

Main Results:

  • Both c-FLIP(S) and c-FLIP(L) inhibit procaspase-8 activation at the DISC, but at distinct stages.
  • c-FLIP(L) permits the initial cleavage of procaspase-8, generating the p10 subunit, indicating partial processing.
  • c-FLIP(S) completely blocks procaspase-8 cleavage, preventing even partial activation, while p43-c-FLIP(L) also inhibits cleavage.

Conclusions:

  • c-FLIP proteins differentially regulate caspase-8 activation at the DISC, impacting the apoptotic cascade.
  • c-FLIP(L) induces a conformation allowing partial procaspase-8 processing, whereas c-FLIP(S) prevents partial activation entirely.
  • These findings highlight distinct inhibitory mechanisms of c-FLIP splice variants on DISC-mediated apoptosis.

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