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Updated: Jul 5, 2026

Evaluation of Caspase Activation to Assess Innate Immune Cell Death

Evaluation of Caspase Activation to Assess Innate Immune Cell Death

Published on: January 20, 2023

TNF-alpha induces two distinct caspase-8 activation pathways.

Lai Wang¹, Fenghe Du, Xiaodong Wang

¹Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.

|May 20, 2008

Summary

Tumor Necrosis Factor-alpha (TNF-alpha) triggers apoptosis through two distinct pathways. These pathways involve either cycloheximide or Smac mimetic, differentially regulating caspase-8 activation via cIAP1/2 and c-FLIP.

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Area of Science:

Cellular biology
Molecular mechanisms of cell death
Immunology

Background:

Tumor Necrosis Factor-alpha (TNF-alpha) is a key cytokine in inflammatory responses.
The switch from inflammation to apoptosis is a critical cellular process.
Caspase-8 is a central mediator in TNF-alpha-induced apoptosis.

Purpose of the Study:

To elucidate the distinct molecular mechanisms by which TNF-alpha induces apoptosis.
To investigate the roles of cycloheximide and Smac mimetic in regulating caspase-8 activation.
To differentiate the regulatory functions of c-FLIP and cIAP1/2 in TNF-alpha signaling.

Main Methods:

Utilized cycloheximide, a protein synthesis inhibitor.
Employed Smac mimetic, a small molecule mimic of Smac/Diablo.
Investigated the involvement of caspase-8, c-FLIP, cIAP1/2, RIPK1, and CYLD.

Main Results:

Cycloheximide promotes caspase-8 activation by degrading c-FLIP.
Smac mimetic triggers apoptosis by degrading cIAP1/2, releasing RIPK1 to form a caspase-8 activating complex.
RIPK1 is essential for Smac mimetic-induced but not cycloheximide-induced caspase-8 activation.
Smac mimetic-induced caspase-8 activation is independent of endogenous c-FLIP.

Conclusions:

TNF-alpha induces apoptosis via at least two distinct caspase-8 activation pathways.
These pathways are differentially regulated by cellular inhibitors cIAP1/2 and c-FLIP.
Understanding these pathways offers insights into targeted therapeutic strategies for diseases involving TNF-alpha signaling.