TCR-induced, PKC-θ-mediated NF-κB activation is regulated by a caspase-8-caspase-9-caspase-3 cascade

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Caspase-8 is known to be vital for T-cell receptor (TCR)-mediated NF-κB activation.
• The involvement of other caspases in this signaling pathway remains unclear.

Purpose of the Study:

• To investigate the role of additional caspases beyond caspase-8 in TCR-mediated NF-κB activation.
• To elucidate the specific roles and sequential order of caspases in T-cell activation signaling.

Main Methods:

• Utilized techniques to assess the requirement of caspases in TCR-mediated NF-κB activation.
• Investigated the upstream and downstream relationships between caspase-8, caspase-9, caspase-3, PKC-θ, and Bcl10.

Main Results:

• Demonstrated that caspase-9, in addition to caspase-8, is essential for TCR-mediated NF-κB activation.
• Showed that caspase-8 acts upstream of caspase-9 in the T-cell activation cascade.
• Identified that caspase-9 activation leads to PKC-θ activation, Bcl10 phosphorylation, and NF-κB activation in a caspase-3-dependent manner.
• Observed that Bcl10 phosphorylation is uncoupled from NF-κB activation and appears to limit its activity.

Conclusions:

• TCR ligation triggers a caspase cascade (caspase-8, -9, -3) crucial for initiating a PKC-θ-dependent pathway for NF-κB activation.
• The study reveals a PKC-θ-independent mechanism for Bcl10 phosphorylation that serves to limit NF-κB activity.