CARMA1 is required for Akt-mediated NF-kappaB activation in T cells

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• The NF-kappaB pathway is crucial for immune responses and is activated by diverse receptor systems.
• CARMA1, Bcl10, and MALT1 proteins are known mediators linking T-cell receptor (TCR) and CD28 signaling to NF-kappaB.
• Previous work identified a role for the serine/threonine kinase Akt in CD28-mediated NF-kappaB induction.

Purpose of the Study:

• To elucidate the role of Akt in NF-kappaB induction through TCR and CD28 signaling.
• To investigate the interaction between Akt and the CARMA/Bcl10/MALT1 complex.
• To determine the mechanisms by which Akt influences T-cell activation.

Main Methods:

• Utilized a CARMA1-deficient T-cell line to assess the requirement of the CARMA complex.
• Employed a novel selective inhibitor of Akt to evaluate its modulatory role.
• Performed co-immunoprecipitation and Western blotting to examine protein interactions and phosphorylation.

Main Results:

• The CARMA complex is essential for Akt-mediated NF-kappaB induction, particularly when combined with protein kinase C activation.
• Akt was confirmed to play a modulatory role in NF-kappaB induction triggered by TCR and CD28.
• Evidence was found for a physical and functional interaction between Akt and CARMA, along with Akt-dependent phosphorylation of Bcl10.

Conclusions:

• In T cells, Akt impacts NF-kappaB signaling through at least two distinct mechanisms.
• Akt's interaction with CARMA and its phosphorylation of Bcl10 are critical steps in T-cell activation pathways.
• These findings provide new insights into the convergence of receptor signaling onto the NF-kappaB transcription factor family.