Defining the combinatorial space of PKC::CARD-CC signal transduction nodes

Area of Science:

• Cellular signaling and molecular biology
• Immunology and cancer research

Background:

• Signal transduction often follows a bow-tie topology, with central signaling nodes like CARD-CC/BCL10/MALT1 (CBM) complexes integrating multiple pathways.
• CBM complexes are activated by protein kinase C (PKC)-mediated phosphorylation of CARD-CC proteins, but specific PKC::CARD-CC relationships are largely unknown.
• Four CARD-CC proteins (CARD9, CARD10, CARD11, CARD14) and nine PKC isozymes exist, presenting a vast combinatorial space for signal integration.

Purpose of the Study:

• To systematically explore the functional combinatorial space of all potential PKC::CARD-CC interactions.
• To identify specific PKC isozymes that activate different CARD-CC family members.
• To investigate the role of mixed CARD-CC protein complexes and phosphorylation sites in regulating CBM signaling.

Main Methods:

• Utilized CARD10-deficient human embryonic kidney 293T cells for pairwise co-transfection experiments.
• Co-transfected all four CARD-CC family members with all nine activated PKC isozymes.
• Assessed functional interactions by measuring NF-κB-dependent reporter gene expression.

Main Results:

• Identified 21 functional PKC::CARD-CC combinations, significantly expanding the known interaction landscape.
• Found CARD10 responsive to most PKCs, CARD14 primarily activated by PKCδ, and CARD11 activation profiles similar to CARD9.
• Discovered that mixed CARD-CC complexes influence PKC response profiles and identified distinct phosphorylation site usage for CARD9 and CARD14 activation.

Conclusions:

• This study elucidates the combinatorial complexity of PKC::CARD-CC signal transduction nodes.
• The findings provide a comprehensive map of PKC::CARD-CC interactions, essential for understanding CBM signaling regulation.
• These data will facilitate future research into inflammatory and oncogenic pathways regulated by CBM complexes.