Functional characterization of a BCL10 isoform in the rainbow trout Oncorhynchus mykiss

• The complexes formed by BCL10, MALT1 and CARMA proteins are key regulators of NF-κB activation.
• We report the functional characterization of tBCL10, a BCL10 isoform from the trout Oncorhynchus mykiss.
• tBCL10 can functionally replace the human protein.
• The rainbow trout Oncorhynchus mykiss can serve as a model organism to study this pathway.

The complexes formed by BCL10, MALT1 and members of the family of CARMA proteins have recently been the focus of much attention because they represent a key mechanism for regulating activation of the transcription factor NF-κB. Here, we report the functional characterization of a novel isoform of BCL10 in the trout Oncorhynchus mykiss, which we named tBCL10. tBCL10 dimerizes, binds to components of the CBM complex and forms cytoplasmic filaments. Functionally, tBCL10 activates NF-κB transcription factor and is inhibited by the deubiquitinating enzyme A20. Finally, depletion experiments indicate that tBCL10 can functionally replace the human protein. This work demonstrates the evolutionary conservation of the mechanism of NF-κB activation through the CBM complex, and indicates that the rainbow trout O. mykiss can serve as a model organism to study this pathway.