I-κBα depletion by transglutaminase 2 and μ-calpain occurs in parallel with the ubiquitin-proteasome pathway

► TGase 2 induces NF-κB activation via I-κBα polymerization. ► TGase 2-induced I-κBα polymers do not accumulate in cancer cells. ► TGase 2-mediated I-κBα polymer deposition is detected by calpain inhibition. ► Calpain inhibition reduces TGase 2-induced NF-κB activity.