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

Dae Seok Kim, Byeong Gu Han, Kang Seo Park, Byung Il Lee, Soo Youl Kim, Chang Dae Bae

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Transglutaminase 2 (TGase2) is a calcium-dependent, cross-linking enzyme that catalyzes iso-peptide bond formation between peptide-bound lysine and glutamine residues. TGase 2 can activate NF-κB through the polymerization-mediated depletion of I-κBα without IKK activation. This NF-κB activation mechanism is associated with drug resistance in cancer cells. However, the polymers cannot be detected in cells, while TGase 2 over-expression depletes free I-κBα, which raises the question of how the polymerized I-κBα can be metabolized in cells. Among proteasome, lysosome and calpain systems, calpain inhibition was found to effectively increase the accumulation of I-κBα polymers in MCF7 cells transfected with TGase 2, and induced high levels of I-κBα polymers as well in MDA-MB-231 breast cancer cells that naturally express a high level of TGase 2. Inhibition of calpain also boosted the level of I-κBα polymers in HEK-293 cells in case of TGase 2 transfection either with I-κBα or I-κBα mutant (S32A, S36A). Interestingly, the combined inhibition of calpain and the proteasome resulted in an increased accumulation of both I-κBα polymers and I-κBα, concurrent with an inhibition of NF-κB activity in MDA-MB-231 cells. This suggests that μ-calpain proteasome-dependent I-κBα polymer degradation may contribute to cancer progression through constitutive NF-κB activation.

Original languageEnglish (US)
Pages (from-to)300-306
Number of pages7
JournalBiochemical and Biophysical Research Communications
Issue number2
StatePublished - Aug 20 2010
Externally publishedYes


  • I-κBα
  • NF-κB
  • Proteasome
  • Transglutaminase 2
  • μ-Calpain

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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