Increase in the level of m-calpain correlates with the elevated cleavage of filamin during myogenic differentiation of embryonic muscle cells

Kyu Bong Kwak, Sung Soo Chung, Ok Mae Kim, Man Sik Kang, Doo Bong Ha, Chin Ha Chung

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The activity of Ca2+-activated proteinase requiring millimolar Ca2+ (m-calpain) was found to increase dramatically in cultured chick embryonic myoblasts during the early period of myogenic differentiation. Furthermore, the protein level of m-calpain also markedly increased in parallel with the rise in its activity, and both remained elevated thereafter. On the other hand, the activity level of calpastatin, an endogenous inhibitor of the proteinase, remained similar during the entire period of the culture. In addition, the activity of Ca2+-activated proteinase requiring micromolar Ca2+ (μ-calpain) was not detected in either proliferating or differentiated myoblasts. Thus, the overall capacity of Ca2+-dependent proteolysis is likely to increase in differentiating myoblasts and should be contributed by m-calpain. Filamin (250 kDa), that is known to facilitate actin microfilament assembly and interfere with actin-myosin filament formation, was found to be cleaved in cultured myoblasts to 240 kDa products. This filamin-cleavage occurred in a manner similar to the in vitro cleavage of the cytoskeletal protein by the purified m-calpain. Moreover, the filamin-cleavage was most evident at the period of the cell fusion. Thus, it seems likely that the in vivo cleavage of filamin is mediated by m-calpain. These results suggest that m-calpain may play an important role in cytoskeletal reorganization that is requisite for myoblast fusion.

Original languageEnglish
Pages (from-to)243-249
Number of pages7
JournalBBA - Molecular Cell Research
Issue number3
Publication statusPublished - 1993 Feb 17
Externally publishedYes


  • Calpain
  • Calpastatin
  • Filamin
  • Myoblast fusion

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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