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Ca(2+)-dependent proteinases (calpains) and muscle cell differentiation
P Cottin1, J J Brustis, S Poussard
1I.S.T.A.B., Laboratoire de Biochimie et Technologie des Aliments, Université Bordeaux I, Talence, France.
Biochimica Et Biophysica Acta
|September 8, 1994
Summary
Calpain II appears early during muscle cell differentiation, while calpain I emerges later. Hormones and growth factors modulate calpain levels, suggesting transcriptional regulation, not housekeeping roles, in myogenesis.
Area of Science:
- Biochemistry
- Cell Biology
- Developmental Biology
Background:
- Calpains are calcium-dependent proteases involved in various cellular processes.
- Myogenesis, the process of muscle cell differentiation, involves complex regulatory mechanisms.
- The specific roles of different calpain isoforms during myogenesis are not fully understood.
Purpose of the Study:
- To investigate the temporal expression of calpain I and calpain II during embryonic myoblast differentiation in vitro.
- To analyze the influence of insulin, corticosterone, IGF-1, and TGF-beta on calpain and calpastatin levels during myogenesis.
- To elucidate the regulatory mechanisms governing calpain expression during muscle development.
Main Methods:
- Immunodetection assays using specific antibodies.
- Enzymic activity measurements.
- Analysis of total calpain mRNA expression.
- In vitro culture of embryonic myoblasts.
Main Results:
- Calpain II was detected from the onset of myoblast fusion, increasing until day 6 and then plateauing.
- Calpain II mRNA expression mirrored its activity profile, indicating transcriptional regulation.
- Calpain I and calpastatin were only detected on day 6 of culture.
- Exogenous factors significantly modulated calpain-calpastatin levels, affecting protein synthesis and degradation rates.
Conclusions:
- Calpain II is involved in events following myoblast fusion, not directly correlated with the fusion rate.
- Calpain I may play a role in the later stages of muscle cell differentiation.
- Calpain expression during myogenesis is transcriptionally regulated and influenced by exogenous factors, suggesting specialized functions beyond housekeeping roles.