| Titre : | Muscle aging and calcium-dependent proteolytic system |
| contenu dans : | |
| Auteurs : | Congrès international de myologie 2008 (International Congress of Myology 2008; 26-30 mai 2008; Marseille, France) ; Brule C ; Dargelos E ; Cottin P ; Poussard S |
| Type de document : | Article |
| Année de publication : | 2008 |
| Pages : | p. 515 |
| Langues: | Anglais |
| Résumé : | The calcium-dependent proteolytic system is composed of cysteine proteases named calpains. They are ubiquitous or tissue-specific enzymes and the two best characterised isoforms are the ubiquitously expressed µ- and m-calpains. Besides its regulation by calcium, calpain activity is tightly regulated by calpastatin (which is the specific endogenous inhibitor), binding to phospholipids, autoproteolysis and phosphorylation. Calpains are responsible for limited proteolytic events. Among the multitude of substrates identified so far are cytoskeletal and membrane proteins, enzymes and transcription factors. Calpains are involved in a large number of physiological processes such as muscle growth and differentiation, and pathological conditions such as muscular dystrophies. Aging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern. Although sarcopenia is well documented, the molecular mechanisms of this condition still remains unclear. The aim of this study was to determine if the proteolytic system could be involved in the phenotype associated with sarcopenia. Calpains and calpastatin levels, subcellular distributions and activities were compared between muscles from young (3 months) and old (24 months) rats. While the subcellular localisation of calpains did not change between young and old rat samples, their enzymatic activity significantly increase with age. In the meantime, calpastatin specific activity and protein level decreased in old samples. Altogether, our data showed an overall increase in calpain activity associated with muscle aging. These findings suggest that the calcium-dependent proteolytic system is indeed involved in sarcopenia. |
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