title: Differential localization of autolyzed calpains 1 and 2 in slow and fast skeletal muscles in the early phase of atrophy.
abstract: Calpains have been proposed to be involved in the cytoskeletal remodeling and wasting of skeletal muscle. However, limited data are available about the specific involvement of each calpain in the early stages of muscle atrophy. The aims of this study were to determine whether calpains 1 and 2 are autolyzed after a short period of muscle disuse, and, if so, where in the myofibers the autolyzed products are localized. In the rat soleus muscle, 5 days of immobilization increased autolyzed calpain 1 in the particulate and not the soluble fraction. Conversely, autolyzed calpain 2 was not found in the particulate fraction, whereas it was increased in the soluble fraction after immobilization. In the less atrophied plantaris muscle, no difference was noted between the control and immobilized groups whatever the fraction or calpain. Other proteolytic pathways were also investigated. The ubiquitin-proteasome pathway was activated in both skeletal muscles, and caspase 3 was activated only in the soleus muscle. Taken together, our data suggest that calpains 1 and 2 are involved in atrophy development in slow type muscle exclusively and that they have different regulation and protein targets. Moreover, the activation of proteolytic pathways appears to differ in slow and fast muscles, and the proteolytic mechanisms involved in fast-type muscle atrophy remain unclear.
authors.affiliation: INSERM, ERI 25, Hôpitol Arnaud de Villneuve, 34295 Montpellier Cedex 5, France. mvermaelen@netcourrier.com
authors.forename: Marianne
authors.initials: M
authors.lastname: Vermaelen
authors.forename: Pascal
authors.initials: P
authors.lastname: Sirvent
authors.forename: Fabrice
authors.initials: F
authors.lastname: Raynaud
authors.forename: Catherine
authors.initials: C
authors.lastname: Astier
authors.forename: Jacques
authors.initials: J
authors.lastname: Mercier
authors.forename: Alain
authors.initials: A
authors.lastname: Lacampagne
authors.forename: Olivier
authors.initials: O
authors.lastname: Cazorla
mesh_terms: D000818:Animals; D001329:Autolysis; D002154:Calpain / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D004195:Disease Models, Animal; D004789:Enzyme Activation; D019417:Hindlimb Suspension; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology; D018485:Muscle Fibers, Skeletal / Q000201:enzymology* / Q000473:pathology; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000473:pathology; D009133:Muscular Atrophy / Q000201:enzymology* / Q000473:pathology; D009210:Myofibrils / Q000201:enzymology; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D025801:Ubiquitin; D002154:Calpain; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex