Regulation of ubiquitin-proteasome system, caspase enzyme activities, and extracellular proteinases in rat soleus muscle in response to unloading

P Berthon, Stephanie Duguez, F B Favier, A Amirouche, L Feasson, L Vico, C Denis, D Freyssenet

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In the present study, we determined the impact of 5 and 10 days of muscle deconditioning induced by hindlimb suspension (HS) on the ubiquitin-proteasome system of protein degradation and caspase enzyme activities in rat soleus muscles. A second goal was to determine whether activities of matrix metalloproteinase-2/9 (MMP-2/9) and urokinase-type/tissue-type plasminogen activator (PAs) were responsive to HS. As expected, HS led to a pronounced atrophy of soleus muscle. Level of ubiquitinated proteins, chymotrypsin-like activity of 20S proteasome, and Bcl-2-associated gene product-1 protein level were all transitory increased in response to 5 days of HS. These changes may thus potentially account for the decrease in muscle mass observed in response to 5 days of HS. Caspase-3 activity was significantly increased throughout the experimental period, whereas activities of caspase-6, another effector caspase, and caspase-9, the mitochondrial-dependent activator of both caspase-3 and -6, were only increased in response to 10 days of HS. This suggests that caspase-3 may be regulated through mitochondrial-independent and mitochondrial-dependent mechanisms in response to HS. Finally, MMP-2/9 activities remained unchanged, whereas PAs activities were increased after 5 days of HS. Overall, these data suggest that time-dependent regulation of intracellular and extracellular proteinases are important in setting the new phenotype of rat soleus muscle in response to HS.
Original languageEnglish
Pages (from-to)625-633
JournalPflügers Archiv European Journal of Physiology
Issue number4
Early online date3 Mar 2007
Publication statusE-pub ahead of print - 3 Mar 2007



  • BAG-1 . Chaperone . Hindlimb suspension . Hypokinesia . Muscle atrophy . Proteolysis

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