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<jats:p>Background/Aims: The purpose of the study was to assess the amount of rRNA and phosphorylation status of the key markers of mTORC1-dependent (70s6k, 4E-BP1) and mTORC1-independent (GSK-3β, AMPK) signaling pathways controlling protein synthesis in rat soleus during early stages of mechanical unloading (hindlimb suspension (HS) for 1-, 3- and 7 days). Methods: The content of the key signaling molecules of various anabolic signaling pathways was determined by Western-blotting. The amount of 28S rRNA was evaluated by RT-PCR. The rate of protein synthesis was assessed using in-vivo SUnSET technique. Results: HS for 3 and 7 days induced a significant (p&lt;0.05) decrease in the rate of global protein synthesis in soleus muscle in comparison with control. HS within 24 hours resulted in a significant (p&lt;0.05) decrease in p-4E-BP1 content, p-AMPK content and increase in p-p70s6k content in rat soleus muscle. Following three days of HS the content of p-AKT was decreased (p&lt;0.05). After 7 days of HS the phosphorylation level of AKT and GSK-3beta was significantly reduced (p&lt;0.05) compared to control. We also observed a significant decrease in the amount of 28S rRNA in rat soleus following 1, 3 and 7 days of HS. Conclusion: Taken together, the results of our study suggest that a decline in the global rate of protein synthesis in rat soleus during early stages of simulated microgravity is associated with impaired ribosome biogenesis as well as reduced activity of mTORC1-independent signaling pathways.</jats:p>

Original publication

DOI

10.1159/000447808

Type

Journal article

Journal

Cellular Physiology and Biochemistry

Publisher

S. Karger AG

Publication Date

2016

Volume

39

Pages

1011 - 1020