SIGNALING PATHWAYS OF PROTEIN SYNTHESIS REGULATION IN RAT POSTURAL MUSCLE DURING RECOVERY AFTER HINDLIMB UNLOADING
Time course changes in the rate of protein synthesis and molecular mechanisms of translation regulation were investigated in rat soleus muscle during recovery (reloading) from mechanical unloading (hindlimb suspension). An increased rate of protein synthesis in soleus was observed after one and 3 days of recovery compared to control (p < 0.05). A rise in protein synthesis was also detected after 7 days of reloading compared to suspended rats (p < 0.05). Using Western blotting, we detected an increase in ribosomal kinase p70 (p70s6k) and initiation factor 4E binding protein (4E-BP1) phosphorylation after 3-day reloading vs. control (p< 0.05) and a decrease in the phosphorylation of these proteins after 7 days of recovery relative to control (p < 0.05). In addition, 3-day reloading induced a significant increase in phosphorylated glycogen synthase kinase (GSK-3β) vs. control (p < 0.05). The content of translation initiation factor 2B (eIF2B-ε) was significantly higher after 3 days of reloading vs. control (p < 0.05), whereas the content of phospho-eIF2B-ε was significantly increased after 24 hours of reloading compared with control (p < 0.05). Thus, we obtained new data about the state of intracellular anabolic signaling pathways in rat soleus during recovery after disuse-induced atrophy.