LAUSR

Skeletal muscle unloading results in atrophy. We hypothesized that pannexin 1 ATP-permeable channel (PANX1) is involved in the response of muscle to unloading. We tested this hypothesis by blocking PANX1, which regulates efflux of ATP from the cytoplasm. Rats were divided into six groups (eight rats each): non-treated control for 1 and 3 days of the experiments (1C and 3C, respectively), 1 and 3 days of hindlimb suspension (HS) with placebo (1H and 3H, respectively), and 1 and 3 days of HS with PANX1 inhibitor probenecid (PRB; 1HP and 3HP, respectively). When compared with 3C group there was a significant increase in ATP in soleus muscle of 3H and 3HP groups (32 and 51%, respectively, p < 0.05). When compared with 3H group, 3HP group had: (1) lower mRNA expression of E3 ligases MuRF1 and MAFbx (by 50 and 38% respectively, p < 0.05) and MYOG (by 34%, p < 0.05); (2) higher phosphorylation of p70S6k and p90RSK (by 51 and 35% respectively, p < 0.05); (3) lower levels of phosphorylated eEF2 (by 157%, p < 0.05); (4) higher level of phosphorylated GSK3β (by 189%, p < 0.05). In conclusion, PANX1 ATP-permeable channels are involved in the regulation of muscle atrophic processes by modulating expression of E3 ligases, and protein translation and elongation processes during unloading.