Analysis of the Role of Piezo1 Channels in Mechano-Anabolic Coupling in Rat Soleus Muscle

It is known that mTORC1-dependent pathway is involved in the activation of muscle protein synthesis and hypertrophy in response to mechanical stress. However, mechanosensors that mediate sensing and transmission of mechanical signals to the mTORC1 signaling pathway (mechanotransduction) are not yet identified. Mechanically activated (MA) ion channels are viewed as potential candidates for the role of such sarcolemmal mechanosensors. The aim of our work was to investigate the potential role of MA channels (Piezo1) in the activation of the mTORC1 pathway in the isolated rat soleus muscle in response to mechanical stress. Wistar rats were divided into 3 groups: 1) “Control” (isolated muscles were not exposed to MA channel inhibitor or Piezo1 channel activator); 2) “Gadolinium” (muscles were incubated with MA channel inhibitor, gadolinium chloride); 3) “Yoda” (muscles were incubated with Yoda1, Piezo1 activator). In rats from each group, the soleus from the left limb was incubated in the appropriate solution without mechanical stress in the form of a passive stretching, and the soleus from the right limb was subjected to passive stretching and then incubated in the appropriate solution. Phosphorylation of mTORC1 targets (p70S6K, rpS6, 4E-BP1) in rat soleus was determined by PAGE and immunoblotting. After passive stretching of the isolated soleus muscle there was an increase in phosphorylation of p70S6K, its substrate, rpS6, as well as 4E-BP1, by 38.5%, 168%, and 112%, respectively, compared to the soleus muscle that was not subjected to stretching. Incubation of the muscles with gadolinium completely prevented the activation of mTORC1 markers caused by stretching. Incubation of the soleus muscle in the solution with Yoda1 resulted in a decrease in the mechano-dependent phosphorylation of p70S6K, rpS6, and 4E-BP1 compared to a muscle that was not exposed to Yoda1. Thus, Piezo1 channels do not appear to play a role in the activation of mTORC1 signaling in rat soleus muscle in response to passive stretching.