Abstract
Effects of the inhibited phsphorylation of heat shock proteins (HSPs) and ribosomal protein S6 phosphorylated at serine-235/236 (p-S6) on the deafferentation-related atrophy of soleus muscle were studied in rats. Adult male Wistar rats were randomly separated into the control, functionally overloaded (FO), sham-operated, deafferentated (DA), FO+DA, and hindlimb-unloaded (U) group. The tendons of plantaris and gastrocnemius muscles were transected in the FO rats. The dorsal roots of the spinal cord at the L4-5 segmental levels were transected in the DA rats. The rats in U were tail-suspended. The sampling of the soleus muscle was performed 2 weeks after the treatments shown above. The cytoplasmic fraction of the soleus muscle homogenate was used for the quantitative analysis of the expression levels of 72 kDa (HSP72) and 27 kDa proteins (total and phosphorylated at serine-85, HSP27 and p-HSP27), and p-S6. All of theses proteins were down-regulated by U. Although the levels of the expression in these proteins were not affected by FO and sham operation, the levels of p-HSP27 and p-S6 235/236 were decreased in DA and FO+DA groups. It was known that the p-HSP27 and p-S6 play a role in the cytoskeletal organization and the initiation of the global mRNA translation, respectively. Therefore, the results suggested that the inhibition of the phosphorylation of HSP27 and S6 may be one of the major causes for the deafferentation-related soleus muscle atrophy. [Jpn J Physiol 55 Suppl:S117 (2005)]
