Characterization of TSSK6 Activating Co‐chaperone (TSACC) in Skeletal Muscle

Abstract

Skeletal muscle atrophy is a physiological condition that is caused by a variety of conditions, including immobilization, denervation, spinal cord injury and aging and results in decreased muscle size and strength. To better characterize the molecular genetic events of neurogenic atrophy, a previous study isolated gastrocnemius muscle from mice following 3 days and 14 days of sciatic nerve denervation. The gene expression profile in the denervated muscle tissue was then analyzed by microarray and compared to control muscle tissue to identify novel neurogenic atrophy‐induced genes. The microarray data revealed for the first time that TSSK6 Activating Co‐chaperone (TSACC) is expressed in skeletal muscle and is significantly induced in response to denervation. To confirm that TSACC is expressed in muscle, the predicted TSACC cDNA was cloned from cultured muscle cells, as was a novel TSACC splice variant that contains an additional exon. Quantitative PCR (qPCR) was then used to assess TSACC expression levels of the full‐length and novel splice variant in proliferating and differentiated muscle cells. The results demonstrate that full‐length TSACC expression levels are relatively low in proliferating myoblasts but show significantly elevated expression in differentiated myotubes, whereas the novel splice variant is expressed relatively evenly in proliferating and differentiated muscle cells. In addition, characterization of the transcriptional regulation of TSACC was assessed by fusing fragments of the proximal promoter located immediately upstream of the start of transcription with a reporter gene. The reporter plasmids were then transfected into C2C12 mouse muscle cells in combination with myogenic regulatory factor (MRF) expression plasmids, which resulted in significant activation of reporter gene activity. Interestingly, there are several predicted E‐box elements in the proximal promoter region of the TSACC gene further suggesting that TSACC may be regulated by muscle‐specific transcription factors. Finally, to determine a possible role for TSACC in skeletal muscle, sub‐cellular localization was determined by fusing the cDNA with GFP and expressing the fusion protein in cultured muscle cells. The discovery that TSACC is induced in response to neurogenic atrophy helps further our understanding of the molecular genetic events of muscle atrophy and may eventually lead to the identification of new therapeutic targets for the treatment of muscle atrophy.Support or Funding InformationThe work was support by University of North Florida Transformational Learning Opportunity grants and a University of North Florida Foundation Board Grant to D.W.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.