Insights into the role and regulation of TCTP in skeletal muscle
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Craig A. Goodman1,2,3, Allison M. Coenen1, John W. Frey1, Jae-Sung You1, Robert G. Barker4, Barnaby P. Frankish4, Robyn M. Murphy4, Troy A. Hornberger1
1Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
2Centre for Chronic Disease Prevention and Management, College of Health and Biomedicine, Victoria University, Melbourne, Victoria, 8001, Australia
3Institute for Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, 8001, Australia
4Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, 3086, Australia
Craig A. Goodman, email: [email protected]
Keywords: muscle hypertrophy, muscle atrophy, cancer, duchenne muscular dystrophy, proteostasis
Received: June 16, 2016 Accepted: September 28, 2016 Published: November 01, 2016
The translationally controlled tumor protein (TCTP) is upregulated in a range of cancer cell types, in part, by the activation of the mechanistic target of rapamycin (mTOR). Recently, TCTP has also been proposed to act as an indirect activator of mTOR. While it is known that mTOR plays a major role in the regulation of skeletal muscle mass, very little is known about the role and regulation of TCTP in this post-mitotic tissue. This study shows that muscle TCTP and mTOR signaling are upregulated in a range of mouse models (mdx mouse, mechanical load-induced hypertrophy, and denervation- and immobilization-induced atrophy). Furthermore, the increase in TCTP observed in the hypertrophic and atrophic conditions occurred, in part, via a rapamycin-sensitive mTOR-dependent mechanism. However, the overexpression of TCTP was not sufficient to activate mTOR signaling (or increase protein synthesis) and is thus unlikely to take part in a recently proposed positive feedback loop with mTOR. Nonetheless, TCTP overexpression was sufficient to induce muscle fiber hypertrophy. Finally, TCTP overexpression inhibited the promoter activity of the muscle-specific ubiquitin proteasome E3-ligase, MuRF1, suggesting that TCTP may play a role in inhibiting protein degradation. These findings provide novel data on the role and regulation of TCTP in skeletal muscle in vivo.
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