Journal of Applied Physiology Watch the video to learn how APS reaches out to developing nations.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
 QUICK SEARCH:   [advanced]


     


J Appl Physiol (September 20, 2007). doi:10.1152/japplphysiol.00736.2007
This Article
Right arrow Full Text (PDF) Free
Right arrow All Versions of this Article:
104/1/27    most recent
00736.2007v1
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Dreyer, H. C.
Right arrow Articles by Rasmussen, B. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Dreyer, H. C.
Right arrow Articles by Rasmussen, B. B.
Submitted on July 9, 2007
Accepted on September 20, 2007

Chronic paraplegia-induced muscle atrophy downregulates the mTOR/S6K1 signaling pathway

Hans C. Dreyer1, Erin L. Glynn2, Heidi L. Lujan3, Christopher S. Fry2, Stephen E. DiCarlo3, and Blake B. Rasmussen4*

1 Physical Therapy, University of Texas Medical Branch, Galveston, Texas, United States
2 Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas, United States
3 Physiology, Wayne State University School of Medicine, Detroit, Michigan, United States
4 Dept. of Physical Therapy, University of Texas Medical Branch, Galveston, Texas, United States

* To whom correspondence should be addressed. E-mail: blrasmus{at}utmb.edu.

Ribosomal S6 kinase 1 (S6K1) is a downstream component of the mammalian target of rapamycin (mTOR) signaling pathway and plays a regulatory role in translation initiation, protein synthesis, and muscle hypertrophy. AMP-activated protein kinase (AMPK) is a cellular energy sensor, a negative regulator of mTOR, and an inhibitor of protein synthesis. The purpose of this study was to determine if the hypertrophy/cell growth-associated mTOR pathway was downregulated during muscle atrophy associated with chronic paraplegia. Soleus muscle was collected from male Sprague-Dawley rats 10 weeks following complete T4-5 spinal cord transection (Paraplegic) and from sham operated (Control) rats. We utilized immunoprecipitation and Western blotting techniques to measure upstream (AMPK, Akt/PKB) and downstream components of the mTOR signaling pathway (mTOR, S6K1, SKAR, 4EBP1 and eIF4G). Paraplegia was associated with significant soleus muscle atrophy (114±8mg vs. 240±13mg, P<0.05). There was a reduction in phosphorylation of mTOR, S6K1, and eIF4G (P<0.05) with no change in Akt/PKB or 4EBP1 (P>0.05). Total protein abundance of mTOR, S6K1, eIF2alpha and Akt/PKB was decreased, and increased for SKAR (P<0.05) while 4EBP1 and eIF4G did not change (P>0.05). S6K1 activity was significantly reduced in the Paraplegic group (P<0.05), however AMPK{alpha}2 activity was not altered (3.5±0.4 vs. 3.7±0.5 pmol·mg-1·min-1, Control vs. Paraplegic rats). We conclude that paraplegia induced muscle atrophy in rats is associated with a general downregulation of the mTOR signaling pathway. Therefore, in addition to upregulation of atrophy signaling during muscle wasting, downregulation of muscle cell growth/hypertrophy-associated signaling appears to be an important component of long-term muscle loss.




This article has been cited by other articles:


Home page
J. Appl. Physiol.Home page
M. J. Drummond, H. C. Dreyer, C. S. Fry, E. L. Glynn, and B. B. Rasmussen
Nutritional and contractile regulation of human skeletal muscle protein synthesis and mTORC1 signaling
J Appl Physiol, April 1, 2009; 106(4): 1374 - 1384.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Physiol. Endocrinol. Metab.Home page
H. S. Hundal and P. M. Taylor
Amino acid transceptors: gate keepers of nutrient exchange and regulators of nutrient signaling
Am J Physiol Endocrinol Metab, April 1, 2009; 296(4): E603 - E613.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Physiol. Endocrinol. Metab.Home page
S. Welle, K. Burgess, and S. Mehta
Stimulation of skeletal muscle myofibrillar protein synthesis, p70 S6 kinase phosphorylation, and ribosomal protein S6 phosphorylation by inhibition of myostatin in mature mice
Am J Physiol Endocrinol Metab, March 1, 2009; 296(3): E567 - E572.
[Abstract] [Full Text] [PDF]




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Visit Other APS Journals Online
Copyright © 1948 by the American Physiological Society.