Presented by Dr. Rayavarapu in partial fulfillment of the requirements for a PhD degree, George Washington University, Washington, DC.
Activation of the Ubiquitin Proteasome Pathway in a Mouse Model of Inflammatory Myopathy: A Potential Therapeutic Target
Article first published online: 27 NOV 2013
Copyright © 2013 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 65, Issue 12, pages 3248–3258, December 2013
How to Cite
Rayavarapu, S., Coley, W., Van der Meulen, J. H., Cakir, E., Tappeta, K., Kinder, T. B., Dillingham, B. C., Brown, K. J., Hathout, Y. and Nagaraju, K. (2013), Activation of the Ubiquitin Proteasome Pathway in a Mouse Model of Inflammatory Myopathy: A Potential Therapeutic Target. Arthritis & Rheumatism, 65: 3248–3258. doi: 10.1002/art.38180
- Issue published online: 27 NOV 2013
- Article first published online: 27 NOV 2013
- Accepted manuscript online: 10 SEP 2013 03:35PM EST
- Manuscript Accepted: 27 AUG 2013
- Manuscript Received: 7 JAN 2013
- NIH (Intellectual and Developmental Disabilities Research Center [IDDRC]). Grant Number: P30-HD-40677
- National Center for Medical Rehabilitation Research/National Institute of Neurological Disorders and Stroke core. Grant Number: 2R24-HD-050846-06
- IDDRC core grant. Grant Number: 5P30-HD-040677-10
- National Center for Research Resources [George Washington University–Children's National Medical Center, Clinical and Translational Science Institute]. Grant Number: UL1-RR-031988
- Association Francaise Contre les Myopathies (Pre-Doctoral Fellowship)
- NIH. Grant Numbers: R01-AR-050478, 5U54-HD-053177, K26-OD-011171
- Muscular Dystrophy Association
- US Department of Defense. Grant Number: W81XWH-05-1-0616
Myositis is characterized by severe muscle weakness. We and others have previously shown that endoplasmic reticulum (ER) stress plays a role in the pathogenesis of myositis. The present study was undertaken to identify perturbed pathways and assess their contribution to muscle disease in a mouse myositis model.
Stable isotope labeling with amino acids in cell culture (SILAC) was used to identify alterations in the skeletal muscle proteome of myositic mice in vivo. Differentially altered protein levels identified in the initial comparisons were validated using a liquid chromatography tandem mass spectrometry spike-in strategy and further confirmed by immunoblotting. In addition, we evaluated the effect of a proteasome inhibitor, bortezomib, on the disease phenotype, using well-standardized functional, histologic, and biochemical assessments.
With the SILAC technique we identified significant alterations in levels of proteins belonging to the ER stress response, ubiquitin proteasome pathway (UPP), oxidative phosphorylation, glycolysis, cytoskeleton, and muscle contractile apparatus categories. We validated the myositis-related changes in the UPP and demonstrated a significant increase in the ubiquitination of muscle proteins as well as a specific increase in ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL-1) in myositis, but not in muscle affected by other dystrophies or normal muscle. Inhibition of the UPP with bortezomib significantly improved muscle function and also significantly reduced tumor necrosis factor α expression in the skeletal muscle of mice with myositis.
Our findings indicate that ER stress activates downstream UPPs and contributes to muscle degeneration and that UCHL-1 is a potential biomarker for disease progression. UPP inhibition offers a potential therapeutic strategy for myositis.