Journal
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
Volume 421, Issue 1, Pages 67-76Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2003.10.010
Keywords
aging; muscle atrophy; proteasome; proteasome subunits; sarcopenia; skeletal muscle; PA28; PA700
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Funding
- NATIONAL INSTITUTE ON AGING [K02AG021626, R01AG017768] Funding Source: NIH RePORTER
- NIA NIH HHS [AG21626, AG17768, R01 AG017768, K02 AG021626] Funding Source: Medline
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Myofibrillar protein degradation is mediated through the ubiquitin-proteasome pathway. To investigate if altered proteasome activity plays a role in age-related muscle atrophy, we examined muscle size and proteasome function in young and aged F344BN rats. Significant age-related muscle atrophy was confirmed by the 38% decrease in cross-sectional area of type I fibers in soleus muscle. Determination of proteasome function showed hydrolysis of fluorogenic peptides was equivalent between ages. However, when accounting for the 3-fold increase in content of the 20S catalytic core in aged muscle, the lower specific activity suggests a functional loss in individual proteins with aging. Comparing the composition of the catalytic beta-subunits showed an age-related 4-fold increase in the cytokine-inducible subunits, LMP2 and LMP7. Additionally, the content of the activating complexes, PA28 and PA700, relative to the 20S proteasome was reduced 50%. These results suggest significant alterations in the intrinsic activity, the percentage of immunoproteasome, and the regulation of the 20S proteasome by PA28 and PA700 in aged muscle. (C) 2003 Elsevier Inc. All rights reserved.
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