Altered proteasome function and subunit composition in aged muscle |
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Authors: | Husom Aimee D Peters Elizabeth A Kolling Erin A Fugere Nicole A Thompson LaDora V Ferrington Deborah A |
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Institution: | Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA. |
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Abstract: | 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 1 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. |
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Keywords: | Aging Muscle atrophy Proteasome Proteasome subunits Sarcopenia Skeletal muscle PA28 PA700 |
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