The effects of age and food restriction on proteasome function in rat liver supernatant (100,000 x g) were investigated. The cellular level of the proteasome has been quantitated by using Western blot analysis. The level of the proteasome was not affected by either age or food restriction. The three best-characterized proteasomal peptidase activities, chymotrypsin-like (ChT- L), trypsin-like (T-L), and peptidylglutamyl peptide hydrolyzing (PGPH) activities, were measured in the presence and absence of the proteasomal activator, sodium dodecyl sulfate (SDS). Basal Ch T-L, T-L, and PGPH activities were not markedly affected by either age or food restriction. SDS- stimulated ChT-L and T-L activities increased ≃ 15% and ≃ 30%, respectively, between 7 and 26 months of age, and the increase of both activities was prevented by food restriction. In marked contrast, the SDS- stimulated PGPH activity decreased ≃40% with age. Food restriction, while not preventing the age-related decline, maintained higher levels of SDS- stimulated PGPH activity at all ages. The proteolytic activity of the proteasome toward casein was not altered by either age or food restriction. In conclusion, the cellular level of the proteasome as well as the caseinolytic activity of the proteasome appear to be unaffected by either age or food restriction. It appears unlikely that the proteasome activity changes are related to the reported age-associated decline of protein degradation. Simultaneously, proteasomal peptidase activities appear to be differentially regulated by both age and food restriction. It suggests mare subtle age- related changes in proteasome function, which could include an effect on proteasomal subunit composition.
|Original language||English (US)|
|Journal||Journals of Gerontology - Series A Biological Sciences and Medical Sciences|
|State||Published - Sep 1996|
ASJC Scopus subject areas
- Geriatrics and Gerontology