FIGURE 2.
Proteasome content increases in muscles of aged but not in rats on dietary restriction. A, levels of the 20S subunits, β1 and β5, and the 19S components, Rpt5 and Rpt6, were measured by immunoblotting with Vinculin as loading control. B, 20S proteasomes were covalently modified in crude extracts with the active site-directed probe dansyl-Ahx3L3VS followed by immunoblotting with anti-dansyl antibody. Each lane in panels A or B represents 25 μg of crude extract from gastrocnemius muscles of 4-month-old (n = 10) and 30-month-old AL (n = 10) and DR (n = 9) rats. Densitometry data and statistical analysis of protein levels (A) and proteasome activity (B) are plotted relative to the 4-month-old AL group (set to 100%). Error bars indicate standard deviation. C, changes in mRNA levels of several proteasome subunits as well as factors involved in proteasome assembly were assayed by qPCR. ***, p < 0.001.