Figure 9.

Altered expression of constitutive and inducible proteasome components. A,B. No significant difference in the levels of 19S subunit S1 because age or genotype is observed in WT or APP/PS1 mice, in spite of a tendency to decrease in 12‐month‐old APP/PS1. C,D. Decreased expression of β5 subunit in APP/PS1 mice aged 6 and 12 months when compared with WT. In contrast, β5 subunit expression is higher at 12 months than at 3 months in WT animals. E,F. Protein levels of MECL‐1 are reduced in APP/PS1 animals aged 6 months when compared with younger animals. This reduction is not maintained at 12 months. G,H. Quantification for LMP2 indicates a significant increase in APP/PS1 mice at 12 months compared with WT and APP/PS1 animals aged 3 or 6 months. I,J. The pathology progression with age is associated with an upregulation of the proteasome activator PA28 regulatory complex in APP/PS1 mice. In contrast, PA28 expression is reduced in aged WT animals. K,L. The expression of UCHL‐1 decreases in APP/PS1 mice at 6 and 12 months with respect to control littermates. A,C,E,G,I,K. Representative immunoblots for β5, MECL‐1, LMP2, PA28 and corresponding β‐actin loading control indicating the molecular weight of each protein. B,D,F,H,J,L. Densitometric quantification of β5, MECL‐1, LMP2, PA28 and UCHL‐1 levels with respect to β‐actin. Data are represented as the mean ± SEM of three animals per group. *P < 0.05, **P < 0.01, ***P < 0.001 compared with WT animals (Student's t‐test). #P < 0.05, ##P < 0.01, ###P < 0.001 compared with animals aged 3 months (Tukey's post hoc test). $$P < 0.01 compared with animals aged 6 months (Tukey's post hoc test).