Proteasome activity in biopsies of Epm2a+/+ and Epm2a-/- mice.

A) Proteasome activity was assessed by using the luminogenic proteasome substrate (succinyl-leucine-leucine-valine-tyrosine-aminoluciferine) in extracts from whole brain and liver of Epm2a+/+ and Epm2a-/- mice as described in Materials and Methods. Data are presented as luciferase activity (mean±SEM; n: 4), and represent the average of two luciferase activity determinations for each sample. B) Fifty micrograms of total lysates from liver and whole brain biopsies of two Epm2a+/+ (A and B) and two Epm2a-/- mice (1 and 2) were analyzed by SDS–PAGE and western blotting using anti-S1 (19S regulatory particle), anti-β2 (20S proteasome) and anti-tubulin antibodies.