Figure 5.

The effect of EDEM1-dependent intracellular reduction on the level of APP isoforms is significantly attenuated after proteasome inhibition. Western blotting of APP, EDEM1 and actin in lysates of cells transfected with (A) APP₆₉₅, (B) APP₇₅₁, or (C) control cDNA with or without EDEM1 cotransfection (as indicated). Cells were treated with 10 µM lactacystin or 1 µM epoxomicin for 5 h before cell lysis. Overexpressed, dominant forms present in (A,B) are indicated in red. Representative experiments are shown for cells treated with epoxomicin. Similar results were obtained for cells treated with lactacystin. The levels of APP isoforms were quantified and are shown in the graphs. Values obtained for lysates of cells without EDEM1 overexpression are indicated as 1. Values representing EDEM1-transfected cells are plotted relative to 1. The values are expressed as mean ± SD, n ≥ 3, * p ˂ 0.05, *** p ˂ 0.001, Student’s t test.