Quantification of IDE and Aβ Levels

For Western Blot analysis of IDE and β-actin protein levels, samples were prepared as described above, adjusted to equal protein amounts and loaded on 10–20% tris-tricine-gradient gels (Anamed Elektrophorese, Groß-Bieberau/Rodau, Germany). For measuring total Aβ degradation, the cell culture supernatant containing remaining human Aβ40 was also separated in tris-tricine-gradient gels. After transferring proteins onto nitrocellulose membranes, IDE, β-actin and human Aβ40 were detected with the primary antibodies ST1120 (1:2000), A5441 (1:5000) and W02 (1 μg/mL), all purchased from Merck, respectively. HRP-coupled antibodies W401 (anti-rabbit, 1:5000) (Promega, Mannheim, Germany) and P0260 (anti-mouse, 1:5000) (Dako, Hamburg, Germany) were utilized as secondary antibodies. Signal detection was performed with the enhanced chemiluminescence (ECL-) method (Perkin Elmer, Rodgau-Jügesheim, Germany) and densitometrical quantification of band intensity was carried out with Image Gauge software (Version 3.45) (Fujifilm). Total proteins were detected using Ponceau S staining as described in [52 (link)] before immunodetection.