Figure 6.

Pulse–chase labeling demonstrates that intracellular APPβ is produced in an intracellular compartment before secretion in NT2N neurons. NT2N neurons were pulse labeled with [³⁵S]methionine for 1 h and chased for 0, 1, 4, 8, and 24 h. Radiolabeled cell lysates (A) or media (B) were immunoprecipitated sequentially with antibody 53 (for APPβ) followed by Karen (for APP_FL in the cell lysates and APPα/β in the media). Radiolabeled immunoprecipitates were used to expose PhosphorImager plates (72 h) or X-ray film (3 wk) for visualization. C and D summarize the quantitation of experiments shown in A and B. Counts from three different experiments were normalized to percentage of maximum and plotted as shown (mean ± standard error).