BCNU increases surface levels of immature APP. A) Surface biotinylation and biotin immunoprecipitation experiments showed significantly increased surface levels of immature APP in BCNU-treated 7WD10 cells compared to untreated cells. B) Quantitation of the signal in A) revealed increased surface to total APP levels for immature APP by 184% but the levels of mature APP were unaltered. C) Treatment of 7WD10 cells with BCNU at 10.0 uM concentration followed by cycloheximide chase at indicated time points did not alter APP half-life or stability. For all samples, n = 4 ± SEM. ***, P < 0.001 versus controls by t test. APP, Alzheimer's precursor protein; BCNU, 1, 3 bis (2-chloroethyl)-1-nitrosourea; SEM, standard error of the mean.