Fig. (4) APP protein levels following cycloheximide treatment in control and NGF-treated PC12 cells grown in the presence or absence of S-MIU. Densitometric analysis of mature (m) APP751/770 (A) immature (i) APP751/770 and mAPP695 (B) and iAPP695 (C) protein expression normalized to α-tubulin in untreated (control) and 2.0 mM S-MIU-treated PC12 cells. No difference in relative mAPP751/770 levels was observed between control cells and those grown in the presence of S-MIU but the level of this isoform was significantly higher in cells grown in the presence of S-MIU following treatment with cycloheximide for 60 and 120 min (*p<0.05). Relative densities of the bands containing APP695 in S-MIU treated PC12 cells were significantly different from control in the absence of cycloheximide (**p<0.01) and following 60 and 120 mins of treatment with cycloheximide (*p<0.05; ** p < 0.01). Densitometric analysis of mAPP751/770 (D) iAPP751/770 and mAPP695 (E) and iAPP695 (F) protein expression normalized to α-tubulin samples obtained from 50 ng/mL NGF-treated PC12 cells grown in the presence or absence of 2.0 mM S-MIU. The relative density of bands containing the APP695 isoform was significantly different in cells treated with NGF alone compared to cells treated with NGF in the presence of S-MIU in the absence of cyclo-heximide (*p < 0.05; **p < 0.01) and following 120 mins of treatment with cycloheximide (*p<0.05; **p<0.01). Data are presented as the mean ± SEM and represent 5 independent experiments. Statistical significance was determined by performing a one-way ANOVA followed by Tukey-Kramer’s multiple comparisons test to determine any significant differences between NGF treated samples grown in the presence or absences of S-MIU at each time point.