ApoER2 proteolysis induced by NGF depends on TrkA tyrosine kinase activity and on metalloproteinase activity. PC12-ApoER2 cells were serum-starved and pre-treated with 10 μM DAPT and (A) 100 nM K252a or (C) with 50 μM GM6001 for 1 h. Then, the cells were incubated with 100 ng/mL NGF for 2 h. ApoER2, ApoER2-CTF and the proteolytic fragment of p75NTR (control) were determined by western blot analysis using antibodies directed against their intracellular regions. α-tubulin is shown as a loading control, and the phosphorylated form of AKT is a control for TrkA activation by NGF. (B and D) The levels of ApoER2 CTF were normalized to the loading control α-tubulin and plotted as the average ± SD of three independent experiments. One way ANOVA, Holm-Sidak post-hoc test, **P < 0.01; *P < 0.05.