Figure 3

ApoE-derived peptide affects APP trafficking in primary cortical and hippocampal neuronal cells. A. Cultured cortical neuronal cells were treated with control (PBS) or apoE monomer (n = 3, 1 μM for 24 hr). Cell surface proteins were biotinylated, isolated with avidin-conjugated beads, and immunoblotted with 22C11 antibody against rodent APP. Total APP and β-actin in cell lysates were measured in the bottom panel. B. Quantification of biotin-labeled cell surface APP in primary cortical neurons showed no significant change by apoE monomer compared to control. C. Cultured cortical neuronal cells were treated with control (PBS), apoE dimer, or apoE trimer (n = 3, 1 μM for 24 hr). Total APP and β-actin in cell lysates were measured in the bottom panel. D. Quantification of biotin-labeled cell surface APP showed a 72% (p < 0.01, n = 3) and 166% (p < 0.001, n = 3) increase in surface APP by the apoE dimer and trimer, respectively. Error bars indicate SEM. E. Cultured hippocampal neurons were transfected at DIV12 with GFP conjugated APP. At DIV 14 cells were treated with PBS control or the apoE monomer (n = 10, 1 μM), dimer (n = 10, 1 μM), or trimer (n = 10, 1 μM) for 24 h, and surface APP was measured by live cell staining. F. Quantification of surface APP intensity in (A) showed a 21% and 43% increase by the dimer and trimer, respectively (n = 10, *p < 0.05, *p < 0.01).