FIGURE 7.

The effect of LDLR on Aβ uptake and clearance is not dependent on apoE. A, to determine whether the effect of LDLR on Aβ uptake and clearance requires the presence of apoE, LDLR was expressed in apoE^−/− and WT primary astrocytes via lentiviral transduction. LDLR expression was confirmed by immunoblot for HA. LDLR Tg astrocyte lysate is shown for comparison. B, to confirm that the LDLR protein expressed after lentiviral transduction was functional, WT cells were transduced and the amount of endogenously produced apoE was measured by ELISA in the cell medium after a 24-h incubation. Mean ± S.E. (n ≥ 4). ** denotes p < 0.01. C, Aβ uptake was measured in WT and apoE^−/− primary astrocytes transduced with LDLR lentivirus. Aβ40 (2 μg/ml) was incubated with the cells for 3 h. The cells were then washed with PBS, treated with trypsin to remove cell surface-bound Aβ, and lysed in Triton X-100 lysis buffer. The cell-internalized Aβ was then measured by ELISA. Control samples were transduced with the empty lentivirus. Mean ± S.E. (n ≥ 4). ** denotes p < 0.01; *** denotes p < 0.001; n.s., not significant. D, Aβ clearance was assessed by the addition of Aβ40 (2 μg/ml) to the media of WT and ApoE^−/− astrocytes transduced with the LDLR lentivirus. After 24 h, the amount of Aβ remaining was measured by ELISA and compared with cells transduced with empty lentivirus. Mean ± S.E. (n ≥ 4). *** denotes p < 0.001; n.s., not significant.