FIGURE 1.

Increased LDLR levels alter the extracellular and intracellular levels of apoE in primary astrocytes. Primary astrocytes were cultured from the cortices of both WT and LDLR transgenic mice. The LDLR transgene is expressed under control of the mouse prion promoter and also contains a hemagglutinin (HA) tag. A, LDLR and HA levels in the cells were measured by immunoblot. Unglycosylated LDLR migrates at 90 kDa and several glycosylated species of the protein migrate between 100 and 150 kDa. Representative images are shown. B, the functional effect of increased LDLR levels on apoE uptake was assessed by measuring the levels of endogenously produced apoE in the culture media. Primary astrocytes were incubated for the indicated time points in serum-free medium and the amount of apoE was measured by ELISA. Mean ± S.E. (n = 4), * denotes p < 0.05, ** denotes p < 0.01, *** denotes p < 0.001. C, the amount of cell-associated apoE was also measured by immunoblot of the cell lysates obtained after a 24-h incubation. A representative image is shown.