Figure 4. Isoform-specific lipid-poor apoE clearance at the abluminal surface of mouse brain capillaries in vitro is regulated by differential internalization rates of VLDLR and LRP1.

(A) Specific binding of ¹²⁵I-labeled lipid-poor apoE2, apoE3, and apoE4 (2 nM, TCA-precipitable ¹²⁵I-radioactivity) by brain microvessels studied for a period of 30 minutes at 4°C with and without excess of unlabeled ligand at 0.5 μM. (B–D) Time-dependent internalization of lipid-poor ¹²⁵I-apoE2 (B), ¹²⁵I-apoE3 (C), and ¹²⁵I-apoE4 (D) on the abluminal surface of brain microvessels in the presence of receptor-specific blocking antibodies to LRP1 and VLDLR and excess of unlabeled ligand at 0.5 μM.