Figure 1. APOE functions in normal brain are reflected in functions in AD brain.

Secreted lipoproteins containing modified APOE are indicated as a yellow disk holding the APOE protein with two representative glycans. This CNS lipoprotein interacts with a variety of CNS cells to 1) clear debris through binding to molecules at the surface of the endothelial cells and basement membrane along CNS blood vessels (in red) and to CNS glia (in green); 2) inhibit activation of glia through signaling through cell surface receptors; and 3) promote neurite outgrowth and dendritic spine formation on neurons (in blue). In the AD brain, these functions act to promote clearance of Aβ monomers and oligomers (small collections of circles), to promote anti-inflammatory processes in response to Aβ plaques (round collection of circles containing APOE molecules), and to slow intracellular neurofibrillary tangle formation (black curved lines) and propagation.