title: apoE isoform-specific disruption of amyloid beta peptide clearance from mouse brain.
abstract: Neurotoxic amyloid beta peptide (Abeta) accumulates in the brains of individuals with Alzheimer disease (AD). The APOE4 allele is a major risk factor for sporadic AD and has been associated with increased brain parenchymal and vascular amyloid burden. How apoE isoforms influence Abeta accumulation in the brain has, however, remained unclear. Here, we have shown that apoE disrupts Abeta clearance across the mouse blood-brain barrier (BBB) in an isoform-specific manner (specifically, apoE4 had a greater disruptive effect than either apoE3 or apoE2). Abeta binding to apoE4 redirected the rapid clearance of free Abeta40/42 from the LDL receptor-related protein 1 (LRP1) to the VLDL receptor (VLDLR), which internalized apoE4 and Abeta-apoE4 complexes at the BBB more slowly than LRP1. In contrast, apoE2 and apoE3 as well as Abeta-apoE2 and Abeta-apoE3 complexes were cleared at the BBB via both VLDLR and LRP1 at a substantially faster rate than Abeta-apoE4 complexes. Astrocyte-secreted lipo-apoE2, lipo-apoE3, and lipo-apoE4 as well as their complexes with Abeta were cleared at the BBB by mechanisms similar to those of their respective lipid-poor isoforms but at 2- to 3-fold slower rates. Thus, apoE isoforms differentially regulate Abeta clearance from the brain, and this might contribute to the effects of APOE genotype on the disease process in both individuals with AD and animal models of AD.
authors.affiliation: Center for Neurodegenerative and Vascular Brain Disorders, Department of Neurosurgery, University of Rochester Medical School, Rochester, New York 14642, USA.
authors.forename: Rashid
authors.initials: R
authors.lastname: Deane
authors.forename: Abhay
authors.initials: A
authors.lastname: Sagare
authors.forename: Katie
authors.initials: K
authors.lastname: Hamm
authors.forename: Margaret
authors.initials: M
authors.lastname: Parisi
authors.forename: Steven
authors.initials: S
authors.lastname: Lane
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Finn
authors.forename: David M
authors.initials: DM
authors.lastname: Holtzman
authors.forename: Berislav V
authors.initials: BV
authors.lastname: Zlokovic
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D053318:Apolipoprotein E3 / Q000235:genetics / Q000378:metabolism*; D053327:Apolipoprotein E4 / Q000235:genetics / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism*; D001812:Blood-Brain Barrier / Q000378:metabolism*; D004195:Disease Models, Animal; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008297:Male; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D053318:Apolipoprotein E3; D053327:Apolipoprotein E4; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D020033:Protein Isoforms; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins; C036053:VLDL receptor