title: Amyloid-β protein modulates the perivascular clearance of neuronal apolipoprotein E in mouse models of Alzheimer's disease.
abstract: The deposition of amyloid-β protein (Aβ) in the brain is a hallmark of Alzheimer's disease (AD). Apolipoprotein E (apoE) is involved in the clearance of Aβ from brain and the APOE ε4 allele is a major risk factor for sporadic AD. We have recently shown that apoE is drained into the perivascular space (PVS), where it co-localizes with Aβ. To further clarify the role of apoE in perivascular clearance of Aβ, we studied apoE-transgenic mice over-expressing human apoE4 either in astrocytes (GE4) or in neurons (TE4). These animals were crossbred with amyloid precursor protein (APP)-transgenic mice and with APP-presenilin-1 (APP-PS1) double transgenic mice. Using an antibody that specifically detects human apoE (h-apoE), we observed that astroglial expression of h-apoE in GE4 mice leads to its perivascular drainage, whereas neuronal expression in TE4 mice does not, indicating that neuron-derived apoE is usually not the subject of perivascular drainage. However, h-apoE was observed not only in the PVS of APP-GE4 and APP-PS1-GE4 mice, but also in that of APP-TE4 and APP-PS1-TE4 mice. In all these mouse lines, we found co-localization of neuron-derived h-apoE and Aβ in the PVS. Aβ and h-apoE were also found in the cytoplasm of perivascular astrocytes indicating that astrocytes take up the neuron-derived apoE bound to Aβ, presumably prior to its clearance into the PVS. The uptake of apoE-Aβ complexes into glial cells was further investigated in glioblastoma cells. It was mediated by α(2)macroglobulin receptor/low density lipoprotein receptor-related protein (LRP-1) and inhibited by adding receptor-associated protein (RAP). It results in endosomal Aβ accumulation within these cells. These results suggest that neuronal apoE-Aβ complexes, but not neuronal apoE alone, are substrates for LRP-1-mediated astroglial uptake, transcytosis, and subsequent perivascular drainage. Thus, the production of Aβ and its interaction with apoE lead to the pathological perivascular drainage of neuronal apoE and provide insight into the pathological interactions of Aβ with neuronal apoE metabolism.
authors.affiliation: Laboratory of Neuropathology, Institute of Pathology, University of Ulm, Ulm, Germany.
authors.forename: Harshvardhan
authors.initials: H
authors.lastname: Rolyan
authors.forename: Ann Caroline
authors.initials: AC
authors.lastname: Feike
authors.forename: Ajeet Rijal
authors.initials: AR
authors.lastname: Upadhaya
authors.forename: Andreas
authors.initials: A
authors.lastname: Waha
authors.forename: Tom
authors.initials: T
authors.lastname: Van Dooren
authors.forename: Christian
authors.initials: C
authors.lastname: Haass
authors.forename: Gerd
authors.initials: G
authors.lastname: Birkenmeier
authors.forename: Claus U
authors.initials: CU
authors.lastname: Pietrzik
authors.forename: Fred
authors.initials: F
authors.lastname: Van Leuven
authors.forename: Dietmar Rudolf
authors.initials: DR
authors.lastname: Thal
mesh_terms: D000544:Alzheimer Disease / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism*; D001921:Brain / Q000473:pathology*; D045744:Cell Line, Tumor; D002552:Cerebral Ventricles / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D026563:LDL-Receptor Related Protein-Associated Protein / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D008822:Mice, Transgenic; D009447:Neuroblastoma / Q000473:pathology / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism*; D053764:Presenilin-1 / Q000235:genetics; D011973:Receptors, LDL / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D001057:Apolipoproteins E; D005904:Glial Fibrillary Acidic Protein; D026563:LDL-Receptor Related Protein-Associated Protein; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; C508853:PSEN1 protein, human; D053764:Presenilin-1; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins