title: Role of ABCG1 and ABCA1 in regulation of neuronal cholesterol efflux to apolipoprotein E discs and suppression of amyloid-beta peptide generation.
abstract: Maintenance of an adequate supply of cholesterol is important for neuronal function, whereas excess cholesterol promotes amyloid precursor protein (APP) cleavage generating toxic amyloid-beta (Abeta) peptides. To gain insights into the pathways that regulate neuronal cholesterol level, we investigated the potential for reconstituted apolipoprotein E (apoE) discs, resembling nascent lipoprotein complexes in the central nervous system, to stimulate neuronal [3H]cholesterol efflux. ApoE discs potently accelerated cholesterol efflux from primary human neurons and cell lines. The process was saturable (17.5 microg of apoE/ml) and was not influenced by APOE genotype. High performance liquid chromatography analysis of cholesterol and cholesterol metabolites effluxed from neurons indicated that <25% of the released cholesterol was modified to polar products (e.g. 24-hydroxycholesterol) that diffuse from neuronal membranes. Thus, most cholesterol (approximately 75%) appeared to be effluxed from neurons in a native state via a transporter pathway. ATP-binding cassette transporters ABCA1, ABCA2, and ABCG1 were detected in neurons and neuroblastoma cell lines and expression of these cDNAs revealed that ABCA1 and ABCG1 stimulated cholesterol efflux to apoE discs. In addition, ABCA1 and ABCG1 expression in Chinese hamster ovary cells that stably express human APP significantly reduced Abeta generation, whereas ABCA2 did not modulate either cholesterol efflux or Abeta generation. These data indicate that ABCA1 and ABCG1 play a significant role in the regulation of neuronal cholesterol efflux to apoE discs and in suppression of APP processing to generate Abeta peptides.
authors.affiliation: Prince of Wales Medical Research Institute, Sydney, New South Wales 2031, Australia.
authors.forename: Woojin Scott
authors.initials: WS
authors.lastname: Kim
authors.forename: Aldwin Suryo
authors.initials: AS
authors.lastname: Rahmanto
authors.forename: Alvin
authors.initials: A
authors.lastname: Kamili
authors.forename: Kerry-Anne
authors.initials: KA
authors.lastname: Rye
authors.forename: Gilles J
authors.initials: GJ
authors.lastname: Guillemin
authors.forename: Ingrid C
authors.initials: IC
authors.lastname: Gelissen
authors.forename: Wendy
authors.initials: W
authors.lastname: Jessup
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Hill
authors.forename: Brett
authors.initials: B
authors.lastname: Garner
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001057:Apolipoproteins E / Q000378:metabolism*; D001921:Brain / Q000196:embryology; D016466:CHO Cells; D002460:Cell Line; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D052816:Foreskin; D006801:Humans; D007700:Kinetics; D008297:Male; D009474:Neurons / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: C577836:ABCA1 protein, human; C419353:ABCG1 protein, human; D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D001057:Apolipoproteins E; D011994:Recombinant Proteins; D002784:Cholesterol