title: A novel reciprocal and biphasic relationship between membrane cholesterol and beta-secretase activity in SH-SY5Y cells and in human platelets.
abstract: Research into the cause of Alzheimer's disease (AD) has identified strong connections to cholesterol. Cholesterol and cholesterol esters can modulate amyloid precursor protein (APP) processing, thus altering production of the Abeta peptides that deposit in cortical amyloid plaques. Processing depends on the encounter between APP and cellular secretases, and is thus subject to the influence of cholesterol-dependent factors including protein trafficking, and distribution between membrane subdomains. We have directly investigated endogenous membrane beta-secretase activity in the presence of a range of membrane cholesterol levels in SH-SY5Y human neuroblastoma cells and human platelets. Membrane cholesterol significantly influenced membrane beta-secretase activity in a biphasic manner, with positive correlations at higher membrane cholesterol levels, and negative correlations at lower membrane cholesterol levels. Platelets from individuals with AD or mild cognitive impairment (n = 172) were significantly more likely to lie within the negative correlation zone than control platelets (n = 171). Pharmacological inhibition of SH-SY5Y beta-secretase activity resulted in increased membrane cholesterol levels. Our findings are consistent with the existence of a homeostatic feedback loop between membrane cholesterol level and membrane beta-secretase activity, and suggest that this regulatory mechanism is disrupted in platelets from individuals with cognitive impairment.
authors.affiliation: School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, UK.
authors.forename: Wei Wei
authors.initials: WW
authors.lastname: Liu
authors.forename: Stephen
authors.initials: S
authors.lastname: Todd
authors.forename: David T R
authors.initials: DT
authors.lastname: Coulson
authors.forename: G Brent
authors.initials: GB
authors.lastname: Irvine
authors.forename: A Peter
authors.initials: AP
authors.lastname: Passmore
authors.forename: Bernadette
authors.initials: B
authors.lastname: McGuinness
authors.forename: Maeve
authors.initials: M
authors.lastname: McConville
authors.forename: David
authors.initials: D
authors.lastname: Craig
authors.forename: Janet A
authors.initials: JA
authors.lastname: Johnston
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001792:Blood Platelets / Q000166:cytology / Q000648:ultrastructure*; D016022:Case-Control Studies; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D003072:Cognition Disorders / Q000097:blood; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D016014:Linear Models; D008297:Male; D009447:Neuroblastoma / Q000473:pathology / Q000648:ultrastructure; D018709:Statistics, Nonparametric; D013347:Subcellular Fractions; D013997:Time Factors; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D002784:Cholesterol; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human