Related Experiment Videos
The role of cholesterol in the biosynthesis of beta-amyloid
E R Frears1, D J Stephens, C E Walters
1Neurodegeneration Unit, St George's Hospital Medical School, London, UK.
Abstract:
Addition of the beta-hydroxy-beta-methylglutaryl-CoA (HmG-CoA) reductase inhibitor lovastatin to human HEK cells transfected with the amyloid precursor protein (APP) reduces intracellular cholesterol/protein ratios by 50%, and markedly inhibits beta-secretase cleavage of newly-synthesized APP. Exogenous water-solubilized cholesterol at 200 microg/ml concentration increases newly synthesized beta-amyloidogenic products four-fold. These intracellular changes are detectable by immunoprecipitation and immunofluorescent labelling. Analyses of the fragments captured from culture medium by an N-terminal anti-beta-amyloid antibody on ProteinChip arrays and detected using surface-enhanced laser desorption/ionization (SELDI) mass spectrometry revealed that culture with cholesterol (200 microg/ml) increased secretion of beta-amyloid 1-40 by 1.8-fold, and increased secretion of beta-amyloid 1-42. Changes in APP processing by cholesterol may mediate the way in which the ApoE4 allele increases risk of developing Alzheimer's disease (AD) in western populations.
Insights
Lovastatin reduces cholesterol and amyloid precursor protein (APP) cleavage. Increased cholesterol boosts beta-amyloid production, potentially linking cholesterol to Alzheimer's disease (AD) risk via ApoE4.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Alzheimer's disease (AD) is linked to amyloid precursor protein (APP) processing.
- Cholesterol metabolism is implicated in neurodegenerative diseases.
- The ApoE4 allele is a significant risk factor for AD.
Purpose of the Study:
- To investigate the role of cholesterol in APP processing and beta-amyloid production.
- To examine the effects of lovastatin, a cholesterol-lowering drug, on APP metabolism.
- To explore potential mechanisms linking cholesterol, APP, and AD pathogenesis.
Main Methods:
- Human HEK cells transfected with APP were treated with lovastatin or exogenous cholesterol.
- Intracellular cholesterol/protein ratios were measured.
- Beta-secretase cleavage of APP was assessed.
- Beta-amyloid secretion was quantified using immunoprecipitation, immunofluorescent labeling, ProteinChip arrays, and SELDI mass spectrometry.
Main Results:
- Lovastatin reduced intracellular cholesterol/protein ratios by 50% and inhibited beta-secretase cleavage of APP.
- Exogenous cholesterol increased newly synthesized beta-amyloidogenic products four-fold.
- Cholesterol treatment increased secretion of beta-amyloid 1-40 by 1.8-fold and beta-amyloid 1-42.
Conclusions:
- Cholesterol levels significantly influence APP processing and beta-amyloid production.
- Modulating cholesterol may represent a therapeutic strategy for AD.
- Cholesterol-mediated changes in APP processing may explain the increased AD risk associated with the ApoE4 allele.