Skip to Content
Merck
  • The Alzheimer's disease-associated C99 fragment of APP regulates cellular cholesterol trafficking.

The Alzheimer's disease-associated C99 fragment of APP regulates cellular cholesterol trafficking.

The EMBO journal (2020-09-01)
Jorge Montesinos, Marta Pera, Delfina Larrea, Cristina Guardia-Laguarta, Rishi R Agrawal, Kevin R Velasco, Taekyung D Yun, Irina G Stavrovskaya, Yimeng Xu, So Yeon Koo, Amanda M Snead, Andrew A Sproul, Estela Area-Gomez
ABSTRACT

The link between cholesterol homeostasis and cleavage of the amyloid precursor protein (APP), and how this relationship relates to Alzheimer's disease (AD) pathogenesis, is still unknown. Cellular cholesterol levels are regulated through crosstalk between the plasma membrane (PM), where most cellular cholesterol resides, and the endoplasmic reticulum (ER), where the protein machinery that regulates cholesterol levels resides. The intracellular transport of cholesterol from the PM to the ER is believed to be activated by a lipid-sensing peptide(s) in the ER that can cluster PM-derived cholesterol into transient detergent-resistant membrane domains (DRMs) within the ER, also called the ER regulatory pool of cholesterol. When formed, these cholesterol-rich domains in the ER maintain cellular homeostasis by inducing cholesterol esterification as a mechanism of detoxification while attenuating its de novo synthesis. In this manuscript, we propose that the 99-aa C-terminal fragment of APP (C99), when delivered to the ER for cleavage by γ-secretase, acts as a lipid-sensing peptide that forms regulatory DRMs in the ER, called mitochondria-associated ER membranes (MAM). Our data in cellular AD models indicates that increased levels of uncleaved C99 in the ER, an early phenotype of the disease, upregulates the formation of these transient DRMs by inducing the internalization of extracellular cholesterol and its trafficking from the PM to the ER. These results suggest a novel role for C99 as a mediator of cholesterol disturbances in AD, potentially explaining early hallmarks of the disease.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
HMG-CoA Reductase Assay Kit, sufficient for 30 assays (1 mL), sufficient for 100 assays (200 μL)
Supelco
Phospholipid mixture for HPLC from Glycine max (soybean), certified reference material
Sigma-Aldrich
Desipramine hydrochloride, ≥98% (TLC), powder
Sigma-Aldrich
Monoclonal Anti-β-Tubulin antibody produced in mouse, clone TUB 2.1, ascites fluid
Sigma-Aldrich
Debrisoquine sulfate
Sigma-Aldrich
Sandoz 58-035, >98% (HPLC), powder
Sigma-Aldrich
Anti-ACSL4 (C-terminal) antibody produced in rabbit
Sigma-Aldrich
Anti-Flotillin 1 antibody produced in rabbit, ~1 mg/mL, affinity isolated antibody, buffered aqueous solution
Sigma-Aldrich
Tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, 97%
Sigma-Aldrich
Anti-Amyloid Precursor Protein, C-Terminal antibody produced in rabbit, IgG fraction of antiserum, buffered aqueous solution
Sigma-Aldrich
Tris(2-carboxyethyl)phosphine hydrochloride, powder
Sigma-Aldrich
Monoclonal Anti-β-Actin antibody produced in mouse, clone AC-15, ascites fluid
Sigma-Aldrich
Filipin complex from Streptomyces filipinensis, ≥70% (UV)
Sigma-Aldrich
DAPT, ≥98% (HPLC), solid