Specific Mutations in the Cholesterol-Binding Site of APP Alter Its Processing and Favor the Production of Shorter, Less Toxic A beta Peptides

• Excess brain cholesterol is strongly implicated in the pathogenesis of Alzheimer's disease (AD). Here we evaluated how the presence of a cholesterol-binding site (CBS) in the transmembrane and juxtamembrane regions of the amyloid precursor protein (APP) regulates its processing. We generated nine point mutations in the APP gene, changing the charge and/or hydrophobicity of the amino-acids which were previously shown as part of the CBS. Most mutations triggered a reduction of amyloid-beta peptides A beta 40 and A beta 42 secretion from transiently transfected HEK293T cells. Only the mutations at position 28 of A beta in the APP sequence resulted in a concomitant significant increase in the production of shorter A beta peptides. Mass spectrometry (MS) confirmed the predominance of A beta x-33 and A beta x-34 with the APP(K28A) mutant. The enzymatic activity of alpha-, beta-, and gamma-secretases remained unchanged in cells expressing all mutants. Similarly, subcellular localization of the mutants in early endosomes did not differ from the APP(WT) protein. A transient increase of plasma membrane cholesterol enhanced the production of A beta 40 and A beta 42 by APP(WT), an effect absent in APP(K28A) mutant. Finally, WT but not CBS mutant A beta derived peptides bound to cholesterol-rich exosomes. Collectively, the present data revealed a major role of juxtamembrane amino acids of the APP CBS in modulating the production of toxic A beta species. More generally, they underpin the role of cholesterol in the pathophysiology of AD.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Neurovetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Neurosciences (hsv//eng)

Keyword

Alzheimer's disease

Cholesterol

Amyloid precursor protein

A beta

Mutant

amyloid precursor protein

c-terminal domain

gamma-secretase

alzheimers-disease

cleavage

fragments

insights

reveals

biology

lipids

Neurosciences & Neurology

Publication and Content Type

ref (subject category)

art (subject category)