The senile plaque is a pathologic hallmark of Alzheimer’s disease (AD).
Amyloid-β peptide (Aβ), the main constituent of senile plaques, derives from the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases in the amyloidogenic pathway. Alternatively, APP can be cleaved by α-secretases within the Aβ domain to produce neurotrophic and neuroprotective α-secretase-cleaved soluble APP (sAPPα) in the nonamyloidogenic pathway.
Since APP and α-, β-, and γ-secretases are membrane proteins, APP processing is highly dependent on the membrane composition and the biophysical properties of cellular mem- brane.
The primary step in Aβ accumulation, the amyloidogenic cleavage of APP, is affected by the membrane properties such as membrane fluidity and can be modulated by removal of cholesterol and manipulation of membrane lipid composition.
Phospholipases A2 and their hydrolyzed products, such as Arachidonic Acid, DHA and other fatty acids, play important roles in the modulation of membrane properties in relation to their effects on APP processing. Aβ-membrane interactions, in turn, affect biophysical membrane properties and accelerate the amyloidogenic processing of APP.
For those of you who would like toknow more on the crucial importance of membrane lipidomics in Alzheimer Disease, here is the link to a great and comprehensive review: http://www.ncbi.nlm.nih.gov/pubmed/24553856 (Cellular Membrane Fluidity in Amyloid Precursor Protein Processing. Xiaoguang et al., 2014).