Identification of neuronal plasma membrane microdomains that colocalize beta-amyloid and presenilin: implications for beta-amyloid precursor protein processing.

Alzheimer's disease (AD) is associated with the accumulation of extracellular deposits of the beta-amyloid protein (Abeta). Abeta is a result of misprocessing of the beta-amyloid precursor protein (APP). Gamma-secretase is involved in APP misprocessing and one hypothesis holds that this secretase is identical to PS1. We tested this hypothesis by determining whether PS is co-localised with Abeta in situ. Using confocal analyses and a sensitive immunogold procedure we show that PS and Abeta are co-localised within discrete microdomains of neuronal plasma membranes in AD patients and in aged dogs, an established model of human brain aging. Our data indicate that APP misprocessing occurs in discrete plasma membrane domains of neurons and provide evidence that PS1 is critically involved in Abeta formation.