Cholesterol-dependent generation of a seeding amyloid beta-protein in cell culture.

Deposition of aggregated amyloid beta-protein (Abeta), a proteolytic cleavage product of the amyloid precursor protein (Abeta ), is a critical step in the development of Alzheimer's disease(Abeta++). However, we are far from understanding the molecular mechanisms underlying the initiation of Abeta polymerization in vivo. Here, we report that a seeding Abeta, which catalyzes the fibrillogenesis of soluble Abeta, is generated from the apically missorted amyloid precursor protein in cultured epithelial cells. Furthermore, the generation of this Abeta depends exclusively on the presence of cholesterol in the cells. Taken together with mass spectrometric analysis of this novel Abeta and our recent study (3), it is suggested that a conformationally altered form of Abeta, which acts as a "seed" for amyloid fibril formation, is generated in intracellular cholesterol-rich microdomains.