Interactions of Aβ(1–40) with Glycerophosphocholine and Intact Erythrocyte Membranes: Fluorescence and Circular Dichroism Studies.

Deposition of amyloid β peptide in human brain in the form of senile plaques is a neuropathological hallmark of Alzheimer's disease (AD). Levels of a phospholipid breakdown product, glycerophosphocholine (GPC), also increase in AD brain. The effect of GPC on amyloid β(1–40) peptide (Aβ) aggregation in PBS buffer was investigated by circular dichroism and fluoresence spectroscopy; interactions of Aβ and GPC with the intact erythrocyte membrane was examined by fluoresence spectroscopy. Fluorescamine labeled Aβ studies indicate GPC enhances Aβ aggregation. CD spectroscopy reveals that Aβ in the presence of GPC adopts 14% more β-sheet structure than does Aβ alone. Fluorescamine anisotropy measurements show that GPC and Aβ interact in the phospholipid head-group region of the erythrocyte membrane. In summary, both soluble Aβ and GPC insert into the phospholipid head-group region of the membrane where they interact leading to β-sheet formation in soluble Aβ which enhances Aβ aggregation. [ABSTRACT FROM AUTHOR]