Aggregation state-dependent binding of beta-amyloid peptide to protein and lipid components of rat cortical homogenates.

Beta-amyloid peptide (A beta) is the primary protein component of senile plaques in Alzheimer's disease. A beta is toxic to neuronal cell cultures, although the mechanism of neurotoxicity is unknown. Neurotoxicity has been correlated to the aggregation state of the peptide. In this work, the synthetic beta-amyloid peptide A beta(1-39) was radioiodinated and fractionated into samples containing varying degrees of aggregated material. Binding of the peptide to rat cortical homogenates (containing both lipids and membrane-associated protein) and to artificial neuronal membrane (containing only lipids) was measured. Binding increased with increasing percent aggregated peptide in the solutions. Aggregated peptide bound to both cortical homogenate and membrane, whereas monomeric peptide bound to homogenate only. These results may help discriminate among alternative mechanisms of neurotoxicity of A beta.