Interaction between human amphipathic apolipoproteins and amyloid beta-peptide: surface plasmon resonance studies.

Several apolipoproteins including apoE and apoA-I are known to be associated with amyloid beta-peptide, a major component of senile plaques in Alzheimer's disease. In the present study the interaction between three human amphipathic apolipoproteins apoE3, apoA-I and apoA-II and immobilized amyloid beta-peptide (1-40) was quantified by plasmon resonance. The interactions were saturable and reversible. The results demonstrated a high affinity of the binding of amphipathic apolipoproteins to amyloid beta-peptide. On the other hand, only a small population of synthetic amyloid beta-peptide participated in the interaction. The apparent equilibrium dissociation constants K(D) were 10 nM for apoE3, 25 nM for apoA-I and 80 nM for apoA-II under physiological conditions. The affinity of the apoE3-amyloid beta-peptide binding was not affected by pH in the range 6.0-8.0 but was significantly increased by high salt concentration. ApoA-I mainly followed similar patterns. A major participation of hydrophobic forces in the binding of apoE3 and apoA-I to amyloid beta-peptide was suggested.