Amyloid beta protein-(1-42) forms calcium-permeable, Zn2+-sensitive channel.

Amyloid beta protein (AbetaP) forms senile plaques in the brain of the patients with Alzheimer's disease. The early-onset AD has been correlated with an increased level of 42-residue AbetaP (AbetaP1-42). However, very little is known about the role of AbetaP1-42 in such pathology. We have examined the activity of AbetaP1-42 reconstituted in phospholipid vesicles. Vesicles reconstituted with AbetaP show strong immunofluorescence labeling with an antibody raised against an extracellular domain of AbetaP suggesting the incorporation of AbetaP peptide in the vesicular membrane. Vesicles reconstituted with AbetaP showed a significant level of 45Ca2+ uptake. The 45Ca2+ uptake was inhibited by (i) a monoclonal antibody raised against the N-terminal region of AbetaP, (ii) Tris, and (iii) Zn2+. However, reducing agents Trolox and dithiothreitol did not inhibit the 45Ca2+ uptake, indicating that the oxidation of AbetaP or its surrounding lipid molecules is not directly involved in the AbetaP-mediated Ca2+ uptake. An atomic force microscope was used to image the structure and physical properties of these vesicles. Vesicles ranged from 0.5 to 1 microm in diameter. The stiffness of the AbetaP-containing vesicles was significantly higher in the presence of calcium. The stiffness change was prevented in the presence of zinc, Tris, and anti-AbetaP antibody but not in the presence of Trolox and dithiothreitol. Thus the stiffness change is consistent with the vesicular uptake of Ca2+. These findings provide biochemical and structural evidence that AbetaP1-42 forms calcium-permeable channels and thus may induce cellular toxicity by regulating the calcium homeostasis in Alzheimer's disease.