Spherical aggregates of beta-amyloid (amylospheroid) show high neurotoxicity and activate tau protein kinase I/glycogen synthase kinase-3beta.
beta-Amyloid (Abeta) acquires toxicity by self-aggregation. To identify and characterize the toxic form(s) of Abeta aggregates, we examined in vitro aggregation conditions by using large quantities of homogenous, chemically synthesized Abeta1-40 peptide. We found that slow rotation of Abeta1-40 solution reproducibly gave self-aggregated Abeta1-40 containing a stable and highly toxic moiety. Examination of the aggregates purified by glycerol-gradient centrifugation by atomic force microscopy and transmission electron microscopy revealed that the toxic moiety is a perfect sphere, which we call amylospheroid (ASPD). Other Abeta1-40 aggregates, including fibrils, were nontoxic. Correlation studies between toxicity and sphere size indicate that 10- to 15-nm ASPD was highly toxic, whereas ASPD <10 nm was nontoxic. A positive correlation between the toxicity and ASPD >10 nm also appeared to exist when Abeta1-42 formed ASPD by slow rotation. However, Abeta1-42-ASPD formed more rapidly, killed neurons at lower concentrations, and showed approximately 100-fold-higher toxicity than Abeta1-40-ASPD. The toxic ASPD was associated with SDS-resistant oligomeric bands in immunoblotting, which were absent in nontoxic ASPD. Because the formation of ASPD was not disturbed by pentapeptides that break beta-sheet interactions, Abeta may form ASPD through a pathway that is at least partly distinct from that of fibril formation. Inhibition experiments with lithium suggest the involvement of tau protein kinase I/glycogen synthase kinase-3beta in the early stages of ASPD-induced neurodegeneration. Here we describe the identification and characterization of ASPD and discuss its possible role in the neurodegeneration in Alzheimer's disease.
Mitsubishi Kagaku Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan. mie@libra.ls.m-kagaku.co.jp
Minako
M
Hoshi
Michio
M
Sato
Shinichiro
S
Matsumoto
Akihiko
A
Noguchi
Kaori
K
Yasutake
Natsuko
N
Yoshida
Kazuki
K
Sato
D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D008854:Microscopy, Electron; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats
D016229:Amyloid beta-Peptides; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D017346:Protein Serine-Threonine Kinases; D038362:Glycogen Synthase Kinase 3; C080888:tau-protein kinase