Self-assembly of Abeta(1-42) into globular neurotoxins.
Amyloid beta 1-42 (Abeta(1-42)) is a self-associating peptide that becomes neurotoxic upon aggregation. Toxicity originally was attributed to the presence of large, readily formed Abeta fibrils, but a variety of other toxic species are now known. The current study shows that Abeta(1-42) can self-assemble into small, stable globular assemblies free of fibrils and protofibrils. Absence of large molecules was verified by atomic force microscopy (AFM) and nondenaturing gel electrophoresis. Denaturing electrophoresis revealed that the globular assemblies comprised oligomers ranging from trimers to 24mers. Oligomers prepared at 4 degrees C stayed fibril-free for days and remained so when shifted to 37 degrees C, although the spectrum of sizes shifted toward larger oligomers at the higher temperature. The soluble, globular Abeta(1-42) oligomers were toxic to PC12 cells, impairing reduction of MTT and interfering with ERK and Rac signal transduction. Occasionally, oligomers were neither toxic nor recognized by toxicity-neutralizing antibodies, suggesting that oligomers could assume alternative conformations. Tests for oligomerization-blocking activity were carried out by dot-blot immunoassays and showed that neuroprotective extracts of Ginkgo biloba could inhibit oligomer formation at very low doses. The observed neurotoxicity, structure, and stability of synthetic Abeta(1-42) globular assemblies support the hypothesis that Abeta(1-42) oligomers play a role in triggering nerve cell dysfunction and death in Alzheimer's disease.
Chromy
Brett A
BA
Biodefense Division, Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, 7000 East Avenue, L-446, Livermore, California 94551, USA.
Nowak
Richard J
RJ
Lambert
Mary P
MP
Viola
Kirsten L
KL
Chang
Lei
L
Velasco
Pauline T
PT
Jones
Bryan W
BW
Fernandez
Sara J
SJ
Lacor
Pascale N
PN
Horowitz
Peleg
P
Finch
Caleb E
CE
Krafft
Grant A
GA
Klein
William L
WL
D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D000818:Animals; D001831:Body Temperature; D002470:Cell Survival / Q000187:drug effects; D004058:Diffusion; D000939:Epitopes / Q000737:chemistry; D020441:Ginkgo biloba; D006801:Humans; D008024:Ligands; D018696:Neuroprotective Agents / Q000737:chemistry; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D009580:Nitroblue Tetrazolium / Q000737:chemistry; D016716:PC12 Cells; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D010936:Plant Extracts / Q000737:chemistry; D011487:Protein Conformation; D051381:Rats
D016229:Amyloid beta-Peptides; D000939:Epitopes; D008024:Ligands; D018696:Neuroprotective Agents; D009498:Neurotoxins; D010446:Peptide Fragments; D010936:Plant Extracts; C075222:amyloid beta-protein (1-42); D009580:Nitroblue Tetrazolium