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.
Biodefense Division, Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, 7000 East Avenue, L-446, Livermore, California 94551, USA.
Brett A
BA
Chromy
Richard J
RJ
Nowak
Mary P
MP
Lambert
Kirsten L
KL
Viola
Lei
L
Chang
Pauline T
PT
Velasco
Bryan W
BW
Jones
Sara J
SJ
Fernandez
Pascale N
PN
Lacor
Peleg
P
Horowitz
Caleb E
CE
Finch
Grant A
GA
Krafft
William L
WL
Klein
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