Efficient reversal of Alzheimer's disease fibril formation and elimination of neurotoxicity by a small molecule.
The Abeta1-42 peptide that is overproduced in Alzheimer's disease (AD) from a large precursor protein has a normal amino acid sequence but, when liberated, misfolds at neutral pH to form "protofibrils" and fibrils that are rich in beta-sheets. We find that these protofibrils or fibrils are toxic to certain neuronal cells that carry Ca-permeant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Disrupting the structure of the Abeta1-42 fibrils and protofibrils might lead to the discovery of molecules that would be very useful in the treatment of AD. A high-throughput screen of a library of >3,000 small molecules with known "biological activity" was set up to find compounds that efficiently decrease the beta-sheet content of aggregating Abeta1-42. Lead compounds were characterized by using thioflavin T (ThT) as a beta-sheet assay. The most effective of six compounds found was 4,5-dianilinophthalimide (DAPH) under the following conditions: DAPH at low micromolar concentrations abolishes or greatly reduces previously existing fully formed Abeta1-42 fibrils, producing instead amorphous materials without fibrils but apparently containing some protofibrils and smaller forms. Coincubation of the Abeta1-42 peptide with DAPH produces either amorphous materials or empty fields. Coincubation of DAPH and Abeta1-42 greatly reduces the beta-sheet content, as measured with ThT fluorescence, and produces a novel fluorescent complex with ThT. When the Abeta1-42 peptide was coincubated with DAPH at very low micromolar concentrations, the neuronal toxicity mentioned above (Ca(2+) influx) was eliminated. Clearly, DAPH is a promising candidate for AD therapy.
Blanchard
Barbara J
BJ
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Chen
Albert
A
Rozeboom
Leslie M
LM
Stafford
Kate A
KA
Weigele
Peter
P
Ingram
Vernon M
VM
D000544:Alzheimer Disease / Q000188:drug therapy* / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D016874:Neurofibrillary Tangles / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D010797:Phthalimides / Q000494:pharmacology*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism
D016229:Amyloid beta-Peptides; D009498:Neurotoxins; D010446:Peptide Fragments; D010797:Phthalimides; D018091:Receptors, AMPA; C075222:amyloid beta-protein (1-42); C098874:4,5-dianilinophthalimide