Abstract
Amyloid fibril formation is associated with a number of debilitating systemic and neurodegenerative diseases. One of the most prominent is Alzheimer disease in which aggregation and deposition of the Aβ peptide occur. Aβ is widely considered to mediate the extensive neuronal loss observed in this disease through the formation of soluble oligomeric species, with the final fibrillar end product of the aggregation process being relatively inert. Factors that influence the aggregation of these amyloid-forming proteins are therefore very important. We have screened a library of 96 amphipathic molecules for effects on Aβ(1-42) aggregation and self-association. We find, using thioflavin T fluorescence and electron microscopy assays, that 30 of the molecules inhibit the aggregation process, whereas 36 activate fibril formation. Several activators and inhibitors were subjected to further analysis using analytical ultracentrifugation and circular dichroism. Activators typically display a 1:10 peptide:detergent stoichiometry for maximal activation, whereas the inhibitors are effective at a 1:1 stoichiometry. Analytical ultracentrifugation and circular dichroism experiments show that activators promote a mixture of unfolded and β-sheet structures and rapidly form large aggregates, whereas inhibitors induce α-helical structures that form stable dimeric/trimeric oligomers. The results suggest that Aβ(1-42) contains at least one small molecule binding site, which modulates the secondary structure and aggregation processes. Further studies of the binding of these compounds to Aβ may provide insight for developing therapeutic strategies aimed at stabilizing Aβ in a favorable conformation.
Highlights
A aggregation may be modulated by small lipid-like molecules
We have used a similar screen of the 96 lipid-like compounds used in the apoC-II study to investigate the effect of these amphipathic molecules on A1–42 amyloid fibril formation and secondary structure with the aim of identifying compounds that may stabilize oligomeric forms of the peptide
Fibril formation was initiated by mixing A1–42 with these solutions, and the change in thioflavin T (ThT) fluorescence was monitored over a 24-h period
Summary
A aggregation may be modulated by small lipid-like molecules. Results: Activators induced -structure and rapid aggregation, whereas inhibitors induced ␣-helical structure and small A oligomers. Alzheimer disease is the leading cause of dementia in the elderly human population [1] This form of neurodegeneration is characterized by the formation of intracellular neurofibrillary tangles, neuronal and synaptic loss, and the extracellular aggregates of amyloid  (A) peptide as plaque material [1]. Several studies have visualized extensive A association with cell and synthetic membranes [9, 10] These surfaces have been shown either to increase the degree of amyloid fibril formation or to inhibit the process, based on the charge, curvature, and composition of the lipid surface [11,12,13,14]. Lipid molecules are not amenable to biophysical studies as they spontaneously form aggre-
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have