Abstract
Increasing evidence shows that β-amyloid (Aβ) peptides, which are associated with Alzheimer disease (AD), are heavily glycated in patients, suggesting a role of this irreversible nonenzymatic post-translational modification in pathology. Previous reports have shown that glycation increases the toxicity of the Aβ peptides, although little is known about the mechanism. Here, we used the natural metabolic by-product methylglyoxal as a glycating agent and exploited various spectroscopic methods and atomic force microscopy to study how glycation affects the structures of the Aβ40 and Aβ42 peptides, the aggregation pathway, and the morphologies of the resulting aggregates. We found that glycation significantly slows down but does not prevent β-conversion to mature fibers. We propose that the previously reported higher toxicity of the glycated Aβ peptides could be explained by a longer persistence in an oligomeric form, usually believed to be the toxic species.
Highlights
Increasing evidence shows that -amyloid (A) peptides, which are associated with Alzheimer disease (AD), are heavily glycated in patients, suggesting a role of this irreversible nonenzymatic post-translational modification in pathology
We first explored by systematically screening the effects of buffer, pH, and ionic strength on the kinetics of glycation and self-assembly to find conditions in which aggregation would be sufficiently slow to follow the glycation process using peptides synthesized in house and previously extensively characterized [31]
Previous studies have demonstrated that A peptides are suitable substrates for glycation, a posttranslational modification of increasing interest because of its association with toxic advanced glycation end products (AGEs) species
Summary
Increasing evidence shows that -amyloid (A) peptides, which are associated with Alzheimer disease (AD), are heavily glycated in patients, suggesting a role of this irreversible nonenzymatic post-translational modification in pathology. An intense fluorescence signal with the maximum centered at 400 nm was observed for the glycated A40 peptide (A40G) (Fig. 1A).
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