The Recombinant Amyloid-β Peptide Aβ1–42 Aggregates Faster and Is More Neurotoxic than Synthetic Aβ1–42

Aggregation of the amyloid-β (Aβ) peptide is considered a central event in the pathogenesis of Alzheimerʹs disease (AD). In order to bypass methodological bias related to a variety of impurities commonly present in typical preparations of synthetic Aβ, we developed a simple, generally applicable method for recombinant production of human Aβ and Aβ variants in Escherichia coli that provides milligram quantities of Aβ in very high purity and yield. Amyloid fibril formation in vitro by human Aβ1–42, the key amyloidogenic Aβ species in AD, was completed threefold faster with recombinant Aβ1–42 compared to synthetic preparations. In addition, recombinant Aβ1–42 was significantly more toxic to cultured rat primary cortical neurons, and it was more toxic in vivo, as shown by strongly increased induction of abnormal phosphorylation of tau and tau aggregation into neurofibrillary tangles in brains of P301L tau transgenic mice. We conclude that even small amounts of impurities in synthetic Aβ—including a significant fraction of racemized peptides that cannot be avoided due to the technical limitations of peptide synthesis—prevent or slow Aβ incorporation into the regular quaternary structure of growing β-amyloid fibrils. The results validate the use of recombinant Aβ1–42 for both in vitro and in vivo studies addressing the mechanisms underlying Aβ aggregation and its related biological consequences for the pathophysiology, therapy, and prevention of AD.