Influence of aggregation propensity and stability on amyloid fibril formation as studied by Fourier transform infrared spectroscopy and two-dimensional COS analysis.

ABSTRACT

Understanding the process of amyloidogenesis is important for the future treatment of misfolding-based diseases, such as Alzheimer's, spongiform encephalopathies, and other important disorders affecting humans. In this work, we have used one of the best-characterized models for folding and misfolding, the activation domain of human procarboxypeptidase A2 (ADA2h). The wild type (WT) and three mutants affecting the kinetics of aggregation have been studied by IR from the folded state at acidic pD to fibril formation, showing the disappearance of structured features prior to a dramatic increase in the magnitude of the amyloid-characteristic band upon temperature induction. Transmission electron microscopy (TEM) shows that amyloid fibrils are formed under the conditions used in this work. The kinetics of the process observed for WT is clearly affected by the aggregation tendency and the stability of each mutant, although the final state is the same. Our conclusion is that this domain is nucleated prior to the conformational reorganization rendering the final amyloid fibril, which is ultimately reached in a manner independent of the aggregation tendency and the stability of each variant.