Fluorescent and luminescent fusion proteins for analyses of amyloid beta peptide aggregation.

The amyloid beta (Aβ) peptide is regarded as a causative agent of Alzheimer's disease. In this study, fluorescent and luminescent fusion proteins were constructed to analyze Aβ aggregation. A system was developed to monitor changes in luminescence that provides information about Aβ aggregation. In the presence of monomeric Aβ, the fusion protein exhibits higher luminescence intensity, and the luminescence intensity is diminished after aggregation of the fusion protein and Aβ. In contrast, the fluorescence is sustained in the presence of Aβ. In the absence of Aβ, the fusion protein self-aggregates, and its luminescence and fluorescence are quenched, thus decreasing the background fluorescence and enhancing the detection of Aβ inside and outside the cells. The ratio of the luminescence intensity to the fluorescence intensity would allow the aggregation degrees of Aβ to be distinguished. This study would be a promising method for analyzing the aggregation state of a particular amyloid protein/peptide (monomer, oligomer, or fibril), as well as the distribution of the amyloid protein/peptide within and at the cell surface, by using a single fusion protein. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.