Identification of potentially therapeutic short cyclic peptides against protein misfolding diseases

Protein misfolding and aggregation is a common pathological feature for many human diseases, such as Alzheimer’s disease and certain forms of cancers that implicate the tumor suppressor protein p53. Alzheimer’s disease has been widely linked to the aggregation of the amyloid-β peptide, while structural mutations of p53 have been found to cause thermodynamic destabilization, protein misfolding and inhibition of the pro-apoptotic activity of p53 that lead to carcinogenesis. One of the most promising approaches for identifying therapeutically relevant agents against these diseases is the discovery of small-molecule-rescuers of protein misfolding. In order to achieve this, we have developed an integrated bacterial platform for the facile discovery of macrocyclic rescuers of disease-associated protein misfolding. In this system, large combinatorial libraries of cyclic oligopeptides are biosynthesized in Escherichia coli cells and simultaneously screened for their ability to rescue pathogenic protein misfolding and aggregation by utilizing a high-throughput genetic screen based on fluorescence-activated cell sorting. By using this approach we have identified two cyclic peptides with the ability to rescue the misfolding and aggregation of the amyloid-β peptide as well as one cyclic peptide with the ability to stabilise the p53(Y220C) variant and restore its apoptotic activity.