In Vitro Interactions Between Model Proteins and Amyloid Inhibitors

Abstract

Protein folding is an essential requirement for most biological functions. Therefore, if folding of proteins can be specifically modulated, we have the power to tune/inhibit protein function, disease progression, and create novel analytical tools. This is an inter-disciplinary research project that aims to find small molecules that selectively modulate protein-folding reactions. The small molecules used in the study are bicyclic 2-pyridone derivatives . These compounds were originally designed to inhibit the assembly of bacterial pili, and are peptidomimetics that were directed to block the periplasmic chaperone PapD required for pilus biogenesis. A subgroup of these compounds are designed to inhibit the formation of curlin-based bacterial biofilms. Curlicides and pilicides thus are potential new antibiotics to fight bacterial infections. The curlicides bind the major curlin protein CsgA inhibiting its oligomerization into amyloid fibrils Moreover, some of these compounds have been found to inhibit β-amyloid peptide fibrillization. During the project we studied the interactions of some selected compounds with Pseudomas aureginosa azurin (beta-sheet model protein), Borrelia burgdorferi Vlse and human alpha-synuclein. We have found that two of the compounds we have studied, namely FNO75 and its fluorescently labelled analogue CB84 are interacting with VlsE directly, while binding to azurin occurs upon refolding of the protein after heat denaturation. Moreover, wéve tested the effect of the compounds on alpha synuclein fibrillization. Surprisingly, it was found that FNO75, which is known to inhibit curli and beta-fibrillization was speeding up the aggregation of alpha synuclein.