MOLECULAR DETERMINANTS UNDERLYING PROTEIN MISFOLDING AND AGGREGATION

Proteins have evolved to adopt distinctive and well-defined functional states under physiological conditions, either as monomers or complexes. The achievement of a three-dimensional structure allows proteins to exert their physiological functions. Nevertheless, when proteins lose – or fail to acquire – their spatial organization, they can convert into aggregated species that can be harmful to the organism. Conformational diseases gather all those pathologies characterized by the misfolding and aggregation of proteins. Indeed, while the formation and deposition of proteinaceous aggregates can be toxic to cells, the lack of active folded protein disrupts normal physiological pathways. Although considerable progresses have been made in the recent years, to date conformational diseases are still incurable. Indeed, the incomplete understanding of the causes guiding protein misfolding and aggregation prevents the development of efficient treatments. At the same time, the complexity and the diversity of the processes leading to the formation of aggregated species make the task extremely challenging. This PhD project was developed to provide a more comprehensive overview of the molecular bases underlying the conversion of soluble and functional states into aggregated and potentially toxic species. To reach such aims, we applied an integrative approach on two model systems, neuroserpin (NS) and beta-2 microglobulin (2m). In particular, we combined a series of biophysical, biochemical and structural techniques to study these two proteins which have been largely used as model systems for serpin polymerization and amyloid formation, respectively. We found that protein misfolding and aggregation processes depend on several molecular properties, including primary sequence, denatured state compactness, thermal stability, ability to form oligomers under physiological conditions, and the presence of post-translation modifications. The data presented in this PhD thesis add valuable information to depict the complex framework of protein misfolding and aggregation.