Interplay between α-synuclein, lipid membrane and DOPAC: A tripartite system against the progression of Parkinson disease

Parkinson's disease (PD) is a neurodegenerative disorder associated with the degeneration of dopaminergic neurons in the substantia nigra pars-compacta. It is characterized by the presence of Lewis Bodies (LBs) inclusions. The major constituent of LBs are the fibrillar aggregates of α-synuclein (aSyn). aSyn is an intrinsically disordered protein, highly abundant in pre-synaptic neurons where it is involved in synaptic vesicle traffic and turnover. aSyn is a peripheric-membrane protein which exists in an equilibrium between the free random coil structure and the membrane bound α-helix structure. Dopamine metabolites are currently studied for their ability to inhibit aSyn fibrillization and to induce the formation of off-pathway non-toxic oligomers. In this Thesis project, aSyn interaction with biological membranes is studied. The effects of DOPAC, a dopamine metabolism intermediate, on the aSyn free/bound to liposome equilibrium were investigated to pinpoint the structural changes induced by the catechol. aSyn structural modification caused by DOPAC was investigated by using wild type (WT) and E46K familiar mutant (E46K) forms. To mimic physiological and pathological conditions, both monomeric and oligomeric forms were incubated with liposomes and DOPAC. The tripartite system was analysed using Circular Dichroism (CD), Isothermal Titration Calorimetry (ITC), limited proteolysis, Hydrogen-Deuterium Exchange mass spectrometry (HDX-MS) and Native mass spectrometry (Native MS). In conclusion, the final aim of this project was to identify the basis of the interaction of aSyn with biological membranes and DOPAC by using innovative biochemical and biophysical technologies. The results of this study may contribute to a deeper understanding in the DOPAC anti-aggregating proprieties and its ability to interfere with aSyn folding process. Furthermore, this may highlight fundamental proprieties for the development of PD inhibitors.

Parkinson's disease (PD) is a neurodegenerative disorder associated with the degeneration of dopaminergic neurons in the substantia nigra pars-compacta. It is characterized by the presence of Lewis Bodies (LBs) inclusions. The major constituent of LBs are the fibrillar aggregates of α-synuclein (aSyn). aSyn is an intrinsically disordered protein, highly abundant in pre-synaptic neurons where it is involved in synaptic vesicle traffic and turnover. aSyn is a peripheric-membrane protein which exists in an equilibrium between the free random coil structure and the membrane bound α-helix structure. Dopamine metabolites are currently studied for their ability to inhibit aSyn fibrillization and to induce the formation of off-pathway non-toxic oligomers. In this Thesis project, aSyn interaction with biological membranes is studied. The effects of DOPAC, a dopamine metabolism intermediate, on the aSyn free/bound to liposome equilibrium were investigated to pinpoint the structural changes induced by the catechol. aSyn structural modification caused by DOPAC was investigated by using wild type (WT) and E46K familiar mutant (E46K) forms. To mimic physiological and pathological conditions, both monomeric and oligomeric forms were incubated with liposomes and DOPAC. The tripartite system was analysed using Circular Dichroism (CD), Isothermal Titration Calorimetry (ITC), imited proteolysis, Hydrogen-Deuterium Exchange mass spectrometry (HDX-MS) and Native mass spectrometry (Native MS). In conclusion, the final aim of this project was to identify the basis of the interaction of aSyn with biological membranes and DOPAC by using innovative biochemical and biophysical technologies. The results of this study may contribute to a deeper understanding in the DOPAC anti-aggregating proprieties and its ability to interfere with aSyn folding process. Furthermore, this may highlight fundamental proprieties for the development of PD inhibitors.