Factors responsible for alpha-Synuclein aggregation.

Aggregation of α-Synuclein (α-Syn) is the hallmark of the pathophysiology of Parkinson's disease. Apart from aggregates, α-Syn can exist in multiple abnormal forms such as oligomers, protofibrils, fibrils amorphous aggregates etc. These forms initiate aggressive, selective and progressive neuronal atrophy through various modes such as mitochondrial dysfunction, lysosomal malfunction, and disruption of calcium homeostasis in various α-Syn-related neurodegenerative disorders. Structurally α-Syn is divided into three domains: N-terminal region made by amino acids1-67 (amphipathic, lysine-rich and interacts with acidic lipid membranes), Non-amyloid-β component (NAC) region made by amino acids 67-95 (hydrophobic region, central to α-syn aggregation) and C-terminal region made by amino acids 96-140 (acidic and proline-rich region responsible for interaction with other proteins). α-Syn follows the pattern of a typical intrinsically disordered protein and lacks a proper folded conformation and exist majorly in a random coil form, though on lipid binding the protein assumes an α-helical structure. The central random coil region of α-Syn is involved in fibril formation transforming into β-sheet rich secondary structures which is a characteristic of amyloids. This chapter entails an elaborate explanation of factors influencing the structure, function and aggregation of α-Syn. Major factors being abnormally high physiological expression of the protein, mutations, posttranslational modifications and also interactions with small molecules such as osmolytes in the cellular milieu. Studying the factors responsible for misfolding and aggregation of α-Syn along with the mechanism involved is crucial to understanding their implications in Parkinson's disease, and will yield valuable insights into disease mechanisms, potential therapeutic strategies.