α-Synuclein (ASN) is richly abundant in the central nervous system, particulary in pre- synaptic terminals. Among many functions, ASN plays a crucial role in regulation of dopaminergic system. In physiological conditions, soluble ASN is involved in maintenance of dopamine (DA) homeostasis in the central nervous system. This protein regulates DA level and biosynthesis by inhibition of the tyrosine hydroxylase. It also influences DA storage and release from synaptic ve- sicles as well as DA uptake by its transporter (DAT).

Synucleins are a family of small (15–20 kDa), soluble, conserved proteins that are predominan- tly expressed in neurons and include α-, β-, γ-Synuclein and Synoretine. Among the synuclein family exclusively α-Synuclein is the precursor protein for highly hydrophobic 35-amino acid peptide NAC (non-amyloid β component of Alzheimer’s disease plaques). This presynaptic protein associated with synaptic vesicles is also present in cytosol. Under physiological conditions α-Synuclein is natively unfolded.