Biological functions of α-synuclein and its role in Parkinson’s disease

α-Synuclein is identified as a constant component of dopaminergic neuronal pale eosinophilic inclusions "the Lewy bodies" in Parkinson’s disease. In fact, normal α-synuclein has lots of biological functions, which regulates synaptic plasticity, integrates presynaptic signaling, regulates dopamine level in the synapse, modulates microglial activation and lipid metabolism, and exerts heat shock protein-like function. However, abnormal α-synuclein leads to pathological lesion. Many studies show that pathological α-synuclein levels are elevated under the condition of its gene mutation, certain posttranslational modifications, dysfunction of molecular chaperones or ubiquitin proteasome system. The pathological α-synuclein plays an important role in neurodegeneration, in particular, Parkinson’s disease because it interrupts integrity of synaptic vesicles, ER-Golgi traffic and axonal transport, inhibits histone acetylation and chaperone-mediated autophagy, stabilizes itself against proteasomal degradation, and leads to neuroinflammation and abnormal phosphorylation of tau.