Alpha-Synuclein Neurobiology in Parkinson's Disease: A Comprehensive Review of Its Role, Mechanisms, and Therapeutic Perspectives.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra (SN) and the presence of intracellular α-synuclein (αSyn) aggregates known as Lewy bodies (LB). αSyn, a presynaptic protein, is believed to play a crucial role in synaptic function, neurotransmitter release, and neuronal plasticity. However, its misfolding and aggregation are thought to be central to PD pathogenesis. This review provides a comprehensive analysis of αSyn's role in PD, exploring its normal physiological functions, pathological mechanisms, and therapeutic potential. The pathological transformation of αSyn involves structural alterations that promote oligomerization and fibrillization, leading to toxic gain-of-function effects. These aggregates disrupt cellular homeostasis through mechanisms including mitochondrial dysfunction, oxidative stress, lysosomal impairment, and endoplasmic reticulum stress. Furthermore, pathogenic αSyn is thought to exacerbate neurodegeneration via prion-like spread along interconnected neuronal circuits. Emerging evidence highlights the frequent co-occurrence of other proteinopathies, such as tau and amyloid-β, which may synergistically accelerate disease progression. Targeting αSyn has emerged as a potential therapeutic strategy. Approaches such as immunotherapy, small-molecule inhibitors, gene silencing, and modulation of protein degradation pathways (e.g., autophagy and proteasomal systems) are actively being explored. Additionally, lifestyle-based interventions, particularly exercise, have shown neuroprotective effects, potentially mediated by irisin-a myokine implicated in protein clearance and synaptic resilience-underscoring the importance of multimodal strategies in PD management.