Secondary nucleation of α-Synuclein drives Mitochondria dysfunctions and Lewy body formation in Parkinson's Disease

The seeding of -Synuclein (Syn) is a key driver of Lewy pathology propagation in Parkinsons disease (PD) and forms the basis for recent diagnostic advances. However, it remains unclear how the structural and biochemical features of Syn seeds dictate their propagation efficiency, capacity to induce Lewy body formation, and resulting cellular toxicity. Using genetic and idiopathic PD cell models, we map the pathogenic cascade beginning with the seed-driven conversion of endogenous Syn, followed by impaired degradation, mitochondrial dysfunction, and ultimately Lewy body formation. By coupling kinetic modelling of aggregation with functional readouts, we identify secondary nucleation as the predominant mechanism generating toxic Syn aggregation intermediates, identifying the critical process that links seeding to pathology. Extending this framework to PD brain, we quantitatively correlate seeding capacity with the spatiotemporal spread and severity of Lewy pathology, revealing a mechanistic connection between Syn aggregation dynamics and disease progression at molecular, cellular, and anatomical levels. By unifying molecular mechanism with clinicopathological progression, our work identifies catalytic Syn fibrillar seeds as tractable targets for both disease-modifying therapy and biomarker development in PD. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=193 HEIGHT=200 SRC="FIGDIR/small/676873v1_ufig1.gif" ALT="Figure 1"> View larger version (79K): org.highwire.dtl.DTLVardef@1eca299org.highwire.dtl.DTLVardef@a714d4org.highwire.dtl.DTLVardef@1486db5org.highwire.dtl.DTLVardef@1aa895_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LISyn fibril-oligomer interplay drives mitochondrial abnormalities and Lewy pathology C_LIO_LIFibrillar Syn catalyse toxic aggregate formations via secondary nucleation C_LIO_LIPhosphorylated Syn evades lysosomal clearance and drives enhanced dysfunctions C_LIO_LISeeding capacity of Syn predicts Lewy pathology burden and disease progression C_LI