Pathogenic Mechanisms of Cytosolic and Membrane-Enriched α-Synudein Converge on Fatty Acid Homeostasis

-alpha-Synuclein (alpha S) plays a key role in Parkinson's disease. Although Parkinson's disease is typically sporadic, inherited alpha S missense mutations provide crucial insights into molecular mechanisms. Here, we examine two clinical mutants, E46K and G51D, which are both in the conserved N-terminus that mediates transient alpha S-membrane interactions. However, E46K increases and G51D decreases alpha S-membrane interactions. Previously, we amplified E46K via the 11-residue repeat motifs, creating 3K (E35K+E46K+E61K). Here, we engineered these motifs to amplify G51D (V40D+G51D+V66D = 3D) and systematically compared E46K/3K versus G51D/3D. We found that 651D increased cytosolic alpha S in neural cells and 3D aggravates this. G51D, and 3D even more, reduced alpha S multimer-to-monomer (0660:0614) ratio. Both amplified variants caused cellular stress in rat primary neurons and reduced growth in human neuroblastoma cells. Importantly, both 3K- and 3D-induced stress was ameliorated by pharmacologically inhibiting stearoyl-CoA desaturase or by conditioning the cells in palmitic (16:0) or myristic (14:0) acid. SCD inhibition lowered lipid-droplet accumulation in both 3D- and 3K-expressing cells and benefitted G51D by normalizing multimer:monomer ratio, as reported previously for E46K. Our findings suggest that, despite divergent cytosol/membrane partitioning, both G51D and E46K neurotoxicity can be prevented by decreasing fatty-acid unsaturation as a common therapeutic approach.

Automated summary

Alpha-synuclein plays a key role in Parkinson's disease. Missense mutations in the conserved N-terminus of the protein affect its interaction with the cell membrane. Two clinical mutants, E46K and G51D, were studied and compared. Both mutants showed altered membrane interactions, with E46K increasing and G51D decreasing the interactions. Cellular stress and reduced growth were observed in neurons and neuroblastoma cells expressing the mutants. The study suggests that reducing fatty-acid unsaturation could be a potential therapeutic strategy for preventing neurotoxicity in both E46K and G51D mutants.