Strain-Distinct α-Synuclein and Tau Cross-Seeding Uncovered by Correlative Approach with Optical Photothermal...

Area of Science:

• Neurobiology
• Biochemistry
• Structural Biology

Background:

• Alpha-synuclein (αSyn) and Tau pathologies coexist in synucleinopathies and tauopathies, indicating complex protein interactions.
• Cross-seeding of αSyn and Tau leads to diverse amyloid structures with implications for biological function.
• Current methods lack the resolution to differentiate amyloid structural polymorphs within living cells.

Purpose of the Study:

• To characterize structural rearrangements of αSyn inclusions cross-seeded by αSyn and Tau preformed fibrils (PFFs) directly within cells.
• To investigate the influence of different PFF compositions on αSyn aggregation and cellular inclusion formation.
• To provide subcellular-resolution structural imaging of amyloid proteins in their native cellular environment.

Main Methods:

• Utilized a correlative approach combining submicron optical photothermal infrared (O-PTIR) microspectroscopy and confocal microscopy.
• Synthesized hybrid PFFs from αSyn and two Tau isoforms (Tau3R and Tau4R).
• Analyzed the composition and structural features of newly formed αSyn inclusions within cells.

Main Results:

• Hybrid PFFs showed variations in αSyn and Tau composition.
• αSyn and Tau3R polymorphs exhibited the highest β-sheet content and seeding potency, leading to increased cellular phosphorylation.
• Cellular inclusions inherited structural motifs from donor seeds and displayed distinct spatial and structural evolution.

Conclusions:

• Cellular inclusions inherit structural characteristics from their initiating seeds.
• αSyn/Tau PFFs induce divergent mechanisms of αSyn aggregation, forming distinct structural polymorphs.
• This study provides novel insights into the structural heterogeneity of amyloids in vivo.