Hypothesis 1: Specific CSF lipoprotein components, especially ApoE- and clusterin-rich particles, bind alpha-synuclein fibril surfaces and stabilize disease-relevant polymorphs by modulating surface hydration and lateral packing. Test: reconstitute fibrils with purified ApoE or CLU fractions and compare cryo-EM class distributions and seeding potency.
Hypothesis 2: Extracellular vesicle membranes and ganglioside-rich lipid fragments in CSF provide the structural cofactor that preserves a brain-derived fibril conformation outside cells. This predicts that vesicle depletion or ganglioside digestion will shift fibril morphology and reduce conformational fidelity. Test: EV fractionation, lipidomics, and serial seeding with morphology readouts.
Hypothesis 3: Sulfated glycans and low-abundance metal-binding proteins in CSF act as molecular braces that stabilize a subset of fibril polymorphs through electrostatic cross-bridging. Test: glycosaminoglycan depletion, divalent cation chelation, and mass spectrometry of fibril-bound CSF proteins.