α-Synuclein Oligomers Impair Neuronal Microtubule-Kinesin Interplay

Early -synuclein (-Syn)-induced alterations are neurite pathologies resulting in Lewy neurites. -Syn oligomers are a toxic species in synucleinopathies and are suspected to cause neuritic pathology. To investigate how -Syn oligomers may be linked to aberrant neurite pathology, we modeled different stages of -Syn aggregation in vitro and investigated the interplay of -Syn aggregates with proteins involved in axonal transport. The interaction of wild type -Syn (WTS) and -Syn variants (E57K, A30P, and aSyn(30-110)) with kinesin, tubulin, and the microtubule (MT)-associated proteins, MAP2 and Tau, is stronger for multimers than for monomers. WTS seeds but not -Syn oligomers significantly and dose-dependently reduced Tau-promoted MT assembly in vitro. In contrast, MT gliding velocity across kinesin-coated surfaces was significantly decreased in the presence of -Syn oligomers but not WTS seeds or fibrils (aSyn(30-110) multimers). In a human dopaminergic neuronal cell line, mild overexpression of the oligomerizing E57K -Syn variant significantly impaired neurite network morphology without causing profound cell death. In accordance with these findings, MT stability, neuritic kinesin, and neuritic kinesin-dependent cargoes were significantly reduced by the presence of -Syn oligomers. In summary, different -Syn species act divergently on the axonal transport machinery. These findings provide new insights into -Syn oligomer-driven neuritic pathology as one of the earliest events in synucleinopathies.