Glucosylceramide induced ectosomes propagate pathogenic α-synuclein in Parkinson’s disease

Intercellular transmission of α-synuclein contributes to Parkinson’s disease pathology. Yet, the mechanisms of α-synuclein spread are not fully understood. Here, we used live-cell microscopy to examine the impact of Parkinson’s disease associated lipid alterations on α-synuclein release. We discovered that increased glucosylceramides induce ectosome shedding from primary neurons, and from dopaminergic neurons derived from Parkinson’s disease patient iPSCs harboring mutations in GBA1 (N370S, L444P and W378G) and LRRK2 (G2019S and R1441H) compared to their isogenic control. We show that elevated glucosylceramide similarly increases vesicle release and uptake by other neurons in living mouse brains using 2-photon microscopy. Finally, we show that ectosomes are loaded with pathogenic α-synuclein and lead to the transmission of α-synuclein pathology to neighbouring neurons. These data reveal ectosomes as the predominant route for α-synuclein transmission that can only be appreciated by live-cell imaging technologies.