PIKfyve inhibition blocks endolysosomal escape of α-synuclein fibrils and spread of α-synuclein aggregation

The inter-cellular prion-like propagation of α-synuclein aggregation is emerging as an important mechanism driving the progression of neurodegenerative diseases including Parkinson’s disease and multiple system atrophy (MSA). To discover therapeutic strategies reducing the spread of α-synuclein aggregation, we performed a genome-wide CRISPR interference screen in a human cell-based model. We discovered that inhibiting PIKfyve dramatically reduced α-synuclein aggregation induced with both recombinant α-synuclein fibrils and fibrils isolated from MSA patient brain. While PIKfyve inhibition did not affect fibril uptake or α-synuclein clearance or secretion, it reduced α-synuclein trafficking from the early endosome to the lysosome, thereby limiting fibril escape from the lysosome and reducing the amount of fibrils that reach cytosolic α-synuclein to induce aggregation. These findings point to the endolysosomal transport of fibrils as a critical step in the propagation of α-synuclein aggregation and a potential therapeutic target. ### Competing Interest Statement The authors have declared no competing interest.