SynCAR platform for capturing neuronal synaptic proteopathic seeds

Synaptic proteins are critical for maintaining healthy neuronal transmission but can also drive prion-like trans -synaptic spreading of pathological aggregated proteins found in many neurodegenerative diseases, including Alzheimer's disease. Recognizing technological limitations for in situ identification of synaptic proteins, we built a modular synaptic chimeric antigen receptor (synCAR) for capture of synaptic proteins by fusing a single-chain antibody fragment with the post-synaptic protein neurolignin-1 ( NLGN1 ). Using our synCAR platform, we show that anchoring the tau antibody PHF1 to the synapse effectively captures pathogenic synaptic tau species. Expressing PHF1 synCAR at synapses in mouse primary and human neuronal tau seeding models results in increased tau aggregation, likely due to concentrating pathological tau seeds at the synapse. These findings provide the first published method for the isolation and modulation of synaptic protein function within relevant biological contexts, highlighting synCAR as a relevant instrumental platform for synaptic protein research and neurodegenerative disease drug development.