Cleavage of tau by asparagine endopeptidase mediates the neurofibrillary pathology in Alzheimer’s disease

Neurofibrillary tangles (NFTs), composed of truncated and hyperphosphorylated tau, are a common feature of numerous aging-related neurodegenerative diseases including Alzheimer’s disease (AD). However, the molecular mechanisms mediating tau truncation and aggregation during aging remain elusive. Here we show that asparagine endopeptidase (AEP), a lysosomal cysteine proteinase, is activated during aging and proteolytically degrades tau, abolishes its microtubule assembly function, induces tau aggregation, and triggers neurodegeneration. AEP is upregulated and active during aging, and is activated in tau P301S transgenic mice and human AD brain, leading to tau truncation in NFTs. Deletion of AEP from tau P301S transgenic mice substantially reduces tau hyperphosphorylation, alleviates the synapse loss and rescues impaired hippocampal synaptic function and the cognitive deficits. Infection of uncleavable tau N255AN368A mutant rescues tau P301S-induced pathological and behavioral defects. Together, these observations indicate that AEP acts as a crucial mediator of tau-related clinical and neuropathological changes in neurodegenerative diseases. Inhibition of AEP may be therapeutically useful for treating tau-mediated neurodegenerative diseases.