Research Paper Volume 12, Issue 19 pp 19421—19439

Blockage of AEP attenuates TBI-induced tau hyperphosphorylation and cognitive impairments in rats

Yi Liu1,2, , Cuiping Guo2, , Yi Ding1, , Xiaobing Long3, , Wensheng Li2, , Dan Ke2, , Qun Wang2, , Rong Liu2, , Jian-Zhi Wang2,4, , Huaqiu Zhang3, , Xiaochuan Wang2,4, ,

  • 1 Department of Pathophysiology, Weifang Medical University, Weifang 261053, China
  • 2 Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
  • 3 Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong, University of Science and Technology, Wuhan 430030, China
  • 4 Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, JS, China
* Equal contribution

Received: June 10, 2020       Accepted: June 29, 2020       Published: October 10, 2020
How to Cite

Copyright: © 2020 Liu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Traumatic brain injury (TBI) is regarded as a high-risk factor for Alzheimer's disease (AD). Asparaginyl endopeptidase (AEP), a lysosomal cysteine protease involved in AD pathogenesis, is normally activated under acidic conditions and also in TBI. However, both the molecular mechanism underlying AEP activation-mediated TBI-related AD pathologies, and the role of AEP as an AD therapeutic target, still remain unclear. Here, we report that TBI induces hippocampus dependent cognitive deficit and synaptic dysfunction, accompanied with AEP activation, I2PP2A (inhibitor 2 of PP2A, also called SET) mis-translocation from neuronal nucleus to cytoplasm, an obvious increase in AEP interaction with SET, and tau hyperphosphorylation in hippocampus of rats. Oxygen-glucose deprivation (OGD), mimicking an acidic condition, also leads to AEP activation, SET mis-translocation, PP2A inhibition, tau hyperphosphorylation, and a decrease in synaptic proteins, all of which are abrogated by AEP inhibitor AENK in primary neurons. Interestingly, AENK restores SET back to the nucleus, mitigates tau pathologies, rescuing TBI-induced cognitive deficit in rats. These findings highlight a novel etiopathogenic mechanism of TBI-related AD, which is initiated by AEP activation, accumulating SET in cytoplasm, and favoring tau pathology and cognitive impairments. Lowering AEP activity by AEP inhibitor would be beneficial to AD patients with TBI.


AEP: Asparaginyl endopeptidase; aAEP: activated form of AEP; AENK: AEP inhibitor; TBI: Traumatic brain injury; CTE: Chronic Traumatic Encephalopathy; PP2A: Protein phosphatase-2A; DMSO: Dimethyl sulfoxide; AD: Alzheimer disease; I2PP2A: Inhibitor 2 of PP2A; OGD: Oxygen-glucose deprivation; Aβ: β-amyloid; Co-IP: Co-immunoprecipitation; NFTs: Neurofibrillary tangles; LTP: Long-term potentiation; mNSS: Modified Neurological Severity Score; MWM: Morris water maze; SC: Schaffer collateral; fEPSP: field excitatory postsynaptic potential; HFS: High-frequency stimulation; PSD95: Postsynaptic density protein 95; RvD1: Resolvin D1; aCSF: artificial CSF; PBS: Phosphate buffer saline; BSA: Bovine Serum Albumin; PMSF: Phenylmethylsulfonyl fluoride; SDS: Sodium dodecylsulphate; RIPA: Radio-Immunoprecipitation Assay.