The identification of neuronal binding partners for human soluble amyloid precursor protein alpha

  • Michael Haycox

Student thesis: Phd


‘Dementia and Alzheimer’s disease’ is the leading cause of death in the UK, so new therapeutic options are of critical importance. One possible therapeutic avenue could be to protect neurons from damage through the use of neuroprotective molecules. The initial cleavage of the amyloid precursor protein (APP) by either α- or β-secretase produces the soluble amyloid precursor protein alpha (sAPPα) or beta (sAPPβ) fragments, respectively. sAPPα binds to neuronal cells in a receptor-dependent manner and is 100-times more neuroprotective than sAPPβ, despite differing by just 16 amino acids at their C-termini. The receptor(s) to which sAPPα binds to facilitate neuroprotection are unknown. Therefore, the identification of new binding partners for sAPPα could have therapeutic relevance. This thesis used two unbiased receptor identification methods to identify sAPPα binding partners in neuronal cells. HEK cell lines stably overexpressing His-tagged sAPPα and sAPPβ were generated. Both recombinant proteins were purified and their identities were confirmed through immunoblotting and GeLC-MS/MS. sAPPα and sAPPβ were shown to bind to induced pluripotent stem cell (iPSC)-derived neurons and SH-SY5Y cells. sAPPα increased the expression of synaptophysin in iPSC-derived neurons. Pre-treatment of SH-SY5Y cells with sAPPα significantly reduced the production of reactive oxygen species following toxic insult in a time-dependent manner. Calsyntenin-1 and calsyntenin-3, type-I transmembrane proteins expressed on the post-synaptic membrane of neurons, were identified in both unbiased receptor identification methods as novel binding partners for sAPPα. Knockdown of calsyntenin-1 did not affect the binding of sAPPα to SH-SY5Y cells; however, knockdown of calsyntenin-3 significantly reduced the binding of sAPPα to SH-SY5Y cells. Overall, the work described in this thesis demonstrated the beneficial effects of sAPPα to reduce oxidative stress in neuronal cells in vitro and identified calsyntenin-3 as a novel binding partner which was required for the binding of sAPPα to neuronal cells. The identification of calsyntenin-1 and calsyntenin-3 as neuronal binding partners for sAPPα may provide new therapeutic targets for neurodegenerative diseases such as Alzheimer’s disease.
Date of Award31 Dec 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorMartin Humphries (Supervisor) & Nigel Hooper (Supervisor)


  • IMAC
  • ROS
  • Neuroprotection
  • QCMD
  • Pulldown
  • Receptor
  • Dementia
  • Amyloid Precursor Protein
  • sAPPβ
  • sAPPα
  • Alcadein
  • Calsyntenin
  • APP
  • iPSC

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