Alzheimer’s disease (AD) is a currently incurable disease. The amyloid hypothesis on causation relates to amyloid precursor protein (APP) which is processed to release soluble APP (α or β) (sAPP) and possibly amyloid β (Aβ) peptides. The Aβ can then form amyloid plaques and are neurotoxic in the brain, newly approved antibodies target Aβ but are not a cure. sAPPα is another possibility predominantly released by ADAM10 processing of APP and has been linked to many neuroprotective/neuroproliferative effects. The objective of this research is to examine the role of APP processing in AD cell models and explore therapies to enhance sAPPα.
Fibrates have previously been used to increase sAPPα release and we tested this in the AD-related cell model Swedish mutant APP695 (SweAPP)-SH-SY5Y. However, the fibrates were found to not enhance release of sAPPα via ADAM10 expression. Subsequently, APP processing was examined for Mock-, wild-type APP695- (wtAPP-), SweAPP- and BACE1-transfected SH-SY5Y Cells, where BACE1 is responsible for amyloidogenic processing of APP to release sAPPβ and Aβ-peptides.
It was found that the non-amyloidogenic release of sAPP was unaffected by batimastat (ADAM inhibitor) in SH-SY5Y-BACE1 cells, which could be due to the release of sAPPβ prime (sAPPβ’) by BACE1. By transfecting Mock- and BACE1-SH-SY5Y cells with sAPPα and sAPPβ’ constructs, the sAPPα/sAPPβ’ axis was shown to rescue the SH-SY5Y-BACE1 cell viability and highlighted the importance of sAPPα release to the cell.
Further work is required to generate a functioning Tet-On system to create an inducible mammalian expression system to selectively overexpress sAPPα.