APP and Alzheimer disease: The death of neurons, a prominent feature of AD, has been associated with the release of oligomeric intracellular Aβ-42 into the surrounding tissue, which may stimulate the production of amyloidogenic fragments of APP, amplify the levels of intracellular Aβ in neighbouring cells, and act as a nidus for the deposition of secreted Aβ[29, 30].