APP and Alzheimer disease: The γ-secretase enzyme complex cleaves many type I transmembrane proteins, including the amyloid-β (Aβ) precursor protein APP (known to be involved in neuronal amyloid plaque formation in Alzheimer's disease [AD]), NOTCH1-4, neuregulin, low-density lipoprotein receptor related protein (LRP1, 2 and 8) and N-cadherin [10], [11].