APP and Alzheimer disease: sAPPβ can undergo a further cleavage at APP286 residue to produce N-APP [41], a 35 kDa peptide reported to bind death receptor 6 (DR6, also known as Tumour Necrosis Factor Receptor Superfamily member 21, TNFRSF21) thus triggering apoptosis and axon pruning, but also neuronal death and possibly AD development [42,43].