Figure 3. A schematic representation of beta-amyloid pathway that leads to AD pathology. The cleavage of APP of β-secretase and subsequently by γ -secretase results in the production of an amyloid plaque. The nonpathogenic (nonamyloidogenic pathway) is initiated by α-secretase releasing sAPPα into the intracellular space. The resulting CTF-α fragment is cleaved by γ -secretase in the intermembrane space resulting in both the AICD and p3 fragments that are both non-plaque forming elements. The pathogenic (amyloidogenic pathway) initiated by β-secretase and resulted in sAPP-β release externally. The remaining CTF-β fragment is cleaved by γ -secretase and releases Aβ_38-42 amino acid amyloid monomers. The externally released Aβ fragment forms toxic oligomers and eventually packaged in amyloid plaques.