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Description

Amyloid-beta A4 protein (UniProt: P05067, also known as ABPP, APPI, APP, Alzheimer disease amyloid protein, Amyloid precursor protein, Amyloid-beta precursor protein, Cerebral vascular amyloid peptide, CVAP, PreA4, Protease nexin-II, PN-II) is encoded by the APP (also known as A4, AD1) gene (Gene ID: 351) in human. APP undergoes extensive post-translational modification including glycosylation, phosphorylation, and tyrosine sulfation, as well as many types of proteolytic processing to generate peptide fragments. APP is proteolytically processed under normal cellular conditions by alpha-secretase or beta-secretase to generate and release soluble APP peptides, S-APP-alpha and S-APP-beta, and the retention of corresponding membrane-anchored C-terminal fragments, C80, C83 and C99. Subsequent processing of C80 and C83 by gamma-secretase yields P3 peptides. In Alzheimer s disease processing of C99 generates amyloid-beta 40 (Abeta40) and amyloid-beta 42 (Abeta42) that form amyloid plaques. Beta-amyloid peptides are lipophilic metal chelators with metal-reducing activity. They bind transient metals such as copper, zinc and iron. APP can also be cleaved by caspases during neuronal apoptosis. Cleavage at Asp-739 by either caspase-6, -8 or -9 results in the production of the neurotoxic C31 peptide and the increased production of beta-amyloid peptides. In addition to its obvious role in Alzheimer's disease, the most-substantiated role for APP is in synaptic formation and repair. Its expression is upregulated during neuronal differentiation and after neural injury.