| Type: | Family | Name: | Amyloid beta A4 protein |
| Description: | Amyloid beta A4 protein (also known as APP or A4) consists of a large N-terminal extracellular region containing heparin-binding and copper-binding sites, a short hydrophobic transmembrane domain, and a short C-terminal intracellular domain. The N-terminal region is similar in structure to cysteine-rich growth factors and appears to function as a cell surface receptor, contributing to neurite growth, neuronal adhesion, axonogenesis and cell mobility []. There are several alternative splicing isoforms of APP in humans. Two of the main isoforms, amyloid-beta40 (Abeta40) and amyloid-beta42 (Abeta42), are found prominently in the extracellular brain deposits associated with Alzheimer's disease (AD) []. The ratio of Abeta42 to Abeta40 affects the pathogenesis of AD []. APP can be processed by different sets of enzymes:In the non-amyloidogenic (non-plaque-forming) pathway, APP is cleaved by alpha-secretase to yield a soluble N-terminal sAPP-alpha (neuroprotective) and a membrane-bound CTF-alpha. CTF-alpha is broken-down by presenilin-containing gamma-secretase to yield soluble p3 and membrane-bound AICD (nuclear signalling). In the amyloidogenic pathway (plaque-forming), APP is broken down by beta-secretase to yield soluble sAPP-beta and membrane-bound CTF-beta. CTF-beta is broken down by gamma-secretase to yield soluble amyloid-beta and membrane-bound AICD. Amyloid-beta is required for neuronal function, but can aggregate to form amyloid plaques that seem to disrupt brain cells by clogging points of cell-cell contact. | Short Name: | APP |
