Amyloid beta (Aβ or Abeta) is a peptide of 36–43 amino acids that is processed from the Amyloid precursor protein. While best known as a component of amyloid plaques in association with Alzheimer's disease, evidence has been found that Aβ is a highly multifunctional peptide with significant non-pathological activity. Aβ is the main component of deposits found in the brains of patients with Alzheimer's disease. Several potential activities have been discovered for Aβ that are not associated with disease, including activation of kinase enzymes, protection against oxidative stress, regulation of cholesterol transport, functioning as a transcription factor, and anti-microbial activity (potentially associated with Aβ's pro-inflammatory activity). Aβ is the main component of amyloid plaques (deposits found in the brains of patients with Alzheimer's disease). Similar plaques appear in some variants of Lewy body dementia and in inclusion body myositis (a muscle disease), while Aβ can also form the aggregates that coat cerebral blood vessels in cerebral amyloid angiopathy. The plaques are composed of a tangle of regularly ordered fibrillar aggregates called amyloid fibers, a protein fold shared by other peptides such as the prions associated with protein misfolding diseases. Recent research suggests that soluble oligomeric forms of the peptide may be causative agents in the development of Alzheimer's disease. A number of genetic, cell biology, biochemical and animal studies support the concept that Aβ plays a central role in the development of Alzheimer’s disease pathology. Brain Aβ is elevated in patients with sporadic Alzheimer’s disease. Aβ is the main constituent of brain parenchymal and vascular amyloid, it contributes to cerebrovascular lesions and is neurotoxic. It is unresolved how Aβ accumulates in the central nervous system and subsequently initiates the disease of cells. Significant efforts have been focused on the mechanisms responsible for Aβ production, including the proteolytic enzymes alpha- and ß-secretases which generate Aβ from its precursor protein, APP (amyloid precursor protein). Aβ circulates in plasma, cerebrospinal fluid (CSF) and brain interstitial fluid (ISF) mainly as soluble Aβ40 Senile plaques contain both Aβ40 and Aβ42, while vascular amyloid is predominantly the shorter Aβ40. Several sequences of Aβ were found in both lesions. Generation of Aβ in the CNS may take place in the neuronal axonal membranes after APP-mediated axonal transport of ß-secretase and presenilin-1. Aβ is formed after sequential cleavage of the amyloid precursor protein (APP), a transmembrane glycoprotein of undetermined function. APP can be processed by α-, β- and γ-secretases; Aβ protein is generated by successive action of the β and γ secretases. The γ secretase, which produces the C-terminal end of the Aβ peptide, cleaves within the transmembrane region of APP and can generate a number of isoforms of 36-43 amino acid residues in length. The most common isoforms are Aβ40 and Aβ42; the shorter form is typically produced by cleavage that occurs in the endoplasmic reticulum, while the longer form is produced by cleavage in the trans-Golgi network. The Aβ40 form is the more common of the two, but Aβ42 is the more fibrillogenic and is thus associated with disease states. *** possibly CHANGE LABEL TO 'amyloid beta (A4) precursor protein' ***

http://purl.obolibrary.org/obo/ND_0005015

http://en.wikipedia.org/wiki/Beta_amyloid

http://pir.georgetown.edu/cgi-bin/pro/entry_pro?id=PR:000004168

http://purl.obolibrary.org/obo/ND_00055012