Deposits of amyloid protein in senile plaques near nerve processes are found in the brains of aged humand and cases of Alzheimer's Disease. The principle component of this extracellular amyloid is beta A4, a 4 kDa peptide derived from a larger amyloid precursor protein (APP), which is widely expressed in the brain and body. The creation, transport and function of these proteins is currently an active area of research.