Molecular neuropathology of Alzheimer's disease.

Alzheimer's disease (AD) is caused by the aberrant metabolism of the amyloid precursor protein (APP) and is consequently associated with the accumulation of one of its degradation products, the beta A4 amyloid protein. The proteases (secretases) which generate beta A4 from APP are now being defined, as is the normal function of APP. How neurons degenerate in AD remains unexplained, but is of central importance in developing new therapeutic approaches. While the genetic factors which contribute to the aberrant metabolism of APP are now being elucidated, the environmental factors which exacerbate this process are unknown.