EVIDENCE THAT BETA-AMYLOID PROTEIN IN ALZHEIMERS-DISEASE IS NOT DERIVED BY NORMAL PROCESSING

The β-amyloid protein (β/A4), derived from a larger amyloid precursor protein (APP), is the principal component of senile plaques in Alzheimer's disease. APP is an integral membrane glycoprotein and is secreted as a carboxyl-terminal truncated molecule. APP cleavage, which is a membrane-associated event, occurred at a site located within the β/A4 region. This suggests that an intact amyloidogenic β/A4 fragment is not generated during normal APP catabolism. Therefore, an early event in amyloid formation may involve altered APP processing that results in the release and subsequent deposition of intact β/A4.