Accumulation of amyloid precursor fragment in Alzheimer plaques

Abstract

Regenerative and degenerative neurites are components of classical senile plaques found in brain tissue of patients with Alzheimer's disease (AD). Amyloid β/A4-protein derived from its precursor, amyloid β/A4-protein precursor (APP/ABPP), constitutes the major portion of the amyloid core of senile plaques. A large N-terminal portion of APP (∼Mr 100,000) is released from cells, leaving a minor C-terminal portion (∼Mr 15,000) behind. A series of antisera against various sequences of APP were prepared and used to study the localization of each sequence in brain tissue. Plaque neurites stained as intensely as neuronal cell bodies with three antisera against the N-terminal portion of APP (N-terminal to a.a. 225), whereas five other antisera directed against the other C-terminal portions of APP (a.a. 284 to C-terminal) and antisera against the Kunitz-type protease inhibitor portion of APP stained plaque neurites less intensely than neuronal cell bodies in the hippocampus. These results suggest that a major part of the APP present in the neuritic component of senile plaques is a fragment representing the N-terminal one-third of the molecule.