Characterization of a novel processing pathway for Alzheimer's amyloid β precursor protein

Amyloid β (Aβ) is a normal proteolytic fragment of a large precursor protein (βPP) which undergoes altered conformation, leading to fibril formation. Two main βPP processing pathways have been described, and we are now reporting the characterization of a third βPP pathway. A membrane-associated 16 kDa component identified in human platelets isolated from normal donors. Based on size, immunoreactivity and amino acid sequence analysis, the fragment is a C-terminal βPP component which starts at position 642 (APP₇₇₀ numbering) and contains the intact Aβ sequence. The presence of this novel pathway of βPP processing in resting platelets suggest that it occurs as a normal event.