The precursor of the non-Abeta component of Alzheimer's disease amyloid (NACP) (also known as alpha-synuclein) is a presynaptic terminal molecule that abnormally accumulates in the plaques of Alzheimer's disease (AD) and in the Lewy bodies (LBs) of Lewy body variant of AD, diffuse Lewy body disease, and Parkinson's disease.