Nontoxic amyloid beta peptide (1-42) suppresses acetylcholine synthesis - Possible role in cholinergic dysfunction in Alzheimer's disease

We show here that amyloid beta peptide(1-42) (A beta(1-42)) may play a key role in the pathogenesis of the cholinergic dysfunction seen in Alzheimer's disease (AD), in addition to its putative role in amyloid plaque formation. A beta(1-42) freshly solubilized in water (non-aged A beta(1-42)), which was not neurotoxic without preaggregation, suppressed acetylcholine (ACE) synthesis in cholinergic neurons at very low concentrations (10-100 nM), although non-aged A beta(1-40) was ineffective. Non-aged A beta(1-42) impaired pyruvate dehydrogenase (PDH) activity by activating mitochondrial tau protein kinase I/glycogen synthase kinase-3 beta, as we have already shown in hippocampal neurons (Hoshi, M., Takashima, A. Noguchi, K., Murayama, M., Sato, M., Hondo, S., Saitoh, Y., Tshiguro, K., Hoshino, T., and Imahori, K. (1996) Proc. Natl. Acad. Sci. U. S. A 93, 2719-2723). Neither choline acetyltransferase activity nor choline metabolism was affected. Therefore, the major cause of reduced ACh synthesis was considered to be an inadequate supply of acetyl-CoA owing to PDH impairment. Soluble A beta(1-42) increases specifically in AD brain (Kuo, Y.-M., Emmerling, M. R., Vigo-Pelfrey, C., Kasunic, T. C., Kirkpatrick, J. B., Murdoch, G. H., Ball, M. J., and Roher, A. E. (1996) J. Biol. Chem. 271, 4077-4081). This increase in soluble A beta(1-42) may disturb cholinergic function, leading to the deterioration of memory and cognitive function that is characteristic of AD.