Regulation of proteolytic processing of the amyloid beta-protein precursor by first messengers. A novel potential approach for the treatment of Alzheimer's disease.

Amyloid deposits in Alzheimer's disease brains consist of aggregated amyloid beta-peptides (A beta) which are derived by proteolytic processing of the amyloid beta-protein precursor (APP). Proteolytic APP processing can be regulated by the activity of neuronal cell surface receptors including the muscarinic m1 and m3, the serotoninergic 5-HT2 and 5-HT1C, vasopressin and bradykinin receptor subtypes. Receptor stimulation with appropriate agonists rapidly increases the rates of release of the alpha-secretase processing product APPs which is cleaved within the A beta domain and thus is a non-amyloidogenic derivative. Moreover, stimulation of m1 receptors also decreases the formation of A beta, a secreted potentially amyloidogenic and possibly neurotoxic APP fragment. Similar biochemical events occur in stimulation experiments of fresh rat brain slices suggesting that neuronal activity may be involved in regulating APP processing in mammalian brain. Activation of non-amyloidogenic APP processing and inhibition of amyloidogenic processing pathways by subtype-specific agonists of muscarinic, serotoninergic or peptidergic receptors provides a novel approach for the pharmacological modulation of APP processing in Alzheimer's disease.