Bepridil and Amiodarone Simultaneously Target the Alzheimer’s Disease β- and γ-Secretase via Distinct Mechanisms
J. Neurosci. 2010 Apr 20. [Epub ahead of print]
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The two proteases beta-secretase and gamma-secretase generate the amyloid beta peptide and are drug targets for Alzheimer’s disease. Here we tested the possibility to target the cellular environment of beta-secretase cleavage instead of the beta-secretase enzyme itself. beta-secretase has an acidic pH optimum and cleaves the amyloid precursor protein in the acidic endosomes. We identified two drugs, bepridil and amiodarone, which are weak bases and are in clinical use as calcium antagonists. Independently of their calcium-blocking activity both compounds mildly raised the membrane-proximal, endosomal pH and inhibited beta-secretase cleavage at therapeutically achievable concentrations in cultured cells, in primary neurons and in vivo in guinea pigs. This shows that an alkalinization of the cellular environment could be a novel therapeutic strategy to inhibit beta-secretase. Surprisingly, bepridil and amiodarone also modulated gamma-secretase cleavage independently of endosomal alkalinization. Thus, both compounds act as dual modulators, which simultaneously target beta- and gamma-secretase through distinct molecular mechanisms. Besides Alzheimer’s disease, compounds with dual properties may also be useful for drug development targeting other membrane proteins.