Presenilin-1 and -2 Are Molecular Targets for γ-Secretase Inhibitors*

Presenilins are integral membrane protein involved in the production of amyloid β-protein. Mutations of the presenilin-1 and -2 gene are associated with familial Alzheimer's disease and are thought to alter γ-secretase cleavage of the β-amyloid precursor protein, leading to increased production of longer and more amyloidogenic forms of Aβ, the 4-kDa β-peptide. Here, we show that radiolabeled γ-secretase inhibitors bind to mammalian cell membranes, and a benzophenone analog specifically photocross-links three major membrane polypeptides. A positive correlation is observed among these compounds for inhibition of cellular Aβ formation, inhibition of membrane binding and cross-linking. Immunological techniques establish N- and C-terminal fragments of presenilin-1 as specifically cross-linked polypeptides. Furthermore, binding of γ-secretase inhibitors to embryonic membranes derived from presenilin-1 knockout embryos is reduced in a gene dose-dependent manner. In addition, C-terminal fragments of presenilin-2 are specifically cross-linked. Taken together, these results indicate that potent and selective γ-secretase inhibitors block Aβ formation by binding to presenilin-1 and -2.