The functional γ-secretase inhibitor prevents production of amyloid β 1–34 in human and murine cell lines

Abstract

The amyloid precursor protein (APP) undergoes two consecutive cleavages by different proteases, β-secretase and γ-secretase, leading to the release of an amyloidogenic 4 kDa fragment called amyloid β (Aβ). Combining immunoprecipitation and mass spectrometry, we characterized soluble Aβ in cultured cell media of mouse neuroblastoma N2a cells and double hAPP/hBACE-1 transfected HEK293. The major Aβ isoforms detected were Aβ11–34, Aβ1–34, Aβ11–40 and Aβ1–40. In this study, we demonstrate that overexpression of human β-secretase (BACE-1) in HEK293 cells resulted in predominant Aβ cleavage at position Glu 11 rather than Asp 1, as well as increased production of Aβx–34, but not Aβx–40. Incubation of cells with a specific γ-secretase inhibitor suggests that cleavage of APP at Leu 34 could be mediated by γ-secretase itself or by a γ-secretase dependent process.