Nirogacestat (PF-03084014)

A DNA fragment encoding amino acids 596 - 695 of the 695-aa isoform of APP (APP695) and the Flag sequence (DYKDDDDK) at the C terminus is generated by PCR amplification with suitably designed oligonucleotides and the APP695 cDNA. The Met that serves as the translation start site is residue 596 of APP695 (the P1 residue with respect to theβ-secretase cleavage site). This DNA fragment is inserted into the prokaryotic expression vector pET2-21b. The recombinant protein, C100Flag, is overproduced in Escherichia coli [strain BL21(DE3)] and purified by Mono-Q column chromatography. C100Flag (1.7 μM) is incubated with cell membranes (0.5 mg/mL) in the presence of CHAPSO, CHAPS (3-[(3-cholamidopropyl)dim-ethylammonio]-1-propanesulfonate), or Triton X-100 (0, 0.125, 0.25, 0.5, or 1%) in buffer B (50 mM Pipes, pH 7.0y 5mM MgCl₂/5 mM CaCl₂/150 mM KCl) at 37°C. The reactions are stopped by adding RIPA (150 mM NaCl/1.0% NP-40/0.5% sodium deoxycholatey 0.1% SDS/50 mM Tris HCl, pH 8.0) and boiling for 5 min. The samples ae centrifuged and the supernatant solutions are assayed for the Aβ peptides by ECL. The Aβ40- and Aβ42-related products from γ-secretase-mediated processing of C100Flag possess a Met at the N terminus and are thus defined as M-Aβ40 and M-Aβ42, respectively. Likewise, supernatant solution (0.125 mg/mL) from CHAPSO-extracted HeLa cell membranes (solubilized γ-secretase) is incubated with C100Flag (1.7 μM) in buffer B containing 0.25% CHAPSO and subsequently assayed for M-Aβ40 and M-Aβ42 by using ECL.