LMDP cleavage by γ-secretase.

(a) γ-secretase activity in cultured cells. The fluorescence peptide probe was incubated with membrane fractions from HUEhT-2, HeLa, MCF-7 and A549 cells. (b) Competitive inhibition of LMDP. The peptide probe and LMDP were incubated at the indicated concentrations in the membrane fraction of A549 cells at 37°C overnight. Values and bars represent the means and SD, respectively. (c) Representative chromatograms of LMDP with or without the membrane fraction as determined by HPLC analysis from three independent experiments. *, P<0.05; **, P<0.01; ***, P<0.001 versus HUEhT-2 (a), 0 µM LMDP (b), n = 3.