Cytosolic side of TMD1 forms a fenofibrate binding pocket. (A) Sensitivity of PS1-Th1 for GSMs. Effect of DAPT (10 μM), GSM-1 (1 μM), NS-1017 (1 μM) and fenofibrate (50 μM) on secreted Aβ from wild-type PS1 containing γ-secretase using DKO cells stably expressing APPNL (n = 3, mean ± SD, *p < 0.01, **p < 0.05 at Student’s t test). (B) Thrombin digestion experiments were performed after PAL by GSM-1-BpB (1 μM), GSM-1-amide-BpB (1 μM) and Fen-B (10 μM). Note that cleaved Th1-fragment (arrowhead) was precipitated and detected by anti-PS1 NTF antibody. (C) Labeling competition analysis of Fen-B (10 μM) in the presence of fenofibrate (100 μM) using PS1-Th1 microsomes. Upper and lower panels show short and long exposures, respectively. (D) Labeling competition analyses were performed with fenofibrate (100 μM), L-685,458 (10 μM), GSM-1 (100 μM) and NS-1017 (100 μM) for the labeling of PS1 NTF by Fen-B (10 μM). (E) Labeling competition experiment with L-685,458 (10 μM) and fenofibrate (100 μM) for the labeling of PS1 NTF by L-852,646 (100 nM). (F) Labeling competition analysis by GSM-1-BpB (1 μM) in the presence of GSM-1 (100 μM) or fenofibrate (100 μM) using CHO cell microsomes. (G) SCAM analyses of microsomes from DKO cells expressing single-Cys mt PS1 containing one Cys at 82 or 85 positions in the presence or absence of indicated compounds. Note that the labeling of V82C was decreased and of L85C was increased by preincubation with fenofibrate. (H) Alignment of amino acid residues of PS1 TMD1 (78th to 100th residues) and 37th to 58th residues of SPP, which includes predicted TMD1 (32nd to 54th residues ). Asterisks and colons indicate conserved and similar amino acids, respectively.