Fig. 3.

Effect of PLD inhibition on FIC1-mediated activation of the human BSEP promoter. UPS cells were untransfected (control) or transfected (FIC1) with a wild-type FIC1 construct. Cells were treated with siPLD1, siPLD2, a scrambled anti-sense control (siScr), or 1 nM FIPI. A: Human BSEP promoter activity. The human BSEP promoter was used as a readout of FXR activity. Activity in untreated UPS cells was set at 100% and all results were normalized to renilla luciferase from a pRL-TK construct as a control for transfection efficiency. The scale of the y axis is logarithmic. Error bars represent the SD for nine measurements. Basal BSEP promoter activity was significantly lower in the UPS cells treated with siPLD2 or FIPI but not siPLD1 or siScr. In each of the treatment groups, FIC1 overexpression led to a statistically significant increase in BSEP promoter activity. B: FIC1 mediated activation of human BSEP promoter activity. The degree of activation (i.e., FIC1 treated/untreated promoter activity) is significantly lower in the siPLD2- and FIPI-treated cells compared with the rest of the experimental groups that are equivalent.