Figure 10.

Effects of ORP1 expression on liver X receptor α-mediated transactivation of a luciferase reporter gene. (A) ORP1L potentiates LXR-RXR transactivation in a dose-dependent manner. COS-1 cells were transfected with a reporter plasmid containing a TK promotor with three copies of a consensus LXRE, LXRα, and/or RXR expression plasmids, and increasing quantities of pcDNAHisMax/ORP1L and incubated in the absence (white bars) or presence (black bars) of 10 μM 22(R)-hydroxycholesterol. (B) Another member of the ORP protein family, ORP6, has no effect on transactivation by LXRα-RXR. COS-1 cells were transfected with LXRα-RXR and/or ORP6 expression plasmids, and incubated in the absence or presence of 10 μM 22(R)-hydroxycholesterol. (C) ORP1L potentiation of LXRα-RXR transactivation is ligand dependent but not specific for the oxysterol ligand or the cell-type used. HEK 293 cells were transfected with LXRα-RXR and/or ORP1L expression plasmids and incubated in the absence or presence of the nonsterol synthetic LXR agonist T0901317 (0.1 μM). (D) ORP1L effect is not mediated through RXR and is independent of the specific interaction of LXRα/RXR with LXRE. HEK 293 cells were transfected with expression plasmids encoding a Gal4 DNA binding domain-LXRα ligand binding domain fusion (Gal4-LXRα) and/or ORP1L. The cells were incubated in the absence or presence of T0901317. (E) ORP1L does not influence transactivation by PPARα-RXR. COS-1 cells were transfected with a reporter plasmid containing six copies of a PPAR response element and the expression plasmids for PPARα, RXR, and/or ORP1L and incubated in the absence or presence of the PPARα agonist WY 14643 (50 μM). (F) ORP1S is not capable of enhancing reporter transactivation by LXRα. HEK 293 cells were transfected with LXRα, RXR, and/or ORP1L or ORP1S expression constructs and incubated in the absence or presence of T0901317.