Figure 6
VDR concentration-response curves. Ligand activation of VDRs from different species, chimeric human-frog VDRs, and mouse VDR site-directed mutants. A) The plot shows activation of human, chicken, Xenopus laevis, and Tetraodon VDRs by 1,25-dihydroxyvitamin D3. Also shown are activation data for a chimeric receptor that is mostly human VDR (hVDR) with the H1-H3 insert replaced by the corresponding sequence from Xenopus laevis VDR (xlVDR) and the converse chimeric receptor that is mostly xlVDR with the H1-H3 insert replaced by the corresponding sequence from hVDR. B) The plot shows activation of mouse VDR (mVDR) and six site-directed mutants of mVDR (R269A, R269E, H392A, H392Y, F417A, and F417D) by 1,25-dihydroxyvitamin D3. C) Lithocholic acid (LCA) activates human, chicken, and Tetraodon VDRs, as well as the chimeric receptor hVDR with xlVDR h1-H3 insert, but does not activate xlVDR and the chimeric receptor xlVDR with the hVDR H1-H3 insert. D) Lithocholic acid strongly activates mVDR, weakly activates the site-directed mutants F417A and F417D, and does not activate R269A, R269E, H392A, and H392Y. The ordinate indicates fold induction compared to vehicle control in luciferase-based assay. Note that the scale of the ordinate is different in A) through D).