Figure 4.

Dragon increases BMP but not TGF-β signaling in kidney tubule cells. (A) Dragon increases BMP signaling. mIMCD3 cells were transfected with BRE-Luc construct in the absence (bars 1 and 2), or presence (bar 3) of Dragon cDNA. Cells were then starved and incubated for 16 hours in the absence (bars 1 and 3) or presence of 40 ng/ml BMP4 (bar 2), and luciferase activity was measured the next day from cell extracts. ***P < 0.001 versus the control. (B) Dragon does not affect TGF-β signaling. mIMCD3 cells were transfected with the (CAGA)₁₂MLP-Luc construct in the absence (bars 1 and 2) or presence (bar 3) of Dragon cDNA. Cells were incubated for 16 hours in the absence (bars 1 and 3) or presence of 2 ng/ml TGF-β1 (bar 2), and luciferase activity was measured the next day. ***P < 0.001 versus the control. (C) Dragon increases BMP signaling in a dose dependent manner. mIMCD3 cells were transfected with BRE-Luc construct with increasing amounts of Dragon cDNA (0, 2, 20, 200, and 500 ng). Relative luciferase activity was measured from cell extracts. *P < 0.05 and ***P < 0.001 versus the control. (D) BMP4 and Dragon signals are additive. mIMCD3 cells were transfected with the BRE-Luc construct in the absence or presence of Dragon cDNA. Cells were then incubated without (open bars) or with BMP4 (filled bars) and relative luciferase activity was measured from cells extracts. ***P < 0.001, bar 3 versus bar 1; ###P < 0.05, bar 4 versus bar 2.