Fig. 3

GDF-11 activates SMAD2/3 signaling pathways in hGL cells. A, hGL cells were treated with 30 ng/mL GDF-11 (G11) for 30 and 60 min. The levels of phosphorylated and total forms of SMAD2/3 were determined by western blot. B, hGL cells were pretreated with vehicle control (DMSO) or 10 µM SB431542 for 1 h, and then treated with 30 ng/mL GDF-11 (G11) for 60 min. The levels of phosphorylated and total forms of SMAD2/3 were determined by western blot. C and D, hGL cells were transfected with 100 nM control siRNA (si-Ctrl) or SMAD4 siRNA (si-SMAD4) for 48 h, and then treated with 30 ng/mL GDF-11 (G11) for 24 h. The mRNA (C) and protein (D) levels of SMAD4 and StAR were determined by RT-qPCR and western blot, respectively. The results are expressed as the mean ± SEM of at least three independent experiments. The values without a common letter are significantly different (p < 0.05)