Fig. 2.

ALK5 mediates GDF-11-induced downregulation of StAR expression in hGL cells. A and 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 24 h. The mRNA (A) and protein (B) levels of StAR were determined by RT-qPCR and western blot, respectively. C and D, hGL cells were transfected with 100 nM control siRNA (si-Ctrl), ALK4 siRNA (si-ALK4) (C), or ALK5 siRNA (si-ALK5) (D) for 48 h, and then treated with 30 ng/mL GDF-11 (G11) for 24 h. The mRNA levels of ALK4, ALK5, and StAR were determined by RT-qPCR. E, hGL cells were transfected with 100 nM control siRNA (si-Ctrl) or ALK5 siRNA (si-ALK5) for 48 h, and then treated with 30 ng/mL GDF-11 (G11) for 24 h. The protein levels of ALK5 and StAR were determined by western blot. 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)