Review Volume 10, Issue 3 pp 305—321

The role of FSH and TGF-β superfamily in follicle atresia

Figure 2. Crosstalk between TGF-β signaling and PKA/PI3K/Akt axis. TGF-β signals through tetramer receptors as dimers. TGF-β receptors phosphorylate R-Smad and two phosphorylated R-Smad forms a complex with one Co-Smad. This complex can enter the nucleus and bind to the Smad-binding element in the FSHR promotor and promote the expression of FSH receptors. FOXL2 can strengthen this effect by binding to a forkhead-binding element near the Smad-binding element. Akt induced by FSH through PKA can phosphorylate AS160 mainly at Thr642, which is a guanosine triphosphatase (GTPase)-activating protein. Then activated GTPase proteins facilitate the fusion of TGF-βR loaded vesicles to the membrane.