Abstract
A surge of luteinizing hormone (LH) from the pituitary gland induces the expression of the epidermal growth factor (EGF)-like factors, which triggers oocyte maturation, cumulus expansion, and ovulation. How LH induces EGF-like factor expression is unclear. In the present study, a rapid increase of phosphorylated cAMP response element binding protein (CREB) was observed after the activation of LH receptor by human chorionic gonadotropin. Large antral follicles from equine chorionic gonadotropin-primed mice were cultured in medium with LH to stimulate the expression of EGF-like factors. CREB phosphorylation was increased in granulosa cells; conversely KG-501, a CREB functional inhibitor, significantly reduced LH-induced gene expression of EGF-like factors, oocyte meiotic resumption, and cumulus cell expansion. Reduction of CREB expression by Creb siRNA also repressed LH-induced expression of EGF-like factors in cultured granulosa cells. Inactivation of mitogen-activated protein kinase (MAPK3/1) by U0126 inhibited LH-induced CREB phosphorylation and EGF-like factors gene expression, whereas the activation of LH receptor increased Akt/protein kinase B phosphorylation, which is involved in LH-induced CREB phosphorylation and the expression of EGF-like factors. Thus, LH induces MAPK3/1 and Akt activation, both of which are required for the CREB-promoted expression of EGF-like factors in granulosa cells. Mol. Reprod. Dev. 83: 1116-1127, 2016. © 2016 Wiley Periodicals, Inc.