RAF1 as Downstream Molecule Mediates the FSH Signaling Pathway to Stimulate E2 Synthesis and Secretion in Mouse Ovarian Granulosa Cells

Abstract Background: V-raf-leukemia viral oncogene 1 (RAF1) kinase is the key factor in extracellular signal regulated pathway, which transmits signals to the downstream extracellular regulated protein kinases (ERK). Regulatory function of RAF1 has been proved to mediate steroid hormone synthesis, which played an essential physiological function in reproduction and development. Whether RAF1 takes part in the signaling events of gonadotropic hormones follicle-stimulating hormone (FSH) in ovarian is unknown.Results: We found that RAF1 as downstream molecule mediates the FSH signaling pathway to stimulate estradiol (E2) synthesis and secretion in mouse ovarian granulosa cells (GCs). The expression of RAF1 is induced by FSH and the production of E2 is increased in the serum and primary ovarian GCs supernatant, the process of which is blocked by treating with RAF1 inhibitor (N-(2-Methyl-5'-morpholino-6'-((tetrahydro-2H-pyran-4-yl)oxy)-[3,3'-bipyridin]-5-yl)-3(trifluoromethyl) benzamide, RAF709). Inhibition of RAF1 activity by RAF709 decreased ERK phosphorylation, and suppressed the expression of cytochrome P450 family 19 subfamily a member 1 (CYP19A1) which is a major rate-limiting enzyme to participate in the last step of E2 biosynthesis. Conclusion: Our results suggest that RAF1 play a pivotal mediating roles toward E2 production in FSH signaling pathway by inducing the phosphorylation of ERK and promoting the process of estradiol synthesis. RAF1 may be a potential and effective factor to regulate the function of the female mouse reproductive system.