RAF1 mediates the FSH signaling pathway as a downstream molecule to stimulate estradiol synthesis and secretion in mouse ovarian granulosa cells

BACKGROUND: The v-raf-leukemia viral oncogene 1 (RAF1) plays an essential physiological role in reproduction and development through the mediation of steroid hormone synthesis. Follicle-stimulating hormone (FSH) signaling pathway was not involved in the majority of RAF1 studies, whether RAF1 takes part in the signaling events of gonadotropic hormones such as FSH in ovarian tissue is unknown. METHODS: The process is blocked by treating granulosa cells (GCs) with the RAF1 inhibitor, RAF709. Inhibition of RAF1 activity by RAF709 decreased extracellular regulated protein kinases (ERK) phosphorylation and suppressed the expression of the cytochrome P450 subfamily 19 member 1 (CYP19A1), which is a major rate-limiting enzyme that participates in the last step of E2 biosynthesis. RESULTS: We found that RAF1, acting as a downstream molecule, mediates FSH signalling to stimulate estradiol (E2) synthesis and secretion in mouse ovarian GCs. Gene expression of RAF1 was induced by FSH and the secretion of E2 increased into the bloodstream of mice and into the supernatant of primary GCs. Our in vitro and in vivo studies clearly illustrate RAF1 plays an important medium adjusting role in the FSH signaling pathway, and RAF1 acting as a downstream molecule to trigger ERK phosphorylation to stimulate GC E2 synthesis and secretion. CONCLUSIONS: RAF1 plays a pivotal mediating role in the FSH signaling pathway by inducing the phosphorylation of ERK and promoting E2 synthesis.