Estrogen Receptor β Is Required for Optimal cAMP Production in Mouse Granulosa Cells

Abstract

AbstractGranulosa cells of preovulatory follicles differentiate in response to FSH, and this differentiation is augmented by estradiol. We have previously shown that FSH-mediated granulosa cell differentiation requires functional estrogen receptor-β (ERβ) by demonstrating that the granulosa cells of ERβ−/− FSH-treated mice are unable to maximally induce expression of the LH receptor (an indicator of granulosa cell differentiation) compared with ERβ+/+ controls. As a result, FSH-primed ERβ−/− granulosa cells exhibit a reduced response to a subsequent ovulatory dose of LH. In this study, we further characterized the attenuated response of ERβ−/− granulosa cells to stimulation by LH and FSH using isolated mouse granulosa cells and primary granulosa cell cultures. We observed a 50% reduction in cAMP levels in cultured ERβ−/− granulosa cells exposed to LH compared with ERβ+/+ controls. We also observed an attenuated genomic response in granulosa cells isolated from FSH-primed ERβ−/− mice compared with ERβ+/+ controls. Our data indicate that this attenuated response may result from inadequate levels of cAMP, because cAMP levels in cultured ERβ−/− granulosa cells exposed to forskolin were approximately 50% lower than in ERβ+/+ granulosa cells. Phosphorylation of cAMP regulatory element binding protein, an indicator of protein kinase A activity, was also reduced in FSH-treated ERβ−/− granulosa cells compared with ERβ+/+ controls. These are the first data to indicate that ERβ plays a role in the induction of the cAMP pathway in mouse granulosa cells and that disruption of proper ERβ signaling associated with this pathway may cause negative effects on ovulation and fertility.