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

Abstract

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