Gonadotropins decrease estrogen receptor-beta messenger ribonucleic acid stability in rat granulosa cells

Area of Science:

• Reproductive Endocrinology
• Molecular Biology
• Cellular Signaling

Background:

• The preovulatory LH surge plays a critical role in ovulation.
• Estrogen receptor-beta (ERbeta) mRNA levels in granulosa cells are known to be downregulated by the LH surge.
• The precise molecular mechanisms underlying this downregulation remain to be fully elucidated.

Purpose of the Study:

• To investigate whether the LH-induced decrease in ERbeta mRNA in rat granulosa cells occurs at the transcriptional or posttranscriptional level.
• To determine if mRNA degradation or altered transcription is the primary mechanism for LH-mediated ERbeta mRNA reduction.
• To explore the role of translation in the LH-induced destabilization of ERbeta mRNA.

Main Methods:

• Nuclear run-off assays to assess ERbeta gene transcription rates.
• Culture of granulosa cells with RNA synthesis inhibitor (DRB) to evaluate mRNA stability.
• Treatment with hCG, forskolin (FSK), and TPA to mimic LH actions.
• Semiquantitative RT-PCR and linear regression analysis to determine ERbeta mRNA half-life.
• Experiments using cycloheximide (protein synthesis inhibitor) to assess translation dependence.

Main Results:

• LH (hCG) had a marginal effect on ERbeta gene transcription.
• LH (hCG) significantly reduced ERbeta mRNA levels, primarily through mRNA destabilization.
• The half-life of ERbeta mRNA was significantly decreased by hCG, FSK, and TPA.
• The inhibitory effects of LH on ERbeta mRNA levels were abolished by cycloheximide, indicating a requirement for protein synthesis.

Conclusions:

• LH decreases ERbeta mRNA expression in granulosa cells mainly by enhancing mRNA degradation (posttranscriptional regulation).
• The LH-induced destabilization of ERbeta mRNA is a translation-dependent process.
• These findings provide crucial insights into the molecular mechanisms regulating ERbeta expression during the preovulatory period.