8701 Rsk2 Regulates Estrogen Homeostasis in Metabolism and Fertility

Abstract Disclosure: E.B. Wright: None. Rsk2 is a protein kinase activated downstream of the Ras/Raf/MEK/ERK cascade and has numerous substrates in metabolism, transcription, and translation. However, the role for Rsk2 in regulation of metabolic substrates has only been studied in cancer cell lines. In breast cancer, active nuclear Rsk2 associates with ERα and promotes transformation by activating a transcriptional program critical to the ER+ lineage in the mammary gland[1]. Cancer co-opts programs important in development and homeostasis, and in investigating this possibility we identified that Rsk2 is an important mediator of reproduction2. The link between metabolism and fertility is poorly understood, and Rsk2 may act as a sensor linking metabolism to fertility. To investigate this link, we looked to the liver as a central regulator of metabolism. Hepatic ERα is a transcriptional regulator of metabolic programs, but it is unknown whether Rsk2 regulates hepatic ERα activity. To investigate the role of Rsk2 in regulation of hepatic ERα, livers and mammary epithelial cells were collected from WT or Rsk2-KO female mice in estrus or diestrus, age 14.0 ± 1.8 wk. RNAseq analysis was performed on bulk liver as hepatocytes are ERα+ and comprise 60-70% of the liver cell population. RNAseq on mammary gland was performed on purified ERα+ mammary epithelial cells (MEC), as these cells comprise only 10% of the mammary gland. To evaluate liver response to estrogen, cumulative Z-scores of gene expression were compared to an estrogen signature obtained from the livers of mice treated with oral estradiol3. For the mammary gland, cumulative Z-scores were compared against an estrogen signature obtained from MCF7 treated with estradiol4. Livers from WT mice in estrus had a significantly stronger estrogen signature compared to Rsk2-KO mice in estrus (p = 0.0152, n ≥ 6). In contrast to the liver, Rsk2-KO MEC in estrus had a stronger estrogen response compared to WT (p = 0.028, n =3). Therefore, we have identified differential regulation of estrogen response by Rsk2 in the mammary gland and liver. Rsk2 is a negative regulator of estrogen response in the mammary gland, whereas Rsk2 promotes hepatic estrogen response. These data support our hypothesis that Rsk2 is a physiological regulator of metabolism and fertility by regulating estrogen response. References: (1) Ludwik, K. A., et al. Cancer Res. 2018 (78): 2014-2025. (2) Ludwik, K. A. et al. Cell Reports. 2020 (32): 107931. (3) Palierne, G. et al. Mol Endo. 2016 (30): 709-732. (4) Dutertre, M. et al. Cancer Res. 2010 (70): 3760-3770. Presentation: 6/3/2024