# Ligand-independent signaling of estrogen receptor beta and the aging brain

> **NIH NIH R01** · LOYOLA UNIVERSITY CHICAGO · 2021 · $442,961

## Abstract

PROJECT SUMMARY. We propose that there is a biological switch in estrogen receptor action that occurs
coincident with age and length of time after ovarian hormone depletion (i.e. menopause). Accumulating
evidence suggests that ERb shifts from a predominantly ligand-activated transcription factor (major role during
reproductive years) to a ligand-independent transcription factor post-menopause. Elucidating the molecular
basis for this shift in signaling paradigms is critical for understanding clinical observations, which demonstrate
a defined narrow window of time for therapeutic efficacy of hormone therapy in postmenopausal women.
 This application is a competitive renewal of R01 AG033605. Our previous aims for this project centered on
factors that we predicted would differentially dictate a dominant ligand-dependent signaling pattern for ERb, as
opposed to a ligand-independent signaling pattern. Through that work, we identified 3 key molecular factors
that facilitated ligand-independent function of ERb in the aged brain: receptor phosphorylation, alternative RNA
splicing, and coregulatory protein interactions. These mechanisms represented both direct changes to the
receptor itself and indirect changes in protein:protein interactions. The experiments proposed in this
renewal will be focused on the direct changes to the ERb protein itself, namely phosphorylation and
alternative splicing. Aim 1 will focus on posttranslational phosphorylation of the receptor. Phosphorylation of
ERb is a strong facilitator of ligand-independent activity, yet the extent of phosphorylated ERb present in the
aged female brain, and the in vivo functional consequences of such a modification, represents a major gap in
our current knowledge. We propose a comprehensive proteomics approach to a) quantify phosphor-ERb in the
aged female brain, b) determine how site-specific phosphorylation alters ERb protein:protein interactions, and
c) identify specific phospho-ERb target genes. Aim 2 will focus on alternative RNA splicing of the nascent ERb
transcript. Our data and others have demonstrated the functional significance of ERb splice variants and we
have shown that these alternative variants increase during aging. However, we lack a fundamental
understanding of the molecular mechanisms regulating ERb splicing in the brain, or in any tissue type. We
have now identified several putative splicing factors that regulate alternative splicing of ERb in the aged brain.
This aim will test the direct effects of these splicing factors on ERb alternative splicing and also determine if E2
regulates global splicing events by modulating the expression of these splicing factors. Our preliminary data
also showed that transcriptional kinetics play an important role in ERb splicing, with slower transcription
favoring exon inclusion resulting in increased ERb2. This aim will further explore this relationship to test how
transcriptional kinetics in the brain change in our aging female rat menopause...

## Key facts

- **NIH application ID:** 10168391
- **Project number:** 5R01AG033605-10
- **Recipient organization:** LOYOLA UNIVERSITY CHICAGO
- **Principal Investigator:** Toni R. Pak
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $442,961
- **Award type:** 5
- **Project period:** 2009-08-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10168391

## Citation

> US National Institutes of Health, RePORTER application 10168391, Ligand-independent signaling of estrogen receptor beta and the aging brain (5R01AG033605-10). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10168391. Licensed CC0.

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