Progesterone Receptor A Stability Is Mediated by Glycogen Synthase Kinase-3β in the Brca1-deficient Mammary Gland

Shaohui Wang,Ying Li,Pang-Hung Hsu,Sou-Ying Lee,Yoon Kim,Eva Y.-H.P Lee

doi:10.1074/jbc.m113.476556

Abstract

Germ line mutations of the BRCA1 gene increase the risk of breast and ovarian cancer, but the basis of this tissue-specific tumor predisposition is not fully understood. Previously, we reported that the progesterone receptors are stabilized in Brca1-deficient mammary epithelial cells, and treating with anti-progesterone delays mammary tumorigenesis in Brca1/p53 conditional knock-out mice, suggesting that the progesterone has a critical role in breast carcinogenesis. To further explore how the stability of progesterone receptor is modulated, here, we have found that glycogen synthase kinase (GSK)-3β phosphorylation of progesterone receptor-A (PR-A) facilitates its ubiquitination. GSK-3β-mediated phosphorylation of serine 390 in PR-A regulates its subsequent ubiquitination and protein stability. Expression of PR-A(S390A) mutant in the human breast epithelial cells, MCF-10A, results in enhanced proliferation and formation of aberrant acini structure in the three-dimensional culture. Consistently, reduction of phosphorylation of serine 390 of PR-A and GSK-3β activity is observed in the Brca1-deficient mammary gland. Taken together, these results provide important aspects of tissue specificity of BRCA1-mediated suppression of breast carcinogenesis.

Highlights

Stabilization of progesterone receptors contributes to mammary tumorigenesis in Brca1-deficient mice
glycogen synthase kinase (GSK)-3␤ Kinase Enhances progesterone receptor-A (PR-A) Ubiquitination and Degradation—Upon ligand binding, progesterone receptors become phosphorylated at multiple sites; the receptors are subsequently polyubiquitinated and degraded by the proteasome
To test whether GSK-3␤ has any effect on Progesterone receptors (PRs)-A polyubiquitination, we performed in vitro ubiquitination assay in the presence of E1, E2, and BRCA1-BARD1 complexes as previously described [11]

Summary

Introduction

Stabilization of progesterone receptors contributes to mammary tumorigenesis in Brca1-deficient mice. Results: Deficiency in phosphorylation on serine 390 of progesterone receptor A by GSK-3␤ enhances the receptor stability. Conclusion: Stabilization of progesterone receptor A is mediated by GSK-3␤ kinase in the Brca1-deficient mammary gland. We reported that the progesterone receptors are stabilized in Brca1-deficient mammary epithelial cells, and treating with anti-progesterone delays mammary tumorigenesis in Brca1/ p53 conditional knock-out mice, suggesting that the progesterone has a critical role in breast carcinogenesis. Reduction of phosphorylation of serine 390 of PR-A and GSK-3␤ activity is observed in the Brca1-deficient mammary gland. Taken together, these results provide important aspects of tissue specificity of BRCA1-mediated suppression of breast carcinogenesis

Methods

Results

Conclusion