Proteasome-Mediated Regulation of GATA2 Expression and Androgen Receptor Transcription in Benign Prostate Epithelial Cells.

Waqas Azeem,Anne Margrete Øyan,Yaping Hua,Jan Roger Olsen,Margrete Reime Hellem,Kristo Marvyin,Xisong Ke,Karl-Henning Kalland

doi:10.3390/biomedicines10020473

Waqas Azeem, Anne Margrete Øyan + Show 6 more

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https://doi.org/10.3390/biomedicines10020473

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Abstract

GATA2 has been shown to be an important transcription factor together with androgen receptor (AR) in prostate cancer cells. Less is known about GATA2 in benign prostate epithelial cells. We have investigated if GATA2 exogenous expression in prostate epithelial basal-like cells could induce AR transcription or luminal differentiation. Prostate epithelial basal-like (transit amplifying) cells were transduced with lentiviral vector expressing GATA2. Luminal differentiation markers were assessed by RT-qPCR, Western blot and global gene expression microarrays. We utilized our previously established AR and androgen-dependent fluorescence reporter assay to investigate AR activity at the single-cell level. Exogenous GATA2 protein was rapidly and proteasome-dependently degraded. GATA2 protein expression was rescued by the proteasome inhibitor MG132 and partly by mutating the target site of the E3 ligase FBXW7. Moreover, MG132-mediated proteasome inhibition induced AR mRNA and additional luminal marker gene transcription in the prostate transit amplifying cells. Different types of intrinsic mechanisms restricted GATA2 expression in the transit amplifying cells. The appearance of AR mRNA and additional luminal marker gene expression changes following proteasome inhibition suggests control of essential cofactor(s) of AR mRNA expression and luminal differentiation at this proteolytic level.

Highlights

We have previously found that the transcription of the androgen receptor (AR) mRNA is effectively silenced in EP156T cells, and luminal differentiation markers and AR target genes such as KLK3, KLK2, FKBP5 and NKX3-1 are not induced by androgen addition [8]
We found that threonine 176 of GATA binding protein 2 (GATA2) was important for proteasome-mediated degradation
Exogenous GATA2 could be rescued by the proteasome-inhibitor MG132, it was difficult to investigate further the physiological role played by GATA2 in luminal cell differentiation

Summary

Introduction

MG132-mediated proteasome inhibition induced AR mRNA and additional luminal marker gene transcription in the prostate transit amplifying cells. We have previously found that the transcription of the androgen receptor (AR) mRNA is effectively silenced in EP156T cells, and luminal differentiation markers and AR target genes such as KLK3, KLK2, FKBP5 and NKX3-1 are not induced by androgen addition [8]. These AR target genes are, readily induced by androgen following exogenous expression of AR, but with endogenous AR remaining silent [8].

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