Direct Association with Thioredoxin Allows Redox Regulation of Glucocorticoid Receptor Function

Yuichi Makino,Noritada Yoshikawa,Kensaku Okamoto,Kiichi Hirota,Junji Yodoi,Isao Makino,Hirotoshi Tanaka

doi:10.1074/jbc.274.5.3182

Abstract

The glucocorticoid receptor (GR) is considered to belong to a class of transcription factors, the functions of which are exposed to redox regulation. We have recently demonstrated that thioredoxin (TRX), a cellular reducing catalyst, plays an important role in restoration of GR function in vivo under oxidative conditions. Although both the ligand binding domain and other domains of the GR have been suggested to be modulated by TRX, the molecular mechanism of the interaction is largely unknown. In the present study, we hypothesized that the DNA binding domain (DBD) of the GR, which is highly conserved among the nuclear receptors, is also responsible for communication with TRX in vivo. Mammalian two-hybrid assay and glutathione S-transferase pull-down assay revealed the direct association between TRX and the GR DBD. Moreover, analysis of subcellular localization of TRX and the chimeric protein harboring herpes simplex viral protein 16 transactivation domain and the GR DBD indicated that the interaction might take place in the nucleus under oxidative conditions. Together these observations indicate that TRX, via a direct association with the conserved DBD motif, may represent a key mediator operating in interplay between cellular redox signaling and nuclear receptor-mediated signal transduction.

Highlights

Gene expression is regulated via interactions between factors, including DNA-binding proteins, coactivators/corepressors, histones, and DNA, and it allows fine tuning of essential cellular processes; e.g. proliferation, growth, differentiation, energy metabolism, and stress responses [1]
A recent study has shown that cellular redox state is an important determinant of glucocorticoid receptor (GR) function in vivo and that TRX is implicated in redox regulation of GR function; GR-mediated gene expression is suppressed by oxidative treatment of cells, which overexpression of TRX counteracts [32]
DNA Binding Domain of the GR Is a Target of Redox Regulation—If TRX translocates into the nucleus under oxidative conditions, it is likely that TRX interacts with the GR in the nucleus to restore the transactivational function of the GR

Summary

Introduction

Gene expression is regulated via interactions between factors, including DNA-binding proteins, coactivators/corepressors, histones, and DNA, and it allows fine tuning of essential cellular processes; e.g. proliferation, growth, differentiation, energy metabolism, and stress responses [1]. A recent study has shown that cellular redox state is an important determinant of GR function in vivo and that TRX is implicated in redox regulation of GR function; GR-mediated gene expression is suppressed by oxidative treatment of cells, which overexpression of TRX counteracts [32].

Results

Conclusion