Glucocorticoid Receptor-β and Receptor-γ Exert Dominant Negative Effect on Gene Repression But Not on Gene Induction

Abstract

Glucocorticoid has diverse biological effects through induction or repression of its target genes via glucocorticoid receptor (GR). In addition to the wild-type GR (GR-alpha), a variety of GR variants has been reported, and these are thought to modify glucocorticoid action. Among others, GR-beta is reported be responsible for the glucocorticoid resistance frequently observed in steroid-resistant nephrotic syndrome, rheumatoid arthritis, and hematologic tumors, although the precise molecular mechanism remains unclear. In this study, we examined the function of GR-beta and some GR variants (GR-gamma and GR-Delta313-338) using GR-deficient BE(2)C and T84 cells in vitro. We found that GR-beta, when expressed alone, completely lost the capacity of both trans-activation and trans-repression on GR target genes. Interestingly, however, GR-beta showed a dominant-negative effect on GR-alpha only for its trans-repressive effects on cAMP-mediated and cAMP response element-dependent genes. Furthermore, both GR-beta and GR-gamma had dominant-negative effects on GR-alpha selectively for its trans-repressive effects on nuclear factor-kappaB-mediated and inflammation-related genes. These results suggest that 1) the GR-beta variant by itself has no receptor function, but 2) GR-beta and GR-gamma have properties to exert dominant-negative effects on the GR-alpha-mediated trans-repression, which may be responsible for the steroid resistance frequently observed in chronic inflammatory diseases under glucocorticoid therapy.