G protein interacts with the glucocorticoid receptor and suppresses its transcriptional activity in the nucleus

Authors:
Kino T, Tiulpakov A, Ichijo T, Chheng L, Kozasa T and Chrousos GP
In:
Source: J Cell Biol
Publication Date: (2005)
Issue: 169(6): 885-896
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
HTC
Species: rat
Tissue Origin: liver
GH3
Species: rat
Tissue Origin:
Platform:
Nucleofector® I/II/2b
Abstract
Extracellular stimuli that activate cell surface receptors modulate glucocorticoid actions via as yet unclear mechanisms. Here, we report that the guanine nucleotide-binding protein (G protein)-coupled receptor-activated WD-repeat Gbeta interacts with the glucocorticoid receptor (GR), comigrates with it into the nucleus and suppresses GR-induced transactivation of the glucocorticoid-responsive genes. Association of Ggamma with Gbeta is necessary for this action of Gbeta. Both endogenous and enhanced green fluorescent protein (EGFP)-fused Gbeta2 and Ggamma2 proteins were detected in the nucleus at baseline, whereas a fraction of EGFP-Gbeta2 and DsRed2-GR comigrated to the nucleus or the plasma membrane, depending on the exposure of cells to dexamethasone or somatostatin, respectively. Gbeta2 was associated with GR/glucocorticoid response elements (GREs) in vivo and suppressed activation function-2-directed transcriptional activity of the GR. We conclude that the Gbetagamma complex interacts with the GR and suppresses its transcriptional activity by associating with the transcriptional complex formed on GR-responsive promoters