Heat Shock Protein is Tightly Associated with the Recombinant Human Glucocorticoid Receptor:glucocorticoid Response Element Complex

The association of heat shock proteins (hsp) with steroid hormone receptors may have functional significance for steroid receptor action. The association of hsp90 with steroid receptors is thought to maintain the receptors in the nonactivated state until their interaction with the respective ligand. The association of hsp70 with progesterone receptor has been well documented. However, there is evidence both for and against the association of hsp70 with the glucocorticoid receptor (GR). We have examined the interaction between hsp70 and human (h) GR over-expressed in the Baculovirus system. Immunoprecipitation and sucrose gradient centrifugation studies demonstrated the association of hsp70 with both the nonactivated and in vitro activated hGR. We were unable to dissociate hGR and hsp70 by incubation of crude cytosol with 3 mM ATP and 0.5 M NaCl. In vivo activation of hGR did not result in dissociation of hsp70 from hGR. Hsp70 coeluted with hGR from a glucocorticoid response element (GRE)-Sepharose column, suggesting that hsp70 is part of the GRE-hGR complex. Both an anti-hGR antibody and an anti-hsp70 antibody were capable of further retarding the migration of a [32P]GRE-hGR complex in polyacrylamide gels. The in vitro activated hGR has been shown to be highly active in an in vitro transcription system. We speculate that hsp70 may influence the DNA-binding and/or transcriptional activities of hGR.