Relationship of the 90-kDa murine heat shock protein to the untransformed and transformed states of the L cell glucocorticoid receptor

Abstract

Incubation of molybdate-stabilized L cell cytosol with a monoclonal antibody directed against the 100-kDa glucocorticoid-binding protein causes the immune-specific adsorption to protein A-Sepharose of both the 100-kDa glucocorticoid receptor and the 90-kDa murine heat shock protein (hsp90) (Sanchez, E. R., Toft, D. O., Schlesinger, M. J., and Pratt, W. B. (1985) J. Biol. Chem. 260, 12398-12401). When the glucocorticoid receptor in cytosol is transformed to the DNA-binding state, hsp90 dissociates. In this paper, we show that temperature-mediated dissociation of hsp90 from the receptor is a hormone-dependent event in the same manner as temperature-mediated transformation to the DNA-binding state. In contrast to temperature-mediated transformation, ammonium sulfate causes both dissociation of hsp90 from the receptor and conversion of the receptor to the DNA-binding form in a manner that does not require the presence of steroid. The untransformed form of the glucocorticoid receptor and the strongly negatively charged hsp90 protein behave similarly on DEAE-cellulose chromatography, suggesting that the hsp90 component may contribute significantly to the net negative charge behavior of the non-DNA-binding form of the receptor complex.