Evidence that the 90-kDa phosphoprotein associated with the untransformed L-cell glucocorticoid receptor is a murine heat shock protein.
Two phosphoproteins are adsorbed to protein-A-Sepharose when cytosol from 32P-labeled L-cells is incubated with a monoclonal antibody against the glucocorticoid receptor: one is a 98-100-kDa phosphoprotein that contains the steroid-binding site and the other is a 90-kDa nonsteroid-binding phosphoprotein that is associated with the untransformed, molybdate-stabilized receptor (Housley, P. R., Sanchez, E. R., Westphal, H.M., Beato, M., and Pratt, W.B. (1985) J. Biol. Chem. 260, in press). In this paper we show that the 90-kDa receptor-associated phosphoprotein is an abundant cytosolic protein that reacts with a monoclonal antibody that recognizes the 90-kDa phosphoprotein that binds steroid receptors in the chicken oviduct. The 90-kDa protein immunoadsorbed from L-cell cytosol with this antibody reacts on Western blots with rabbit antiserum prepared against the 89-kDa chicken heat shock protein. Immunoadsorption of molybdate-stabilized cytosol by antibodies against the glucocorticoid receptor results in the presence of a 90-kDa protein that interacts on Western blots with the antiserum against the chicken heat shock protein. The association between the 90-kDa protein and the receptor is only seen by this technique when molybdate is present to stabilize the complex; and when steroid-bound receptors are incubated at 25 degrees C to transform them to the DNA-binding state, the 90-kDa protein dissociates. These observations are consistent with the proposal that the untransformed glucocorticoid receptor in L-cells exists in a complex with the murine 90-kDa heat shock protein.
D000818:Animals; D000911:Antibodies, Monoclonal; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007158:Immunologic Techniques; D007163:Immunosorbent Techniques; D007739:L Cells / Q000378:metabolism*; D051379:Mice; D008970:Molecular Weight; D008982:Molybdenum / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000378:metabolism
D000911:Antibodies, Monoclonal; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D011965:Receptors, Glucocorticoid; D008982:Molybdenum; D004247:DNA; C024687:sodium molybdate(VI); D014222:Triamcinolone Acetonide