Association of the dioxin receptor with the M_r 90,000 heat shock protein: A structural kinship with the glucocorticoid receptor

The M_r ≈ 90,000 heat shock protein, hsp90, readily interacts with the glucocorticoid receptor to form the 9 S, non-DNA-binding receptor complex. This receptor is stabilized in cytosolic preparations by sodium molybdate. In analogy, sodium molybdate stabilizes a 9 S form of the dioxin receptor. Polyclonal antibodies raised against the purified glucocorticoid receptor-associated hsp90 interact with the molybdate-stabilized 9 S dioxin-receptor complex but not with the 4 S dioxin receptor monomer, as assessed by sedimentation shift analysis on sucrose gradients. Thus we conclude that both the dioxin and glucocorticoid receptor can form heteromeric complexes which share a common non-ligand-binding component. These results represent the first demonstration of a structural relationship between the dioxin and glucocorticoid receptors.