Evidence that the endogenous heat-stable glucocorticoid receptor stabilizing factor is a metal component of the untransformed receptor complex.
Boiled cytosols prepared from a wide variety of sources contain a low Mr factor that inhibits glucocorticoid receptor transformation to the DNA-binding state (Leach, K.L., Grippo, J.F., Housley, P.R., Dahmer, M.K., Salive, M.E., and Pratt, W.B. (1982) J. Biol. Chem. 257, 381-388). In this work, we show that this endogenous factor, which is partially purified from rat liver, produces all of the effects of the group VI-A transition metal oxyanions molybdate and vanadate on the structure and function of glucocorticoid receptors in cytosol preparations. Like molybdate, the endogenous factor behaves as a strong anion with an apparent Mr of 340 on Bio-Gel P-2, and it binds to both hydroxylapatite and Chelex 100 resins. The receptor stabilizing activity of the factor is completely stable to heating at 320 degrees C for 1 h. The small size, profound heat stability, and absorption by a metal chelating resin strongly suggest that the factor is an endogenous metal anion. As reduction of the concentration of the factor in cytosol promotes generation of the DNA-binding form of the receptor, we suggest that this endogenous metal anion interacts with the receptor to stabilize the 9 S complex and maintain the receptor in its untransformed, non-DNA-binding state. We propose that molybdate and vanadate may exert their effects on the untransformed receptor by interacting with the binding site for the endogenous metal anion.
Meshinchi
S
S
Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109.
Grippo
J F
JF
Sanchez
E R
ER
Bresnick
E H
EH
Pratt
W B
WB
D000818:Animals; D002850:Chromatography, Gel; D004229:Dithiothreitol / Q000494:pharmacology; D008099:Liver / Q000032:analysis; D008670:Metals / Q000032:analysis*; D008970:Molecular Weight; D008982:Molybdenum / Q000494:pharmacology; D010742:Phospholipid Ethers / Q000032:analysis*; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000032:analysis*; D014638:Vanadates / Q000494:pharmacology
D008670:Metals; D010742:Phospholipid Ethers; D011965:Receptors, Glucocorticoid; C055044:glucocorticoid receptor complex modulator; C044659:molybdate; D014638:Vanadates; D008982:Molybdenum; D004229:Dithiothreitol