Dexamethasone 21-mesylate: an affinity label of glucocorticoid receptors from rat hepatoma tissue culture cells.
We recently described the biological properties of an alpha-keto mesylate derivative of cortisol, cortisol-Mes. Cortisol-Mes exhibited long-term antiglucocorticoid activity, but there was no firm evidence that this activity was irreversible or receptor-mediated. Here we report that dexamethasone mesylate (Dex-Mes), which is the alpha-keto mesylate derivative of the more active glucocorticoid dexamethasone, is a candidate for a steroid-specific affinity label of glucocorticoid receptors. Dex-Mes is relatively stable, like cortisol-Mes, but possesses greater whole-cell antiglucocorticoid activity. However, Dex-Mes also possesses partial agonist activity, which is expressed at somewhat higher concentrations of Dex-Mes than the antagonist activity. Dex-Mes is more efficient than cortisol-Mes in competing for dexamethasone binding to glucocorticoid receptors. Furthermore, Dex-Mes is effective at lower concentrations than cortisol-Mes in causing long-term apparently irreversible antiglucocorticoid effects in whole and broken cells. The cell-free effect of Dex-Mes is specifically prevented by coincubation with an excess of cortisol. These facts argue that the apparently irreversible effects of Dex-Mes are steroid mediated. [3H]Dex-Mes has been used to identify a glucocorticoid-specific, covalently labeled fraction on sodium dodecyl sulfate/polyacrylamide gels with a molecular weight of approximately 85,000. Thus Dex-Mes appears to have been established as an affinity label for glucocorticoid receptors.
D000345:Affinity Labels; D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000031:analogs & derivatives*; D004591:Electrophoresis, Polyacrylamide Gel; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D013329:Structure-Activity Relationship
D000345:Affinity Labels; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D003907:Dexamethasone; C031710:dexamethasone 21-methanesulfonate