High levels of non-activated receptors in glucocorticoid-sensitive S49wt mouse lymphoma cells incubated with dexamethasone.
Upon agonist binding the heteromeric glucocorticoid receptor complex undergoes a conformational change (receptor activation). This event involves the dissociation of a dimer of 90 kDa heat shock proteins. Whereas receptor activation in cytosolic assays is both rapid and irreversible, less is known about the receptor activation and translocation in intact cells during challenge with an agonist. In this paper we report on the receptor status of glucocorticoid-sensitive murine S49 lymphoma cells during dexamethasone exposure. By three different assays, ligand (re)binding, nuclear translocation and hsp90 co-immunoprecipitation, it was found that the majority of the glucocorticoid receptor protein was in a non-activated conformation. Furthermore, prolonged exposure to dexamethasone did not result in increased levels of activated receptors. By assessing receptor activation in situ we found that physiological temperature was less effective in dissociating hsp90 compared to room temperature. These findings indicate that the physiological temperature negatively controls receptor activation, probably due to a thermolabile interaction between the hormone and its cognate receptor.
van den Berg
J D
JD
The Netherlands Cancer Institute/Antoni van Leeuwenhoekhuis, Division of Experimental Therapy, Amsterdam.
Smets
L A
LA
Hutchison
K A
KA
van Rooij
H
H
van den Elshout
M M
MM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry; D003907:Dexamethasone / Q000494:pharmacology*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D008024:Ligands; D008223:Lymphoma / Q000378:metabolism*; D051379:Mice; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013696:Temperature; D014407:Tumor Cells, Cultured
D018841:HSP90 Heat-Shock Proteins; D008024:Ligands; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone