van den Berg J D, Smets L A, Hutchison K A, van Rooij H, van den Elshout M M
The Netherlands Cancer Institute/Antoni van Leeuwenhoekhuis, Division of Experimental Therapy, Amsterdam.
J Steroid Biochem Mol Biol. 1994 Oct;51(1-2):33-40. doi: 10.1016/0960-0760(94)90112-0.
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.
激动剂结合后，异源糖皮质激素受体复合物会发生构象变化（受体激活）。这一过程涉及90 kDa热休克蛋白二聚体的解离。虽然在胞质分析中受体激活既快速又不可逆，但对于完整细胞在激动剂刺激下的受体激活和转位了解较少。在本文中，我们报告了地塞米松暴露期间糖皮质激素敏感的小鼠S49淋巴瘤细胞的受体状态。通过三种不同的分析方法，即配体（再）结合、核转位和hsp90共免疫沉淀，发现大多数糖皮质激素受体蛋白处于未激活的构象。此外，长时间暴露于地塞米松并不会导致激活受体水平的增加。通过原位评估受体激活，我们发现与室温相比，生理温度在解离hsp90方面效果较差。这些发现表明，生理温度对受体激活具有负向调控作用，这可能是由于激素与其同源受体之间存在热不稳定相互作用所致。
