Activation of the glucocorticoid-receptor complex

Area of Science:

• Molecular Biology
• Cellular Biology
• Endocrinology

Background:

• Glucocorticoid receptor (GR) activation is essential for target cell interaction.
• This activation involves conformational changes in cytoplasmic GR complexes.
• Activated GR complexes facilitate binding to the cell nucleus.

Purpose of the Study:

• To investigate the biochemical mechanisms regulating GR activation.
• To identify factors influencing the rate and extent of GR activation.
• To characterize the structural and chemical changes associated with GR activation.

Main Methods:

• Quantification of GR activation by measuring binding to polyanions like DNA-cellulose.
• Separation of activated from unactivated GR complexes using ion exchange chromatography (DEAE-Sephadex/cellulose).
• In vitro studies using physical manipulations, chemical probes (pyridoxal 5'-phosphate, 1,10-phenanthroline), and phosphatase inhibitors/enzymes.

Main Results:

• GR activation occurs in vivo and can be enhanced in vitro by physical factors.
• A low molecular weight modulator in rat hepatic cytosol inhibits activation.
• Activation involves dephosphorylation and exposure of basic amino acid residues (lysine, arginine, histidine), potentially involving metal ions.

Conclusions:

• Glucocorticoid receptor activation is a regulated biochemical process with physiological relevance.
• Activation is influenced by cellular components, physical conditions, and post-translational modifications like dephosphorylation.
• Structural changes during activation expose DNA-binding sites and involve metal ions.