Restored mutant receptor:Corticoid binding in chaperone complexes by trimethylamine N-oxide

Area of Science:

• Molecular biology
• Cell biology
• Biochemistry

Background:

• The glucocorticoid receptor (GR) is a transcription factor primarily located in the cytoplasm in its inactive state, bound by chaperones.
• Upon binding a glucocorticoid (GC) ligand, GR translocates to the nucleus to regulate gene expression.
• An
• activation-labile
• mutant GR (GRact/l) exhibits impaired GC binding under activating conditions.

Purpose of the Study:

• To investigate the effects of trimethylamine N-oxide (TMAO) on the function of the GRact/l mutant.
• To determine if TMAO can restore GC binding to the GRact/l mutant.

Main Methods:

• Experiments were conducted using both cell-free cytosols and intact cells.
• The GRact/l mutant was treated with varying concentrations of TMAO.
• GC binding to GRact/l was assessed in the presence and absence of TMAO.

Main Results:

• TMAO restored GC binding to the GRact/l mutant in both cell cytosols and intact cells.
• TMAO stabilized the GRact/l mutant in its chaperone-bound complex, preventing its activation-labile state.
• Lower concentrations of TMAO were effective in intact cells compared to in vitro, suggesting intracellular molecular crowding effects.

Conclusions:

• TMAO acts as a protective osmolyte that can rescue the GC-binding function of the GRact/l mutant.
• The findings suggest that intracellular molecular crowding, influenced by osmolytes like TMAO, plays a significant role in regulating GR activity.