GR Utilizes a Co-Chaperone Cytoplasmic CAR Retention Protein to Form an N/C Interaction

Area of Science:

• Molecular Biology
• Cellular Biology
• Endocrinology

Background:

• Nuclear receptors regulate gene expression via interactions between their N-terminal domain (NTD) and C-terminal ligand-binding domain (LBD).
• This N/C interaction is known in receptors like the androgen receptor but has not been previously observed in the glucocorticoid receptor (GR).

Purpose of the Study:

• To investigate the existence and regulation of an N/C interaction in GR.
• To determine the role of the co-chaperone CCRP in mediating this interaction.
• To explore the functional implications of the N/C interaction in GR.

Main Methods:

• Co-immunoprecipitation assays using GR fragments in COS-1 cells.
• Site-directed mutagenesis to create Y30F and Y30E GR mutants.
• 2D blue native/SDS-PAGE to analyze GR complex formation.
• cDNA microarray analysis to assess gene expression changes.

Main Results:

• Demonstrated an N/C interaction in GR, specifically involving the 26VMDFY30 motif in the NTD and the LBD.
• Showed that the co-chaperone CCRP is essential for inducing and stabilizing this GR N/C interaction.
• Identified Y30 as a critical residue, where a negative charge disrupts the interaction, suggesting its role as a regulatory phosphorylation site.

Conclusions:

• CCRP is essential for GR to form a stable N/C interaction.
• The N/C interaction, regulated by CCRP and potentially phosphorylation at Y30, plays a significant role in GR function.
• This finding provides new insights into the molecular mechanisms governing GR activity.