INTERACTION OF THE LIGAND-ACTIVATED GLUCOCORTICOID RECEPTOR WITH THE 14-3-3-ETA PROTEIN

The glucocorticoid receptor (GR) is a ligand-activated transcription f actor. In this study, we used the yeast two-hybrid system to isolate c DNAs encoding proteins that interact with the human GR ligand-binding domain (LBD) in a ligand-dependent manner, One isolated cDNA from a He La cell library encoded the COOH-terminal portion of the eta-isoform o f the 14-3-3 protein (residues 187-246). Glucocorticoid agonists, tria mcinolone acetonide and dexamethasone, induced the GR LBD/14-3-3 eta p rotein fragment interaction, but an antagonist, RU486, did not. Glutat hione S-transferase pull-down experiments in vitro showed that full-le ngth 14-3-3 eta protein also interacted with the activated GR. Transie nt transfection studies using COS-7 cells revealed a stimulatory effec t of 14-3-3 eta protein on transcriptional activation by the Oh. The 1 4-3-3 family members have recently been found to associate with a numb er of important signaling proteins, such as protein kinase C and Raf-1 , as functional modulators, Our findings suggest a novel regulatory ro le of 14-3-3 eta protein in GR-mediated signaling pathways and also po int to a mechanism whereby GR may cross-talk with other signal transdu ction systems.