Crystal Structure of the Glucocorticoid Receptor Ligand Binding Domain Reveals a Novel Mode of Receptor Dimerization and Coactivator Recognition

Abstract

Transcriptional regulation by the glucocorticoid receptor (GR) is mediated by hormone binding, receptor dimerization, and coactivator recruitment. Here, we report the crystal structure of the human GR ligand binding domain (LBD) bound to dexamethasone and a coactivator motif derived from the transcriptional intermediary factor 2. Despite structural similarity to other steroid receptors, the GR LBD adopts a surprising dimer configuration involving formation of an intermolecular beta sheet. Functional studies demonstrate that the novel dimer interface is important for GR-mediated activation. The structure also reveals an additional charge clamp that determines the binding selectivity of a coactivator and a distinct ligand binding pocket that explains its selectivity for endogenous steroid hormones. These results establish a framework for understanding the roles of protein-hormone and protein-protein interactions in GR signaling pathways.

Crystallization of protein–ligand complexes

“…The proteins shown are the soluble fractions from the Ni 2+ column. Lanes 3-5 show the purification of the F602S LBD (lane 3, sample after thrombin digestion; lane 4, Ni 2+ column flowthrough of the thrombin-digested material; lane 5, final purified protein; Bledsoe et al, 2002).…”

“…Expression studies with GR demonstrated that mutating the phenylalanine at position 602 to a serine residue (F602S), as in PR, led to increased expression of this receptor (Bledsoe et al, 2002;Fig. 2).…”

“…A multi-faceted approach of expression as a GST fusion, the presence of high-affinity ligands during cell growth, isolation under denaturing conditions, the F602S mutation and optimization of ligand type led to the growth of GR crystals and subsequent structure determinations (Bledsoe et al, 2002;Fig. 4).…”

How Do Corticosteroids Work in Asthma?

“…This suggests that the development of steroids with a greater margin of safety is possible and may even lead to the development of oral steroids that do not have significant adverse effects. The recent resolution of the crystal structure of glucocorticoid receptors may help to better design dissociated steroids (75).…”

Glucocorticoid receptor transcriptional isoforms and resistance in multiple myeloma cells

“…GR contains three functional domains: the NH 2 -terminal part or modulating domain involved in modulation of gene transcription (14); the DNA-binding domain involved in DNA binding, receptor dimerization (15), and gene transcription enhancement (16); and the ligand-binding domain that controls the activity of the receptor as a whole through its interaction with other proteins and glucocorticoids. In addition to ligand binding, the ligand-binding domain contains a receptor dimerization function (17,18) as well as domains for silencing of the receptor in the absence of the hormone (19,20).…”