Intertwined Domain Requirements for Dimerization of the Glucocorticoid Receptor

AGUSTINA L. LAFUENTE; ALBA JIMENEZ-PANIZO; THEOPHILUS TETTEY; R. LOUIS SCHILTZ; ADALI PECCI; PABLO FUENTES-PRIOR; EVA ESTÉBANEZ-PERPIÑÁ; GORDON L. HAGER; MARIA FLORENCIA OGARA; DIEGO M PRESMAN

CABA

Simposio; Frontiers in Bioscience 4; 2023

IBioBA - CONICET ? Partner Institute of the MaxPlanck Society

Glucocorticoids (GCs) are steroid hormones that have a major role in the clinic due to their powerful anti-inflammatory and immunosuppressive actions. Unfortunately, their chronic use is linked to severe metabolic side effects. GCs act through the glucocorticoid receptor (GR), a ubiquitous transcription factor organized into three structural and functional domains: the NTD (N-terminal domain), DBD (DNA binding domain), and LBD (ligand binding domain). A relationship between the quaternary structure of GR and its transcriptional activity is still accepted. This paradigm establishes that monomeric GR is unable to bind DNA directly and is responsible for its anti-inflammatory effects. On the other hand, GR dimers can bind to DNA, and promote the transactivation of genes associated with metabolic side effects. This monomer-dimer dichotomy encouraged the search for dissociated GCs that could favor a monomeric state of GR. However, up to date, there is no synthetic glucocorticoid exempt from serious side effects. Using the microscopy technique Number and Brightness (N&B), our lab has previously characterized the oligomerization state of full-length GR in living cells. Our results indicate that, after stimulation, GR is mostly dimeric in the nucleoplasm, and DNA binding triggers tetramerization of the receptor, which we proposed as the final active form. We found no evidence to support a functional role for the monomeric GR. Here, we performed N&B assays on selected GR mutants designed from new crystal structures of GR LBD. Our data suggest that several topologically distinct GR dimers co-exist within the nucleoplasm of live cells and that GR dimerization depends, at least in part, on the allosteric communication between the DBD and LBD domains. These results open new venues in the search for safer glucocorticoid treatments.