«This is, in fact, the first time that we present to the scientific community a coherent mechanism to explain how the GR associates within the cell nucleus. “These results reaffirm the importance of continuing research to experimentally determine the three-dimensional structures of proteins and their complexes.”
The formation of these complexes occurs thanks to the interactions discovered by the team, which are specific to the ligand-binding domain of the GR. If in a previous study (Nucleic Acids Research2022) the team identified twenty different forms of association between the subunits, the new work goes further and defines which oligomeric forms are most relevant to the physiological function of the GR.
“The active conformation of the GR is clearly different from the traditional model that had been described for other nuclear receptors,” says researcher and also corresponding author Pablo Fuentes-Prior (IBUB). «As we already published in 2022, the functional unit is a non-canonical homodimer that associates through the first helices of the ligand binding domain. “This confirms that the GR has abnormal functioning compared to its counterparts.”
The new study confirms that this basic dimer is essential for the transcriptional function of the receptor “and, in addition, it functions as a kind of building block in a molecular Lego to form more complex structures.” “These structures, mostly tetramers, are what really represent the active form of GR when it binds to DNA,” emphasize Alegre-Martí and Jiménez-Panizo.
The active conformation of the GR demonstrates high plasticity in the interaction surface between dimers. This flexibility allows it to adopt a range of more “open” or more “closed” structures. “This oscillation between different conformations is essential to guarantee the correct functioning of the transcriptional machinery that the GR coordinates,” says Fuentes-Prior.
The GR, like a true “molecular contortionist,” is extremely flexible, capable of adopting multiple conformations and associating with various nuclear proteins. Specifically, this complexity has made its structural characterization difficult and, until now, only isolated structures of its DNA and ligand binding domains had been solved. To overcome this challenge, the new work has combined a set of cutting-edge techniques from structural and molecular biology, including X-ray crystallography using ALBA synchrotron radiation, molecular dynamics simulations, mass spectrometry, high-resolution fluorescence microscopy (Number and Brightness) and transcriptomic analysis through cellular RNA sequencing.
“This combined strategy was essential to overcome the difficulties inherent in the study of a protein of such high structural complexity,” the team details. “Thanks to this, we have been able to propose a detailed and coherent molecular mechanism for the interactions that drive glucocorticoid receptor multimerization.”
Mutations affecting the glucocorticoid receptor
Mutations in the GR gene can directly alter the multimerization process and, thus, cause aberrant forms and loss of functionality of the protein. This is what happens in Chrousos syndrome, a rare disease characterized by resistance to glucocorticoids and severe immune, metabolic and growth alterations.
The study expands knowledge about the molecular mechanisms of the disease associated with these mutations and presents an exhaustive catalog of pathological variants, located mainly on the surface of the ligand-binding domain. Unlike mutations in the hormone binding pocket – whose pathogenicity was already known – this work explains for the first time the effect of residue mutations on the surface of the domain associated with resistance to glucocorticoids, until now without a clear explanation. Some of these mutations weaken the dimer and interfere with its formation. More frequently, mutations increase the hydrophobicity of the receptor surface, forcing the formation of larger structures (hexamers and octamers) with reduced transcriptional activity.
«Apart from autoimmune and inflammatory diseases, these findings open new avenues to address pathologies associated with GR dysfunctions, including asthma, Cushing’s syndrome or Addison’s disease. In short, our research lays the foundations for the design of precision drugs capable of modulating GR function with unprecedented specificity,” concludes the research team.
Reference article:
Alegre-Martí, Andrea et al. «The multimerization pathway of the glucocorticoid receptor». Nucleic Acids ResearchOctober 2025. DOI: 10.1093/nar/gkaf1003.
