Unlocking the Secrets of Glucocorticoid Receptor Multimerization in Inflammation
Understanding how the glucocorticoid receptor (GR) forms complexes through the joining of multiple subunits is a pivotal breakthrough that could significantly enhance the development of more tailored medications. These innovative drugs aim to precisely modify this receptor interaction, potentially reducing serious side effects like immunosuppression and bone density loss.
The ambitious research was spearheaded by Eva Estébanez-Perpiñá, who serves as a Serra Húnter professor in the Department of Biochemistry and Molecular Biomedicine at the Faculty of Biology and the Institute of Biomedicine (IBUB) at the University of Barcelona, situated at the Barcelona Science Park (PCB). Young investigators Andrea Alegre-Martí and Alba Jiménez-Paniño from IBUB have earned recognition as the first co-authors of this significant paper.
This study is particularly noteworthy for its comprehensive, multidisciplinary approach that resulted from extensive collaboration across national and international research teams. This includes contributions from Gordon L. Hager of the US National Institutes of Health (NIH), Jaime Rubio, and M. Núria Peralta from the University of Barcelona’s Faculty of Chemistry and the Institute of Theoretical and Computational Chemistry (IQTCUB), along with members from various institutes such as the Mass Spectrometry and Proteomics core facility at the Institute for Research in Biomedicine (IRB Barcelona), Research Centre of Vine and Wine Related Science (ICVV-CSIC), the Institute of Biomedicine of Valencia (IBV-CSIC), and even overseas collaborators from the University of Buenos Aires in Argentina.
A Dynamic Protein with Many Shapes
For many years, the scientific consensus suggested that the GR operated solely as a monomer or a homodimer, meaning it existed either as a single unit or a pair of identical receptors. However, this new investigation challenges that long-standing belief, revealing for the first time that within the cell nucleus, the receptor can actually form larger oligomeric structures, predominantly consisting of four subunits, known as tetramers.
"The glucocorticoid receptor is essential in governing around 20% of the human transcriptome and plays a vital role in regulating blood sugar levels, metabolic processes, and the body’s anti-inflammatory responses," Professor Estébanez-Perpiñá explains.
"This is indeed the first occasion we provide the scientific community with a cohesive mechanism that elucidates how the GR behaves within the cell’s nucleus. Our findings underline the necessity for ongoing research aimed at experimentally determining the three-dimensional configurations of proteins and their associated complexes."
The complexes form thanks to specific interactions discovered by the research team that are particularly associated with the ligand-binding domain of the GR. In a prior study published in Nucleic Acids Research (2022), the team had identified 20 different interaction forms among the subunits, but this latest research goes deeper by classifying which oligomeric forms are critical for the GR’s physiological roles.
"The active structure of the GR markedly differs from the conventional model used for other nuclear receptors," states Pablo Fuentes-Prior, a researcher and co-author from IBUB. "As we noted in our 2022 paper, the functional unit resembles a non-canonical homodimer that connects via the initial helices of the ligand-binding domain. This reinforces that the GR operates differently than its related counterparts."
This new research substantiates that this fundamental dimer is crucial for the receptor's transcriptional activity and also acts as a building block, much like components of a LEGO set, to construct more intricate molecular configurations. "The structures we're observing, predominantly tetramers, are the true representation of the active GR when it engages with DNA," explain Alegre-Martí and Jiménez-Panizo.
The GR’s active configuration showcases significant adaptability in how its dimer interacts. This flexibility allows the receptor to transition between various states, either more open or more closed. Fuentes-Prior asserts, "This fluctuation between conformations is vital to ensure the transcriptional machinery that the GR orchestrates functions correctly."
Often referred to as a "molecular contortionist," the GR exhibits remarkable flexibility, enabling it to adopt numerous shapes and form associations with different nuclear proteins. This intricate nature has made it a challenge to characterize its structure, with successful revelations up to now only pertaining to its isolated DNA and ligand-binding domains. To address this complexity, the study employed an array of advanced methodologies from structural and molecular biology. This included X-ray crystallography utilizing synchrotron radiation at ALBA, molecular dynamics simulations, mass spectrometry, high-resolution fluorescence microscopy techniques, and cellular RNA analysis.
"This amalgamated approach was critical in tackling the challenges linked to studying such a structurally complex protein," the team notes. "As a result, we have proposed a detailed and coherent molecular mechanism that reveals how the glucocorticoid receptor undergoes multimerization."
The Impact of Mutations on the Glucocorticoid Receptor
Genetic mutations affecting the GR can disrupt the multimerization process, leading to dysfunctional proteins. This phenomenon is observed in Chrousos syndrome, a rare condition marked by glucocorticoid resistance, coupled with serious immune challenges, metabolic issues, and growth anomalies.
The findings contribute significantly to our understanding of the molecular underpinnings of diseases linked to these mutations, offering an extensive catalog of pathological variants predominantly found on the surface of the ligand-binding domain. Unlike previously recognized mutations in the hormone-binding site, which had already been tied to disease, this research also clarifies the impacts of mutations on the external residues of the domain related to glucocorticoid resistance, an area devoid of clear explanations until now. Some of these mutations diminish the stability of the dimer, thereby hindering its formation. Frequently, these mutations heighten the hydrophobic nature of the receptor's surface, compelling the assembly of larger structures like hexamers and octamers, which exhibit diminished transcriptional activities.
"Beyond autoimmune and inflammatory disorders, our discoveries pave new paths for addressing various ailments associated with GR dysfunction, including asthma, Cushing’s syndrome, and Addison’s disease. Ultimately, our research establishes a foundation for crafting precision medications capable of modulating GR activity with an unprecedented level of specificity," the research team concludes.
For further reading, refer to: Alegre-Martí A, Jiménez-Panizo A, Lafuente AL, et al. The multimerization pathway of the glucocorticoid receptor. Nucleic Acids Res. 2025;53(19):gkaf1003. doi: 10.1093/nar/gkaf1003 (https://doi.org/10.1093/nar/gkaf1003)
This article has been adapted from materials sourced from the University of Barcelona (https://web.ub.edu/en/web/actualitat/w/complexity-glucocorticoid-receptor?referer=news). Please note that some content may have been edited for clarity and brevity. For more information, kindly contact the original source. You can find our press release publishing policy here: (https://www.technologynetworks.com/tn/editorial-policies#republishing).
How do you view the implications of these findings for future therapies? Are there unresolved questions about GR multimerization that you think should be explored? Share your thoughts in the comments!
