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Glucocorticoids are ubiquitous, pleotropic steroid hormones secreted from the cortices of the adrenal glands in a circadian fashion under the strong influence of the central Clock center located in the suprachiasmatic nuclei (SCN) of the hypothalamus. In previous work, we reported that the circadian transcription factor CLOCK and its heterodimer partner BMAL1 suppress the transcriptional activity of the glucocorticoid receptor (GR) by acetylating a lysine cluster located in its hinge region between the DNA- and ligand-binding domains. This regulation of GR transcriptional activity by CLOCK/BMAL1 functions as a counter-regulatory loop against the diurnally fluctuating circulating glucocorticoids. Here, we have performed further analyses of our data using bioinformatics and computational methods. Gene expression data were analyzed using unsupervised machine learning methods, such as hierarchical clustering, k-means, Naïve Bayes classification, and polynomial regression analyses. We determined expression patterns of Clock-related genes, unraveled the dynamics of spatial data, and defined the temporal function of Clock-mediated GR-regulated genes. Gene expressions manifested nonlinear dynamics, possibly because we obtained dynamic results from stationary measurements. The mechanics of the circadian rhythms are still obscure, and more studies are required to understand how such rhythms influence mammalian physiology. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Living organisms are highly complex systems that must maintain a dynamic equilibrium or homeostasis that requires energy to be sustained. Stress is a state in which several extrinsic or intrinsic disturbing stimuli, the stressors, threaten, or are perceived as threatening, homeostasis. To achieve homeostasis against the stressors, organisms have developed a highly sophisticated system, the stress system, which provides neuroendocrine adaptive responses, to restore homeostasis. These responses must be appropriate in terms of size and/or duration; otherwise, they may sustain life but be associated with detrimental effects on numerous physiologic functions of the organism, leading to a state of disease-causing disturbed homeostasis or cacostasis. In addition to facing a broad spectrum of external and/or internal stressors, organisms are subject to recurring environmental changes associated with the rotation of the planet around itself and its revolution around the sun. To adjust their homeostasis and to synchronize their activities to day/night cycles, organisms have developed an evolutionarily conserved biologic system, the "clock" system, which influences several physiologic functions in a circadian fashion. Accumulating evidence suggests that the stress system is intimately related to the circadian clock system, with dysfunction of the former resulting in dysregulation of the latter and vice versa. In this review, we describe the functional components of the two systems, we discuss their multilevel interactions, and we present how excessive or prolonged activity of the stress system affects the circadian rhythm of glucocorticoid secretion and target tissue effects. © 2017 Nicolaides, Charmandari, Kino and Chrousos.

Neural stem cells (NSCs) are pluripotent precursors with the ability to proliferate and differentiate into 3 neural cell lineages, neurons, astrocytes and oligodendrocytes. Elucidation of the mechanisms underlying these biologic processes is essential for understanding both physiologic and pathologic neural development and regeneration after injury. Nuclear hormone receptors (NRs) and their transcriptional coregulators also play crucial roles in neural development, functions and fate. To identify key NRs and their transcriptional regulators in NSC differentiation, we examined mRNA expression of 49 NRs and many of their coregulators during differentiation (0-5 days) of mouse embryonic NSCs induced by withdrawal of fibroblast growth factor-2 (FGF2). 37 out of 49 NRs were expressed in NSCs before induction of differentiation, while receptors known to play major roles in neural development, such as THR alpha, RXRs, RORs, TRs, and COUP-TFs, were highly expressed. CAR, which plays important roles in xenobiotic metabolism, was also highly expressed. FGF2 withdrawal induced mRNA expression of ROR gamma, RXR gamma, and MR by over 20-fold. Most of the transcriptional coregulators examined were expressed basally and throughout differentiation without major changes, while FGF2 withdrawal strongly induced mRNA expression of several histone deacetylases (HDACs), including HDAC11. Dexamethasone and aldosterone, respectively a synthetic glucocorticoid and natural mineralocorticoid, increased NSC numbers and induced differentiation into neurons and astrocytes. These results indicate that the NRs and their coregulators are present and/or change their expression during NSC differentiation, suggesting that they may influence development of the central nervous system in the absence or presence of their ligands.

Glucocorticoids, major end effectors of the stress response, play an essential role in the homeostasis of the central nervous system (CNS) and contribute to memory consolidation and emotional control through their intracellular receptors, the glucocorticoid and mineralocorticoid receptors. Cyclin-dependent kinase 5 (CDK5), on the other hand, plays important roles in the morphogenesis and functions of the central nervous system, and its aberrant activation has been associated with development of neurodegenerative disorders. We previously reported that CDK5 phosphorylated the glucocorticoid receptor and modulated its transcriptional activity. Here we found that CDK5 also regulated mineralocorticoid receptor-induced transcriptional activity by phosphorylating multiple serine and threonine residues located in its N-terminal domain through physical interaction. Aldosterone and dexamethasone, respectively, increased and suppressed mRNA/protein expression of brain-derived neurotrophic factor (BDNF) in rat cortical neuronal cells, whereas the endogenous glucocorticoid corticosterone showed a biphasic effect. CDK5 enhanced the effect of aldosterone and dexamethasone on BDNF expression. Because this neurotrophic factor plays critical roles in neuronal viability, synaptic plasticity, consolidation of memory, and emotional changes, we suggest that aberrant activation of CDK5 might influence these functions through corticosteroid receptors/BDNF. Copyright © 2010 by The Endocrine Society.

The availability of nutrients influences cellular growth and survival by affecting gene transcription. Glucocorticoids also influence gene transcription and have diverse activities on cell growth, energy expenditure, and survival. We found that the growth arrest-specific 5 (Gas5) noncoding RNA, which is abundant in cells whose growth has been arrested because of lack of nutrients or growth factors, sensitized cells to apoptosis by suppressing glucocorticoid-mediated induction of several responsive genes, including the one encoding cellular inhibitor of apoptosis 2. Gas5 bound to the DNA-binding domain of the glucocorticoid receptor (GR) by acting as a decoy glucocorticoid response element (GRE), thus competing with DNA GREs for binding to the GR. We conclude that Gas5 is a "riborepressor" of the GR, influencing cell survival and metabolic activities during starvation by modulating the transcriptional activity of the GR. Copyright 2008 the American Association for the Advancement of Science; all rights reserved.

Dehydration, and consequent intracellular hyperosmolarity, is a major challenge to land organisms as it is associated with extraction of water from cells and disturbance of global cellular function. Organisms have thus developed a highly conserved regulatory mechanism that transduces the hyperosmolarity signal from the cell surface to the cell nucleus and adjusts the expression of cellular osmolarity-regulating genes. We recently found that the Rho-type guanine nucleotide exchange factor Brx, or AKAP13, is essential for osmotic stress-stimulated expression of nuclear factor of activated T cells 5 (NFAT5), a key transcription factor of intracellular osmolarity. It accomplishes this by first attracting cJun kinase-interacting protein 4 and then coupling activated Rho-type small G-proteins to cascade components of the p38 MAPK signaling pathway, ultimately activating NFAT5. We describe the potential implications of osmotic stress and Brx activation in organ physiology and pathophysiology and connect activation of this system to key human homeostatic states. © 2010 Expert Reviews Ltd.

Extracellular hyperosmolarity, or osmotic stress, generally caused by differences in salt and macro-molecule concentrations across the plasma membrane, occurs in lymphoid organs and at inflammatory sites. The response of immune cells to osmotic stress is regulated by nuclear factor of activated T cells 5 (NFAT5), a transcription factor that induces the expression of hyperosmolarity-responsive genes and stimulates cytokine production. We report that the guanine nucleotide exchange factor (GEF) Brx [also known as protein kinase A-anchoring protein 13 (AKAP13)] is essential for the expression of nfat5 in response to osmotic stress, thus transmitting the extracellular hyperosmolarity signal and enabling differentiation of splenic B cells and production of immunoglobulin. This process required the activity of p38 mitogen-activated protein kinase (MAPK) and NFAT5 and involved a physical interaction between Brx and c-Jun N-terminal kinase (JNK)-interacting protein 4 (JIP4), a scaffold molecule specific to activation of the p38 MAPK cascade. Our results indicate that Brx integrates the responses of immune cells to osmotic stress and inflammation by elevating intracellular osmolarity and stimulating the production of cytokines.

HIV-1-infected patients may develop lipodystrophy and insulin resistance. We investigated the effect of the HIV-1 accessory protein viral protein R (Vpr) on the activity of the peroxisome proliferator-activating receptor-γ (PPARγ), a key regulator of adipocyte differentiation and tissue insulin sensitivity. We studied expression of PPARγ-responsive reporter genes in 3T3-L1 mouse adipocytes. We investigated Vpr interaction with the PPAR/retinoid X receptor (RXR)-binding site of the c-Cbl-associating protein (CAP) gene using the chromatin immunoprecipitation assay as well as the interaction of Vpr and PPARγ using coimmunoprecipitation. Finally, we studied the ability of exogenous Vpr protein to enter cultured adipocytes and retard differentiation. We found that Vpr suppressed PPARγ-induced transactivation in both undifferentiated and differentiated 3T3-L1 cells. Transcriptional suppression by Vpr required an intact LXXLL coactivator motif. Vpr suppressed mRNA expression of PPARγ-responsive genes in undifferentiated 3T3-L1 cells and associated with the PPAR/ RXR-binding site located in the promoter region of the CAP gene. Vpr interacted with the ligand-binding domain of PPARγ in an agonist-dependent fashion in vitro. Vpr delivered either by an expression plasmid or as protein added to media suppressed PPARγ agonist-induced adipocyte differentiation, assessed as lipid accumulation and mRNA expression of the adipocyte differentiation marker adipocyte P2 in 3T3-L1 cells. In conclusion, circulating Vpr or, alternatively, Vpr produced as a consequence of direct infection of adipocytes could suppress in vivo differentiation of preadipocytes by acting as a corepressor of PPARγ-mediated gene transcription. Vpr may alter sensitivity to insulin and thereby contribute to the development of lipodystrophy and insulin resistance observed in HIV-1-infected patients. Copyright © 2008 by The Endocrine Society.

Background Interleukin-6 and downstream liver effectors acute phase reactants are implicated in the systemic inflammatory reaction. Peroxisome proliferator-activated receptor delta (PPAR delta), which binds to and is activated by a variety of fatty acids, was recently shown to have anti-inflammatory actions. Materials and methods We examined the ability of the synthetic PPAR delta agonist GW501516 to suppress interleukin-6-induced expression of acute phase proteins in human hepatoma HepG2 cells and rat primary hepatocytes. Results GW501516 dose-dependently suppressed interleukin-6-induced mRNA expression of the acute phase protein alpha 1-antichymotrypsin in HepG2 cells. The compound also suppressed interleukin-6-induced mRNA expression of alpha 2-acid glycoprotein, beta-fibrinogen and alpha 2-macroglobulin in and the secretion of C-reactive protein by rat primary hepatocytes. Depletion of the PPAR delta receptor, but not of PPAR alpha or gamma, attenuated the suppressive effect of GW501516 on interleukin-6-induced alpha 1-antichymotrypsin mRNA expression, indicating that PPAR delta specifically mediated this effect. Since interleukin-6 stimulates the transcriptional activity of the alpha 1-antichymotrypsin promoter by activating the signal transducer and activator of transcription (STAT) 3, we examined functional interaction of this transcription factor and PPAR delta on this promoter. Overexpression of PPAR delta enhanced the suppressive effect of GW501516 on STAT3-activated transcriptional activity of the alpha 1-antichymotrypsin promoter, while GW501516 suppressed interleukin-6-induced binding of this transcription factor to this promoter. Conclusions These findings indicate that agonist-activated PPAR delta interferes with interleukin-6-induced acute phase reaction in the liver by inhibiting the transcriptional activity of STAT3. PPAR delta agonists might be useful for the suppression of systemic inflammatory reactions in which IL-6 plays a central role.

Background: The multifunctional inflammatory cytokine IL-6 regulates the acute phase reaction and plays central roles in the pathogenesis of chronic inflammatory disorders. Objectives: Two small chemical compounds, 3-O-formyl-20R,21-epoxyresibufogenin (TB-2-081) and 3-O-formyl-20S,21-epoxyresibufogenin (TB-2-082), known isolates from the Chinese toad skin extract drug Ch'an Su, were synthesized and tested on the IL-6-induced hepatic acute-phase reaction. Methods: HepG2 cells or rat primary hepatocytes were incubated with the compounds, and the effects on IL-6-induced expression of acute-phase molecules were tested. Results: TB-2-081, and to a lesser extent TB-2-082, suppressed IL-6-induced α1-antichymotrypsin (AACT) mRNA expression in HepG2 cells, whereas TB-2-081 failed to influence the mRNA expression of the TNF-α-induced mRNA expression of the methionine adenosyltransferase 2A gene in these cells. TB-2-081 suppressed IL-6-induced mRNA expression of α1-acid glycoprotein, α2-macroglobulin, and β-fibrinogen in and secretion of the C-reactive protein by rat primary hepatocytes. TB-2-081 shifted the IL-6 dose-response curve of the AACT mRNA expression right and downward and inhibited IL-6-induced phosphorylation of signal transducer and activator of transcription 3. In addition to IL-6, TB-2-081 inhibited IL-11-stimulated and oncostatin M-stimulated AACT mRNA expression independently of the IL-6 receptor subunit. The soluble glycoprotein 130, but not the soluble IL-6 receptor, antagonized TB-2-081-induced suppression of IL-6-stimulated AACT mRNA expression. Conclusion: TB-2-081 inhibits IL-6-type cytokine action by attenuating the function of the common receptor subunit glycoprotein 130. Clinical implications: This class of compounds may be beneficial for the treatment of diseases in which excessive circulation/production/action of IL-6-type cytokines play pathologic roles. © 2007 American Academy of Allergy, Asthma & Immunology.

Glucocorticoids regulate many crucial biologic functions through their cytoplasmic/nuclear glucocorticoid receptors (GR). Excess, deficiency, or alteration in tissue sensitivity to glucocorticoids has been associated with major causes of human morbidity and mortality. Brx, a cytoplasmic Rho family guanine nucleotide exchange factor, binds to and influences the activity of several nuclear hormone receptors. We examined the functional and molecular interactions between GR and Brx. The glucocorticoid sensitivity of lymphocytes obtained from mice haplo-insufficient for Brx was significantly decreased. Conversely, GR-mediated transcriptional activity of a glucocorticoid response element (GRE)-mediated glucocorticoid-responsive promoter was enhanced by Brx in a guanine nucleotide exchange factor domain-dependent fashion. Brx interacted with GR, forming a ternary complex with RhoA. In a chromatin immunoprecipitation assay, Brx and RhoA were co-precipitated with GREs only in the presence of ligand-activated GR. Extracellularly administered lysophosphatidic acid, which activates its signaling cascade through a specific membrane GTP-binding protein (G-protein)-coupled receptor in a G-protein alpha(13)-, Brx-, and RhoA-dependent fashion, enhanced GR transcriptional activity, whereas depletion of endogenous Brx attenuated this effect. These findings suggest that glucocorticoid signaling and, hence, the tissue sensitivity to glucocorticoids, may be coupled to extracellular signals via Brx and small G-proteins. Nuclear Brx might act as a local GRE-GR-transcriptosome activator by mediating the effect of small G-proteins on glucocorticoid-regulated genes.

The hypothalamic-pituitary-adrenal axis (a major component of the stress system) and the immune system contribute to the maintenance of homeostasis at rest and during stress. Because of their essential roles for the survival of self and species, the activities of these systems have evolutionarily developed in parallel and are intertwined at many levels. In this issue of the JCI, Ezzat et al. demonstrate that Ikaros, a differentiation factor of leukocyte lineage, also influences the maturation of the fetal pituitary corticotroph and, hence, the secretion of adrenocorticotropic hormone before and after birth (see the related article beginning on page 1021). These results indicate that Ikaros is an ontogenetic and phylogenetic integrator of the stress and immune systems and that abnormalities in its function may produce endocrine and/or immune pathologies.

Glucocorticoids play pivotal roles in the maintenance of homeostasis but, when dysregulated, may also have deleterious effects. Smad6, one of the transforming growth factor beta ( TGF beta) family downstream transcription factors, interacts with the N-terminal domain of the glucocorticoid receptor ( GR) through its Mad homology 2 domain and suppresses GR-mediated transcriptional activity in vitro. Adenovirus-mediated Smad6 overexpression inhibits glucocorticoid action in rat liver in vivo, preventing dexamethasone-induced elevation of blood glucose levels and hepatic mRNA expression of phosphoenolpyruvate carboxykinase, a well known rate-limiting enzyme of liver gluconeogenesis. Smad6 suppresses GR-induced transactivation by attracting histone deacetylase 3 to DNA-bound GR and by antagonizing acetylation of histone H3 and H4 induced by p160 histone acetyltransferase. These results indicate that Smad6 regulates glucocorticoid actions as a corepressor of the GR. From our results and known cross-talks between glucocorticoids and TGF beta family molecules, it appears that the anti-glucocorticoid actions of Smad6 may contribute to the neuroprotective, anticatabolic and pro-wound healing properties of the TGF beta family of proteins.

The hypothalamic-pituitary-adrenal axis (a major component of the stress system) and the immune system contribute to the maintenance of homeostasis at rest and during stress. Because of their essential roles for the survival of self and species, the activities of these systems have evolutionarily developed in parallel and are intertwined at many levels. In this issue of the JCI, Ezzat et al. demonstrate that Ikaros, a differentiation factor of leukocyte lineage, also influences the maturation of the fetal pituitary corticotroph and, hence, the secretion of adrenocorticotropic hormone before and after birth (see the related article beginning on page 1021). These results indicate that Ikaros is an ontogenetic and phylogenetic integrator of the stress and immune systems and that abnormalities in its function may produce endocrine and/or immune pathologies.

Glucocorticoids contribute fundamentally to the maintenance of basal and stress-related homeostasis in all higher organisms. The major roles of these steroids in physiology are amply matched by their remarkable contributions to pathology. Glucocorticoids influence about 20% of the expressed human genome, and their effects spare almost no organs or tissues. For many years we thought that the numerous actions of glucocorticoids were mediated by a single receptor molecule: the classic glucocorticoid receptor (GR) isoform alpha, a complex, multifunctional domain protein, operating as a ligand-dependent transcription factor. The GR gene, however, encodes two 3' splicing variants, GRalpha and GRbeta, from alternative use of two distinct terminal exons (9alpha and 9beta), and each variant mRNA is translated from at least eight initiation sites into multiple GRalpha and possibly GRbeta isoforms, amounting to a minimum of 16 GR monomers and 256 different homo- or heterodimers. The translational GRalpha isoforms may be produced variably in target tissues, have varying intrinsic transcriptional activities, and influence different complements of glucocorticoid-responsive genes. It is likely that expression and functional differences might also be present between the putative GRbeta translational isoforms. The presence of multiple GR monomers and dimers in different quantities with quantitatively and qualitatively different transcriptional activities suggests that the glucocorticoid signaling system is highly stochastic.

Background We previously reported that the guanine tri-phosphate-binding proteins (G) beta and gamma are both localized in the nucleus, in addition to their expected cytoplasmic/plasma membrane localization. These proteins, as a heterodimeric complex, suppress glucocorticoid response element-mediated transcriptional activity of the glucocorticoid receptor through direct physical interactions between G beta and the glucocorticoid receptor. Materials and methods As G gamma is prenylated at a cysteine residue in its C-terminal portion, and as this post-translational modification is required for many of the known G beta/G gamma activities, we examined the effect of its absence or diminution on G beta/G gamma-induced suppression of glucocorticoid receptor-induced transcriptional activity. Results In a functional reporter assay, G gamma 2C68S, which is defective at the prenylation site, was more potent than the wild-type G gamma 2 at increasing G beta 2-induced suppression of glucocorticoid receptor transactivation. Interestingly, the enhanced green fluorescent protein fusion of this mutant G gamma 2 was localized preferentially in the nucleus, while it was absent from the plasma membrane. Lovastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor that abrogates the prenylation of G gamma, shifted the subcellular localization of enhanced green fluorescence protein-fused G gamma 2 and G beta 2 from the cytoplasm/plasma membrane to the nucleus and further suppressed glucocorticoid receptor-induced transcriptional activity. Conclusions These findings indicate that not only is the natural covalent addition of the prenyl residue to G gamma unnecessary for the transcriptional suppression induced by G beta/G gamma on the glucocorticoid receptor, but rather helps retain the G beta/G gamma complex away from the nucleus decreasing its antiglucocorticoid actions.

L-Carnitine (3-hydroxy-4-N,N,N-trimethylaminobutyrate) is a conditionally essential nutrient with a major role in cellular energy metabolism. It is available in the United States as both a prescription drug and an over-the-counter nutritional supplement. Accumulating evidence from both animal and human studies indicates that pharmacologic doses of L-carnitine (LCAR) have immunomodulatory effects resembling those of glucocorticoids (GC). On the other hand, in contrast to GC, which cause bone loss, LCAR seems to have positive effects on bone metabolism. To explore the molecular bases of this GC-like activity of LCAR, we investigated its effects on glucocorticoid receptor (GR)-modulated cytokine release ex vivo, and on the transcriptional activity, intracellular trafficking, and binding of GR in vitro. At high noncytotoxic doses, LCAR (a) suppressed the lipopolysaccharide-stimulated release of tumor necrosis factor α and interleukin-12 from primary human monocytes in a GC-like fashion, (b) stimulated the transcriptional activity of GR on the GC-responsive promoters, (c) triggered nuclear translocation of green fluorescent protein (GFP)-fused GR, and (d) reduced the whole cell binding of [3H]-dexamethasone to GR. These results suggest that LCAR is a "nutritional modulator" of the GR, by acting as an agonist-like compound. Since LCAR appears to have positive effects on bone metabolism, in contrast to GC, LCAR may share some of the therapeutic properties of GC, particularly on the immune system, but not their deleterious side effects on some of other organs/ tissues. Thus, LCAR is potentially a useful alternative compound of GC in particular therapeutic situations. The clinical and therapeutic implications of these findings, as well as a better understanding of their mechanisms, warrant further research.

Natural mutations of the human glucocorticoid receptor (GR) isoform alpha cause the glucocorticoid resistance syndrome. Mutant receptors may have abnormal interactions with the ligand, target DNA sequences, and/or multiple intracellular proteins, as well as aberrant nucleocytoplasmic trafficking. Using fluorescence recovery after photobleaching (FRAP) analysis, all GR pathologic mutant receptors examined, as well as 2 synthetic GR mutants lacking the activation function (AF)-1 or the ligand-binding domain (and hence the AF-2), had defective transcriptional activity and dynamic motility defects inside the nucleus of living cells. In the presence of dexamethasone, these mutants displayed a curtailed 50% recovery time ((1/2)) after photobleaching and, hence, significantly increased intranuclear motility and decreased “chromatin retention.” The t(1/2) values of the mutants correlated positively with their transcriptional activities and depended on the GR domain affected. GR beta, a natural splice variant of the GR gene, also demonstrated a shorter t(1/2) than GR alpha. The motility responsiveness of the natural and artificial mutant receptors examined, and of GR beta, to the proteasomal inhibitor MG-132 also depended on the mutant domain. Thus, mutant glucocorticoid receptors possess dynamic motility defects in the nucleus, possibly caused by their inability to properly interact with all key partner nuclear molecules necessary for full activation of glucocorticoid-responsive genes.

BACKGROUND: Alternative splicing of the transcripts of the human glucocorticoid receptor gene results in two mutually exclusive products, the classic, ligand-binding glucocorticoid receptor (hGR alpha), and a dominant negative non-ligand-binding isoform, hGR beta. MATERIALS AND METHODS: We examined the existence of and quantified both hGR alpha and hGR beta isoforms in a panel of human tissues, as well as in intact and fractionated HeLa cells, using specific quantitative Western blots and/or immunocytochemistry. We studied the potential interactions of hGR beta with heat shock protein (hsp) 90 and/or hGR alpha using cross-immunoadsorption/precipitation procedures followed by Western blots. RESULTS: For the first time, we demonstrated the natural existence of the hGR beta protein, which was widely expressed in human tissues. The ratio of immunoreactive hGR alpha to hGR beta varied from 0.2 to 1.0 among different tissues, and was approximately 0.2 in HeLa cells. In the latter, both isoforms were distributed in the cytoplasm and nucleus in the absence of the hormonal ligand, and translocated into the nucleus after addition of dexamethasone. The cytosolic and nuclear hGR alpha-to-hGR beta ratio remained the same before and after dexamethasone exposure, suggesting that upon activation the two isoforms translocated into the nucleus in equal proportions. hGR alpha- and hGR beta-specific antibodies cross-adsorbed and precipitated cytosolic and nuclear glucocorticoid hGR alpha and hGR beta, respectively, as well as hsp90, suggesting that hGR alpha and hGR beta are in complex with hsp90 and/or each other. CONCLUSIONS: The hGR beta protein is widely expressed throughout the human body and present mostly in the cytoplasm of human cells, in complex with hsp90 and other proteins. In the presence of glucocorticoid, hGR beta probably heterodimerizes with ligand-bound hGR alpha and translocates into the nucleus to act as a dominant negative inhibitor of the classic receptor.