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J Carlstedt-Duke

Publications and source records attributed to J Carlstedt-Duke.

At least 19 recordsLinked to original sources
PubMed2001

Cellular estrogen activity: implications for pulsed estrogen therapy.

Estrogens exert their principal biological effects through the actions of two different intracellular estrogen receptor (ER) proteins, ER alpha and ER beta. Following the binding of steroid, the protein undergoes a conformational change that results in a transcriptionally active form. The receptor protein is locked into an active state by estradiol, which results in the transition of the receptor through a signal transduction cascade of events, ultimately resulting in the activation of specific genes, thereby inducing the biological events specific for that type of target cell. There is a large variation in the relative expression levels of the two ER isoforms in different target tissues and in different stages of development. In addition, variant forms of the two ER isoforms, the result of splice variation, have been described. ER alpha and ER beta have been shown to differ in specific aspects within the various stages of the signal transduction pathway. Thus, there is a broad spectrum of estrogen response mechanisms as a result of an infinite number of possible combinations of all these factors. In addition, there are gene regulatory mechanisms that are the result of ER--protein interactions instead of ER--DNA interactions. Steroid binding is the key initiating action of the whole pathway, which, in terms of cell biology, is a relatively slow process. The response induced through the action of ER induction can be shown to be dependent on the total dose exposure rather than estradiol concentrations at subsaturating levels.

Estrogen Replacement Therapy↗
PubMed2001

Characterization of two novel mutations in the glucocorticoid receptor gene in patients with primary cortisol resistance.

OBJECTIVE: Primary glucocorticoid resistance is characterized by decreased sensitivity to cortisol signalling. We have performed genetic analysis of the glucocorticoid receptor (GR) gene in 12 unrelated patients with primary cortisol resistance as defined by a pathological dexamethasone suppression test. METHODS: Exon specific polymerase chain reaction amplification of the GR gene and sequencing of each exon was carried out. The two mutations were characterized in vitro in terms of glucocorticoid driven reporter gene activity in a transient transfection assay and in a ligand binding assay. Molecular modelling of the R477H mutant was performed based on the X-ray structure of the GR-DNA binding domain. RESULTS: Two novel mutations in the GR gene were found: R477H in the DNA-binding domain which is the first reported mutation in that region of the human GR gene and G679S in the ligand binding domain. The R477H mutation showed no transactivating capacity, whereas the G679S mutation had reduced transactivation capacity compared to the wild-type (wt) GR. When tested for ligand binding capacity, the G679S mutation had 50% binding affinity compared to the wt GR. The effect of the point mutation R477H was deduced by a comparison between the wt structure and the model of the mutant. The wt GR has direct and water mediated contact with the phosphate groups of the glucocorticoid responsive element (GRE) whereas, in the model, the mutation R477H has no contact with the GRE. The G679S mutation is located on the surface of the ligand binding domain, at a distance from the steroid-binding site. A previously reported polymorphism, AAT to AAC at amino acid position 766, was found in four of the patients. CONCLUSIONS: In two of 12 patients with clinical glucocorticoid resistance, mutant forms of GR could be found. The glucocorticoid resistance in vivo in these two patients corresponds to impaired function of the two mutated GR forms in two in vitro assays. The relevance of the conservative polymorphism for the glucocorticoid insensitivity noted in these patients remains to be clarified.

Adult↗
PubMed2000

Functional probing of the human glucocorticoid receptor steroid-interacting surface by site-directed mutagenesis. Gln-642 plays an important role in steroid recognition and binding.

To elucidate which amino acids in the glucocorticoid receptor ligand-binding domain might be involved in determining steroid binding specificity by interaction with the D-ring of glucocorticoids, we have performed site-directed mutagenesis of the four amino acids Met-560, Met-639, Gln-642, and Thr-739 based on their proximity to the steroid in a model structure. Mutations of these residues affected steroid binding affinity, specificity, and/or steroid-dependent transactivation. The results indicate that these residues are located in close proximity to the ligand and appear to play a role in steroid recognition and/or transactivating sensitivity, possibly by changes in the steroid-dependent conformational change of this region, resulting in the formation of the AF-2 site. Mutation of Gln-642 resulted in a marked decrease in affinity for steroids containing a 17alpha-OH group. This effect was alleviated by the presence of a 16alpha-CH(3) group to a varying degree. Thr-739 appears to form a hydrogen bond with the 21-OH group of the steroid, as well as possibly forming hydrophobic interactions with the steroid. Met-560 and Met-639 appear to form hydrophobic interactions with the D-ring of the steroid, although the nature of these interactions cannot be characterized in more detail at this point.

Animals↗
PubMed1999

Valine 571 functions as a regional organizer in programming the glucocorticoid receptor for differential binding of glucocorticoids and mineralocorticoids.

The glucocorticoid receptor (GR) interacts specifically with glucocorticoids, whereas its closest relative, the mineralocorticoid receptor (MR), interacts with both glucocorticoids and mineralocorticoids, such as aldosterone. To investigate the mechanism underlying the glucocorticoid/mineralocorticoid specificity of the GR, we used a yeast model system to screen for GR ligand-binding domain mutants, substituted with MR residues in the segment 565-574, that can be efficiently activated by aldosterone. In all such increased activity mutants, valine 571 was replaced by methionine, even though most mutants also contained substitutions of other residues with their MR counterparts. Further analysis in yeast and COS-7 cells has revealed that the identity of residue 571 determines the behavior of other MR substituted residues in the 565-574 segment. Generally, MR substitutions in this region are only consistent with aldosterone binding if residue 571 is also replaced with methionine (MR conformation). If residue 571 is valine (GR conformation), most other MR substitution mutants drastically reduce interaction with both mineralocorticoid and glucocorticoid hormones. Based on these functional data, we hypothesize that residue 571 functions as a regional organizer involved in discriminating between glucocorticoid and mineralocorticoid hormones. We have used a molecular model of the GR ligand-binding domain in an attempt to interpret our functional data in structural terms.

Aldosterone↗
PubMed1999

Involvement of tyrosine kinases on cyclooxygenase expression and prostaglandin E2 production in human gingival fibroblasts stimulated with interleukin-1beta and epidermal growth factor.

The purpose of the present study was to investigate the involvement of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and tyrosine kinase on prostaglandin E2 (PGE2) production in human gingival fibroblasts stimulated by interleukin-1beta (IL-1beta) and/or epidermal growth factor (EGF). The cytokine IL-1beta and to a lesser extent EGF, enhanced COX-2 mRNA levels in gingival fibroblasts. Simultaneous treatment with EGF and IL-1beta resulted in enhanced COX-2 mRNA levels accompanied by a synergistic stimulation of PGE2 biosynthesis compared to the cells treated with IL-1beta or EGF alone. Neither IL-1beta EGF nor the combination of IL-1beta and EGF enhanced COX-1 mRNA levels in gingival fibroblasts. The tyrosine kinase inhibitors, Herbimycin A and PD 153035 hydrochloride, reduced COX-2 mRNA levels as well as PGE2 production induced by IL-1beta or the combination of IL-1beta and EGF whereas COX-1 mRNA levels were not affected. Furthermore, the COX-2 specific inhibitor, NS-398, abolished the PGE2 production induced by IL-1beta, EGF, or the combination. These results indicate that the synergy between IL-1beta and EGF on PGE2 production is due to an enhanced gene expression of COX-2 and that tyrosine kinase(s) are involved in the signal transduction of COX-2 in gingival fibroblasts.

Benzoquinones↗
PubMed1999

Glucocorticoid Receptor beta: View II.

There is a clear role for mechanisms that modulate glucocorticoid receptor (GR) function. The non-steroid-binding GRbeta isoform has been proposed to play a role in this modulation but the published data are contradictory. The relative levels of this isoform appear to be low. Alternative mechanisms for the modulation of glucocorticoid action are described and contrasted with the proposed role for GRbeta.

Journal Article↗
PubMed1999

Dental maturity in children of short stature--a two-year longitudinal study of growth hormone substitution.

The aim of this investigation was to present the 2-year follow-up results of a longitudinal study examining the influence of growth hormone (GH) substitution on dental maturity in healthy children of short stature (height <2 SD). At baseline, the children were divided into a GH-deficient group and a GH non-deficient group, and comparisons were made with healthy controls (height between -2 SD and 2 SD) and between the short stature groups. The GH-substituted group included 24 children (8 F, 16 M) with a mean chronological age of 12.20 +/- 2.40 years, whereas the GH non-substituted group included 19 children (5 F, 14 M) with a mean chronological age of 11.00 +/- 2.40 years. The corresponding age- and sex-matched control groups constituted 48 and 36 children, respectively. The mean dental age in the GH-substituted group was 11.60 +/- 2.70 years, compared to their healthy controls 12.40 +/- 2.60 years (P< 0.05). The dental age for the GH non-substituted children was 10.20 +/- 2.60 years compared to their controls 11.90 +/- 2.60 years (P< 0.001). GH-substituted children show an acceleration in their dental maturity in contrast to controls, whereas in non-substituted children the acceleration is less pronounced.

Adolescent↗
PubMed1998

Identification of a functional glucocorticoid response element in the CYP3A1/IGC2 gene.

The rat CYP3A subfamily of cytochrome P450 consists of steroid- and drug-metabolizing enzymes inducible by pregnenolone 16alpha-carbonitrile and by supra-physiological doses of dexamethasone. The induction of CYP3A by dexamethasone has been proposed to be mediated by a mechanism distinct from the glucocorticoid receptor mediated response. However, a synergistic induction of CYP3A has been observed with physiological doses of glucocorticoids and other CYP3A inducers. We have identified the presence of a glucocorticoid-responsive element in the CYP3A1/IGC2 gene that mediates the induction with physiological doses of glucocorticoids. A 219-bp dexamethasone responsive fragment of the CYP3A1/IGC2 gene localized at -2100/-1882 bp upstream of the transcription initiation site was identified in transfection experiments with HepG2 cells. Maximum induction was achieved with 50-100 nM dexamethasone. DNase I footprinting analysis revealed two glucocorticoid receptor-protected sequences in the 5' flank of the CYP3A1/IGC2 gene. Point mutations in footprint I (-1982/-1960-bp) completely abolished binding and transcription activation whereas a mutation in footprint II (-2001/-1986-bp) only decreased the binding and had no effect on transcription activation. These results led to the conclusion that the glucocorticoid response element present in footprint I mediated the dexamethasone response in transfection experiments with HepG2 cells. Pregnenolone 16alpha-carbonitrile failed to induce any transcriptional effect mediated by this response element in the HepG2 cells.

Animals↗
PubMed1997

A weak TATA box is a prerequisite for glucocorticoid-dependent repression of the osteocalcin gene.

The TATA box element is not only important for establishing basal levels of transcription, but it can also be used to modulate cell type or stage specific gene activity. In the case of the human osteocalcin gene, which is transcriptionally repressed by glucocorticoids, a specific binding element for the glucocorticoid receptor (GR) overlaps a noncanonical TATA box. In the present study, the relevance and function of the TATA element in glucocorticoid-mediated repression of the human osteocalcin gene was characterized. Mutating this noncanonical TATA box into a consensus TATA box within the context of the osteocalcin promoter greatly decreased hormone-dependent transcriptional repression by GR. TATA-binding protein (TBP) bound this mutated element much more strongly suggesting a physiologically relevant role for the weak osteocalcin TATA element in the regulation of this bone specific gene. The optimization of the putative transcription factor IIB recognition site did not affect the level of GR-mediated repression. Our results support a model wherein competitive DNA binding of GR and TBP for their overlapping sites explains conditional repression of the osteocalcin gene by glucocorticoids.

Binding, Competitive↗
PubMed1997

Evidence that the beta-isoform of the human glucocorticoid receptor does not act as a physiologically significant repressor.

Alternative splicing of the human glucocorticoid receptor (hGR) primary transcript generates two receptor isoforms, hGRalpha and hGRbeta, with different carboxyl termini diverging at amino acid 727. By reverse transcriptase-polymerase chain reactions it was previously demonstrated that the hGRbeta message had a widespread tissue distribution. To demonstrate the presence of hGRbeta as protein we produced specific rabbit antisera to hGRbeta, as well as a hGRbeta-specific mouse monoclonal IgM antibody, by peptide immunizations. By SDS-polyacrylamide gel electrophoresis and Western immunoblotting we showed that hGRbeta is endogenously expressed at the protein level in HeLa cells and human lymphatic leukemia cells. Using an antibody directed against an epitope shared by both isoforms we showed a relatively lower expression of the hGRbeta form. We also showed that hGRbeta bound to hsp90 by immunoprecipitation of in vitro translated hGRbeta in reticulocyte lysate with hsp90-specific antibodies, a coprecipitation occurring also in the presence of dexamethasone. We could not demonstrate that hGRbeta inhibited the effects of dexamethasone-activated hGRalpha on a glucocorticoid-responsive reporter gene. In conclusion, low hGRbeta expression levels and hGRbeta-hsp90 interaction maintained in the presence of ligand and lack of inhibition of hormone-activated hGRalpha effects challenge the concept of the hGRbeta isoform as a proposed dominant negative inhibitor of hGRalpha activity.

Alternative Splicing↗
PubMed1997

The rat glucocorticoid receptor mutant K461A differentiates between two different mechanisms of transrepression.

The glucocorticoid receptor (GR) can both activate and repress transcription of target genes by interaction with specific genomic response elements, glucocorticoid response elements (GREs). Activation of transcription is usually the result of the direct interaction between GR and the GRE, whereas GR-mediated transcription repression is either the result of the indirect action of GR, mediated by a response element as a result of protein.protein interaction or by an occlusion mechanism in which GR displaces a general or regulatory transcription factor. A specific mutation of rat GR, K461A, has previously been described to transform the indirect protein.protein interaction-dependent transrepressive effect of GR into an activating function (Starr, D. B., Matsui, W., Thomas, J. R., and Yamamoto, K. R. (1996) Genes Dev. 10, 1271-1283). In HOS D4 and COS7 cells, this mutation was shown to transform the transrepressive effect of wild-type GR, acting on reporter constructs containing the composite GRE from the proliferin gene (plfG) or the negative tethering GRE from the collagenase A promoter (colA), into an activating function. In contrast, the K461A mutation had no effect on the transrepressive effect of GR on the human osteocalcin gene in which repression apparently occurs through the binding of GR to a negative GRE that overlaps the TATA box. The transrepressive function, typically 40% of the basal level in the absence of hormone, required only the isolated DNA-binding domain of wild type or mutant GR and was independent of the nature of transactivation domain. Thus, mutation of rat GR at position 461 differentiates between transrepressive functions of GR dependent on GR.DNA interaction (repression by occlusion) and GR.protein interaction (active repression).

Animals↗
PubMed1997

Glucocorticoid-dependent transcriptional repression of the osteocalcin gene by competitive binding at the TATA box.

The human osteocalcin gene is transcriptionally repressed by glucocorticoids. A specific binding element for the glucocorticoid receptor (GR) overlapping the TATA box of the human osteocalcin promoter has previously been identified. In the present study, the function of this element has been further characterized by competitive gel mobility-shift assay and transfection experiments. The GR and TATA-binding protein (TBP) bound to the cognate overlapping elements in a mutually exclusive manner. The GR preferentially inhibited the binding of TBP. The isolated DNA-binding domain of the GR is sufficient to compete for TBP binding. The integrity of both half-sites of the glucocorticoid response element (GRE) is required to effectively compete for TBP binding, and competitive binding of the GR is dependent on dimerization. Transient overexpression of TBP overrides the transcriptional repression of the osteocalcin promoter by glucocorticoids. We conclude that the repressive effect of glucocorticoids on this promoter is the result of competitive DNA binding to a basal transcriptional element and that it does not appear to require direct protein-protein interaction between the competitive factors.

Base Sequence↗
PubMed1997

Dental maturity in children of short stature, with or without growth hormone deficiency.

The aim of this investigation was to study dental maturity in healthy prepubertal children of short stature (height<-2 SD), with or without growth hormone (GH) deficiency, compared to healthy controls. The GH-deficient group (GH level<10.0 microg/l) included 29 children (11 female, 18 male) with a mean age of 10.2+/-2.2 years. The GH non-deficient group consisted of 17 children (5 female, 12 male) with a mean age of 8.5+/-2.1 years. All the children were evaluated for serum concentrations of IGF-1, alkaline phosphatase (ALP), triiodthyronin (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and fasting plasma insulin; height and bone age were also recorded. Dental maturity was determined from panoramic radiographs. The mean difference between the dental and chronological ages was -0.67+/-0.89 years in the GH-deficient group compared to 0.23+/-1.07 years in their controls: in the GH non-deficient group the difference was -0.95+/-0.82 years compared to controls 0.16+/-1.06 years in their controls. Compared to chronological age, both bone and dental age were lower in the GH-deficient and GH non-deficient groups. It is concluded that children of short stature, both GH-deficient and GH non-deficient. exhibit a delayed dental age compared to their chronological age- and sex-matched controls. A multiple stepwise regression analysis showed that the sitting height and GH level were the only significant factors associated with dental maturity.

Age Determination by Skeleton↗
PubMed1996

Identification of single amino acid substitutions of Cys-736 that affect the steroid-binding affinity and specificity of the glucocorticoid receptor using phenotypic screening in yeast.

In this study a yeast-screening system has been developed for the isolation of rarely occurring change-of-function missense mutations in defined protein segments that have potential to give more information about the function of mutated residues. Mutagenesis of cysteine-736 was chosen for this initial study because it has been shown previously, by photoaffinity labeling, to lie in close proximity to the bound hormone molecule. After randomization of residue 736 by oligonucleotide-directed mutagenesis, two functional substitutions with serine (C736S) and threonine (C736T) were found. These were further analyzed using transactivation assays in both yeast and mammalian cells and by steroid-binding assays using wild type and mutant proteins expressed in mammalian cells. The C736S protein showed reduced sensitivity to all hormones tested in transactivation assays and a reduced affinity of hormone binding. A correspondence between sensitivity to hormones in transactivation assays and hormone-binding affinity was also observed for the C736T protein. However, in this case the sensitivity to the synthetic hormone triamcinolone acetonide was higher than that for wild type whereas the sensitivity to endogenous hormones was somewhat lower. To test the efficacy of the yeast-screening system in relation to the two informative mutations identified, all 20 alternative substitutions at position 736 were constructed and analyzed. In addition to Ser and Thr, which resulted in change of function, alanine was the only other substitution that resulted in significant activity. The activity of this mutant was indistinguishable from wild type in yeast. Thus we conclude that very conservative substitutions of cysteine-736 (C736A, C736S, and C736T) cause variable effects on hormone binding that distinguish between different glucocorticoid steroid hormones.

Amino Acids↗
PubMed1995

Modulation of DNA-binding specificity within the nuclear receptor family by substitutions at a single amino acid position.

Regulation of gene expression involves a large number of transcription factors with unique DNA-binding properties. Many transcription factors belong to families of related proteins that bind to similar but distinct sequences. In this study we have analyzed how amino acid substitutions at a single position in the DNA-binding domain modulate the DNA-binding specificity within the nuclear receptor family of transcription factors. All possible amino acids were introduced at the first position in the DNA recognition helix, and the specificities of the mutants were analyzed using response elements containing all combinations of bases at two variable base pair positions. All mutant proteins were functional in DNA binding, and could be divided into classes of mutants with different response element specificities. By combining functional data with analysis of the structural effects of the mutations by molecular modeling, we could identify both prohibitive steric interactions as well as positive interactions, such as hydrogen bonds, that function as important determinants for specificity. Only the residues found naturally in the glucocorticoid and estrogen receptors, glycine and glutamate, produce unique binding specificities. The specificities of the other mutants overlap with each other somewhat but the substitutions clearly have potential to contribute to diversity within the nuclear receptor family.

Amino Acid Sequence↗
PubMed1995

Interleukin-1 beta induces expression of cyclooxygenase-2 mRNA in human gingival fibroblasts.

The effect of interleukin-1 beta (IL-1 beta) on the expression of cyclooxygenase-1 and -2 (COX-1 and COX-2) mRNA and its relation to prostaglandin E2 (PGE2) biosynthesis in human gingival fibroblasts was studied. IL-1 beta increased levels of mRNA for COX-2 whereas the COX-1 mRNA level was unaffected. The increased COX-2 mRNA levels were accompanied by enhanced PGE2 formation. The phorbol, 12-myristate 13-acetate (PMA), known to stimulate protein kinase C (PKC), also induced expression of COX-2 mRNA. When gingival fibroblasts were treated simultaneously with IL-1 beta and PMA, the cytokine IL-1 beta synergistically increased levels of COX-2 mRNA, accompanied by a corresponding increase in PGE2 biosynthesis. The anti-inflammatory steroid, dexamethasone (DEX) abolished the enhanced expression of COX-2 mRNA as well as PGE2 formation induced by IL-1 beta, PMA or the combination of IL-1 beta and PMA. The study indicates that the IL-1 beta induced PGE2 formation is mediated by an enhanced gene expression of COX-2 in gingival fibroblasts suggesting that the enzyme COX-2 may play an important role in the regulation of prostanoid formation at inflammatory lesions in gingival tissue.

Base Sequence↗