Impaired male sexual development in perinatal Sprague-Dawley and Long-Evans hooded rats exposed in utero and lactationally to p,p'-DDE

Although the pesticide DDT has been banned in the United States for decades, it remains at low levels in the environment. p,p'-DDE, a metabolite of DDT, was recently shown to inhibit the binding of androgens to the androgen receptor and to exert antiandrogenic effects in perinatal Long-Evans (LE) rats at a dose of 100 mg/kg/day administered to pregnant dams. In this study, we compared the effects of p,p'-DDE on male sexual development in offspring of Sprague-Dawley (SD) and LE rats. The chemical was dosed by gavage to pregnant dams at 10 or 100 mg/kg body wt from gestation day 14 to 18. The developing male rats were examined for sexual developmental landmarks, while the effects of p,p'-DDE on androgen receptor expression were evaluated in the testis and other reproductive organs. The tissue dosimetry of p,p'-DDE was also determined at different stages of development following in utero and lactational exposures. The higher p,p'-DDE dose induced a reduction in the male anogenital distance, an increase in retention of male thoracic nipples and alterations in expression of the androgen receptor in either one or both strains. A much weaker response was seen in the lower dose groups. Tissue and body fluid concentrations of p,p'-DDE were similar in the two strains in some tissues but dissimilar in others, particularly in the serum levels. Higher serum p,p'-DDE levels in the LE strain during pregnancy corresponded with an overall greater sensitivity of the LE strain to the antiandrogenic effects of p,p'-DDE. These results support the previous findings of p,p'-DDE antiandrogenicity in LE rats, extend the findings to SD rats, and suggest that the developmental effects of p,p'-DDE on male rat sexual differentiation are minimal at maternal doses below 10 mg/kg/day.

Methyl tertiary butyl ether-induced endocrine alterations in mice are not mediated through the estrogen receptor

Chronic exposure to methyl tertiary butyl ether (MTBE) altered the rodent tumor incidence of endocrine-sensitive tissues and decreased the incidence of estrogen-dependent uterine cystic hyperplasia in mice. To test the hypothesis that changes in the incidence of tumors in female B6C3F1 mice after MTBE exposure are secondary to endocrine alterations, we exposed female mice to the carcinogenic dose of MTBE vapor (8000 ppm) for 3 or 21 days or 4 or 8 months under conditions similar to a previous 2-year bioassay. MTBE exposure significantly decreased body weight gain and ovary and pituitary weight at 4 and 8 months and uterine weight at all time points. After 8 months of exposure, MTBE significantly increased the length of the estrous cycle by increasing the mean number of days in both the estrus and the nonestrus stages. Histological evaluation of H&E-stained tissues showed a decrease in the number of uterine glands after subchronic MTBE exposure. DNA synthesis, as measured by the incorporation of 5-bromo-2'-deoxyuridine (BrdU), was decreased in uterine glandular and luminal epithelial cells after MTBE exposure for 3 or 21 days or 4 or 8 months. MTBE exposure decreased the number of epithelial layers in the cervix and vagina at all time points. DNA synthesis was decreased in cervical and vaginal epithelium after 21 days of MTBE. Decreased zona reticularis of adrenal glands was found after 4 and 8 months of MTBE exposure without changes in BrdU incorporation. MTBE did not competitively bind to estrogen receptor. MTBE exposure did not alter serum estrogen levels or alter the location or intensity of estrogen receptor immunoreactivity in the uterus, cervix, and vagina. These data indicate that while MTBE exposure causes multiple endocrine-related tissue and cellular responses, these effects are not mediated through the estrogen receptor.

Expression and subcellular distribution of the beta-isoform of the human glucocorticoid receptor

Alternative splicing of the human glucocorticoid receptor (hGR) primary transcript produces two highly homologous protein isoforms, termed hGR alpha and hGRbeta, that differ at their carboxy-termini. In contrast to the well characterized hGR alpha isoform, which modulates gene expression in a hormone-dependent fashion, the biological significance of hGRbeta has only recently begun to emerge. We and others have shown that the hGRbeta messenger RNA transcript is widely expressed in human tissues and that the hGRbeta protein functions as a dominant negative inhibitor of hGR alpha in transfected cells. Unfortunately, these initial studies did not determine whether the hGRbeta protein was made in vivo. Such analyses are hindered because available anti-hGR antibodies cannot discriminate between the similarly sized hGR alpha and hGRbeta proteins. Therefore, to investigate the expression of the hGRbeta protein, we have produced an antipeptide, hGRbeta-specific antibody termed BShGR. This antibody was made against the unique 15-amino acid peptide at the carboxy-terminus of hGRbeta and recognizes both the native and denatured conformations of hGRbeta, but does not cross-react with hGR alpha. Using BShGR on Western blots and in immunoprecipitation experiments, we detected the hGRbeta protein in a variety of human cell lines and tissues. Immunocytochemistry was then performed with BShGR on HeLa S3 and CEM-C7 cells and on tissue sections prepared from lung, thymus, and liver to assess the cellular and subcellular distribution of hGRbeta. In all immunopositive cells, hGRbeta was found in the nucleus independent of glucocorticoid treatment. Within tissues, the hGRbeta protein was expressed most abundantly in the epithelial cells lining the terminal bronchiole of the lung, forming the outer layer of Hassall's corpuscle in the thymus, and lining the bile duct in the liver. As a potential in vivo inhibitor of hGR alpha activity, expression of hGRbeta may be an important factor regulating target cell responsiveness to glucocorticoids.

Mouse glucocorticoid receptor phosphorylation status influences multiple functions of the receptor protein

Although studies have shown that the mouse glucocorticoid receptor (mGR) contains eight phosphorylation sites (Bodwell, J. E., Ortí, E. , Coull, J. M., Pappin, D. J. C., Smith, L. I., and Swift, F. (1991) J. Biol. Chem. 266, 7549-7555), the effect of phosphorylation on receptor function is unclear. We have examined the consequences of single or multiple phosphorylation site mutations on several properties of mGR including receptor expression, ligand-dependent nuclear translocation, hormone-mediated transactivation, ligand-dependent down-regulation of mGR, and receptor protein half-life. Mutations had little effect on receptor expression, subcellular distribution, ligand-dependent nuclear translocation, or on the ability to activate hormone-mediated transcription from a complex (murine mammary tumor virus) promoter. In contrast, the phosphorylation status of the mGR had a profound effect on the ability to transactivate a minimal promoter containing simple glucocorticoid response elements after hormone administration. Similarly, ligand-dependent down-regulation by glucocorticoids of both receptor mRNA and protein was abrogated in mutants containing three or more phosphorylation site alterations. Finally, we show that the phosphorylation status of mGR has a profound effect on the stability of the glucocorticoid receptor protein. Receptors containing seven or eight mutated sites have a markedly extended half-life and do not show the ligand-dependent destabilization seen with wild type receptor. These data show that receptor phosphorylation may play a crucial role in regulating receptor levels and hence control receptor functions.

Dehydroepiandrosterone activates mutant androgen receptors expressed in the androgen-dependent human prostate cancer xenograft CWR22 and LNCaP cells

An androgen receptor (AR) gene mutation identified in the androgen-dependent human prostate cancer xenograft, CWR22, changed codon 874 in the ligand-binding domain (exon H) from CAT for histidine to TAT for tyrosine and abolished a restriction site for the endonuclease SfaNI. SfaNI digestion of AR exon H DNA from normal but not from prostate cancer tissue indicated H874Y is a somatic mutation that occurred before the initial tumor transplant. CWR22, an epithelial cell tumor, expresses a 9.6-kb AR mRNA similar in size to the AR mRNA in human benign prostatic hyperplasia. AR protein is present in cell nuclei by immunostaining as in other androgen-responsive tissues. Transcriptional activity of recombinant H874Y transiently expressed in CV1 cells in the presence of testosterone or dihydrotestosterone was similar to that of wild type AR. With dihydrotestosterone at a near physiological concentration (0.01 nM), H874Y and wild type AR induced 2-fold greater luciferase activity than did the LNCaP mutant AR T877A. The adrenal androgen, dehydroepiandrosterone (10 and 100 nM) with H874Y stimulated a 3- to 8-fold greater response than with wild type AR and at 100 nM the response was similar with the LNCaP mutant. H874Y, like the LNCaP cell mutant, was more responsive to estradiol and progesterone than was wild type AR. The antiandrogen hydroxyflutamide (10 nM) had greater agonist activity (4- to 7-fold) with both mutant ARs than with wild type AR. AR mutations that alter ligand specificity may influence tumor progression subsequent to androgen withdrawal by making the AR more responsive to adrenal androgens or antiandrogens.

Androgen and glucocorticoid receptors in the stroma and epithelium of prostatic hyperplasia and carcinoma

Differences in stromal and epithelial cell staining for androgen and glucocorticoid receptors (ARs and GRs) were investigated in 20 patients with clinically localized prostatic carcinoma treated by radical prostatectomy. Sections of benign prostatic hyperplasia and prostatic carcinoma from each patient were stained with antibodies to AR and GR using an avidin-biotin peroxidase technique. The specificity of the GR immunoreactivity was established in benign prostatic hyperplasia and prostatic carcinoma by immunohistochemistry using the GR antibody absorbed with synthetic peptide and Western blotting. Nuclear staining intensity and percentage of nuclei stained were summed to obtain AR and GR immunostaining scores. AR staining of prostatic carcinoma epithelial [103 +/- 58 (SD)] and stromal (126 +/- 48) nuclei was less than in benign prostatic hyperplasia (142 +/- 47 and 169 +/- 56; paired Student's t tests, P = 0.02 and P = 0.01); however, no difference in staining intensity occurred between stroma and epithelium in either tissue type. GR stained intensely in stromal cells from benign prostatic hyperplasia (189 +/- 50) and prostatic carcinoma (163 +/- 60). However, prostatic carcinoma epithelial cells (34 +/- 57) had low levels of glucocorticoid receptor staining (P < 10(-7)), and benign prostatic hyperplasia epithelium (74 +/- 51) was intermediate. In most patients, GR could not be detected in nuclei of prostatic carcinoma epithelial cells but was undiminished in stromal cell nuclei. There was no relationship by multivariate regression analysis between AR or GR staining and age, serum prostate-specific antigen, Gleason grade, or pathological stage. In comparison with AR, the greater variability of GR staining in epithelium versus stroma of prostatic carcinoma warrants further study of GR, particularly in the area of stromal-epithelial interaction.

The human glucocorticoid receptor beta isoform. Expression, biochemical properties, and putative function

Alternative splicing of the human glucocorticoid receptor (hGR) primary transcript produces two receptor isoforms, hGRalpha and hGRbeta, which differ at their carboxyl termini. The hGRalpha isoform conveys endocrine information to target tissues by altering patterns of gene expression in a hormone-dependent fashion. In contrast to hGRalpha, very little is known about the hGRbeta splice variant. Using hGRalpha- and hGRbeta-specific riboprobes on human multiple tissue Northern blots, we show that the hGRbeta message has a widespread tissue distribution. We also prove by reverse transcriptase-polymerase chain reaction that the alternative splicing event underlying the formation of the hGRbeta message occurs in these tissues. Because the hGRbeta protein differs from hGRalpha at the extreme COOH terminus, we investigated several of the biochemical properties of hGRbeta expressed in transfected cells. hGRbeta does not bind the glucocorticoid agonist dexamethasone nor the glucocorticoid antagonist RU38486 in vivo. Moreover, in contrast to hGRalpha, hGRbeta is located primarily in the nucleus of transfected cells independent of hormone administration. Finally, in the absence of hGRalpha, hGRbeta is transcriptionally inactive on a glucocorticoid-responsive enhancer. However, when both isoforms are expressed in the same cell, hGRbeta inhibits the hormone-induced, hGRalpha-mediated stimulation of gene expression. Thus, hGRbeta potentially functions as a dominant negative inhibitor of hGRalpha activity.

Coordinate modulation of glucocorticoid receptor and glutaminase gene expression in LLC-PK1-F+ cells

The effect of glucocorticoid receptor on glutaminase gene expression and related glutamine metabolism was studied in proximal tubule-like LCC-PK1-F+ cells. These cells express functional glucocorticoid receptors as demonstrated by immunoreactivity with antiglucocorticoid receptor antibody, specific ligand binding, and a 14-fold increase in chloramphenicol acetyltransferase (CAT) reporter gene activity after exposure to dexamethasone (10(-6)M). Dexamethasone exposure for 18 h increased glutaminase mRNA and activity by 32 and 42%, respectively (both P< 0.05, paired t-test), associated with a small (9%) but significant increase in glutamine utilization (P<0.05). In an effort to elicit a greater response, endogenous glucocorticoid receptors were supplemented by transfecting cells with a plasmid, pMAMGR, expressing the rat glucocorticoid receptor gene. Transfected cells expressed a 39-fold increase in CAT activity with dexamethasone treatment, confirming a higher level of functional receptors, but glutaminase mRNA and activity were now decreased by 34 and 32%, respectively, associated with a 15% fall in glutamine utilization after 18-h exposure to dexamethasone. This biphasic response in glutaminase gene expression was mirrored by glucocorticoid receptor mRNA that increased 41% after dexamethasone in LLC-PK(1)-F+ cells, but decreased 63% after transfection (both P<0.05). These findings are consonant with glucocorticoid receptor gene modulation of glutaminase gene expression and glutamine utilization.

Immunocytochemical analysis of hormone mediated nuclear translocation of wild type and mutant glucocorticoid receptors

We have analyzed structural and functional features of the human glucocorticoid receptor (hGR) for their effects on receptor subcellular distribution. COS 1 cells transiently transfected with wild type and mutant hGR cDNAs were assessed immunocytochemically using well-characterized antipeptide antibodies to the hGR. The effect of administration of steroid hormones (and the antiglucocorticoid RU486) on receptor localization was evaluated. Unliganded wild type receptors expressed in COS 1 cells were predominately cytoplasmic. Addition of glucocorticoids or the glucocorticoid receptor antagonist, RU486, resulted in complete translocation of these receptors into the nucleus whereas non-glucocorticoid steroids or dibutyryl cAMP were not effective in promoting nuclear translocation. Thus, nuclear translocation was specific for steroids capable of high affinity binding to the hGR. To elucidate the potential role of receptor domains in receptor localization, COS 1 cells transiently transfected with various receptor cDNA mutants were analyzed in a similar manner. Translocation of an hGR deletion mutant lacking the majority of the amino terminus (deletion of amino acids 77-262) was identical to the wild type receptor despite the absence of a transactivation domain. Receptors in which the DNA binding domain was either partially or totally deleted showed an impaired capacity to undergo hormone-inducible nuclear translocation. Deletion of the hinge region of the hGR (which also contains part of the nuclear localization signal, NL1) resulted in receptor localization in the cytoplasm. Mutants in the ligand binding domain exhibited two localization phenotypes, exclusively nuclear or cytoplasmic. Receptor mutants truncated after amino acid 550 were found in the nucleus in the presence and absence of hormone consistent with the existence of nuclear localization inhibitory sequences in the ligand binding domain of the receptor. However, a linker insertion mutant (at amino acid 582) which results in a receptor deficient in ligand binding did not undergo nuclear translocation indicating that nuclear localization inhibitory sequences were intact in this mutant. The role of receptor phosphorylation on hormone induced nuclear translocation was also examined. Mouse glucocorticoid receptors which contained mutations of certain hormone inducible phosphorylation sites exhibited translocation properties similar to wild type mGR indicating that these phosphorylation sites on the receptor do not play a major role in hormone inducible nuclear translocation.

Steroid hormone receptors in astrocytic neoplasms

The presence of specific steroid hormone-binding receptors has been correlated with the clinical response to hormonal therapy in a number of different neoplasias, including breast and prostate cancer. In this article, we investigated the expression of the androgen, estrogen, glucocorticoid, and progesterone receptor messenger ribonucleic acid (mRNA) and protein in a number of astrocytic neoplasms of various histological grades. Androgen and glucocorticoid receptor mRNA were detected in all astrocytic neoplasms examined, regardless of histological subtype. In contrast, progesterone receptor mRNA was observed more frequently in high-grade tumors than in low-grade tumors. Estrogen receptor mRNA was undetectable in all astrocytic tumors examined. These studies suggest a possible adjunct clinical use of hormonal therapy for the treatment of astrocytomas. Specific antagonists and agonists may allow the modulation of the growth of these tumors. Development of this body of knowledge may lead to the development of better treatment for these aggressive tumors.

Androgen receptor antagonist versus agonist activities of the fungicide vinclozolin relative to hydroxyflutamide

The mechanism of antiandrogenic activity of vinclozolin (3-(3,5-dichlorophenyl)-5-methyl-5-vinyloxazolidine-2,4-dione), a dicarboximide fungicide under investigation for its potential adverse effects on human male reproduction, was investigated using recombinant human androgen receptor (AR). The two primary metabolites of vinclozolin in plants and mammals are M1 (2-[[3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid) and M2 (3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide). Both metabolites, in a dose-dependent manner, target AR to the nucleus and inhibit androgen-induced transactivation mediated by the mouse mammary tumor virus promoter. M2 is a 50-fold more potent inhibitor than M1 and only 2-fold less than hydroxyflutamide. In the presence of dihydrotestosterone (50 nM), M2 (0.2-10 microM) inhibits androgen-induced AR binding to androgen response element DNA. In the absence of dihydrotestosterone, concentrations of 10 microM M2 or hydroxyflutamide promote AR binding to androgen response element DNA and activation of transcription. Agonist activities of M2 and hydroxyflutamide occur at 10-fold lower concentrations with the mutant AR (Thr877 to Ala) endogenous to LNCaP human prostate cancer cells. The results indicate that androgen antagonists can act as agonists, depending on ligand binding affinity, concentration, and the presence of competing natural ligands.

Androgen receptor expression in meningiomas

The predominance of meningiomas in females, the accelerated growth of these tumors during the luteal phase of the menstrual cycle and during pregnancy, and the association between meningiomas and breast cancer have led to a number of studies examining the potential role of steroids in the growth of meningiomas. The possibility that androgens play a role in meningioma proliferation has been suggested by a small number of investigators. The aim of this study was to examine the expression of androgen receptor messenger ribonucleic acid (mRNA) and correlate it using immunochemistry with the nuclear localization of androgen receptor in a large number of meningiomas. Thirty-nine meningiomas were examined by Northern blot analysis for the presence of measurable amounts of androgen receptor mRNA and eight of these were analyzed by immunohistochemistry for receptor protein. Sixty-seven percent of the meningiomas expressed androgen receptor mRNA. There was a marked predominance of women among the patients whose tumors expressed androgen receptor; 69% were women and 31% were men. The immunohistochemical data correlated with Northern blot analysis of mRNA. The staining was predominantly nuclear, suggesting that the androgen receptor resides in a location that can activate gene expression.

Intragenic sequences of the human glucocorticoid receptor complementary DNA mediate hormone-inducible receptor messenger RNA down-regulation through multiple mechanisms

Glucocorticoid receptors (GR) are ligand-dependent transcription factors that play a critical role in the endocrine control of cell growth, differentiation, and death. These steroid receptors are widely recognized to undergo down-regulation after exposure to ligand in cell cultures and animals, including humans. This reduction in cellular receptor levels leads to insensitivity to subsequent hormone administration. The mechanisms controlling homologous down-regulation of the GR are, however, poorly understood. We have previously shown (1) that a transfected human GR (hGR) complementary DNA (cDNA) contains sequences that are sufficient to recapitulate the down-regulation of both hGR messenger RNA (mRNA) and protein seen in vivo. We have now evaluated potential mechanisms involved in the hormonal regulation of the hGR mRNA and, further, have identified an intragenic domain of the hGR cDNA that contains the down-regulatory signal. Glucocorticoid treatment of COS-1 cells expressing a transfected hGR cDNA resulted in down-regulation of the hGR mRNA in the presence of cycloheximide or actinomycin-D, suggesting that a glucocorticoid-inducible protein was not essential for down-regulation. We show that prolonged receptor occupation by ligand leads to increased GR mRNA turnover, and furthermore, that either the agonist dexamethasone or the antagonist RU486 decreased transcription of the hGR cDNA. To resolve which receptor cDNA sequences are critical in down-regulation, a cotransfection strategy was employed in which a series of hGR cDNA deletion mutants was transfected in conjunction with the full-length hGR cDNA. The effects of glucocorticoid on the regulation of receptor mRNAs encoded by the mutant receptor cDNAs were examined. Deletions within the 5' half of the receptor cDNA produced transcripts that were susceptible to glucocorticoid-mediated down-regulation, whereas deletion of sequences located in the 3'-end of the receptor-coding sequence (corresponding to amino acids 550-697) resulted in receptor transcripts that were only minimally down-regulated by glucocorticoid. Together these studies indicate that multiple mechanisms control GR mRNA abundance, and an intragenic element within the ligand-binding domain is critical for this down-regulation.

Regulation of the human glucocorticoid receptor by long-term and chronic treatment with glucocorticoid

HeLa S3 cells that contain endogenous glucocorticoid receptors (GR) were treated with dexamethasone (DEX) for periods of time ranging from 24 h to 2 weeks or chronically over a 2-year period. Regulation of GR protein and mRNA were examined by affinity labeling, Western blotting, and Northern blotting. Relatively short-term treatment of cells with DEX for 24 or 48 h revealed more profound down-regulation of GR protein than of GR mRNA. However, by 2 weeks of DEX treatment, the levels of both receptor protein and mRNA were both maximally down-regulated. Cells that had been chronically DEX treated (for up to 2 years) had no measurable GR protein or mRNA. The down-regulation of receptor protein and RNA that occurred after 2 weeks of DEX treatment is completely reversible upon DEX removal, whereas reversibility did not occur with cells that had been chronically treated with DEX. Furthermore, transfection of a glucocorticoid responsive reporter plasmid into these chronically DEX-treated cells demonstrated that these cells were no longer responsive to steroid treatment. However, cotransfection of a plasmid encoding the human GR into these chronically DEX-treated cells resulted in restored production of GR and responsiveness to hormone, indicating that the defect in these cells occurs only at the receptor level.

A ligand-dependent bipartite nuclear targeting signal in the human androgen receptor. Requirement for the DNA-binding domain and modulation by NH2-terminal and carboxyl-terminal sequences

The amino acid sequence requirements for androgen-dependent androgen receptor nuclear import were determined by immunostaining transiently expressed full-length wild type and mutant human androgen receptors (AR) in monkey kidney COS cells and measuring transcriptional activity by cotransfection with a luciferase reporter vector in monkey kidney CV1 cells. Mutagenesis studies revealed a bipartite nuclear targeting sequence in the DNA binding and hinge regions at amino acids 617-633, consisting of two clusters of basic amino acids separated by 10 amino acids, (sequence: see text). In a series of deletion mutants, AR NH2-terminal fragments (residues 1-639 through 1-723) displayed constitutive nuclear import, and transcriptional activity was similar to that of the ligand-activated full-length wild type AR. In contrast, nuclear import and transcriptional activation were inhibited by sequence extensions into the steroid-binding domain (1-771). Constitutive nuclear import was regained in part by NH2-terminal deletions of full-length AR. Expression of AR/pyruvate kinase chimeras defined a sequence required for pre-dominant nuclear localization as residues 580-661, comprised of the second zinc finger region of the DNA-binding domain, the 17-amino-acid putative targeting sequence, and 28 residues of flanking carboxyl-terminal sequence. These studies suggest that the bipartite nuclear targeting sequence of AR includes flanking sequence and is modulated by interactions between the NH2-and carboxyl-terminal regions.

Characterization of mutant androgen receptors causing partial androgen insensitivity syndrome

The androgen insensitivity syndrome (AIS) is an X-linked disorder caused by mutations of the androgen receptor (AR) gene resulting in a spectrum of sex phenotypes that ranges from complete female (complete AIS) to nearly complete male (partial AIS). Using the polymerase chain reaction and denaturing gradient gel electrophoresis, we have analyzed the AR gene in three 46,XY individuals with partial AIS. In one subject whose androgen insensitivity was manifest at birth by clitoromegaly, posterior labial fusion, and a urogenital sinus, androgen-binding affinity in genital skin fibroblasts was similar to that of the control. In this subject, a mutation was identified in exon C encoding the second zinc finger of the androgen receptor. The mutation converted a leucine residue at position 616 to arginine, causing greatly reduced binding of receptor to an androgen-response element DNA sequence. However, the mutant AR retained a low level of transcriptional activity at physiological androgen concentrations in keeping with the subject's phenotype of partial AIS. In the second subject, who also had an ambiguous external genital phenotype, a single base mutation was identified in exon G, converting arginine at position 840 to histidine. Androgen-binding affinity in genital skin fibroblasts of this subject was 7-fold lower than control, and the mutant receptor had reduced transcriptional activity. In the third subject, who had a female phenotype with normal pubic hair reflecting a low degree of androgen responsiveness, the valine residue at position 889 was replaced by methionine. This mutant receptor had apparent normal androgen-binding affinity but reduced androgen-binding capacity when examined by expression of the recreated mutant AR in COS 7 cells. These results demonstrate the clinical, functional, and molecular heterogeneity in the syndrome of partial androgen insensitivity.

Extended junctional sarcoplasmic reticulum of avian cardiac muscle contains functional ryanodine receptors

The ryanodine receptor (RYR)/Ca2+ release channel of avian cardiac muscle was localized by immunocytochemical techniques and biochemically characterized using isolated membrane and receptor protein fractions. Monoclonal antibody C3-33 raised against the canine cardiac RYR bound to the junctional sarcoplasmic reticulum of pigeon and finch hearts, both at peripheral couplings and at extended junctional sarcoplasmic reticulum (EJSR). Immunoblots of sarcoplasmic reticulum vesicles from pigeon and finch hearts showed this antibody recognized a single high molecular weight protein, which co-migrated with the canine M(r) 565,000 RYR/Ca2+ release channel polypeptide. The pigeon heart RYR bound [3H]ryanodine with high affinity in a Ca(2+)-dependent manner, comparable to the canine cardiac RYR. Purification of the pigeon RYR yielded a 30 S protein complex, which bound the maximum calculated amount of [3H]ryanodine ((440 +/- 60) pmol/mg protein), assuming one high affinity site/tetrameric 30 S RYR comprised of M(r) 565,000 polypeptides. Autoradiography of isolated finch cardiac myocytes indicated [3H]ryanodine binding throughout the cells. These results suggest that avian heart contains a single population of RYRs, and thereby support the hypothesis that avian EJSR contains functional calcium release channels which, because of the absence of transverse tubules, can be located micrometers away from the surface membrane in avian heart.

Steroid requirement for androgen receptor dimerization and DNA binding. Modulation by intramolecular interactions between the NH2-terminal and steroid-binding domains

Infection of Spodoptera frugiperda Sf9 insect cells with recombinant human androgen receptor (AR) baculovirus results in expression of a 118-kDa phosphoprotein that displays high affinity androgen binding and androgen-dependent targeting to the nucleus. Using the DNA mobility shift assay, specific in vitro binding of full-length AR to androgen response element DNA (ARE) requires intracellular hormone exposure. The ability of a variety of steroids to induce ARE binding paralleled their transcriptional potential. Certain antihormones, cyproterone acetate and RU486, promote ARE binding, but a pure antiandrogen, hydroxyflutamide, inhibits AR binding to ARE DNA. AR dimerization requires incubation of recombinant baculovirus-infected insect cells with androgen, but only when one or both components of the dimer contain the NH2-terminal domain. Based on the intensities of ARE binding and lack of binding to an ARE half-site, it appears that, unlike the glucocorticoid receptor, AR binds DNA primarily as a dimer. Thus, full-length baculovirus-expressed AR requires intracellular hormone exposure for dimerization and ARE binding to overcome inhibition imposed by the AR NH2-terminal domain. Antihormones with agonist activity promote dimerization and ARE binding, while a pure antiandrogen blocks AR DNA binding. It is concluded that intramolecular interactions between the NH2-terminal and steroid-binding domains are regulated by the specificity of hormone binding and modulate receptor dimerization and DNA binding.

Progestagen nuclear binding sites in the male genital tract of the mouse, studied by autoradiography

Autoradiograms were prepared after injection of 125I progestagen (sp. act. 2200 Ci/mmol) to prepubertal and young adult mice. Nuclear concentration of radioactivity was found in smooth muscle cells at the beginning and the end of the deferent duct and in fibroblasts around the fusion of the deferent duct with the urethra. Nuclear labeling was enhanced in adult animals pretreated with oestradiol-valerate. In prepubertal mice nuclear labeling was more abundant than in adult mice and found in all smooth muscle cells of the deferent duct. No nuclear labeling was observed in other accessory sex organs. Nuclear labeling was prevented by injection of excess of unlabeled R5020. The presence of progestin receptors in smooth muscle cells of the deferent duct suggests a regulatory effect of progestin on contractions in analogy to progestin effects on oviductal and uteral smooth muscle cells. The presence of nuclear progestin receptors in the periurethral region may indicate an involvement of progestins in the etiology and regulation of benign prostate hyperplasia.

Dexamethasone target sites in the central nervous system and their potential relevance to mental illness

1. The topical distribution of tritiated dexamethasone (DEX), a potent synthetic glucocorticoid of widespread use in the diagnosis and assessment of mental illness, was studied in rat CNS by autoradiography to obtain information on potential target sites for feedback and other centrally mediated effects of glucocorticoids. 2. The cells of the arcuate nucleus of the hypothalamus and the lateral thalamic nuclei displayed the most concentrated nuclear accumulation of silver grains. 3. Significant accumulation, exceeding that found in the hippocampal formation, also occurred in the cells of the ventromedial, periventricular, and paraventricular nuclei of the hypothalamus, the locus ceruleus, the nucleus tractus solitarii, and the area postrema, none of which are targeted by corticosterone, the native glucocorticoid of the rat. 4. Nuclear accumulation of silver grains was prominent in neural and glial cells of the cerebral cortex, the olfactory nucleus, the dorsolateral septum, the amygdala, the subfornical organ, the lateral parabrachial, medial trapezoid, and dorsal reticular nuclei, the nucleus centralis of the raphe, the cerebellum, and vascular tissues. 5. The localization of DEX in hypothalamic and brain-stem nuclei coincided with that of the glucocorticoid receptor, possibly implicating these sites in direct or modulating effects of glucocorticoids in various forms of mental disturbance, including depression, anxiety, panic disorders, and alcohol withdrawal. 6. The extent to which various CNS regions targeted by DEX feature in negative feedback control of adrenocortical secretion remains to be defined, as does the site of impaired feedback disclosed by the dexamethasone suppression test in psychiatric patients.

Immunohistochemistry of the androgen receptor in human benign and malignant prostate tissue

The role of the androgen receptor in the development and progression of prostatic carcinoma has not been defined. The development of androgen receptor antibodies has provided new opportunities for direct immunohistochemical analysis. We compared the androgen receptor staining characteristics of fresh human prostatic carcinoma with benign prostatic hyperplasia (BPH) using an avidin-biotin complex method. Cancer and BPH obtained from the same radical retropubic prostatectomy specimen in 10 prostate cancer patients (68.5 +/- 7.3 years old standard deviation) and BPH from 10 noncancer patients (71.5 +/- 7.7 years old) were incubated with AR52, a rabbit polyclonal antibody against a synthetic androgen receptor peptide. Nuclei within each section were graded for intensity of androgen receptor staining (0-absent, 1-weak, 2-moderate or 3-strong) and the percentage (0 to 100%) of nuclei sampled staining at each of these intensity levels was determined. A total intensity score (0 to 300) was the summation of the products of each intensity score (0 to 3) and their corresponding percentages. Cancer sections (166 +/- 69) stained less intensely and more heterogeneously than BPH in cancer patients (246 +/- 41, Student's t test p < 0.05) and noncancer patients (225 +/- 39, p < 0.05). The decreased intensity and greater heterogeneity of androgen receptor staining in cancer tissue may implicate a quantitative or functional difference in androgen receptor between prostatic carcinoma and BPH.

Ligand-dependent down-regulation of stably transfected human glucocorticoid receptors is associated with the loss of functional glucocorticoid responsiveness

The effect of glucocorticoids on the regulation of stably transfected human glucocorticoid receptors has been examined. Exposure of a Chinese hamster ovary-derived cell line containing stably transfected human glucocorticoid receptor genes and glucocorticoid-responsive dihydrofolate reductase genes to 5 nM dexamethasone resulted in a rapid, time-dependent reduction in the level of glucocorticoid receptor protein to 50% of control levels within 5 h of steroid treatment. This decrease in receptor protein was persistent, with a maximal 70% reduction observed even after 4 weeks of dexamethasone treatment. Immunocytochemical analysis of the influence of dexamethasone on stably transfected glucocorticoid receptors revealed efficient translocation of receptors to the nucleus within 1 h of hormone treatment. However, upon longer exposure to dexamethasone (5 h), immunoreactive glucocorticoid receptors were localized primarily to the cytoplasm. By 24 h of treatment, glucocorticoid receptors were absent from the cytoplasm and the nucleus, suggesting that the ligand-induced loss of glucocorticoid receptors may be a cytoplasmic event. The decrease in transfected glucocorticoid receptor protein was largely reflected by similar changes in steady state levels of human glucocorticoid receptor mRNA; however, the effects of hormone on receptor protein levels were more profound than on receptor mRNA. There was an initial rapid reduction in transfected glucocorticoid receptor mRNA to 50% of control levels within 2 h of dexamethasone treatment. This reduction was followed by a transient rise in mRNA expression after 12 h of hormone treatment. With prolonged exposure to dexamethasone (> 12 h) a second, more gradual decline in human glucocorticoid receptor mRNA was observed. This biphasic pattern of glucocorticoid receptor gene expression was not reflected at the level of receptor protein, suggesting that both transcriptional and translational control mechanisms may be involved in ligand-dependent receptor regulation. When cells were removed from dexamethasone after up to 48 h of treatment, glucocorticoid receptor mRNA levels fully recovered within 12 h. Receptor protein recovered only partially during this same time period. Down-regulation of glucocorticoid receptor protein and mRNA levels by dexamethasone in stably transfected cells led to corresponding reductions in the hormone sensitivity to two glucocorticoid-regulated genes: a transiently transfected chloramphenicol acetyltransferase receptor gene and a stably integrated dihydrofolate reductase gene. These results demonstrate that stably transfected human glucocorticoid receptors are subject to ligand-induced down-regulation in a heterologous cell line. Moreover, glucocorticoid receptor autoregulation appears to be a highly conserved mechanism for attenuating cellular responsiveness to hormone.