DNA dependent recruitment of DDX17 and other interacting proteins by the human androgen receptor.

An oligonucleotide-based assay (OBA) was used to identify novel co-factors that can be recruited by the deoxyribonucleic acid (DNA)-bound androgen receptor (AR). Nuclear extracts obtained from LNCaP cells, after incubation with R1881, were incubated with biotinylated oligonucleotides bound to streptavidin coated beads. The oligonucleotides contain 3 copies in tandem of the androgen responsive element ARE1 from the prostate specific antigen (PSA) gene promoter. As control incubation, a scrambled version of the tandem ARE1 was used. Immunoblots of the eluents revealed that the AR was bound to the ARE1 oligonucleotide and to a much lesser extent to the scrambled oligonucleotide. Proteins eluted from the oligonucleotides, were separated on a 5-15% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gradient gel, followed by identification using mass spectrometry. Identified proteins were scored for having one or more of the following known properties: nuclear localization, involved in transcription regulation, involvement in steroid hormone receptor (SHR) function, or specifical involvement in AR function. A total number of 85 nuclear proteins were found in two separate OBAs. Based on peptide counting, we found enrichment of 7 proteins eluted from the ARE1 oligonucleotide, compared to the scrambled oligonucleotide. Taken together with the obtained scores, these proteins are considered putative AR co-factors. One of these proteins, DDX17, is known to be a co-factor for estrogen receptor alpha (ERalpha), but has never been associated with AR function. The results indicate that the ARE oligonucleotide-based assay may allow enrichment of new candidate DNA-bound AR interacting proteins.

Proteomic analysis of proteins regulated by TRPS1 transcription factor in DU145 prostate cancer cells.

The aim of the present study was to identify proteins differentially regulated by TRPS1 in human prostate cancer cells in order to better understand the role of TRPS1 in prostate cancer development. The proteomes of androgen-independent DU145 prostate cancer cells, that do not express TRPS1 and of genetically engineered DU145 cells that stable and inducible express recombinant TRPS1 protein, were compared. Using two-dimensional electrophoresis followed by mass spectrometric analysis, 13 proteins that were differentially expressed between these two cell lines were identified. These proteins represent a dominant reduction of expression of antioxidant proteins, including superoxide dismutase, protein disulfide isomerase A3 precursor, endoplasmin precursor and annexin A2. Furthermore, regulation was observed for mitochondrion-associated proteins, glycolytic enzymes, a cytoskeleton-associated protein, a nuclear protein and proteins involved in apoptosis. Our data indicate that overexpression of TRPS1 protein is correlated with reduced protein expression of certain antioxidants. This suggests a possible involvement of TRPS1 in oxidative stress, and possibly in apoptosis in androgen-independent DU145 prostate cancer cells.

A novel mutation F826L in the human androgen receptor in partial androgen insensitivity syndrome; increased NH2-/COOH-terminal domain interaction and TIF2 co-activation.

A novel mutation F826L located within the ligand binding domain (LBD) of the human androgen receptor (AR) was investigated. This mutation was found in a boy with severe penoscrotal hypospadias (classified as 46,XY DSD). The AR mutant F826L appeared to be indistinguishable from the wild-type AR, with respect to ligand binding affinity, transcriptional activation of MMTV-luciferase and ARE2-TATA-luciferase reporter genes, protein level in genital skin fibroblasts (GSFs), and sub-cellular distribution in transfected cells. However, an at least two-fold higher NH2-/COOH-terminal domain interaction was found in luciferase and GST pull-down assays. A two-fold increase was also observed for TIF2 (transcription intermediary factor 2) co-activation of the AR F826L COOH-terminal domain. This increase could not be explained by a higher stability of the mutant protein, which was within wild-type range. Repression of transactivation by the nuclear receptor co-repressor (N-CoR) was not affected by the AR F826L mutation. The observed properties of AR F826L would be in agreement with an increased activity rather than with a partial defective AR transcriptional activation. It is concluded that the penoscrotal hypospadias in the present case is caused by an as yet unknown mechanism, which still may involve the mutant AR.

Lack of Association of the 11beta-hydroxysteroid dehydrogenase type 1 gene 83,557insA and hexose-6-phosphate dehydrogenase gene R453Q polymorphisms with body composition, adrenal androgen production, blood pressure, glucose metabolism, and dementia.

CONTEXT: Recently, it was proposed that a combination of the 83,557insA polymorphism in the 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1) gene and the R453Q polymorphism in the hexose-6-phosphate dehydrogenase (H6PD) gene interacts to cause cortisone reductase deficiency (CRD) when at least three alleles are affected. OBJECTIVE: The aim was to study the separate and combined effects of these polymorphisms on body composition, adrenal androgen production, blood pressure, glucose metabolism, and the incidence of dementia in the healthy elderly population. DESIGN/SETTING/PARTICIPANTS: The Rotterdam study (n = 6105) and the Frail Old Men study (n = 347) are population-based cohort studies in the elderly. MAIN OUTCOME MEASURES: Genotype distributions and influences of (combined) genotypes on body mass index, adrenal androgen production, waist to hip ratio, systolic and diastolic blood pressure, fasting glucose levels, glucose tolerance test, and incidence of dementia were measured. RESULTS: No influence of the HSD11B1 83,557insA (allele frequencies 22.0 and 21.5%) and H6PD R453Q (allele frequencies 22.9 and 20.2%) variants was found for the different outcome measures that were investigated, either separately or when at least three alleles were affected. CONCLUSIONS: Two population-based studies among Caucasian elderly showed no evidence for (combined) effects of two polymorphisms in the HSD11B1 and H6PD genes on body composition, adrenal androgen production, blood pressure, glucose metabolism, and incidence of dementia. Moreover, the high frequencies observed for these two polymorphisms do not correspond to the low incidence of CRD observed in the general population. Altogether, it is unlikely that these polymorphisms cause CRD.

Associations between promoter usage and alternative splicing of the glucocorticoid receptor gene.

The glucocorticoid receptor (GR) is widely expressed in various tissues throughout the human body. At least three different 3'-splice variants of the GR have been reported: GR-alpha, which is functionally active; GR-beta, which is a dominant negative inhibitor of GR-alpha function; and GR-P, which is thought to activate the function of GR-alpha. At least seven different variants for exon 1 exist, 1A-1F and 1H, each with its own promoter. In this study, we explored if tissue-specific splicing of the 3'-end variants of the GR is influenced by alternative promoter usage. cDNAs of different tissues and cell lines were used to investigate which part of transcripts carrying each of the three major variants for exons 1, 1A, 1B, or 1C, encodes for the splice variants GR-alpha, GR-beta, and GR-P. Our data demonstrate that the expression of GR-alpha is preferentially regulated by promoter 1C and that for the expression of GR-P promoter 1B is predominantly used. This indicates that regulation of GR splice variants could partly occur through selective use of the multiple promoters, and that this is another way to sensitize cells and tissues to the different activities of the GR isoforms.

Androgen receptor ligand-binding domain interaction and nuclear receptor specificity of FXXLF and LXXLL motifs as determined by L/F swapping.

The androgen receptor (AR) ligand-binding domain (LBD) binds FXXLF motifs, present in the AR N-terminal domain and AR-specific cofactors, and some LXXLL motifs of nuclear receptor coactivators. We demonstrated that in the context of the AR FXXLF motif many different amino acid residues at positions +2 and +3 are compatible with strong AR LBD interaction, although a preference for E at +2 and K or R at +3 was found. Pairwise systematic analysis of F/L swaps at +1 and +5 in FXXLF and LXXLL motifs showed: 1) F to L substitutions in natural FXXLF motifs abolished AR LBD interaction; 2) binding of interacting LXXLL motifs was unchanged or increased upon L to F substitutions; 3) certain noninteracting LXXLL motifs became strongly AR-interacting FXXLF motifs; whereas 4) other nonbinders remained unaffected by L to F substitutions. All FXXLF motifs, but not the corresponding LXXLL motifs, displayed a strong preference for AR LBD. Progesterone receptor LBD interacted with some FXXLF motifs, albeit always less efficiently than corresponding LXXLL motifs. AR LBD interaction of most FXXLF and LXXLL peptides depended on classical charge clamp residue K720, whereas E897 was less important. Other charged residues lining the AR coactivator-binding groove, K717 and R726, modulated optimal peptide binding. Interestingly, these four charged residues affected binding of individual peptides independent of an F or L at +1 and +5 in swap experiments. In conclusion, F residues determine strong and selective peptide interactions with AR. Sequences flanking the core motif determine the specific mode of FXXLF and LXXLL interactions.

Strategies for the characterization of disorders in cortisol sensitivity.

CONTEXT: The clinical presentation of abnormalities in glucocorticoid (GC) sensitivity is diverse, and therefore it is difficult to diagnose this condition. OBJECTIVE AND DESIGN: The objective of the study was to develop strategies for the characterization of GC sensitivity disorders. SETTING: The study was conducted in an outpatient clinic. PATIENTS: Nine patients with GC sensitivity disorders participated. INTERVENTIONS: Sequence analysis of the GC receptor (GR), determination of GR number per cell, GR ligand-binding affinity, and GR splice regulation were performed in freshly prepared peripheral blood mononuclear lymphocytes and Epstein-Barr virus-transformed lymphoblasts. Cellular GC sensitivity was determined ex vivo by measuring the effect of dexamethasone on GC-induced leucine-zipper and IL-2 mRNA levels and on cell proliferation. RESULTS: Differences in GR number per cell, GR affinity, GR splice variants, and effects on transactivation or transrepression of GC-sensitive genes were observed between patients and controls. Epstein-Barr virus transformation of lymphoblasts had no influence on GR affinity but increased the GR number 5-fold in healthy controls. In patients diagnosed as cortisol resistant, however, GR number after transformation was increased significantly less than 5-fold, whereas a higher GR number was observed in a patient suspected of cortisol hypersensitivity. CONCLUSION: This study illustrates several strategies to define abnormalities in GC sensitivity by describing nine patients with affected GC sensitivity, all with a unique clinical course and background.

Glucocorticoid receptor polymorphism affects transrepression but not transactivation.

CONTEXT: Glucocorticoids (GCs) are extensively used in the treatment of inflammatory and autoimmune diseases. Their beneficial effects are thought to be mediated by GC transrepression on gene expression. However, their use is limited by serious adverse effects, presumably mediated by GC transactivation of gene expression. OBJECTIVE: The objective of the study was to investigate the effect of the GC receptor haplotype, characterized by the GR-9beta polymorphism, on GC transactivation and transrepression. DESIGN AND METHODS: This was a cross-sectional study in 216 persons randomly selected from participants in The Rotterdam Study, a population-based cohort study in the elderly. Clinical and biochemical parameters of GC sensitivity were measured: weight, height, waist to hip ratio, glucose, insulin, total cholesterol, high-density lipoprotein, and C-reactive protein. In a dexamethasone suppression test, the response of serum cortisol concentrations was studied. Genotyping for four GC receptor polymorphisms was performed. In addition, ex vivo experiments were performed with leukocytes of 10 healthy controls and two persons homozygous for the GR-9beta polymorphism, in which the expression of two GC-sensitive genes, GC-induced leucine zipper and IL-2, was measured. RESULTS: Persons carrying the GR-9beta haplotype without 22/23EK (n = 53) revealed no significant differences in their body mass index, waist to hip ratio, fat spectrum, and insulin sensitivity or in their cortisol response to dexamethasone and levels of C-reactive protein, compared with noncarriers (n = 113). Ex vivo, GC-induced up-regulation of GC-induced leucine zipper mRNA via transactivation did not significantly differ in GR-9beta homozygotes, whereas the down-regulation of IL-2 expression via transrepression was decreased. CONCLUSION: Persons carrying the GR-9beta haplotype seem to have a decreased GC transrepression with normal transactivation.

Increased expression of the glucocorticoid receptor-A translational isoform as a result of the ER22/23EK polymorphism.

One of the most intriguing polymorphisms in the GR [glucocorticoid (GC) receptor] gene is in codons 22 and 23 [GAGAGG(GluArg) --> GAAAAG (GluLys)]. This polymorphism is associated with a reduced GC sensitivity, a better metabolic and cardiovascular health profile, and an increased survival rate. Recently, Yudt and Cidlowski reported that two different methionine codons in the GR mRNA may be used as initiation codon: AUG-1 and AUG-27, resulting in two isoforms, the GR-A and the GR-B proteins, respectively. They also showed that the GR-B protein had a stronger transactivating effect in transient transfection experiments. In this study, we elucidated the molecular basis for the reduced GC sensitivity by investigating the influence of the ER22/23EK polymorphism on synthesis of GR-A and GR-B by expressing them independently from constructs with and without the polymorphic site. Binding studies with [(3)H]-dexamethasone and transactivation studies showed that, when the ER22/23EK polymorphism is present, approximately 15% more GR-A protein was expressed, whereas total GR levels (GR-A + GR-B) were not affected. These results show that the transcriptional activity in GR(ER22/23EK) carriers is decreased because more of the less transcriptionally active GR-A isoform is formed. This is probably caused by altered secondary mRNA structure.

REPS2/POB1 is downregulated during human prostate cancer progression and inhibits growth factor signalling in prostate cancer cells.

During progression of prostate cancer, cellular changes occur, leading to a transition from androgen-dependent to androgen-independent growth. One aspect of this transition is a switch from androgens to growth factors, like epidermal growth factor (EGF), as primary regulators of proliferation. We examined the involvement of REPS2/POB1 in this process. REPS2/POB1 is an EH domain-containing protein, reported to be involved in signalling via RalBP1 and to play a role in endocytosis of EGF receptors. Furthermore, the protein is relatively highly expressed in androgen-dependent as compared to androgen-independent human prostate cancer cell lines and xenografts. Next to the known REPS2/POB1 protein, an open reading frame encoding REPS2/POB1, with 139 additional amino-acid residues at the NH(2)-terminus, was cloned and found to be expressed in prostate cancer cells. Overexpression, by transient transfection, of both forms of REPS2/POB1 in prostate cancer cell lines, induced apoptosis within 48 h. At shorter time intervals after transfection, signalling towards a TPA response element luciferase reporter was found to be inhibited. From these experiments, it is concluded that REPS2/POB1, through its influence on the Ral signalling pathway, is involved in growth factor signalling. Decreased expression of REPS2/POB1 during progression of prostate cancer may therefore result in loss of control of growth factor signalling and consequently in loss of control of cell proliferation.

Expression of the human glucocorticoid receptor splice variants alpha, beta, and P in peripheral blood mononuclear leukocytes in healthy controls and in patients with hyper- and hypocortisolism.

CONTEXT: The effects of cortisol are mediated by the alpha-isoform of the glucocorticoid receptor (GR). GR-alpha levels and activity are modulated by alternative splicing of the common pre-mRNA into mRNAs for the GR-beta and GR-P isoforms. OBJECTIVE: The objective of this study was to investigate whether chronic hypercortisolism, chronic hypocortisolism, or acute, relative hypocortisolism influences the expression levels of the GR splice variants in mononuclear leukocytes. DESIGN: This was a case-control study. SETTING: The study was performed at a university hospital. PARTICIPANTS: Eighteen patients with Cushing's syndrome, five patients with hypocortisolemia, seven patients undergoing metyrapone testing, and 14 controls were studied. MAIN OUTCOME MEASURES: The main outcome measures were mRNA levels, GR affinity, and number per cell. RESULTS: All three GR mRNA isoforms were detected in participants from all groups at relative levels of alpha/P/beta = 1:0.25:0.001. There was a significant correlation between the expression levels of the three splice variants and between the mRNA levels and the number of receptors per cell. The GR in Cushing patients had an increased Kd (P < 0.05) preoperatively. GR number was not significantly different. Postoperatively, the Kd decreased. GR-beta mRNA expression was increased compared with controls (P < 0.05) and was decreased after surgery (P < 0.05). In patients with chronic hypocortisolism, GR-alpha mRNA expression was increased, and receptor numbers were increased (P < 0.05), whereas GR affinity was normal. No changes were observed in patients undergoing a metyrapone test. CONCLUSIONS: Cushing's syndrome is accompanied by a reversible decrease in GR affinity, possibly related to an increased GR-beta expression, which may be a compensatory mechanism to GC excess. In chronic hypocortisolism, adaptive changes in GR status seem to occur at the level of GR number.

Differential regulation of synthetic glucocorticoids on gene expression levels of glucocorticoid-induced leucine zipper and interleukin-2.

Individual glucocorticoid (GC) sensitivity was determined by measuring the effects of several clinically used GCs on transactivation of the GC-induced leucine zipper (GILZ) gene and on transrepression of the IL-2 gene using quantitative real-time PCR. A clear difference in relative potencies for transactivation and transrepression of the various GCs was observed, suggesting differential effects. To determine whether the in vitro outcomes could predict in vivo effects of GCs, 15 individuals underwent a 0.25-mg dexamethasone (DEX) suppression test (DST) while determining GILZ and IL-2 mRNA levels in their peripheral blood mononuclear cells incubated with hydrocortisone, DEX, budesonide, and prednisolone. No correlations were found between the DST and the two expression assays. However, significant correlations existed between hydrocortisone and DEX (r = 0.52; P = 0.046), hydrocortisone and budesonide (r = 0.48; P = 0.069), and hydrocortisone and prednisolone (r = 0.86; P = 0.007) regarding GILZ mRNA levels, and between hydrocortisone and DEX (r = 0.62; P = 0.014), hydrocortisone and budesonide (r = 0.71; P = 0.003), and hydrocortisone and prednisolone (r = 0.71; P = 0.047) regarding IL-2 mRNA levels. In conclusion, intra- and inter-individual variations in GC sensitivity were observed using two expression assays representing GC-mediated transactivation and transrepression. The two expression assays did not correlate with each other or with the results of the DST. This suggests that regulation of the hypothalamic-pituitary-adrenal axis is more complex. However, within an individual person, these two tests combined might predict what type and dosage of GC will be preferable in individual patients for its inhibitory clinical effects, together with relatively fewer transactivating effects related to adverse effects.

Two polymorphisms in the glucocorticoid receptor gene directly affect glucocorticoid-regulated gene expression.

CONTEXT: Interindividual variation in glucocorticoid (GC)-sensitivity can be partly explained by polymorphisms in the GC receptor (GR) gene. The ER22/23EK and N363S polymorphisms have been described to be associated with lower and higher GC sensitivity, respectively. OBJECTIVE AND DESIGN: We examined the basis of this altered GC sensitivity by expressing GR(N363S) and GR(ER22/23EK) in COS-1 cells and investigating their transactivating and transrepressing capacities using a GC response element-luciferase reporter and a p65-activated nuclear factor kappaB-luciferase reporter, respectively. Furthermore, we evaluated the transactivating and transrepressing capacities of the GR in peripheral blood mononuclear lymphocytes of homozygous and heterozygous carriers of these polymorphisms by determining the maximum effect of dexamethasone on transactivation of the GC-induced leucine-zipper and transinhibition of the IL-2 gene by means of real-time RT-PCR. RESULTS: The effects of the polymorphisms in the GR gene previously observed in population studies were also detected at the level of gene expression. The ER22/23EK polymorphism resulted in a significant reduction of transactivating capacity, in both transfection experiments (-14 +/- 5%, P < 0.05) and peripheral blood mononuclear lymphocytes of carriers of this polymorphism (homozygous: -48 +/- 6%, P < 0.01, n = 1; heterozygous: -21 +/- 4%, P = 0.08, n = 3). The N363S polymorphism, associated with increased GC sensitivity, resulted in a significantly increased transactivating capacity, both in vitro (8 +/- 3%; P < 0.02) and ex vivo (homozygous: 204 +/- 19%, P < 0.0001, n = 1; heterozygous: 124 +/- 8%, P = 0.05, n = 3). Neither the ER22/23EK nor the N363S polymorphism seemed to influence the transrepressing capacity of the GR. CONCLUSION: The presence of these and other GC sensitivity-modulating polymorphisms may have consequences for the use of GCs in a clinical setting.

Functional analysis of a novel androgen receptor mutation, Q902K, in an individual with partial androgen insensitivity.

Androgen insensitivity syndrome (AIS) is caused by defects in the androgen receptor (AR) that render the AR partially or completely inactive. As a result, embryonic sex differentiation is impaired. Here, we describe a novel mutation in the AR found in a patient with partial AIS. The mutation results in a substitution of a glutamine (Q) by a lysine (K) residue at position 902, Q902K. The AR Q902K mutation was investigated in vitro with respect to its functional properties. The equilibrium dissociation constants (K(d)s) of AR Q902K in the presence of either the synthetic androgen R1881 or the natural ligand DHT were slightly elevated. The R1881 dissociation rate (t(1/2)) was increased 3-fold for AR Q902K compared with wild type. Transcriptional activity was decreased to 85% of wild type, and the dose-response curve revealed that the sensitivity to hormone was decreased due to the mutation. Furthermore, the 114-kDa androgen-induced phosphorylated AR protein band was not detectable in genital skin fibroblasts. However, it could be detected in transfected CHO cells expressing the mutant receptor in the presence of 10 and 100 nm R1881. Functional interaction assays and a GST pull-down assay showed that the interaction between the NH2 and COOH terminus of AR Q902K was reduced to 50% of wild type. Furthermore, the transactivation by the coactivator TIF2 (transcriptional intermediary factor 2) was decreased 2- to 3-fold. The half-maximal response in both assays was shifted to a higher hormone concentration compared with wild type. These results indicate that residue Q902 is involved in TIF2 and NH2/COOH interaction and that the Q to K mutation results in a mild impairment of AR function, which can explain the partial AIS phenotype of the patient.

A common polymorphism in the CYP3A7 gene is associated with a nearly 50% reduction in serum dehydroepiandrosterone sulfate levels.

CONTEXT: CYP3A7, expressed in the human fetal liver and normally silenced after birth, plays a major role in the 16alpha-hydroxylation of dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), and estrone. Due to a replacement of part of the CYP3A7 promoter with a sequence identical with the same region in the CYP3A4 promoter (referred to as CYP3A7*1C), some individuals still express a variant of the CYP3A7 gene later in life. OBJECTIVE: The objective of this study was to examine the effect of the CYP3A7*1C polymorphism on serum steroid hormone levels. DESIGN, SETTING, PARTICIPANTS: Two population-based cohort studies were performed. Study group 1 consisted of 208 subjects randomly selected from the Rotterdam Study, and study group 2 consisted of 345 elderly independently living men. MAIN OUTCOME MEASURES: Serum DHEA(S), androstenedione, estradiol, estrone, and testosterone levels were the main outcome measures. RESULTS: In study groups 1 and 2, heterozygous CYP3A7*1C carriers had almost 50% lower DHEAS levels compared with homozygous carriers of the reference allele [study group 1, 1.74 +/- 0.25 vs. 3.33 +/- 0.15 micromol/liter (P = 0.02); study group 2, 2.09 +/- 0.08 vs. 1.08 +/- 0.12 micromol/liter (P < 0.001)]. No differences in circulating DHEA, androstenedione, estradiol, or testosterone levels were found. However, in study group 2, serum estrone levels were lower in heterozygous CYP3A7*1C carriers compared with homozygous carriers of the reference allele (0.11 +/- 0.002 vs. 0.08 +/- 0.006 nmol/liter; P < 0.001). CONCLUSION: The CYP3A7*1C polymorphism causes the persistence of enzymatic activity of CYP3A7 during adult life, resulting in lower circulating DHEAS and estrone levels.

A polymorphism in the glucocorticoid receptor gene, which decreases sensitivity to glucocorticoids in vivo, is associated with low insulin and cholesterol levels.

We investigated whether a polymorphism in codons 22 and 23 of the glucocorticoid (GC) receptor gene [GAGAGG(GluArg) --> GAAAAG(GluLys)] is associated with altered GC sensitivity, anthropometric parameters, cardiovascular risk factors, and sex steroid hormones. In a subgroup of 202 healthy elderly subjects of the Rotterdam Study, we identified 18 heterozygotes (8.9%) for the 22/23EK allele (ER22/23EK carriers). In the highest age group, the number of ER22/23EK carriers was higher (67-82 years, 12.9%) than in the youngest age group (53-67 years, 4.9%; P < 0.05). Two dexamethasone (DEX) suppression tests with 1 and 0.25 mg DEX were performed, and serum cortisol and insulin concentrations were compared between ER22/23EK carriers and noncarriers. After administration of 1 mg DEX, the ER22/23EK group had higher serum cortisol concentrations (54.8 +/- 18.3 vs. 26.4 +/- 1.4 nmol/l, P < 0.0001), as well as a smaller decrease in cortisol (467.0 +/- 31.7 vs. 484.5 +/- 10.3 nmol/l, P < 0.0001). ER22/23EK carriers had lower fasting insulin concentrations (P < 0.001), homeostasis model assessment- insulin resistance (IR) (index of IR, P < 0.05), and total (P < 0.02) and LDL cholesterol concentrations (P < 0.01). Our data suggest that carriers of the 22/23EK allele are relatively more resistant to the effects of GCs with respect to the sensitivity of the adrenal feedback mechanism than noncarriers, resulting in a better metabolic health profile.

Consequences of loss of progesterone receptor expression in development of invasive endometrial cancer.

PURPOSE: In endometrial cancer, loss of progesterone receptors (PR) is associated with more advanced disease. This study aimed to investigate the mechanism of action of progesterone and the loss of its receptors (PRA and PRB) in development of endometrial cancer. EXPERIMENTAL DESIGN: A 9600-cDNA microarray analysis was performed to study regulation of gene expression in the human endometrial cancer subcell line Ishikawa PRAB-36 by the progestagen medroxy progesterone acetate (MPA). Five MPA-regulated genes were selected for additional investigation. Expression of these genes was studied by Northern blot and by immunohistochemistry in Ishikawa subcell lines expressing different PR isoforms. Additionally, endometrial cancer tissue samples were immunohistochemically stained to study the in vivo protein expression of the selected genes. RESULTS: In the PRAB-36 cell line, MPA was found to regulate the expression of a number of invasion- and metastasis-related genes. On additional investigation of five of these genes (CD44, CSPG/Versican, Tenascin-C, Fibronectin-1, and Integrin-beta 1), it was observed that expression and progesterone regulation of expression of these genes varied in subcell lines expressing different PR isoforms. Furthermore, in advanced endometrial cancer, it was shown that loss of expression of both PR and E-cadherin was associated with increased expression CD44 and CSPG/Versican. CONCLUSION: The present study shows that progestagens exert a modulatory effect on the expression of genes involved in tumor cell invasion. As a consequence, loss of PR expression in human endometrial cancer may lead to development of a more invasive phenotype of the respective tumor.

Distinct recognition modes of FXXLF and LXXLL motifs by the androgen receptor.

Among nuclear receptors, the androgen receptor (AR) is unique in that its ligand-binding domain (LBD) interacts with the FXXLF motif in the N-terminal domain, resembling coactivator LXXLL motifs. We compared AR- and estrogen receptor alpha-LBD interactions of the wild-type AR FXXLF motif and coactivator transcriptional intermediary factor 2 LXXLL motifs and variants of these motifs. Random mutagenesis revealed a key role for the F residues in FXXLF motifs in high-affinity and selective AR LBD interaction. The FXXLF motif in full-length AR and transcriptional intermediary factor 2 LXXLL motifs competed for an overlapping binding site. A computer model of the AR LBD/AR FXXLF complex showed that the bulky F residues are buried in a deep coactivator-binding groove. The corresponding groove in estrogen receptor alpha LBD is considerably shallower, explaining lack of binding of any of the FXXLF motifs tested. FXXLF and LXXLL motif interaction depended on different charged amino acid residues in the AR LBD present at opposite ends of the coactivator groove. In conclusion, our data demonstrate the importance of a deep hydrophobic groove and alternative usage of charged amino acids in specifying peptide binding to the AR LBD.

Differential modulation of androgen receptor transcriptional activity by the nuclear receptor co-repressor (N-CoR).

Antiandrogens are widely used agents in the treatment of prostate cancer, as inhibitors of AR (androgen receptor) action. Although the precise mechanism of antiandrogen action is not yet elucidated, recent studies indicate the involvement of nuclear receptor co-repressors. In the present study, the regulation of AR transcriptional activity by N-CoR (nuclear receptor co-repressor), in the presence of different ligands, has been investigated. Increasing levels of N-CoR differentially affected the transcriptional activity of AR occupied with either agonistic or antagonistic ligands. Small amounts of co-transfected N-CoR repressed CPA (cyproterone acetate)- and mifepristone (RU486)-mediated AR activity, but did not affect agonist (R1881)-induced AR activity. Larger amounts of co-transfected N-CoR repressed AR activity for all ligands, and converted the partial agonists CPA and RU486 into strong AR antagonists. In the presence of the agonist R1881, co-expression of the p160 co-activator TIF2 (transcriptional intermediary factor 2) relieved N-CoR repression up to control levels. However, in the presence of RU486 and CPA, TIF2 did not functionally compete with N-CoR, suggesting that antagonist-bound AR has a preference for N-CoR. The AR mutation T877A (Thr877-->Ala), which is frequently found in prostate cancer and affects the ligand-induced conformational change of the AR, considerably reduced the repressive action of N-CoR. The agonistic activities of CPA- and hydroxyflutamide-occupied T877A-AR were hardly affected by N-CoR, whereas TIF2 strongly enhanced their activities. These results indicate that lack of N-CoR action allows these antiandrogens to act as strong agonists on the mutant AR.

Phosphorylation of androgen receptor isoforms.

Phosphorylation of the human AR (androgen receptor) is directly correlated with the appearance of at least three AR isoforms on an SDS/polyacrylamide gel. However, it is still not clear to what extent phosphorylation is involved in the occurrence of isoforms, which sites are phosphorylated and what are the functions of these phosphosites. The human AR was expressed in COS-1 cells and AR phosphorylation was studied further by mutational analyses and by using reversed-phase HPLC and MS. The reversed-phase HPLC elution pattern of the three isoforms revealed that Ser-650 was phosphorylated constitutively. After de novo synthesis, only Ser-650 was phosphorylated in the smallest isoform of 110 kDa and both Ser-650 and Ser-94 were phosphorylated in the second isoform of 112 kDa. The hormone-induced 114 kDa isoform shows an overall increase in phosphorylation of all the isolated peptides. The activities of the Ser-Ala substitution mutant S650A (Ser-650-->Ala) was found to be identical with wild-type AR activation in four different cell lines and three different functional analyses, e.g. transactivation, N- and C-terminal-domain interaction and co-activation by transcriptional intermediary factor 2. This was also found for mutants S94A and S515A with respect to transactivation. However, the S515A mutation, which should eliminate phosphorylation of the potential mitogen-activated protein kinase site, Ser-515, resulted in an unphosphorylated form of the peptide containing Ser-650. This suggests that Ser-515 can modulate phosphorylation at another site. The present study shows that the AR isoform pattern from AR de novo synthesis is directly linked to differential phosphorylation of a distinct set of sites. After mutagenesis of these sites, no major change in functional activity of the AR was observed.