The androgen receptor (AR) amino-terminus imposes androgen-specific regulation of AR gene expression via an exonic enhancer

Identification of Potential Ferroptosis Biomarkers and Analysis of Immune Cell Infiltration in Psoriasis Using Machine Learning

Background

Ferroptosis is a type of cell death characterized by the accumulation of iron-dependent lethal lipid peroxides, which is associated with various pathophysiological processes. Psoriasis is a chronic autoimmune skin disease accompanied by abnormal immune cell infiltration and excessive production of lipid reactive oxygen species (ROS). Currently, its pathogenesis remains elusive, especially the potential role of ferroptosis in its pathophysiological process.

Methods

The microarrays GSE13355 (58 psoriatic skin specimens versus 122 healthy skin specimens) and the ferroptosis database were employed to identify the common differentially expressed genes (DEGs) associated with psoriasis and ferroptosis. The functions of common DEGs were investigated through functional enrichment analysis and protein-protein interaction analysis. The potential diagnostic markers for psoriasis among the common DEGs were identified using four machine-learning algorithms. DGIdb was utilized to explore potential therapeutic agents for psoriasis. Additionally, CIBERSORT was employed to investigate immune infiltration in psoriasis.

Results

A total of 8 common DEGs associated with psoriasis and ferroptosis were identified, which are involved in intercellular signaling and affect pathways of cell response to stress and stimulation. Four machine-learning algorithms were employed to identify poly (ADP-ribose) polymerase 12 (PARP12), frizzled homolog 7 (FZD7), and arachidonate 15-lipoxygenase (ALOX15B) among the eight common DEGs as potential diagnostic markers for psoriasis. A total of 18 drugs targeting the five common DEGs were identified as potential candidates for treating psoriasis. Additionally, significant changes were observed in the immune microenvironment of patients with psoriasis.

Conclusion

This study has contributed to our enhanced comprehension of ferroptosis-related genes as potential biomarkers for psoriasis diagnosis, as well as the alterations in the immune microenvironment associated with psoriasis. Our findings offer valuable insights into the diagnosis and treatment of psoriasis.

Androgen Receptor Signaling in Prostate Cancer and Therapeutic Strategies

Understanding of the molecular mechanisms of prostate cancer has led to development of therapeutic strategies targeting androgen receptor (AR). These androgen-receptor signaling inhibitors (ARSI) include androgen synthesis inhibitor-abiraterone and androgen receptor antagonists-enzalutamide, apalutamide, and darolutamide. Although these medications provide significant improvement in survival among men with prostate cancer, drug resistance develops in nearly all patients with time. This could be through androgen-dependent or androgen-independent mechanisms. Even weaker signals and non-canonical steroid ligands can activate AR in the presence of truncated AR-splice variants, AR overexpression, or activating mutations in AR. AR splice variant, AR-V7 is the most studied among these and is not targeted by available ARSIs. Non-androgen receptor dependent resistance mechanisms are mediated by activation of an alternative signaling pathway when AR is inhibited. DNA repair pathway, PI3K/AKT/mTOR pathway, BRAF-MAPK and Wnt signaling pathway and activation by glucocorticoid receptors can restore downstream signaling in prostate cancer by alternative proteins. Multiple clinical trials are underway exploring therapeutic strategies to overcome these resistance mechanisms.

Peroxisome proliferator-activated receptor γ isoforms differentially regulate preadipocyte proliferation, apoptosis, and differentiation in chickens

Peroxisome proliferator-activated receptor γ (PPARγ) has 2 protein isoforms (PPARγ1 and PPARγ2) generated by alternative promoter usage and alternative splicing. However, their functional uniqueness and similarity remain unclear. In the study, we investigated the effects of lentivirus-mediated overexpression of PPARγ1 and PPARγ2 on proliferation, apoptosis, and differentiation of the immortalized chicken preadipocytes. Cell Counting Kit–8 assay showed PPARγ1 and PPARγ2 overexpression markedly suppressed cell proliferation, and fluorescence activated cell sorting analysis showed that PPARγ1 and PPARγ2 overexpression caused cell cycle arrest at G0/G1 phase. Cell death detection ELISA analysis showed both PPARγ1 and PPARγ2 overexpression induced cell apoptosis. Oil red O staining and gene expression analysis showed both PPARγ1 and PPARγ2 overexpression promoted preadipocyte differentiation. In the presence of PPARγ ligand, rosiglitazone, PPARγ2 overexpression was more potent in inducing apoptosis, promoting adipogenesis, and suppressing cell proliferation than PPARγ1 overexpression. We further explored the molecular basis for their functional differences. Reporter gene assay showed that under ligand conditions, PPARγ2 overexpression resulted in 1.68-fold increase in transcription activity compared with PPARγ1. Electrophoretic mobility shift assay showed both PPARγ1 and PPARγ2 could bind to PPAR response element (PPRE) as heterodimer with retinoid X receptor alpha, and by comparison, PPARγ2 had a higher affinity for PPRE than PPARγ1. Reporter gene assay showed expression PPARγ1 and PPARγ2 similarly induced fatty acid synthase and adipocyte fatty acid–binding protein promoter activity but differentially induced lipoprotein lipase and perilipin 1 promoter activities. Coimmunoprecipitation analysis showed that PPARγ1 and PPARγ2 interacted similarly with the coactivators, Tat-interacting protein 60. Taken together, our results demonstrate that PPARγ1 and PPARγ2 differentially regulate preadipocyte proliferation, apoptosis, and differentiation as a result of their distinct and overlapping molecular functions.

Involvement of the MEN1 Gene in Hormone-Related Cancers: Clues from Molecular Studies, Mouse Models, and Patient Investigations

MEN1 mutation predisposes patients to multiple endocrine neoplasia type 1 (MEN1), a genetic syndrome associated with the predominant co-occurrence of endocrine tumors. Intriguingly, recent evidence has suggested that MEN1 could also be involved in the development of breast and prostate cancers, two major hormone-related cancers. The first clues as to its possible role arose from the identification of the physical and functional interactions between the menin protein, encoded by MEN1, and estrogen receptor α and androgen receptor. In parallel, our team observed that aged heterozygous Men1 mutant mice developed cancerous lesions in mammary glands of female and in the prostate of male mutant mice at low frequencies, in addition to endocrine tumors. Finally, observations made both in MEN1 patients and in sporadic breast and prostate cancers further confirmed the role played by menin in these two cancers. In this review, we present the currently available data concerning the complex and multifaceted involvement of MEN1 in these two types of hormone-dependent cancers.

Human blood-based exposure levels of persistent organic pollutant (POP) mixtures antagonise androgen receptor transactivation and translocation

INTRODUCTION

Human exposure to persistent organic pollutants (POPs) has been linked to genitourinary health-related conditions such as decreased sperm quality, hypospadias, and prostate cancer (PCa). Conventional risk assessment of POPs focuses on individual compounds. However, in real life, individuals are exposed to many compounds simultaneously. This might lead to combinatorial effects whereby the global effect of the mixture is different from the effect of the single elements or subgroups. POP mixtures may act as endocrine disruptors via the androgen receptor (AR) and potentially contribute to PCa development.

AIM

To determine the endocrine disrupting activity of a POP mixture and sub-mixtures based upon exposure levels detected in a human Scandinavian population, on AR transactivation and translocation in vitro.

MATERIALS AND METHODS

The Total POP mixture combined 29 chemicals modelled on the exposure profile of a Scandinavian population and 6 sub-mixtures: brominated (Br), chlorinated (Cl), Cl + Br, perfluorinated (PFAA), PFAA + Br, PFAA + Cl, ranging from 1/10× to 500× relative to what is found in human blood. Transactivation was measured by reporter gene assay (RGA) and translocation activity was measured by high content analysis (HCA), each using stably transfected AR model cell lines.

RESULTS

No agonist activity in terms of transactivation and translocation was detected for any POP mixtures. In the presence of testosterone the Cl + Br mixture at 100× and 500× blood level antagonised AR transactivation, whereas the PFAA mixture at blood level increased AR transactivation (P < 0.05). In the presence of testosterone the Cl and PFAA + Br mixtures at 1/10×, 1×, and 50× blood level antagonised AR translocation (P < 0.05).

CONCLUSION

Taken together, some combinations of POP mixtures can interfere with AR translocation. However, in the transactivation assay, these combinations did not affect gene transactivation. Other POP combinations were identified here as modulators of AR-induced gene transactivation without affecting AR translocation. Thus, to fully evaluate the effect of environmental toxins on AR signalling, both types of assays need to be applied.

Cistrome Data Browser: expanded datasets and new tools for gene regulatory analysis

The Cistrome Data Browser (DB) is a resource of human and mouse cis-regulatory information derived from ChIP-seq, DNase-seq and ATAC-seq chromatin profiling assays, which map the genome-wide locations of transcription factor binding sites, histone post-translational modifications and regions of chromatin accessible to endonuclease activity. Currently, the Cistrome DB contains approximately 47,000 human and mouse samples with about 24,000 newly collected datasets compared to the previous release two years ago. Furthermore, the Cistrome DB has a new Toolkit module with several features that allow users to better utilize the large-scale ChIP-seq, DNase-seq, and ATAC-seq data. First, users can query the factors which are likely to regulate a specific gene of interest. Second, the Cistrome DB Toolkit facilitates searches for factor binding, histone modifications, and chromatin accessibility in any given genomic interval shorter than 2Mb. Third, the Toolkit can determine the most similar ChIP-seq, DNase-seq, and ATAC-seq samples in terms of genomic interval overlaps with user-provided genomic interval sets. The Cistrome DB is a user-friendly, up-to-date, and well maintained resource, and the new tools will greatly benefit the biomedical research community. The database is freely available at http://cistrome.org/db, and the Toolkit is at http://dbtoolkit.cistrome.org.

Association between G1733A (rs6152) polymorphism in androgen receptor gene and recurrent spontaneous abortions in Mexican population

INTRODUCTION

Recurrent spontaneous abortion (RSA) is a multifactorial condition that occurs with a frequency of 0.2-5% in women of reproductive age. Among genetic factors, the single nucleotide polymorphism (SNP) G1733A in the androgen receptor (AR) gene has been associated with its presence in Greek and Iranian populations. Therefore, the aim of this study is to determine its possible association with RSA in this population.

PATIENTS AND METHODS

A total of 156 Mexican RSA (with at least 2 consecutive abortions) unrelated patients and 152 unrelated healthy women were included, the presence of karyotype anomalies in the parents as well as uterine anomalies as well as antiphospholipid antibodies was excluded in patients; while all the controls presented at least two healthy pregnancies and no abortion. In all the included women, the presence of the SNP G1733A was determined by restriction fragment length polymorphism (RFLP) technique.

RESULTS

No significant differences were observed in age between groups. The genotype GG, GA, and AA had a frequency of 0.70, 0.27, and 0.03 in patients and of 0.89, 0.10, and 0.01 in controls [corrected] (p < 0.001); while the A allele frequency was of 0.06 and 0.16 in controls and patients, respectively (p < 0.0001). The difference in allele frequency increased 10-15% when patients with primary RSA (with no live births) and with at least three abortions were included.

CONCLUSIONS

The SNP G1733A of the AR gene is significantly associated with RSA in Mexican patients. These results coincide with previous reports in other populations.

Targeting the androgen receptor pathway in castration-resistant prostate cancer: progresses and prospects

Androgen receptor (AR) signaling is a critical pathway for prostate cancer cells, and androgen-deprivation therapy (ADT) remains the principal treatment for patients with locally advanced and metastatic disease. However, over time, most tumors become resistant to ADT. The view of castration-resistant prostate cancer (CRPC) has changed dramatically in the last several years. Progress in understanding the disease biology and mechanisms of castration resistance led to significant advancements and to paradigm shift in the treatment. Accumulating evidence showed that prostate cancers develop adaptive mechanisms for maintaining AR signaling to allow for survival and further evolution. The aim of this review is to summarize molecular mechanisms of castration resistance and provide an update in the development of novel agents and strategies to more effectively target the AR signaling pathway.

StuI polymorphism on the androgen receptor gene is associated with recurrent spontaneous abortion

PURPOSE

This is a case- control study to determine whether G1733A polymorphism of androgen receptor gene is associated with an increased risk for recurrent spontaneous abortion (RSA).

METHOD

A total of 85 women with at least two recurrent spontaneous abortion before 20th week of gestation composed the study group. Subjects were genotyped by the polymerase chain reaction restriction fragment length polymorphism method.

RESULTS

The observed frequencies of GG, GA and AA genotypes of the G1733A polymorphism were 5.89 %, 82.35 % and 11.76 %, respectively, for the patient group and 71.76 %, 23.51 % and 4.71 %, respectively, for the control group. Allele frequencies of the G1733A polymorphism among patients and controls were 0.47 and 0.84, respectively, for the dominant allele (G) (wild type) and 0.53 and 0.16, respectively, for the A allele (mutant type).

CONCLUSIONS

These results indicated that the androgen receptor G1733A polymorphism is strongly associated with increased risk for RSA.

Androgen receptor (AR) aberrations in castration-resistant prostate cancer

Genetic aberrations affecting the androgen receptor (AR) are rare in untreated prostate cancers (PCs) but have been found in castration-resistant prostate cancers (CRPCs). Further, successful treatment with novel endocrine therapies indicates that CRPCs remain androgen-sensitive. Known AR aberrations include amplification of the AR gene leading to the overexpression of the receptor, point mutations of AR resulting in promiscuous ligand usage, and constitutively active AR splice variants. Gain, or amplification, of the AR gene is one of the most frequent genetic alterations observed in CRPCs. Up to 80% of CRPCs have been reported to carry an elevated AR gene copy number, and about 30% have a high-level amplification of the gene. AR mutations are also commonly observed and have been found in approximately 10-30% of the CRPC treated with antiandrogens; however, the frequency and significance of AR splice variants is still unclear. Because AR aberrations are found almost exclusively in CRPC, these alterations must have been selected for during therapy. Interestingly, these aberrations lead to activation of the receptor, despite treatment-induced emergence of therapy-resistant tumor clones. Therefore, future novel treatment strategies should focus on suppressing AR activity in CRPC.

Identification of testosterone-/androgen receptor-regulated genes in mouse Sertoli cells

Androgen and androgen receptor (AR) play important roles in male spermatogenesis and fertility, yet detailed androgen/AR signals in Sertoli cells remain unclear. To identify AR target genes in Sertoli cells, we analyzed the gene expression profiles of testis between mice lacking AR in Sertoli cells (S-AR(-/y)) and their littermate wild-type (WT) mice. Digital gene expression analysis identified 2276 genes downregulated and 2865 genes upregulated in the S-AR(-/y) mice testis compared to WT ones. To further nail down the difference within Sertoli cells, we first constructed Sertoli cell line TM4 with stably transfected AR (named as TM4/AR) and found androgens failed to transactivate AR in Sertoli TM4 and TM4/AR cells. Interestingly, additional transient transfection of AR-cDNA resulted in significant androgen responsiveness with TM4/AR cells showing 10 times more androgen sensitivity than TM4 cells. In the condition where maximal androgen response was demonstrated, we then analyzed gene expression and found the expression levels of 2313 genes were changed more than twofold by transient transfection of AR-cDNA in the presence of testosterone. Among these genes, 603 androgen-/AR-regulated genes, including 164 upregulated and 439 downregulated, were found in both S-AR(-/y) mice testis and TM4/AR cells. Using informatics analysis, the gene ontology was applied to analyze these androgen-/AR-regulated genes to predict the potential roles of androgen/AR in the process of spermatogenesis. Together, using gene analysis in both S-AR(-/y) mice testis and TM4/AR cells may help us to better understand the androgen/AR signals in Sertoli cells and their influences in spermatogenesis.

The Raf/MEK/extracellular signal-regulated kinase 1/2 pathway can mediate growth inhibitory and differentiation signaling via androgen receptor downregulation in prostate cancer cells

Upregulated ERK1/2 activity is correlated with androgen receptor (AR) downregulation in certain prostate cancer (PCa) that exhibits androgen deprivation-induced neuroendocrine differentiation, but its functional relevance requires elucidation. We found that sustained ERK1/2 activation using active Raf or MEK1/2 mutants is sufficient to induce AR downregulation at mRNA and protein levels in LNCaP. Downregulation of AR protein, but not mRNA, was blocked by proteasome inhibitors, MG132 and bortezomib, indicating that the pathway regulation is mediated at multiple points. Ectopic expression of a constitutively active AR inhibited Raf/MEK/ERK-mediated regulation of the differentiation markers, neuron-specific enolase and neutral endopeptidase, and the cyclin-dependent kinase inhibitors, p16(INK4A) and p21(CIP1), but not Rb phosphorylation and E2F1 expression, indicating that AR has a specific role in the pathway-mediated differentiation and growth inhibitory signaling. However, despite the sufficient role of Raf/MEK/ERK, its inhibition using U0126 or ERK1/2 knockdown could not block androgen deprivation-induced AR downregulation in an LNCaP neuroendocrine differentiation model, suggesting that additional signaling pathways are involved in the regulation. We additionally report that sustained Raf/MEK/ERK activity can downregulate full length as well as hormone binding domain-deficient AR isoforms in androgen-refractory C4-2 and CWR22Rv1, but not in LAPC4 and MDA-PCa-2b. Our study demonstrates a novel role of the Raf/MEK/ERK pathway in regulating AR expression in certain PCa types and provides an insight into PCa responses to its aberrant activation.

Molecular basis for gene-specific transactivation by nuclear receptors

Nuclear receptors (NRs) are key transcriptional regulators of metazoan physiology and metabolism. Different NRs bind to similar or even identical core response elements; however, they regulate transcription in a highly receptor- and gene-specific manner. These differences in gene activation can most likely be accounted for by mechanisms involving receptor-specific interactions with DNA as well as receptor-specific interactions with protein complexes binding to adjacent and distant DNA sequences. Here, we review key molecular aspects of transactivation by NRs with special emphasis on the recent advances in the molecular mechanisms responsible for receptor- and gene-specific transcriptional activation. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

The G allele of SNP E1/A118G at the µ-opioid receptor gene locus shows genomic evidence of recent positive selection

Opioid drug response and pain perception differs greatly amongst different individuals. The µ-opioid receptor (MOR) is the main receptor target for important opioid analgesics. As SNPs may contribute to interindividual differences in drug response, in silico signatures of recent positive selection (RPS) were utilized to seek out potentially functional SNPs in the MOR gene in order to facilitate the prioritization of SNPs for evaluation in genetic association studies. Out of over 1000 SNPs at the MOR locus, 184 high-frequency SNPs were interrogated for signatures of RPS. A total of five SNPs (four noncoding and one nonsynonymous coding) demonstrated in silico evidence of RPS. Significantly, the nonsynonymous E1/A118G SNP, which was previously reported to be functionally important, showed in silico evidence of RPS. This reaffirms the feasibility of utilizing in silico signatures of RPS to identify potentially functionally significant SNPs for association studies. Interestingly, the positively selected G allele of this RPS SNP was also predicted to create a novel exon splice enhancer as well as p53 binding sites.

Endothelin-1 enhances the expression of the androgen receptor via activation of the c-myc pathway in prostate cancer cells

Increasing evidence suggests that androgen independent prostate cancer (PC) maintains a functional androgen receptor (AR) pathway despite the low levels of circulating androgen following androgen withdrawal, the molecular mechanisms of which are not well defined yet. To address this question, we investigated the effects of endothelin-1 (ET-1) on AR expression. Western analysis and RT-PCR revealed that in the presence of ET-1, levels of AR significantly increased in a time- and dose-dependent manner in LNCaP cells. Pretreatments with inhibitors of Src and phosphoinositide kinase 3 (PI-3K) suppressed ET-1-induced AR expression. As ET-1 was reported to cause a transient increase in c-myc mRNA levels, we examined the involvement of c-myc in ET-1-mediated AR expression. Transient transfection of c-myc siRNA neutralized ET-1-induced AR expression, suggesting that AR induction by ET-1 is c-myc dependent. AR can regulate the transcription of its own gene via a mechanism in which c-myc plays a crucial role. Therefore, we assessed if ET-1-induced-c-myc leads to the enhancement of AR transcription. Reporter gene assays using the previously identified AR gene enhancer containing a c-myc binding site were conducted in LNCaP cells. We found that ET-1 induced reporter gene activity from the construct containing the wild-type but not mutant c-myc binding site. Chromatin immunoprecipitation assays confirmed that ET-1 increased interaction between c-myc and c-myc binding sites in AR enhancer, suggesting that ET-1-induced AR transcription occurs via c-myc-mediated AR transcription. Together, these data support the notion that ET-1, via Src/PI-3K signaling, augments c-myc expression leading to enhanced AR expression in PC.

Evidence for association of the G1733A polymorphism of the androgen receptor gene with recurrent spontaneous abortions

OBJECTIVE

To determine whether the G1733A polymorphism of the androgen receptor gene is associated with an increased risk for recurrent spontaneous abortion (RSA).

DESIGN

Case-control study.

SETTING

Division of Genetics and Biotechnology, Department of Biology, University of Athens.

PATIENT(S)

A total of 131 women with at least three unexplained spontaneous abortions before 20 weeks' gestation, with the same partner, composed the study group.

INTERVENTION(S)

Subjects were genotyped by the polymerase chain reaction-restriction fragment length polymorphism method.

MAIN OUTCOME MEASURE(S)

G1733A polymorphism genotypes and allele frequencies.

RESULT(S)

The observed frequencies of GG, GA, and AA genotypes of the G1733A polymorphism were 0.57, 0.27, and 0.16, respectively, for the patient group and 0.76, 0.15, and 0.09, respectively, for the control group. Allele frequencies were 0.70 and 0.84, respectively, for the patient and control groups for the G allele (wild type) and 0.30 and 0.16, respectively, for the patient and control groups for the A allele (mutant). Statistical analysis of these results indicated significant differences between the two groups.

CONCLUSION(S)

These results indicated for the first time that the androgen receptor G1733A polymorphism is strongly associated with increased risk for RSA.

An ultraconserved Hox-Pbx responsive element resides in the coding sequence of Hoxa2 and is active in rhombomere 4

The Hoxa2 gene has a fundamental role in vertebrate craniofacial and hindbrain patterning. Segmental control of Hoxa2 expression is crucial to its function and several studies have highlighted transcriptional regulatory elements governing its activity in distinct rhombomeres. Here, we identify a putative Hox–Pbx responsive cis-regulatory sequence, which resides in the coding sequence of Hoxa2 and is an important component of Hoxa2 regulation in rhombomere (r) 4. By using cell transfection and chromatin immunoprecipitation (ChIP) assays, we show that this regulatory sequence is responsive to paralogue group 1 and 2 Hox proteins and to their Pbx co-factors. Importantly, we also show that the Hox–Pbx element cooperates with a previously reported Hoxa2 r4 intronic enhancer and that its integrity is required to drive specific reporter gene expression in r4 upon electroporation in the chick embryo hindbrain. Thus, both intronic as well as exonic regulatory sequences are involved in Hoxa2 segmental regulation in the developing r4. Finally, we found that the Hox–Pbx exonic element is embedded in a larger 205-bp long ultraconserved genomic element (UCE) shared by all vertebrate genomes. In this respect, our data further support the idea that extreme conservation of UCE sequences may be the result of multiple superposed functional and evolutionary constraints.

Androgen receptor-mediated repression of novel target genes

BACKGROUND

The androgen receptor (AR) plays a pivotal role in prostate cancer (PCa) initiation and progression. To date, studies have focused disproportionately on androgen-stimulated genes such as prostate-specific antigen (PSA), while repressed genes have gained little attention, even though they too may be involved in regulating cell growth, differentiation, and apoptosis.

METHODS

ChIP Display was used to identify putative AR target genes in the ablation-resistant human PCa cell line, C4-2B. Quantitative real-time reverse transcription-PCR analysis was used to measure gene expression in cells subjected to dihydrotestosterone (DHT) timecourse and dose-response, as well as AR knock-down and bicalutamide-treatments.

RESULTS

We report on three genes, KIAA1217, CHRM1, and WBSCR28, which were newly identified in a screen for AR-occupied regions in C4-2B PCa cells, and which were repressed by treatment with DHT. AR knock-down resulted in increased KIAA1217, CHRM1, and WBSCR28 mRNA, indicating that, like PSA stimulation, AR represses these three genes even in the absence of added ligand. DHT decreased KIAA1217 and CHRM1 pre-mRNA levels, suggesting AR-mediated transcriptional inhibition. Cycloheximide attenuated DHT-mediated repression of CHRM1, suggesting the requirement of new protein synthesis. Furthermore, bicalutamide treatment did not mimic, but rather antagonized DHT-mediated KIAA1217 repression. Unlike the handful of androgen-repressed genes studied thus far, AR occupancy at KIAA1217, CHRM1, and WBSCR28 was mapped outside their respective 5'-promoter regions.

CONCLUSIONS

Many more genes likely share AR-mediated gene repression through distal regulatory elements. Further study of such targets and their transcriptional regulation may help explain the receptor's tumorigenicity in PCa.

Calmodulin-androgen receptor (AR) interaction: calcium-dependent, calpain-mediated breakdown of AR in LNCaP prostate cancer cells

Chemotherapy of prostate cancer targets androgen receptor (AR) by androgen ablation or antiandrogens, but unfortunately, it is not curative. Our attack on prostate cancer envisions the proteolytic elimination of AR, which requires a fuller understanding of AR turnover. We showed previously that calmodulin (CaM) binds to AR with important consequences for AR stability and function. To examine the involvement of Ca(2+)/CaM in the proteolytic breakdown of AR, we analyzed LNCaP cell extracts that bind to a CaM affinity column for the presence of low molecular weight forms of AR (intact AR size, approximately 114 kDa). Using an antibody directed against the NH(2)-terminal domain (ATD) of AR on Western blots, we identified approximately 76-kDa, approximately 50-kDa, and 34/31-kDa polypeptides in eluates of CaM affinity columns, suggesting the presence of CaM-binding sites within the 31/34-kDa ATD of AR. Under cell-free conditions in the presence of phenylmethylsulfonyl fluoride, AR underwent Ca(2+)-dependent degradation. AR degradation was inhibited by N-acetyl-leu-leu-norleu, an inhibitor of thiol proteases, suggesting the involvement of calpain. In intact cells, AR breakdown was accelerated by raising intracellular Ca(2+) using calcimycin, and increased AR breakdown was reversed with the cell-permeable Ca(2+) chelator bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra-(acetoxymethyl)-ester. In CaM affinity chromatography studies, the Ca(2+)-dependent protease calpain was bound to and eluted from the CaM-agarose column along with AR. Caspase-3, which plays a role in AR turnover under stress conditions, did not bind to the CaM column and was present in the proenzyme form. Similarly, AR immunoprecipitates prepared from whole-cell extracts of exponentially growing LNCaP cells contained both calpain and calpastatin. Nuclear levels of calpain and calpastatin (its endogenous inhibitor) changed in a reciprocal fashion as synchronized LNCaP cells progressed from G(1) to S phase. These reciprocal changes correlated with changes in AR level, which increased in late G(1) phase and decreased as S phase progressed. Taken together, these observations suggest potential involvement of AR-bound CaM in calcium-controlled, calpain-mediated breakdown of AR in prostate cancer cells.

Genetic variation in the human androgen receptor gene is the major determinant of common early-onset androgenetic alopecia

Androgenetic alopecia (AGA), or male-pattern baldness, is the most common form of hair loss. Its pathogenesis is androgen dependent, and genetic predisposition is the major requirement for the phenotype. We demonstrate that genetic variability in the androgen receptor gene (AR) is the cardinal prerequisite for the development of early-onset AGA, with an etiological fraction of 0.46. The investigation of a large number of genetic variants covering the AR locus suggests that a polyglycine-encoding GGN repeat in exon 1 is a plausible candidate for conferring the functional effect. The X-chromosomal location of AR stresses the importance of the maternal line in the inheritance of AGA.

Differential gene up-regulation by hypoxia-inducible factor-1alpha and hypoxia-inducible factor-2alpha in HEK293T cells

Cells exposed to hypoxia respond by increasing the level of hypoxia-inducible factor-1 (HIF-1). This factor then activates a number of genes by binding to hypoxia response elements in their promoter regions. A second hypoxia-responsive factor, HIF-2, can activate many of the same genes as HIF-1. Overexpression of HIFs accompanies the pathogenesis of many tumors. It is unclear, however, as to the respective role of these factors in responsiveness to hypoxia and other stresses. To address this issue, we used microarray technology to study the genes activated in HEK293T cells by hypoxia or transfection with the alpha chain of HIF-1 (or mutant HIF-1 resistant to degradation) or HIF-2. Fifty-six genes were found to be up-regulated at least 3-fold by either hypoxia or transfection. Of these, 21 were elevated both by transfection with HIF-1alpha and with HIF-2alpha, and 14 were preferentially activated by HIF-1alpha including several involved in glycolysis. Ten genes were preferentially activated by HIF-2alpha, including two (CACNA1A and PTPRZ1) implicated in neurologic diseases. Interestingly, most HIF-2alpha-responsive genes were not substantially activated by hypoxia. An additional 10 genes were up-regulated by hypoxia but minimally activated by HIF-1alpha or HIF-2alpha transfection. Ten of the genes were studied by quantitative real-time PCR and/or by Northern blot and the results paralleled those found with microarray technology. Although confirmation in other systems will be necessary, these results indicate that whereas some genes are robustly activated by both HIF-1 and HIF-2, others can be preferentially activated by one or the other factor.

Androgen-induced mineralization by MC3T3-E1 osteoblastic cells reveals a critical window of hormone responsiveness

Despite their clinical importance for skeletal growth and homeostasis, the actions of androgens on osteoblastic cells are not well understood. MC3T3-E1 cells, a nontransformed murine preosteoblastic cell line, that traverse the stages of osteoblastic differentiation within 30 days in vitro, were exposed to mibolerone (an androgen receptor (AR) agonist) or 5alpha-dihydroxytestosterone (DHT) from days 3 to 30 post-plating. Cells exposed to this hormonal regimen exhibited a significant increase in mineralization (calcium deposition) compared to vehicle-treated cells. Delaying treatment for 4-11 days (treatment still completed on day 30 post-plating) enhanced mineralization further. Within 2 days post-plating, AR protein increased 7.2-fold in androgen-treated cells and 2.5-fold in vehicle-treated cells. MC3T3-E1 cells transfected with an androgen- and glucocorticoid-responsive reporter construct on day 1 post-plating followed by a 2 day exposure to DHT, mibolerone, or dexamethasone (dex; a glucocorticoid receptor agonist) exhibited reporter gene activation only with dex treatment. In contrast, delaying transfection and treatment for at least 1 day resulted in comparable androgen- and dex-mediated reporter gene transactivation. Therefore, the ability of MC3T3-E1 cells to respond to androgens is dependent on the timing of androgen administration.

Transactivation functions of the N-terminal domains of nuclear hormone receptors: protein folding and coactivator interactions

The N-terminal domains (NTDs) of many members of the nuclear hormone receptor (NHR) family contain potent transcription-activating functions (AFs). Knowledge of the mechanisms of action of the NTD AFs has lagged, compared with that concerning other important domains of the NHRs. In part, this is because the NTD AFs appear to be unfolded when expressed as recombinant proteins. Recent studies have begun to shed light on the structure and function of the NTD AFs. Recombinant NTD AFs can be made to fold by application of certain osmolytes or when expressed in conjunction with a DNA-binding domain by binding that DNA-binding domain to a DNA response element. The sequence of the DNA binding site may affect the functional state of the AFs domain. If properly folded, NTD AFs can bind certain cofactors and primary transcription factors. Through these, and/or by direct interactions, the NTD AFs may interact with the AF2 domain in the ligand binding, carboxy-terminal portion of the NHRs. We propose models for the folding of the NTD AFs and their protein-protein interactions.

Transcriptional regulation of gene expression by the coding sequence: An attempt to enhance expression of human AChE

In a previous report, Morel and Massoulié showed that Bungarus AChE (bBAChE) is produced more efficiently than rat AChE in various expression systems, mainly because the Bungarus coding sequence exerts a stimulatory effect on transcription (Morel and Massoulié, 2000). They reported that a 5' Bungarus fragment could partially transfer this property to a CAT expression vector. This appeared to offer the possibility of increasing the production of recombinant proteins. In the present paper, we show that insertion of this fragment in the transcribed region, before the polyadenylation site, may have either stimulatory or inhibitory effects, depending on the vector and on the reporter gene. Since the stimulatory effect of Bungarus coding region could not be attached to a small number of discrete motifs, we reasoned that it might result from a general feature of the sequence. Therefore it might be possible to partially transfer this property to the very homologous human AChE (hHAChE) coding sequence by modifications based on synonymous codons, which increased nucleotide identity between the 5' fragment (721 nucleotides) of bBAChE and hHAChE from 71% to 85%. The production of human AChE in transfected COS cells was increased nearly 2-fold with this modified construct, but still remained about 4-fold smaller than that of Bungarus AChE. There was no change in expression level in transformed Pichia pastoris. We thus confirm that coding sequences can strongly influence gene expression, but in a manner that depends on the context and cannot yet be predicted.

Role of androgens in female genital sexual arousal: receptor expression, structure, and function

OBJECTIVE

In women, androgens modulate the physiological function of many reproductive and sexual organs, including the ovaries, uterus, vagina, oviducts, clitoris, and mammary gland. In this article, we review the mechanisms of androgen action and discuss new data on the effects of androgens in vaginal and clitoral tissues.

MAIN OUTCOME MEASURE(S)

In this study, we characterized the androgen receptor expression in rabbit vaginal tissues from control and ovariectomized animals treated with or without androgen replacement therapy. We investigated the effects of androgen deprivation and replacement on the expression and activity of nitric oxide synthase and arginase and on vaginal smooth muscle contractility.

RESULT(S)

Androgens enhanced nitric oxide synthase activity and down-regulated arginase activity in proximal vagina. Estrogens down-regulated nitric oxide synthase activity and increased arginase activity in distal vagina. Androgens facilitated vaginal smooth muscle relaxation to electric field stimulation and vasoactive intestinal polypeptide, whereas estrogens attenuated vaginal tissue relaxation to electric field stimulation and to vasoactive intestinal polypeptide.

CONCLUSION(S)

These observations suggest that androgens may play an important role in modulating the physiology of vaginal tissue and contribute to female genital sexual arousal.