Identification of androgen receptor phosphorylation in the primate ovary in vivo

Female Reproductive Systems: Hormone Dependence and Receptor Expression

The female reproductive system which consists of the ovaries, uterus (myometrium, endometrium), Fallopian tubes, cervix and vagina is exquisitely sensitive to the actions of steroid hormones. The ovaries play a key role in the synthesis of bioactive steroids (oestrogens, androgens, progestins) that act both within the tissue (intracrine/paracrine) as well as on other reproductive organs following release into the blood stream (endocrine action). Sex steroid receptors encoded by the oestrogen (ESR1, ESR2), progesterone (PR) and androgen (AR) receptor genes, which are members of the superfamily of ligand activated transcription factors are widely expressed within these tissues. These receptors play critical role(s) in regulation of cell proliferation, ovulation, endometrial receptivity, myometrial cell function and inflammatory cell infiltration. Our understanding of their importance has been informed by studies on human tissues and cells, which have employed immunohistochemistry as well as a wide range of molecular and genetic methods to identify which processes are dependent steroid ligand activation. The development of mice with targeted deletions of each of these receptors has provided complementary data that has extended our appreciation of cell-cell interactions in the fine tuning of reproductive tissue function. This large body of work has formed the basis of new and improved therapeutics to treat conditions such as infertility.

Physiological and Pathological Androgen Actions in the Ovary

Androgens, although traditionally thought to be male sex steroids, play important roles in female reproduction, both in healthy and pathological states. This mini-review focuses on recent advances in our knowledge of the role of androgens in the ovary. Androgen receptor (AR) is expressed in oocytes, granulosa cells, and theca cells, and is temporally regulated during follicular development. Mouse knockout studies have shown that AR expression in granulosa cells is critical for normal follicular development and subsequent ovulation. In addition, androgens are involved in regulating dynamic changes in ovarian steroidogenesis that are critical for normal cycling. Androgen effects on follicle development have been incorporated into clinical practice in women with diminished ovarian reserve, albeit with limited success in available literature. At the other extreme, androgen excess leads to disordered follicle development and anovulatory infertility known as polycystic ovary syndrome (PCOS), with studies suggesting that theca cell AR may mediate many of these negative effects. Finally, both prenatal and postnatal animal models of androgen excess have been developed and are being used to study the pathophysiology of PCOS both within the ovary and with regard to overall metabolic health. Taken together, current scientific consensus is that a careful balance of androgen activity in the ovary is necessary for reproductive health in women.

Phosphorylation of androgen receptor serine 81 is associated with its reactivation in castration-resistant prostate cancer

Phosphorylation of serine 81 (pS81) in the N-terminal transactivation domain of the androgen receptor (AR) has been linked to its transcriptional activation in prostate cancer (PCa) cell lines, but in vivo studies have been limited. Moreover, the role of pS81 in the reactivation of AR when tumors relapse after androgen deprivation therapy (castration-resistant prostate cancer, CRPC) has not been determined. In this study we validate a pS81 antibody for immunohistochemistry (IHC) and show it yields strong nuclear staining in primary PCa clinical samples and in the VCaP PCa xenograft model. Moreover, this staining was decreased at 7 days post-castration in VCaP xenografts, coinciding with markedly decreased AR transcriptional activity. Staining with the pS81 antibody then was restored when the VCaP xenografts relapsed, which was associated with restoration of AR transcriptional activity. Significantly, analysis of CRPC clinical samples, including tumors that had progressed during treatment with abiraterone, showed strong nuclear staining with the pS81 antibody. Together these findings indicate that AR reactivation in CRPC is associated with S81 phosphorylation, and suggest that IHC for pS81 may be useful as a biomarker of AR activity in CRPC.

Posttranslational Modifications of Steroid Receptors: Phosphorylation

The detection of phosphorylation status of proteins has become a critical component of the analysis of activity, localization, and turnover studies of most proteins, particularly for those involved in signaling. The androgen receptor is no exception to this rule with its localization, transcriptional activity, and interactions determined by a series of key phosphorylations on serine residues. Here we have presented a series of techniques for the investigation of the phosphorylation status and intracellular localization of the androgen receptor after hormone and growth factor stimulation of cells in culture (in vitro) and in prostate cancer tissue (in vivo). Modified methods for immunohistochemistry, immunoblotting and immunofluorescence detection with high efficacy for the measurement and monitoring of androgen receptor are presented here alongside examples of their use.

Androgen Receptor Coregulator CTBP1-AS Is Associated With Polycystic Ovary Syndrome in Chinese Women: A Preliminary Study

Polycystic ovary syndrome (PCOS) is currently considered a predominantly hyperandrogenic syndrome. In theory, hyperandrogenism can be caused by high level of testosterone (T) as well as by enhanced androgen receptor (AR) activity. C-Terminal binding protein 1 antisense (CTBP1-AS) was a novel long noncoding RNA (lncRNA) to regulate AR activity. In this study, we found that expression level of CTBP1-AS in peripheral blood leukocytes was significantly higher in women with PCOS than that in controls after adjustment for age and body mass index (BMI). Individuals having higher expression of CTBP1-AS had significantly greater disease risk than those having lower expression. We also identified expression of CTBP1-AS as an independent risk factor for PCOS. A positive correlation was observed between the CTBP1-AS expression and the total T (TT) concentration either unadjusted or after adjusting for age, BMI, and homeostatic model assessment insulin resistance. Taken together, our current study presented the first evidence that the lncRNA CTBP1-AS, a novel AR modulator, is associated with PCOS in Chinese population and established the possibility that abnormal CTBP1-AS expression is a risk factor for PCOS and it is a predictor of variability in serum TT level in Chinese women with PCOS.

Evidence of androgen action in endometrial and ovarian cancers

Endometrial cancer (EC) and ovarian cancer are common gynaecological malignancies. The impact of androgen action in these cancers is poorly understood; however, there is emerging evidence to suggest that targeting androgen signalling may be of therapeutic benefit. Epidemiological evidence suggests that there is an increased risk of EC associated with exposure to elevated levels of androgens, and genetic variants in genes related to both androgen biosynthesis and action are associated with an increased risk of both EC and ovarian cancer. Androgen receptors (ARs) may be a potential therapeutic target in EC due to reported anti-proliferative activities of androgens. By contrast, androgens may promote growth of some ovarian cancers and anti-androgen therapy has been proposed. Introduction of new therapies targeting ARs expressed in EC or ovarian cancer will require a much greater understanding of the impacts of cell context-specific AR-dependent signalling and how ARs can crosstalk with other steroid receptors during progression of disease. This review considers the evidence that androgens may be important in the aetiology of EC and ovarian cancer with discussion of evidence for androgen action in normal and malignant endometrial and ovarian tissue.

The role of androgen hormones in early follicular development

Background. Although chronic hyperandrogenism, a typical feature of polycystic ovary syndrome, is often associated with disturbed reproductive performance, androgens have been shown to promote ovarian follicle growth in shorter exposures. Here, we review the main effects of androgens on the regulation of early folliculogenesis and the potential of their application in improving follicular in vitro growth. Review. Androgens may affect folliculogenesis directly via androgen receptors (ARs) or indirectly through aromatization to estrogen. ARs are highly expressed in the granulosa and theca cells of early stage follicles and slightly expressed in mature follicles. Short-term androgen exposure augments FSH receptor expression in the granulosa cells of developing follicles and enhances the FSH-induced cAMP formation necessary for the transcription of genes involved in the control of follicular cell proliferation and differentiation. AR activation also increases insulin-like growth factor (IGF-1) and its receptor gene expression in the granulosa and theca cells of growing follicles and in the oocytes of primordial follicles, thus facilitating IGF-1 actions in both follicular recruitment and subsequent development. Conclusion. During the early and intermediate stages of follicular maturation, locally produced androgens facilitate the transition of follicles from the dormant to the growing pool as well as their further development.

Docking and CoMSIA studies on steroids and non-steroidal chemicals as androgen receptor ligands

While some synthetic chemicals have been demonstrated to disrupt normal endocrine function by binding to the androgen receptor (AR), the mechanism by which ligands bind to the ligand binding domain (LBD) remained unclear. In this study, docking and comparative molecular similarity index analysis (CoMSIA) were performed to study the AR ligand binding mechanism of steroids and non-steroidal chemicals. The obtained docking conformations and predictive CoMSIA models (r(pred)(2)values as 0.842 and 0.554) indicated the primary interaction site and key residues in the binding process. The major factors influence the binding affinity of steroids and non-steroidal chemicals were electrostatic and hydrophobic interactions, respectively. The results indicated that besides amino-acid residues Gln711, Arg752 and Thr877 which have previously been reported to be important in binding ligands, Leu701 and Leu704 are also important. Residues Val746, Met749 and Phe764 are crucial only for steroids, while Met742 and Met787 are important only for non-steroidal chemicals. This knowledge of key interactions and important amino-acid residues governing ligands to the AR allow better prediction of potency of AR agonists so that their potential to disrupt AR-mediated pathways and to design less potent alternatives.

CAG repeat polymorphism in androgen receptor gene is not directly associated with polycystic ovary syndrome but influences serum testosterone levels

Hyperandrogenemia has been the most consistent feature of polycystic ovary syndrome (PCOS). Androgens exert their effects through androgen receptors (ARs). The expansion of the codon CAG trinucleotide repeat polymorphism in exon 1 of the AR gene represents a type of genetic alteration associated with changes in the AR gene function. The purpose of this study was to establish a possible association of the AR gene CAG repeat length polymorphism with PCOS, and its influence on clinical and biochemical androgen traits. Two hundred and fourteen Croatian women with PCOS and 209 healthy control women of reproductive age were enrolled. Phenotypic hyperandrogenism, BMI and waist to hip ratio were recorded. Hormonal profiles, fasting insulin and glucose levels were measured on cycle days 3-5. Genotyping of the CAG repeat polymorphism in the AR gene was performed. We found no significant difference in the mean CAG repeat number between the PCOS patients and controls (22.1±3.4 vs. 21.9±3.2, P=0.286). There was a positive correlation between the CAG repeat length and total testosterone (TT) in the PCOS group (R=0.225, P=0.015). A multiple linear regression model using mean CAG repeat length, BMI, age and HOMA-IR as predictors explained 8.5% (adjusted R²) of the variability in serum TT levels. In this model the CAG repeat polymorphism was found to be a significant predictor of serum TT levels in PCOS patients (P=0.015). The logistic regression analysis revealed that the CAG repeat length is not a significant predictor of hirsutism and acne status (P=0.921 and P=0.437, respectively). The model was adjusted for serum TT, free testosterone, androstendione and DHEAS levels as independent variables, which were also not found to be significant predictors of hirsutism (P=0.687, P=0.194, P=0.675 and P=0.938, respectively) or acne status (P=0.594, P=0.095, P=0.290 and P=0.151, respectively). In conclusion, the AR CAG repeat polymorphism is not a major determinant of PCOS in the Croatian population, but it is a predictor of serum TT level variability in women with PCOS.

Intrinsic disorder in the androgen receptor: identification, characterisation and drugability

The androgen receptor (AR) regulates networks of genes in response to the steroid hormones testosterone and dihydrotestosterone. The receptor protein is made up of both stably folded globular domains, involved in hormone and DNA binding, and regions of intrinsic disorder, including the N-terminal domain (NTD). The AR-NTD has a modular activation function (termed AF1) and is important for gene regulation, participating in multiple protein-protein interactions. Biophysical studies have revealed that AR-NTD/AF1 has limited stable secondary structure and conforms to a 'collapsed disordered' conformation. The AR-NTD/AF1 has the propensity to adopt an α-helical conformation in response to a natural osmolyte or a co-regulatory binding partner. The AR is a key drug target in the management of advanced prostate cancer and recently a small molecule inhibitor was identified that interacts with the NTD/AF1 and impairs protein-protein interactions and recruitment of the receptor to target genes. In this review the role of intrinsic disorder in AR function is discussed along with the potential to develop new drugs that will target the structurally plastic NTD.