Calcineurin and CRTC2 mediate FSH and TGFβ1 upregulation of Cyp19a1 and Nr5a in ovary granulosa cells

in Journal of Molecular Endocrinology

Estrogens are essential for female reproduction and overall well-being, and estrogens in the circulation are largely synthesized in ovarian granulosa cells. Using primary cultures of ovarian granulosa cells from gonadotropin-primed immature rats, we have recently discovered that pituitary FSH and ovarian cytokine transforming growth factor beta 1 (TGFβ1) induce calcineurin-mediated dephosphorylation–activation of cAMP-response element-binding protein (CREB)-regulated transcription coactivator (CRTC2) to modulate the expression of Star, Cyp11a1, and Hsd3b leading to increased production of progesterone. This study explored the role of calcineurin and CRTC2 in FSH and TGFβ1 regulation of Cyp19a1 expression in granulosa cells. Ovarian granulosa cells treated with FSH displayed increased aromatase protein at 24 h post-treatment, which subsided by 48 h, while TGFβ1 acting through its type 1 receptor augmented the action of FSH with a greater and longer effects. It is known that the ovary-specific Cyp19a1 PII-promoter contains crucial response elements for CREB and nuclear receptor NR5A subfamily liver receptor homolog 1 (LRH1/NR5A2) and steroidogenic factor 1 (SF1/NR5A1), and that the Nr5a2 promoter also has a potential CREB-binding site. Herein, we demonstrate that FSH+TGFβ1 increased LRH1 and SF1 protein levels, and their binding to the Cyp19a1 PII-promoter evidenced, determined by chromatin immunoprecipitation analysis. Moreover, pretreatment with calcineurin auto-inhibitory peptide (CNI) abolished the FSH+TGFβ1-upregulated but not FSH-upregulated aromatase activity at 48 h, and the corresponding mRNA changes in Cyp19a1, and Nr5a2 and Nr5a1 at 24 h. In addition, FSH and TGFβ1 increased CRTC2 binding to the Cyp19a1 PII-promoter and Nr5a2 promoter at 24 h, with CREB bound constitutively. In summary, the results of this study indicate that calcineurin and CRTC2 have important roles in mediating FSH and TGFβ1 collateral upregulation of Cyp19a1 expression together with its transcription regulators Nr5a2 and Nr5a1 in ovarian granulosa cells.

Abstract

Estrogens are essential for female reproduction and overall well-being, and estrogens in the circulation are largely synthesized in ovarian granulosa cells. Using primary cultures of ovarian granulosa cells from gonadotropin-primed immature rats, we have recently discovered that pituitary FSH and ovarian cytokine transforming growth factor beta 1 (TGFβ1) induce calcineurin-mediated dephosphorylation–activation of cAMP-response element-binding protein (CREB)-regulated transcription coactivator (CRTC2) to modulate the expression of Star, Cyp11a1, and Hsd3b leading to increased production of progesterone. This study explored the role of calcineurin and CRTC2 in FSH and TGFβ1 regulation of Cyp19a1 expression in granulosa cells. Ovarian granulosa cells treated with FSH displayed increased aromatase protein at 24 h post-treatment, which subsided by 48 h, while TGFβ1 acting through its type 1 receptor augmented the action of FSH with a greater and longer effects. It is known that the ovary-specific Cyp19a1 PII-promoter contains crucial response elements for CREB and nuclear receptor NR5A subfamily liver receptor homolog 1 (LRH1/NR5A2) and steroidogenic factor 1 (SF1/NR5A1), and that the Nr5a2 promoter also has a potential CREB-binding site. Herein, we demonstrate that FSH+TGFβ1 increased LRH1 and SF1 protein levels, and their binding to the Cyp19a1 PII-promoter evidenced, determined by chromatin immunoprecipitation analysis. Moreover, pretreatment with calcineurin auto-inhibitory peptide (CNI) abolished the FSH+TGFβ1-upregulated but not FSH-upregulated aromatase activity at 48 h, and the corresponding mRNA changes in Cyp19a1, and Nr5a2 and Nr5a1 at 24 h. In addition, FSH and TGFβ1 increased CRTC2 binding to the Cyp19a1 PII-promoter and Nr5a2 promoter at 24 h, with CREB bound constitutively. In summary, the results of this study indicate that calcineurin and CRTC2 have important roles in mediating FSH and TGFβ1 collateral upregulation of Cyp19a1 expression together with its transcription regulators Nr5a2 and Nr5a1 in ovarian granulosa cells.

Introduction

The steroid hormone estrogen governs female reproductive competence and whole-body well-being (Rosenfeld et al. 2001). Estrogens in the circulation are largely produced in ovarian granulosa cells through aromatase conversion of theca cell-derived androgens (Rosenfeld et al. 2001, Britt & Findlay 2002). Imbalance of estrogen often leads to reproductive dysfunction and exacerbates certain diseases including cancers (Couse & Korach 1999, Yager & Davidson 2006). Knockout of aromatase severely impairs ovarian follicle development as has been indicated by an arrest at the antral stage and formation of hemorrhagic cysts (Fisher et al. 1998, Britt et al. 2001). In addition, deficiency of estrogen or its action is closely associated with cardiovascular, immunological, and neurological abnormalities (Couse & Korach 1999, Mendelsohn & Karas 1999, Stein 2001, Kovacs et al. 2002). As such, it is of crucial importance to understand the regulation of ovarian estrogen synthesis, particularly aromatase gene (Cyp19a1) expression.

Follicle-stimulating hormone (FSH) secreted by the pituitary is the master regulator that stimulates aromatase activity and expression and hence estrogen production in ovarian granulosa cells, and estrogen could, via feed-forward mechanisms, regulate follicle development and maturation including granulosa cell survival, proliferation, and steroidogenic differentiation (Rosenfeld et al. 2001, Britt & Findlay 2002). The use of different promoters confers tissue-specific transcriptional regulation of the Cyp19a1 gene (Bulun et al. 2003). In granulosa cells, this is driven by the ovary-specific PII-promoter that binds cAMP-response element-binding protein (CREB) and nuclear receptor NR5A subfamily liver receptor homolog 1 (LRH1/NR5A2) and steroidogenic factor 1 (SF1/NR5A1), and these are required for FSH and its signaling second messenger cAMP to upregulate aromatase expression (Fitzpatrick & Richards 1994, Michael et al. 1997, Falender et al. 2003, Hinshelwood et al. 2003, Mendelson & Kamat 2007, Stocco 2008). In the ovary, LRH1 is primarily expressed in granulosa cells and luteal cells, whereas SF1 is expressed in theca/interstitial cells and granulosa cells (Falender et al. 2003, Hinshelwood et al. 2003).

By using granulosa cells isolated from ovarian antral follicles developed in rats primed with equine chorionic gonadotropin (eCG) 48 h previously, we have demonstrated that FSH acts in concert with the ovarian cytokine-transforming growth factor beta 1 (TGFβ1) to promote advanced differentiation of granulosa cells, indicated by increased production of progesterone and estrogen (Dodson & Schomberg 1987, Dorrington et al. 1993, Ke et al. 2004, Chen et al. 2007, 2008). FSH is known to act through the cAMP–PKA and PI3K–Akt pathways to regulate steroidogenesis in granulosa cells (Hunzicker-Dunn & Maizels 2006, Chen et al. 2007). In addition, FSH has been reported to activate calcium signaling that is significantly involved in FSH stimulation of progesterone production (Tsang & Carnegie 1983, Carnegie & Tsang 1984, Flores et al. 1990); however, the understanding of the calcium-signal-triggered mechanism remains limited. Calcineurin is an unique protein phosphatase activated by Ca2+–calmodulin binding, which initiates the displacement of calcineurin auto-inhibitory domain from its catalytic domain (Li et al. 2011). Furthermore, calcineurin could modulate CREB activity, acting indirectly through CREB-regulated transcription coactivator (CRTC), initially named transducer of regulated CREB (TORC) (Screaton et al. 2004, Altarejos & Montminy 2011). Upon calcineurin-mediated dephosphorylation–activation, CRTC enters the nucleus and facilitates CREB transcriptional activity through binding to the bZIP domain of CREB (Conkright et al. 2003, Altarejos & Montminy 2011). Interestingly, we have recently demonstrated that FSH and TGFβ1 stimulate CRTC2 activation in ovarian granulosa cells, and further revealed a pivotal role of calcineurin and CRTC2 in FSH and TGFβ1 upregulation of the expression of key steroidogenic genes, such as Star, Cyp11a1, and Hsd3b, responsible for progesterone production (Fang et al. 2012). It was not clear whether FSH-initiated calcium signaling is involved in estrogen synthesis in granulosa cells. Therefore, this study was aimed to determine whether calcineurin and CRTC2 play a central role in the induction of aromatase expression by FSH and TGFβ1 in ovarian granulosa cells. In addition, FSH has been reported to upregulate the expression of NR5A nuclear receptors LRH1 and SF1 in granulosa cells (Falender et al. 2003), and both are involved in FSH stimulation of aromatase expression (Hinshelwood et al. 2003, Parakh et al. 2006). We further explored the potential involvement of calcineurin and CRTC2 in FSH and TGFβ1 regulation of LRH1 and SF1.

Materials and methods

Materials

Ovine FSH (oFSH-19–SIAFP) and eCG were purchased from the National Institute of Diabetes and Digestive and Kidney Diseases & National Hormone & Peptide Program and Dr A F Parlow (Harbor–UCLA Medical Center, Torrance, CA, USA). Recombinant human TGFβ1 and mouse MABs against LRH1 and SF1 were obtained from R&D System, Inc. (Minneapolis, MN, USA). DMEM/F12 culture medium was from Gibco Life Technologies, Inc. Engelbreth–Holm–Swarm sarcoma tumor-derived (EHS) matrigel and mouse MAB against β-actin were from Sigma Chemical Co. Rabbit polyclonal antibody against aromatase was produced and verified at the laboratory of Dr Nobuhiro Harada (Fujita Health University, Aichi, Japan). Rabbit MAB against CREB and goat polyclonal antibody against CRTC2 were respectively purchased from Cell Signaling Technology, Inc. (Danvers, MA, USA) and Santa Cruz Biotechnology, Inc. Calcineurin auto-inhibitory peptide and protein G agarose were from Millipore Corp. (Billerica, MA, USA). SB431542 was obtained from Upstate Biotechnology Co. (Lake Placid, NY, USA). The Moloney murine leukemia virus reverse transcriptase set and Taq DNA polymerase were, respectively, purchased from Toyobo Biologics, Inc. (Osaka, Japan) and Protech Technology Enterprise Co. (Taipei, Taiwan).

Animals

Immature Sprague–Dawley-derived rats (23–25 days of age) were obtained from the Animal Center at National Yang-Ming University (Taipei, Taiwan). The rats were maintained under controlled temperature (22–25 °C) and light conditions (12 h light:12 h darkness). Food (Lab Diet from PMI Feeds, Inc., St Louis, MO, USA) and water were available ad libitum. This study was conducted in accordance with the United States National Research Council's Guide for the Care and Use of Laboratory Animals and National Yang-Ming University institutional guidelines, and was approved by the Institutional Animal Care and Use Committee of National Yang-Ming University.

Cell culture and treatment

Primary cultures of ovarian granulosa cells from gonadotropin (eCG)-primed immature rats were used because FSH is well known to potently increase progesterone synthesis and cAMP level (Carnegie & Tsang 1984, Reaven et al. 1999, Ke et al. 2005, Chen et al. 2007, 2008, Fang et al. 2012). In addition, in vivo eCG priming for 48 h elevated FSH receptor transcript levels in ovarian follicles (Findlay & Drummond 1999). Isolation of ovarian granulosa cells from eCG-primed immature rats was carried out as described previously (Ke et al. 2005). In brief, immature rats received single subcutaneous injections of 15 IU of eCG to stimulate follicle development to the antral follicle stage. Forty-eight hours later, ovarian granulosa cells of mid- to large-sized antral follicles were isolated and inoculated into EHS matrigel-coated culture wares in the growth medium (DMEM/F12, 1:1, 2 μg/ml bovine insulin, 0.1% w/v fatty acid-free BSA, 100 IU/ml penicillin, and 100 μg/ml streptomycin) and were allowed to attach for 20 h at 37 °C, 5% CO2–95% air. The cultured cells were then incubated in an incubation medium (DMEM/F12, 1:1, 0.1% w/v lactalbumin hydrolysate, 100 IU/ml penicillin, and 100 μg/ml streptomycin) for an additional 20 h before the beginning of treatment with FSH±TGFβ1 and other drugs. Low-dose FSH (10 ng/ml) within physiological serum concentration (Besecke et al. 1997, Tébar et al. 1997) was used in our study.

Immunoblotting analysis

Granulosa cells (∼6×106) were cultured in matrigel-coated 60-mm culture dishes and treated as described in the figure legends. Immunoblotting was carried out as previously described (Lai et al. 2013). An equal amount of protein was loaded for each sample, which was then analyzed for aromatase, LRH1, and SF1, with β-actin used as an internal control.

Aromatase activity assay

The granulosa cells (∼5.5×105) were cultured in matrigel-coated 24-well culture plates and treated as described in the figure legends. An hour before the end of culture, androstenedione (final concentration being 10−7 M) was added to serve as the substrate for aromatase. At the end of culture, conditioned media were collected and 17β-estradiol (E2) content was determined by enzyme immunoassay (EIA). E2 antisera and E2–HRP conjugate were produced and verified in the laboratory of Dr Leang-Shin Wu (National Taiwan University, Taipei, Taiwan). First, a 96-well plate was coated with 150 μl of anti-E2 antibody (1:20 000) overnight at 4 °C. After rinsing the plate with wash buffer (150 mM NaCl and 0.05% v/v Tween-20), 100 μl of E2 standards (0.02–10 ng/ml) or conditioned medium samples diluted in EIA buffer (100 mM sodium phosphate, 150 mM NaCl, and 0.1% w/v BSA, pH 7) were added to the well and incubated with 50 μl of E2–HRP (1:20 000) for 2 h at room temperature. The reaction plate was washed and 150 μl of peroxidase substrate 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (Sigma Chemical Co.) at 0.1 mg/ml in reaction buffer (50 mM Na2HPO4 and 25 mM citric acid, pH 5) was added and the plates incubated for 2 h at room temperature. The absorbance of reaction products was measured at 410 nm using a multimode microplate reader (Infinite 200 PRO, Männerdorf, Switzerland).

Immunofluorescence analysis

The granulosa cells (∼5×105) were seeded on matrigel-coated 12-mm cover slips and treated as described in the figure legends. At the end of culture, the cells were fixed with 4% paraformaldehyde for 15 min, permeabilized with 0.05% Triton X-100 for 5 min, and then incubated in the blocking reagent (3% BSA and 3% goat serum in PBS) for 1 h. The cells were then incubated with rabbit antibodies against LRH1/NR5A2 or SF1/NR5A1, or isotypic immunoglobulin, serving as a negative control, for 1 h, followed by Alexa 488-conjugated goat anti-rabbit IgG for 1 h. The cover slips were mounted on glass slides and viewed under a fluorescence microscope (Olympus BX50) equipped with a mercury arc lamp and photographed using SPOT image capture system (Diagnostic Instruments, Inc., Sterling Heights, MI, USA). Only the fluorescence emission intensity, exposure time, and signal output gain value could affect the outcome signal intensity. In order not to have overexposed images, the system was set to automatically capture image of a sample that displayed the most intense fluorescence signal, that is, FSH+TGFβ1-treated cells. Then the exposure time and signal output gain value of this image were used to capture all of the subsequent samples in a single experiment. Using this technique it was possible to ensure that, the fluorescent images would reflect the actual emission signal for comparison among samples.

RT-PCR analysis

The granulosa cells (∼2×106) were cultured in matrigel-coated 35-mm culture dishes. At the end of culture, the cells were extracted for total RNA using TRIzol reagent (Life Technologies, Inc.), and then RNA sample was analyzed using RT-PCR and agarose gel electrophoresis conducted as described previously (Lai et al. 2013) for Cyp19a1, Nr5a1, and Nr5a2, with Gapdh used as an internal control. Forward and reverse primer pairs used are listed in Table 1.

Table 1

Primer pairs used in RT-PCR and Chromatin immunoprecipitation (ChIP) analyses

GeneAccession no.Forward and reverse primer pairProduct length (bp)
RT-PCR analysis
 Cyp19a1NM_017085.25′-CTGCTGATCATGGGCCTCCT-3′341
5′-CTCCACAGGCTCGGGTTGTT-3′
 Nr5a1NM_001191099.15′-GCCCTGCTGGATTACACCTT-3′507
5′-AGACATTCAGGCCCACCAAG-3′
 Nr5a2NM_021742.15′-AAGAAAGCCCTCATTCGAG-3′454
5′-TGTTCCGGTTATTCTGCTC-3′
 GapdhNM_017008.45′-AATGCATCCTGCACCACCAACTGT-3′555
5′-GGAGGCCATGTAGGCCATGAGGTC-3′
ChIP analysis
 Cyp19a1AC_000076.15′-TGAGCATGTGTGTCCTAGG-3′378
5′-CAGTAGTTTGGCTGTGGCTC-3′
 Nr5a2NC_005112.35′-CGGCCGCCGTTATCATCTAA-3′447
5′-TTCAGAAAGGCCCAAGCCAT-3′
 Cyp19a1 exon 10AC_000076.15′-ATTTGGCTTTGGGCCCCGCA-3′ 180
5′-TCCACAATGGGGCTGTCCTCA-3′
 Nr5a2 exon 8NC_005112.35′-CTCTTTTGGCGTGCAGCATT-3′ 207
5′-GCGTCCAAGAGCAGGTCAAT-3′

Chromatin immunoprecipitation analysis

The granulosa cells (∼1.8×107) were cultured in matrigel-coated 100-mm culture dishes. At the end of culture, the cell lysates were prepared and subjected to chromatin immunoprecipitation (ChIP) analysis conducted as described previously (Lai et al. 2013). In brief, 10% of each sample was saved as input, and the rest was immunoprecipitated with CRTC2, CREB, LRH1, or SF1 antibody, and isotypic normal IgG was used as a negative control. DNA was extracted from the immunoprecipitated samples and subjected to analysis by PCR and 2% w/v agarose gel electrophoresis for Cyp19a1 PII-promoter and Nr5a2 promoter regions containing CRE and NR5A sites. Input for each sample was used as an internal control. DNA from each sample was used a template for amplification of the last exon of Cyp19a1 or Nr5a2 with the same cycle number used for the promoter regions (34 cycles) to serve as a PCR negative control. Forward and reverse primer pairs used are listed in Table 1.

Statistical analysis

Quantitative data are presented as the mean (±s.e.m.), and were analyzed by ANOVA and Duncan's multiple-range test at a significance level of 0.05 using the general linear model of the SAS program (SAS Institute, Inc., Cary, NC, USA). Differences between two treatment groups were analyzed using the Student's t-test at a significance level of 0.05.

Results

FSH and TGFβ1 regulation of aromatase and NR5As in rat ovarian granulosa cells

We first investigated FSH and TGFβ1 regulation of aromatase protein in the granulosa cells of rat ovarian antral follicles. The cells treated with FSH (10 ng/ml) for 24 h had an increase in aromatase protein level which subsided by 48 h, and FSH+TGFβ1 treatment exerted a greater and longer effect (24 and 48 h) (Fig. 1A), whereas TGFβ1 treatment alone had no effect (Supplementary Fig. 2, see section on supplementary data given at the end of this article). Consistent with results presented in an earlier report (Dorrington et al. 1993), we observed FSH stimulation of aromatase activity in granulosa cells at 48-h post-treatment, and TGFβ1 potentiated FSH action (Fig. 1B). Herein, we demonstrate that pretreatment with SB431542, an inhibitor of TGFβ type 1 receptor (TGFβR1) kinase activity (Inman et al. 2002), completely suppressed TGFβ1 enhancement of FSH-induced aromatase activity at 48-h post-treatment, and this is in accordance to changes in Cyp19a1 mRNA level at 24-h post-treatment (Fig. 1C). Besides aromatase protein level, TGFβ1 treatment alone also had no significant effect on Cyp19a1 mRNA level (Supplementary Fig. 1). These results indicate that TGFβ1 acts through its type 1 receptor (TGFβR1) to augment FSH induction of Cyp19a1 expression in granulosa cells.

Figure 1
Figure 1

FSH and TGFβ1 regulation of aromatase expression and activity in rat ovarian granulosa cells. (A) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 or 48 h. At the end of culture, cell lysates were prepared and analyzed for aromatase by immunoblotting with β-actin serving as an internal control. Relative density ratios were calculated defining the 24 h control value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3–4). Different lower case letters represent significant differences among groups within the same culture period (P<0.05). (B and C) Cells were pretreated with vehicle or SB431542 (1 μM) for 1 h followed by FSH and/or TGFβ1 treatment for an additional 48 h to determine aromatase activity, or 24 h to determine Cyp19a1 gene expression. (B) For the analysis of aromatase activity, androstenedione was added 1 h before the end of culture when conditioned media were collected and 17β-estradiol content was determined by EIA. Relative ratios of aromatase activity were calculated using FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative aromatase activity (n=6). (C) Total RNAs were extracted and Cyp19a1 mRNA levels were analyzed by RT-PCR using Gapdh as an internal control. Relative density ratios were calculated with the FSH+TGFβ1-treated group value defined as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters represent significant differences among groups without the inhibitor (P<0.05). *Significant difference compared with the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1; SB, SB431542.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Aromatase is also regulated by the NR5A family members LRH1/NR5A2 and SF1/NR5A1, as both are expressed in granulosa cells and could bind to the two NR5A-response element half-sites within the Cyp19a1 PII-promoter (Falender et al. 2003, Hinshelwood et al. 2003). We therefore investigated whether FSH and TGFβ1 regulate the expression of Nr5a, and whether the resulting LRH1 and SF1 modulate Cyp19a1 expression. The granulosa cells treated with FSH for 24 and 48 h had increased levels of SF1 protein but not of LRH1, and treatment with FSH+TGFβ1 markedly increased both LRH1 and SF1 protein and mRNA levels (Figs 2A, and Supplementary Figs 1 and 2). Also, treatment with TGFβ1 alone had no effect on LRH1 and SF1 protein and mRNA levels (Supplementary Figs 1 and 2). In addition, we noticed that both LRH1 and SF1 were predominantly localized in the cell nucleus (Fig. 3), with relative immunostaining intensities among treatment groups similar to those observed in the immunoblotting analysis (Fig. 2). Furthermore, ChIP analysis reveals that FSH+TGFβ1 treatment for 24 h increased LRH1 and SF1 binding to Cyp19a1 PII-promoter (Fig. 2B). These results indicate the important roles of the two NR5As in FSH and TGFβ1 upregulation of Cyp19a1 expression.

Figure 2
Figure 2

FSH and TGFβ1 regulation of LRH1/NR5A2 and SF1/NR5A1 protein and their binding to Cyp19a1 PII-promoter in rat ovarian granulosa cells. (A) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 or 48 h. At the end of culture, cell lysates were prepared and analyzed for LRH1 and SF1 by immunoblotting, with β-actin used as an internal control. Relative density ratios were calculated using the 48-h FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3–4). Different lower case letters represent significant differences among groups within the same culture period (P<0.05). (B) Cells were treated with FSH and/or TGFβ1 for 24 h. Cell lysates were analyzed by ChIP assay using LRH1 or SF1 antibody with isotypic normal IgG serving as a negative control, and input DNA as an internal control. DNA from each sample was amplified by PCR with a primer pair flanking the promoter region, and another primer pair flanking the exon region used as a PCR negative control (Table 1). PCR product intensity was determined and normalized to input DNA. Relative density ratios were calculated with the FSH+TGFβ1-treated group value defined as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). *Significant difference compared with the control (P<0.05). C, control; F, FSH; T, TGFβ1.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Figure 3
Figure 3

Localization of LRH1 and SF1 in rat ovarian granulosa cells. Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. At the end of culture, cells were subjected to immunofluorescence analysis for LRH1 and SF1 with normal mouse IgG used as a negative control. Cells were also stained with DAPI for visualization of cell nuclei.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Involvement of calcineurin in FSH and TGFβ1 regulation of aromatase and NR5A in rat ovarian granulosa cells

Results from our recent work has demonstrated that Ca2+-dependent calcineurin signaling mediates FSH and TGFβ1-stimulated progesterone production and expression of Star, Cyp11a1, and Hsd3b (Fang et al. 2012). Herein, we sought to understand whether calcineurin mediates FSH and TGFβ1 upregulation of aromatase by employing calcineurin auto-inhibitory peptide (CNI). The cell-permeable CNI peptide contains the calcineurin auto-inhibitory domain, and thus is a highly selective inhibitor of calcineurin phosphatase activity. Pretreatment with CNI completely suppressed the additional increase in aromatase activity induced by FSH+TGFβ1 but not the increase induced by FSH alone at 48-h post-treatment, and this is in accordance with changes in Cyp19a1 mRNA levels at 24 h (Fig. 4). Next, we examined FSH and TGFβ1 regulation of Nr5a expression, and the involvement of calcineurin in the process. The granulosa cells treated with FSH+TGFβ1 for 24 h, but not FSH or TGFβ1 alone, had increased mRNA levels of both Nr5a2/LRH1 and Nr5a1/SF1, and pretreatment with CNI completely abrogated such effect (Fig. 5 and Supplementary Fig. 1). These results together indicate that calcineurin crucially mediates FSH and TGFβ1 induction of the expression of Cyp19a1, Nr5a2, and Nr5a1 in ovarian granulosa cells.

Figure 4
Figure 4

Effect of calcineurin inhibitor (CNI) on FSH and TGFβ1 regulation of aromatase in rat ovarian granulosa cells. Cells were pretreated with vehicle or CNI (50 μM) for 1 h followed by treatment with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for an additional 48 h to determine aromatase activity, or 24 h to determine Cyp19a1 gene expression. (A) Aromatase activity was analyzed as described in Fig. 1B. Relative ratios of aromatase activity were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative aromatase activity (n=6). (B) Cyp19a1 mRNA levels were analyzed by RT-PCR as described in Fig. 1C. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters indicate significant differences among groups without the inhibitor (P<0.05). *Significant difference compared to the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Figure 5
Figure 5

Effect of calcineurin inhibitor (CNI) on FSH and TGFβ1 regulation of NR5A expression in rat ovarian granulosa cells. Cells were pretreated with vehicle or CNI (50 μM) for 1 h followed by treatment with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for an additional 24 h. Total RNAs were extracted and analyzed for Nr5a2/LRH1 and Nr5a1/SF1 mRNA levels using RT-PCR as described in Fig. 1C. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters indicate significant differences among groups without the inhibitor (P<0.05). *Significant difference compared with the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Involvement of CRTC2 in FSH and TGFβ1 regulation of aromatase and NR5A in rat ovarian granulosa cells

CRTC2 is a calcineurin-activated CREB coactivator (Screaton et al. 2004, Altarejos & Montminy 2011). Results from our recent study indicated that calcineurin auto-inhibitory peptide CNI could effectively block the FSH and TGFβ1-induced CRTC2 activation in granulosa cells of rat ovarian antral follicles (Fang et al. 2012). Herein, we further investigated whether CRTC2 mediates the action of calcineurin in induction of Cyp19a1 expression by FSH and TGFβ1. In a previous study it was reported that CREB binds to a CRE-like site within the Cyp19a1 PII-promoter (Fitzpatrick & Richards 1994); accordingly, a primer pair flanking such region was designed (Table 1) for ChIP analysis. The granulosa cells treated with FSH for 24 h had increased CRTC2 binding to this region containing CRE-like-site in Cyp19a1 PII-promoter, and TGFβ1 further enhanced the effect of FSH (Fig. 6). In addition, results shown in Fig. 5 indicated that FSH and TGFβ1 increased the mRNA levels of both Nr5a2 and Nr5a1, and that this requires calcineurin activity. We therefore performed promoter sequence analysis of Nr5a2 and Nr5a1 genes, searching for potential CRTC2 regulatory regions containing CRE sites, and identified a putative CREB-binding motif 438 bp upstream of the initiation site in Nr5a2 that is highly conserved among species (Fig. 7A), whereas no potential CRE site was found in the Nr5a1 promoter. ChIP assay was further conducted and revealed that granulosa cells treated with FSH for 24 h had increased CRTC2 binding to the Nr5a2 promoter region containing the potential CRE site, and TGFβ1 further enhanced the effect of FSH (Fig. 7B). Interestingly, CREB exhibited constitutive binding to these promoter regions of Cyp19a1 and Nr5a2 independent of FSH and/or TGFβ1 treatment (Figs 6 and 7). This indicates that with CREB constitutively occupying at the CRE-like site in the Cyp19a1 PII-promoter and Nr5a2 promoter, FSH and TGFβ1-activated CRTC2 may play a key role in enhancement of CREB transcriptional activity to turn on the expression of both genes.

Figure 6
Figure 6

FSH and TGFβ1 regulation of CRTC2 and CREB binding to Cyp19a1 PII-promoter in rat ovarian granulosa cells. Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. Cell lysates were analyzed by ChIP assay using CRTC2 or CREB antibody with isotypic normal IgG serving as a negative control, and input DNA as an internal control. DNA from each sample was amplified by PCR with a primer pair flanking the promoter region, and another primer pair flanking the exon region used as a PCR negative control (Table 1). PCR product intensity was determined and normalized to input DNA. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3). Different lower case letters indicate significant differences among groups (P<0.05). C, control; F, FSH; T, TGFβ1.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Figure 7
Figure 7

FSH and TGFβ1 regulation of CRTC2 and CREB binding to the Nr5a2 promoter in rat ovarian granulosa cells. (A) The Nr5a2 promoter region contains a potential CREB-binding site (shaded area) and is conserved among rats, mice, and humans. *100% identity among species. (B) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. Cell lysates were analyzed by ChIP assay as described in Fig. 5. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3). Different lower case letters indicate significant differences among groups (P<0.05). C, control; F, FSH; T, TGFβ1.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Discussion

The master regulator FSH is well known to act via cAMP–PKA to stimulate aromatase activity and Cyp19a1 expression in ovarian granulosa cells involving key transcription factors, CREB and nuclear receptors LRH1/NR5A2 and SF1/NR5A1 (Fitzpatrick & Richards 1994, Michael et al. 1997, Falender et al. 2003, Hinshelwood et al. 2003, Mendelson & Kamat 2007, Stocco 2008). Using primary cultures of granulosa cells from ovarian antral follicles of gonadotropin-primed immature rats, this study revealed that calcium-dependent calcineurin critically mediates FSH and TGFβ1-marked induction of Cyp19a1 expression through direct and indirect mechanisms discussed as described below. In addition, TGFβ1 acts through its type 1 receptor (TGFβR1) to augment the effect of FSH. The proposed working model is illustrated in Fig. 8.

Figure 8
Figure 8

A proposed working model of FSH and TGFβ1 regulation of Cyp19a1 expression through calcineurin and CRTC2. (A) FSH upregulates Cyp19a1 expression moderately at 24 h post-treatment, and this may involve increased SF1 protein levels and CRTC2 binding to the Cyp19a1 PII-promoter. (B) FSH acts synergistically with TGFβ1 to markedly upregulate Cyp19a1 expression through a direct and an indirect mechanism. The former by inducing Ca2+/calcineurin-dependent activation of CRTC2, which binds to CREB-occupied Cyp19a1 PII-promoter to directly activate Cyp19a1 expression. The latter by facilitating calcineurin-dependent expression of Nr5a2 and Nr5a1 respectively through a CRTC2-mediated and a yet undiscovered mechanism. Also, the upregulated NR5A2/LRH1 and NR5A1/SF1 further bind and transactivate the Cyp19a1 PII-promoter. Thus, acting through the NR5As in a calcineurin-dependent manner, FSH and TGFβ1 also indirectly facilitate Cyp19a1 gene expression. R1, TGFβR. A full colour version of this figure is available via http://dx.doi.org/10.1530/JME-14-0048.

Citation: Journal of Molecular Endocrinology 53, 2; 10.1530/JME-14-0048

Calcineurin could act directly through activation of CRTC2 that may escalate CREB activity to upregulate Cyp19a1 expression in granulosa cells in response to FSH and TGFβ1 stimulation. This is supported by the following lines of evidence. Our recent study using granulosa cells has revealed that FSH induces an early-phase (0.5–1 h) and FSH+TGFβ1 induces a late-phase (24 and 48 h) calcineurin-dependent dephosphorylation–activation of CRTC2 that complexes with CREB to upregulate the expression of the steroidogenic genes Star, Cyp11a1, and Hsd3b (Fang et al. 2012). The results indicated that FSH±TGFβ1 upregulate Cyp19a1 mRNA at 24-h post-treatment with corresponding changes in aromatase protein level and enzymatic activity at 48 h (control<FSH<FSH+TGFβ1; Figs 1 and 4). Also, at 24-h post-treatment TGFβ1 potentiated the FSH-induced increase in CRTC2 binding to the Cyp19a1 PII-promoter region containing a CREB-binding site (control<FSH<FSH+TGFβ1; Fig. 6). Another report using primary breast adipose stromal cells also described how treatment with the adenylyl cyclase activator forskolin increased CRTC2 binding to the Cyp19a1 PII-promoter, and that overexpression of CRTC2 increased Cyp19a1 PII-promoter activity (Brown et al. 2009). This study further demonstrates that pretreatment with the calcineurin auto-inhibitory peptide CNI abolished the FSH+TGFβ1-induced increase in Cyp19a1 mRNA and aromatase activity at 24 and 48 h post-treatment respectively (Fig. 4). Together, these findings indicate that in ovarian granulosa cells of antral follicles FSH stimulates calcineurin-mediated activation of CRTC2 that may complex with CREB and perhaps other coregulator(s) to upregulate Cyp19a1 expression, and that the concomitant presence of TGFβ1 increases the FSH-induced effect.

Besides direct effect on CRTC2-mediated Cyp19a1 expression, calcineurin could act indirectly through LRH1/NR5A2 and SF1/NR5A1 that in turn further enhance the transcription of Cyp19a1 in granulosa cells in response to FSH and TGFβ1 stimulation. At 24-h post-treatment, while FSH treatment alone had no effect, FSH+TGFβ1 increased the mRNA levels of Nr5a2 and Nr5a1, and this was completely diminished in the presence of CNI (Fig. 5). Furthermore, results of immunoblotting and ChIP analysis indicated that granulosa cells treated with FSH+TGFβ1 for 24 h had increased protein levels of LRH1 and SF1, and increased binding of these proteins to the Cyp19a1 PII-promoter (Fig. 2). Moreover, CRTC2 also mediates FSH and TGFβ1 upregulation of Nr5a2 expression as a CREB-binding site was identified in Nr5a2 promoter, and treatment with FSH and TGFβ1 for 24 h increased CRTC2 binding to this region of Nr5a2 the promoter (control<FSH<FSH+TGFβ1; Fig. 7). CRTC2 may enhance transcriptional activity of CREB together with other coregulator(s) on regulating Nr5a2 expression. It has been shown that Nr5a2 is also a target gene of estrogen receptor alpha (ERα (ESR1)) as has been revealed in the MCF7 breast cancer cell line (Annicotte et al. 2005). Also, we have previously demonstrated that ERα crucially mediates the induction by FSH and TGFβ1 of expression of steroidogenic genes, including Hsd3b and Cyp11a1, in granulosa cells (Chen et al. 2008). In addition, in the MCF7 cancer cell line overexpression of GATA4 could increase Nr5a2 promoter activity (Bouchard et al. 2005). While CRTC2–CREB participates in FSH and TGFβ1 upregulation of Nr5a2 promoter activity, additional granulosa-cell-relevant transcription regulators such as ERα and GATA4 may also be engaged and this awaits further study. In addition, although CNI abolished FSH+TGFB1-increased Nr5a1 mRNA level (Fig. 4), no consensus CREB-binding site was found in the Nr5a1 promoter; thus, how calcineurin regulates Nr5a1 awaits further study.

Interestingly, our ChIP analyses disclosed that treatment with FSH±TGFβ1 for 24 h increased CRTC2 binding to the CRE-containing region (∼400–1000 bp) of the Cyp19a1 PII-promoter and the Nr5a2 promoter (control<FSH<FSH+TGFβ1) (Figs 6 and 7, Table 1). In addition though the extent of CREB binding to these regions was similar in all groups, our recent study using coimmunoprecipitation analysis has revealed that treatment with FSH±TGFβ1 for 24 h increased the association of CRTC2 with CREB (control<FSH<FSH+TGFβ1) when phospho-CREB(S133) was barely detectable (Fang et al. 2012). Furthermore, results from previous studies indicated that CRTC could activate CREB transcriptional activity independent of CREB phosphorylation state (Conkright et al. 2003, Takemori et al. 2007). The results of these studies together indicate that despite the CREB(S133) phosphorylation state, FSH and TGFβ1 could promote CRTC2 binding with CREB and thus facilitate the transcriptional activity of CREB on Cyp19a1 and Nr5a2 genes in ovarian granulosa cells. In addition, we and others using primary rat granulosa cell cultures have demonstrated that TGFβ1 augments the FSH-induced advanced differentiation of granulosa cells, marked by increased production of progesterone and estrogen, and the expression of associated key steroidogenic proteins StAR, P450scc, 3β-HSD, and aromatase and gap junction protein connexin 43 (Ying et al. 1986, Dodson & Schomberg 1987, Gitay-Goren et al. 1993, Inoue et al. 2002, Ke et al. 2004, 2005, Chen et al. 2007). Our previous and present studies have revealed that TGFβ1, acting through its type 1 receptor, acts as an important autocrine/paracrine factor, modulating granulosa cell function (Fang et al. 2012). The understanding of how TGFβ1 augments the action of FSH in granulosa cells remains limited. TGFβ1 may modulate the action of FSH at the receptor level. Results from a previous study indicated that TGFβ1 could increase FSH receptor mRNA level and FSH binding activity in granulosa cells (Gitay-Goren et al. 1993, Dunkel et al. 1994). Also, TGFβ1 increased the expression of transcription factor GATA4 in a granulosa tumor cell line KK1 (Anttonen et al. 2006), and GATA4 has recently been reported to bind and stimulate FSH receptor promoter activity in mouse granulosa cells (Bennett et al. 2012).

This study carried out using primary cultures of ovarian granulosa cells retrieved from antral follicles reveals that FSH+TGFβ1 concomitantly upregulate aromatase and NR5As in a calcineurin-dependent manner, with CRTC2 similarly used to regulate both Cyp19a1 and Nr5a2 promoters. Our findings correspond to the in vivo work demonstrating parallel expression pattern of the NR5As and aromatase in granulosa cells of ovarian antral follicles (Mendelson & Kamat 2007), and further supports an important role of TGFβ1 acting synergistically with FSH to stimulate aromatase activity during antral follicle development. In all, this study reveals that calcineurin is critically involved in FSH and TGFβ1 stimulation of Cyp19a1 expression in rat ovarian granulosa cells of antral follicles. FSH and TGFβ1 could induce calcineurin-dependent activation of CRTC2 that plays a permissive role in CREB activation of the Cyp19a1 PII-promoter. Furthermore, FSH+TGFβ1 could also upregulate Cyp19a1 through calcineurin-mediated induction of the NR5A members LRH1 and SF1.

Supplementary data

This is linked to the online version of the paper at http://dx.doi.org/10.1530/JME-14-0048.

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding

This study was supported by grants from National Science Council of Taiwan NSC99-2320-B-010-013-MY3 (to J-J H) and NSC98-2311-B-002-005-MY3 (to F-C K) from Cheng Hsin General Hospital CHGH101-18 (to W-L L), and from the Ministry of Education Aim for the Top University Plan. W-A L was supported by the Physician Scientist Program of National Yang-Ming University, and National Health Research Institutes of Taiwan (DD9801N).

References

  • AltarejosJYMontminyM2011CREB and the CRTC co-activators: sensors for hormonal and metabolic signals. Nature Reviews. Molecular Cell Biology12141151. (doi:10.1038/nrm3072).

    • Search Google Scholar
    • Export Citation
  • AnnicotteJ-SChaveyCServantNTeyssierJBardinALicznarABadiaEPujolPVignonFMaudelondeT2005The nuclear receptor liver receptor homolog-1 is an estrogen receptor target gene. Oncogene2481678175. (doi:10.1038/sj.onc.1208950).

    • Search Google Scholar
    • Export Citation
  • AnttonenMParviainenHKyrönlahtiABielinskaMWilsonDBRitvosOHeikinheimoM2006GATA-4 is a granulosa cell factor employed in inhibin-α activation by the TGF-β pathway. Journal of Molecular Endocrinology36557568. (doi:10.1677/jme.1.01962).

    • Search Google Scholar
    • Export Citation
  • BennettJWuY-GGossenJZhouPStoccoC2012Loss of GATA-6 and GATA-4 in granulosa cells blocks folliculogenesis, ovulation, and follicle stimulating hormone receptor expression leading to female infertility. Endocrinology15324742485. (doi:10.1210/en.2011-1969).

    • Search Google Scholar
    • Export Citation
  • BeseckeLMGuendnerMJSlussPAPolakAGWoodruffTKJamesonJLBauer-DantoinACWeissJ1997Pituitary follistatin regulates activin-mediated production of follicle-stimulating hormone during the rat estrous cycle. Endocrinology13828412848. (doi:10.1210/endo.138.7.5279).

    • Search Google Scholar
    • Export Citation
  • BouchardMFTaniguchiHVigerRS2005Protein kinase A-dependent synergism between GATA factors and the nuclear receptor, liver receptor homolog-1, regulates human aromatase (CYP19) PII promoter activity in breast cancer cells. Endocrinology14649054916. (doi:10.1210/en.2005-0187).

    • Search Google Scholar
    • Export Citation
  • BrittKFindlayJ2002Estrogen actions in the ovary revisited. Journal of Endocrinology175269276. (doi:10.1677/joe.0.1750269).

  • BrittKLDrummondAEDysonMWrefordNGJonesMESimpsonERFindlayJK2001The ovarian phenotype of the aromatase knockout (ArKO) mouse. Journal of Steroid Biochemistry and Molecular Biology79181185. (doi:10.1016/S0960-0760(01)00158-3).

    • Search Google Scholar
    • Export Citation
  • BrownKAMcInnesKJHungerNIOakhillJSSteinbergGRSimpsonER2009Subcellular localization of cyclic AMP-responsive element binding protein-regulated transcription coactivator 2 provides a link between obesity and breast cancer in postmenopausal women. Cancer Research6953925399. (doi:10.1158/0008-5472.CAN-09-0108).

    • Search Google Scholar
    • Export Citation
  • BulunSESebastianSTakayamaKSuzukiTSasanoHShozuM2003The human CYP19 (aromatase P450) gene: update on physiologic roles and genomic organization of promoters. Journal of Steroid Biochemistry and Molecular Biology86219224. (doi:10.1016/S0960-0760(03)00359-5).

    • Search Google Scholar
    • Export Citation
  • CarnegieJATsangBK1984The calcium–calmodulin system: participation in the regulation of steroidogenesis at different stages of granulosa cell differentiation. Biology of Reproduction30515522. (doi:10.1095/biolreprod30.2.515).

    • Search Google Scholar
    • Export Citation
  • ChenYJHsiaoPWLeeMTMasonJIKeFCHwangJJ2007Interplay of PI3K and cAMP/PKA signaling, and rapamycin-hypersensitivity in TGFβ1 enhancement of FSH-stimulated steroidogenesis in rat ovarian granulosa cells. Journal of Endocrinology192405419. (doi:10.1677/JOE-06-0076).

    • Search Google Scholar
    • Export Citation
  • ChenYJLeeMTYaoHCHsiaoPWKeFCHwangJJ2008Crucial role of estrogen receptor-α interaction with transcription coregulators in follicle-stimulating hormone and transforming growth factor β1 up-regulation of steroidogenesis in rat ovarian granulosa cells. Endocrinology14946584668. (doi:10.1210/en.2008-0063).

    • Search Google Scholar
    • Export Citation
  • ConkrightMDCanettieriGScreatonRGuzmanEMiragliaLHogeneschJBMontminyM2003TORCs: transducers of regulated CREB activity. Molecular Cell12413423. (doi:10.1016/j.molcel.2003.08.013).

    • Search Google Scholar
    • Export Citation
  • CouseJFKorachKS1999Estrogen receptor null mice: what have we learned and where will they lead us?Endocrine Reviews20358417. (doi:10.1210/edrv.20.3.0370).

    • Search Google Scholar
    • Export Citation
  • DodsonWCSchombergDW1987The effect of transforming growth factor-β on follicle-stimulating hormone-induced differentiation of cultured rat granulosa cells. Endocrinology120512516. (doi:10.1210/endo-120-2-512).

    • Search Google Scholar
    • Export Citation
  • DorringtonJHBendellJJKhanSA1993Interactions between FSH, estradiol-17β and transforming growth factor-β regulate growth and differentiation in the rat gonad. Journal of Steroid Biochemistry and Molecular Biology44441447. (doi:10.1016/0960-0760(93)90248-U).

    • Search Google Scholar
    • Export Citation
  • DunkelLTillyJLShikoneTNishimoriKHsuehAJ1994Follicle-stimulating hormone receptor expression in the rat ovary: increases during prepubertal development and regulation by the opposing actions of transforming growth factors β and α. Biology of Reproduction50940948. (doi:10.1095/biolreprod50.4.940).

    • Search Google Scholar
    • Export Citation
  • FalenderAELanzRMalenfantDBelangerLRichardsJS2003Differential expression of steroidogenic factor-1 and FTF/LRH-1 in the rodent ovary. Endocrinology14435983610. (doi:10.1210/en.2002-0137).

    • Search Google Scholar
    • Export Citation
  • FangWLLeeMTWuLSChenYJMasonJKeFCHwangJJ2012CREB coactivator CRTC2/TORC2 and its regulator calcineurin crucially mediate follicle-stimulating hormone and transforming growth factor β1 upregulation of steroidogenesis. Journal of Cellular Physiology22724302440. (doi:10.1002/jcp.22978).

    • Search Google Scholar
    • Export Citation
  • FindlayJKDrummondAE1999Regulation of the FSH receptor in the ovary. Trends in Endocrinology and Metabolism10183188. (doi:10.1016/S1043-2760(98)00144-1).

    • Search Google Scholar
    • Export Citation
  • FisherCRGravesKHParlowAFSimpsonER1998Characterization of mice deficient in aromatase (ArKO) because of targeted disruption of the cyp19 gene. PNAS9569656970. (doi:10.1073/pnas.95.12.6965).

    • Search Google Scholar
    • Export Citation
  • FitzpatrickSLRichardsJS1994Identification of a cyclic adenosine 3′,5′-monophosphate-response element in the rat aromatase promoter that is required for transcriptional activation in rat granulosa cells and R2C Leydig cells. Molecular Endocrinology813091319. (doi:10.1210/mend.8.10.7854348).

    • Search Google Scholar
    • Export Citation
  • FloresJAVeldhuisJDLeongDA1990Follicle-stimulating hormone evokes an increase in intracellular free calcium ion concentrations in single ovarian (granulosa) cells. Endocrinology12731723179. (doi:10.1210/endo-127-6-3172).

    • Search Google Scholar
    • Export Citation
  • Gitay-GorenHKimICMiggansSTSchombergDW1993Transforming growth factor β modulates gonadotropin receptor expression in porcine and rat granulosa cells differently. Biology of Reproduction4812841289. (doi:10.1095/biolreprod48.6.1284).

    • Search Google Scholar
    • Export Citation
  • HinshelwoodMMRepaJJSheltonJMRichardsonJAMangelsdorfDJMendelsonCR2003Expression of LRH-1 and SF-1 in the mouse ovary: localization in different cell types correlates with differing function. Molecular and Cellular Endocrinology2073945. (doi:10.1016/S0303-7207(03)00257-0).

    • Search Google Scholar
    • Export Citation
  • Hunzicker-DunnMMaizelsET2006FSH signaling pathways in immature granulosa cells that regulate target gene expression: branching out from protein kinase A. Cellular Signalling1813511359. (doi:10.1016/j.cellsig.2006.02.011).

    • Search Google Scholar
    • Export Citation
  • InmanGJNicolásFJCallahanJFHarlingJDGasterLMReithADLapingNJHillCS2002SB-431542 is a potent and specific inhibitor of transforming growth factor-β superfamily type I activin receptor-like kinase (ALK) receptors ALK4, ALK5, and ALK7. Molecular Pharmacology626574. (doi:10.1124/mol.62.1.65).

    • Search Google Scholar
    • Export Citation
  • InoueKNakamuraKAbeKHirakawaTTsuchiyaMMatsudaHMiyamotoKMinegishiT2002Effect of transforming growth factor β on the expression of luteinizing hormone receptor in cultured rat granulosa cells. Biology of Reproduction67610615. (doi:10.1095/biolreprod67.2.610).

    • Search Google Scholar
    • Export Citation
  • KeFCChuangLCLeeMTChenYJLinSWWangPSStoccoDMHwangJJ2004The modulatory role of transforming growth factor β1 and androstenedione on follicle-stimulating hormone-induced gelatinase secretion and steroidogenesis in rat granulosa cells. Biology of Reproduction7012921298. (doi:10.1095/biolreprod.103.023531).

    • Search Google Scholar
    • Export Citation
  • KeFCFangSHLeeMTSheuSYLaiSYChenYJHuangFLWangPSStoccoDMHwangJJ2005Lindane, a gap junction blocker, suppresses FSH and transforming growth factor β1-induced connexin43 gap junction formation and steroidogenesis in rat granulosa cells. Journal of Endocrinology184555566. (doi:10.1677/joe.1.05776).

    • Search Google Scholar
    • Export Citation
  • KovacsEJMessinghamKAGregoryMS2002Estrogen regulation of immune responses after injury. Molecular and Cellular Endocrinology193129135. (doi:10.1016/S0303-7207(02)00106-5).

    • Search Google Scholar
    • Export Citation
  • LaiWAYehYTLeeMTWuLSKeFCHwangJJ2013Ovarian granulosa cells utilize scavenger receptor SR-BI to evade cellular cholesterol homeostatic control for steroid synthesis. Journal of Lipid Research54365378. (doi:10.1194/jlr.M030239).

    • Search Google Scholar
    • Export Citation
  • LiHRaoAHoganPG2011Interaction of calcineurin with substrates and targeting proteins. Trends in Cell Biology2191103. (doi:10.1016/j.tcb.2010.09.011).

    • Search Google Scholar
    • Export Citation
  • MendelsohnMEKarasRH1999The protective effects of estrogen on the cardiovascular system. New England Journal of Medicine34018011811. (doi:10.1056/NEJM199906103402306).

    • Search Google Scholar
    • Export Citation
  • MendelsonCRKamatA2007Mechanisms in the regulation of aromatase in developing ovary and placenta. Journal of Steroid Biochemistry and Molecular Biology1066270. (doi:10.1016/j.jsbmb.2007.05.001).

    • Search Google Scholar
    • Export Citation
  • MichaelMDMichaelLFSimpsonER1997A CRE-like sequence that binds CREB and contributes to cAMP-dependent regulation of the proximal promoter of the human aromatase P450 (CYP19) gene. Molecular and Cellular Endocrinology134147156. (doi:10.1016/S0303-7207(97)00178-0).

    • Search Google Scholar
    • Export Citation
  • ParakhTNHernandezJAGrammerJCWeckJHunzicker-DunnMZeleznikAJNilsonJH2006Follicle-stimulating hormone/cAMP regulation of aromatase gene expression requires β-catenin. PNAS1031243512440. (doi:10.1073/pnas.0603006103).

    • Search Google Scholar
    • Export Citation
  • ReavenELuaYNomotoATemelRWilliamsDLvan der WesthuyzenDRAzharS1999The selective pathway and a high-density lipoprotein receptor (SR-BI) in ovarian granulosa cells of the mouse. Biochimica et Biophysica Acta1436565576. (doi:10.1016/S0005-2760(98)00169-6).

    • Search Google Scholar
    • Export Citation
  • RosenfeldCWagnerJRobertsRLubahnD2001Intraovarian actions of oestrogen. Reproduction122215226. (doi:10.1530/rep.0.1220215).

  • ScreatonRAConkrightMDKatohYBestJLCanettieriGJeffriesSGuzmanENiessenSYatesJRIIITakemoriH2004The CREB coactivator TORC2 functions as a calcium- and cAMP-sensitive coincidence detector. Cell1196174. (doi:10.1016/j.cell.2004.09.015).

    • Search Google Scholar
    • Export Citation
  • SteinDG2001Brain damage, sex hormones and recovery: a new role for progesterone and estrogen?Trends in Neurosciences24386391. (doi:10.1016/S0166-2236(00)01821-X).

    • Search Google Scholar
    • Export Citation
  • StoccoC2008Aromatase expression in the ovary: hormonal and molecular regulation. Steroids73473487. (doi:10.1016/j.steroids.2008.01.017).

    • Search Google Scholar
    • Export Citation
  • TakemoriHKanematsuMKajimuraJHatanoOKatohYLinXZMinLYamazakiTDoiJOkamotoM2007Dephosphorylation of TORC initiates expression of the StAR gene. Molecular and Cellular Endocrinology265–266196204. (doi:10.1016/j.mce.2006.12.020).

    • Search Google Scholar
    • Export Citation
  • TébarMUilenbroekJTKramerPvan SchaikRHWierikxCDRuizAde JongFHSánchez-CriadoJE1997Effects of progesterone on the secondary surge of follicle-stimulating hormone in the rat. Biology of Reproduction577784. (doi:10.1095/biolreprod57.1.77).

    • Search Google Scholar
    • Export Citation
  • TsangBKCarnegieJA1983Calcium requirement in the gonadotropic regulation of rat granulosa cell progesterone production. Endocrinology113763769. (doi:10.1210/endo-113-2-763).

    • Search Google Scholar
    • Export Citation
  • YagerJDDavidsonNE2006Estrogen carcinogenesis in breast cancer. New England Journal of Medicine354270282. (doi:10.1056/NEJMra050776).

  • YingSYBeckerALingNUenoNGuilleminR1986Inhibin and β type transforming growth factor (TGFβ) have opposite modulating effects on the follicle stimulating hormone (FSH)-induced aromatase activity of cultured rat granulosa cells. Biochemical and Biophysical Research Communications136969975. (doi:10.1016/0006-291X(86)90427-4).

    • Search Google Scholar
    • Export Citation

If the inline PDF is not rendering correctly, you can download the PDF file here.

 

      Society for Endocrinology

Sept 2018 onwards Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 818 125 16
PDF Downloads 221 95 5
  • View in gallery

    FSH and TGFβ1 regulation of aromatase expression and activity in rat ovarian granulosa cells. (A) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 or 48 h. At the end of culture, cell lysates were prepared and analyzed for aromatase by immunoblotting with β-actin serving as an internal control. Relative density ratios were calculated defining the 24 h control value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3–4). Different lower case letters represent significant differences among groups within the same culture period (P<0.05). (B and C) Cells were pretreated with vehicle or SB431542 (1 μM) for 1 h followed by FSH and/or TGFβ1 treatment for an additional 48 h to determine aromatase activity, or 24 h to determine Cyp19a1 gene expression. (B) For the analysis of aromatase activity, androstenedione was added 1 h before the end of culture when conditioned media were collected and 17β-estradiol content was determined by EIA. Relative ratios of aromatase activity were calculated using FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative aromatase activity (n=6). (C) Total RNAs were extracted and Cyp19a1 mRNA levels were analyzed by RT-PCR using Gapdh as an internal control. Relative density ratios were calculated with the FSH+TGFβ1-treated group value defined as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters represent significant differences among groups without the inhibitor (P<0.05). *Significant difference compared with the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1; SB, SB431542.

  • View in gallery

    FSH and TGFβ1 regulation of LRH1/NR5A2 and SF1/NR5A1 protein and their binding to Cyp19a1 PII-promoter in rat ovarian granulosa cells. (A) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 or 48 h. At the end of culture, cell lysates were prepared and analyzed for LRH1 and SF1 by immunoblotting, with β-actin used as an internal control. Relative density ratios were calculated using the 48-h FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3–4). Different lower case letters represent significant differences among groups within the same culture period (P<0.05). (B) Cells were treated with FSH and/or TGFβ1 for 24 h. Cell lysates were analyzed by ChIP assay using LRH1 or SF1 antibody with isotypic normal IgG serving as a negative control, and input DNA as an internal control. DNA from each sample was amplified by PCR with a primer pair flanking the promoter region, and another primer pair flanking the exon region used as a PCR negative control (Table 1). PCR product intensity was determined and normalized to input DNA. Relative density ratios were calculated with the FSH+TGFβ1-treated group value defined as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). *Significant difference compared with the control (P<0.05). C, control; F, FSH; T, TGFβ1.

  • View in gallery

    Localization of LRH1 and SF1 in rat ovarian granulosa cells. Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. At the end of culture, cells were subjected to immunofluorescence analysis for LRH1 and SF1 with normal mouse IgG used as a negative control. Cells were also stained with DAPI for visualization of cell nuclei.

  • View in gallery

    Effect of calcineurin inhibitor (CNI) on FSH and TGFβ1 regulation of aromatase in rat ovarian granulosa cells. Cells were pretreated with vehicle or CNI (50 μM) for 1 h followed by treatment with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for an additional 48 h to determine aromatase activity, or 24 h to determine Cyp19a1 gene expression. (A) Aromatase activity was analyzed as described in Fig. 1B. Relative ratios of aromatase activity were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative aromatase activity (n=6). (B) Cyp19a1 mRNA levels were analyzed by RT-PCR as described in Fig. 1C. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters indicate significant differences among groups without the inhibitor (P<0.05). *Significant difference compared to the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1.

  • View in gallery

    Effect of calcineurin inhibitor (CNI) on FSH and TGFβ1 regulation of NR5A expression in rat ovarian granulosa cells. Cells were pretreated with vehicle or CNI (50 μM) for 1 h followed by treatment with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for an additional 24 h. Total RNAs were extracted and analyzed for Nr5a2/LRH1 and Nr5a1/SF1 mRNA levels using RT-PCR as described in Fig. 1C. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=4). Different lower case letters indicate significant differences among groups without the inhibitor (P<0.05). *Significant difference compared with the respective vehicle control without the inhibitor (P<0.05). C, control; F, FSH; T, TGFβ1.

  • View in gallery

    FSH and TGFβ1 regulation of CRTC2 and CREB binding to Cyp19a1 PII-promoter in rat ovarian granulosa cells. Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. Cell lysates were analyzed by ChIP assay using CRTC2 or CREB antibody with isotypic normal IgG serving as a negative control, and input DNA as an internal control. DNA from each sample was amplified by PCR with a primer pair flanking the promoter region, and another primer pair flanking the exon region used as a PCR negative control (Table 1). PCR product intensity was determined and normalized to input DNA. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3). Different lower case letters indicate significant differences among groups (P<0.05). C, control; F, FSH; T, TGFβ1.

  • View in gallery

    FSH and TGFβ1 regulation of CRTC2 and CREB binding to the Nr5a2 promoter in rat ovarian granulosa cells. (A) The Nr5a2 promoter region contains a potential CREB-binding site (shaded area) and is conserved among rats, mice, and humans. *100% identity among species. (B) Cells were treated with FSH (10 ng/ml) and/or TGFβ1 (0.5 ng/ml) for 24 h. Cell lysates were analyzed by ChIP assay as described in Fig. 5. Relative density ratios were calculated using the FSH+TGFβ1-treated group value as one. Each bar represents mean (±s.e.m.) relative density ratio (n=3). Different lower case letters indicate significant differences among groups (P<0.05). C, control; F, FSH; T, TGFβ1.

  • View in gallery

    A proposed working model of FSH and TGFβ1 regulation of Cyp19a1 expression through calcineurin and CRTC2. (A) FSH upregulates Cyp19a1 expression moderately at 24 h post-treatment, and this may involve increased SF1 protein levels and CRTC2 binding to the Cyp19a1 PII-promoter. (B) FSH acts synergistically with TGFβ1 to markedly upregulate Cyp19a1 expression through a direct and an indirect mechanism. The former by inducing Ca2+/calcineurin-dependent activation of CRTC2, which binds to CREB-occupied Cyp19a1 PII-promoter to directly activate Cyp19a1 expression. The latter by facilitating calcineurin-dependent expression of Nr5a2 and Nr5a1 respectively through a CRTC2-mediated and a yet undiscovered mechanism. Also, the upregulated NR5A2/LRH1 and NR5A1/SF1 further bind and transactivate the Cyp19a1 PII-promoter. Thus, acting through the NR5As in a calcineurin-dependent manner, FSH and TGFβ1 also indirectly facilitate Cyp19a1 gene expression. R1, TGFβR. A full colour version of this figure is available via http://dx.doi.org/10.1530/JME-14-0048.