1
|
Post-Transcriptional Regulation of Gnrhr: A Checkpoint for Metabolic Control of Female Reproduction. Int J Mol Sci 2021; 22:ijms22073312. [PMID: 33805020 PMCID: PMC8038027 DOI: 10.3390/ijms22073312] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/09/2021] [Accepted: 03/20/2021] [Indexed: 12/15/2022] Open
Abstract
The proper expression of gonadotropin-releasing hormone receptors (GnRHRs) by pituitary gonadotropes is critical for maintaining maximum reproductive capacity. GnRH receptor expression must be tightly regulated in order to maintain the normal pattern of expression through the estrous cycle in rodents, which is believed to be important for interpreting the finely tuned pulses of GnRH from the hypothalamus. Much work has shown that Gnrhr expression is heavily regulated at the level of transcription. However, researchers have also discovered that Gnrhr is regulated post-transcriptionally. This review will discuss how RNA-binding proteins and microRNAs may play critical roles in the regulation of GnRHR expression. We will also discuss how these post-transcriptional regulators may themselves be affected by metabolic cues, specifically with regards to the adipokine leptin. All together, we present evidence that Gnrhr is regulated post-transcriptionally, and that this concept must be further explored in order to fully understand the complex nature of this receptor.
Collapse
|
2
|
Yaw AM, McLane-Svoboda AK, Hoffmann HM. Shiftwork and Light at Night Negatively Impact Molecular and Endocrine Timekeeping in the Female Reproductive Axis in Humans and Rodents. Int J Mol Sci 2020; 22:E324. [PMID: 33396885 PMCID: PMC7795361 DOI: 10.3390/ijms22010324] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/24/2020] [Accepted: 12/25/2020] [Indexed: 01/17/2023] Open
Abstract
Shiftwork, including work that takes place at night (nightshift) and/or rotates between day and nightshifts, plays an important role in our society, but is associated with decreased health, including reproductive dysfunction. One key factor in shiftwork, exposure to light at night, has been identified as a likely contributor to the underlying health risks associated with shiftwork. Light at night disrupts the behavioral and molecular circadian timekeeping system, which is important for coordinated timing of physiological processes, causing mistimed hormone release and impaired physiological functions. This review focuses on the impact of shiftwork on reproductive function and pregnancy in women and laboratory rodents and potential underlying molecular mechanisms. We summarize the negative impact of shiftwork on female fertility and compare these findings to studies in rodent models of light shifts. Light-shift rodent models recapitulate several aspects of reproductive dysfunction found in shift workers, and their comparison with human studies can enable a deeper understanding of physiological and hormonal responses to light shifts and the underlying molecular mechanisms that may lead to reproductive disruption in human shift workers. The contributions of human and rodent studies are essential to identify the origins of impaired fertility in women employed in shiftwork.
Collapse
Affiliation(s)
| | | | - Hanne M. Hoffmann
- Department of Animal Science and the Reproductive and Developmental Science Program, Michigan State University, East Lansing, MI 48824, USA
| |
Collapse
|
3
|
Yeh DM, Coss D. PACAP induces FSHβ gene expression via EPAC. Mol Cell Endocrinol 2019; 492:110438. [PMID: 31034837 PMCID: PMC7141571 DOI: 10.1016/j.mce.2019.04.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 04/25/2019] [Accepted: 04/25/2019] [Indexed: 01/01/2023]
Abstract
Gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are heterodimers of a common α subunit and unique β subunits. Regulation of their levels, primarily by GnRH, is critical for reproductive function. Several other hormones modulate gonadotropin expression, either independently or by modifying the responsiveness to GnRH. Pituitary adenylate cyclase activating peptide (PACAP) is one such hormone. Four-hour treatment of female mouse primary pituitary cells by either GnRH or PACAP induced FSHβ expression, while 24-h treatment repressed FSHβ. Both PACAP and GnRH caused FSH secretion into the medium. In the gonadotropes, PACAP activates primarily Gαs and increases concentration of cAMP, while GnRH primarily functions via Gαq and increases calcium concentration. Herein, we compared PACAP and GnRH signaling pathways that lead to the induction of FSHβ expression. Interestingly, constitutively active Gαs represses LHβ and induces FSHβ expression, while Gαq induces both β-subunits. We determined that FSHβ induction by PACAP requires functional EPAC, a cAMP sensor protein that serves as a guanine exchange factors for small G proteins that then bridges cAMP signaling to MAPK pathway. We further demonstrate that in addition to the prototypical small G protein Ras, two members of the Rho subfamily, Rac and CDC42 are also necessary for PACAP induction of FSHβ, likely via activation of p38 MAPK that leads to induction of cFOS, a critical transcription factor that is necessary and sufficient for FSHβ induction. Therefore, PACAP-induced cAMP pathway leads to MAPK activation that stimulates cFOS induction, to induce the expression of FSHβ subunit and increase FSH concentration.
Collapse
Affiliation(s)
| | - Djurdjica Coss
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA, 92521, USA.
| |
Collapse
|
4
|
Robinson G, Porter M, Peltier M, Cleaver B, Farmerie T, Wolfe M, Nilson J, Sharp D. Regulation of Luteinizing Hormone β and α Messenger Ribonucleic Acid by Estradiol or Gonadotropin-Releasing Hormone Following Pituitary Stalk Section in Ovariectomized Pony Mares1. Biol Reprod 2018. [DOI: 10.1093/biolreprod/52.monograph_series1.373] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- G. Robinson
- Department of Animal Science, University of Florida, Gainesville, Florida 32611
| | - M.B. Porter
- Department of Animal Science, University of Florida, Gainesville, Florida 32611
| | - M.R. Peltier
- Department of Animal Science, University of Florida, Gainesville, Florida 32611
| | - B.C. Cleaver
- Department of Animal Science, University of Florida, Gainesville, Florida 32611
| | - T.A. Farmerie
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - M.W. Wolfe
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - J.H. Nilson
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - D.C. Sharp
- Department of Animal Science, University of Florida, Gainesville, Florida 32611
| |
Collapse
|
5
|
Das N, Kumar TR. Molecular regulation of follicle-stimulating hormone synthesis, secretion and action. J Mol Endocrinol 2018; 60:R131-R155. [PMID: 29437880 PMCID: PMC5851872 DOI: 10.1530/jme-17-0308] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 02/07/2018] [Indexed: 12/11/2022]
Abstract
Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.
Collapse
Affiliation(s)
- Nandana Das
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
| | - T. Rajendra Kumar
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Division of Reproductive Endocrinology and Infertility, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Author for Correspondence: T. Rajendra Kumar, PhD, Edgar L. and Patricia M. Makowski Professor, Associate Vice-Chair of Research, Department of Obstetrics & Gynecology, University of Colorado Anschutz Medical Campus, Mail Stop 8613, Research Complex 2, Room # 15-3000B, 12700 E. 19th Avenue, Aurora, CO 80045, USA, Tel: 303-724-8689,
| |
Collapse
|
6
|
Coss D. Regulation of reproduction via tight control of gonadotropin hormone levels. Mol Cell Endocrinol 2018; 463:116-130. [PMID: 28342855 PMCID: PMC6457911 DOI: 10.1016/j.mce.2017.03.022] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/16/2017] [Accepted: 03/21/2017] [Indexed: 01/04/2023]
Abstract
Mammalian reproduction is controlled by the hypothalamic-pituitary-gonadal axis. GnRH from the hypothalamus regulates synthesis and secretion of gonadotropins, LH and FSH, which then control steroidogenesis and gametogenesis. In females, serum LH and FSH levels exhibit rhythmic changes throughout the menstrual or estrous cycle that are correlated with pulse frequency of GnRH. Lack of gonadotropins leads to infertility or amenorrhea. Dysfunctions in the tightly controlled ratio due to levels slightly outside the normal range occur in a larger number of women and are correlated with polycystic ovaries and premature ovarian failure. Since the etiology of these disorders is largely unknown, studies in cell and mouse models may provide novel candidates for investigations in human population. Hence, understanding the mechanisms whereby GnRH regulates gonadotropin hormone levels will provide insight into the physiology and pathophysiology of the reproductive system. This review discusses recent advances in our understanding of GnRH regulation of gonadotropin synthesis.
Collapse
Affiliation(s)
- Djurdjica Coss
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA 92521, United States.
| |
Collapse
|
7
|
Xie H, Hoffmann HM, Iyer AK, Brayman MJ, Ngo C, Sunshine MJ, Mellon PL. Chromatin status and transcription factor binding to gonadotropin promoters in gonadotrope cell lines. Reprod Biol Endocrinol 2017; 15:86. [PMID: 29065928 PMCID: PMC5655979 DOI: 10.1186/s12958-017-0304-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 10/04/2017] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Proper expression of key reproductive hormones from gonadotrope cells of the pituitary is required for pubertal onset and reproduction. To further our understanding of the molecular events taking place during embryonic development, leading to expression of the glycoproteins luteinizing hormone (LH) and follicle-stimulating hormone (FSH), we characterized chromatin structure changes, imparted mainly by histone modifications, in model gonadotrope cell lines. METHODS We evaluated chromatin status and gene expression profiles by chromatin immunoprecipitation assays, DNase sensitivity assay, and RNA sequencing in three developmentally staged gonadotrope cell lines, αT1-1 (progenitor, expressing Cga), αT3-1 (immature, expressing Cga and Gnrhr), and LβT2 (mature, expressing Cga, Gnrhr, Lhb, and Fshb), to assess changes in chromatin status and transcription factor access of gonadotrope-specific genes. RESULTS We found the common mRNA α-subunit of LH and FSH, called Cga, to have an open chromatin conformation in all three cell lines. In contrast, chromatin status of Gnrhr is open only in αT3-1 and LβT2 cells. Lhb begins to open in LβT2 cells and was further opened by activin treatment. Histone H3 modifications associated with active chromatin were high on Gnrhr in αT3-1 and LβT2, and Lhb in LβT2 cells, while H3 modifications associated with repressed chromatin were low on Gnrhr, Lhb, and Fshb in LβT2 cells. Finally, chromatin status correlates with the progressive access of LHX3 to Cga and Gnrhr, followed by PITX1 binding to the Lhb promoter. CONCLUSION Our data show the gonadotrope-specific genes Cga, Gnrhr, Lhb, and Fshb are not only controlled by developmental transcription factors, but also by epigenetic mechanisms that include the modulation of chromatin structure, and histone modifications.
Collapse
Affiliation(s)
- Huimin Xie
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
| | - Hanne M. Hoffmann
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
| | - Anita K. Iyer
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
- 0000 0004 0507 3954grid.185669.5Illumina Inc, 5200 Illumina Way, San Diego, CA 92122 USA
| | - Melissa J. Brayman
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
- Foley and Lardner LLP, 402 West Broadway, Suite 2100, San Diego, CA 92101 USA
| | - Cindy Ngo
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
| | - Mary Jean Sunshine
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
| | - Pamela L. Mellon
- 0000 0001 2107 4242grid.266100.3Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093-0674 USA
| |
Collapse
|
8
|
Norwitz ER, Jeong KH, Chin WW. Molecular Mechanisms of Gonadotropin-Releasing Hormone Receptor Gene Regulation. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/107155769900600402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Errol R. Norwitz
- Division of Maternal-Fetal Medicine, Department of Obstetries & Gynecology, and Division of Molecular Genetics. Department of Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | - William W. Chin
- Division of Maternal-Fetal Medicine, Department of Obstetries & Gynecology, and Division of Molecular Genetics. Department of Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts
| |
Collapse
|
9
|
Park CH, Skarra DV, Rivera AJ, Arriola DJ, Thackray VG. Constitutively active FOXO1 diminishes activin induction of Fshb transcription in immortalized gonadotropes. PLoS One 2014; 9:e113839. [PMID: 25423188 PMCID: PMC4244159 DOI: 10.1371/journal.pone.0113839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 10/31/2014] [Indexed: 11/29/2022] Open
Abstract
In the present study, we investigate whether the FOXO1 transcription factor modulates activin signaling in pituitary gonadotropes. Our studies show that overexpression of constitutively active FOXO1 decreases activin induction of murine Fshb gene expression in immortalized LβT2 cells. We demonstrate that FOXO1 suppression of activin induction maps to the −304/−95 region of the Fshb promoter containing multiple activin response elements and that the suppression requires the FOXO1 DNA-binding domain (DBD). FOXO1 binds weakly to the −125/−91 region of the Fshb promoter in a gel-shift assay. Since this region of the promoter contains a composite SMAD/FOXL2 binding element necessary for activin induction of Fshb transcription, it is possible that FOXO1 DNA binding interferes with SMAD and/or FOXL2 function. In addition, our studies demonstrate that FOXO1 directly interacts with SMAD3/4 but not SMAD2 in a FOXO1 DBD-dependent manner. Moreover, we show that SMAD3/4 induction of Fshb-luc and activin induction of a multimerized SMAD-binding element-luc are suppressed by FOXO1 in a DBD-dependent manner. These results suggest that FOXO1 binding to the proximal Fshb promoter as well as FOXO1 interaction with SMAD3/4 proteins may result in decreased activin induction of Fshb in gonadotropes.
Collapse
Affiliation(s)
- Chung Hyun Park
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - Danalea V. Skarra
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - Alissa J. Rivera
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - David J. Arriola
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - Varykina G. Thackray
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA, United States of America
- * E-mail:
| |
Collapse
|
10
|
Perrett RM, McArdle CA. Molecular mechanisms of gonadotropin-releasing hormone signaling: integrating cyclic nucleotides into the network. Front Endocrinol (Lausanne) 2013; 4:180. [PMID: 24312080 PMCID: PMC3834291 DOI: 10.3389/fendo.2013.00180] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 11/06/2013] [Indexed: 01/21/2023] Open
Abstract
Gonadotropin-releasing hormone (GnRH) is the primary regulator of mammalian reproductive function in both males and females. It acts via G-protein coupled receptors on gonadotropes to stimulate synthesis and secretion of the gonadotropin hormones luteinizing hormone and follicle-stimulating hormone. These receptors couple primarily via G-proteins of the Gq/ll family, driving activation of phospholipases C and mediating GnRH effects on gonadotropin synthesis and secretion. There is also good evidence that GnRH causes activation of other heterotrimeric G-proteins (Gs and Gi) with consequent effects on cyclic AMP production, as well as for effects on the soluble and particulate guanylyl cyclases that generate cGMP. Here we provide an overview of these pathways. We emphasize mechanisms underpinning pulsatile hormone signaling and the possible interplay of GnRH and autocrine or paracrine regulatory mechanisms in control of cyclic nucleotide signaling.
Collapse
Affiliation(s)
- Rebecca M. Perrett
- Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Craig A. McArdle
- Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Bristol, UK
- *Correspondence: Craig A. McArdle, Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, 1 Whitson Street, Bristol BS1 3NY, UK e-mail:
| |
Collapse
|
11
|
Lindaman LL, Yeh DM, Xie C, Breen KM, Coss D. Phosphorylation of ATF2 and interaction with NFY induces c-Jun in the gonadotrope. Mol Cell Endocrinol 2013. [PMID: 23178797 PMCID: PMC3529762 DOI: 10.1016/j.mce.2012.11.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Induction of c-Jun and c-Fos, partners that comprise the AP1 transcription factor, is critical for GnRH regulation of FSHβ gene expression. The signaling pathways that are necessary for regulation of AP1 in the gonadotrope cell are not known. Here, we investigate the mechanism of c-Jun induction by GnRH, the sole regulator of c-Jun in the gonadotrope. We identify that GnRH phosphorylates ATF2 via p38 and JNK, the same pathways responsible for GnRH induction of c-Jun. Upon phosphorylation, ATF2 binds the CRE element within the c-Jun proximal promoter and interacts with NFY. Functional ATF2 is necessary for both GnRH induction of c-Jun and FSHβ. Taken together, these studies elucidate the specificity of c-Jun induction by GnRH in the gonadotrope by demonstrating GnRH activation of the p38 and JNK signaling pathways that lead to phosphorylation of ATF2, providing critical insight into GnRH regulation of its target gene, the gonadotropin subunit FSHβ.
Collapse
Affiliation(s)
- Lacey L Lindaman
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, CA 92093-0674, USA.
| | | | | | | | | |
Collapse
|
12
|
Reddy GR, Xie C, Lindaman LL, Coss D. GnRH increases c-Fos half-life contributing to higher FSHβ induction. Mol Endocrinol 2012; 27:253-65. [PMID: 23275456 DOI: 10.1210/me.2012-1168] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
GnRH is a potent hypothalamic regulator of gonadotropin hormones, LH and FSH, which are both expressed within the pituitary gonadotrope and are necessary for the stimulation of gametogenesis and steroidogenesis in the gonads. Differential regulation of LH and FSH, which is essential for reproductive fitness, is achieved, in part, through the varying of GnRH pulse frequency. However, the mechanism controlling the increase in FSH during the periods of low GnRH has not been elucidated. Here, we uncover another level of regulation by GnRH that contributes to differential expression of the gonadotropins and may play an important role for the generation of the secondary rise of FSH that stimulates folliculogenesis. GnRH stimulates LHβ and FSHβ subunit transcription via induction of the immediate early genes, Egr1 and c-Fos, respectively. Here, we determined that GnRH induces rapidly both Egr1 and c-Fos, but specifically decreases the rate of c-Fos degradation. In particular, GnRH modulates the rate of c-Fos protein turnover by inducing c-Fos phosphorylation through the ERK1/2 pathway. This extends the half-life of c-Fos, which is normally rapidly degraded. Confirming the role of phosphorylation in promoting increased protein activity, we show that a c-Fos mutant that cannot be phosphorylated by GnRH induces lower expression of the FHSβ promoter than wild-type c-Fos. Our studies expand upon the role of GnRH in the regulation of gonadotropin gene expression by highlighting the role of c-Fos posttranslational modification that may cause higher levels of FSH during the time of low GnRH pulse frequency to stimulate follicular growth.
Collapse
Affiliation(s)
- Gaddameedi R Reddy
- Department of Reproductive Medicine, University of California San Diego, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
13
|
Arriola DJ, Mayo SL, Skarra DV, Benson CA, Thackray VG. FOXO1 transcription factor inhibits luteinizing hormone β gene expression in pituitary gonadotrope cells. J Biol Chem 2012; 287:33424-35. [PMID: 22865884 DOI: 10.1074/jbc.m112.362103] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synthesis of luteinizing hormone (LH) is tightly controlled by a complex network of hormonal signaling pathways that can be modulated by metabolic cues, such as insulin. One group of candidate genes that may be regulated by insulin signaling in pituitary gonadotrope cells is the FOXO subfamily of forkhead transcription factors. In this study we investigated whether FOXO1 is expressed in gonadotropes and if it can modulate LH β-subunit (Lhb) gene expression. We demonstrated that FOXO1 is expressed in murine gonadotrope cells and that insulin signaling increased FOXO1 phosphorylation and cytoplasmic localization in a PI3K-dependent manner. We also showed that FOXO1 repressed basal transcription and gonadotropin-releasing hormone (GnRH) induction of both the murine and human LHB genes in LβT2 cells, suggesting that FOXO1 regulation of LHB transcription may be conserved between rodents and humans. Although we did not detect FOXO1 binding to the proximal Lhb promoter, the FOXO1 DNA binding domain was necessary for the suppression, suggesting that FOXO1 exerts its effect through protein-protein interactions with transcription factors/cofactors required for Lhb gene expression. FOXO1 repression mapped to the proximal Lhb promoter containing steroidogenic factor 1 (SF1), pituitary homeobox 1 (PTX1), and early growth response protein 1 (EGR1) binding elements. Additionally, FOXO1 blocked induction of the Lhb promoter with overexpressed SF1, PTX1, and EGR1, indicating that FOXO1 repression occurs via these transcription factors but not through regulation of their promoters. In summary, we demonstrate that FOXO1 phosphorylation and cellular localization is regulated by insulin signaling in gonadotropes and that FOXO1 inhibits Lhb transcription. Our study also suggests that FOXO1 may play an important role in controlling LH levels in response to metabolic cues.
Collapse
Affiliation(s)
- David J Arriola
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, California 92093, USA
| | | | | | | | | |
Collapse
|
14
|
Ghochani Y, Saini JK, Mellon PL, Thackray VG. FOXL2 is involved in the synergy between activin and progestins on the follicle-stimulating hormone β-subunit promoter. Endocrinology 2012; 153:2023-33. [PMID: 22294749 PMCID: PMC3320250 DOI: 10.1210/en.2011-1763] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Differential regulation of gonadotropin hormone production in the pituitary is critical for fertility. Activin and progesterone signaling in gonadotrope cells is important for Fshb gene expression. Previously, we reported that synergy between activin and progestins required the binding of SMAD proteins and the progesterone receptor (PR) to the murine Fshb promoter. In this study, we demonstrate that the FOXL2 transcription factor is also necessary for the full synergistic response between activin and progestins. We show that this synergy occurs in a species-specific manner and that multiple elements in the Fshb promoter that bind forkhead box L2 (FOXL2), SMA/mothers against decapentaplegic homologs (SMAD), and PR are required. Furthermore, we demonstrate that FOXL2 can physically interact with PR and SMAD3. Thus, it is likely that protein-protein interactions among FOXL2, SMAD, and PR recruited to the Fshb promoter play a key role in facilitating Fshb transcription before the secondary FSH surge in rodents.
Collapse
Affiliation(s)
- Yasmin Ghochani
- Department of Reproductive Medicine and the Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
| | | | | | | |
Collapse
|
15
|
Chauvin TR, Herndon MK, Nilson JH. Cold-shock-domain protein A (CSDA) contributes posttranscriptionally to gonadotropin-releasing hormone-regulated expression of Egr1 and indirectly to Lhb. Biol Reprod 2012; 86:53. [PMID: 22053098 DOI: 10.1095/biolreprod.111.093658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Gonadotropin-releasing hormone (GnRH), a hypothalamic neurohormone, regulates transcription of Lhb in gonadotrophs indirectly through transient induction and accumulation of EGR1, a zinc finger transcription factor. AlphaT3 and LbetaT2 cell lines model gonadotrophs at two distinct stages of development, prenatal and postnatal expression of Lhb. Although GnRH induces EGR1 in both cell lines, the levels of the DNA-binding protein are lower and disappear more quickly in alphaT3 than in LbetaT2 cells. Herein we show that overexpression of Egr1 in alphaT3 cells rescues activity of a transfected LHB promoter-reporter, suggesting that its transcription is dependent on EGR1 crossing a critical concentration threshold. We also show that Csda, a gene that encodes an RNA-binding protein and is a member of the cold-shock-domain (CSD) family, is expressed at higher levels in LbetaT2 compared to alphaT3 cells. Transient expression studies indicate that at least one Csd element, residing in the 3' untranslated region of Egr1 mRNA, increases activity of a chimeric pGL3 luciferase reporter vector in LbetaT2 cells. Additional experiments indicate that CSDA physically interacts with Egr1 mRNA. Furthermore, siRNA-mediated reduction of endogenous Csda mRNA attenuates GnRH regulation of a transiently transfected LHB reporter vector. Taken together, these studies suggest that CSDA contributes posttranscriptionally to GnRH-regulated expression of Egr1, thereby enabling the transcription factor to cross a critical concentration threshold necessary for maximal accumulation of Lhb mRNA in response to the neurohormone.
Collapse
Affiliation(s)
- Theodore R Chauvin
- School of Molecular Biosciences, Washington State University, Pullman, 99164-7520, USA
| | | | | |
Collapse
|
16
|
Lirón J, Prando A, Ripoli M, Rogberg-Muñoz A, Posik D, Baldo A, Peral-García P, Giovambattista G. Characterization and validation of bovine Gonadotripin releasing hormone receptor (GNRHR) polymorphisms. Res Vet Sci 2011; 91:391-6. [DOI: 10.1016/j.rvsc.2010.09.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 09/21/2010] [Accepted: 09/26/2010] [Indexed: 11/28/2022]
|
17
|
Corpuz PS, Lindaman LL, Mellon PL, Coss D. FoxL2 Is required for activin induction of the mouse and human follicle-stimulating hormone beta-subunit genes. Mol Endocrinol 2010; 24:1037-51. [PMID: 20233786 DOI: 10.1210/me.2009-0425] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Activin is a major physiological regulator of FSH. We identify FoxL2 as a critical component in activin induction of FSHbeta, both for the mouse gene, induction of which is Sma- and Mad-related protein (Smad) dependent, and for the human gene that is Smad independent. FoxL2 has been shown to regulate gonadotrope gene expression (GnRH receptor, alpha-glycoprotein subunit, porcine FSHbeta, and follistatin), but the mechanisms of action are not well understood. We identify novel sites required for activin action in both the mouse and human FSHbeta promoters, some of which bind FoxL2, and show that the FoxL2-binding element encompasses a larger region (12 bp) than the previously identified forkhead-binding consensus (7 bp). Remarkably, although required for activin induction, FoxL2 sites neither contribute to basal FSHbeta promoter activity nor confer activin response to a heterologous promoter; thus, they are neither classical activin-response elements nor is their role solely to recruit Smads to the promoter. FoxL2 overexpression can potentiate activin induction in gonadotropes and can confer activin responsiveness to FSHbeta in heterologous cells where this promoter is normally refractory to activin induction. Although Smad3 requires the presence of FoxL2 sites to induce mouse FSHbeta, even through its consensus Smad-binding element; the human promoter, which is induced by activin independently of Smad3, also requires FoxL2 sites for its induction by activin; thus the actions of FoxL2 are not exclusively through interactions with the Smad pathway. Thus, FoxL2 plays a key role in activin induction of the FSHbeta gene, by binding to sites conserved across multiple species.
Collapse
Affiliation(s)
- Patrick S Corpuz
- Department of Reproductive Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
18
|
Walker JJ, Terry JR, Lightman SL. Origin of ultradian pulsatility in the hypothalamic-pituitary-adrenal axis. Proc Biol Sci 2010; 277:1627-33. [PMID: 20129987 PMCID: PMC2871854 DOI: 10.1098/rspb.2009.2148] [Citation(s) in RCA: 149] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The hypothalamic–pituitary–adrenal (HPA) axis is a neuroendocrine system that regulates the circulating levels of vital glucocorticoid hormones. The activity of the HPA axis is characterized not only by a classic circadian rhythm, but also by an ultradian pattern of discrete pulsatile release of glucocorticoids. A number of psychiatric and metabolic diseases are associated with changes in glucocorticoid pulsatility, and it is now clear that glucocorticoid responsive genes respond to these rapid fluctuations in a biologically meaningful way. Theoretical modelling has enabled us to identify and explore potential mechanisms underlying the ultradian activity in this axis, which to date have not been identified successfully. We demonstrate that the combination of delay with feed-forward and feedback loops in the pituitary–adrenal system is sufficient to give rise to ultradian pulsatility in the absence of an ultradian source from a supra-pituitary site. Moreover, our model enables us to predict the different patterns of glucocorticoid release mediated by changes in hypophysial-portal corticotrophin-releasing hormone levels, with results that parallel our experimental in vivo data.
Collapse
Affiliation(s)
- Jamie J Walker
- Department of Engineering Mathematics, University of Bristol, Bristol, UK.
| | | | | |
Collapse
|
19
|
Thackray VG, Mellon PL, Coss D. Hormones in synergy: regulation of the pituitary gonadotropin genes. Mol Cell Endocrinol 2010; 314:192-203. [PMID: 19747958 PMCID: PMC2815122 DOI: 10.1016/j.mce.2009.09.003] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 09/02/2009] [Accepted: 09/02/2009] [Indexed: 11/23/2022]
Abstract
The precise interplay of hormonal influences that governs gonadotropin hormone production by the pituitary includes endocrine, paracrine and autocrine actions of hypothalamic gonadotropin-releasing hormone (GnRH), activin and steroids. However, most studies of hormonal regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary gonadotrope have been limited to analyses of the isolated actions of individual hormones. LHbeta and FSHbeta subunits have distinct patterns of expression during the menstrual/estrous cycle as a result of the integration of activin, GnRH, and steroid hormone action. In this review, we focus on studies that delineate the interplay among these hormones in the regulation of LHbeta and FSHbeta gene expression in gonadotrope cells and discuss how signaling cross-talk contributes to differential expression. We also discuss how recent technological advances will help identify additional factors involved in the differential hormonal regulation of LH and FSH.
Collapse
Affiliation(s)
| | | | - Djurdjica Coss
- To whom the correspondence should be addressed: Djurdjica Coss, Department of Reproductive Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0674, Phone: (858) 534-1762, Fax: (858) 534-1438,
| |
Collapse
|
20
|
Lim S, Pnueli L, Tan JH, Naor Z, Rajagopal G, Melamed P. Negative feedback governs gonadotrope frequency-decoding of gonadotropin releasing hormone pulse-frequency. PLoS One 2009; 4:e7244. [PMID: 19787048 PMCID: PMC2746289 DOI: 10.1371/journal.pone.0007244] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 08/19/2009] [Indexed: 11/19/2022] Open
Abstract
The synthesis of the gonadotropin subunits is directed by pulsatile gonadotropin-releasing hormone (GnRH) from the hypothalamus, with the frequency of GnRH pulses governing the differential expression of the common alpha-subunit, luteinizing hormone beta-subunit (LHbeta) and follicle-stimulating hormone beta-subunit (FSHbeta). Three mitogen-activated protein kinases, (MAPKs), ERK1/2, JNK and p38, contribute uniquely and combinatorially to the expression of each of these subunit genes. In this study, using both experimental and computational methods, we found that dual specificity phosphatase regulation of the activity of the three MAPKs through negative feedback is required, and forms the basis for decoding the frequency of pulsatile GnRH. A fourth MAPK, ERK5, was shown also to be activated by GnRH. ERK5 was found to stimulate FSHbeta promoter activity and to increase FSHbeta mRNA levels, as well as enhancing its preference for low GnRH pulse frequencies. The latter is achieved through boosting the ultrasensitive behavior of FSHbeta gene expression by increasing the number of MAPK dependencies, and through modulating the feedforward effects of JNK activation on the GnRH receptor (GnRH-R). Our findings contribute to understanding the role of changing GnRH pulse-frequency in controlling transcription of the pituitary gonadotropins, which comprises a crucial aspect in regulating reproduction. Pulsatile stimuli and oscillating signals are integral to many biological processes, and elucidation of the mechanisms through which the pulsatility is decoded explains how the same stimulant can lead to various outcomes in a single cell.
Collapse
Affiliation(s)
- Stefan Lim
- National University of Singapore, Graduate School for Integrative Sciences and Engineering, Centre for Life Sciences, Singapore, Republic of Singapore
| | - Lilach Pnueli
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Jing Hui Tan
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Zvi Naor
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
| | - Gunaretnam Rajagopal
- The Cancer Institute of New Jersey, New Brunswick, New Jersey, United States of America
| | - Philippa Melamed
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| |
Collapse
|
21
|
Meethal SV, Liu T, Chan HW, Ginsburg E, Wilson AC, Gray DN, Bowen RL, Vonderhaar BK, Atwood CS. Identification of a regulatory loop for the synthesis of neurosteroids: a steroidogenic acute regulatory protein-dependent mechanism involving hypothalamic-pituitary-gonadal axis receptors. J Neurochem 2009; 110:1014-27. [PMID: 19493163 DOI: 10.1111/j.1471-4159.2009.06192.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Brain sex steroids are derived from both peripheral (primarily gonadal) and local (neurosteroids) sources and are crucial for neurogenesis, neural differentiation and neural function. The mechanism(s) regulating the production of neurosteroids is not understood. To determine whether hypothalamic-pituitary-gonadal axis components previously detected in the extra-hypothalamic brain comprise a feedback loop to regulate neuro-sex steroid (NSS) production, we assessed dynamic changes in expression patterns of steroidogenic acute regulatory (StAR) protein, a key regulator of steroidogenesis, and key hypothalamic-pituitary-gonadal endocrine receptors, by modulating peripheral sex hormone levels in female mice. Ovariectomy (OVX; high serum gonadotropins, low serum sex steroids) had a differential effect on StAR protein levels in the extrahypothalamic brain; increasing the 30- and 32-kDa variants but decreasing the 37-kDa variant and is indicative of cholesterol transport into mitochondria for steroidogenesis. Treatment of OVX animals with E(2), P(4), or E(2) + P(4) for 3 days, which decreases OVX-induced increases in GnRH/gonadotropin production, reversed this pattern. Suppression of gonadotropin levels in OVX mice using the GnRH agonist leuprolide acetate inhibited the processing of the 37-kDa StAR protein into the 30-kDa StAR protein, confirming that the differential processing of brain StAR protein is regulated by gonadotropins. OVX dramatically suppressed extra-hypothalamic brain gonadotropin-releasing hormone 1 receptor expression, and was further suppressed in E(2)- or P(4)-treated OVX mice. Together, these data indicate the existence of endocrine and autocrine/paracrine feedback loops that regulate NSS synthesis. Further delineation of these feedback loops that regulate NSS production will aid in developing therapies to maintain brain sex steroid levels and cognition.
Collapse
Affiliation(s)
- Sivan Vadakkadath Meethal
- Department of Medicine, University of Wisconsin and Geriatric Research, Education and Clinical Center, Veterans Administration Hospital, Madison, Wisconsin 53705, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Thackray VG, Hunnicutt JL, Memon AK, Ghochani Y, Mellon PL. Progesterone Inhibits basal and gonadotropin-releasing hormone induction of luteinizing hormone beta-subunit gene expression. Endocrinology 2009; 150:2395-403. [PMID: 19106225 PMCID: PMC2671912 DOI: 10.1210/en.2008-1027] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
LH and FSH play critical roles in mammalian reproduction by mediating steroidogenesis and gametogenesis in the gonad. Gonadal steroid hormone feedback to the hypothalamus and pituitary influences production of the gonadotropins. We previously demonstrated that progesterone differentially regulates the expression of the LH and FSH beta-subunits at the level of the gonadotrope: FSHbeta transcription is induced, whereas LHbeta is repressed. In this study, we investigated the mechanism of progesterone repression of LHbeta gene expression using immortalized gonadotrope-derived LbetaT2 cells. The progesterone suppression of both basal and GnRH-induced LHbeta gene expression occurs in a hormone- and receptor-dependent manner. Chromatin immunoprecipitation demonstrates that the hormone-bound progesterone receptor (PR) is recruited to the endogenous mouse LHbeta promoter. In addition, suppression requires both the amino-terminal and DNA-binding regions of PR. Furthermore, progesterone suppression does not require direct PR binding to the promoter, and, thus, PR is likely recruited to the promoter via indirect binding through other transcription factors. These data demonstrate that the molecular mechanism for progesterone action on the LHbeta promoter is distinct from FSHbeta, which involves direct PR binding to the promoter to produce activation. It also differs from androgen repression of LHbeta gene expression in that, rather than Sp1 or steroidogenic factor-1 elements, it requires elements within -300/-250 and -200/-150 that also contribute to basal expression of the LHbeta promoter. Altogether, our data indicate that progesterone feedback at the level of the pituitary gonadotrope is likely to play a key role in differential production of the gonadotropin genes.
Collapse
Affiliation(s)
- Varykina G Thackray
- Department of Reproductive Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | | | | | | | | |
Collapse
|
23
|
Thackray VG, Mellon PL. Synergistic induction of follicle-stimulating hormone beta-subunit gene expression by gonadal steroid hormone receptors and Smad proteins. Endocrinology 2008; 149:1091-102. [PMID: 18079204 PMCID: PMC2275352 DOI: 10.1210/en.2007-1498] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
LH and FSH play crucial roles in mammalian reproduction by mediating steroidogenesis and gametogenesis. Gonadal steroid hormones influence gonadotropin production via feedback to the hypothalamus and pituitary. We previously demonstrated that progesterone and testosterone can stimulate expression of the FSH beta-subunit gene in immortalized gonadotrope-derived LbetaT2 cells. Herein, we investigate how these gonadal steroids modulate activin signaling in the gonadotrope. Cotreatment of LbetaT2 cells or mouse primary pituitary cells with steroids and activin results in a synergistic induction of FSHbeta gene expression. This synergy decreases when DNA-binding mutations are introduced into the steroid receptors or when mutations that reduce steroid hormone responsiveness are introduced into the FSHbeta promoter, indicating that synergy requires direct DNA binding of the steroid receptors. Furthermore, classical activin signaling via Smad proteins is necessary for this synergy. In addition, these steroid receptors physically interact with Smads and are sufficient for the synergism to occur on the FSHbeta promoter. Disruption of Smad binding to the promoter with a Smad protein lacking the DNA-binding domain or an FSHbeta promoter containing mutated activin-response elements prevents the synergistic enhancement of FSHbeta transcription. Collectively, our data demonstrate that the molecular mechanism for gonadal steroid hormone action on the FSHbeta promoter involves cross-talk between the steroid and activin signaling pathways. They also reveal that this synergism requires binding of both the steroid receptors and Smad proteins to their cognate DNA-binding elements and likely involves a direct protein-protein interaction between the two types of transcription factors.
Collapse
Affiliation(s)
- Varykina G Thackray
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | | |
Collapse
|
24
|
López de Maturana R, Martin B, Millar RP, Brown P, Davidson L, Pawson AJ, Nicol MR, Mason JI, Barran P, Naor Z, Maudsley S. GnRH-mediated DAN production regulates the transcription of the GnRH receptor in gonadotrope cells. Neuromolecular Med 2007; 9:230-48. [PMID: 17914181 DOI: 10.1007/s12017-007-8004-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 11/30/1999] [Accepted: 02/02/2007] [Indexed: 10/23/2022]
Abstract
The primary function of gonadotropin-releasing hormone (GnRH) is the regulation of pituitary gonadotropin hormone gene transcription, biosynthesis and release. These effects are mediated through intracellular mobilization of Ca2+ and activation of PKC isoforms and MAP kinases. We show here that DAN (differential screening-selected gene aberrative in neuroblastoma) which is a secreted bone morphogenic protein (BMP) antagonist belonging to the TGFbeta protein superfamily, is controlled by GnRH in murine gonadotrope cells. Acute GnRH stimulation induced a rapid, 27-fold, elevation of DAN mRNA, accompanied by an approximate 3-fold increase in the amount of mature DAN glycoprotein in the cell cytoplasm and in DAN secretion into the culture medium. Incubation of L beta T2 cells in DAN-containing medium altered the levels of a number of cellular proteins. Two of these were identified as the steroidogenic acute regulatory protein (StAR) and the actin-related protein 2/3 complex subunits 2 (p34-ARC) which are primarily involved in steroidogenesis and cytoskeleton remodelling, respectively. DAN caused an approximate 2-fold specific elevation in the cytoplasmic levels of both these proteins in L beta T2 cells. We further tested the effects of DAN on classical GnRH effects viz. gonadotropin and GnRH receptor gene expression. Co-transfection of L beta T2 cells with DAN and gonadotropin subunit promoter luciferase reporter genes had no effect on GnRH stimulation of alpha GSU and LH beta or on the additive GnRH and activin induction of FSH beta subunit transcription. However, co-transfection of DAN markedly inhibited the synergistic activation of GnRH and activin on GnRH receptor gene expression thus implicating DAN as a novel autocrine/paracrine factor that modulates GnRH function in pituitary gonadotropes.
Collapse
Affiliation(s)
- Rakel López de Maturana
- MRC Human Reproductive Sciences Unit, Centre for Human Reproductive Biology, Edinburgh, EH16 4SB, UK
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Conway-Campbell BL, McKenna MA, Wiles CC, Atkinson HC, de Kloet ER, Lightman SL. Proteasome-dependent down-regulation of activated nuclear hippocampal glucocorticoid receptors determines dynamic responses to corticosterone. Endocrinology 2007; 148:5470-7. [PMID: 17690167 DOI: 10.1210/en.2007-0585] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Timing is a critical factor in neuroendocrinology. Despite this, the temporal aspects of glucocorticoid signaling in the regulation of in vivo targets have been largely overlooked. Here, we present data showing that plasma glucocorticoid levels differ greatly from the constant signal predominantly used in cell culture experiments. Using an automated blood sampling system, we found that under basal conditions in nonstressed rats, corticosterone release occurs in discrete pulses of various amplitudes dependent on the circadian cycle. This basal pattern changes to a prolonged elevated nonpulsatile release in response to stressful stimuli. We have been able to recapitulate these different patterns of corticosterone presentation (short pulse vs. prolonged elevation) in adrenalectomized rats, and show that each pattern results in differential activation of hippocampal glucocorticoid and mineralocorticoid receptors. Finally, we provide evidence for a rapid proteasome-dependent clearance of activated glucocorticoid receptors, but not mineralocorticoid receptors, as a novel mechanism to allow dynamic interaction with rapidly changing physiological and environmental conditions.
Collapse
Affiliation(s)
- Becky L Conway-Campbell
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Dorothy Hodgkins Building, University of Bristol, Bristol, UK.
| | | | | | | | | | | |
Collapse
|
26
|
McGillivray SM, Thackray VG, Coss D, Mellon PL. Activin and glucocorticoids synergistically activate follicle-stimulating hormone beta-subunit gene expression in the immortalized LbetaT2 gonadotrope cell line. Endocrinology 2007; 148:762-73. [PMID: 17082263 PMCID: PMC2932480 DOI: 10.1210/en.2006-0952] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
FSH is produced by the pituitary gonadotrope to regulate gametogenesis. Production of the beta-subunit of FSH is the rate-limiting step in FSH synthesis, and a number of peptide and steroid hormones within the reproductive axis have been found to regulate transcription of the FSH beta-subunit gene. Although both activin and glucocorticoids are notable regulators of FSHbeta by themselves, we find that cotreatment results in a synergistic interaction on the mouse FSHbeta promoter at the level of the gonadotrope using transient transfection of a reporter gene into the LbetaT2 immortalized gonadotrope-derived cell line. This synergistic interaction is specific to FSHbeta, because only additive effects of these two hormones are observed on LH beta-subunit, GnRH receptor, and mouse mammary tumor virus gene expression. Components of both activin and glucocorticoid signaling are found to be necessary for synergy, and there are specific cis elements on the mouse FSHbeta promoter that contribute to the synergistic response as well. We also identify novel activin-responsive regions in the mouse FSHbeta promoter and find that the -120 site can bind Smad2/3 in vitro. In addition, the glucocorticoid receptor and Smad3 are sufficient to confer a striking synergy with glucocorticoids on the mouse FSHbeta promoter. Our studies provide the first evidence of a synergistic interaction between activin and glucocorticoids within the gonadotrope cell and demonstrate that this synergy can occur directly at the level of the mouse FSHbeta promoter.
Collapse
Affiliation(s)
- Shauna M McGillivray
- Department of Reproductive Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
27
|
Thackray VG, McGillivray SM, Mellon PL. Androgens, progestins, and glucocorticoids induce follicle-stimulating hormone beta-subunit gene expression at the level of the gonadotrope. Mol Endocrinol 2006; 20:2062-79. [PMID: 16675544 PMCID: PMC2941439 DOI: 10.1210/me.2005-0316] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
FSH is produced by the pituitary gonadotrope to regulate gametogenesis. Steroid hormones, including androgens, progestins, and glucocorticoids, have all been shown to stimulate expression of the FSHbeta subunit in primary pituitary cells and rodent models. Understanding the molecular mechanisms of steroid induction of FSHbeta has been difficult due to the heterogeneity of the anterior pituitary. Immortalized LbetaT2 cells are a model of a mature gonadotrope cell and express the endogenous steroid receptor for each of the three hormones. Transient transfection of each receptor, along with ligand treatment, stimulates the mouse FSHbeta promoter, but induction is severely diminished using receptors that lack the ability to bind DNA, indicating that induction is likely through direct DNA binding. All three steroid hormones act within the first 500 bp of the FSHbeta promoter where six putative hormone response elements exist. The -381 site is critical for FSHbeta induction by all three steroid hormones, whereas the -197 and -139 sites contribute to maximal induction. Interestingly, the -273 and -230 sites are also necessary for androgen and progestin induction of FSHbeta, but not for glucocorticoid induction. Additionally, we find that all three receptors bind the endogenous FSHbeta promoter, in vivo, and specifically bind the -381 site in vitro, suggesting that the binding of the receptors to this element is critical for the induction of FSHbeta by these 3-keto steroid hormones. Our data indicate that androgens, glucocorticoids, and progestins act via their receptors to directly activate FSHbeta gene expression in the pituitary gonadotrope.
Collapse
Affiliation(s)
- Varykina G Thackray
- Department of Reproductive Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
| | | | | |
Collapse
|
28
|
Ferris HA, Shupnik MA. Mechanisms for pulsatile regulation of the gonadotropin subunit genes by GNRH1. Biol Reprod 2006; 74:993-8. [PMID: 16481592 DOI: 10.1095/biolreprod.105.049049] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The frequency of gonadotropin-releasing hormone (GNRH1, or GnRH) pulses secreted from the hypothalamus determine the ratios of the gonadotropin subunit genes luteinizing hormone beta (Lhb), follicle-stimulating hormone beta (Fshb) and the common alpha-glycoprotein subunit gene (Cga) transcribed in the anterior pituitaries of mammals. Fshb is preferentially transcribed at slower GNRH1 pulse frequencies, whereas Lhb and Cga are preferentially transcribed at more rapid pulse frequencies. Producing the gonadotropins in the correct proportions is critical for normal fertility. Currently, there is no definitive explanation for how GNRH1 pulses differentially activate gonadotropin subunit gene transcription. Several pathways may contribute to this regulation. For example, GNRH1-regulated GNRH1-receptor concentrations may lead to variable signaling pathway activation. Several signaling pathways are activated by GnRH, including mitogen-activated protein kinase, protein kinase C, calcium influx, and calcium-calmodulin kinase, and these may be preferentially regulated under certain conditions. In addition, some signaling proteins feed back to downregulate their own levels. Other arms of gonadotroph signaling appear to be regulated by synthesis, modification, and degradation of either transcription factors or regulatory proteins. Finally, the dynamic binding of proteins to the chromatin, and how that might be regulated by chromatin-modifying proteins, is addressed. Oscillations in expression, modification, and chromatin binding of the proteins involved in gonadotropin gene expression are likely a link between GNRH1 pulsatility and differential gonadotropin transcription.
Collapse
MESH Headings
- Animals
- Chromatin/physiology
- Follicle Stimulating Hormone, beta Subunit/genetics
- Follicle Stimulating Hormone, beta Subunit/metabolism
- Follicle Stimulating Hormone, beta Subunit/physiology
- Gene Expression Regulation/physiology
- Glycoprotein Hormones, alpha Subunit/genetics
- Glycoprotein Hormones, alpha Subunit/metabolism
- Glycoprotein Hormones, alpha Subunit/physiology
- Gonadotropin-Releasing Hormone/physiology
- Gonadotropins/genetics
- Gonadotropins/metabolism
- Gonadotropins/physiology
- Gonads/physiology
- Humans
- Hypothalamo-Hypophyseal System/physiology
- Hypothalamus/metabolism
- Luteinizing Hormone, beta Subunit/genetics
- Luteinizing Hormone, beta Subunit/metabolism
- Luteinizing Hormone, beta Subunit/physiology
- Protein Processing, Post-Translational/genetics
- Protein Processing, Post-Translational/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Transcription, Genetic/genetics
- Transcription, Genetic/physiology
Collapse
Affiliation(s)
- Heather A Ferris
- Department of Physiology, University of Virginia, Charlottesville, Virginia 22908, USA
| | | |
Collapse
|
29
|
Coss D, Thackray VG, Deng CX, Mellon PL. Activin regulates luteinizing hormone beta-subunit gene expression through Smad-binding and homeobox elements. Mol Endocrinol 2005; 19:2610-23. [PMID: 15961509 PMCID: PMC2932483 DOI: 10.1210/me.2005-0047] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
LH beta-subunit (LHbeta), which is essential for ovulation and reproductive fitness, is synthesized specifically in pituitary gonadotropes. In this study, we show that LHbeta gene expression is induced by activin in mouse primary pituitary cells if the cells are treated within 24 h after dispersion in culture. Furthermore, male mice deficient in Smad3, and therefore in activin signaling, have lower expression of both LHbeta and FSHbeta mRNAs compared with their wild-type littermates. Using the LbetaT2 immortalized mouse gonadotrope cell line that endogenously expresses LH, we identify specific elements in the regulatory region of the rat LHbeta gene necessary for its induction by activin. Activin responsiveness is conferred by a promoter-proximal region located -121/-86 from the transcriptional start site. Maximal LHbeta induction by activin requires a homeobox element (HB) and a 5'-early growth response (Egr) site found in this region of the promoter. Juxtaposed to the HB are three Smad-binding elements (SBEs), which are essential for LHbeta induction. Interestingly, two of the SBEs are also critical for basal expression of the LHbeta gene. We demonstrate that Smad proteins are necessary and sufficient for activin induction of the LHbeta gene. Furthermore, Smad proteins can bind one of the identified SBEs. In addition to binding this SBE, Smad proteins interact with pituitary homeobox 1 (Ptx-1) and orthodenticle homeobox 1 (Otx-1), which can bind the HB located close to the Smad-binding site. Thus, activin induction of LHbeta gene expression requires a combination of several transcription factors, both basal and activin induced, as well as cooperation between multiple DNA elements.
Collapse
Affiliation(s)
- Djurdjica Coss
- Department of Reproductive Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
30
|
Ciccone NA, Dunn IC, Boswell T, Tsutsui K, Ubuka T, Ukena K, Sharp PJ. Gonadotrophin inhibitory hormone depresses gonadotrophin alpha and follicle-stimulating hormone beta subunit expression in the pituitary of the domestic chicken. J Neuroendocrinol 2004; 16:999-1006. [PMID: 15667455 DOI: 10.1111/j.1365-2826.2005.01260.x] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Studies performed in vitro suggest that a novel 12 amino acid RF amide peptide, isolated from the quail hypothalamus, is a gonadotrophin inhibitory hormone (GnIH). The aim of the present study was to investigate this hypothesis in the domestic chicken. Injections of GnIH into nest-deprived incubating hens failed to depress the concentration of plasma luteinizing hormone (LH). Addition of GnIH to short-term (120 min) cultures of diced pituitary glands from adult cockerels depressed follicle-stimulating hormone (FSH) and LH release and depressed common alpha and FSHbeta gonadotrophin subunit mRNAs, with no effect on LHbeta subunit mRNA. Hypothalamic GnIH mRNA was higher in incubating (out-of-lay) than in laying hens, but there was no significant difference in the amount of hypothalamic GnIH mRNA in out-of-lay and laying broiler breeder hens at the end of a laying year. It is concluded that avian GnIH may play a role in controlling gonadotrophin synthesis and associated constitutive release in the domestic chicken.
Collapse
Affiliation(s)
- N A Ciccone
- Division of Genetics and Genomics, Roslin Institute, Midlothian, UK.
| | | | | | | | | | | | | |
Collapse
|
31
|
Jorgensen JS, Quirk CC, Nilson JH. Multiple and overlapping combinatorial codes orchestrate hormonal responsiveness and dictate cell-specific expression of the genes encoding luteinizing hormone. Endocr Rev 2004; 25:521-42. [PMID: 15294880 DOI: 10.1210/er.2003-0029] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Normal reproductive function in mammals requires precise control of LH synthesis and secretion by gonadotropes of the anterior pituitary. Synthesis of LH requires expression of two genes [alpha-glycoprotein subunit (alphaGSU) and LHbeta] located on different chromosomes. Hormones from the hypothalamus and gonads modulate transcription of both genes as well as secretion of the biologically active LH heterodimer. In males and females, the transcriptional tone of the genes encoding alphaGSU and LHbeta reflects dynamic integration of a positive signal provided by GnRH from hypothalamic neurons and negative signals emanating from gonadal steroids. Although alphaGSU and LHbeta genes respond transcriptionally in the same manner to changes in hormonal input, different combinations of regulatory elements orchestrate their response. These hormone-responsive regulatory elements are also integral members of much larger combinatorial codes responsible for targeting expression of alphaGSU and LHbeta genes to gonadotropes. In this review, we will profile the genomic landscape of the promoter-regulatory region of both genes, depicting elements and factors that contribute to gonadotrope-specific expression and hormonal regulation. Within this context, we will highlight the different combinatorial codes that control transcriptional responses, particularly those that mediate the opposing effects of GnRH and one of the sex steroids, androgens. We will use this framework to suggest that GnRH and androgens attain the same transcriptional endpoint through combinatorial codes unique to alphaGSU and LHbeta. This parallelism permits the dynamic and coordinate regulation of two genes that encode a single hormone.
Collapse
Affiliation(s)
- Joan S Jorgensen
- Department of Veterinary Biosciences, University of Illinois, Urbana 61802, USA
| | | | | |
Collapse
|
32
|
Norwitz ER, Xu S, Xu J, Spiryda LB, Park JS, Jeong KH, McGee EA, Kaiser UB. Direct binding of AP-1 (Fos/Jun) proteins to a SMAD binding element facilitates both gonadotropin-releasing hormone (GnRH)- and activin-mediated transcriptional activation of the mouse GnRH receptor gene. J Biol Chem 2002; 277:37469-78. [PMID: 12145309 DOI: 10.1074/jbc.m206571200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The response of pituitary gonadotropes to gonadotropin-releasing hormone (GnRH) correlates directly with the concentration of GnRH receptors (GnRHR) on the cell surface, which is mediated in part at the level of gene expression. Several factors are known to affect expression of the mouse GnRHR (mGnRHR) gene, including GnRH and activin. We have previously shown that activin augments GnRH-mediated transcriptional activation of mGnRHR gene, and that region -387/-308 appears to be necessary to mediate this effect. This region contains two overlapping cis-regulatory elements of interest: GnRHR activating sequence (GRAS) and a putative SMAD-binding element (SBE). This study investigates the role of these elements and their cognate transcription factors in transactivation of the mGnRHR gene. Transfection studies confirm the presence of GnRH- and activin-response elements within -387/-308 of mGnRHR gene promoter. Competition electrophoretic mobility shift assay experiments using -335/-312 as probe and alphaT3-1 nuclear extract or SMAD, Jun, and Fos proteins demonstrate direct binding of AP-1 (Fos/Jun) protein complexes to -327/-322 and SMAD proteins to -329/-328. Further transfection studies using mutant constructs of these cis-regulatory elements confirm that both are functionally important. These data define a novel cis-regulatory element comprised of an overlapping SBE and newly characterized non-consensus AP-1 binding sequence that integrates the stimulatory transcriptional effects of both GnRH and activin on the mGnRHR gene.
Collapse
Affiliation(s)
- Errol R Norwitz
- Department of Obstetrics, Gynecology and Reproductive Biology, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Norwitz ER, Xu S, Jeong KH, Bédécarrats GY, Winebrenner LD, Chin WW, Kaiser UB. Activin A augments GnRH-mediated transcriptional activation of the mouse GnRH receptor gene. Endocrinology 2002; 143:985-97. [PMID: 11861523 DOI: 10.1210/endo.143.3.8663] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The response of pituitary gonadotropes to GnRH correlates directly with the concentration of GnRH receptors (GnRHRs) on the cell surface, which is mediated in part at the level of GnRHR gene expression. We have previously localized GnRH responsiveness in the mouse GnRHR (mGnRHR) gene promoter to two elements: activating protein-1 and sequence underlying responsiveness to GnRH-1. This study was designed to investigate potential synergy between GnRH and activin A in transcriptional activation of the mGnRHR gene. In functional transfection studies using alphaT3-1 cells, GnRH agonist stimulation of the mGnRHR gene promoter (-765/+62) resulted in a 10.9-fold increase in activity, which was further increased 2-fold (to 21.3-fold) following activin pretreatment. Activin pretreatment alone had no effect. Deletion of region -387/-308 or mutation of a putative SMAD-binding element at -331/-324 (5'-GTCTAG[T]C-3') abrogated the augmented response to GnRH in the presence of activin but not the response to GnRH alone. Overexpression of SMAD2 and SMAD3 along with SMAD4 increased transcriptional activity of the mGnRHR gene, which was further increased by GnRH agonist stimulation. These data demonstrate that activin augments GnRH-mediated transcriptional activation of the mGnRHR gene and suggest that this effect may be mediated through SMAD transcription factors.
Collapse
Affiliation(s)
- Errol R Norwitz
- Department of Obstetrics, Gynecology, and Reproductive Biology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
| | | | | | | | | | | | | |
Collapse
|
34
|
Park JY, Park JH, Park HJ, Lee JY, Lee YI, Lee K, Chun SY. Stage-dependent regulation of ovarian pituitary adenylate cyclase-activating polypeptide mRNA levels by GnRH in cultured rat granulosa cells. Endocrinology 2001; 142:3828-35. [PMID: 11517159 DOI: 10.1210/endo.142.9.8384] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The present study was designed to test whether GnRH regulates pituitary adenylate cyclase-activating polypeptide mRNA levels in a stage-dependent manner during follicle development in the rat ovary. The granulosa cells of preovulatory and immature follicles obtained from PMSG- and estrogen-treated rats, respectively, were cultured in serum-free conditions in the presence of various hormones. GnRH receptor mRNA expression was detected in both preovulatory and immature granulosa cells and was down-regulated by gonadotropins. Treatment of preovulatory granulosa cells with GnRH agonist stimulated pituitary adenylate cyclase-activating polypeptide mRNA levels in a dose-dependent manner. In situ hybridization analysis of cultured preovulatory follicles revealed that GnRH-induced pituitary adenylate cyclase- activating polypeptide signals were detected in granulosa cells, but not thecal cells. In immature granulosa cells, cotreatment with GnRH agonist suppressed FSH-stimulated pituitary adenylate cyclase-activating polypeptide mRNA levels in a dose-dependent manner, whereas treatment with GnRH alone had no effect. Furthermore, treatment with GnRH antagonist inhibited LH-induced pituitary adenylate cyclase-activating polypeptide gene expression in preovulatory granulosa cells, whereas it stimulated FSH-induced pituitary adenylate cyclase-activating polypeptide gene expression in immature granulosa cells. Interestingly, GnRH-stimulated pituitary adenylate cyclase-activating polypeptide mRNA levels in preovulatory granulosa cells was inhibited by arachidonyltri fluoromethyl ketone, an inhibitor of phospholipase A(2), but not by an inhibitor of protein kinase A or C. Lastly, treatment of preovulatory follicles with pituitary adenylate cyclase-activating polypeptide antagonist suppressed GnRH-stimulated progesterone production during 6--9 h of culture. Taken together, these results demonstrate the stage-dependent regulation of pituitary adenylate cyclase-activating polypeptide mRNA levels by GnRH, the stimulatory and inhibitory effect in granulosa cells of preovulatory and immature follicles, respectively.
Collapse
Affiliation(s)
- J Y Park
- Hormone Research Center, Chonnam National University, Kwangju 500-757, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
35
|
Cheon M, Park D, Park Y, Kam K, Park SD, Ryu K. Homologous upregulation of gonadotropin-releasing hormone receptor mRNA occurs through transcriptional activation rather than modulation of mRNA stability. Endocrine 2000; 13:47-53. [PMID: 11051046 DOI: 10.1385/endo:13:1:47] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2000] [Revised: 05/01/2000] [Accepted: 05/07/2000] [Indexed: 11/11/2022]
Abstract
In a previous study, we showed that even continuous application of gonadotropin-releasing hormone (GnRH) could increase the steady-state levels of GnRH receptor (GnRH-R) mRNA if treated for a relatively short period (6 h). Therefore, in the present study we examined whether GnRH-induced increment of GnRH-R mRNA is owing to stabilization of the preexisting GnRH-R mRNA or new synthesis of GnRH-R mRNA or both. Initially, to examine the effect on new RNA synthesis, the transcription inhibitor, actinomycin D (2 microM), was added to primary cultured rat anterior pituitary cells. In the presence of transcription inhibitor, GnRH-induced augmentation of GnRH-R mRNA levels was completely abolished. This result indicates that homologous upregulation of GnRH-R mRNA expression occurs at least through new RNA synthesis of GnRH-R gene. We further assessed the effects of GnRH on the turnover rate of GnRH-R mRNA using actinomycin D (2 microM). The basal half-life of GnRH-R mRNA was estimated to be approx 21 h. The application of GnRH tended to slightly suppress the basal turnover rate of GnRH; however, there was no statistically significant difference, compared with the group treated with actinomycin D alone. Collectively, our results suggest that the homologous upregulation of GnRH-R mRNA may occur through transcriptional activation of GnRH-R gene rather than enhancement of GnRH-R mRNA stability, although we did not examine the transcription rate of GnRH-R gene.
Collapse
Affiliation(s)
- M Cheon
- Endocrine Laboratory, College of Medicine, Yonsei University, Seoul, South Korea
| | | | | | | | | | | |
Collapse
|
36
|
Kato Y, Tomizawa K, Kato T. Multiple binding sites for nuclear proteins of the anterior pituitary are located in the 5'-flanking region of the porcine follicle-stimulating hormone (FSH) beta-subunit gene. Mol Cell Endocrinol 1999; 158:69-78. [PMID: 10630407 DOI: 10.1016/s0303-7207(99)00184-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Gonadotropins, follicle-stimulating hormone (FSH), and luteinizing hormone (LH), are synthesized specifically in the gonadotropes of the anterior pituitary. The aim of this study was to investigate nuclear factors that bind specifically to the porcine FSH beta-subunit gene. We examined nuclear protein binding to 2.75 kilobase pairs (kbp) of DNA adjacent to the porcine FSH beta-subunit gene: about 2.32 kbp of upstream DNA and 0.43 kbp of downstream DNA. The upstream region contains only TATA box, CACCC element, and some imperfect sequences of cAMP-responsive element, activator protein-1 binding site, and activator protein-2 binding site. Gel mobility shift assay using nuclear proteins extracted from the porcine anterior pituitary revealed that the proteins bound to a limited region of DNA, 107 bp long (designated as Fd2), located about -800 bp upstream from the transcription initiation site. Competitive binding assays demonstrated that the protein binding was sequence specific; the addition of excess amounts of several putative regulatory sequences and plasmid (non-homologous) DNA fragments did not reduce the binding. Furthermore, all five subfragments of Fd2 were also bound by the pituitary nuclear proteins, showing that the entire region of Fd2 is involved in this interaction. Southwestern blotting demonstrated that at least seven protein species of 110, 98, 78, 63, 52, 42, and 35 kDa recognize Fd2. Nuclear proteins from several other porcine tissues were also able to bind to the Fd2 fragment but the gel shift patterns were different and the bindings were weak, although only the cerebellum showed a pattern of binding that was similar to that of the anterior pituitary. These data suggest that multiple proteins of the anterior pituitary recognize a specific region of the porcine FSH beta-subunit gene.
Collapse
Affiliation(s)
- Y Kato
- Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | | | | |
Collapse
|
37
|
Glenn DJ, Maurer RA. MRG1 binds to the LIM domain of Lhx2 and may function as a coactivator to stimulate glycoprotein hormone alpha-subunit gene expression. J Biol Chem 1999; 274:36159-67. [PMID: 10593900 DOI: 10.1074/jbc.274.51.36159] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Tissue-specific expression of the alpha-subunit gene of glycoprotein hormones involves an enhancer element designated the pituitary glycoprotein basal element, which interacts with the LIM homeodomain transcription factor, Lhx2. In the present studies we have explored the function of the LIM domain of Lhx2 in stimulating alpha-subunit transcription. When fused to the GAL4 DNA-binding domain, the LIM domain of Lhx2 was shown to contain a transcriptional activation domain. Furthermore, in the context of an alpha-subunit reporter gene in which a GAL4-binding site replaced the pituitary glycoprotein basal element, the LIM domain enhanced both basal and Ras-mediated transcription. In addition, a synergistic response to Ras activation was observed when the Lhx2 LIM domain and the transactivation domain of Elk1 are directed to a minimal reporter gene. A yeast two-hybrid screen identified the recently described melanocyte-specific gene-related gene 1 (MRG1) as an Lhx2 LIM-interacting protein. MRG1 was shown to bind Lhx2 in vitro, and a co-immunoprecipitation assay provided evidence that endogenous MRG1 forms a complex with Lhx2 in alphaT3-1 cells. Expression of MRG1 in alphaT3-1 cells enhanced alpha-subunit reporter gene activity. MRG1 was also shown to bind in vitro to the TATA-binding protein and the transcriptional coactivator, p300. These data suggest a model in which the Lhx2 LIM domain activates transcription through interaction with MRG1 leading to recruitment of p300/CBP and the TATA-binding protein.
Collapse
Affiliation(s)
- D J Glenn
- Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201, USA
| | | |
Collapse
|
38
|
Wersinger SR, Haisenleder DJ, Lubahn DB, Rissman EF. Steroid feedback on gonadotropin release and pituitary gonadotropin subunit mRNA in mice lacking a functional estrogen receptor alpha. Endocrine 1999; 11:137-43. [PMID: 10709760 DOI: 10.1385/endo:11:2:137] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/1999] [Revised: 06/23/1999] [Accepted: 07/07/1999] [Indexed: 11/11/2022]
Abstract
Steroid hormones regulate levels of gonadotropin mRNA in the pituitary, and gonadotropic hormones in plasma. To determine whether estrogen receptor alpha (ERalpha) mediates steroid negative feedback, wild type (WT) and estrogen receptor alpha knockout (ERalphaKO) mice of both sexes were gonadectomized and implanted with a Silastic capsule containing either estradiol (E2), dihydrotestosterone (DHT), testosterone, or a blank capsule. Ten days later, plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured. Pituitary mRNA levels of gonadotropin subunit (alpha, LHbeta, FSHbeta) and prolactin (PRL) were quantified. LH levels in gonad-intact ERalphaKO females were elevated, similar to values seen following gonadectomy. By contrast, serum LH concentrations in gonad-intact ERalphaKO males were low and rose following gonadectomy, suggesting androgen feedback. Estradiol treatment significantly decreased plasma LH in WT animals, but not in ERalphaKOs. In fact, in female ERalphaKOs, our dose of E2 increased plasma levels of LH as compared with untreated, ovariectomized ERalphaKOs. All the steroid treatments suppressed LH in WT animals whereas only DHT consistently suppressed LH concentrations in ERalphaKO mice. The postgonadectomy rise in plasma FSH was prevented by steroid treatments in WT females, but not in any of the other groups. Gonadotropin subunit and PRL mRNA responses to E2 treatment (both inhibitory and stimulatory) were absent in ERalphaKO mice, suggesting a critical role for ERalpha. Although E2 can exert negative feedback effects on LH release in both males and females by actions at the ERalpha, the androgen receptor plays the primary physiological role in the male mouse.
Collapse
Affiliation(s)
- S R Wersinger
- Department of Biology, University of Virginia, Charlottesville 22903, USA
| | | | | | | |
Collapse
|
39
|
Norwitz ER, Cardona GR, Jeong KH, Chin WW. Identification and characterization of the gonadotropin-releasing hormone response elements in the mouse gonadotropin-releasing hormone receptor gene. J Biol Chem 1999; 274:867-80. [PMID: 9873026 DOI: 10.1074/jbc.274.2.867] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The response of the pituitary gonadotrope to gonadotropin-releasing hormone (GnRH) correlates directly with the concentration of GnRH receptors (GnRHR) on the cell surface, which is mediated in part at the level of GnRHR gene expression. Several hormones have been implicated in this regulation, most notably GnRH itself. Despite these observations and the central role that GnRH is known to play in reproductive development and function, the molecular mechanism(s) by which GnRH regulates transcription of the GnRHR gene has not been well elucidated. Previous studies in this laboratory have identified and partially characterized the promoter region of the mouse GnRHR gene and demonstrated that the regulatory elements for tissue-specific expression as well as for GnRH regulation are present within the 1.2-kilobase 5'-flanking sequence. By using deletion and mutational analysis as well as functional transfection studies in the murine gonadotrope-derived alphaT3-1 cell line, we have localized GnRH responsiveness of the mouse GnRHR gene to two DNA sequences at -276/-269 (designated Sequence Underlying Responsiveness to GnRH-2 (SURG-2), which contains the consensus sequence for the activating protein-1-binding site) and -292/-285 (a novel element designated SURG-1), and demonstrated that this response is mediated via protein kinase C. By using the electrophoretic mobility shift assay, we further demonstrate that a member(s) of the Fos/Jun heterodimer superfamily is responsible in part for the DNA-protein complexes formed on SURG-2, using alphaT3-1 nuclear extracts. These data define a bipartite GnRH response element in the mouse GnRHR 5'-flanking sequence and suggest that the activating protein-1 complex plays a central role in conferring GnRH responsiveness to the murine GnRHR gene.
Collapse
Affiliation(s)
- E R Norwitz
- Division of Maternal-Fetal Medicine, Department of Obstetrics & Gynecology and Division of Genetics, Department of Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
| | | | | | | |
Collapse
|
40
|
Hall JE, Taylor AE, Hayes FJ, Crowley WF. Insights into hypothalamic-pituitary dysfunction in polycystic ovary syndrome. J Endocrinol Invest 1998; 21:602-11. [PMID: 9856414 DOI: 10.1007/bf03350785] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Polycystic ovary syndrome (PCOS) is characterized by menstrual dysfunction and hyperandrogenism in the absence of other known causes. While the pathogenesis of PCOS remains elusive and is likely to involve abnormalities in several systems, there has long been an association of abnormal gonadotropin secretion with this disorder. In recent studies we have determined that 94% of women meeting the broad criteria for PCOS have an increased LH/FSH ratio. Several lines of evidence suggest that the mechanisms underlying the increased LH/FSH ratio in PCOS include an increased frequency of GnRH secretion. Decreased sensitivity to progesterone negative feedback on the GnRH pulse generator may play a role in this neuroendocrine defect. Additional factors which may contribute to the low to normal FSH levels in the face of increased LH include chronic mild estrogen increases and possibly inhibin. In addition to these effects on the differential control of FSH, there is increased pituitary sensitivity of LH secretion to GnRH. Both estrogen and androgens have been proposed as candidates mediating these effects. Superimposed on these underlying abnormalities in gonadotropin secretion is a marked inhibitory effect of obesity on LH secretion which may be mediated at either a pituitary or hypothalamic level.
Collapse
Affiliation(s)
- J E Hall
- National Center for Infertility Research and Reproductive Endocrine Unit, Massachusetts General Hospital, Boston 02114, USA
| | | | | | | |
Collapse
|
41
|
Stanislaus D, Pinter JH, Janovick JA, Conn PM. Mechanisms mediating multiple physiological responses to gonadotropin-releasing hormone. Mol Cell Endocrinol 1998; 144:1-10. [PMID: 9863622 DOI: 10.1016/s0303-7207(98)00126-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A central question in endocrinology is how a single ligand interacting with a single receptor can mediate multiple responses. GnRH interaction with receptor offers a prime example, leading to the regulation of synthesis and release of at least three molecules, regulation of target cell responsiveness and receptor number. The present study suggests a molecular model consistent with extant data that provides a mechanism by which this may occur and, further, which allows for coordinate regulation.
Collapse
Affiliation(s)
- D Stanislaus
- Department of Physiology and Pharmacology, Oregon Health Sciences University, Portland 97201, USA
| | | | | | | |
Collapse
|
42
|
Kaiser UB, Jakubowiak A, Steinberger A, Chin WW. Differential effects of gonadotropin-releasing hormone (GnRH) pulse frequency on gonadotropin subunit and GnRH receptor messenger ribonucleic acid levels in vitro. Endocrinology 1997; 138:1224-31. [PMID: 9048630 DOI: 10.1210/endo.138.3.4968] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The hypothalamic hormone, GnRH, is released and transported to the anterior pituitary in a pulsatile manner, where it binds to specific high-affinity receptors and regulates gonadotropin biosynthesis and secretion. The frequency of GnRH pulses changes under various physiological conditions, and varying GnRH pulse frequencies have been shown to regulate differentially the secretion of LH and FSH and the expression of the gonadotropin alpha, LH beta, and FSH beta subunit genes in vivo. We demonstrate differential effects of varying GnRH pulse frequency in vitro in superfused primary monolayer cultures of rat pituitary cells. Cells were treated with 10 nM GnRH pulses for 24 h at a frequency of every 0.5, 1, 2, or 4 h. alpha, LH beta, and FSH beta messenger RNA (mRNA) levels were increased by GnRH at all pulse frequencies alpha and LH beta mRNA levels and LH secretion were stimulated to the greatest extent at a GnRH pulse frequency of every 30 min, whereas FSH beta mRNA levels and FSH secretion were stimulated maximally at a lower GnRH pulse frequency, every 2 h. GnRH receptor (GnRHR) mRNA levels also were increased by GnRH at all pulse frequencies and were stimulated maximally at a GnRH pulse frequency of every 30 min. Similar results were obtained when the dose of each pulse of GnRH was adjusted to maintain a constant total cumulative dose of GnRH over 24 h. These data show that gonadotropin subunit gene expression is regulated differentially by varying GnRH pulse frequencies in vitro, suggesting that the differential effects of varying GnRH pulse frequencies on gonadotropin subunit gene expression occur directly at the level of the pituitary. The pattern of regulation of GnRHR mRNA levels correlated with that of alpha and LH beta but was different from that of FSH beta. This suggests that alpha and LH beta mRNA levels are maximally stimulated when GnRHR levels are relatively high, whereas FSH beta mRNA levels are maximally stimulated at lower levels of GnRHR expression, and that the mechanism for differential regulation of the gonadotropins by varying pulse frequencies of GnRH may involve levels of GnRHR. Furthermore, these data suggest that the mechanisms whereby varying GnRH pulse frequencies stimulate alpha LH beta, and GnRHR gene expression are similar, whereas the stimulation of FSH beta mRNA levels may be different.
Collapse
Affiliation(s)
- U B Kaiser
- Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
| | | | | | | |
Collapse
|
43
|
McArdle CA. Functional interaction between gonadotropin-releasing hormone and PACAP in gonadotropes and alpha T3-1 cells. Ann N Y Acad Sci 1996; 805:112-20; discussion 120-1. [PMID: 8993397 DOI: 10.1111/j.1749-6632.1996.tb17477.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Gonadotropes, like other cells, receive informational input from multiple receptor types, acting through multiple intracellular signaling pathways, and are therefore faced with the task of integrating this input in order to respond appropriately to their environment. In recent years an increasing number of examples of functional interactions occurring between the PIC and adenylyl cyclase signaling pathways in gonadotropes have been described, and the discovery that these cells are targets for PACAP has provided a physiological context for earlier work on gonadotrope regulation by cyclic AMP. The development of the alpha T3-1 cell line has greatly facilitated investigation of the interaction between these signaling systems. In these cells we have obtained no evidence for interaction between the GnRH and PACAP receptor-effector systems at the level of receptor occupancy or expression, but these systems clearly do have reciprocal modulatory effects on second messenger generation and/or mobilization. We are now faced with the challenge of determining the physiological and/or pathophysiological relevance of such interactions.
Collapse
Affiliation(s)
- C A McArdle
- University of Bristol, Department of Medicine, UK.
| |
Collapse
|
44
|
Kaiser UB, Sabbagh E, Katzenellenbogen RA, Conn PM, Chin WW. A mechanism for the differential regulation of gonadotropin subunit gene expression by gonadotropin-releasing hormone. Proc Natl Acad Sci U S A 1995; 92:12280-4. [PMID: 8618885 PMCID: PMC40340 DOI: 10.1073/pnas.92.26.12280] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The hypothalamic hormone gonadotropin-releasing hormone (GnRH) is released in a pulsatile fashion, with its frequency varying throughout the reproductive cycle. Varying pulse frequencies and amplitudes differentially regulate the biosynthesis and secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by pituitary gonadotropes. The mechanism by which this occurs remains a major question in reproductive physiology. Previous studies have been limited by lack of available cell lines that express the LH and FSH subunit genes and respond to GnRH. We have overcome this limitation by transfecting the rat pituitary GH3 cell line with rat GnRH receptor (GnRHR) cDNA driven by a heterologous promoter. These cells, when cotransfected with regulatory regions of the common alpha, LH beta, or FSH beta subunit gene fused to a luciferase reporter gene, respond to GnRH with an increase in luciferase activity. Using this model, we demonstrate that different cell surface densities of the GnRHR result in the differential regulation of LH and FSH subunit gene expression by GnRH. This suggests that the differential regulation of gonadotropin subunit gene expression by GnRH observed in vivo in rats may, in turn, be mediated by varying gonadotrope cell surface GnRHR concentrations. This provides a physiologic mechanism by which a single ligand can act through a single receptor to regulate differentially the production of two hormones in the same cell.
Collapse
Affiliation(s)
- U B Kaiser
- Department of Medicine, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, MA, USA
| | | | | | | | | |
Collapse
|
45
|
Roberson MS, Misra-Press A, Laurance ME, Stork PJ, Maurer RA. A role for mitogen-activated protein kinase in mediating activation of the glycoprotein hormone alpha-subunit promoter by gonadotropin-releasing hormone. Mol Cell Biol 1995; 15:3531-9. [PMID: 7791760 PMCID: PMC230590 DOI: 10.1128/mcb.15.7.3531] [Citation(s) in RCA: 162] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Gonadotropin-releasing hormone (GnRH) interacts with a G protein-coupled receptor and increases the transcription of the glycoprotein hormone alpha-subunit gene. We have explored the possibility that mitogen-activated protein kinase (MAPK) plays a role in mediating GnRH effects on transcription. Activation of the MAPK cascade by an expression vector for a constitutively active form of the Raf-1 kinase led to stimulation of the alpha-subunit promoter in a concentration-dependent manner. GnRH treatment was found to increase the phosphorylation of tyrosine residues of MAPK and to increase MAPK activity, as determined by an immune complex kinase assay. A reporter gene assay using the MAPK-responsive, carboxy-terminal domain of the Elk1 transcription factor was also consistent with GnRH-induced activation of MAPK. Interference with the MAPK pathway by expression vectors for kinase-defective MAPKs or vectors encoding MAPK phosphatases reduced the transcription-stimulating effects of GnRH. The DNA sequences which are required for responses to GnRH include an Ets factor-binding site. An expression vector for a dominant negative form of Ets-2 was able to reduce GnRH effects on expression of the alpha-subunit gene. These findings provide evidence that GnRH treatment leads to activation of the MAPK cascade in gonadotropes and that activation of MAPK contributes to stimulation of the alpha-subunit promoter. It is likely that an Ets factor serves as a downstream transcriptional effector of MAPK in this system.
Collapse
Affiliation(s)
- M S Roberson
- Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland 97201, USA
| | | | | | | | | |
Collapse
|
46
|
Conn PM, Janovick JA, Stanislaus D, Kuphal D, Jennes L. Molecular and cellular bases of gonadotropin-releasing hormone action in the pituitary and central nervous system. VITAMINS AND HORMONES 1995; 50:151-214. [PMID: 7709600 DOI: 10.1016/s0083-6729(08)60656-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- P M Conn
- Oregon Regional Primate Research Center, Beaverton 97006
| | | | | | | | | |
Collapse
|
47
|
Schoderbek W, Roberson M, Maurer R. Two different DNA elements mediate gonadotropin releasing hormone effects on expression of the glycoprotein hormone alpha-subunit gene. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53558-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
|
48
|
Ben-Menahem D, Shraga Z, Lewy H, Limor R, Hammel I, Stein R, Naor Z. Dissociation between release and gene expression of gonadotropin alpha-subunit in gonadotropin-releasing hormone-stimulated alpha T3-1 cell line. Biochemistry 1992; 31:12893-8. [PMID: 1281429 DOI: 10.1021/bi00166a026] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The alpha T3-1 cell line which was derived by targeted tumorigenesis in transgenic mice [Windle et al. (1990) Mol. Endocrinol. 4, 597-603] possesses high-affinity binding sites for GnRH analogs coupled to enhanced phosphoinositide turnover and phospholipase D activity. Incubation of alpha T3-1 cells with [D-Trp6]-GnRH analog (GnRH-A) resulted in a rapid increase in gonadotropin alpha-subunit mRNA levels which was detected already at 30 min of incubation (0.1 nM GnRH-A, 3-fold, p < 0.01). The effect diminished with time to reach basal levels at about 12 h of incubation, with a secondary rise in alpha mRNA levels between 12 and 24 h of incubation. Addition of the protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA, 100 ng/mL) or the Ca2+ ionophore ionomycin (1 microM) to alpha T3-1 cells also resulted in a rapid increase in alpha-subunit mRNA levels. Surprisingly, GnRH-induced alpha-subunit release was detected only after a lag of 4 h of incubation. Thus, dissociation between exocytosis and gene expression can be demonstrated in GnRH-stimulated alpha T3-1 cell line.
Collapse
Affiliation(s)
- D Ben-Menahem
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
| | | | | | | | | | | | | |
Collapse
|
49
|
Oppenheim DS, Bikkal H, Crowley WF, Klibanski A. Effects of chronic GnRH analogue administration on gonadotrophin and alpha-subunit secretion in post-menopausal women. Clin Endocrinol (Oxf) 1992; 36:559-64. [PMID: 1385024 DOI: 10.1111/j.1365-2265.1992.tb02265.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE To investigate in detail the regulation of LH, FSH, and alpha-subunit secretion by a GnRH agonist analogue under physiological conditions of gonadotrophin elevation. SUBJECTS Six normal healthy post-menopausal women. DESIGN Subjects were given D-Trp6-Pro9-Net-GnRH (GnRHa), 32 micrograms/kg, subcutaneously, daily for 24 days. On days 1, 2, 3, 4, 7, 11, 14, 17, 21, and 24, blood samples before and after GnRHa injection were taken. Sampling was continued off GnRHa twice a week for 4 weeks and then on days 66, 76, and 98. GnRH tests (100 micrograms i.v.) were performed on days 0, 24, and 98. MEASUREMENTS All serum samples were analysed for LH, FSH, and alpha-subunit levels. RESULTS LH and FSH levels reached a maximum on day 2 after which there was a steady decline to day 24. LH did not begin to rise again until day 44 (20 days off GnRHa), then rose steadily. FSH began to rise earlier, on day 34 (10 days off GnRHa). alpha-Subunit levels also showed maximum elevation on day 2 but remained equally elevated throughout the period of GnRHa administration and then fell rapidly to baseline by day 34. LH, FSH, and alpha-subunit responses to i.v. GnRH were absent on day 24 and were equivalent to baseline on day 98. CONCLUSIONS We conclude that there is a striking dissociation in the regulation of gonadotrophin and alpha-subunit secretion in response to GnRHa in normal post-menopausal women. Gonadotrophin secretion is profoundly suppressed during GnRHa administration and recovers only after a long delay post-treatment, while alpha-subunit is markedly stimulated and recovers rapidly. The difference between this pattern and that seen in patients with pituitary tumours could be useful for diagnosis.
Collapse
Affiliation(s)
- D S Oppenheim
- Neuroendocrine Unit, Massachusetts General Hospital, Boston 02114
| | | | | | | |
Collapse
|
50
|
Abstract
In this review article evidence is assembled from the neuroendocrinology of women with polycystic ovary-like syndrome (PCOS), to argue that the central dysregulation of gonadotropin secretion as found in the syndrome is not the cause of its development. The increased amplitude of luteinizing hormone (LH) pulses is explained by an increased pituitary sensitivity to gonadotropin releasing hormone (GnRH) due to prolonged unopposed estrogen exposure of the gonadotropic cells. The increase in pulse frequency cannot be used in the argument because it may be the cause for, as well the result of, the pathological status of the ovary. A good argument for a pathogenetic involvement of central factors, however, is the reversed day/night rhythm in adolescent girls with PCOS. A critical review of the literature does not give evidence of involvement of either obesity or catecholamines in the central abnormalities. Therefore they cannot cause PCOS via central feedback systems. The response of the gonadotropins to progesterone is the same as it is in normally cycling women. Androgens exert a variable effect on LH secretory patterns, although they do induce the typical change of PCOS in the ovaries. This argues for an ovarian rather than for a central cause. Endogenous opiates seem to be increased in PCOS. It can be argued that this should suppress both LH secretion and adrenal androgen secretion. It should also stimulate insulin-like growth factor (IGF)-binding proteins, thereby binding more IGF with less stimulatory action on the theca cells to produce androgens. Therefore endogenous opiates do not seem to be involved in the pathogenesis of PCOS either. Studies in PCOS during the recovery from GnRH agonist treatment show that the luteinizing hormone/follicle stimulating hormone (LH/FSH) ratio is quite normal for some time during the recovery phase. However, PCOS always develops again. This therefore does not give a clue either. In pulsatile GnRH stimulation of PCOS patients, the LH and FSH secretory patterns completely normalize. However, the symptoms of PCOS continue under this stimulation and the clinical pattern does not change dramatically. This gives the best argument that PCOS is caused by one or more peripheral factors, which may be ovarian in origin, rather than by central factors.
Collapse
Affiliation(s)
- J Schoemaker
- Department of Obstetrics and Gynecology, Free University Hospital, Amsterdam, The Netherlands
| |
Collapse
|