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Fortin J, Ongaro L, Li Y, Tran S, Lamba P, Wang Y, Zhou X, Bernard DJ. Minireview: Activin Signaling in Gonadotropes: What Does the FOX say… to the SMAD? Mol Endocrinol 2015; 29:963-77. [PMID: 25942106 DOI: 10.1210/me.2015-1004] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The activins were discovered and named based on their abilities to stimulate FSH secretion and FSHβ (Fshb) subunit expression by pituitary gonadotrope cells. According to subsequent in vitro observations, activins also stimulate the transcription of the GnRH receptor (Gnrhr) and the activin antagonist, follistatin (Fst). Thus, not only do activins stimulate FSH directly, they have the potential to regulate both FSH and LH indirectly by modulating gonadotrope sensitivity to hypothalamic GnRH. Moreover, activins may negatively regulate their own actions by stimulating the production of one of their principal antagonists. Here, we describe our current understanding of the mechanisms through which activins regulate Fshb, Gnrhr, and Fst transcription in vitro. The activin signaling molecules SMAD3 and SMAD4 appear to partner with the winged-helix/forkhead transcription factor, forkhead box L2 (FOXL2), to regulate expression of all 3 genes. However, in vivo data paint a different picture. Although conditional deletion of Foxl2 and/or Smad4 in murine gonadotropes produces impairments in FSH synthesis and secretion as well as in pituitary Fst expression, Gnrhr mRNA levels are either unperturbed or increased in these animals. Surprisingly, gonadotrope-specific deletion of Smad3 alone or with Smad2 does not impair FSH production or fertility; however, mice harboring these mutations may express a DNA binding-deficient, but otherwise functional, SMAD3 protein. Collectively, the available data firmly establish roles for FOXL2 and SMAD4 in Fshb and Fst expression in gonadotrope cells, whereas SMAD3's role requires further investigation. Gnrhr expression, in contrast, appears to be FOXL2, SMAD4, and, perhaps, activin independent in vivo.
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Affiliation(s)
- Jérôme Fortin
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Luisina Ongaro
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Yining Li
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Stella Tran
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Pankaj Lamba
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Ying Wang
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Xiang Zhou
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Daniel J Bernard
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
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Bilezikjian LM, Justice NJ, Blackler AN, Wiater E, Vale WW. Cell-type specific modulation of pituitary cells by activin, inhibin and follistatin. Mol Cell Endocrinol 2012; 359:43-52. [PMID: 22330643 PMCID: PMC3367026 DOI: 10.1016/j.mce.2012.01.025] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Revised: 01/26/2012] [Accepted: 01/30/2012] [Indexed: 01/01/2023]
Abstract
Activins are multifunctional proteins and members of the TGF-β superfamily. Activins are expressed locally in most tissues and, analogous to the actions of other members of this large family of pleiotropic factors, play prominent roles in the regulation of diverse biological processes in both differentiated and embryonic stem cells. They have an essential role in maintaining tissue homeostasis in the adult and are known to contribute to the developmental programs in the embryo. Activins are further implicated in the growth and metastasis of tumor cells. Through distinct modes of action, inhibins and follistatins function as antagonists of activin and several other TGF-β family members, including a subset of BMPs/GDFs, and modulate cellular responses and the signaling cascades downstream of these ligands. In the pituitary, the activin pathway is known to regulate key aspects of gonadotrope functions and also exert effects on other pituitary cell types. As in other tissues, activin is produced locally by pituitary cells and acts locally by exerting cell-type specific actions on gonadotropes. These local actions of activin on gonadotropes are modulated by the autocrine/paracrine actions of locally secreted follistatin and by the feedback actions of gonadal inhibin. Knowledge about the mechanism of activin, inhibin and follistatin actions is providing information about their importance for pituitary function as well as their contribution to the pathophysiology of pituitary adenomas. The aim of this review is to highlight recent findings and summarize the evidence that supports the important functions of activin, inhibin and follistatin in the pituitary.
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Affiliation(s)
- Louise M Bilezikjian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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Pisarska MD, Barlow G, Kuo FT. Minireview: roles of the forkhead transcription factor FOXL2 in granulosa cell biology and pathology. Endocrinology 2011; 152:1199-208. [PMID: 21248146 PMCID: PMC3206711 DOI: 10.1210/en.2010-1041] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The forkhead transcription factor (FOXL2) is an essential transcription factor in the ovary. It is important in ovarian development and a key factor in female sex determination. In addition, FOXL2 plays a significant role in the postnatal ovary and follicle maintenance. The diverse transcriptional activities of FOXL2 are likely attributable to posttranslational modifications and binding to other key proteins involved in granulosa cell function. Mutations of FOXL2 lead to disorders of ovarian function ranging from premature follicle depletion and ovarian failure to unregulated granulosa cell proliferation leading to tumor formation. Thus, FOXL2 is a key regulator of granulosa cell function and a master transcription factor in these cells.
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Affiliation(s)
- Margareta D Pisarska
- Center for Fertility and Reproductive Medicine, Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center, 8635 West Third Street, Suite 160W, Los Angeles, California 90048, USA.
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Bilezikjian LM, Vale WW. The Local Control of the Pituitary by Activin Signaling and Modulation. OPEN NEUROENDOCRINOLOGY JOURNAL (ONLINE) 2011; 4:90-101. [PMID: 21927629 PMCID: PMC3173763 DOI: 10.2174/1876528901104010090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pituitary gland plays a prominent role in the control of many physiological processes. This control is achieved through the actions and interactions of hormones and growth factors that are produced and secreted by the endocrine cell types and the non-endocrine constituents that collectively and functionally define this complex organ. The five endocrine cell types of the anterior lobe of the pituitary, somatotropes, lactotropes, corticotropes, thyrotropes and gonadotropes, are defined by their primary product, growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH) and follicle stimulating hormone (FSH)/luteinizing hormone (LH). They are further distinguishable by the presence of cell surface receptors that display high affinity and selectivity for specific hypothalamic hormones and couple to appropriate downstream signaling pathways involved in the control of cell type specific responses, including the release and/or synthesis of pituitary hormones. Central control of the pituitary via the hypothalamus is further fine-tuned by the positive or negative actions of peripheral feedback signals and of a variety of factors that originate from sources within the pituitary. The focus of this review is the latter category of intrinsic factors that exert local control. Special emphasis is given to the TGF-β family of growth factors, in particular activin effects on the gonadotrope population, because a considerable body of evidence supports their contribution to the local modulation of the embryonic and postnatal pituitary as well as pituitary pathogenesis. A number of other substances, including members of the cytokine and FGF families, VEGF, IGF1, PACAP, Ghrelin, adenosine and nitric oxide have also been shown or implicated to function as autocrine/paracrine factors, though, definitive proof remains lacking in some cases. The ever-growing list of putative autocrine/paracrine factors of the pituitary nevertheless has highlighted the complexity of the local network and its impact on pituitary functions.
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Affiliation(s)
- Louise M Bilezikjian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California, USA
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Blount AL, Schmidt K, Justice NJ, Vale WW, Fischer WH, Bilezikjian LM. FoxL2 and Smad3 coordinately regulate follistatin gene transcription. J Biol Chem 2009; 284:7631-45. [PMID: 19106105 PMCID: PMC2658057 DOI: 10.1074/jbc.m806676200] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 12/10/2008] [Indexed: 12/19/2022] Open
Abstract
Follistatin is a transcriptional target and a modulator of activin action. Through an autocrine/paracrine loop, activin controls follistatin levels and thus regulates its own bioavailability. In gonadotropic alphaT3-1 cells, activin induces follistatin transcription primarily through the action of Smad3 at an intronic Smad-binding element (SBE1). Using a proteomics approach, we searched for endogenous alphaT3-1 proteins that participate in SBE1-mediated transcription. We identified FoxL2, a member of the forkhead family, as a candidate modulator of SBE1 function. Mutations of FoxL2 are associated with the blepharophimosis/ptosis/epicanthus inversus syndrome characterized with craniofacial defects and premature ovarian failure. FoxL2 localizes to alpha-glycoprotein subunit- and follicle-stimulating hormone beta-positive cells of the adult mouse pituitary and is present in alphaT3-1 and LbetaT2 cells, but its pituitary actions remain largely unknown. We have determined that FoxL2 binds to a forkhead-binding element (FKHB) located just downstream of the SBE1 site of the follistatin gene and functions as a Smad3 partner to drive SBE1-mediated transcription in alphaT3-1 cells treated with activin. Chromatin immunoprecipitation assays confirm that endogenous FoxL2 and Smad3 are recruited to the intronic enhancer of the follistatin gene where the SBE1 and FKHB sites are located. Exogenous FoxL2 enhances SBE1-mediated transcription, and short hairpin RNA-mediated knockdown of endogenous FoxL2 protein compromises this effect in alphaT3-1 cells. FoxL2 directly associates with Smad3 but not Smad2 or Smad4. This association between Smad3 and FoxL2 is mediated by the MH2 domain of Smad3 and is dependent on an intact forkhead domain in FoxL2. Altogether, these observations highlight a novel role for FoxL2 and suggest that it may function as a transcriptional regulator and a coordinator of Smad3 targets.
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Affiliation(s)
- Amy L Blount
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037, USA
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Taylor JE, Miller BT, Gray KD, Scott RT, Catherino WH, Segars JH. The mechanism responsible for the supraphysiologic gonadotropin surge in females treated with gonadotropin-releasing hormone (GnRH) agonist and primed with GnRH antagonist. Fertil Steril 2009; 93:1668-75. [PMID: 19200975 DOI: 10.1016/j.fertnstert.2008.12.047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 11/20/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE To elucidate the physiologic mechanism responsible for the supraphysiologic gonadotropin release from the pituitary induced by gonadotropin-releasing hormone (GnRH) agonist in female rats primed with GnRH antagonist. DESIGN Controlled experimental intervention. SETTING Government research facility. ANIMAL(S) Forty 8-week-old Sprague-Dawley rats. INTERVENTION(S) Forty oophorectomized rats were randomized into four treatment groups of 10: group A, control vehicles; group B, GnRH agonist (leuprolide acetate; 1.7 microg/kg twice a day) on day 4; group C, GnRH antagonist (Nal-Lys; 3 mg/kg each day) days 1 to 4; or group D, GnRH antagonist (Nal-Lys; 3 mg/kg each day) days 1 to 4 plus GnRH agonist (1.7 microg/kg twice a day) on day 4. MAIN OUTCOME MEASURE(S) Immunohistochemical methods, Northern and in situ hybridization to quantitate pituitary follicle-stimulating hormone beta (FSH-beta), luteinizing hormone beta (LH-beta), and GnRH receptor (GnRH-R) messenger RNA (mRNA), and receptor protein levels in all treatment groups. RESULT(S) Treatment with GnRH antagonist was associated with increased storage of gonadotropin in the pituitary for FSH-beta and LH-beta, but mRNA levels were unchanged. The GnRH-R mRNA decreased after GnRH-agonist treatment but remained stable in the GnRH-antagonist treatment groups. Levels of GnRH-R were decreased after GnRH-antagonist treatment. CONCLUSION(S) These data indicate that the in vivo mechanism responsible for the exaggerated release of gonadotropins in rats primed with GnRH antagonist and treated with GnRH agonist was an increase in releasable gonadotropin pools coupled with a reduction in GnRH-R, but receptor function was preserved.
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Affiliation(s)
- Joelle E Taylor
- Reproductive Biology and Medicine Branch, National Institutes of Health, Bethesda, Maryland 20814, USA
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A mathematical model for the actions of activin, inhibin, and follistatin on pituitary gonadotrophs. Bull Math Biol 2008; 70:2211-28. [PMID: 18690487 DOI: 10.1007/s11538-008-9341-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
The timed secretion of the luteinizing hormone (LH) and follicle stimulating hormone (FSH) from pituitary gonadotrophs during the estrous cycle is crucial for normal reproductive functioning. The release of LH and FSH is stimulated by gonadotropin releasing hormone (GnRH) secreted by hypothalamic GnRH neurons. It is controlled by the frequency of the GnRH signal that varies during the estrous cycle. Curiously, the secretion of LH and FSH is differentially regulated by the frequency of GnRH pulses. LH secretion increases as the frequency increases within a physiological range, and FSH secretion shows a biphasic response, with a peak at a lower frequency. There is considerable experimental evidence that one key factor in these differential responses is the autocrine/paracrine actions of the pituitary polypeptides activin and follistatin. Based on these data, we develop a mathematical model that incorporates the dynamics of these polypeptides. We show that a model that incorporates the actions of activin and follistatin is sufficient to generate the differential responses of LH and FSH secretion to changes in the frequency of GnRH pulses. In addition, it shows that the actions of these polypeptides, along with the ovarian polypeptide inhibin and the estrogen-mediated variations in the frequency of GnRH pulses, are sufficient to account for the time courses of LH and FSH plasma levels during the rat estrous cycle. That is, a single peak of LH on the afternoon of proestrus and a double peak of FSH on proestrus and early estrus. We also use the model to identify which regulation pathways are indispensable for the differential regulation of LH and FSH and their time courses during the estrous cycle. We conclude that the actions of activin, inhibin, and follistatin are consistent with LH/FSH secretion patterns, and likely complement other factors in the production of the characteristic secretion patterns in female rats.
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Blount AL, Vaughan JM, Vale WW, Bilezikjian LM. A Smad-binding Element in Intron 1 Participates in Activin-dependent Regulation of the Follistatin Gene. J Biol Chem 2008; 283:7016-26. [DOI: 10.1074/jbc.m709502200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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Moore JP, Winters SJ. Weaning and the developmental changes in follicle-stimulating hormone, pituitary adenylate cyclase-activating polypeptide, and inhibin B in the male rat. Biol Reprod 2007; 78:752-60. [PMID: 18160680 DOI: 10.1095/biolreprod.107.065466] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Pituitary Fshb concentrations increase markedly and selectively beginning on Postnatal Day 20 in the male rat. To evaluate the factors potentially responsible for this rise in FSH, we adjusted the time of weaning, which is generally also on Day 20. Male rat pups were provided nutrients by suckling only and were weaned to laboratory chow earlier (Day 17) or later (Day 23) than normally performed in animal facilities (Day 20). Between ages 17 and 29 days, significant increases were seen in serum LH (1.4-fold) and FSH (2.4-fold) levels; pituitary expression of Lhb (5.4-fold), Fshb (21.3-fold), and inhibin beta B (Inhbb, 2.26-fold) mRNAs; and testicular expression of Inhbb (10-fold) mRNA. Concurrently, significant decreases occurred in serum inhibin B levels (1.8-fold); pituitary adenylate cyclase-activating polypeptide (Adcyap1, 4.2-fold), total follistatin (Fst, 3.5-fold), and Fst isoform 288 (5.6-fold) mRNAs; and testicular expression of inhibin beta A (8.2-fold) mRNA. Early weaning significantly increased serum FSH but not LH and increased pituitary expression of Fshb and GnRH receptor (Gnrhr) mRNAs but not Lhb. Early weaning also significantly decreased serum inhibin B but increased testicular expression of the Inhbb subunit. Early weaning also caused pituitary expression of Fst and Adcyap1 to decline earlier than in the control group. Immediately after weaning, growth accelerated substantially, and the time of weaning produced significant and differential effects on circulating leptin levels that were not related to indices of FSH production. From these observations, we propose the novel hypothesis that the increase in growth rate subsequent to weaning signals circulating inhibin B levels to fall and pituitary Adcyap1 and consequently Fst expression to decrease, and that these events together facilitate the rise in Fshb and Gnrhr expression by increasing pituitary activin signaling.
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Affiliation(s)
- Joseph P Moore
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
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Prendergast KA, Burger LL, Aylor KW, Haisenleder DJ, Dalkin AC, Marshall JC. Pituitary Follistatin Gene Expression in Female Rats: Evidence That Inhibin Regulates Transcription1. Biol Reprod 2004; 70:364-70. [PMID: 14561646 DOI: 10.1095/biolreprod.103.021733] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Follistatin (FS), along with the members of the transforming growth factor beta family activin and inhibin, are important regulators of FSH secretion and messenger RNA production. While activin and inhibin appear to function as tonic modulators of FSH (stimulatory and inhibitory, respectively), dynamic changes in FS are noted through the estrous cycle and under varying physiological experimental paradigms. This suggests that FS is a major contributor to the precisely coordinated secretion of FSH that maintains reproductive function. The aim of this study was to investigate changes in FS, in particular the early (<12 h) rise observed after ovariectomy (OVX), and to determine whether these changes were as a consequence of variations in gene transcription rates. FS primary transcript (PT) and mRNA were found to increase 3-fold 12 h post-OVX, indicating increased gene transcription during this time period. Replacement with estradiol and/or blockade of GnRH had only modest effects on FS PT concentration. Inhibin immunoneutralization of intact rats resulted in a 3-fold increase in FS PT 12 h after administration of inhibin alpha antisera. Significant increases in FS mRNA at both 2 and 12 h also suggested that inhibin also may have effects on message stability. After administration of recombinant human inhibin A, there was a prompt decline in both FS PT and mRNA. These results indicate that inhibin is a major regulator of FS, both by transcriptional and nontranscriptional mechanisms.
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Affiliation(s)
- Kathleen A Prendergast
- Department of Internal Medicine, and the Center for Research in Reproduction, University of Virginia, Charlottesville, Virginia 22908, USA.
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Nakatani M, Yamakawa N, Matsuzaki T, Shimasaki S, Sugino H, Tsuchida K. Genomic organization and promoter analysis of mouse follistatin-related gene (FLRG). Mol Cell Endocrinol 2002; 189:117-23. [PMID: 12039070 DOI: 10.1016/s0303-7207(01)00734-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Follistatin (FS) is well characterized as an activin-binding protein. Recently, a novel follistatin-like protein called follistatin-related gene (FLRG) that has a similar domain organization to that of follistatin has been identified. Like follistatins, FLRG binds activins and bone morphogenetic proteins (BMPs). To study the regulation of FLRG expression, we have analyzed the genomic organization and promoter of the mouse FLRG gene. The mouse FLRG gene consists of five exons, and each encodes discrete functional regions. The overall genomic structure of FLRG is similar to that of FS except that the FLRG gene is missing one exon that codes a third FS domain found in FS. The promoter that covers 2.5 kbp and is linked to a luciferase reporter construct is active in human cervical carcinoma HeLa cells as well as in human embryonic kidney (HEK293) cells. Deletion analysis of the promoter regions indicates that a proximal 550 base pairs are enough for basal FLRG promoter activity in the cell lines. FLRG promoter activity is significantly augmented by phorbol 12-myristate 13-acetate (PMA) treatment, but not by cAMP stimulation. By contrast, FS promoter is activatable either by cAMP or PMA. Thus, although FS and FLRG are structurally and functionally related, their modes of regulation by external stimuli are different.
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Affiliation(s)
- Masashi Nakatani
- Institute for Enzyme Research, The University of Tokushima, 3-18-15 Kuramoto, 770-8503, Tokushima, Japan
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Chen YG, Lui HM, Lin SL, Lee JM, Ying SY. Regulation of cell proliferation, apoptosis, and carcinogenesis by activin. Exp Biol Med (Maywood) 2002; 227:75-87. [PMID: 11815670 DOI: 10.1177/153537020222700201] [Citation(s) in RCA: 173] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The aim of this review is to provide insight into the molecular mechanisms by which activin A modulates cell proliferation, apoptosis, and carcinogenesis in vitro and in vivo. Activin A, a member of the TGFbeta superfamily, has various effects on diverse biological systems, including cell growth inhibition in many cell types. However, the mechanism(s) by which activin exerts its inhibitory effects are not yet understood. This review highlights activin's effects on activin receptors and signaling pathway, modulation of activin signaling, and regulation of cell proliferation and apoptosis by activin. Based on the experiences of all the authors, we emphasized cell cycle inhibitors such as p16 and p21 and regulators of apoptosis such as p53 and members of the bcl-2 family. Aside from activin's inhibition of cell proliferation and enhancement of apoptosis, other newly developed methods for molecular studies of apoptosis by activin were briefly presented that support the role of activin as an inhibitor of carcinogenesis and cancer progression. These methods include subtractive hybridization based on covalent bonding, a simple and accurate means to determine molecular profile of as few as 20 cells based on an RNA-PCR approach, and a messenger RNA-antisense DNA interference phenomenon (D-RNAi), resulting in a long-term gene knockout effects.
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Affiliation(s)
- Ye-Guang Chen
- Division of Biomedical Sciences, University of California, Riverside, California 92521, USA
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Baratta M, West LA, Turzillo AM, Nett TM. Activin modulates differential effects of estradiol on synthesis and secretion of follicle-stimulating hormone in ovine pituitary cells. Biol Reprod 2001; 64:714-9. [PMID: 11159377 DOI: 10.1095/biolreprod64.2.714] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In several physiological paradigms, secretion of FSH and LH are not coordinately regulated. Because these hormones appear to be produced by a single cell type in the anterior pituitary gland, their discordant regulation must be related to differential intracellular responses to various stimuli. Estradiol-17beta (estradiol) has been shown to influence secretion of both FSH and LH and some of its effects are mediated directly on the gonadotrope. Changes in expression of intrapituitary factors such as activin and follistatin may mediate effects of estradiol and account for discordant patterns of FSH and LH. The aims of this study were 1) to determine if estradiol alters expression of genes encoding activin, follistatin, or both in ovine pituitary cells; and 2) to observe the effects of immunoneutralizing activin B in vitro on gonadotropin secretion. Pituitary cells from five ewes in the anestrous season were cultured for 24 h with estradiol (0.01 or 1.0 nM). Estradiol reduced basal secretion of FSH in a dose-dependent manner (P: < 0.001) and simultaneously increased basal secretion of LH (P: < 0.001). Decreased secretion of FSH in estradiol-treated cultures was accompanied by suppressed levels of FSHbeta subunit mRNA (P: < 0.001). Amounts of mRNA for activin beta(B) were reduced in a dose-dependent manner by estradiol (27% +/- 4.9% at 0.01 nM, P: < 0.02; and 46% +/- 3.9% at 1.0 nM, P: < 0.002). In contrast, mRNA for follistatin was not affected by treatment with estradiol. Treatment of pituitary cells with an antibody to activin B reduced secretion of FSH by 50% (P: < 0.01) without influencing secretion of LH. These data lead us to conclude that discordant secretion of gonadotropins can be induced by estradiol acting directly at the pituitary level. The inhibitory effect of estradiol on FSH secretion may be mediated indirectly through decreased pituitary expression of the activin gene.
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Affiliation(s)
- M Baratta
- Institute of Veterinary Physiology, University of Parma, 43100 Parma, Italy
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Abstract
Activins are growth and differentiation factors belonging to the transforming growth factor-β superfamily. They are dimeric proteins consisting of two inhibin β subunits. The structure of activins is highly conserved during vertebrate evolution. Activins signal through type I and type II receptor proteins, both of which are serine/threonine kinases. Subsequently, downstream signals such as Smad proteins are phosphorylated. Activins and their receptors are present in many tissues of mammals and lower vertebrates where they function as autocrine and (or) paracrine regulators of a variety of physiological processes, including reproduction. In the hypothalamus, activins are thought to stimulate the release of gonadotropin-releasing hormone. In the pituitary, activins increase follicle-stimulating hormone secretion and up-regulate gonadotropin-releasing hormone receptor expression. In the ovaries of vertebrates, activins are expressed predominantly in the follicular layer of the oocyte where they regulate processes such as folliculogenesis, steroid hormone production, and oocyte maturation. During pregnancy, activin-A is also involved in the regulation of placental functions. This review provides a brief overview of activins and their receptors, including their structures, expression, and functions in the female reproductive axis as well as in the placenta. Special effort is made to compare activins and their receptors in different vertebrates. Key words: activins, activin receptors, reproductive axis, placenta.
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15
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Abstract
Follistatin was first described in 1987 as a follicle-stimulating hormone inhibiting substance present in ovarian follicular fluid. We now know that this effect of follistatin is only one of its many properties in a number of reproductive and nonreproductive systems. A majority of these functions are facilitated through the affinity of follistatin for activin, where activin's effects are neutralized through its binding to follistatin. As such, the interplay between follistatin and activin represents a powerful regulatory mechanism that impinges on a variety of cellular processes within the body. In this review we focus on the biochemical characteristics of follistatin and its interaction with activin and discuss the emerging role of these proteins as potent tissue regulators in the gonad, pituitary gland, pregnancy membranes, vasculature, and liver. Consideration is also given to the larger family of proteins that contain follistatin-like modules, in particular with regard to their functional and structural implications.
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Affiliation(s)
- D J Phillips
- Institute of Reproduction and Development, Monash University, Clayton, Victoria, 3168, Australia.
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Zhang YQ, Kanzaki M, Shibata H, Kojima I. Regulation of the expression of follistatin in rat hepatocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1354:204-10. [PMID: 9427529 DOI: 10.1016/s0167-4781(97)00085-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To elucidate the regulation of follistatin production in the liver, we studied changes in steady-state follistatin mRNA levels in cultured rat hepatocytes. Activin A stimulated follistatin mRNA levels in a time- and concentration-dependent manner. The stimulatory effect of activin A on follistatin mRNA was significant at 2 h, maximal at 6 h and declined thereafter. Incubating the cells with EGF increased follistatin mRNA levels at 48 h and later. The EGF-induced increase in follistatin mRNA was markedly inhibited by exogenous follistatin in the culture medium, which blocks the action of activin A synthesized in hepatocytes, suggesting that endogenous activin A at least partly mediated the effect of EGF. We also examined the effects of transforming growth factor-beta (TGF-beta), glucagon and alpha-adrenergic agonist, phenylephrine, on follistatin mRNA levels. TGF-beta increased the follistatin mRNA to levels similar to those caused by activin A. Phenylephrine and glucagon also increased follistatin mRNA levels but the effects were transient and weaker than those caused by activin A. Finally, follistatin mRNA levels were markedly increased in remnant liver 3 h after 70% hepatectomy. The mRNA remained elevated for up to 72 h. These results indicate that the expression of mRNA for follistatin is positively controlled by activin A, TGF-beta and other hormones or neurotransmitters. The stimulatory effect of EGF on follistatin mRNA is mediated by activin A released from hepatocytes.
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Affiliation(s)
- Y Q Zhang
- Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
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17
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van Schaik RH, Wierikx CD, Looijenga LH, Oosterhuis JW, de Jong FH. Human testicular germ cell tumours express inhibin subunits, activin receptors and follistatin mRNAs. Br J Cancer 1997; 76:1191-8. [PMID: 9365168 PMCID: PMC2228115 DOI: 10.1038/bjc.1997.532] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Germ cell development is influenced by activin and inhibin, which are produced by Sertoli cells. Activin also affects differentiation of mouse embryonal carcinoma cells, which, to a certain extent, resemble the embryonal carcinoma component of germ cell tumours. Therefore, the expression of inhibin/activin subunits, of activin receptors and of the activin-binding protein follistatin was studied in testicular germ cell tumours, using RNAase protection assays. Testicular germ cell tumours of adolescents and adults (TGCTs) and spermatocytic seminomas expressed activin type I and type II receptors (ActRI and ActRII respectively). Seminomas expressed significantly lower levels of ActRIIA (P<0.05, Mann-Whitney U-test) and higher levels of ActRIA (P<0.05) and ActRIB (P<0.05) compared with non-seminomas. All tumours expressed inhibin beta-subunit transcripts, which are a prerequisite for activin synthesis. Non-seminomas contained significantly higher levels of the inhibin betaA subunit (P<0.001) compared with seminomas. No activin betaC subunit transcripts could be demonstrated by RNAase protection. Inhibin alpha-subunit expression was absent in the spermatocytic seminomas, in six out of nine seminomas and in 10 out of 11 non-seminomas. Follistatin was expressed predominantly in non-seminomas and spermatocytic seminomas. This expression of activin type I and type II receptors in combination with expression of inhibin beta-subunits indicates that activin may act as a para- or autocrine factor in the regulation of growth and differentiation of tumours of human germ cells.
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Affiliation(s)
- R H van Schaik
- Department of Endocrinology & Reproduction, Erasmus University Rotterdam, The Netherlands
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Michael Kettel L, DePaolo LV, Morales AJ, Apter D, Ling N, Yen SS. Circulating levels of follistatin from puberty to menopause*†*Supported by the National Institute of Child Health and Human Development Center grant HD-12303-17; the University of California, San Diego General Clinical Research Center, National Institute of Health Division of Research Resources grant M01 00827, Bethesda, Maryland; and in part by the Clayton Foundation for Research, California Division, La Jolla, California.†Presented in part at the 39th Annual Meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 18 to 21, 1992. Fertil Steril 1996. [DOI: 10.1016/s0015-0282(16)58139-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Abstract
OBJECTIVE To review the available information regarding the polypeptide factors inhibin, activin, and follistatin in reproductive physiology. DESIGN The protein structure, tissue expression, regulation, and effects of these factors are outlined, with an emphasis on the reproductive tissues in both females and males. Although some information is only available in animal model systems, human data has been selected whenever possible. CONCLUSIONS Inhibin and activin are closely related peptides with opposing actions, whereas follistatin is a structurally unrelated peptide that may act indirectly through modulation of inhibin-activin effects. These three peptides are secreted in highest levels by the adult gonads; however, they are also present in a wide variety of reproductive and nonreproductive tissues where they are believed to exert local, tissue-specific effects. Within the reproductive system, these peptides play a role in the regulation of gonadotropin biosynthesis and secretion, ovarian and placental steroidogenesis, and oocyte and spermatogonial maturation.
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Affiliation(s)
- L M Halvorson
- Department of Obstetrics and Gynecology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Coffin JD, Florkiewicz RZ, Neumann J, Mort-Hopkins T, Dorn GW, Lightfoot P, German R, Howles PN, Kier A, O'Toole BA. Abnormal bone growth and selective translational regulation in basic fibroblast growth factor (FGF-2) transgenic mice. Mol Biol Cell 1995; 6:1861-73. [PMID: 8590811 PMCID: PMC301338 DOI: 10.1091/mbc.6.12.1861] [Citation(s) in RCA: 252] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Basic fibroblast growth factor (FGF-2) is a pleiotropic growth factor detected in many different cells and tissues. Normally synthesized at low levels, FGF-2 is elevated in various pathologies, most notably in cancer and injury repair. To investigate the effects of elevated FGF-2, the human full-length cDNA was expressed in transgenic mice under control of a phosphoglycerate kinase promoter. Overexpression of FGF-2 caused a variety of skeletal malformations including shortening and flattening of long bones and moderate macrocephaly. Comparison by Western blot of FGF-2 transgenic mice to nontransgenic littermates showed expression of human FGF-2 protein in all major organs and tissues examined including brain, heart, lung, liver, kidney, spleen, and skeletal muscle; however, different molar ratios of FGF-2 protein isoforms were observed between different organs and tissues. Some tissues preferentially synthesize larger isoforms of FGF-2 while other tissues produce predominantly smaller 18-kDa FGF-2. Translation of the high molecular weight isoforms initiates from unconventional CUG codons and translation of the 18-kDa isoform initiates from an AUG codon in the FGF-2 mRNA. Thus the Western blot data from the FGF-2 transgenic mice suggest that tissue-specific expression of FGF-2 isoforms is regulated translationally.
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Affiliation(s)
- J D Coffin
- Department of Cell Biology, Scripps Research Institute, La Jolla, CA 92121, USA
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Affiliation(s)
- J Schwartz
- Department of Obstetrics and Gynecology, Bowman Gray School of Medicine Winston-Salem, North Carolina 27157
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