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Chang JP, Pemberton JG. Comparative aspects of GnRH-Stimulated signal transduction in the vertebrate pituitary - Contributions from teleost model systems. Mol Cell Endocrinol 2018; 463:142-167. [PMID: 28587765 DOI: 10.1016/j.mce.2017.06.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/31/2017] [Accepted: 06/01/2017] [Indexed: 02/07/2023]
Abstract
Gonadotropin-releasing hormone (GnRH) is a major regulator of reproduction through actions on pituitary gonadotropin release and synthesis. Although it is often thought that pituitary cells are exposed to only one GnRH, multiple GnRH forms are delivered to the pituitary of teleost fishes; interestingly this can include the cGnRH-II form usually thought to be non-hypophysiotropic. GnRHs can regulate other pituitary cell-types, both directly as well as indirectly, and multiple GnRH receptors (GnRHRs) may also be expressed in the pituitary, and even within a single pituitary cell-type. Literature on the differential actions of native GnRH isoforms in primary pituitary cells is largely derived from teleost fishes. This review will outline the diversity and complexity of GnRH-GnRHR signal transduction found within vertebrate gonadotropes as well as extra-gonadotropic sites with special emphasis on comparative studies from fish models. The implications that GnRHR transduction mechanisms are GnRH isoform-, function-, and cell-specific are also discussed.
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Affiliation(s)
- John P Chang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Joshua G Pemberton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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Chen D, Yang W, Han S, Yang H, Cen X, Liu J, Zhang L, Zhang W. A Type IIb, but Not Type IIa, GnRH Receptor Mediates GnRH-Induced Release of Growth Hormone in the Ricefield Eel. Front Endocrinol (Lausanne) 2018; 9:721. [PMID: 30555419 PMCID: PMC6283897 DOI: 10.3389/fendo.2018.00721] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Accepted: 11/14/2018] [Indexed: 12/22/2022] Open
Abstract
Multiple gonadotropin-releasing hormone receptors (GnRHRs) are present in vertebrates, but their differential physiological relevances remain to be clarified. In the present study, we identified three GnRH ligands GnRH1 (pjGnRH), GnRH2 (cGnRH-II), and GnRH3 (sGnRH) from the brain, and two GnRH receptors GnRHR1 (GnRHR IIa) and GnRHR2 (GnRHR IIb) from the pituitary of the ricefield eel Monopterus albus. GnRH1 and GnRH3 but not GnRH2 immunoreactive neurons were detected in the pre-optic area, hypothalamus, and pituitary, suggesting that GnRH1 and GnRH3 may exert hypophysiotropic roles in ricefield eels. gnrhr1 mRNA was mainly detected in the pituitary, whereas gnrhr2 mRNA broadly in tissues of both females and males. In the pituitary, GnRHR1 and GnRHR2 immunoreactive cells were differentially distributed, with GnRHR1 immunoreactive cells mainly in peripheral areas of the adenohypophysis whereas GnRHR2 immunoreactive cells in the multicellular layers of adenohypophysis adjacent to the neurohypophysis. Dual-label fluorescent immunostaining showed that GnRHR2 but not GnRHR1 was localized to somatotropes, and all somatotropes are GnRHR2-positive cells and vice versa at all stages examined. GnRH1 and GnRH3 were shown to stimulate growth hormone (Gh) release from primary culture of pituitary cells, and to decrease Gh contents in the pituitary of ricefield eels 12 h post injection. GnRH1 and GnRH3 stimulated Gh release probably via PLC/IP3/PKC and Ca2+ pathways. These results, as a whole, suggested that GnRHs may bind to GnRHR2 but not GnRHR1 to trigger Gh release in ricefield eels, and provided novel information on differential roles of multiple GnRH receptors in vertebrates.
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Affiliation(s)
- Dong Chen
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Wei Yang
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Shiying Han
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Huiyi Yang
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Xin Cen
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Jiang Liu
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Lihong Zhang
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
- *Correspondence: Lihong Zhang
| | - Weimin Zhang
- Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
- Guangdong Provincial Engineering Technology Research Center for Healthy Breeding of Important Economic Fish, Sun Yat-Sen University, Guangzhou, China
- Weimin Zhang
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Regazzo D, Losa M, Albiger NM, Terreni MR, Vazza G, Ceccato F, Emanuelli E, Denaro L, Scaroni C, Occhi G. The GIP/GIPR axis is functionally linked to GH-secretion increase in a significant proportion of gsp- somatotropinomas. Eur J Endocrinol 2017; 176:543-553. [PMID: 28179449 DOI: 10.1530/eje-16-0831] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 02/01/2017] [Accepted: 02/07/2017] [Indexed: 01/03/2023]
Abstract
OBJECTIVE Glucose-dependent insulinotropic polypeptide receptor (GIPR) overexpression has been recently described in a proportion of gsp- somatotropinomas and suggested to be associated with the paradoxical increase of GH (GH-PI) during an oral glucose load. DESIGN AND METHODS This study was aimed at linking the GIP/GIPR pathway to GH secretion in 25 somatotropinomas-derived primary cultures and correlating molecular with clinical features in acromegalic patients. Given the impairment of the GIP/GIPR axis in acromegaly, an additional aim was to assess the effect of GH/IGF-1 stimulation on GIP expression in the enteroendocrine cell line STC-1. RESULTS Nearly 80% of GIPR-expressing somatotropinomas, all of them negative for gsp mutations, show increased GH secretion upon GIP stimulation, higher sensitivity to Forskolin but not to somatostatin analogs. Besides increased frequency of GH-PI, GIPR overexpression does not appear to affect acromegalic patients' clinical features. In STC-1 cells transfected with GIP promoter-driven luciferase vector, IGF-1 but not GH induced dose-dependent increase in luciferase activity. CONCLUSIONS We demonstrate that GIPR mediates the GH-PI in a significant proportion of gsp- acromegalic patients. In these cases, the stimulatory effect of IGF-1 on GIP promoter support the hypothesis of a functional GH/IGF-1/GIP axis. Further studies based on larger cohorts and the development of a stable transgenic model with inducible GIPR overexpression targeted to pituitary somatotroph lineage will be mandatory to establish the real role of GIPR in the pathogenesis of somatotropinomas.
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Affiliation(s)
- D Regazzo
- Endocrinology DivisionDepartment of Medicine, Hospital/University of Padova, Padova, Italy
| | - M Losa
- Pituitary UnitDepartment of Neurosurgery
| | - N M Albiger
- Endocrinology DivisionDepartment of Medicine, Hospital/University of Padova, Padova, Italy
| | - M R Terreni
- Pathology UnitIstituto Scientifico San Raffaele, Università Vita-Salute, Milano, Italy
| | - G Vazza
- Department of BiologyUniversity of Padova, Padova, Italy
| | - F Ceccato
- Endocrinology DivisionDepartment of Medicine, Hospital/University of Padova, Padova, Italy
| | | | - L Denaro
- Department of NeuroscienceHospital/University of Padova, Padova, Italy
| | - C Scaroni
- Endocrinology DivisionDepartment of Medicine, Hospital/University of Padova, Padova, Italy
| | - G Occhi
- Department of BiologyUniversity of Padova, Padova, Italy
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Mayr B, Buslei R, Theodoropoulou M, Stalla GK, Buchfelder M, Schöfl C. Molecular and functional properties of densely and sparsely granulated GH-producing pituitary adenomas. Eur J Endocrinol 2013; 169:391-400. [PMID: 23847328 DOI: 10.1530/eje-13-0134] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE GH-producing pituitary adenomas display two distinct morphological patterns of cytoplasmic GH-containing secretory granules, namely the densely and sparsely granulated somatotroph adenoma subtype. It is unknown whether these morphological variants reflect distinct pathophysiological entities at the molecular level. METHODS In 28 GH-producing adenoma tissues from a consecutive set of patients undergoing pituitary surgery for acromegaly, we studied the GH granulation pattern, the expression of somatostatin receptor subtypes (SSTR) as well as the calcium, cAMP and ZAC1 pathways in primary adenoma cell cultures. RESULTS The expression of GSP oncogene was similar between densely and sparsely granulated somatotroph adenoma cells. There were no differences in the calcium, cAMP and ZAC1 pathways as well as in their regulation by SSTR agonists. SSTR2 was exclusively expressed in densely but not in sparsely granulated tumours (membrane expression 86 vs 0%; cytoplasmic expression 67 vs 0%). By contrast, expression of SSTR5 was only found in sparsely but not in densely granulated somatotroph adenomas (membrane expression 29 vs 0%; cytoplasmic expression 57 vs 0%). CONCLUSIONS Our results indicate that different granulation patterns in GH-producing adenomas do not reflect differences in pathways and factors pivotal for somatotroph differentiation and function. In vitro, the vast majority of both densely and sparsely granulated tumour cells were responsive to SSTR activation at the molecular level. Sparsely granulated adenomas lacking SSTR2, but expressing SSTR5, might be responsive to novel SSTR agonists with increased affinity to SSTR5.
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Affiliation(s)
- Bernhard Mayr
- Division of Endocrinology and Diabetes, Department of Medicine I
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Knollman PE, Conn PM. Multiple G proteins compete for binding with the human gonadotropin releasing hormone receptor. Arch Biochem Biophys 2008; 477:92-7. [PMID: 18541137 DOI: 10.1016/j.abb.2008.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 05/13/2008] [Accepted: 05/18/2008] [Indexed: 01/05/2023]
Abstract
The GnRH receptor is coupled to G proteins of the families G(q) and G(11). G(q) and G(11) coupling leads to intracellular signaling through the phospholipase C pathway. GnRHR coupling to other G proteins is controversial. This study provides evidence that G protein families G(s), G(i), G(q) and G(11) complete for binding with the GnRHR. We quantified interactions of over-expressed G proteins with GnRHR by a competitive binding approach, using measurements of second messengers, IP and cAMP. Transient co-transfection of HEK293 cells with human WT GnRHR and with stimulatory and inhibitory G proteins (G(q), G(11) and G(s), G(i)) led to either production or inhibition of total inositol phosphate (IP) production, depending on the G protein that was over-expressed. Studies were conducted in different human (COS7, HeLa) and rodent-derived (CHO-K1, GH(3)) cell lines in order to confirm that G protein promiscuity observed with the GnRHR was not limited to a particular cell type.
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Affiliation(s)
- Paul E Knollman
- Divisions of Neuroscience and Reproductive Biology, ONPRC/OHSU, Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, Oregon 97006, USA
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Grottoli S, Gasco V, Broglio F, Baldelli R, Ragazzoni F, Gallenca F, Mainolfi A, Prodam F, Muccioli G, Ghigo E. Cortistatin-17 and somatostatin-14 display the same effects on growth hormone, prolactin, and insulin secretion in patients with acromegaly or prolactinoma. J Clin Endocrinol Metab 2006; 91:1595-9. [PMID: 16449338 DOI: 10.1210/jc.2005-1837] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Cortistatin binds all somatostatin receptor subtypes but also has particular central actions; moreover, a specific cortistatin receptor has also been discovered. OBJECTIVE We compared the endocrine effects of cortistatin-17 with those of somatostatin-14 in patients with acromegaly (ACRO) or prolactinoma (PRLOMA). Normal subjects (NS) were studied as control group. DESIGN All subjects underwent the following tests: 1) saline, 2) somatostatin-14 (2.0 microg/kg.h iv, 0-120 min) and 3) cortistatin-17 (2.0 microg/kg.h iv, 0-120 min) infusion. RESULTS Cortistatin-17 and somatostatin-14 inhibited GH secretion to the same extent in ACRO (P < 0.05) and NS (P < 0.01). Cortistatin-17 and somatostatin-14 inhibited PRL secretion in PRLOMA (P < 0.05), to some extent in ACRO (P value not significant), but not in NS. Insulin secretion was inhibited by both cortistatin-17 and somatostatin-14 to the same extent in all groups (P < 0.05). CONCLUSIONS Cortistatin-17 and somatostatin-14 display the same effects on GH, PRL, and insulin secretion in patients with ACRO or PRLOMA.
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Affiliation(s)
- S Grottoli
- Division of Endocrinology and Metabolism, Department of Internal Medicine, San Giovanni Battista-Molinette Hospital, Corso Dogliotti 14, 10126 Turin, Italy
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Kraus S, Naor Z, Seger R. Gonadotropin-releasing hormone in apoptosis of prostate cancer cells. Cancer Lett 2006; 234:109-23. [PMID: 16546667 DOI: 10.1016/j.canlet.2005.02.038] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Accepted: 02/28/2005] [Indexed: 10/25/2022]
Abstract
GnRH and its analogs (GnRH-a) are used extensively for the treatment of prostate cancer and other hormone-dependent diseases via the desensitization of pituitary gonadotropes, which consequently leads to the inhibition of gonadotropins, gonadal steroids and tumor growth. The actions of GnRH-a are mediated by the GnRH receptor (GnRHR) that is expressed in both the pituitary and extrapituitary sites, including normal tissues and tumors. Several studies have provided evidence that besides its pituitary effects, GnRH-a may exert direct anti-proliferative and apoptotic effects in tumor cells. These effects are mediated by the GnRHRs via signal transduction mechanisms that are distinct from the classical pituitary mechanisms. Here we describe the direct effects of GnRH-a on prostate cancer and other types of cancer. Interestingly, androgen ablation by GnRH-a is the main treatment for hormone-dependent prostate cancer. However, most of these tumors become eventually hormone-refractory, and are no longer sensitive to the GnRH-a-mediated reduction in androgen levels. Hence, the ability of GnRH-a to induce direct effects such as apoptosis may have large implications regarding the clinical use of GnRH-a. Therefore, an understanding of the cellular mechanisms involved in GnRH-a action may lead to better therapeutic modalities for the treatment of advanced prostate cancer and other malignancies.
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Affiliation(s)
- Sarah Kraus
- Department of Microbiology and Cancer Center, University of Virginia, Charlottesville, VA 22908, USA
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