1
|
Newton CL, Anderson RC, Kreuchwig A, Krause G, Katz AA, Millar RP. Rescue of Function of Mutant Luteinising Hormone Receptors with Deficiencies in Cell Surface Expression, Hormone Binding, and Hormone Signalling. Neuroendocrinology 2021; 111:451-464. [PMID: 32316022 DOI: 10.1159/000508000] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 04/18/2020] [Indexed: 11/19/2022]
Abstract
INTRODUCTION G protein-coupled receptor (GPCR) mutations are implicated in many diseases. Most inactivating mutations cause receptor misfolding and prevent trafficking to the plasma membrane. Pharmacological chaperones can "rescue" cell surface expression of such mutants, presumably by stabilising correct folding of the nascent protein. OBJECTIVE Here we examine the scope of intracellularly retained luteinising hormone receptor (LHR) mutants that can be "rescued" by the pharmacological chaperone LHR-Chap, and whether this allosteric agonist can also restore the function of mutant LHRs with deficiencies in hormone binding or hormone-induced signalling. METHODS Mutant LHRs were expressed in HEK 293-T cells. Cell surface expression/localisation, hormone binding, and hCG/LHR-Chap signalling were determined by ELISA, radioligand binding, and inositol phosphate accumulation assays, respectively. Molecular modelling predicted LHR-Chap interactions. RESULTS LHR-Chap increased cell surface expression of a subset of retained mutants located in transmembrane helices predicted to be stabilised by LHR-Chap binding. For 3 (T4613.47I, L5024.61P, and S6167.46Y) hCG-responsiveness was increased following treatment. LHRs with mutations in the hormone-binding site (C131ECDR and I152ECDT) or in the hinge region (E354HingeK) had good cell surface expression but poor response to hormone stimulation, yet were responsive to allosteric activation by LHR-Chap. CONCLUSIONS LHR-Chap, in addition to rescuing cell surface expression of intracellularly retained LHR mutants, can rescue function in mutant receptors with binding and signalling deficiencies that have normal cell surface expression. This demonstration of rescue of multiple elements of LHR dysfunction arising from inactivating mutations offers exceptional potential for treating patients with diseases arising from GPCR mutations in general.
Collapse
Affiliation(s)
- Claire Louise Newton
- Centre for Neuroendocrinology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa,
- Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa,
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom,
| | - Ross Calley Anderson
- Centre for Neuroendocrinology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Annika Kreuchwig
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Gerd Krause
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Arieh Anthony Katz
- UCT Receptor Biology Research Unit and SAMRC Gynaecology Cancer Research Centre, Department of Integrative Biomedical Sciences and Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Robert Peter Millar
- Centre for Neuroendocrinology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| |
Collapse
|
2
|
Martínez-Hernández J, Seco-Rovira V, Beltrán-Frutos E, Ferrer C, Serrano-Sánchez MI, Pastor LM. Lectin-binding pattern of glycoconjugates during spontaneous testicular recrudescence in Syrian hamster (Mesocricetus auratus) after exposure to short photoperiod. Andrologia 2018; 51:e13148. [PMID: 30246471 DOI: 10.1111/and.13148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/26/2018] [Accepted: 08/21/2018] [Indexed: 01/19/2023] Open
Abstract
Lectin histochemistry was used to characterise glycoconjugates and cellular apoptosis in the seminiferous epithelium and interstitium of hamster testis during spontaneous recrudescence. An increase in the LTA lectin affinity was observed in spermatids in the Golgi phase. An increase in labelling of PNA and Con-A lectin in acrosome of spermatids (acrosome phase) as well as increased labelling with Con-A in spermatids (cap phase) was observed. Spermatocytes showed decreased affinity with PNA and AAA lectins and an increase in positivity for LTA and GNA lectins. Spermatogonia showed a slight decrease in positivity to WGA and an increase in labelling with Con-A and a decreased affinity for the AAA lectin. At the end of recrudescence, all these germinal cells showed a similar pattern to the control. The Sertoli cells showed a gradual decrease in labelling with the GNA lectin and the Leydig cells an increase in labelling with Con-A and GNA. Particularly unusual was the observation of apoptotic spermatocytes and spermatids positive for PNA, GNA, AAA and Con-A, together with spermatocytes positive to LTA. In conclusion, the normal lectin pattern is recovered during testis recrudescence and germ cell apoptotic activity is low, as is observed by specific lectins for germ cells in apoptosis.
Collapse
Affiliation(s)
- Jesús Martínez-Hernández
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| | - Vicente Seco-Rovira
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| | - Ester Beltrán-Frutos
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| | - Concepción Ferrer
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| | - María Isabel Serrano-Sánchez
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| | - Luis Miguel Pastor
- Department of Cell Biology and Histology, Medical School, IMIB-Arrixaca, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, Murcia, Spain
| |
Collapse
|
3
|
Ulloa-Aguirre A, Zariñán T, Gutiérrez-Sagal R, Dias JA. Intracellular Trafficking of Gonadotropin Receptors in Health and Disease. Handb Exp Pharmacol 2018; 245:1-39. [PMID: 29063275 DOI: 10.1007/164_2017_49] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Gonadotropin receptors belong to the highly conserved subfamily of the G protein-coupled receptor (GPCR) superfamily, the so-called Rhodopsin-like family (class A), which is the largest class of GPCRs and currently a major drug target. Both the follicle-stimulating hormone receptor (FSHR) and the luteinizing hormone/chorionic gonadotropin hormone receptor (LHCGR) are mainly located in the gonads where they play key functions associated to essential reproductive functions. As any other protein, gonadotropin receptors must be properly folded into a mature tertiary conformation compatible with quaternary assembly and endoplasmic reticulum export to the cell surface plasma membrane. Several primary and secondary structural features, including presence of particular amino acid residues and short motifs and in addition, posttranslational modifications, regulate intracellular trafficking of gonadotropin receptors to the plasma membrane as well as internalization and recycling of the receptor back to the cell surface after activation by agonist. Inactivating mutations of gonadotropin receptors may derive from receptor misfolding and lead to absent or reduced plasma membrane expression of the altered receptor, thereby manifesting an array of phenotypical abnormalities mostly characterized by reproductive failure and/or abnormal or absence of development of secondary sex characteristics. In this chapter we review the structural requirements necessary for intracellular trafficking of the gonadotropin receptors, and describe how mutations in these receptors may lead to receptor misfolding and disease in humans.
Collapse
Affiliation(s)
- Alfredo Ulloa-Aguirre
- Red de Apoyo a la Investigación (RAI), Universidad Nacional Autónoma de México-Instituto Nacional de Ciencias Médicas y Nutrición SZ, Vasco de Quiroga 15, Tlalpan, Mexico City, 14000, Mexico.
| | - Teresa Zariñán
- Red de Apoyo a la Investigación (RAI), Universidad Nacional Autónoma de México-Instituto Nacional de Ciencias Médicas y Nutrición SZ, Vasco de Quiroga 15, Tlalpan, Mexico City, 14000, Mexico
| | - Rubén Gutiérrez-Sagal
- Red de Apoyo a la Investigación (RAI), Universidad Nacional Autónoma de México-Instituto Nacional de Ciencias Médicas y Nutrición SZ, Vasco de Quiroga 15, Tlalpan, Mexico City, 14000, Mexico
| | - James A Dias
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, USA
| |
Collapse
|
4
|
Chen CC, Chen CW, Lin PH, Chou JC, Weng TC, Jian CY, Hu S, Lai WH, Lieu FK, Wang SW, Wang PS. Interactive Effect of Corticosterone and Lactate on Regulation of Testosterone Production in Rat Leydig Cells. J Cell Physiol 2017; 232:2135-2144. [PMID: 27886378 DOI: 10.1002/jcp.25700] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 11/21/2016] [Indexed: 11/11/2022]
Abstract
The increasing intensity of exercise enhanced corticosterone and lactate production in both humans and rodents. Our previous studies also demonstrated that lactate could stimulate testosterone production in vivo and in vitro. However, the production of testosterone in response to combined corticosterone and lactate on Leydig cells, and underlying molecular mechanisms are remained unclear. This study investigated the changes in testosterone levels of Leydig cells upon exposure to lactate, corticosterone or combination of both, and revealed the detailed mechanisms. Leydig cells were isolated from rat testes, and treated with different concentrations of lactate (2.5-20 mM), cortiosterone (10-9 -10-4 M) and lactate plus corticosterone. The production of testosterone were assayed by radioimmunoassay, and the key molecular proteins, including luteinizing hormone receptor (LHR), protein kinase A (PKA), steroidogenic acute regulatory protein (StAR), and cholesterol P450 side-chain cleavage enzyme (P450scc) involved in testosterone production were performed by Western blot. Results showed that testosterone levels were significantly increased with lactate, while decresed with corticosterone and lactate plus corticosterone treatment. Protein expressions of LHR and P450scc were upregulated with lactate treatment. However, PKA and P450scc were downregulated by lactate plus corticosterone treatment. This downregulation was followed by decreased testoterone levels in Leydig cells. Furthermore, acetylated cAMP, which activates testosterone production was increased with lactate, but not altered by conrtiosterone. Our findings conclude that corticosterone may interfere with lactate, and restrict lactate-stimulated testosterone production in Leydig cells. J. Cell. Physiol. 232: 2135-2144, 2017. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Chih-Chieh Chen
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Chien-Wei Chen
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Po-Han Lin
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Jou-Chun Chou
- Medical Center of Aging Research, China Medical University Hospital, Taichung, Taiwan, Republic of China.,Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan, Republic of China
| | - Ting-Chun Weng
- Medical Center of Aging Research, China Medical University Hospital, Taichung, Taiwan, Republic of China
| | - Cai-Yun Jian
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Sindy Hu
- Aesthetic Medical Center, Department of Dermatology, Chang-Gung Memorial Hospital, Taoyuan, Taiwan, Republic of China.,Department of Medicine, College of Medicine, Chang-Gung University, Taoyuan, Taiwan, Republic of China
| | - Wei-Ho Lai
- Department of Rehabilitation, Cheng-Hsin General Hospital, Taipei, Taiwan, Republic of China
| | - Fu-Kong Lieu
- Department of Rehabilitation, Cheng-Hsin General Hospital, Taipei, Taiwan, Republic of China
| | - Shyi-Wu Wang
- Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan, Republic of China.,Department of Physiology and Pharmacology, College of Medicine, Chang-Gung University, Taoyuan, Taiwan, Republic of China
| | - Paulus S Wang
- Department of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China.,Medical Center of Aging Research, China Medical University Hospital, Taichung, Taiwan, Republic of China.,Department of Biotechnology, College of Health Science, Asia University, Taichung, Taiwan, Republic of China.,Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China
| |
Collapse
|
5
|
Caro LN, Li Z, Balo AR, Van Eps N, Rini JM, Ernst OP. Rapid and facile recombinant expression of bovine rhodopsin in HEK293S GnTI(-) cells using a PiggyBac inducible system. Methods Enzymol 2015; 556:307-30. [PMID: 25857788 DOI: 10.1016/bs.mie.2015.01.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Rhodopsin is a class A G protein-coupled receptor (GPCR) that provides important insights into the structure and function of the GPCR superfamily. Bovine rhodopsin is widely used as a model for GPCRs and was the first GPCR whose X-ray crystal structure was solved. One of the advantages of rhodopsin is that it is abundant in native tissue, and as a result, milligram quantities can be purified from the retinal rod cells of bovine eyes. Nonetheless, the study of GPCR conformation and dynamics, e.g., by electron paramagnetic resonance or (19)F nuclear magnetic resonance spectroscopy, typically requires mutagenesis to enable site-directed labeling of the protein. Mutations are also of great importance as they can stabilize the receptor and can be necessary to study different receptor conformations. Recombinant production of rhodopsins for biophysical studies has been achieved in different systems, including mammalian, insect, and yeast cells in culture, and from Drosophila melanogaster and Caenorhabditis elegans tissue. The piggyBac (PB) transposon system is used for gene delivery into a variety of cell types (e.g., HEK293 and CHO cells, fibroblasts, stem cells) and living organisms (e.g., honeybees, pigs, chicken, mice). Recently, the PB transposon has been described as an efficient tool for inducible protein expression in HEK293T and HEK293S N-acetylglucosaminyltransferase I-deficient (GnTI(-)) cells. This chapter describes a protocol for using the PB-based system for inducible expression of bovine rhodopsin in HEK293S GnTI(-) cells. Using this protocol, we expressed and purified 26 rhodopsin mutants to be used for site-directed spin labeling.
Collapse
Affiliation(s)
- Lydia N Caro
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Zhijie Li
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Aidin R Balo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Ned Van Eps
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - James M Rini
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
| | - Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
| |
Collapse
|
6
|
Xu H, Chen H, Li J, Zhao Y, Ghishan FK. Disruption of NHE8 expression impairs Leydig cell function in the testes. Am J Physiol Cell Physiol 2014; 308:C330-8. [PMID: 25472965 DOI: 10.1152/ajpcell.00289.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Multiple sodium/hydrogen exchanger (NHE) isoforms are expressed in the testes, and they play various roles in cell volume regulation, intracellular pH regulation, and fluid absorption. NHE8, the most recently characterized NHE family member, is detected in the Leydig cells in humans and mice in great abundance by immunohistochemistry in the current study. Male mice lacking NHE8 expression were infertile. Despite having intact male reproductive organs, male NHE8-/- mice have smaller testes and lacked spermatozoon in the seminiferous tubules and the epididymis. At the age of 39 wk, few spermogonia were seen in the testis in NHE8-/- mice. Although male NHE8-/- mice have normal serum levels of luteinizing hormone and follicle-stimulating hormone, serum testosterone level was significantly reduced. These mice have decreased expression of luteinizing hormone receptor in the testes. In NHE8 small-interfering RNA-transfected mouse Leydig cells (MLTC-1), silencing of NHE8 decreased the expression of luteinizing hormone receptor by ∼70%. Moreover, loss of NHE8 function in Leydig cells resulted in disorganized luteinizing hormone receptor membrane distribution. Therefore, male infertility in NHE8-/- mice is at least partially due to the disruption of luteinizing hormone receptor distribution and consequent low testosterone production, which leads to Sertoli cell dysfunction. Our work identified a novel role of NHE8 in male fertility through its effect on modifying luteinizing hormone receptor function.
Collapse
Affiliation(s)
- Hua Xu
- Department of Pediatrics, Steel Children's Research Center, The University of Arizona, Tucson, Arizona
| | - Huacong Chen
- Department of Pediatrics, Steel Children's Research Center, The University of Arizona, Tucson, Arizona
| | - Jing Li
- Department of Pediatrics, Steel Children's Research Center, The University of Arizona, Tucson, Arizona
| | - Yang Zhao
- Department of Pediatrics, Steel Children's Research Center, The University of Arizona, Tucson, Arizona
| | - Fayez K Ghishan
- Department of Pediatrics, Steel Children's Research Center, The University of Arizona, Tucson, Arizona
| |
Collapse
|
7
|
The additional N-glycosylation site of the equine LH/CG receptor is not responsible for the limited cyclic AMP pathway activation by equine chorionic gonadotropin relative to luteinizing hormone. Reprod Biol 2012; 11:157-64. [PMID: 21804636 DOI: 10.1016/s1642-431x(12)60052-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In order to investigate the role of the unique seventh N23-glycosylation site of the equine LH/CG receptor (eLHCGR) in the cAMP pathway activation, COS-7 cells were transiently transfected with either the wild-type or the mutant eLHCGR(N23Q) cDNA and challenged with porcine LH and eCG for cAMP production. We showed that the N23-glycosylation site of the eLHCGR is not required for the functional coupling of the receptor with the cAMP pathway and is not responsible for the limited potency of eCG relative to pLH to activate this receptor.
Collapse
|
8
|
Abreu AP, Noel SD, Xu S, Carroll RS, Latronico AC, Kaiser UB. Evidence of the importance of the first intracellular loop of prokineticin receptor 2 in receptor function. Mol Endocrinol 2012; 26:1417-27. [PMID: 22745195 DOI: 10.1210/me.2012-1102] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Prokineticin receptors (PROKR) are G protein-coupled receptors (GPCR) that regulate diverse biological processes, including olfactory bulb neurogenesis and GnRH neuronal migration. Mutations in PROKR2 have been described in patients with varying degrees of GnRH deficiency and are located in diverse functional domains of the receptor. Our goal was to determine whether variants in the first intracellular loop (ICL1) of PROKR2 (R80C, R85C, and R85H) identified in patients with hypogonadotropic hypogonadism interfere with receptor function and to elucidate the mechanisms of these effects. Because of structural homology among GPCR, clarification of the role of ICL1 in PROKR2 activity may contribute to a better understanding of this domain across other GPCR. The effects of the ICL1 PROKR2 mutations on activation of signal transduction pathways, ligand binding, and receptor expression were evaluated. Our results indicated that the R85C and R85H PROKR2 mutations interfere only modestly with receptor function, whereas the R80C PROKR2 mutation leads to a marked reduction in receptor activity. Cotransfection of wild-type (WT) and R80C PROKR2 showed that the R80C mutant could exert a dominant negative effect on WT PROKR2 in vitro by interfering with WT receptor expression. In summary, we have shown the importance of Arg80 in ICL1 for PROKR2 expression and demonstrate that R80C PROKR2 exerts a dominant negative effect on WT PROKR2.
Collapse
Affiliation(s)
- Ana Paula Abreu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | | | | | | | | | | |
Collapse
|
9
|
Skropeta D. The effect of individual N-glycans on enzyme activity. Bioorg Med Chem 2009; 17:2645-53. [PMID: 19285412 DOI: 10.1016/j.bmc.2009.02.037] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Revised: 02/11/2009] [Accepted: 02/13/2009] [Indexed: 01/08/2023]
Abstract
In a series of investigations, N-glycosylation has proven to be a key determinant of enzyme secretion, activity, binding affinity and substrate specificity, enabling a protein to fine-tune its activity. In the majority of cases elimination of all putative N-glycosylation sites of an enzyme results in significantly reduced protein secretion levels, while removal of individual N-glycosylation sites often leads to the expression of active enzymes showing markedly reduced catalytic activity, with the decreased activity often commensurate with the number of glycosylation sites available, and the fully deglycosylated enzymes showing only minimal activity relative to their glycosylated counterparts. On the other hand, several cases have also recently emerged where deglycosylation of an enzyme results in significantly increased catalytic activity, binding affinity and altered substrate specificity, highlighting the very unique and diverse roles that individual N-glycans play in regulating enzyme function.
Collapse
Affiliation(s)
- Danielle Skropeta
- School of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia.
| |
Collapse
|
10
|
Yan Y, Scott DJ, Wilkinson TN, Ji J, Tregear GW, Bathgate RAD. Identification of the N-linked glycosylation sites of the human relaxin receptor and effect of glycosylation on receptor function. Biochemistry 2008; 47:6953-68. [PMID: 18533687 DOI: 10.1021/bi800535b] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The relaxin receptor, RXFP1, is a member of the leucine-rich repeat-containing G-protein-coupled receptor (LGR) family. These receptors are characterized by a large extracellular ectodomain containing leucine-rich repeats which contain the primary ligand binding site. RXFP1 contains six putative Asn-linked glycosylation sites in the ectodomain at positions Asn-14, Asn-105, Asn-242, Asn-250, Asn-303, and Asn-346, which are highly conserved across species. N-Linked glycosylation is the most common post-translational modification of G-protein-coupled receptors, although its role in modulating receptor function differs. We herein investigate the actual N-linked glycosylation status of RXFP1 and the functional ramifications of these post-translational modifications. Site-directed mutagenesis was utilized to generate single- or multiple-glycosylation site mutants of FLAG-tagged human RXFP1 which were then transiently expressed in HEK-293T cells. Glycosylation status was analyzed by immunoprecipitation and Western blot and receptor function analyzed with an anti-FLAG ELISA, (33)P-H2 relaxin competition binding, and cAMP activity measurement. All of the potential N-glycosylation sites of RXFP1 were utilized in HEK-293T cells, and importantly, disruption of glycosylation at individual or combinations of double and triple sites had little effect on relaxin binding. However, combinations of glycosylation sites were required for cell surface expression and cAMP signaling. In particular, N-glycosylation at Asn-303 of RXFP1 was required for optimal intracellular cAMP signaling. Hence, as is the case for other LGR family members, N-glycosylation is essential for the transport of the receptor to the cell surface. Additionally, it is likely that glycosylation is also essential for the conformational changes required for G-protein coupling and subsequent cAMP signaling.
Collapse
Affiliation(s)
- Y Yan
- Department of Biochemistry and Molecular Biology, College of Life Sciences, The National Laboratory of Protein Engineering and Plant Genetic Engineering, Peking University, Beijing 100871, PR China
| | | | | | | | | | | |
Collapse
|
11
|
Carlson HE. Human adrenal cortex hyperfunction due to LH/hCG. Mol Cell Endocrinol 2007; 269:46-50. [PMID: 17363138 DOI: 10.1016/j.mce.2006.06.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2006] [Revised: 06/30/2006] [Accepted: 06/30/2006] [Indexed: 11/17/2022]
Abstract
Adrenal cortex hyperfunction may occasionally be due to stimulation of steroid hormone production by LH/hCG. The recent demonstration of the LH/hCG receptor in a variety of normal and abnormal human adrenal tissues has provided a novel explanation for these clinical observations and offers the possibility of spontaneous remission (as in pregnancy-related hyperfunction) or effective treatment with GnRH-agonists (to down-regulate LH secretion in menopausal patients). Involvement of adrenal LH/hCG receptors should be considered in pregnant or post-menopausal patients with ACTH-independent Cushing's syndrome or androgen excess. Additional investigations are needed to better define the role of the LH/hCG receptor in the normal adult and fetal human adrenal and to understand how this system is excessively activated in rare cases of human disease.
Collapse
Affiliation(s)
- Harold E Carlson
- Department of Medicine, Endocrinology Division, HSC T15-060, Stony Brook University, Stony Brook, NY 11794-8154, United States.
| |
Collapse
|
12
|
Banerjee S, Smallwood A, Chambers AE, Papageorghiou A, Loosfelt H, Spencer K, Campbell S, Nicolaides K. A link between high serum levels of human chorionic gonadotrophin and chorionic expression of its mature functional receptor (LHCGR) in Down's syndrome pregnancies. Reprod Biol Endocrinol 2005; 3:25. [PMID: 15969756 PMCID: PMC1190215 DOI: 10.1186/1477-7827-3-25] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 06/21/2005] [Indexed: 11/26/2022] Open
Abstract
Human chorionic gonadotrophin (hCG) is released from placental trophoblasts and is involved in establishing pregnancy by maintaining progesterone secretion from the corpus luteum. Serum hCG is detected in the maternal circulation within the first 2-3 wks of gestation and peaks at the end of the first trimester before declining. In Down's syndrome (DS) pregnancies, serum hCG remains significantly high compared to gestation age-matched uncompromised pregnancies. It has been proposed that increased serum hCG levels could be due to transcriptional hyper-activation of the CGB (hCG beta) gene, or an increased half life of glycosylated hCG hormone, or both. Another possibility is that serum hCG levels remain high due to reduced availability of the hormone's cognate receptor, LHCGR, leading to lack of hormone utilization. We have tested this hypothesis by quantifying the expression of the hCG beta (CGB) RNA, LHCGR RNA and LHCGR proteins in chorionic villous samples. We demonstrate that chorionic expression of hCG beta (CGB) mRNA directly correlates with high serum hCG levels. The steady-state synthesis of LHCGR mRNA (exons 1-5) in DS pregnancies was significantly higher than that of controls, but the expression of full-length LHCGR mRNA (exons 1-11) in DS was comparable to that of uncompromised pregnancies. However, the synthesis of high molecular weight mature LHCGR proteins was significantly reduced in DS compared to uncompromised pregnancies, suggesting a lack of utilization of circulating hCG in DS pregnancies.
Collapse
MESH Headings
- Animals
- Antibodies, Monoclonal/analysis
- Antibody Specificity
- Blotting, Western
- Chorionic Gonadotropin, beta Subunit, Human/blood
- Chorionic Gonadotropin, beta Subunit, Human/genetics
- Chorionic Gonadotropin, beta Subunit, Human/metabolism
- Chorionic Villi/metabolism
- Down Syndrome/embryology
- Down Syndrome/genetics
- Female
- Glycoprotein Hormones, alpha Subunit/blood
- Glycoprotein Hormones, alpha Subunit/genetics
- Glycoprotein Hormones, alpha Subunit/metabolism
- Humans
- Mice
- Pregnancy
- Protein Isoforms/metabolism
- RNA, Messenger/metabolism
- Receptors, LH/chemistry
- Receptors, LH/genetics
- Receptors, LH/metabolism
- Trisomy
Collapse
Affiliation(s)
- Subhasis Banerjee
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| | - Alan Smallwood
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| | - Anne E Chambers
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| | - Aris Papageorghiou
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| | - Hugues Loosfelt
- INSERM U135, Biochimie hormonale, CHU de Kremlin-Bicêtre, Bat Paul Broca, 3e niveau 78 avenue du général Leclerc, 94275 Le Kremlin-Bicêtre, France
| | - Kevin Spencer
- Endocrine Unit, Clinical Biochemistry Department, Harold Wood Hospital, Gubbins Lane, Romford RM3 0BE, UK
| | - Stuart Campbell
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| | - Kypros Nicolaides
- Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 9RS, UK
| |
Collapse
|
13
|
Menon KMJ, Clouser CL, Nair AK. Gonadotropin receptors: role of post-translational modifications and post-transcriptional regulation. Endocrine 2005; 26:249-57. [PMID: 16034179 DOI: 10.1385/endo:26:3:249] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 05/02/2005] [Indexed: 11/11/2022]
Abstract
This review focuses on the post-translational modifications of LH and FSH receptors and recent studies on the regulation of LH receptor expression mediated by an RNA binding protein. Both LH and FSH receptors undergo extensive post-translational modifications. N-linked glycosylation occurs co-translationally and plays a role in the maturation and processing of the receptor, while palmitoylation is involved in receptor endocytosis and post-endocytic trafficking. A third type of post-translational modification is phosphorylation and its function has been reviewed. Finally, the regulation of LH receptor at the mRNA level by an RNA binding protein is discussed in the context of ovarian function.
Collapse
Affiliation(s)
- K M J Menon
- Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, 48109-0617, USA.
| | | | | |
Collapse
|