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Koklič T, Hrovat A, Guixà-González R, Rodríguez-Espigares I, Navio D, Frangež R, Uršič M, Kubale V, Plemenitaš A, Selent J, Šentjurc M, Vrecl M. Electron Paramagnetic Resonance Gives Evidence for the Presence of Type 1 Gonadotropin-Releasing Hormone Receptor (GnRH-R) in Subdomains of Lipid Rafts. Molecules 2021; 26:molecules26040973. [PMID: 33673080 PMCID: PMC7918721 DOI: 10.3390/molecules26040973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/02/2021] [Accepted: 02/08/2021] [Indexed: 11/16/2022] Open
Abstract
This study investigated the effect of type 1 gonadotropin releasing hormone receptor (GnRH-R) localization within lipid rafts on the properties of plasma membrane (PM) nanodomain structure. Confocal microscopy revealed colocalization of PM-localized GnRH-R with GM1-enriched raft-like PM subdomains. Electron paramagnetic resonance spectroscopy (EPR) of a membrane-partitioned spin probe was then used to study PM fluidity of immortalized pituitary gonadotrope cell line αT3-1 and HEK-293 cells stably expressing GnRH-R and compared it with their corresponding controls (αT4 and HEK-293 cells). Computer-assisted interpretation of EPR spectra revealed three modes of spin probe movement reflecting the properties of three types of PM nanodomains. Domains with an intermediate order parameter (domain 2) were the most affected by the presence of the GnRH-Rs, which increased PM ordering (order parameter (S)) and rotational mobility of PM lipids (decreased rotational correlation time (τc)). Depletion of cholesterol by methyl-β-cyclodextrin (methyl-β-CD) inhibited agonist-induced GnRH-R internalization and intracellular Ca2+ activity and resulted in an overall reduction in PM order; an observation further supported by molecular dynamics (MD) simulations of model membrane systems. This study provides evidence that GnRH-R PM localization may be related to a subdomain of lipid rafts that has lower PM ordering, suggesting lateral heterogeneity within lipid raft domains.
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Affiliation(s)
- Tilen Koklič
- Laboratory of Biophysics, Department of Condensed Matter Physics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia; (T.K.); (M.Š.)
| | - Alenka Hrovat
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Ramon Guixà-González
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
- Laboratory of Biomolecular Research, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
- Condensed Matter Theory Group, PSI, 5232 Villigen, Switzerland
| | - Ismael Rodríguez-Espigares
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Damaris Navio
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Robert Frangež
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Matjaž Uršič
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Valentina Kubale
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Ana Plemenitaš
- Faculty of Medicine, Institute of Biochemistry and Molecular Genetics, University of Ljubljana, 1000 Ljubljana, Slovenia;
| | - Jana Selent
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Marjeta Šentjurc
- Laboratory of Biophysics, Department of Condensed Matter Physics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia; (T.K.); (M.Š.)
| | - Milka Vrecl
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
- Correspondence: ; Tel.: +386-1-477-9118
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Phang YL, Soga T, Kitahashi T, Parhar IS. Cloning and functional expression of novel cholesterol transporters ABCG1 and ABCG4 in gonadotropin-releasing hormone neurons of the tilapia. Neuroscience 2011; 203:39-49. [PMID: 22198513 DOI: 10.1016/j.neuroscience.2011.12.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 12/07/2011] [Accepted: 12/09/2011] [Indexed: 10/14/2022]
Abstract
In addition to reproduction, gonadotropin-releasing hormone (GnRH) has been postulated to control cholesterol metabolism via cholesterol transport, which is carried out partly by the members of ATP-binding cassette (ABC) transporters G1 (ABCG1) and G4 (ABCG4). However, there is yet to be evidence demonstrating the relationship between these transporters with reference to GnRH neurons. In the present study, we cloned two ABCG1 messenger RNA (mRNA) variants and one ABCG4 mRNA and examined their expression in the brain including GnRH neurons (GnRH1, GnRH2, and GnRH3) in the cichlid tilapia (Oreochromis niloticus). Comparison of nucleotide sequences of the tilapia ABCG1 and ABCG4 with that of other fish species showed that both of these genes are evolutionarily conserved among fishes. ABCG1 and ABCG4 were shown to have high mRNA expressions in the CNS, pituitary, and gonads. In the brain, real-time polymerase chain reaction (PCR) showed that ABCG4 mRNA was higher than ABCG1a in all brain regions including the olfactory bulb (ABCG1=13.34, ABCG4=6796.35; P<0.001), dorsal telencephalon (ABCG1=8.64, ABCG4=10149.13; P=0.001), optic tectum (ABCG1=22.12, ABCG4=13931.04; P<0.01), cerebellum (ABCG1=8.68, ABCG4=12382.90; P<0.01), and preoptic area-midbrain-hypothalamus (ABCG1=21.36, ABCG4=13255.41; P=0.001). Similarly, although ABCG1 mRNA level is much higher in the pituitary compared with the brain, it was still significantly lower compared with ABCG4 (ABCG1=337.73, ABCG4=1157.87; P=0.01). The differential pattern of expression of ABCG1 and ABCG4 in the brain versus pituitary suggests that the two transporters are regulated by different mechanisms. Furthermore, ABCG1 and ABCG4 mRNA expressions were found in all three types of laser-captured GnRH neurons with highly similar percentage of expressions, suggesting that cholesterol efflux from GnRH neurons may require heterodimerization of both ABCG1 and ABCG4.
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Affiliation(s)
- Y L Phang
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Sunway Campus, Jalan Lagoon Selatan, Bandar Sunway, 46150 Petaling Jaya, Selangor, Malaysia
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Abstract
The synthesis and secretion of the gonadotropic hormones involves coordination of signal transduction, gene expression, protein translation, post-translational folding and modification and finally secretion. The production of biologically active gonadotropin thus requires appropriately folded and glycosylated subunits that assemble to form the heterodimeric hormone. Here we overview recent literature on regulation of gonadotropin subunit gene expression and current understanding of the assembly and secretion of biologically active gonadotropic hormones. Finally, we discuss the therapeutic potential of understanding glycosylation function towards designing new forms of gonadotropins based on observations of physiologically relevant parameters such as age related glycosylation changes.
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Affiliation(s)
- George R Bousfield
- Department of Biological Sciences, Wichita State University, Wichita, KS, USA.
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Pearl CA, Jablonka-Shariff A, Boime I. Rerouting of a follicle-stimulating hormone analog to the regulated secretory pathway. Endocrinology 2010; 151:388-93. [PMID: 19887562 PMCID: PMC2803143 DOI: 10.1210/en.2009-0939] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
LH and FSH are produced by the same gonadotrope cells of the anterior pituitary but differ in their mode of secretion. This coordinated secretion of LH and FSH is essential for normal follicular development and ovulation in females and for spermatogenesis in males. The structural signals encoded in the LH and FSH subunits that govern the intracellular sorting of LH through the regulated secretory pathway and FSH through the constitutive pathway are largely unknown. Our laboratory recently identified the seven amino acid carboxy tail of LH beta as a sorting signal for LH in GH(3) cells. Here we compared the morphological features of GH(3) cells expressing an FSH analog containing the heptapeptide (FL7AA) with wild-type FSH using confocal microscopy. These experiments were performed to develop a rerouting model for examining structure-function links between secretion pathways of FSH/LH and their biological action. Both FSH- and LH-expressing cells exhibit a fluorescence pattern of randomly dispersed cytoplasmic puncta. FL7AA expressing cells have more intracellular accumulation compared with wild-type FSH and display a unique halo pattern of fluorescence near the plasma membrane. Such a pattern was not observed in cells expressing FSH or LH. Our results demonstrate that this FSH analog containing the carboxy heptapeptide of LH beta is rerouted to the regulated secretory pathway in GH(3) cells. This rerouted gonadotropin provides a unique model to study the trafficking, regulation, and function of LH and FSH.
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Affiliation(s)
- Christopher A Pearl
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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