101
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Dietrich JW, Landgrafe G, Fotiadou EH. TSH and Thyrotropic Agonists: Key Actors in Thyroid Homeostasis. J Thyroid Res 2012; 2012:351864. [PMID: 23365787 PMCID: PMC3544290 DOI: 10.1155/2012/351864] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 11/21/2012] [Indexed: 12/11/2022] Open
Abstract
This paper provides the reader with an overview of our current knowledge of hypothalamic-pituitary-thyroid feedback from a cybernetic standpoint. Over the past decades we have gained a plethora of information from biochemical, clinical, and epidemiological investigation, especially on the role of TSH and other thyrotropic agonists as critical components of this complex relationship. Integrating these data into a systems perspective delivers new insights into static and dynamic behaviour of thyroid homeostasis. Explicit usage of this information with mathematical methods promises to deliver a better understanding of thyrotropic feedback control and new options for personalised diagnosis of thyroid dysfunction and targeted therapy, also by permitting a new perspective on the conundrum of the TSH reference range.
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Affiliation(s)
- Johannes W. Dietrich
- Lab XU44, Medical Hospital I, Bergmannsheil University Hospitals, Ruhr University of Bochum (UK RUB), Bürkle-de-la-Camp-Platz 1, 44789 Bochum, NRW, Germany
| | - Gabi Landgrafe
- Lab XU44, Medical Hospital I, Bergmannsheil University Hospitals, Ruhr University of Bochum (UK RUB), Bürkle-de-la-Camp-Platz 1, 44789 Bochum, NRW, Germany
- Klinik für Allgemein- und Visceralchirurgie, Agaplesion Bethesda Krankenhaus Wuppertal gGmbH, Hainstraße 35, 42109 Wuppertal, NRW, Germany
| | - Elisavet H. Fotiadou
- Lab XU44, Medical Hospital I, Bergmannsheil University Hospitals, Ruhr University of Bochum (UK RUB), Bürkle-de-la-Camp-Platz 1, 44789 Bochum, NRW, Germany
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102
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Bockaert J. [G-protein coupled receptors. Nobel Prize 2012 for chemistry to Robert J. Lefkowitz and Brian Kobilka]. Med Sci (Paris) 2012; 28:1133-7. [PMID: 23290416 DOI: 10.1051/medsci/20122812026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The 2012 Nobel Prize for chemistry has been won by Robert J. Lefkowitz and Brian Kobilka for their work on G protein-coupled receptors (GPCRs). Those receptors (3% of human genome) evolutionary are derived from one 1 or 2 ancestors and are able to recognize external message as different as light, odorants, gustative molecules and intercellular messages such as hormones and neurotransmitters. They are targets of 30-40% of therapeutic drugs. Robert J. Lefkowitz has been one of the leaders of the field from more than 40 years and has built several key concepts of the domain. Brian Kobilka was successful, in 2007, in producing a crystal structure of the β2-adrenergic receptor. This paved the way for the production of a series of almost 50 GPCR crystal structures both in inactive and active forms.
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Affiliation(s)
- Joël Bockaert
- CNRS UMR 5203, Institut de génomique fonctionnelle, Inserm U661, Université de Montpellier 1 et 2, 34000 Montpellier, France.
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103
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Wise H. The roles played by highly truncated splice variants of G protein-coupled receptors. J Mol Signal 2012; 7:13. [PMID: 22938630 PMCID: PMC3477067 DOI: 10.1186/1750-2187-7-13] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/29/2012] [Indexed: 01/08/2023] Open
Abstract
Alternative splicing of G protein-coupled receptor (GPCR) genes greatly increases the total number of receptor isoforms which may be expressed in a cell-dependent and time-dependent manner. This increased diversity of cell signaling options caused by the generation of splice variants is further enhanced by receptor dimerization. When alternative splicing generates highly truncated GPCRs with less than seven transmembrane (TM) domains, the predominant effect in vitro is that of a dominant-negative mutation associated with the retention of the wild-type receptor in the endoplasmic reticulum (ER). For constitutively active (agonist-independent) GPCRs, their attenuated expression on the cell surface, and consequent decreased basal activity due to the dominant-negative effect of truncated splice variants, has pathological consequences. Truncated splice variants may conversely offer protection from disease when expression of co-receptors for binding of infectious agents to cells is attenuated due to ER retention of the wild-type co-receptor. In this review, we will see that GPCRs retained in the ER can still be functionally active but also that highly truncated GPCRs may also be functionally active. Although rare, some truncated splice variants still bind ligand and activate cell signaling responses. More importantly, by forming heterodimers with full-length GPCRs, some truncated splice variants also provide opportunities to generate receptor complexes with unique pharmacological properties. So, instead of assuming that highly truncated GPCRs are associated with faulty transcription processes, it is time to reassess their potential benefit to the host organism.
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Affiliation(s)
- Helen Wise
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China.
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104
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Sun Z, Runne C, Tang X, Lin F, Chen S. The Gβ3 splice variant associated with the C825T gene polymorphism is an unstable and functionally inactive protein. Cell Signal 2012; 24:2349-59. [PMID: 22940628 DOI: 10.1016/j.cellsig.2012.08.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 08/27/2012] [Indexed: 12/13/2022]
Abstract
A splice variant of Gβ3, termed Gβ3s, has been associated with the C825T polymorphism in the Gβ3 gene and linked with many human disorders. However, the biochemical properties and functionality of Gβ3s remain controversial. Here, using multidisciplinary approaches including co-immunoprecipitation analysis and bioluminescence resonance energy transfer (BRET) measurements, we showed that unlike Gβ3, Gβ3s failed to form complexes with either Gγ or Gα subunits. Moreover, using a mutant Gγ2 deficient in lipid modification to purify Gβ3s from Sf9 cells without the use of detergents, we further showed that the failure of Gβ3s to form dimers with Gγ was not due to the instability of the dimers in detergents, but rather, reflected the intrinsic properties of Gβ3s. Additional studies indicated that Gβ3s is unstable, and unable to localize properly to the plasma membrane and to activate diverse Gβγ effectors including PLCβ2/3, PI3Kγ, ERKs and the Rho guanine exchange factor (RhoGEF) PLEKHG2. Thus, these data suggest that the pathological effects of Gβ3 C825T polymorphism may result from the downregulation of Gβ3 function. However, we found that the chemokine SDF1α transmits signals primarily through Gβ1 and Gβ2, but not Gβ3, to regulate chemotaxis of several human lymphocytic cell lines, indicating the effects of Gβ3 C825T polymorphism are likely to be tissue and/or stimuli specific and its association with various disorders in different tissues should be interpreted with great caution.
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Affiliation(s)
- Zhizeng Sun
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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105
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Zoenen M, Urizar E, Swillens S, Vassart G, Costagliola S. Evidence for activity-regulated hormone-binding cooperativity across glycoprotein hormone receptor homomers. Nat Commun 2012; 3:1007. [DOI: 10.1038/ncomms1991] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 07/06/2012] [Indexed: 11/09/2022] Open
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106
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Bratton MR, Antoon JW, Duong BN, Frigo DE, Tilghman S, Collins-Burow BM, Elliott S, Tang Y, Melnik LI, Lai L, Alam J, Beckman BS, Hill SM, Rowan BG, McLachlan JA, Burow ME. Gαo potentiates estrogen receptor α activity via the ERK signaling pathway. J Endocrinol 2012; 214:45-54. [PMID: 22562654 PMCID: PMC3614348 DOI: 10.1530/joe-12-0097] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The estrogen receptor α (ERα) is a transcription factor that mediates the biological effects of 17β-estradiol (E(2)). ERα transcriptional activity is also regulated by cytoplasmic signaling cascades. Here, several Gα protein subunits were tested for their ability to regulate ERα activity. Reporter assays revealed that overexpression of a constitutively active Gα(o) protein subunit potentiated ERα activity in the absence and presence of E(2). Transient transfection of the human breast cancer cell line MCF-7 showed that Gα(o) augments the transcription of several ERα-regulated genes. Western blots of HEK293T cells transfected with ER±Gα(o) revealed that Gα(o) stimulated phosphorylation of ERK 1/2 and subsequently increased the phosphorylation of ERα on serine 118. In summary, our results show that Gα(o), through activation of the MAPK pathway, plays a role in the regulation of ERα activity.
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Affiliation(s)
- Melyssa R Bratton
- Section of Hematology and Medical Oncology, Department of Medicine, Tulane University, 1430 Tulane Avenue, SL-78, New Orleans, Louisiana 70112, USA
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107
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Cöster M, Wittkopf D, Kreuchwig A, Kleinau G, Thor D, Krause G, Schöneberg T. Using ortholog sequence data to predict the functional relevance of mutations in G‐protein‐coupled receptors. FASEB J 2012; 26:3273-81. [DOI: 10.1096/fj.12-203737] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Maxi Cöster
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | - Doreen Wittkopf
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | | | - Gunnar Kleinau
- Institute of Experimental Pediatric EndocrinologyCharité Universitätsmedizin Berlin Berlin Germany
| | - Doreen Thor
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | - Gerd Krause
- Leibniz Institute for Molecular Pharmacology Berlin Germany
| | - Torsten Schöneberg
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
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108
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Potetinova Z, Tantry S, Cohen LS, Caroccia KE, Arshava B, Becker JM, Naider F. Large multiple transmembrane domain fragments of a G protein-coupled receptor: biosynthesis, purification, and biophysical studies. Biopolymers 2012; 98:485-500. [PMID: 23203693 PMCID: PMC3542537 DOI: 10.1002/bip.22122] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 06/01/2012] [Accepted: 07/02/2012] [Indexed: 01/04/2023]
Abstract
To conduct biophysical analyses on large domains of GPCRs, multimilligram quantities of highly homogeneous proteins are necessary. This communication discusses the biosynthesis of four transmembrane and five transmembrane-containing fragments of Ste2p, a GPCR recognizing the Saccharomyces cerevisiae tridecapeptide pheromone α-factor. The target fragments contained the predicted four N-terminal Ste2p[G(31) -A(198) ] (4TMN), four C-terminal Ste2p[T(155) -L(340) ] (4TMC), or five C-terminal Ste2p[I(120) -L(340) ] (5TMC) transmembrane segments of Ste2p. 4TMN was expressed as a fusion protein using a modified pMMHa vector in L-arabinose-induced Escherichia coli BL21-AI, and cleaved with cyanogen bromide. 4TMC and 5TMC were obtained by direct expression using a pET21a vector in IPTG-induced E. coli BL21(DE3) cells. 4TMC and 5TMC were biosynthesized on a preparative scale, isolated in multimilligram amounts, characterized by MS and investigated by biophysical methods. CD spectroscopy indicated the expected highly α-helical content for 4TMC and 5TMC in membrane mimetic environments. Tryptophan fluorescence showed that 5TMC integrated into the nonpolar region of 1-stearoyl-2-hydroxy-sn-glycero-3-phospho-(1'-rac-glycerol) micelles. HSQC-TROSY investigations revealed that [(15) N]-labeled 5TMC in 50% trifluoroethanol-d(2) /H(2) O/0.05%-trifluoroacetic acid was stable enough to conduct long multidimensional NMR measurements. The entire Ste2p GPCR was not readily reconstituted from the first two and last five or first three and last four transmembrane domains.
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Affiliation(s)
- Zhanna Potetinova
- Department of Chemistry, College of Staten Island, The City University of New York, Staten Island, NY 10314, USA
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109
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Fanelli F, De Benedetti PG. Update 1 of: computational modeling approaches to structure-function analysis of G protein-coupled receptors. Chem Rev 2011; 111:PR438-535. [PMID: 22165845 DOI: 10.1021/cr100437t] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Francesca Fanelli
- Dulbecco Telethon Institute, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy.
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110
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Damian M, Marie J, Leyris JP, Fehrentz JA, Verdié P, Martinez J, Banères JL, Mary S. High constitutive activity is an intrinsic feature of ghrelin receptor protein: a study with a functional monomeric GHS-R1a receptor reconstituted in lipid discs. J Biol Chem 2011; 287:3630-41. [PMID: 22117076 DOI: 10.1074/jbc.m111.288324] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Despite its central role in signaling and the potential therapeutic applications of inverse agonists, the molecular mechanisms underlying G protein-coupled receptor (GPCR) constitutive activity remain largely to be explored. In this context, ghrelin receptor GHS-R1a is a peculiar receptor in the sense that it displays a strikingly high, physiologically relevant, constitutive activity. To identify the molecular mechanisms responsible for this high constitutive activity, we have reconstituted a purified GHS-R1a monomer in a lipid disc. Using this reconstituted system, we show that the isolated ghrelin receptor per se activates G(q) in the absence of agonist, as assessed through guanosine 5'-O-(thiotriphosphate) binding experiments. The measured constitutive activity is similar in its extent to that observed in heterologous systems and in vivo. This is the first direct evidence for the high constitutive activity of the ghrelin receptor being an intrinsic property of the protein rather than the result of influence of its cellular environment. Moreover, we show that the isolated receptor in lipid discs recruits arrestin-2 in an agonist-dependent manner, whereas it interacts with μ-AP2 in the absence of ligand or in the presence of ghrelin. Of importance, these differences are linked to ligand-specific GHS-R1a conformations, as assessed by intrinsic fluorescence measurements. The distinct ligand requirements for the interaction of purified GHS-R1a with arrestin and AP2 provide a new rationale to the differences in basal and agonist-induced internalization observed in cells.
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Affiliation(s)
- Marjorie Damian
- Institut des Biomolécules Max Mousseron, CNRS UMR 5247, Université de Montpellier 1, Faculté de Pharmacie, 15 avenue Charles Flahaut, BP 14491, 34093 Montpellier cedex 5, France
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