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Structural and Functional Implication of Natural Variants of Gαs. Int J Mol Sci 2023; 24:ijms24044064. [PMID: 36835474 PMCID: PMC9959179 DOI: 10.3390/ijms24044064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Heterotrimeric guanine nucleotide-binding proteins (G proteins) are among the most important cellular signaling components, especially G protein-coupled receptors (GPCRs). G proteins comprise three subunits, Gα, Gβ, and Gγ. Gα is the key subunit, and its structural state regulates the active status of G proteins. Interaction of guanosine diphosphate (GDP) or guanosine triphosphate (GTP) with Gα switches G protein into basal or active states, respectively. Genetic alteration in Gα could be responsible for the development of various diseases due to its critical role in cell signaling. Specifically, loss-of-function mutations of Gαs are associated with parathyroid hormone-resistant syndrome such as inactivating parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) signaling disorders (iPPSDs), whereas gain-of-function mutations of Gαs are associated with McCune-Albright syndrome and tumor development. In the present study, we analyzed the structural and functional implications of natural variants of the Gαs subtype observed in iPPSDs. Although a few tested natural variants did not alter the structure and function of Gαs, others induced drastic conformational changes in Gαs, resulting in improper folding and aggregation of the proteins. Other natural variants induced only mild conformational changes but altered the GDP/GTP exchange kinetics. Therefore, the results shed light on the relationship between natural variants of Gα and iPPSDs.
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Hanson J. [G proteins: privileged transducers of 7-transmembrane spanning receptors]. Biol Aujourdhui 2022; 215:95-106. [PMID: 35275054 DOI: 10.1051/jbio/2021011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Indexed: 06/14/2023]
Abstract
G protein-coupled receptors or GPCR are the most abundant membrane receptors in our genome with around 800 members. They play an essential role in most physiological and pathophysiological phenomena. In addition, they constitute 30% of the targets of currently marketed drugs and remain an important reservoir for new innovative therapies. Their main effectors are heterotrimeric G proteins. These are composed of 3 subunits, α, β and γ, which, upon coupling with a GPCR, dissociate into Gα and Gβγ to activate numerous signaling pathways. This article describes some of the recent advances in understanding the function and role of heterotrimeric G proteins. After a short introduction to GPCRs, the history of the discovery of G proteins is briefly described. Then, the fundamental mechanisms of activation, signaling and regulation of G proteins are reviewed. New paradigms concerning intracellular signaling, specific recognition of G proteins by GPCRs as well as biased signaling are also discussed.
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Affiliation(s)
- Julien Hanson
- Laboratoire de Pharmacologie Moléculaire, GIGA-Molecular Biology of Diseases, Université de Liège, CHU, B34, Tour GIGA (+4), Avenue de l'Hôpital 11, B-4000 Liège, Belgique
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Hilger D, Masureel M, Kobilka BK. Structure and dynamics of GPCR signaling complexes. Nat Struct Mol Biol 2018; 25:4-12. [PMID: 29323277 PMCID: PMC6535338 DOI: 10.1038/s41594-017-0011-7] [Citation(s) in RCA: 534] [Impact Index Per Article: 89.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 11/21/2017] [Indexed: 12/16/2022]
Abstract
G-protein-coupled receptors (GPCRs) relay numerous extracellular signals by triggering intracellular signaling through coupling with G proteins and arrestins. Recent breakthroughs in the structural determination of GPCRs and GPCR-transducer complexes represent important steps toward deciphering GPCR signal transduction at a molecular level. A full understanding of the molecular basis of GPCR-mediated signaling requires elucidation of the dynamics of receptors and their transducer complexes as well as their energy landscapes and conformational transition rates. Here, we summarize current insights into the structural plasticity of GPCR-G-protein and GPCR-arrestin complexes that underlies the regulation of the receptor's intracellular signaling profile.
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Affiliation(s)
- Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Matthieu Masureel
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
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Thiele S, Mantovani G, Barlier A, Boldrin V, Bordogna P, De Sanctis L, Elli FM, Freson K, Garin I, Grybek V, Hanna P, Izzi B, Hiort O, Lecumberri B, Pereda A, Saraff V, Silve C, Turan S, Usardi A, Werner R, de Nanclares GP, Linglart A. From pseudohypoparathyroidism to inactivating PTH/PTHrP signalling disorder (iPPSD), a novel classification proposed by the EuroPHP network. Eur J Endocrinol 2016; 175:P1-P17. [PMID: 27401862 DOI: 10.1530/eje-16-0107] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 07/05/2016] [Accepted: 07/07/2016] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Disorders caused by impairments in the parathyroid hormone (PTH) signalling pathway are historically classified under the term pseudohypoparathyroidism (PHP), which encompasses rare, related and highly heterogeneous diseases with demonstrated (epi)genetic causes. The actual classification is based on the presence or absence of specific clinical and biochemical signs together with an in vivo response to exogenous PTH and the results of an in vitro assay to measure Gsa protein activity. However, this classification disregards other related diseases such as acrodysostosis (ACRDYS) or progressive osseous heteroplasia (POH), as well as recent findings of clinical and genetic/epigenetic background of the different subtypes. Therefore, the EuroPHP network decided to develop a new classification that encompasses all disorders with impairments in PTH and/or PTHrP cAMP-mediated pathway. DESIGN AND METHODS Extensive review of the literature was performed. Several meetings were organised to discuss about a new, more effective and accurate way to describe disorders caused by abnormalities of the PTH/PTHrP signalling pathway. RESULTS AND CONCLUSIONS After determining the major and minor criteria to be considered for the diagnosis of these disorders, we proposed to group them under the term 'inactivating PTH/PTHrP signalling disorder' (iPPSD). This terminology: (i) defines the common mechanism responsible for all diseases; (ii) does not require a confirmed genetic defect; (iii) avoids ambiguous terms like 'pseudo' and (iv) eliminates the clinical or molecular overlap between diseases. We believe that the use of this nomenclature and classification will facilitate the development of rationale and comprehensive international guidelines for the diagnosis and treatment of iPPSDs.
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Affiliation(s)
- Susanne Thiele
- Division of Experimental Pediatric Endocrinology and DiabetesDepartment of Pediatrics, University of Lübeck, Lübeck, Germany
| | - Giovanna Mantovani
- Fondazione IRCCS Ca' Granda Ospedale Maggiore PoliclinicoEndocrinology and Diabetology Unit, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Anne Barlier
- APHMHôpital la Conception, Laboratory of Molecular Biology, Marseille, France
| | - Valentina Boldrin
- Fondazione IRCCS Ca' Granda Ospedale Maggiore PoliclinicoEndocrinology and Diabetology Unit, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Paolo Bordogna
- Fondazione IRCCS Ca' Granda Ospedale Maggiore PoliclinicoEndocrinology and Diabetology Unit, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Luisa De Sanctis
- Department of Public Health and Pediatric SciencesUniversity of Torino, Torino, Italy
| | - Francesca M Elli
- Fondazione IRCCS Ca' Granda Ospedale Maggiore PoliclinicoEndocrinology and Diabetology Unit, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Kathleen Freson
- Department of Cardiovascular SciencesCenter for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium
| | - Intza Garin
- Molecular (Epi)Genetics LaboratoryBioAraba National Health Institute, OSI Araba University Hospital, Vitoria-Gasteiz, Spain
| | - Virginie Grybek
- APHPReference Center for rare disorders of the Calcium and Phosphate Metabolism, filière OSCAR and Plateforme d'Expertise Maladies Rares Paris-Sud, Hôpital Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- INSERM U1169Hôpital Bicêtre, Le Kremlin Bicêtre, et Université Paris-Saclay, Le Kremlin Bicêtre, France
| | - Patrick Hanna
- APHPReference Center for rare disorders of the Calcium and Phosphate Metabolism, filière OSCAR and Plateforme d'Expertise Maladies Rares Paris-Sud, Hôpital Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- INSERM U1169Hôpital Bicêtre, Le Kremlin Bicêtre, et Université Paris-Saclay, Le Kremlin Bicêtre, France
| | - Benedetta Izzi
- Department of Cardiovascular SciencesCenter for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium
| | - Olaf Hiort
- Division of Experimental Pediatric Endocrinology and DiabetesDepartment of Pediatrics, University of Lübeck, Lübeck, Germany
| | - Beatriz Lecumberri
- Department of Endocrinology and NutritionLa Paz University Hospital, Madrid, Spain
| | - Arrate Pereda
- Molecular (Epi)Genetics LaboratoryBioAraba National Health Institute, OSI Araba University Hospital, Vitoria-Gasteiz, Spain
- Department of Biochemistry and Molecular BiologyUniversity of Basque Country, Leioa, Spain
| | - Vrinda Saraff
- Department of Endocrinology and DiabetesBirmingham Children's Hospital, Birmingham, UK
| | - Caroline Silve
- APHPReference Center for rare disorders of the Calcium and Phosphate Metabolism, filière OSCAR and Plateforme d'Expertise Maladies Rares Paris-Sud, Hôpital Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- INSERM U1169Hôpital Bicêtre, Le Kremlin Bicêtre, et Université Paris-Saclay, Le Kremlin Bicêtre, France
- APHPService de Biochimie et Génétique Moléculaires, Hôpital Cochin, Paris, France
| | - Serap Turan
- Department of PediatricsDivision of Endocrinology and Diabetes, Marmara University, Istanbul, Turkey
| | - Alessia Usardi
- APHPReference Center for rare disorders of the Calcium and Phosphate Metabolism, filière OSCAR and Plateforme d'Expertise Maladies Rares Paris-Sud, Hôpital Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- APHPDepartment of Paediatric Endocrinology and Diabetology, Bicêtre Paris Sud hospital, Le Kremlin Bicêtre, France
| | - Ralf Werner
- Division of Experimental Pediatric Endocrinology and DiabetesDepartment of Pediatrics, University of Lübeck, Lübeck, Germany
| | - Guiomar Perez de Nanclares
- Molecular (Epi)Genetics LaboratoryBioAraba National Health Institute, OSI Araba University Hospital, Vitoria-Gasteiz, Spain
| | - Agnès Linglart
- APHPReference Center for rare disorders of the Calcium and Phosphate Metabolism, filière OSCAR and Plateforme d'Expertise Maladies Rares Paris-Sud, Hôpital Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- INSERM U1169Hôpital Bicêtre, Le Kremlin Bicêtre, et Université Paris-Saclay, Le Kremlin Bicêtre, France
- APHPDepartment of Paediatric Endocrinology and Diabetology, Bicêtre Paris Sud hospital, Le Kremlin Bicêtre, France
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Duc NM, Kim HR, Chung KY. Structural mechanism of G protein activation by G protein-coupled receptor. Eur J Pharmacol 2015; 763:214-22. [PMID: 25981300 DOI: 10.1016/j.ejphar.2015.05.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/03/2015] [Accepted: 05/11/2015] [Indexed: 12/17/2022]
Abstract
G protein-coupled receptors (GPCRs) are a family of membrane receptors that regulate physiology and pathology of various organs. Consequently, about 40% of drugs in the market targets GPCRs. Heterotrimeric G proteins are composed of α, β, and γ subunits, and act as the key downstream signaling molecules of GPCRs. The structural mechanism of G protein activation by GPCRs has been of a great interest, and a number of biochemical and biophysical studies have been performed since the late 80's. These studies investigated the interface between GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. Recently, arrestins are also reported to be important molecular switches in GPCR-mediated signal transduction, and the physiological output of arrestin-mediated signal transduction is different from that of G protein-mediated signal transduction. Understanding the structural mechanism of the activation of G proteins and arrestins would provide fundamental information for the downstream signaling-selective GPCR-targeting drug development. This review will discuss the structural mechanism of GPCR-induced G protein activation by comparing previous biochemical and biophysical studies.
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Affiliation(s)
- Nguyen Minh Duc
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea.
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Chung KY. Structural Aspects of GPCR-G Protein Coupling. Toxicol Res 2014; 29:149-55. [PMID: 24386514 PMCID: PMC3877993 DOI: 10.5487/tr.2013.29.3.149] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/10/2013] [Accepted: 09/17/2013] [Indexed: 11/24/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane receptors; approximately 40% of drugs on the market target GPCRs. A precise understanding of the activation mechanism of GPCRs would facilitate the development of more effective and less toxic drugs. Heterotrimeric G proteins are important molecular switches in GPCR-mediated signal transduction. An agonist-activated receptor interacts with specific sites on G proteins and promotes the release of GDP from the Gα subunit. Because of the important biological role of the GPCR-G protein coupling, conformational changes in the G protein upon receptor coupling have been of great interest. One of the most important questions was the interface between the GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. A number of biochemical and biophysical studies have been performed since the late 80s to address these questions; there was a significant breakthrough in 2011 when the crystal structure of a GPCR-G protein complex was solved. This review discusses the structural aspects of GPCR-G protein coupling by comparing the results of previous biochemical and biophysical studies to the GPCR-G protein crystal structure.
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Affiliation(s)
- Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon, Korea
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Hamm HE, Kaya AI, Gilbert JA, Preininger AM. Linking receptor activation to changes in Sw I and II of Gα proteins. J Struct Biol 2013; 184:63-74. [PMID: 23466875 DOI: 10.1016/j.jsb.2013.02.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 12/28/2012] [Accepted: 02/22/2013] [Indexed: 10/27/2022]
Abstract
G-protein coupled receptors catalyze nucleotide exchange on G proteins, which results in subunit dissociation and effector activation. In the recent β2AR-Gs structure, portions of Switch I and II of Gα are not fully elucidated. We paired fluorescence studies of receptor-Gαi interactions with the β2AR-Gs and other Gi structures to investigate changes in Switch I and II during receptor activation and GTP binding. The β2/β3 loop containing Leu194 of Gαi is located between Switches I and II, in close proximity to IC2 of the receptor and the C-terminus of Gα, thus providing an allosteric connection between these Switches and receptor activation. We compared the environment of residues in myristoylated Gαi proteins in the heterotrimer to that upon receptor activation and subsequent GTP binding. Upon receptor activation, residues in both Switch regions are less solvent-exposed, as compared to the heterotrimer. Upon GTPγS binding, the environment of several residues in Switch I resemble the receptor-bound state, while Switch II residues display effects on their environment which are consistent with their role in GTP binding and Gβγ dissociation. The ability to merge available crystal structures with solution studies is a powerful tool to gain insight into conformational changes associated with receptor-mediated Gi protein activation.
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Affiliation(s)
- Heidi E Hamm
- Vanderbilt University Medical Center, Department of Pharmacology, Nashville, TN 37232-6600, United States
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8
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Cheeseman MT, Vowell K, Hough TA, Jones L, Pathak P, Tyrer HE, Kelly M, Cox R, Warren MV, Peters J. A mouse model for osseous heteroplasia. PLoS One 2012; 7:e51835. [PMID: 23284784 PMCID: PMC3526487 DOI: 10.1371/journal.pone.0051835] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 11/07/2012] [Indexed: 11/29/2022] Open
Abstract
GNAS/Gnas encodes Gsα that is mainly biallelically expressed but shows imprinted expression in some tissues. In Albright Hereditary Osteodystrophy (AHO) heterozygous loss of function mutations of GNAS can result in ectopic ossification that tends to be superficial and attributable to haploinsufficiency of biallelically expressed Gsα. Oed-Sml is a point missense mutation in exon 6 of the orthologous mouse locus Gnas. We report here both the late onset ossification and occurrence of benign cutaneous fibroepithelial polyps in Oed-Sml. These phenotypes are seen on both maternal and paternal inheritance of the mutant allele and are therefore due to an effect on biallelically expressed Gsα. The ossification is confined to subcutaneous tissues and so resembles the ossification observed with AHO. Our mouse model is the first with both subcutaneous ossification and fibroepithelial polyps related to Gsα deficiency. It is also the first mouse model described with a clinically relevant phenotype associated with a point mutation in Gsα and may be useful in investigations of the mechanisms of heterotopic bone formation. Together with earlier results, our findings indicate that Gsα signalling pathways play a vital role in repressing ectopic bone formation.
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Affiliation(s)
- Michael T Cheeseman
- Medical Research Council Mammalian Genetics Unit, Medical Research Council Harwell, Oxfordshire, UK.
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Snyder EE, Walts B, Pérusse L, Chagnon YC, Weisnagel SJ, Rankinen T, Bouchard C. The Human Obesity Gene Map: The 2003 Update. ACTA ACUST UNITED AC 2012; 12:369-439. [PMID: 15044658 DOI: 10.1038/oby.2004.47] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Eric E Snyder
- Human Genomics Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana 70808-4124, USA
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Pérusse L, Rankinen T, Zuberi A, Chagnon YC, Weisnagel SJ, Argyropoulos G, Walts B, Snyder EE, Bouchard C. The Human Obesity Gene Map: The 2004 Update. ACTA ACUST UNITED AC 2012; 13:381-490. [PMID: 15833932 DOI: 10.1038/oby.2005.50] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Louis Pérusse
- Division of Kinesiology, Department of Social and Preventive Medicine, Faculty of Medicine, Laval University, Sainte-Foy, Québec, Canada
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DeMars G, Fanelli F, Puett D. The extreme C-terminal region of Gαs differentially couples to the luteinizing hormone and beta2-adrenergic receptors. Mol Endocrinol 2011; 25:1416-30. [PMID: 21622536 DOI: 10.1210/me.2011-0009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The mechanisms of G protein coupling to G protein-coupled receptors (GPCR) share general characteristics but may exhibit specific interactions unique for each GPCR/G protein partnership. The extreme C terminus (CT) of G protein α-subunits has been shown to be important for association with GPCR. Hypothesizing that the extreme CT of Gα(s) is an essential component of the molecular landscape of the GPCR, human LH receptor (LHR), and β(2)-adrenergic receptor (β(2)-AR), a model cell system was created for the expression and manipulation of Gα(s) subunits in LHR(+) s49 ck cells that lack endogenous Gα(s). On the basis of studies involving truncations, mutations, and chain extensions of Gα(s), the CT was found to be necessary for LHR and β(2)-AR signaling. Some general similarities were found for the responses of the two receptors, but significant differences were also noted. Computational modeling was performed with a combination of comparative modeling, molecular dynamics simulations, and rigid body docking. The resulting models, focused on the Gα(s) CT, are supported by the experimental observations and are characterized by the interaction of the four extreme CT amino acid residues of Gα(s) with residues in LHR and β(2)-AR helix 3, (including R of the DRY motif), helix 6, and intracellular loop 2. This portion of Gα(s) recognizes the same regions of the two GPCR, although with differences in the details of selected interactions. The predicted longer cytosolic extensions of helices 5 and 6 of β(2)-AR are expected to contribute significantly to differences in Gα(s) recognition by the two receptors.
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Affiliation(s)
- Geneva DeMars
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-7229, USA
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Thiele S, de Sanctis L, Werner R, Grötzinger J, Aydin C, Jüppner H, Bastepe M, Hiort O. Functional characterization of GNAS mutations found in patients with pseudohypoparathyroidism type Ic defines a new subgroup of pseudohypoparathyroidism affecting selectively Gsα-receptor interaction. Hum Mutat 2011; 32:653-60. [PMID: 21488135 DOI: 10.1002/humu.21489] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 02/09/2011] [Indexed: 01/09/2023]
Abstract
Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the α-subunit of stimulatory G proteins (Gsα) that mediate signal transduction of G protein-coupled receptors via cAMP. PHP type Ic (PHPIc) and PHPIa share clinical features of Albright hereditary osteodystrophy (AHO); however, in vitro activity of solubilized Gsα protein is normal in PHPIc but reduced in PHPIa. We screened 32 patients classified as PHPIc for GNAS mutations and identified three mutations (p.E392K, p.E392X, p.L388R) in four unrelated families. These and one novel mutation associated with PHPIa (p.L388P) were introduced into a pcDNA3.1(-) expression vector encoding Gsα wild-type and expressed in a Gsα-null cell line (Gnas(E2-/E2-) ). To investigate receptor-mediated cAMP accumulation, we stimulated the endogenous expressed β(2) -adrenergic receptor, or the coexpressed PTH or TSH receptors, and measured the synthesized cAMP by RIA. The results were compared to receptor-independent cholera toxin-induced cAMP accumulation. Each of the mutants associated with PHPIc significantly reduced or completely disrupted receptor-mediated activation, but displayed normal receptor-independent activation. In contrast, PHPIa associated p.L388P disrupted both receptor-mediated activation and receptor-independent activation. We present a new subgroup of PHP that is caused by Gsα deficiency and selectively affects receptor coupling functions of Gsα.
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Affiliation(s)
- Susanne Thiele
- Department of Pediatrics and Adolescent Medicine, University of Lübeck, Germany.
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13
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Fernandez-Rebollo E, Barrio R, Pérez-Nanclares G, Carcavilla A, Garin I, Castaño L, de Nanclares GP. New mutation type in pseudohypoparathyroidism type Ia. Clin Endocrinol (Oxf) 2008; 69:705-12. [PMID: 18394017 DOI: 10.1111/j.1365-2265.2008.03255.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
CONTEXT The GNAS gene encodes the alpha-subunit of the stimulatory G proteins, which play a crucial role in intracellular signal transduction of peptide and neurotransmitter receptors. Heterozygous inactivating maternally inherited mutations of GNAS (including translation initiation mutations, amino acid substitutions, nonsense mutations, splice site mutations and small insertions or deletions) lead to a phenotype in which Albright hereditary osteodystrophy is associated with pseudohypoparathyroidism type Ia. OBJECTIVE We sought to identify the molecular defect in a patient who was thought to have PHP-Ia. METHODS AND RESULTS The GNAS gene of a 5-year-old boy with brachydactily, mental retardation, pseudohypoparathyroidism and congenital hypothyroidism was investigated. We found a heterozygous inversion of exon 2 and part of intron 1 of de novo origin. Molecular studies of cDNA from blood RNA demonstrated that both the normal and the mutant variants were stable and that new splice-sites were generated. CONCLUSION This report demonstrates the first evidence for an inversion at the GNAS gene responsible of pseudohypoparathyroidism type Ia.
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Adegbite NS, Xu M, Kaplan FS, Shore EM, Pignolo RJ. Diagnostic and mutational spectrum of progressive osseous heteroplasia (POH) and other forms of GNAS-based heterotopic ossification. Am J Med Genet A 2008; 146A:1788-96. [PMID: 18553568 DOI: 10.1002/ajmg.a.32346] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Progressive osseous heteroplasia (POH) is a rare, disabling disease of heterotopic ossification (HO) that progresses from skin and subcutaneous tissues into deep skeletal muscle. POH occurs in the absence of multiple developmental features of Albright hereditary osteodystrophy (AHO) or hormone resistance, clinical manifestations that are also associated with GNAS inactivation. However, occasional patients with AHO and pseudohypoparathyroidism 1a/c (PHP1a/c; AHO features plus hormone resistance) have also been described who have progressive HO. This study was undertaken to define the diagnostic and mutational spectrum of POH and progressive disorders of HO, and to distinguish them from related disorders in which HO remains confined to the skin and subcutaneous tissues. We reviewed the charts of 111 individuals who had cutaneous and subcutaneous ossification. All patients were assessed for eight characteristics: age of onset of HO, presence and location of HO, depth of HO, type of HO, progression of HO, features of AHO, PTH resistance, and GNAS mutation analysis. We found, based on clinical criteria, that POH and progressive HO syndromes are at the severe end of a phenotypic spectrum of GNAS-inactivating conditions associated with extra-skeletal ossification. While most individuals with superficial or progressive ossification had mutations in GNAS, there were no specific genotype-phenotype correlations that distinguished the more progressive forms of HO (e.g., POH) from the non-progressive forms (osteoma cutis, AHO, and PHP1a/c).
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Affiliation(s)
- N S Adegbite
- Department of Orthopaedic Surgery, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104, USA
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15
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Abstract
Heterotrimeric G proteins couple the activation of heptahelical receptors at the cell surface to the intracellular signaling cascades that mediate the physiological responses to extracellular stimuli. G proteins are molecular switches that are activated by receptor-catalyzed GTP for GDP exchange on the G protein alpha subunit, which is the rate-limiting step in the activation of all downstream signaling. Despite the important biological role of the receptor-G protein interaction, relatively little is known about the structure of the complex and how it leads to nucleotide exchange. This chapter will describe what is known about receptor and G protein structure and outline a strategy for assembling the current data into improved models for the receptor-G protein complex that will hopefully answer the question as to how receptors flip the G protein switch.
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Affiliation(s)
- William M Oldham
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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16
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Tamada Y, Kanda S, Suzuki H, Tajima T, Nishiyama T. A pseudohypoparathyroidism type Ia patient with normocalcemia. Endocr J 2008; 55:169-73. [PMID: 18250541 DOI: 10.1507/endocrj.k07e-019] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Pseudohypoparathyroidism type Ia (PHP-Ia), one of 4 types of PHP, is a genetic disease characterized by clinical hypoparathyroidism caused by parathyroid hormone (PTH) resistance. In addition, patients with PHP-Ia show resistance to other hormones as well as Albright's hereditary osteodystrophy (AHO), a constellation of features including short stature, obesity, brachydactyly, ectopic ossifications, and/or mental retardation. Hypocalcemia is one of the hallmarks of PHP-Ia, but several PHP-Ia patients have been described to have normocalcemia. We encountered a 10-year-old girl with typical Albright's hereditary osteodystrophy with round face, short stature, brachydactyly, and obesity. Biochemical examination showed normocalcemia and increased PTH levels. Ellsworth-Howard test did not show any responses of urinary cAMP and phosphate. Based on these findings, she was diagnosed as having PHP-Ia with normocalcemia. Sequencing analysis of the GNAS gene identified a heterozygous missense mutation in exon 13 (R385H), which was previously reported in a PHP-Ia patient. The exact reason for her normocalcemia is not determined, but we must recognize heterogeneous biochemical findings even in PHP-Ia.
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Affiliation(s)
- Yasuko Tamada
- Department of Public Health, Kansai Medical University, Moriguchi, Japan
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17
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Mouallem M, Shaharabany M, Weintrob N, Shalitin S, Nagelberg N, Shapira H, Zadik Z, Farfel Z. Cognitive impairment is prevalent in pseudohypoparathyroidism type Ia, but not in pseudopseudohypoparathyroidism: possible cerebral imprinting of Gsalpha. Clin Endocrinol (Oxf) 2008; 68:233-9. [PMID: 17803690 DOI: 10.1111/j.1365-2265.2007.03025.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Pseudohypoparathyroidism type Ia (PHP-Ia) is a hereditary disorder characterized by resistance to multiple hormones that work via cAMP such as PTH and TSH, accompanied by typical skeletal features including short stature and brachydactyly, termed Albright hereditary osteodystrophy (AHO). In affected kindreds, some members may have AHO but not hormone resistance; they are termed as pseudopseudohypoparathyroidism (PPHP). The molecular basis for the disorder is heterozygous inactivating mutation of the Gsalpha gene. In affected families, subjects with both PHP-Ia and PPHP have the same Gsalpha mutations. The skeletal features common to PPHP and PHP-Ia are presumably caused by tissue-specific Gsalpha haploinsufficiency. Other features that distinguish between PPHP and PHP-Ia, such as the multihormone resistance, are presumably caused by tissue-specific paternal imprinting of Gsalpha. This suggests that major differences in phenotype between PHP-Ia and PPHP point to specific tissues with Gsalpha imprinting. One such major difference may be cognitive function in PHP-Ia and PPHP. DESIGN Description of a large family with PHP-Ia and PPHP. PATIENTS Eleven affected subjects with PHP-Ia or PPHP in one family. MEASUREMENTS Cognitive impairment (CI) was defined by a history of developmental delay, learning disability and the Wechsler intelligence scale. RESULTS CI occurred only in the five PHP-Ia but not in the six PPHP subjects. Hypothyroidism which occurred in all PHP-Ia subjects was apparently not the cause of CI as it was mild, and was treated promptly. Analysis of additional Israeli cases, and the published cases from the literature, all with documented Gsalpha mutations, revealed that CI is prevalent in PHP-Ia [60 of 77 subjects (79%)] but not in PPHP [3 of 30 subjects (10%)] (P < 1 x 10(-6)). CONCLUSION We suggest that Gsalpha is imprinted in the brain.
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Affiliation(s)
- M Mouallem
- Department of Medicine E, Sheba Medical Center, Tel Hashomer, and Tel Aviv University School of Medicine, Tel Aviv, Israel
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18
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Heterotrimeric G protein activation by G-protein-coupled receptors. Nat Rev Mol Cell Biol 2008; 9:60-71. [PMID: 18043707 DOI: 10.1038/nrm2299] [Citation(s) in RCA: 783] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Heterotrimeric G proteins have a crucial role as molecular switches in signal transduction pathways mediated by G-protein-coupled receptors. Extracellular stimuli activate these receptors, which then catalyse GTP-GDP exchange on the G protein alpha-subunit. The complex series of interactions and conformational changes that connect agonist binding to G protein activation raise various interesting questions about the structure, biomechanics, kinetics and specificity of signal transduction across the plasma membrane.
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19
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Makita N, Sato J, Rondard P, Fukamachi H, Yuasa Y, Aldred MA, Hashimoto M, Fujita T, Iiri T. Human G(salpha) mutant causes pseudohypoparathyroidism type Ia/neonatal diarrhea, a potential cell-specific role of the palmitoylation cycle. Proc Natl Acad Sci U S A 2007; 104:17424-9. [PMID: 17962410 PMCID: PMC2077272 DOI: 10.1073/pnas.0708561104] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Indexed: 01/08/2023] Open
Abstract
Pseudohypoparathyroidism type Ia (PHP-Ia) results from the loss of one allele of G(salpha), causing resistance to parathyroid hormone and other hormones that transduce signals via G(s). Most G(salpha)mutations cause the complete loss of protein expression, but some cause loss of function only, and these have provided valuable insights into the normal function of G proteins. Here we have analyzed a mutant G(salpha) (alphas-AVDT) harboring AVDT amino acid repeats within its GDP/GTP binding site, which was identified in unique patients with PHP-Ia accompanied by neonatal diarrhea. Biochemical and intact cell analyses showed that alphas-AVDT is unstable but constitutively active as a result of rapid GDP release and reduced GTP hydrolysis. This instability underlies the PHP-Ia phenotype. alphas-AVDT is predominantly localized in the cytosol, but in rat and mouse small intestine epithelial cells (IEC-6 and DIF-12 cells) alphas-AVDT was found to be localized predominantly in the membrane where adenylyl cyclase is present and constitutive increases in cAMP accumulation occur in parallel. The likely cause of this membrane localization is the inhibition of an activation-dependent decrease in alphas palmitoylation. Upon the overexpression of acyl-protein thioesterase 1, however, alphas-AVDT translocates from the membrane to the cytosol, and the constitutive accumulation of cAMP becomes attenuated. These results suggest that PHP-Ia results from the instability of alphas-AVDT and that the accompanying neonatal diarrhea may result from its enhanced constitutive activity in the intestine. Hence, palmitoylation may control the activity and localization of G(salpha) in a cell-specific manner.
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Affiliation(s)
- Noriko Makita
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Junichiro Sato
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, 141 Rue de la Cardonille, 34094 Montpellier Cedex 5, France
| | - Hiroshi Fukamachi
- Department of Molecular Oncology, Graduate School of Medicine and Dentistry, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan; and
| | - Yasuhito Yuasa
- Department of Molecular Oncology, Graduate School of Medicine and Dentistry, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan; and
| | - Micheala A. Aldred
- Division of Medical Genetics, University of Leicester and Leicestershire Genetics Service, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
| | - Makiko Hashimoto
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Toshiro Fujita
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Taroh Iiri
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
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21
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Plati J, Tsomaia N, Piserchio A, Mierke DF. Structural features of parathyroid hormone receptor coupled to Galpha(s)-protein. Biophys J 2006; 92:535-40. [PMID: 17040990 PMCID: PMC1751412 DOI: 10.1529/biophysj.106.094813] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The molecular basis of the activation of G-proteins by the G-protein coupled receptor for parathyroid hormone (PTH) is unknown. Employing a combination of NMR methods and computer-based structural refinement, structural features involved in the activation of Galpha(s) by the PTH receptor (PTH1R) have been determined. Focusing on the C-terminus of the third intracellular loop (IC3), previously shown to be important for Galpha(s) activation by PTH1R, the structure of this region, PTH1R(402-408), while bound to Galpha(s), was determined by transferred nuclear Overhauser effect spectroscopy. The relative topological orientation of the IC3 while associated with Galpha(s) was determined by saturation transfer difference spectroscopy. These experimental data were incorporated into molecular dynamics simulations of the PTH1R and Galpha(s) to provide atomic insight into the receptor-protein interactions important for PTH signaling and a structural framework to analyze previous mutagenesis studies of Galpha(s). These data provide the first step toward development of a molecular mechanism for the signaling profile of PTH1R, an important regulator of calcium levels in the bloodstream.
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Affiliation(s)
- Jessica Plati
- Department of Chemistry, and Department of Molecular Pharmacology, Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912, USA
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22
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Rankinen T, Zuberi A, Chagnon YC, Weisnagel SJ, Argyropoulos G, Walts B, Pérusse L, Bouchard C. The human obesity gene map: the 2005 update. Obesity (Silver Spring) 2006; 14:529-644. [PMID: 16741264 DOI: 10.1038/oby.2006.71] [Citation(s) in RCA: 685] [Impact Index Per Article: 38.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Tuomo Rankinen
- Human Genomics Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808-4124, USA
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23
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Hazari A, Lowes V, Chan JHP, Wong CSS, Ho MKC, Wong YH. Replacement of the α5 helix of Gα16 with Gαs-specific sequences enhances promiscuity of Gα16 toward Gs-coupled receptors. Cell Signal 2004; 16:51-62. [PMID: 14607275 DOI: 10.1016/s0898-6568(03)00097-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
G(16) can couple indiscriminately to a large number of G protein-coupled receptors (GPCRs), making it a prime candidate as a universal adaptor for GPCRs. In order to increase the promiscuity of Galpha(16), three chimeras incorporating increasing lengths of G(s)-specific residues (25, 44 or 81 residues) into the C-terminus of Galpha(16) were constructed and named 16s25, 16s44 and 16s81, respectively. The chimeras were examined for their ability to mediate receptor-induced stimulation of phospholipase C (PLC) and Ca(2+) mobilization. 16s25 was more effective than 16s44 and 16s81 at coupling to G(s)-linked receptors. 16s25 coupled productively to 10 different G(s)-coupled receptors examined and, for 50% of these receptors, 16s25-mediated PLC activities were higher than those mediated via Galpha(16). Similar results were observed for agonist-induced Ca(2+) mobilizations. These results show that incorporating the alpha5 helix of Galpha(s) into Galpha(16) can increase the promiscuity of 16s25 towards G(s)-coupled receptors.
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MESH Headings
- Animals
- Base Sequence/genetics
- COS Cells
- Calcium/metabolism
- Calcium Signaling/physiology
- GTP-Binding Protein alpha Subunits/genetics
- GTP-Binding Protein alpha Subunits/metabolism
- GTP-Binding Protein alpha Subunits, Gq-G11
- GTP-Binding Protein alpha Subunits, Gs/genetics
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Heterotrimeric GTP-Binding Proteins/genetics
- Heterotrimeric GTP-Binding Proteins/metabolism
- Protein Structure, Secondary/genetics
- Protein Structure, Tertiary/genetics
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Signal Transduction/genetics
- Type C Phospholipases/metabolism
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Affiliation(s)
- Anjali Hazari
- Department of Biochemistry, the Biotechnology Research Institute, and the Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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24
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Chagnon YC, Rankinen T, Snyder EE, Weisnagel SJ, Pérusse L, Bouchard C. The human obesity gene map: the 2002 update. OBESITY RESEARCH 2003; 11:313-67. [PMID: 12634430 DOI: 10.1038/oby.2003.47] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.
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Affiliation(s)
- Yvon C Chagnon
- Psychiatric Genetic Unit, Laval University Robert-Giffard Research Center, Beauport, Québec, Canada.
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25
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Abstract
Gs is the ubiquitously expressed heterotrimeric G protein that couples receptors to the effector enzyme adenylyl cyclase and is required for receptor-stimulated intracellular cAMP generation. Activated receptors promote the exchange of GTP for GDP on the Gs alpha-subunit (Gs(alpha)), resulting in Gs activation; an intrinsic GTPase activity of Gs(alpha) deactivates Gs by hydrolyzing bound GTP to GDP. Mutations of Gs(alpha) residues involved in the GTPase reaction that lead to constitutive activation are present in endocrine tumors, fibrous dysplasia of bone, and McCune-Albright syndrome. Heterozygous loss-of-function mutations lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, and skeletal defects, and are sometimes associated with progressive osseous heteroplasia. Maternal transmission of Gs(alpha) mutations leads to AHO plus resistance to several hormones (e.g., parathyroid hormone) that activate Gs in their target tissues (pseudohypoparathyroidism type IA), while paternal transmission leads only to the AHO phenotype (pseudopseudohypoparathyroidism). Studies in both mice and humans demonstrate that Gs(alpha) is imprinted in a tissue-specific manner, being expressed primarily from the maternal allele in some tissues and biallelically expressed in most other tissues. This likely explains why multihormone resistance occurs only when Gs(alpha) mutations are inherited maternally. The Gs(alpha) gene GNAS1 has at least four alternative promoters and first exons, leading to the production of alternative gene products including Gs(alpha), XL alphas (a novel Gs(alpha) isoform expressed only from the paternal allele), and NESP55 (a chromogranin-like protein expressed only from the maternal allele). The fourth alternative promoter and first exon (exon 1A) located just upstream of the Gs(alpha) promoter is normally methylated on the maternal allele and is transcriptionally active on the paternal allele. In patients with parathyroid hormone resistance but without AHO (pseudohypoparathyroidism type IB), the exon 1A promoter region is unmethylated and transcriptionally active on both alleles. This GNAS1 imprinting defect is predicted to decrease Gs(alpha) expression in tissues where Gs(alpha) is normally imprinted and therefore to lead to renal parathyroid hormone resistance.
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Affiliation(s)
- Lee S Weinstein
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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26
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Rankinen T, Pérusse L, Weisnagel SJ, Snyder EE, Chagnon YC, Bouchard C. The human obesity gene map: the 2001 update. OBESITY RESEARCH 2002; 10:196-243. [PMID: 11886943 DOI: 10.1038/oby.2002.30] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This report constitutes the eighth update of the human obesity gene map, incorporating published results up to the end of October 2001. Evidence from the rodent and human obesity cases caused by single-gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) uncovered in human genome-wide scans and in crossbreeding experiments in various animal models, association and linkage studies with candidate genes and other markers is reviewed. The human cases of obesity related in some way to single-gene mutations in six different genes are incorporated. Twenty-five Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different QTLs reported from animal models currently reaches 165. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 174 studies reporting positive associations with 58 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map depicted in Figure 1 reveals that putative loci affecting obesity-related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months, and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.
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Affiliation(s)
- Tuomo Rankinen
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana 70808-4124, USA.
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27
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Weinstein LS, Yu S, Warner DR, Liu J. Endocrine manifestations of stimulatory G protein alpha-subunit mutations and the role of genomic imprinting. Endocr Rev 2001; 22:675-705. [PMID: 11588148 DOI: 10.1210/edrv.22.5.0439] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The heterotrimeric G protein G(s) couples hormone receptors (as well as other receptors) to the effector enzyme adenylyl cyclase and is therefore required for hormone-stimulated intracellular cAMP generation. Receptors activate G(s) by promoting exchange of GTP for GDP on the G(s) alpha-subunit (G(s)alpha) while an intrinsic GTPase activity of G(s)alpha that hydrolyzes bound GTP to GDP leads to deactivation. Mutations of specific G(s)alpha residues (Arg(201) or Gln(227)) that are critical for the GTPase reaction lead to constitutive activation of G(s)-coupled signaling pathways, and such somatic mutations are found in endocrine tumors, fibrous dysplasia of bone, and the McCune-Albright syndrome. Conversely, heterozygous loss-of-function mutations may lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, brachydactyly, sc ossifications, and mental deficits. Similar mutations are also associated with progressive osseous heteroplasia. Interestingly, paternal transmission of GNAS1 mutations leads to the AHO phenotype alone (pseudopseudohypoparathyroidism), while maternal transmission leads to AHO plus resistance to several hormones (e.g., PTH, TSH) that activate G(s) in their target tissues (pseudohypoparathyroidism type IA). Studies in G(s)alpha knockout mice demonstrate that G(s)alpha is imprinted in a tissue-specific manner, being expressed primarily from the maternal allele in some tissues (e.g., renal proximal tubule, the major site of renal PTH action), while being biallelically expressed in most other tissues. Disrupting mutations in the maternal allele lead to loss of G(s)alpha expression in proximal tubules and therefore loss of PTH action in the kidney, while mutations in the paternal allele have little effect on G(s)alpha expression or PTH action. G(s)alpha has recently been shown to be also imprinted in human pituitary glands. The G(s)alpha gene GNAS1 (as well as its murine ortholog Gnas) has at least four alternative promoters and first exons, leading to the production of alternative gene products including G(s)alpha, XLalphas (a novel G(s)alpha isoform that is expressed only from the paternal allele), and NESP55 (a chromogranin-like protein that is expressed only from the maternal allele). A fourth alternative promoter and first exon (exon 1A) located approximately 2.5 kb upstream of the G(s)alpha promoter is normally methylated on the maternal allele and transcriptionally active on the paternal allele. In patients with isolated renal resistance to PTH (pseudohypoparathyroidism type IB), the exon 1A promoter region has a paternal-specific imprinting pattern on both alleles (unmethylated, transcriptionally active), suggesting that this region is critical for the tissue-specific imprinting of G(s)alpha. The GNAS1 imprinting defect in pseudohypoparathyroidism type IB is predicted to decrease G(s)alpha expression in renal proximal tubules. Studies in G(s)alpha knockout mice also demonstrate that this gene is critical in the regulation of lipid and glucose metabolism.
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Affiliation(s)
- L S Weinstein
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Pérusse L, Chagnon YC, Weisnagel SJ, Rankinen T, Snyder E, Sands J, Bouchard C. The human obesity gene map: the 2000 update. OBESITY RESEARCH 2001; 9:135-69. [PMID: 11316348 DOI: 10.1038/oby.2001.17] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This report constitutes the seventh update of the human obesity gene map incorporating published results up to the end of October 2000. Evidence from the rodent and human obesity cases caused by single-gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci uncovered in human genome-wide scans and in cross-breeding experiments in various animal models, and association and linkage studies with candidate genes and other markers are reviewed. Forty-seven human cases of obesity caused by single-gene mutations in six different genes have been reported in the literature to date. Twenty-four Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different quantitative trait loci reported from animal models currently reaches 115. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 130 studies reporting positive associations with 48 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map reveals that putative loci affecting obesity-related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.
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Affiliation(s)
- L Pérusse
- Department of Social and Preventive Medicine, Faculty of Medicine, Laval University, Sainte-Foy, Québec, Canada.
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Wu WI, Schwindinger WF, Aparicio LF, Levine MA. Selective resistance to parathyroid hormone caused by a novel uncoupling mutation in the carboxyl terminus of G alpha(s). A cause of pseudohypoparathyroidism type Ib. J Biol Chem 2001; 276:165-71. [PMID: 11029463 DOI: 10.1074/jbc.m006032200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G(s) is a heterotrimeric (alpha, beta, and gamma chains) G protein that couples heptahelical plasma membrane receptors to stimulation of adenylyl cyclase. Inactivation of one GNAS1 gene allele encoding the alpha chain of G(s) (G alpha(s)) causes pseudohypoparathyroidism type Ia. Affected subjects have resistance to parathyroid hormone (PTH) and other hormones that activate adenylyl cyclase plus somatic features termed Albright hereditary osteodystrophy. By contrast, subjects with pseudohypoparathyroidism type Ib have hormone resistance that is limited to PTH and lack Albright hereditary osteodystrophy. The molecular basis for pseudohypoparathyroidism type Ib is unknown. We analyzed the GNAS1 gene for mutations using polymerase chain reaction to amplify genomic DNA from three brothers with pseudohypoparathyroidism type Ib. We identified a novel heterozygous 3-base pair deletion causing loss of isoleucine 382 in the three affected boys and their clinically unaffected mother and maternal grandfather. This mutation was absent in other family members and 15 additional unrelated subjects with pseudohypoparathyroidism type Ib. To characterize the signaling properties of the mutant G alpha(s), we used site-directed mutagenesis to introduce the isoleucine 382 deletion into a wild type G alpha(s) cDNA, transfected HEK293 cells with either wild type or mutant G alpha(s) cDNA, plus cDNAs encoding heptahelical receptors for PTH, thyrotropic hormone, or luteinizing hormone, and we measured cAMP production in response to hormone stimulation. The mutant G alpha(s) protein was unable to interact with the receptor for PTH but showed normal coupling to the other coexpressed heptahelical receptors. These results provide evidence of selective uncoupling of the mutant G alpha(s) from PTH receptors and explain PTH-specific hormone resistance in these three brothers with pseudohypoparathyroidism type Ib. The absence of PTH resistance in the mother and maternal grandfather who carry the same mutation is consistent with current models of paternal imprinting of the GNAS1 gene.
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Affiliation(s)
- W I Wu
- Division of Pediatric Endocrinology, Department of Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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30
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Mantovani G, Romoli R, Weber G, Brunelli V, De Menis E, Beccio S, Beck-Peccoz P, Spada A. Mutational analysis of GNAS1 in patients with pseudohypoparathyroidism: identification of two novel mutations. J Clin Endocrinol Metab 2000; 85:4243-8. [PMID: 11095461 DOI: 10.1210/jcem.85.11.6986] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pseudohypoparathyroidism (PHP) refers to two major variants that generally coexist in the same family, PHP type Ia (PHP Ia), in which both PTH resistance and a constellation of physical features, termed Albright's hereditary osteodystrophy (AHO), are present, and pseudopseudohypoparathyroidism (PPHP), in which AHO occurs without PTH resistance. Most patients with PHP Ia show a partial deficiency (50%) of Gs activity, due to loss of function mutations in Gsalpha gene (GNAS1). The present study reports clinical, biochemical, and molecular data of 8 unrelated families with PHP Ia and PPHP. The 13 exons of GNAS1 were screened for mutations by PCR and direct sequencing of the amplified products. We detected heterozygous mutations in the affected members of the 4 families in which PHP Ia was present. In 2 families 2 previously reported deletions in exons 5 and 7 were found, whereas in the other 2 families, 2 novel frameshift deletions were identified in exons 1 and 11, causing a premature stop codon in the mutant allele. No mutation was detected in the families in which PPHP was the only clinical manifestation. In conclusion, we report the first mutational analysis of Italian patients with PHP Ia and PPHP, and we describe two novel deletions in GNAS1. Furthermore, we confirm that these mutations cannot be detected in families with isolated PPHP, suggesting that these forms of AHO are genetically distinct from PHP Ia.
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Affiliation(s)
- G Mantovani
- Ospedale Maggiore IRCCS, Institute of Endocrine Sciences, University of Milan, Italy
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31
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Abstract
GNAS1 on chromosome 20 is a complex locus, encoding multiple proteins, of which G(s)alpha, the alpha-subunit of the heterotrimeric stimulatory G protein G(s), is of particular interest clinically. Amino acid substitutions at two specific codons lead to constitutive activation of G(s)alpha. Such gain-of-function mutations are found in a variety of sporadic endocrine tumors and in McCune-Albright syndrome, a sporadic condition characterized by multiple endocrine abnormalities. Heterozygous loss of G(s)alpha function results in the dominantly inherited condition, Albright hereditary osteodystrophy (AHO). Here we present a review of published GNAS1 mutations and report 19 additional mutations, of which 15 are novel. A diverse range of inactivating mutations has been detected, scattered throughout the gene but showing some evidence of clustering. Only one, a recurring 4 bp deletion in exon 7, could be considered common among AHO patients. The parental origin of the mutation apparently determines whether or not the patient shows end-organ resistance to hormones such as parathyroid hormone. G(s)alpha is biallelically expressed in all tissues studied to date and thus there is no direct evidence that this transcript is imprinted. However, the recent identification of other imprinted transcripts encoded by GNAS1 and overlapping G(s)alpha, together with at least one imprinted antisense transcript, raises intriguing questions about how the primary effect of mutations in GNAS1 might be modulated.
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Affiliation(s)
- M A Aldred
- Leicestershire Genetics Centre, Leicester Royal Infirmary, Leicester, UK
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32
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Carel JC, Garabédian M, Mallet E, Chaussain JL. [Pseudohypoparathyroidism: new diagnostic and therapeutic approaches]. Arch Pediatr 2000; 4:86s-90s. [PMID: 9246311 DOI: 10.1016/s0929-693x(97)86469-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J C Carel
- Service d'endocrinologie pédiatrique et Inserm U342, Paris, France
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33
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Abstract
The G proteins are components of a complex membrane signaling system designed to modulate extracellular signals as they are transmitted into the cell. The principal components are the receptor, the G proteins including the alpha, beta, gamma subunits and the effector. Associated with these molecules are several molecular processes by which the signal is transmitted, and regulated including desensitization. Molecules such as arrestin, the RGS (regulators of the G-protein signaling) as well as downstream kinases associated with cyclic AMP are key to regulating the G protein signal. Membrane lipids are key for both anchoring this signal system to the plasma membrane but also in defining the signaling process. Through understanding the biology of the signal system, a number of diseases have been linked to dysfunction of the G protein system. It is clear that this important membrane signal system will become the target for more intense investigation and pharmacologic manipulation to treat critical illness.
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Affiliation(s)
- R A Forse
- Department of Surgery, Boston University School of Medicine, MA, USA
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34
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Weinstein LS, Yu S, Ecelbarger CA. Variable imprinting of the heterotrimeric G protein G(s) alpha-subunit within different segments of the nephron. Am J Physiol Renal Physiol 2000; 278:F507-14. [PMID: 10751211 DOI: 10.1152/ajprenal.2000.278.4.f507] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The heterotrimeric G protein G(s) is required for hormone-stimulated intracellular cAMP generation because it couples hormone receptors to the enzyme adenylyl cyclase. Hormones that activate G(s) in the kidney include parathyroid hormone, glucagon, calcitonin, and vasopressin. Recently, it has been demonstrated that the G(s)alpha gene is imprinted in a tissue-specific manner, leading to preferential expression of G(s)alpha from the maternal allele in some tissues. In the kidney, G(s)alpha is imprinted in the proximal tubule but not in more distal nephron segments, such as the thick ascending limb or collecting duct. This most likely explains why in both humans and mice heterozygous mutations in the maternal allele lead to parathyroid hormone resistance in the proximal tubule whereas mutations in the paternal allele do not. In contrast, heterozygous mutations have little effect on vasopressin action in the collecting ducts. In mice with heterozygous null G(s)alpha mutations (both those with mutations on the maternal or paternal allele), expression of the Na-K-2Cl cotransporter was decreased in the thick ascending limb, suggesting that its expression is regulated by cAMP. The G(s)alpha genes also generate alternative, oppositely imprinted transcripts encoding XLalphas, a G(s)alpha isoform with a long NH(2)-terminal extension, and NESP55, a chromogranin-like neurosecretory protein. The role, if any, of these proteins in renal physiology is unknown.
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Affiliation(s)
- L S Weinstein
- Metabolic Diseases Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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35
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Chagnon YC, Pérusse L, Weisnagel SJ, Rankinen T, Bouchard C. The human obesity gene map: the 1999 update. OBESITY RESEARCH 2000; 8:89-117. [PMID: 10678263 DOI: 10.1038/oby.2000.12] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This report constitutes the sixth update of the human obesity gene map incorporating published results up to the end of October 1999. Evidence from the rodent and human obesity cases caused by single gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTL) uncovered in human genome-wide scans and in crossbreeding experiments with mouse, rat, pig and chicken models, association and linkage studies with candidate genes and other markers is reviewed. Twenty-five human cases of obesity can now be explained by variation in five genes. Twenty Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different QTLs reported from animal models reaches now 98. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 89 reports of positive associations pertaining to 40 candidate genes. Finally, 44 loci have linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map depicted in Figure 1 reveals that putative loci affecting obesity-related phenotypes can be found on all autosomes, with chromosomes 14 and 21 showing each one locus only. The number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes continues to increase and is now well above 200.
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Affiliation(s)
- Y C Chagnon
- Department of Social and Preventive Medicine, Faculty of Medicine, Laval University, Sainte-Foy, Québec, Canada.
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36
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Affiliation(s)
- M A Levine
- The Johns Hopkins University School of Medicine, Division of Pediatric Endocrinology, Department of Pediatrics, Baltimore, Maryland 21287, USA
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37
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Affiliation(s)
- Z Farfel
- Department of Medicine E, Sheba Medical Center, Tel Aviv University, Tel Hashomer, Israel
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38
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Nebes V, Wall J. Membrane Receptor–Linked Disease States. Compr Physiol 1998. [DOI: 10.1002/cphy.cp070112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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39
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Warner DR, Weng G, Yu S, Matalon R, Weinstein LS. A novel mutation in the switch 3 region of Gsalpha in a patient with Albright hereditary osteodystrophy impairs GDP binding and receptor activation. J Biol Chem 1998; 273:23976-83. [PMID: 9727013 DOI: 10.1074/jbc.273.37.23976] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Albright hereditary osteodystrophy (AHO), a disorder characterized by skeletal abnormalities and obesity, is associated with heterozygous inactivating mutations in the gene for Gsalpha. A novel Gsalpha mutation encoding the substitution of tryptophan for a nonconserved arginine within the switch 3 region (Gsalpha R258W) was identified in an AHO patient. Although reverse transcription-polymerase chain reaction studies demonstrated that mRNA expression from wild type and mutant alleles was similar, Gsalpha expression in erythrocyte membranes from the affected patient was reduced by 50%. A Gsalpha R258W cDNA, as well as one with arginine replaced by alanine (Gsalpha R258A), was generated, and the biochemical properties of in vitro transcription/translation products were examined. When reconstituted with cyc- membranes, both mutant proteins were able to stimulate adenylyl cyclase normally in the presence of guanosine- 5'-O-(3-thiotriphosphate) (GTPgammaS) but had decreased ability in the presence of isoproterenol or AlF4- (a mixture of 10 microM AlCl3 and 10 mM NaF). The ability of each mutant to bind and be activated by GTPgammaS or AlF4- was assessed by trypsin protection assays. Both mutants were protected normally by GTPgammaS but showed reduced protection in the presence of AlF4-. The addition of excess GDP (2 mM) was able to rescue the ability of AlF4- to protect the mutants, suggesting that they might have reduced affinity for GDP. A Gsalpha R258A mutant purified from Escherichia coli had decreased affinity for GDP and an apparent rate of GDP release that was 10-fold greater than that of wild type Gsalpha. Sucrose density gradient analysis demonstrated that both Gsalpha R258W and Gsalpha R258A were thermolabile at higher temperatures and that denaturation of both mutants was prevented by the presence of 0.1 mM GTPgammaS or 2 mM GDP. The crystal structure of Gsalpha demonstrates that Arg258 interacts with a conserved residue in the helical domain (Gln170). Arg258 substitutions would be predicted to open the cleft between the GTPase and helical domains, allowing for increased GDP release in the inactive state, resulting in enhanced thermolability and reduced AlF4--induced adenylyl cyclase stimulation and trypsin protection, since activation by AlF4- requires bound GDP.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Adult
- Alanine
- Aluminum Compounds/pharmacology
- Amino Acid Sequence
- Arginine
- Base Sequence
- Binding Sites
- Cloning, Molecular
- Erythrocyte Membrane/metabolism
- Escherichia coli
- Exons
- Female
- Fibrous Dysplasia, Polyostotic/genetics
- Fluorides/pharmacology
- GTP-Binding Protein alpha Subunits, Gs/blood
- GTP-Binding Protein alpha Subunits, Gs/chemistry
- GTP-Binding Protein alpha Subunits, Gs/genetics
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Guanosine Diphosphate/metabolism
- Humans
- Male
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Point Mutation
- Polymerase Chain Reaction
- Protein Biosynthesis
- Protein Structure, Secondary
- RNA, Messenger/genetics
- Receptors, Cell Surface/metabolism
- Recombinant Proteins/metabolism
- Transcription, Genetic
- Tryptophan
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Affiliation(s)
- D R Warner
- Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, NINDS, National Institutes of Health, Bethesda, Maryland 20892, USA.
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40
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Abstract
It has been demonstrated that the majority of secreting and nonsecreting adenomas is monoclonal in origin suggesting that these neoplasia arise from the replication of a single mutated cell, in which growth advantage results from either activation of protooncogenes or inactivation of antioncogenes. Although a large number of genes has been screened for mutations, only few genetic abnormalities have been found in pituitary tumors such as allelic deletion of chromosome 11q13 where the MEN-1 gene has been localised, and mutations in the gene encoding the alpha subunit of the stimulatory Gs and Gi2 protein. These mutations constitutively activate the alpha subunit of the Gs and Gi2 protein by inhibiting their intrinsic GTPase activity. Both Gs alpha and Gi2alpha can be considered products of protooncogenes (gsp and gip2, respectively) since gain of function mutations that activate mitogenic signals have been recognized in human tumors. Gsp oncogene is found in 30-40% of GH-secreting adenomas, in a low percentage of nonfunctioning and ACTH-secreting pituitary adenomas, in toxic thyroid adenomas and differentiated thyroid carcinomas. The same mutations, occurred early in embriogenesis, have been also identified in tissues from patients affected with the McCune Albright syndrome. These mutations result in an increased cAMP production and in the subsequent overactivation of specific pathways involved in both cell growth and specific programmes of cell differentiation. By consequence, the endocrine tumors expressing gsp oncogene retain differentiated functions. The gip2 oncogene has been identified in about 10% of nonfunctioning pituitary adenomas, in tumors of the ovary and the adrenal cortex. However, it remains to be established whether Gi proteins activate mitogenic signals in pituitary cells. Since Gi proteins are involved in mediating the effect of inhibitory neurohormones on intracellular effectors, it has been proposed that in pituitary tumors the low expression of these proteins, particularly Gi1-3alpha, may contribute to uncontrolled pituitary cells growth by preventing the transduction of inhibitory signals. While by in vitro mutagenesis it has been demonstrated that activated mutant of Gq alpha, G12alpha, G13alpha and Gz alpha are fully oncogenic, it remains to be proved whether or not these abnormalities might naturally occur in human tumors and, in particular, in pituitary adenomas.
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Affiliation(s)
- A Spada
- Institute of Endocrine Sciences, University of Milan, Ospedale Maggiore IRCCS, Milano, Italy.
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41
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Abstract
How does a trimeric G protein on the inside of a cell membrane respond to activation by a transmembrane receptor? G-protein mutations in patients with hypertension and inherited endocrine disorders enhance or block signals from stimulated receptors. In combination with three-dimensional crystal structures and results from biochemical experiments, the phenotypes produced by these mutations suggest a model for the molecular activation mechanism that relays hormonal and sensory signals transmitted by many transmembrane receptors.
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Affiliation(s)
- T Iiri
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco 94143-0450, USA
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42
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Korswagen HC, Park JH, Ohshima Y, Plasterk RH. An activating mutation in a Caenorhabditis elegans Gs protein induces neural degeneration. Genes Dev 1997; 11:1493-503. [PMID: 9203577 DOI: 10.1101/gad.11.12.1493] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Heterotrimeric guanine nucleotide-binding proteins (G proteins) act as signal-transducing molecules that connect serpentine-transmembrane receptors to a variety of intracellular effectors. We characterized a Caenorhabditis elegans G(s) gene, gsa-1, which encodes a G(s) alpha-subunit (G alpha(s)) that is expressed throughout the nervous system and in muscle cells. gsa-1 is an essential gene; a loss-of-function mutation in gsa-1 results in lethality at the first stage of larval development. Partial (mosaic) loss of G alpha(s) expression or overexpression of the protein results in reciprocal defects in movement and egg-laying, suggesting a role for G alpha(s) in the regulation of these behaviors. Expression of a constitutively active form of G alpha(s) from an inducible promotor results in hypercontraction of body-wall muscle cells and vacuolization and degeneration of neurons within hours of induction. Neurons that are susceptible to the degeneration induced by activated G alpha(s) are predominantly motoneurons located within the ventral nerve cord. Phenotypic analysis shows that the induced neural degeneration is not the result of programmed cell death but is probably caused by the activation of ion channels. A genetic suppressor of activated G alpha(s) was isolated that identifies a putative downstream target of G(s) signaling.
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Affiliation(s)
- H C Korswagen
- Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam
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43
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Farfel Z, Iiri T, Shapira H, Roitman A, Mouallem M, Bourne HR. Pseudohypoparathyroidism, a novel mutation in the betagamma-contact region of Gsalpha impairs receptor stimulation. J Biol Chem 1996; 271:19653-5. [PMID: 8702665 DOI: 10.1074/jbc.271.33.19653] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Pseudohypoparathyroidism, type Ia (PHP-Ia), is a dominantly inherited endocrine disorder characterized by resistance to hormones that act by stimulating adenylyl cyclase. It is caused by inheritance of an autosomal mutation that inactivates the alpha subunit (alphas) of Gs, the stimulatory regulator of adenylyl cyclase. In three members of a family, the PHP-Ia phenotype is associated with a mutation (R231H) that substitutes histidine for an arginine at position 231 in alphas. We assessed signaling function of alphas-WT versus alphas-R231H transiently transfected in HEK293 cells. Hormone receptor-dependent stimulation of cAMP accumulation in cells expressing alphas-R231H is reduced by approximately 75% in comparison to cAMP accumulation in cells expressing alphas-WT. A second mutation, alphas-R201C, inhibits the GTPase turnoff reaction of alphas, thus producing receptor-independent stimulation of cAMP accumulation. The double mutant, alphas-R231H/R201C, stimulates cAMP accumulation almost as well (approximately 80%) as does alphas-R201C itself, indicating that the R231H mutation selectively impairs receptor-dependent signaling. In three-dimensional structures of G protein heterotrimers, Arg-231 is located in a region, switch 2, that is thought to interact with the betagamma subunit rather than with the hormone receptor. Thus, the R231H phenotype suggests that switch 2 (perhaps in concert with betagamma) mediates G protein activation by receptors at a site distant from the receptor-G protein contact surface.
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Affiliation(s)
- Z Farfel
- Laboratory of Biochemical Pharmacology, Sheba Medical Center, Tel Aviv University, Tel Hashomer 52621, Israel
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44
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Ringel MD, Schwindinger WF, Levine MA. Clinical implications of genetic defects in G proteins. The molecular basis of McCune-Albright syndrome and Albright hereditary osteodystrophy. Medicine (Baltimore) 1996; 75:171-84. [PMID: 8699958 DOI: 10.1097/00005792-199607000-00001] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Inactivating and activating mutations in the gene encoding G alpha s (GNAS1) are known to be the basis for 2 well-described contrasting clinical disorders, Albright hereditary osteodystrophy (AHO) and McCune-Albright syndrome (MAS). AHO is an autosomal dominant disorder due to germline mutations in GNAS1 that decrease expression or function of G alpha s protein. Loss of G alpha s function leads to tissue resistance to multiple hormones whose receptors couple to G alpha s. By contrast, MAS results from postzygotic somatic mutations in GNAS1 that lead to enhanced function of G alpha s protein. Acquisition of the activating mutation early in life leads to a more generalized distribution of the mosaicism and is associated with the classic clinical triad of polyostotic fibrous dysplasia, endocrine hyperfunction, and café au lait skin lesions described in MAS. Acquisition of a similar activating mutation in GNAS1 later in life presumably accounts for the restricted distribution of the gsp oncogene, and is associated with the development of isolated lesions (for example, fibrous dysplasia, pituitary or thyroid tumors) without other manifestations of MAS. Tissues that are affected by loss of G alpha s function in AHO are also affected by gain of G alpha s function in MAS, thus identifying specific tissues in which the second messenger cAMP plays a dominant role in cell growth, proliferation, or function. Further investigations of the functions of G alpha s and other members of the GTPase binding protein family will provide more insight into the pathogenesis and clinical manifestations of human disease.
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Affiliation(s)
- M D Ringel
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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45
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Yokoyama M, Takeda K, Iyota K, Okabayashi T, Hashimoto K. A 4-base pair deletion mutation of Gs alpha gene in a Japanese patient with pseudohypoparathyroidism. J Endocrinol Invest 1996; 19:236-41. [PMID: 8862504 DOI: 10.1007/bf03349874] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Mutations in the guanine nucleotide binding protein alpha subunit (Gs alpha) have been found in patients with pseudohypoparathyroidism (PHP). We have screened the Gs alpha gene for mutations in a Japanese patient with this disorder and identified a novel 4-base pair deletion in exon 7 in codons 189-190. This deletion causes a frameshift and if synthesis of a truncated form of Gs alpha occurred, it would likely be biologically inactive. The patient was heterozygous for this deletion. The patient's mother and an unaffected brother were tested for the presence of this mutation. His mother had the same mutation, and although her serum calcium and parathyroid hormone levels were within the normal range, she had subcutaneous calcifications. Thus, this mutation appears to be necessary but not sufficient to cause the complete pseudohypoparathyroidism phenotype and thus, other unknown factors, either genetic or acquired, may be necessary for the full syndrome to occur.
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Affiliation(s)
- M Yokoyama
- Second Department of Internal Medicine, Kochi Medical School, Japan
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46
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Martin EL, Rens-Domiano S, Schatz PJ, Hamm HE. Potent peptide analogues of a G protein receptor-binding region obtained with a combinatorial library. J Biol Chem 1996; 271:361-6. [PMID: 8550587 DOI: 10.1074/jbc.271.1.361] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The C terminus of the G protein alpha subunit represents an important site of interaction between heterotrimeric G proteins and their cognate receptors. We have screened a combinatorial peptide library based on the C terminus of the alpha subunit of Gt (340-350) and have identified unique sequences that bind rhodopsin with high affinity. Six of these sequences, as both fusion proteins and synthetic peptides, were significantly more potent than the parent sequence in binding to and stabilization of metarhodopsin II. These sequences provide information about which residues are required for appropriate receptor interaction. We observed that in all the high affinity sequences, a positively charged residue at position 341 was changed to a neutral one. Thus, it appears that the receptor-G protein interaction was designed to be low affinity to ensure efficient catalysis of G protein activation. We also observed Cys-347 and Gly-348 to be invariant, and hydrophobic residues were always located at positions 340, 344, 349, and 350, demonstrating the critical nature of these residues. A composite of the structures of the high affinity sequences was modeled based upon the structure of rhodopsin-bound trNOESY NMR of this region of Gt alpha (Dratz, E. D., Fursteneau, J. E., Lambert, C. G., Thireault, D. L., Rarick, H., Schepers, T., Pakhlevaniants, S., and Hamm, H. E. (1993) Nature 363, 276-280) and provides insight into the complementary G protein-binding surface of the receptor.
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Affiliation(s)
- E L Martin
- Affymax Research Institute, Palo Alto, California 94304, USA
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47
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Milligan G. Endocrine disorders associated with mutations in guanine nucleotide binding proteins. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1996; 10:177-87. [PMID: 8734456 DOI: 10.1016/s0950-351x(96)80378-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The basis for a number of relatively rare endocrine diseases, which present clinically with features of AHO, have been shown conclusively to result from mutations in the G3 alpha gene which interfere with the expression of functional protein. Individual kindreds display a range of specific mutations in this gene. A further series of disorders result from somatic mutations of the G3 alpha gene which result in constitutive activation (in one case probably with a concomitant decrease in stability of the expressed protein). When such a mutation occurs in early embryogenesis it can result in a pattern of mosaicism of expression of clinical features in the patient. Despite these cases, equivalent alterations in other G-protein alpha subunit genes seem to be of limited importance in human disease. This is despite biochemical data from a range of experimental cell models which indicate that such mutations can have potent effects on cell growth and division.
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Affiliation(s)
- G Milligan
- Division of Biochemistry and Molecular Biology, University of Glasgow, Scotland, UK
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48
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Phelan MC, Rogers RC, Clarkson KB, Bowyer FP, Levine MA, Estabrooks LL, Severson MC, Dobyns WB. Albright hereditary osteodystrophy and del(2) (q37.3) in four unrelated individuals. AMERICAN JOURNAL OF MEDICAL GENETICS 1995; 58:1-7. [PMID: 7573148 DOI: 10.1002/ajmg.1320580102] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Albright hereditary osteodystrophy (AHO) is a condition with characteristic physical findings (short stature, obesity, round face, brachydactyly) but variable biochemical changes (pseudohypoparathyroidism, pseudopseudohypoparathyroidism). Most patients with AHO have decreased activity of the guanine nucleotide-binding protein (GS protein) that stimulates adenylyl cyclase. The gene encoding the alpha subunit of the GS protein (GNAS1) has been mapped to the long arm of chromosome 20. We describe 4 unrelated individuals with apparent AHO, associated with small terminal deletions of chromosome 2. All 4 patients had normal serum calcium levels consistent with pseudopseudohypoparathyroidism. Del(2) (q37) is the first consistent karyotypic abnormality that has been documented in AHO [Phelan et al., 1993: Am J Hum Genet 53:484]. The finding of the same small terminal deletion in 4 unrelated individuals with a similar phenotype suggests that a gene locus in the 2q37 region is important in the pathogenesis of Albright syndrome. The association of Albright syndrome and the GNAS1 locus on chromosome 20 is well documented. The observation of a second potential disease locus on chromosome 2 may help explain the heterogeneity observed in this disorder.
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Affiliation(s)
- M C Phelan
- Greenwood Genetic Center, South Carolina, USA
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