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Pateman, Cassandra Sophie Catherine. "RGS proteins and G protein signalling." Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/2367/.
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The work within this thesis is concerned with the creation of a temperature-sensitive Schizosaccharomyces pombe marker protein, and the regulation of the pheromone communication system of Sz. pombe reporter strains by RGS proteins. There are a limited number of marker proteins available for use in the genetic manipulation of Sz. pombe, and the generation of a temperature-sensitive Ura4p was envisaged to expand the scope of carrying out sequential gene disruptions in the fission yeast. PCR-based mutagenesis was used to introduce mutations in the ura4 cassette, and a leucine to proline mutation identified at residue 261 in the ura4 open reading frame conferred a temperature-sensitive requirement for uracil. To demonstrate the use of the Ura4sp marker in gene disruption, the Sz. pombe irpl gene was disrupted with the ura4u cassette, and subsequently, the prkl gene was disrupted with the wild-type ura4 cassette. RGS proteins are a recently discovered family of proteins that negatively regulate G protein-coupled signalling pathways. This thesis describes the ability of mammalian RGS proteins to regulate the pheromone communication system of Sz. pombe reporter strains. Human RGS 1 and human RGS4 displayed the greatest ability to negatively regulate the Sz. pombe pheromone signalling pathway when expressed from multicopy expression vectors. Human RGS2, human RGS3, human RGS9-2 and murine RGS2 displayed lesser, varying abilities. Expression of human RGS 1 from single copy reduced signalling at low pheromone concentrations. Expression of human RGS4 from single copy was incapable of reducing pheromone-independent and pheromone-dependent signalling. This thesis also describes the search for gain-of-function RGS proteins. Two potential gain-of-function szRgslp mutants were previously identified, and these mutants were recreated. The two mutations identified (histidine to arginine at szRgslp residue 171 and valine to isoleucine at szRgslp residue 305) conferred gain-of-function szRgslp phenotypes in an sxa2:: ura4 reporter strain. Hydroxylamine treatment of the human RGS4 open reading frame resulted in the identification of a potential gain-of-function RGS4 mutant. The lysine to arginine mutation at huRGS4p residue 20 conferred a gain-of-function huRGS4p phenotype in an sxa2:: ura4 reporter strain.
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Mohr, Andrea. "Protein-Protein-Interaktionen des G-CSFR." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960605398.
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Humrich, Jan. "G-Protein betagamma-Regulation durch Phosducin-like Proteine." kostenfrei, 2009. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2009/4005/.
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Higgs, C. "A computational study of the G-protein-G-protein coupled receptor interaction." Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324216.
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Howlett, Alyson Cerny. "Role of molecular chaperones in G protein B5-Regulator of G protein signaling dimer assembly and G protein By dimer specificity." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2065.
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In order for G protein signaling to occur, the G protein heterotrimer must be assembled from its nascent polypeptides. The most difficult step in this process is the formation of the Gβγ dimer from the free subunits since both are unstable in the absence of the other. Recent studies have shown that phosducin-like protein (PhLP1) works as a co-chaperone with the cytosolic chaperonin complex (CCT) to fold Gβ and mediate its interaction with Gγ. However, these studies did not address questions concerning the scope of PhLP1 and CCT-mediated Gβγ assembly, which are important questions given that there are four Gβs that form various dimers with 12 Gγs and a 5th Gβ that dimerizes with the four regulator of G protein signaling (RGS) proteins of the R7 family. The data presented in Chapter 2 shows that PhLP1 plays a vital role in the assembly of Gγ2 with all four Gβ1-4 subunits and in the assembly of Gβ2 with all twelve Gγ subunits, without affecting the specificity of the Gβγ interactions. The results of Chapter 3 show that Gβ5-RGS7 assembly is dependent on CCT and PhLP1, but the apparent mechanism is different from that of Gβγ. PhLP1 seems to stabilize the interaction of Gβ5 with CCT until Gβ5 is folded, after which it is released to allow Gβ5 to interact with RGS7. These findings point to a general role for PhLP1 in the assembly of all Gβγ combinations, and suggest a CCT-dependent mechanism for Gβ5-RGS7 assembly that utilizes the co-chaperone activity of PhLP1 in a unique way. Chapter 4 discusses PhLP2, a recently discovered essential protein, and member of the Pdc family that does not play a role in G protein signaling. Several studies have indicated that PhLP2 acts as a co-chaperone with CCT in the folding of actin, tubulin, and several cell cycle and pro-apoptotic proteins. In a proteomics screen for PhLP2A interacting partners, α-tubulin, 14-3-3, elongation factor 1α, and ribosomal protein L3 were found. Further proteomics studies indicated that PhLP2A is a phosphoprotein that is phosphorylated by CK2 at threonines 47 and 52.
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Kong, Janice 1978. "G-protein coupled receptors (GPCRs) modulate regulator of G-protein signaling (RGS) selectivity." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33013.
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Regulators of G-protein Signaling (RGSs) are negative regulators of G-protein Coupled Receptor (GPCR) mediated signaling that function to limit the lifetime of receptor-activated Galpha proteins. Heterologously expressed mammalian RGSs can functionally complement a yeast mutant lacking its RGS containing gene SST2. Here we show that four mammalian RGSs differentially inhibit the activation of a FUS1-LacZ reporter gene by the STE2 encoded GPCR in yeast with the apparent rank order potency: RGS1 > RGS16 > RGS2 > RGS5. In order to examine the role of the GPCR in modulating RGS function, we functionally expressed the human somatostatin receptor 5 (SSTR5) in yeast.The ability of RGSs to inhibit SSTR5 signaling was further assessed in cells expressing modified Gpa1 proteins.
Yeast have also been shown to be a useful model organism for the study of the localization of mammalian RGS proteins. We have constructed a series of vectors that allow us to express proteins fused to a Green Fluorescent Protein (GFP). (Abstract shortened by UMI.)
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Fransen, Maikel Peter. "Stabilizing the G protein-coupled receptor rhodopsin/heterotrimeric G protein transducin signalling complex." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610816.
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Guillemot, Jean-Claude. "Contribution à l'étude des petites protéines -G." Toulouse 3, 1995. http://www.theses.fr/1995TOU30216.
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L'adnc humain de d4-gdi a ete clone au laboratoire par soustraction de banque d'adnc entre lignees hematopoietiques et non hematopoietiques. Au niveau acides amines, ce gene montre une homologie de 68% avec rho-gdi, inhibiteur de la dissociation du gdp pour rho. La famille des proteines ras, les petites proteines g, se comporte de plusieurs sous-groupes: ras/raf, rab, tc4/ran et rho. L'analyse par northern du profil d'expression de d4-gdi nous a montre qu'il est exprime preferentiellement dans les cellules hematopoietiques. Afin d'etudier ce gene, nous en avons etabli une mutation nulle par recombinaison homologue dans des cellules embryonnaires souches de souris. Plusieurs laboratoires, dont le notre, ont decrit la possibilite d'obtenir une differenciation hematopoietique in vitro a partir de cellules es. Nous avons ainsi montre que d4-gdi n'est pas implique dans l'hematopoiese
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Howlett, Alyson Cerny. "Role of molecular chaperones in G protein "beta"5-regulator of G protein signaling dimer assembly and G protein "beta""gamma" specificity /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2874.pdf.
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Sheng, Yinglun. "G protein signaling and G protein coupled receptor (GPCR) pathway in Xenopus oocyte maturation." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/29262.
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Xenopus laevis oocytes are physiologically arrested at the first meiotic prophase. Progesterone reinitiates meiosis (maturation) through inhibition of an oocyte adenylyl cyclase (AC) and reduction of intracellular cAMP. However, the mechanism by which progesterone regulates AC activity and cAMP level still remains unclear.
In this thesis, I summarize work I conducted that collectively helps elucidate how high levels of cAMP might be achieved in G2 arrested oocytes. In Chapter 2, I describe our finding that inhibiting endogenous G-protein betagamma subunits, through the use of two structurally distinct Gbetagamma scavengers, causes hormone-independent oocyte maturation. In contrast, overexpression of Xenopus Gbeta1, alone or together with bovine Ggamma2, inhibits progesterone-induced oocyte maturation. These results for the first time implicate that an endogenous G protein coupled receptor system releases a Gbetagamma complex as the dominant meiosis inhibitor.
Chapter 3 describes my research aiming to reveal the identity of the oocyte AC responsible for generating meiosis-inhibiting cAMP. I provide further evidence here that the ability of Gbetagamma to inhibit meiosis is attributed to the activation of an endogenous AC, rather than other possible Gbetagamma effectors. Through molecular cloning and biochemical characterization, I discovered that the likely AC candidate is Xenopus AC7, an isoform that is activated by Gbetagamma, but only in the presence of GTP-bound Gsalpha. The identification of xAC7 suggests that the maintenance of high levels of cAMP may require the cooperation of Gsalpha and Gbetagamma.
Finally, in Chapter 4, I describe our efforts in identifying the GPCR(s) responsible for activating the cAMP signaling in prophase-arrested oocytes. A screening of known antagonists of GPCR(s) led to the identification of ritanserin, a potent antagonist of serotonin receptors, as a potent maturation inducer in Xenopus oocytes. Pharmacological and molecular studies, however, have ruled out the involvement of a known serotonin receptor in meiosis arrest. Instead, the most likely candidate is a "constitutively activated" GPCR that bears structural similarities to Xenopus serotonin receptor 7.
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Brockmann, Jörg. "Regulation G-Protein-gekoppelter Rezeptorkinasen." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979675677.
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Marchese, Adriano. "Orphan G protein-coupled receptors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq41468.pdf.
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Ghimire, Ganga D., ガンガ Ｄ. ギミレ, Kenichiro Imai, 賢一郎 今井, Fumitsugu Akazawa, 史嗣 赤沢, Toshiyuki Tsuji, et al. "Physicochemical properties of amino acid sequences of G-proteins for understanding GPCR-G-protein coupling." Chem-Bio Informatics Society, 2006. http://hdl.handle.net/2237/9277.
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Gros, Robert. "Regulation of G-protein-coupled receptor function, a role for increased G-protein-coupled receptor kinase-2 protein content." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/NQ58133.pdf.
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Kikkou, Tatsuhiko. "NMR structural analysis of G protein activation peptides derived from seven transmembrane G protein-coupled receptors." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124071.
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Lai, Chun Wan Jeffrey. "Mechanism of G Protein Beta-Gamma Assembly Mediated by Phosducin-Like Protein 1." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3190.
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G-protein coupled receptor signaling (GPCR) is essential for regulating a large variety of hormonal, sensory and neuronal processes in eukaryotic cells. Because the regulation of these physiological responses is critical, GPCR signaling pathways are carefully controlled at different levels within the cascade. Phosducin-like protein 1 (PhLP1) can bind the G protein βγ dimer and participate in GPCR signaling. Recent evidence has supported the concept that PhLP1 can serve as a co-chaperone of the eukaryotic cytosolic chaperonin complex CCT/TRiC to mediate G βγ assembly. Although a general mechanism of PhLP1-mediated G βγ assembly has been postulated, many of the details about this process are still missing. Structural analysis of key complexes that are important intermediates in the G βγ assembly process can generate snapshots that provide molecular details of the mechanism beyond current understanding. We have isolated two important intermediates in the assembly process, the Gβ1-CCT and PhLP1-Gβ1-CCT complexes assembled in vivo in insect cells, and have determined their structures by cryo-electron microscopy (cryo-EM). Structural analysis reveals that Gβ1, representing the WD40 repeat proteins which are a major class of CCT substrates, interacts specifically with the apical domain of CCTβ. Gβ1 binding experiments with several chimeric CCT subunits confirm a strong interaction of Gβ1 with CCTβ and map Gβ1 binding to α-Helix 9 and the loop between β-strands 6 and 7. These regions are part of a hydrophobic surface of the CCTβ apical domain facing the chaperonin cavity. Docking the Gβ molecule into the two 3D reconstructions (Gβ1-CCT and PhLP1-Gβ1-CCT) reveals that upon PhLP1 binding to Gβ1-CCT, the quasi-folded Gβ molecule is constricted to a more native state and shifted to an angle that can lead to the release of folded Gβ1 from CCT. Moreover, mutagenesis of the CCTβ subunit suggests that PhLP1 can interact with the tip of the apical domain of CCTβ subunit at residue S260, which is a downstream phosphorylation target site of RSK and S6K kinases from the Ras-MAPK and mTOR pathways. These results reveal a novel mechanism of PhLP1-mediated Gβ folding and its release from CCT. The next important step in testing the PhLP1-mediated Gβγ assembly hypothesis is to investigate the function of PhLP1 in vivo. We have prepared a rod-specific PhLP1 conditional knockout mouse in which the physiological consequences of the loss of PhLP1 functions have been characterized. The loss of PhLP1 has led to profound consequences on the ability of these rods to detect light as a result of a significant reduction in the expression of transducin (Gt) subunits. Expression of other G protein subunits as well as Gβ5-RGS9-1 complexes was also greatly decreased, yet all of this occurs without resulting in rapid degeneration of the photoreceptor cells. These results show for the first time the essential nature of PhLP1 for Gβγ and Gβ5-RGS dimer assembly in vivo, confirming results from cell culture and structural studies.
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Gräler, Markus. "Der G-Protein-gekoppelte Rezeptor EDG6." [S.l. : s.n.], 2000. http://www.diss.fu-berlin.de/2001/6/index.html.
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Kidley, N. J. "Modelling G protein-coupled receptor activation." Thesis, University of Essex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402792.
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Ja, William Wei-Hua Rees Douglas C. "Peptide modulators of G protein signaling /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-01032005-161114.
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Yang, Zhao 1970. "Identification of a novel anti-apoptotic protein and characterization of mammalian regulators of G protein signaling (RGSs) in yeast." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111875.
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Regulators of G protein signaling (RGSs) are negative regulators of G protein coupled receptors (GPCRs). Our lab has demonstrated that yeast Saccharomyces cerevisiae is a useful system to study RGS and G protein signaling. Mammalian RGSs can be expressed in yeast and favored to interact with mammalian GPCRs as well.Based on the observation that human RGS1 causes yeast cell growth arrest, I therefore used RGS1 expressing yeast cells to screen a mouse T cell cDNA library in order to find potential interacting proteins. From the screen, I identified a mouse sphingomyelin synthase 1 (SMS1) cDNA. By using a series of different apoptotic stimuli, such as hydrogen peroxide, osmotic stress, exogenous ceramide and its precursors, high temperature etc., SMS1 expression was found to suppress cell growth arrest and prevent viability decline, indicating that SMS1 represents an anti-apoptotic protein that functions by decreasing the intracellular level of pro-apoptotic ceramide.
Gene analysis further indicated that the SMS1 gene consists of 16 exons spread over a 256kb portion of mouse chromosome 19. It is alternatively spliced to produce 4 different transcripts (SMS1alpha1, SMS1alpha2, SMS1beta and SMS1gamma) and encode 3 different proteins (SMS1alpha, SMS1beta and SMS1gamma). Notably, I found that SMS1beta protein does not interfere with SMS1alpha anti-apoptotic function, although both of these two proteins contain the protein-protein interaction domain, sterile alpha motif (SAM), at their N-terminus.
I also carried out a study to examine GPCR-RGS interactions using the yeast expression system. Our lab had noticed that there was an extra RGS5 related protein that was detected by western blot analysis in the protein extracts prepared from yeast and HEK293 cells expressing RGS5. The size of the band was approximately 2 times the molecular weight of RGS5, indicating the possibility that RGS5 forms a dimer. To further examine this hypothesis, I, therefore, performed a series of experiments, included yeast 2 hybrid assays, to demonstrate that RGS5 does interact with itself. This is the first report that RGS can form a dimer. The implications for this finding are discussed in detail.
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Lauffer, Benjamin E. L. "Protein interactions mediating endocytic recycling of G protein-coupled receptors." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3339215.
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Walker, Karen Nicola. "Protein engineering and characterisation of an IgG-binding domain based upon protein G from Streptococcus group G." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296376.
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Han, Li. "G protein coupled receptor signaling to phospholipase D1 mediated by G12 type G proteins, LIM kinase and cofilin." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968929923.
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Conti, Sofia Alessandra. "Monoclonal antibodies purification via Protein G and protein A affinity chromatography." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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realization of a pilot scale affinity protein G chromatography for the purification of small volumes of supernatant from different harvests from the same antibody clone. The objective was to make a study on the productivity of each harvest, investigating for a dilution effect in case of an increasing number of harvests, and to have a rapid retention kit for the quality control of the purified antibody. Moreover, an identical column packed with protein A has been tested with the same products, in order to see if there was space for a yield improvement, and a further scale-up.
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Gata, Gabriel. "Regulated export of G-protein coupled receptors." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05T066.
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La plus grande famille de récepteurs membranaires est constituée par des récepteurs à sept domaines transmembranaires couplés aux protéines G (RCPG). Ces récepteurs sont impliqués dans un grand nombre de réponses cellulaires physiologiques et pathologiques et représentent la ciblé de une grande majorité des produits thérapeutiques. La fonction d’un récepteur est déterminée par la quantité de récepteur fonctionnel à la surface cellulaire, qui dépend de différents paramètres comme le niveau de biosynthèse, l’export vers la surface cellulaire à partir de stocks intracellulaires, l’endocytose et les modifications post-transcriptionelles (ex. phosphorylation). Le nouveau concept d’export régulé pour les RCPG présent l’importance physiologique de la rétention de récepteurs, leur relargage, leur interaction avec les partenaires chaperonnes et les escortes. Les études présentées ici concernent les mécanismes d’export régulé de deux RCPG, le récepteur métabotropique de l’acide γ-amino butyrique (GABAB) et le récepteur de chimiokines CC 5 (CCR5). GABAB est un récepteur constitué de deux sous-unités GB1 et GB2 et CCR5 est probablement un homo-dimer. GB1 ainsi que CCR sont retenus dans des compartiments intracellulaire (RE et appareil Golgi) d’où ils sont relâchés en réponse à un signal extern (CCR5) ou/et en interagissant avec protéines d’escorte (comme CD4 pour CCR5 et GB2 pour GB1). L’objectif de ces études était de comprendre le mécanisme de rétention de ces récepteurs et leur régulation. Dans ce contexte, nous avons déterminé en utilisant des approches biophysiques et biochimiques que ces récepteurs interagissent de façon spécifique avec les membres de Prenylated Rab Acceptors Family (PRAF). Ces protéines sont résidentes dans le RE (PRAF2 et PRAF3) et dans le appareil Golgi (PRAF1) où elles fonctionnent comme de gatekeepers pour les récepteurs. Nous avons pu démontrer que PRAF2 interagie de manière spécifique avec des motifs de rétention connus pour leur implication dans la rétention de récepteurs. Cette interaction détermine une rétention au niveau de RE donc régule de façon négatif l’export vers la membrane cellulaire. Dans le cas de récepteur GABAB, l’interaction de GB2 avec GB1 permet la libération de GB1 de sa rétention par PRAF2 par simple compétition. La modification de l’équilibre stoichiométrique entre les gatekeepers PRAF et les protéines d’escorte pour les récepteurs induit des modifications de la fonction du récepteur in vitro et in vivo. Les PRAFs sont ubiquitaires et peuvent interagir avec plusieurs RCPG représentant dans ce cas des régulateurs majors de la fonction de RCPG dans des conditions physiologiques et pathologiquesThe largest family of membrane receptors is constituted by conserved seven-membrane domain spanning receptors, the G-protein coupled receptors (GPCRs). They are involved in numerous cell responses and diseases thus being a major drug target. Receptor function is determined by the amount of active receptors at the cell surface, which depends on various parameters, such as the biosynthetic rate, the export to the cell surface from internal stores, the endocytosis and post-transcriptional modifications (i.e. phosphorylation). Only recently, the importance of the regulated export has emerged, shedding new light on the physiological role of receptor retention, release, chaperoning and escorting. This work concerns the regulated export mechanisms of two members of the GPCRs family, the chemokine receptor 5 (CCR5) and the metabotropic receptor of the g amino butyric acid (GABAB). Whereas CCR5 is likely a homo-dimer of 2 identical protomers, GABAB is an obligatory hetero-dimer of 2 distinct subunit known as GB1 and GB2. Both CCR5 and GB1 are retained in intracellular compartments (the ER and the Golgi) from which they are released in response to external signals (CCR5) and/or interaction with “private escort proteins” (CD4 for CCR5 and GB2 for GB1). The main goal of our work was to understand the mechanism of retention of these receptors and its regulation. In this context, we determined using biochemical and biophysical approaches that these GPCRs specifically interact with the members of the Prenylated Rab Acceptor Family (PRAF). These proteins are resident either in the ER (PRAF2 and PRAF3) or in the Golgi apparatus (PRAF1) where they function as receptor gatekeepers. Indeed, we could document for PRAF2 that this protein likely interacts directly with previously identified receptor retention motifs and inhibits receptor egress from the ER and subsequent trafficking to the plasma membrane. In the context of the GABAB receptor, PRAF2-dependent retention of GB1 can be overridden by GB2 via simple competition. Perturbing the stoichiometry of PRAF gatekeepers respective to that of receptors significantly perturbs receptor function both in vitro and in vivo. Because PRAFs are ubiquitous and seem to interact with many other GPCRs, they might represent major regulators of receptor function both in physiological and pathological conditions
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Dasso, Leonardo. "Receptor-G protein interactions in rat hepatocytes." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282114.
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White, Colin D. "Dissection of GnRH receptor-G protein coupling." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3885.
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Hypothalamic gonadotropin-releasing hormone (GnRH) (GnRH I) is the central regulator of the mammalian reproductive system. Most vertebrates studied also possess a second form of GnRH, GnRH II. GnRH I acts on its cognate G proteincoupled receptor (GPCR) on pituitary gonadotropes and activates Gq/11-mediated signalling pathways to stimulate the biosynthesis and the release of luteinising hormone (LH) and follicle-stimulating hormone (FSH). Both GnRHs have also been suggested to inhibit cellular proliferation, an action which has largely been proposed to be mediated by the coupling of the receptor to Gi/o. However, the range of G proteins activated by the GnRH receptor and the signalling cascades involved in inducing antiproliferation remain controversial. To delineate the G protein coupling selectivity of the mammalian GnRH receptor and to identify the signalling pathways involved in GnRH I-mediated cell growth inhibition, I examined the ability of the receptor to interact with Gq/11, Gi/o and Gs in Gαq/11 knockout MEF cells. My results indicate that the receptor is unable to interact with Gi/o but can signal through Gq/11. Additionally, my data do not support the suggestion of GnRH receptor-Gs interaction. Furthermore, I show that the GnRH Iinduced inhibition of cell growth is dependent on Gq/11, src and extracellular signal regulated kinase (ERK) but is independent of the activity of protein kinase C (PKC), Ca2+, jun-N-terminal kinase (JNK) or P38. Based on these findings and previous research within our group, I propose a mechanism whereby GnRH I may induce antiproliferation. Previous studies from our laboratory suggest that the GnRH receptor can adopt distinct active conformations in response to the binding of GnRH I and GnRH II. These data thus account for our hypothesis of ligand-induced selective signalling (LiSS). Given my previous results, I examined the ability of the GnRH receptor to couple to G12/13. My work indicates that the receptor can directly activate G12/13 and the downstream signalling cascades associated with this G protein family. Indeed, I provide evidence, in several cellular backgrounds, to suggest that GnRH receptor- G12/13-mediated signalling is involved in the regulation of GnRH-induced MAPK activity, SRE-driven gene transcription and cytoskeletal reorganisation. Furthermore, I propose a role for these G proteins in the transcriptional regulation of LHβ and FSHβ. Finally, I confirm previous results from our laboratory indicating that the GnRH receptor may interact with src Tyr kinase and show that GnRH I but not GnRH II may, independently of Gq/11, stimulate the Tyr phosphorylation and thus the activation of this protein. I propose that this differential signalling accounts for the distinct effects of GnRH I and GnRH II on cellular morphology and SREpromoted transcriptional activity. The research presented within this thesis provides evidence to refute published conclusions based on largely circumstantial experimental data, describes novel GnRH receptor signalling pathways and offers support for the concept of LiSS. It may assist in the development of new therapeutic compounds which selectively target one GnRH-mediated signalling pathway while bypassing others.
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Taddese, Bruck. "Computational modelling of G protein-coupled receptors." Thesis, University of Essex, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589439.
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G protein-coupled receptors (GPCRs) comprise the most "drugable" family of transmembrane proteins, GPCRs share a common structural template and a general mechanism of signal transduction, but vary greatly in sequence conservation, ligand recognition and function. The current set of class A GPCR crystal structures have facilitated the modelling of class A GPCRs. However, other classes of GPCRs have not been so easy to study. The main focus presented in this thesis is the utilisation of class A GPCR structural information to model medically important GPCRs other than class A GPCRs via molecular modelling. The lack of sequence conservation hampers modelling non-class A GPCRs using class A GPCR crystal structures. A plant GPCR, namely GCR1, has sequence homology to more than one GPCR family (class A, Band E GPCRs) and has been used to align the transmembrane region of class A and B GPCRs. Consequently, we have presented a computational protocol for the identification of putative plant GPCRs that may similarly be used to address the difficult issue of alignment between GPCR families but in this respect only GCR1 was found to be useful. GCR1 is still an orphan GPCR with no known cognate ligand. We first assessed whether GCR 1 was a valid GPCR via homology modelling and molecular dynamics. We found that GCR1 has more similarities to class A and class S GPCRs than was previously acknowledged and further support evidence that GCR1 is a GPCR. Consequently, using the class A - GCR1 - class B alignment, we have produced active and inactive homology models of the CGRP receptor, a prototypical class B GPCR. In conjunction with mutation data, these models were used to identify a number of distinct class B motifs and their class A equivalents for the first time. Finally, molecular dynamic simulations were used to further confirm the role of the class B motifs.
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Ho, H. M. I. "Regulation of G protein-gated K+channels." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604105.
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The aims of my project were (i) to elucidate the molecular mechanism of Na+-dependent activation of GIRK channel, and (ii) to investigate the effect of intracellular acidification on GIRK channel activity. Intracellular Na+ dose-dependently activated the wild type GIRK2 homomeric and GIRK1/GIRK2 heteromeric channels. The proximal C-terminal region of the GIRK2 subunit was shown to mediate the Na+-dependent activation of both homomeric and heteromeric channels. Within this region, GIRK2 has an aspartate at position 226, whereas GIRK1 has an asparagine at the equivalent position (217). A single point mutation, D226N, in GIRK2, abolished the Na+-dependent activation of both the homomeric and heteromeric channels without affecting their ability to be activated via the m2-muscarinic receptors. Neutralizing a nearby charge, E234S had no effect. A reverse mutation in the GIRK1 subunit, N217D, was sufficient to restore the Na+-dependent activation of the GIRK1N217D/GIRK2D226N heteromeric channels. Thus, the aspartate 226 in GIRK2 plays a crucial role in Na+-dependent activation of both the GIRK2 homomeric and GIRK1/GIRK2 heteromeric channels. Interestingly, intracellular Na+ slowed the time-course of inhibition by PIP2-specific antibody to a similar extent as the neutralization of the aspartate 226 in GIRK2 did. This suggests that intracellular Na2+ binds to the GIRK2 subunit to neutralize the aspartate 226 and to promote the binding of PIP2 to a nearby region of the C-terminus. This activates the GIRK2 homomeric and GIRK1/GIRK2 heteromeric channels.
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Gibson, W. T. "G-protein signalling pathways and appetite regulation." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599391.
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The objective of the work presented here was to screen genes involved in appetite regulation, with a focus on orexigenic signalling. The following genes were screened: the serotonin receptor 5HT2c, the melanin-concentrating hormone receptors types 1 and 2 (MCHR1 and MCHR2) and the gene for the orexigenic ligand agouti-related peptide (AGRP). Several previously-unknown DNA variants were detected. Of greatest interest were mutations that changed coding amino acids. A Thr419Ala variant in 5HT2c cosegregated with obesity over two generations in a British Caucasian family, and was not detected among 192 controls. Nonconservative variants found in MCHR1 were Tyr181His and Arg248Gln. The latter cosegregated with obesity in the proband’s nuclear family, and neither MCHR1 coding variant was detected in 262 controls. Functional testing of the mutant receptors was done in collaboration with other investigators. No differnces between the signalling properties of the wild type and mutant 5HT2c proteins were found. Constitutive activity of the MCHR1 variant proteins could not be demonstrated with certainty. Population studies among British Caucasians found no association between common MCHR1 variants and obesity phenotypes. However, association studies using the c.123G>A and c.199G>A variants in AGRP revealed and association between body-mass index, total fat mass and the rare alleles. This association was highly significant (p<0.0001), and specific to females. Several novel variants in genes involved in appetite regulation are presented here. Functional consequences for the rare nonconservative variants have yet to be verified. However, a potentially intriguing association exists between common SNPs in the AGRP gene and fat accumulation in women.
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Sun, Xianqiang. "Theoretical Studies of G-Protein-Coupled Receptors." Doctoral thesis, KTH, Teoretisk kemi och biologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166407.
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The family of G-protein-coupled receptors (GPCRs) contains the largest number of drug targets in the human body, with more than a quarter of the clinically used drugs targeting them. Because of the important roles GPCRs play in the human body, the mechanisms of activation of GPCRs or ligands binding to GPCRs have captivated much research interest since the discovery of GPCRs. A number of GPCR crystal structures determined in recent years have provided us with unprecedented opportunities in investigating how GPCRs function through the conformational changes regulated by their ligands. This has motivated me to perform molecular dynamics (MD) simulations in combination with a variety of other modeling methods to study the activation of some GPCRs and their ligand selectivity. This thesis consists of six chapters. In the first chapter, a brief introduction of GPCRs and MD simulation techniques is given. Detailed MD simulation techniques, including pressure controlling methods and temperature coupling approaches, are described in chapter 2. The metadynamics simulation technique, used to enhance conformational sampling, is described in chapter 3. In chapter 4, I outline the inhomogeneous fluid theory used to calculate the thermodynamics properties of interfacial water molecules. Using the methods described in chapters 2-4, I carried out theoretical investigations on some GPCRs with the results summarized in chapter 5. In chapter 6, I provide a summary of the thesis with future work outlined in an outlook.QC 201505020
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Henne, Randal Marlow. "Computational studies of G-protein coupled receptors /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8048.
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Slessareva, Janna Eugenievna. "Molecular mechanisms of G protein-receptor coupling." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2907.
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Thesis (Ph. D.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains vi, 200 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Ma, Hongzheng. "Molecular mechanisms of G protein-receptor coupling." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2978.
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Thesis (Ph. D.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains viii, 264 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Zazzu, Valeria. "The human G protein-coupled receptor GPR30." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16325.
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Im 1997 wurden der Orphan GPR30 aus HUVECs kloniert, die FSS ausgesetzt waren. In dieser Studie konnte gezeigt werden dass die Expression von GPR30 durch die FSS-Behandlung im Vergleich zu unbehandelten HUVEC-Zellen deutlich induziert wurde. Daraufhin wurde in einer Studie von Isensse et al. die zelluläre und gewebsspezifische Expression von GPR30 in GPR30-LacZ Reportergen-Mäusen untersucht. Es konnte eine Expression von GPR30 vorwiegend in den Endothelzellen der kleinen Arterien verschiedenster Gewebetypen nachgewiesen werden. GPR30 war postuliert dass E2 direkt binden kann und dadurch rasche nicht-genomische Signale vermittelt. Im Gegensatz dazu haben verschiedene andere Veröffentlichungen gezeigt dass E2 nicht spezifisch an GPR30 bindet. Trotz der Kontroverse ob es sich bei GPR30 um einen Östrogenrezeptor oder nicht ist bislang nichts über seine Interaktion zu anderen Proteinen und deren Wechselwirkung bekannt. Deswegen war ein Ziel dieser Arbeit, Interaktionspartner von menschlichen GPR30 zu identifizieren und folglich ein humanes vaskuläres in vitro Modell zu etabliren, um die potentiellen Interaktionen von GPR30 sowie die downstream-Effekte der Wechselwirkung zwischen GPR30 und den neuen Interaktionspartner des vaskulären Modells auf Transkriptebene zu evaluieren. Ein Screening einer humanen kardiovaskulären cDNA-Bibliothek mit Hilfe des Y2H-Systems führte zur Identifizierung mehrerer Interaktionspartner für GPR30 darunter PATJ und FUNDC2. Durch anschließende CoIP konnte die Interaktion von GPR30 mit PATJ validiert werden. Des Weiteren konnte in dieser Arbeit die Wirkung von FSS auf die Expression von GPR30 in HUVECs bestätigt und ebenfalls in weiteren anderen Endothelzellen gezeigt werden. Abschließend wurde die Rolle von GPR30 und PATJ bei der Reaktion auf FSS auf transkriptioneller Ebene in HMEC-1-Zellen genomweit untersucht. Interessanterweise war eine Gruppe von Genen aufgrund von FSS in Zellen die GPR30 überexprimierten dereguliert als alleine durch FSS.In 1997, the orphan G protein-coupled receptor 30, GPR30, was cloned using HUVECs exposed to FSS. It was shown that the level of GPR30 expression was up-regulated in response to FSS. Subsequently, in a study performed in the laboratory where the work for this thesis was carried out, the cellular and tissue distribution of GPR30 were investigated in GPR30-LacZ reporter mice and the expression was found predominantly in the endothelial cells of small arteries in several tissue types. GPR30, was also claimed to bind 17-β-estradiol (E2) directly and to mediate rapid non-genomic signalling. In contrast, various reports have indicated that E2 fails to bind GPR30 in a specific manner. Despite the controversy on whether GPR30 is an estrogen receptor or not, nothing is known at present about its relation and interaction with other proteins. Therefore, the aim of the work described in this thesis was to identify human GPR30 protein interaction partners and to establish a human vascular in vitro model in order to evaluate the potential role of GPR30 and the downstream effects of the interaction between GPR30 and new interaction partners in a vascular model at transcript level. The screening of a human heart cDNA library using the yeast two-hybrid assay led to the identification of several interaction partners for GPR30, among them PATJ and FUNDC2. These interactions were verified by CoIP experiments and the interaction of GPR30 with PATJ could be confirmed. The effect of FSS on the expression of GPR30 was confirmed in HUVECs and was detected in other endothelial cell types. In HUAECs, HAoECs and HMEC-1 cells GPR30 was also found up-regulated upon FSS, suggesting that GPR30 may indeed play a key role in vascular physiology. Finally, the role of GPR30 and PATJ in the FSS response was investigated at the genome-wide transcript level in HMEC-1 cells. Interestingly, a different panel of genes was deregulated owing to FSS in cells over-expressing GPR30 compared to FSS alone.
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Rose, Alexander. "The dynamic coupling interface of G-protein coupled receptors." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17215.
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Um mit ihrer Umgebung zu kommunizieren verfügen lebende Zellen über Rezeptoren, welche die umschließende Membran überbrücken. Die vorherrschende G-Protein-gekoppelte Rezeptoren (GPCR) erhalten Informationen von Außerhalb durch Bindung eines Liganden, wodurch der Rezeptor aktiviert wird. Während der Aktivierung bildet sich innerzellulär ein offener Spalt, in den ein G-Protein (Gαβγ, G) mit seinem C-terminalen Ende koppeln kann. Die Bindung an einen GPCR führt in der Gα-Untereinheit vom Gαβγ zu einen GDP/GTP-Austausch, welcher für die weitere Signalübertragung ins Zellinnere notwendig ist. Die Kopplung von Rezeptor und Gαβγ umfasst eine Reihe von dynamischen strukturellen Änderungen, die Geschwindigkeit und Spezifität der Interaktion regeln. Hier haben wir MD-Simulationen (Molekulardynamik) verwendet, um die molekularen Details der GPCR Gαβγ Kopplung vor und während der GPCR-Gαβγ-Komplexbildung bis hin zum GDP/GTP-Austausch zu untersuchen.To communicate with their environment, living cells feature receptors that provide a bridge across the enclosing membrane. The prevalent G protein-coupled receptors (GPCR) receive outside information through the binding of a ligand, which activates the receptor. During activation, an open intracellular crevice forms, to which a G protein (Gαβγ, G) can couple with its Gα C-terminus. Binding to GPCRs triggers GDP/GTP exchange in the Gα subunit of Gαβγ, necessary for further signal transfer within the cell. The coupling between receptor and Gαβγ involves a series of dynamic structural changes that govern speed and specificity of the interaction. Here we used molecular dynamics (MD) simulations to elucidate molecular details of the GPCR Gαβγ coupling process before and during GPCR Gαβγ complex formation up to the GDP/GTP exchange.
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Hill, Claire Louise. "The use of Schizosaccharomyces pombe to investigate reguator of G protein signalling proteins." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487827.
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Barclay, Elaine. "Characterisation of palmitoylation in alpha₂_A adrenoceptor and 5-HT₁_A serotonin receptor-G₀₁α G protein fusion proteins." Thesis, University of Glasgow, 2004. http://theses.gla.ac.uk/4998/.
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Palmitoylation variant GPCR-G protein fusion proteins were created between the porcine u2A-adrenoceptor or the human 5-HT1A-serotonin receptor and the pertussis toxin resistant, Cys35lIle, form of the rat Go1u protein. These palmitoylation-variant fusions were transiently expressed in HEK293T cells prior to analysis of the regulation of palmitoylation and the functional consequences of palmitoylation for both the GPCR and G protein parts of the fusions. When the regulation of palmitoylation was studied for u2A-adrenoceptor-GoluCys35IIle fusion proteins, dynamic palmitoylation and depalmitoylation of both the Cys442residue of the u2A-adrenoceptor and the Cys ' residue of the GoluCys351Ile protein were found to occur. However, only the GOluCys351Ileprotein part of the fusion was found to undergo adrenaline-stimulated regulation of palmitoylation and the effect of adrenaline required G protein activation. Adrenaline regulation proceeded in a concentration-dependent manner correlating with agonist occupancy of the u2A-adrenoceptor. Such agonist effects were found to be, at least in part, due to agonist-stimulation of GOluCys351Ile protein depalmitoylation. The requirements for palmitoylation of the u2A-adrenoceptor and GoluCys351Ile protein elements of the u2A-adrenoceptor-GoluCys35IUe fusion proteins were subsequently assessed for various functional properties. Palmitoylation of neither the U2Aadrenoceptor nor the GoluCys351Ile protein parts of the fusion determined fusion protein expression levels, affinity for the agonist adrenaline, affinity for the antagonist RS- 79948-197, ability to bind or to hydrolyse GTP or their ability to influence the efficiency of RGS 16 protein to accelerate the GTPase reaction. In regulation of palmitoylation studies for 5-HTIA-receptor-GoluCys35IIle fusion proteins, dynamic palmitoylation of the Cys' residue of the GoluCys351Ue protein and the Cys417 residue of the 5-HTIA-receptor was observed as well as a lack of incorporation of palmitate into Cys420 of the 5-HT1A-receptor. Dynamic depalmitoylation was only observed for the Cys' residue of the GoluCys351Ile protein, not for the 5-HT1A-receptor. In the latter case, palmitate once incorporated appeared to remain stably attached. Both the 5-HT1A-receptor and the GoluCys351Ile protein parts of the fusion were found to undergo 8-0H-DPAT-stimulated regulation ofpalmitoylation. 8-0H-DPAT was able to regulate palmitoylation levels of both proteins in a concentration-dependent manner. For the regulation of GoluCys351Ile protein palmitoylation such agonist effects were found likely to be, at least in part, due to an agonist-stimulated rate of depalmitoylation. For the regulation of 5-HT1A-receptor palmitoylation such agonist-stimulated increases in observed palmitoylation levels were only attributable to the addition of palmitate, given that no depalmitoylation of the 5- HT1A-receptor could be detected. The requirements for palmitoylation of the 5-HT1A-receptor and GoluCys351Ile protein elements of the 5-HT1A-receptor-GoluCys351Ile fusion proteins were also assessed for a selection of functional properties. Similar to the results obtained with Go1uCys351Ile protein constrained to the uZA-adrenoceptor, the palmitoylation of the GoluCys351Ile protein did not determine fusion protein expression levels, their affinity for the antagonist WAYI00635, or their ability to bind GTP. Palmitoylation of 5-HT1Areceptor did not alter fusion protein expression levels or their affinity for the antagonist WAYI00635. However, in contrast, it did cause enhanced levels of GTP binding to the 5-HT1A-receptor-GoluCys351Ile fusion proteins. The results of this investigation suggest that there are different requirements for regulation of GPCR and G protein palmitoylation dependent on the GPCR-G protein fusion in question. These requirements may be responsible for the specific functional properties displayed by such fusions. The current study also demonstrates that GPCR-G protein fusion proteins can be successfully used as tools to study both the regulation of palmitoylation and the functional consequences of this modification.
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Sagi, Sarah Ann. "G alpha q- and G alpha 12-mediated signaling pathways activated by G protein-coupled thrombin receptors /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9992384.
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Lo, Kin Ho. "Activation of signal transducer and activator of transcription 3 (STAT3) by G[alpha]16 and G[alpha]14 via a c-Src/JAK-and ERK-dependent mechanism /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?BICH%202004%20LO.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 92-111). Also available in electronic version. Access restricted to campus users.
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Ip, Koon-ching. "Role of G[alpha]-interacting protein (GAIP) in modulation of MAPK pathways /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?BICH%202008%20IP.
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Runne, Caitlin M. "Function and Activation Mechanism of PLEKHG2, A Novel G Beta Gamma-Activated RhoGEF in Leukemia Cells." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4907.
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The Rho family of GTPases plays a crucial role in the regulation of diverse cellular processes, including proliferation and actin cytoskeletal rearrangement to promote cell migration. However, dysregulation of RhoGTPases has been associated with disease, particularly cancers such as leukemia. Despite this, RhoGTPases are rarely mutated in cancer. Rather, dysregulation of their regulatory proteins through mutation or overexpression contributes to disease pathogenesis. RhoGTPases are activated through Rho guanine nucleotide exchange factors (GEFs). Although over eighty RhoGEFs have been identified that activate the 25 RhoGTPases, the pathological role of the majority of these proteins remains unclear. Further, whereas the majority of RhoGEFs are activated through tyrosine phosphorylation, a small subset can be activated through heterotrimeric G proteins, including through GΒ;Γ; subunits. However, the mechanism by which GΒ;Γ; induces RhoGEF activation remains unclear.
PLEKHG2 is a Dbl family RhoGEF that was originally identified as a gene upregulated in a leukemia mouse model, and later shown to be activated by heterotrimeric G protein Β;Γ; subunits. However, its function and activation mechanisms remain elusive. Here we show that, as compared to primary human T cells, the expression of PLEKHG2 is upregulated in leukemia cell lines. Downregulation of PLEKHG2 by siRNAs specifically inhibited GΒ;Γ;-stimulated Rac and Cdc42, but not RhoA activation. Consequently, inhibition of PLEKHG2 blocked actin polymerization, protrusion formation, and leukemia cell migration in response to SDF1alpha;. Additional studies indicate that GΒ;Γ; likely activates PLEKHG2 by binding the N-terminus of PLEKHG2. This interaction results in the release of autoinhibition imposed by the C-terminus within a region encompassing the catalytic DH domain. As a result, overexpressing either the N-terminus of PLEKHG2 that binds GΒ;Γ; or the C-terminus that autoinhibits PLEKHG2 blocked GΒ;Γ;-stimulated Rac and Cdc42 activation and the ability of leukemia cell to form membrane protrusions and to migrate. Together, our results have demonstrated that PLEKHG2 functions as a novel GΒ;Γ; -stimulated RhoGEF that could contribute to chemokine-induced leukemia cell dissemination and leukemia pathogenesis.
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Kumas, Gozde. "Detecting G-protein Coupled Receptor Interactions Using Enhanced Green Fluorescent Protein Reassembly." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614136/index.pdf.
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The largest class of cell surface receptors in mammalian genomes is the superfamily of G protein-coupled receptors (GPCRs) which are activated by a wide range of extracellular responses such as hormones, pheromones, odorants, and neurotransmitters. Drugs which have therapeutic effects on a wide range of diseases are act on GPCRs. In contrast to traditional idea, it is recently getting accepted that G-protein coupled receptors can form homo- and hetero-dimers and this interaction could have important role on maturation, internalization, function or/and pharmacology.
Bimolecular fluorescence complementation technique (BiFC)is an innovative approach based on the reassembly of protein fragments which directly report interactions. In our study we implemented this technique for detecting and visualizing the GPCR interactions in yeast cells. The enhanced green fluorescent protein (EGFP) fractionated into two fragments at genetic level which does not possess fluorescent function. The target proteins which are going to be tested in terms of interaction are modified with the non-functional fragments, to produce the fusion proteins. The interaction between two target proteins, in this study Ste2p receptors which are alpha pheromone receptors from Saccharomyces cerevisiae, enable the fragments to come in a close proximity and reassemble. After reassembly, EGFP regains its fluorescent function which provides a direct read-out for the detection of interaction. Further studies are required to determine subcellular localization of the interaction. Moreover, by using the fusion protein partners constructed in this study, effects of agonist/antagonist binding and post-translational modifications such as glycosylation and phosphorylation can be examined. Apart from all, optimized conditions for BiFC technique will guide for revealing new protein-protein interactions.
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Gaudio, Sabrina. "Functional characterization of the interaction between G protein coupled receptors (GPCR) and regulators of G protein signaling (RGS) in yeast." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97959.
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Regulators of G-protein Signaling (RGSs) are proteins which attenuate G-Protein coupled receptor (GPCR) signaling by acting as GAPs (GTPase activating proteins) for the Galpha subunit of the heterotrimeric G protein. Although RGSs have been clearly shown to bind the Galpha subunit of heterotrimeric G-proteins, recent studies have shown that RGS specificity occurs via receptor association. To examine possible RGS/GPCR interactions, we constructed a somatostatin 5 (SST5) receptor deletion mutant lacking most of its intracellular C-tail. Here we show that the activation of a GPCR-responsive FUS1 -LacZ reporter gene in yeast strains expressing full length WT SST5 receptor as well as the C-terminally truncated mutant were both inhibited by RGSs 1, 2, 5 and 16, suggesting that the C-tail does not play an integral role in RGS function. As an alternative approach to examine possible RGS/GPCR interactions, RGS function was analyzed via halo assay in yeast cells expressing different RGSs as well the C-tail of different GPCRs including mouse LPA 1, LPA4, Cbeta1, 5HT2A, beta 2AR and human SST5 receptors as well as the third intracellular loop of human SST5. The C-tails and the i3-loop were constructed as GFP fusions. Western blot analysis confirmed that the fusions were expressed in yeast. Of all the combinations of GPCR-C-tail-GFP fusions and RGSs expressed in yeast, only LPA4-GFP was able to interfere with RGS2 function. RGS function was also not inhibited by the expression of SST5-i3-GFP. This suggests that there is a high degree of specificity involved in dictating the interaction between RGSs and GPCRs. In a second study, we wanted to further characterize an immunoreactive RGS5 protein band which was detected from western blot analysis of extract from a yeast strain expressing RGS5 and that was double the size of RGS5. To examine the possibility that this band represents an RGS5 dimer, we examined the molecular weight of RGS5 protein in yeast cells expressing an RGS5-GFP fusion. Western blot analysis of yeast extract expressing GFP-tagged RGS5 detected a band at approximately 50 kDa (representing RGS5-GFP) and a second band at 100 kDa. This suggests that RGS5, like GPCRs, are capable of forming dimers.
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Stewart, Adele Marie. "Regulator of G protein signaling 6 (RGS6), a multifarious and pleiotropic modulator of G protein coupled receptor signaling in brain." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/4765.
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Transmembrane signal transduction by ligand-activated G protein-coupled receptors (GPCRs) controls virtually every aspect of mammalian physiology, and this receptor class is the target of 40-50% of currently marketed pharmaceuticals. In addition to the clinical use of direct GPCR agonists and antagonists, it is now believed that GPCR effectors and regulators may also be viable drug targets with improved therapeutic efficacy and specificity. The prototypic role of Regulator of G protein Signaling (RGS) proteins is inhibition of G protein signaling through acceleration of GTP hydrolysis by GΑ, which promotes re-association of GΑ and GΒΓ subunits with the receptor at the cell membrane. In this way, RGS proteins determine the magnitude and duration of the cellular response to GPCR stimulation. Though RGS protein biochemistry has been well elucidated in vitro, the physiological functions of each RGS family member remain largely unexplored.
RGS6 belongs to the R7 subfamily of RGS proteins originally identified in brain. Our acquisition of an RGS6-/- mouse allowed us to survey RGS6 expression in all tissues of the body revealing the greatest expression of RGS6 in brain. Despite robust neural RGS6 expression, little is known regarding functional roles of RGS6 in the brain and spinal cord. In addition, we identified several novel, higher molecular weight RGS6 immunoreactive bands specifically present in the nervous system. The plan of this thesis work was multifaceted. We sought to elucidate novel GPCR signaling cascades modulated by RGS6 in brain while simultaneously characterizing the expression patterns and identity of the novel RGS6 species specifically detected in the nervous system. Considering the large diversity of RGS6 isoforms present in brain, the abundance of potential RGS6 binding partners, and the possibility of discovering new mechanisms involved in RGS6 regulation, elucidation of the novel RGS6 molecular species is of paramount importance.
Utilizing RGS6-/- mice we identified RGS6 as a critical modulator of two GPCRs in brain. First, by inhibiting the serotonin receptor 1A (5-HT1AR)-adenylyl cyclase (AC) axis, RGS6 functions to promote anxiety- and depression-related behaviors in mice. As a result, RGS6-/- mice exhibit a robust anxiolytic and antidepressant phenotype remarkably similar to that of animals treated chronically with therapeutic doses of selective serotonin reuptake inhibitors (SSRIs). RGS6 also inhibits GABAB receptor (GABABR)-G protein- activated inwardly rectifying potassium (GIRK) channel current in cerebellar granule cells, and loss of RGS6 results in cerebellar ataxia and gait abnormalities reversible by GABABR blockade. Furthermore, evaluation of voluntary alcohol drinking behaviors in WT versus RGS6-/- mice revealed a striking reduction in alcohol intake resulting from RGS6 loss in both acute and chronic alcohol consumption paradigms due, at least in part, to potentiation of GABABR signaling. Thus, RGS6 inhibitors have potential clinical utility in the treatment of mood disorders and alcoholism.
We have shown that one novel RGS6 immunoreactive band expressed in the brain and spinal cord is a phospho-protein sensitive to Λ phosphatase-mediated dephosphorylation. Further, new information acquired from PCR amplification of RGS6 mRNA species from human brain cDNA libraries has necessitated substantial revisions to the RGS6 splicing scheme devised by the Fisher laboratory in 2003. To the 36 isoforms generated from two alternate transcription start sites (RGS6L vs. RGS6), the inclusion or exclusion of exons 14 and 17, and variable splicing to one of 7 different 3' terminal exons, we have added the possible insertion of three novel internal exons (A1, A2, A3), a retained intron, and two new 3' terminal exons. As a result, the number of RGS6 mRNAs present in brain could be as many as 248 unique species, an astonishing diversity unprecedented in the RGS protein family.
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Teichmann, Anke. "Fluoreszenzmikroskopische Untersuchungen zur Interaktion G-Protein gekoppelter Rezeptoren." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16671.
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G-Protein gekoppelte Rezeptoren (GPCR) sind Rezeptoren mit 7 Transmembrandomänen. Nach Bindung ihres Liganden werden über die Kopplung von G-Proteinen rezeptorspezifisch Signaltransduktionswege aktiviert. Ein bislang nicht ausreichend verstandener Prozess für die Funktion von GPCR ist deren Oligomerisierung. Für einige GPCR konnte gezeigt werden, dass die Oligomerisierung den Rezeptortransport und/oder die Dynamik der Rezeptoraktivierung moduliert. Dabei ist noch nicht aufgeklärt, ob die entsprechenden GPCR ausschließlich als Oligomere oder in einem bestimmten Monomer-Dimer Verhältnis (M/D) vorliegen und welcher Dynamik dieses Verhältnis unterliegt. In dieser Arbeit wurde die Homo-Oligomerisierung des Endothelin-B-Rezeptors (ETBR), des Vasopressin-V2-Rezeptors (V2R) und der Corticotropin-Releasing-Factor-Rezeptoren Typ 1 (CRF1R) und Typ 2(a) (CRF2(a)R) analysiert. Im Anschluss an diese Untersuchungen wurde das M/D der GPCR bestimmt. Zur Detektion der Protein-Protein Interaktionen wurden die biophysikalischen Methoden Fluoreszenz-Resonanz-Energie-Transfer (FRET) und Fluoreszenz-Kreuzkorrelations-Spektroskopie (FCCS) eingesetzt. Mit Hilfe der FCCS konnte das spezifische M/D der GPCR bestimmt und über FRET ein Unterschied in der Interaktions-Dynamik zwischen den GPCR der Familie 1 (am Bsp. des V2R) und der Familie 2 (am Bsp. des CRF1R) ermittelt werden. Des Weiteren lieferten die genutzten Methoden den Nachweis, dass der zum CRF1R homologe CRF2(a)R ausschließlich als Monomer vorliegt. Zusätzliche Untersuchungen an Signalpeptidmutanten des CRF1R und des CRF2(a)R weisen darauf hin, dass das Pseudosignalpeptid des CRF2(a)R, welches bislang einzigartig in der Superfamilie der GPCR ist, die Oligomerisierung des Rezeptors verhindert. Zusätzlich zu diesen neuen Daten konnte in dieser Arbeit erstmals ein Zusammenhang zwischen Rezeptorinteraktion und G-Protein Selektivität für den CRF1R und den CRF2(a)R festgestellt werdenThe heptahelical G protein-coupled receptors (GPCRs) are important drug targets. Following activation by their ligands, they exert their function via the binding of G proteins and activation of specific signal transduction cascades. To date, the functional significance of the oligomerization of GPCRs is not completely understood. For some GPCRs it could be shown that the oligomerization modulates receptor transport and/or the dynamics of receptor activation. Most importantly, it is not clear whether the GPCRs exist exclusively as oligomers or in a certain monomer-dimer ratio (M/D) or whether a given ratio is dynamic. In this work, the homo-oligomerization of the endothelin-B-receptor (ETBR), the vasopressin-V2-receptor (V2R) and the corticotropin-releasing-factor-receptors type 1 (CRF1R) and type 2(a) (CRF2(a)R) was analysed. In addition, the M/D of these GPCRs was determined. For the detection of the protein-protein interactions, the following biophysical methods were established: fluorescence-resonance-energy-transfer (FRET) and fluorescence-crosscorrelation-spectroscopy (FCCS). With the help of FCCS, a specific M/D could be determined for each of the GPCRs. Using FRET, differences in the interaction dynamics between family 1 (V2R) and family 2 GPCRs (CRF1R) could be described. Moreover, it was experimentally verified that the CRF2(a)R is exclusively expressed as a monomer, in contrast to the other GPCRs and even the highly homologous CRF1R. Using signal peptide swap experiments, it could be demonstrated that the N-terminal pseudo signal peptide of the CRF2(a)R, which is so far unique in the superfamily of GPCRs, prevents oligomerization of the receptor. In addition, a relation of receptor oligomerization and G protein coupling selectivity was established for the CRF1R and the CRF2(a)R which is novel for the GPCR protein family.
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Zheng, Bin. "RGS proteins : bridging the "GAP"s between G protein signaling and membrane trafficking /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3059905.
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Burger, Katja. "Cholesterin und Progesteron - Modulatoren G-Protein-gekoppelter Signaltransduktionswege." [S.l.] : [s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2001/0031/diss.pdf.
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Schnelzer, Andreas Christof. "Untersuchungen zum kleinen G-Protein Rac1 beim Mammakarzinom." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963997610.
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Ritscher, Lars. "Die Agonistspezifität des G-Protein-gekoppelten Rezeptors GPR34." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-97551.
Full textAbstract:
In der vorliegenden Arbeit wurden die molekularen Grundlagen für die Agonistspezifität des G-Protein-gekoppelten Rezeptors GPR34 untersucht. Mittels verschiedener funktioneller Versuche konnte an ausgewählten Orthologen des Rezeptors gezeigt werden, dass, im Gegensatz zu publizierten Daten, Lysophosphatidylserin (Lyso-PS) nicht der natürliche Agonist des GPR34 ist. Lediglich an einigen cyprinoiden Subtypen des GPR34 hat Lyso-PS surrogat-agonistische Effekte. Anhand eines detaillierten evolutionären Vergleichs von Orthologen konnten Bereiche des Rezeptors ermittelt werden, welche an der Ligandenbindung, und damit an der Agonistspezifität des GPR34 beteiligt sind. Durch Übertragung dieser Bereiche vom Karpfen-GPR34-Subtyp 2a auf den humanen GPR34 konnte dieser zu einem Lyso-PS-sensitiven Rezeptor modelliert werden. Weiterhin wurde Aminoethyl-Carbamoyl-ATP (EDA-ATP) als inverser Agonist an cyprinoiden Orthologen des GPR34 identifiziert. Die Erweiterung des möglichen Ligandenspektrums von Lipiden zu Nukleotidderivaten gibt Hinweise auf die Promiskuität der Bindungsstelle des GPR34. Die Ergebnisse zeigen, dass Lyso-PS nur eine zufällige Aktivität an einigen Orthologen des GPR34 hat. Mit Identifizierung eines Nichtlipides als invers-agonistischen Liganden ist die Suche nach dem natürlichen Liganden des GPR34 noch nicht abgeschlossen und sollte auf weitere chemische Entitäten ausgeweitet werdenLyso-PS (lyso-phosphatidylserine) has been shown to activate the G(i/o)-protein-coupled receptor GPR34. Since in vitro and in vivo studies provided controversial results in assigning lyso-PS as the endogenous agonist for GPR34, we investigated the evolutionary conservation of agonist specificity in more detail. Except for some fish GPR34 subtypes, lyso-PS has no or very weak agonistic activity at most vertebrate GPR34 orthologues investigated. Using chimaeras we identified single positions in the second extracellular loop and the transmembrane helix 5 of carp subtype 2a that, if transferred to the human orthologue, enabled lyso-PS to activate the human GPR34. Significant improvement of agonist efficacy by changing only a few positions strongly argues against the hypothesis that nature optimized GPR34 as the receptor for lyso-PS. Phylogenetic analysis revealed several positions in some fish GPR34 orthologues which are under positive selection. These structural changes may indicate functional specification of these orthologues which can explain the species- and subtype-specific pharmacology of lyso-PS. Furthermore, we identified aminoethyl-carbamoyl ATP as an antagonist of carp GPR34, indicating ligand promiscuity with non-lipid compounds. The results of the present study suggest that lyso-PS has only a random agonistic activity at some GPR34 orthologues and the search for the endogenous agonist should consider additional chemical entities