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Oxford GS, Webb CK. GoLoco motif peptides as probes of Galpha subunit specificity in coupling of G-protein-coupled receptors to ion channels. Methods Enzymol 2005; 390:437-50. [PMID: 15488193 DOI: 10.1016/s0076-6879(04)90027-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Biochemical and structural studies of signaling proteins have revealed critical features of peptide motifs at the interaction surfaces between proteins. Such information can be used to design small peptides that can be used as functional probes of specific interactions in signaling cascades. This article describes the use of a novel domain (the GoLoco motif) found in several members of the regulators of G-protein signaling (RGS) protein family to probe the specificity of Galpha subunit involvement in the coupling of dopamine and somatostatin receptors to ion channels in the AtT20 neuroendocrine cell line. Peptides encoding the GoLoco motifs of RGS12 and AGS3 were perfused into single cells during electrical recording of agonist-induced current responses by whole cell patch clamp methods. The particular sequences chosen have been demonstrated to bind selectively to the GDP-bound form of Galphai, but not Galphao, and preclude association of Gbetagamma and Galphai subunits. A functional manifestation of this property is observed in the progressive uncoupling of D2 dopamine receptors and Kir3.1/3.2 channels with repeated agonist application. Similar uncoupling is not observed with somatostatin receptors nor with D2 receptors coupling to calcium channels, suggesting Galpha subunit specificity in these signaling pathways. Motifs found in other proteins in the GPCR signaling machinery may also prove useful in assessing G-protein signaling specificity and complexity in single cells in the future.
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Affiliation(s)
- Gerry S Oxford
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis 46202, USA
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52
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Fagni L, Ango F, Perroy J, Bockaert J. Identification and functional roles of metabotropic glutamate receptor-interacting proteins. Semin Cell Dev Biol 2004; 15:289-98. [PMID: 15125892 DOI: 10.1016/j.semcdb.2003.12.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In the mammalian brain, a majority of excitatory synapses use glutamate as a neurotransmitter. Glutamate activates ligand-gated channels (ionotropic receptors) and G protein-coupled (metabotropic) receptors. During the past decade, a number of intracellular proteins have been described to interact with these receptors. These proteins not only scaffold the glutamate receptors at the pre- and post-synaptic membranes, but also regulate their subcellular targeting and intracellular signaling. Thus, identification of these proteins has been essential for further understanding the functions of glutamate receptors. Here we will focus on those proteins that interact with the subgroup of metabotropic glutamate (mGlu) receptors, and review the methods used for their identification, as well as their functional roles in neurons.
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Affiliation(s)
- Laurent Fagni
- Laboratory of Functional Genomics, CNRS UPR 2580, CCIPE, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France.
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53
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Kerchner KR, Clay RL, McCleery G, Watson N, McIntire WE, Myung CS, Garrison JC. Differential Sensitivity of Phosphatidylinositol 3-Kinase p110γ to Isoforms of G Protein βγ Dimers. J Biol Chem 2004; 279:44554-62. [PMID: 15322106 DOI: 10.1074/jbc.m406071200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The ability of G protein alpha and betagamma subunits to activate the p110gamma isoform of phosphatidylinositol 3-kinase (PtdIns 3-kinase) was examined using pure, recombinant G proteins and the p101/p110gamma form of PtdIns 3-kinase reconstituted into synthetic lipid vesicles. GTP-activated Gs, Gi, Gq, or Go alpha subunits were unable to activate PtdIns 3-kinase. Dimers containing Gbeta(1-4) complexed with gamma2-stimulated PtdIns 3-kinase activity about 26-fold with EC50 values ranging from 4 to 7 nm. Gbeta5gamma2 was not able to stimulate PtdIns 3-kinase despite producing a 10-fold activation of avian phospholipase Cbeta. A series of dimers with beta subunits containing point mutations in the amino acids that undergo a conformational change upon interaction of betagamma with phosducin (beta1H311Agamma2, beta1R314Agamma2, and beta1W332Agamma2) was tested, and only beta1W332Agamma2 inhibited the ability of the dimer to stimulate PtdIns 3-kinase. Dimers containing the beta1 subunit complexed with a panel of different Ggamma subunits displayed variation in their ability to stimulate PtdIns 3-kinase. The beta1gamma2, beta1gamma10, beta1gamma12, and beta1gamma13 dimers all activated PtdIns 3-kinase about 26-fold with 4-25 nm EC50 values. The beta1gamma11 dimer, which contains the farnesyl isoprenoid group and is highly expressed in tissues containing the p101/p110gamma form of PtdIns 3-kinase, was ineffective. The role of the prenyl group on the gamma subunit in determining the activation of PtdIns 3-kinase was examined using gamma subunits with altered CAAX boxes directing the addition of farnesyl to the gamma2 subunit and geranylgeranyl to the gamma1 and gamma11 subunits. Replacement of the geranylgeranyl group of the gamma2 subunit with farnesyl inhibited the activity of beta1gamma2 on PtdIns 3-kinase. Conversely, replacement of the farnesyl group on the gamma1 and gamma11 subunit with geranylgeranyl restored almost full activity. These findings suggest that all beta subunits, with the exception of beta5, interact equally well with PtdIns 3-kinase. In contrast, the composition of the gamma subunit and its prenyl group markedly affects the ability of the betagamma dimer to stimulate PtdIns 3-kinase.
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Affiliation(s)
- Kristi R Kerchner
- Department of Pharmacology, University of Virginia Health System, Charlottesville, Virginia 22908-0735, USA
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Hynes TR, Mervine SM, Yost EA, Sabo JL, Berlot CH. Live cell imaging of Gs and the beta2-adrenergic receptor demonstrates that both alphas and beta1gamma7 internalize upon stimulation and exhibit similar trafficking patterns that differ from that of the beta2-adrenergic receptor. J Biol Chem 2004; 279:44101-12. [PMID: 15297467 DOI: 10.1074/jbc.m405151200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
To visualize and investigate the regulation of the localization patterns of Gs and an associated receptor during cell signaling, we produced functional fluorescent fusion proteins and imaged them in HEK-293 cells. alphas-CFP, with cyan fluorescent protein (CFP) inserted into an internal loop of alphas, localized to the plasma membrane and exhibited similar receptor-mediated activity to that of alphas. Functional fluorescent beta1gamma7 dimers were produced by fusing an amino-terminal yellow fluorescent protein (YFP) fragment to beta1 (YFP-N-beta1) and a carboxyl-terminal YFP fragment to gamma7 (YFP-C-gamma7). When expressed together, YFP-N-beta1 and YFP-C-gamma7 produced fluorescent signals in the plasma membrane that were not seen when the subunits were expressed separately. Isoproterenol stimulation of cells co-expressing alphas-CFP, YFP-N-beta1/YFP-C-gamma7, and the beta2-adrenergic receptor (beta2AR) resulted in internalization of both fluorescent signals from the plasma membrane. Initially, alphas-CFP and YFP-N-beta1/YFP-C-gamma7 stained the cytoplasm diffusely, and subsequently they co-localized on vesicles that exhibited minimal overlap with beta2AR-labeled vesicles. Moreover, internalization of beta2AR-GFP, but not alphas-CFP or YFP-N-beta1/YFP-C-gamma7, was inhibited by a fluorescent dominant negative dynamin 1 mutant, Dyn1(K44A)-mRFP, indicating that the Gs subunits and beta2AR utilize different internalization mechanisms. Subsequent trafficking of the Gs subunits and beta2AR also differed in that vesicles labeled with the Gs subunits exhibited less overlap with RhoB-labeled endosomes and greater overlap with Rab11-labeled endosomes. Because Rab11 regulates traffic through recycling endosomes, co-localization of alphas and beta1gamma7 on these endosomes may indicate a means of recycling specific alphasbetagamma combinations to the plasma membrane.
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Affiliation(s)
- Thomas R Hynes
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2623, USA
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Holtmann G, Liebregts T, Siffert W. Molecular basis of functional gastrointestinal disorders. Best Pract Res Clin Gastroenterol 2004; 18:633-40. [PMID: 15324704 DOI: 10.1016/j.bpg.2004.04.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
There are a number of abnormalities of gastrointestinal function, including sensory and motor dysfunction, which are believed to play a role in the manifestation of symptoms in patients with functional gastrointestinal disorders (FGID). In addition, there is a remarkable psychiatric comorbidity. Family and twin studies have provided strong evidence for a clustering of FGID in families and an increased concordance in monozygotic compared to dizygotic twins. This points towards the role of one or more hereditary (genetic) factors. Considering these disorders of function and the psychiatric comorbidity, polymorphisms of adrenergic, opioidergic or serotonergic receptors as well as G-protein beta3 (GNB3) subunit gene polymorphisms (C825T) and polymorphisms of 5-HT transporter genes are suitable causes. In addition, mediators or regulators of mucosal inflammation may trigger events that ultimately result in the manifestation of FGID. Thus, relevant polymorphisms of genes with immunmodulating and/or neuromodulating features (OPRM1, IL-4, IL-4R, TNFalpha) may also play a role in the manifestation of FGIDs.
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Affiliation(s)
- Gerald Holtmann
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Essen, Hufelandstr 55, 45122 Essen, Germany.
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56
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Rebois R, Allen BG, Hébert TE. The targetable G protein proteome: where is the next generation of drug targets? ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1741-8372(04)02429-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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57
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Hynes TR, Tang L, Mervine SM, Sabo JL, Yost EA, Devreotes PN, Berlot CH. Visualization of G protein betagamma dimers using bimolecular fluorescence complementation demonstrates roles for both beta and gamma in subcellular targeting. J Biol Chem 2004; 279:30279-86. [PMID: 15136579 DOI: 10.1074/jbc.m401432200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate the role of subcellular localization in regulating the specificity of G protein betagamma signaling, we have applied the strategy of bimolecular fluorescence complementation (BiFC) to visualize betagamma dimers in vivo. We fused an amino-terminal yellow fluorescent protein fragment to beta and a carboxyl-terminal yellow fluorescent protein fragment to gamma. When expressed together, these two proteins produced a fluorescent signal in human embryonic kidney 293 cells that was not obtained with either subunit alone. Fluorescence was dependent on betagamma assembly in that it was not obtained using beta2 and gamma1, which do not form a functional dimer. In addition to assembly, BiFC betagamma complexes were functional as demonstrated by more specific plasma membrane labeling than was obtained with individually tagged fluorescent beta and gamma subunits and by their abilities to potentiate activation of adenylyl cyclase by alpha(s) in COS-7 cells. To investigate isoform-dependent targeting specificity, the localization patterns of dimers formed by pair-wise combinations of three different beta subunits with three different gamma subunits were compared. BiFC betagamma complexes containing either beta1 or beta2 localized to the plasma membrane, whereas those containing beta5 accumulated in the cytosol or on intracellular membranes. These results indicate that the beta subunit can direct trafficking of the gamma subunit. Taken together with previous observations, these results show that the G protein alpha, beta, and gamma subunits all play roles in targeting each other. This method of specifically visualizing betagamma dimers will have many applications in sorting out roles for particular betagamma complexes in a wide variety of cell types.
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Affiliation(s)
- Thomas R Hynes
- The Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2623, USA
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58
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Abstract
We showed previously that Gbetagamma interacts with Receptor for Activated C Kinase 1 (RACK1), a protein that not only binds activated protein kinase C (PKC) but also serves as an adaptor/scaffold for many signaling pathways. Here we report that RACK1 does not interact with Galpha subunits or heterotrimeric G proteins but binds free Gbetagamma subunits released from activated heterotrimeric G proteins following the activation of their cognate receptors in vivo. The association with Gbetagamma promotes the translocation of RACK1 from the cytosol to the membrane. Moreover, binding of RACK1 to Gbetagamma results in inhibition of Gbetagamma-mediated activation of phospholipase C beta2 and adenylyl cyclase II. However, RACK1 has no effect on other functions of Gbetagamma, such as activation of the mitogen-activated protein kinase signaling pathway or chemotaxis of HEK293 cells via the chemokine receptor CXCR2. Similarly, RACK1 does not affect signal transduction through the Galpha subunits of G(i), G(s), or G(q). Collectively, these findings suggest a role of RACK1 in regulating specific functions of Gbetagamma.
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Affiliation(s)
- Songhai Chen
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, USA.
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59
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Li X, Ikezu T, Hexum TD. Betagamma subunits mediate the NPY enhancement of ATP-stimulated inositol phosphate formation. Peptides 2004; 25:267-74. [PMID: 15063008 DOI: 10.1016/j.peptides.2003.12.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Accepted: 12/22/2003] [Indexed: 10/26/2022]
Abstract
Neuropeptide Y (NPY) enhances ATP-stimulated inositol phosphate (InsP) formation in bovine chromaffin cells through an unknown mechanism. Chromaffin cells were transduced with the carboxyl terminus of beta-adrenergic receptor kinase 1 (betaARK1CT), a Gbetagamma subunits scavenger, using a recombinant adenovirus system. The adenovirus also expresses a green fluorescent protein (GFP) which serves as an index of transduction. Flow cytometry showed that up to 80% of chromaffin cells were transduced by the virus. There was a direct correlation between the betaARK1CT inhibition of the NPY enhancement of ATP-stimulated InsP formation and the percent of cells expressing GFP ( r2=0.9993 ). These results demonstrate that Gbetagamma subunits are required for the NPY enhancement of ATP-stimulated InsP formation in bovine chromaffin cells.
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Affiliation(s)
- Xinying Li
- Department of Pharmacology, 986260 Nebraska Medical Center, University of Nebraska Medical Center, Omaha, NE 68198-6260, USA
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60
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Abstract
Patients with irritable bowel syndrome (IBS) are characterized by a broad spectrum of gastrointestinal (GI) symptoms. These IBS-symptoms and symptoms of other functional GI disorders frequently overlap. Moreover, at least in patients with severe disease manifestations there is a remarkable psychiatric comorbidity. There is a number of abnormalities of GI functions including sensory and motor dysfunction that are believed to play a role for the manifestation of symptoms in patients with these functional gastrointestinal disorders (FGID). Family studies provide strong evidence for a clustering of FGID in families. Furthermore, twin studies clearly demonstrate an increased concordance in monocygotic compared to dicygotic twins. This points towards the role of one or more hereditary factors. Considering sensory and motor function as well as the psychiatric comorbidity, polymorphisms of adrenergic, opioidergic or serotonergic receptors as well as G-protein beta3 (GNB3) subunit gene polymorphism and polymorphisms of 5-HT transporter genes are suitable mechanisms for these abnormalities. Hence acute GI infections with a mucosal inflammation appear to trigger a cascade of events that ultimately results in the manifestation of FGID, it is reasonable to assume that functionally relevant polymorphisms of genes with immunmodulating and/or neuromodulating features (OPRM1, IL-4, IL-4R, TNFalpha) play a role. It has emerged that a number of various factors may contribute to the manifestation of functional GI disorders. The currently symptom based labels for functional GI disorders may be helpful to categorize patients and target therapy. However, various underlying pathophysiologies may cause similar symptom patterns. Thus, it is reasonable to anticipate that IBS will be dissected accordingly and our disease concepts will accept the irritable bowel syndrome as the clinical manifestation of a number of different disorders.
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Affiliation(s)
- Gerald Holtmann
- Department of Gastroenterology, Hepatology and General Internal Medicine, Royal Adelaide Hospital,University of Adelaide, North Terrace, South Australia 5000, Adelaide, Australia.
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61
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Woodard GE, Rosado JA. G-Protein Coupled Receptors and Calcium Signaling in Development. Curr Top Dev Biol 2004; 65:189-210. [PMID: 15642384 DOI: 10.1016/s0070-2153(04)65007-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Affiliation(s)
- Geoffrey E Woodard
- Metabolic Diseases Branch, National Institute of Diabetes Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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62
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Møller LN, Stidsen CE, Hartmann B, Holst JJ. Somatostatin receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2003; 1616:1-84. [PMID: 14507421 DOI: 10.1016/s0005-2736(03)00235-9] [Citation(s) in RCA: 255] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In 1972, Brazeau et al. isolated somatostatin (somatotropin release-inhibiting factor, SRIF), a cyclic polypeptide with two biologically active isoforms (SRIF-14 and SRIF-28). This event prompted the successful quest for SRIF receptors. Then, nearly a quarter of a century later, it was announced that a neuropeptide, to be named cortistatin (CST), had been cloned, bearing strong resemblance to SRIF. Evidence of special CST receptors never emerged, however. CST rather competed with both SRIF isoforms for specific receptor binding. And binding to the known subtypes with affinities in the nanomolar range, it has therefore been acknowledged to be a third endogenous ligand at SRIF receptors. This review goes through mechanisms of signal transduction, pharmacology, and anatomical distribution of SRIF receptors. Structurally, SRIF receptors belong to the superfamily of G protein-coupled (GPC) receptors, sharing the characteristic seven-transmembrane-segment (STMS) topography. Years of intensive research have resulted in cloning of five receptor subtypes (sst(1)-sst(5)), one of which is represented by two splice variants (sst(2A) and sst(2B)). The individual subtypes, functionally coupled to the effectors of signal transduction, are differentially expressed throughout the mammalian organism, with corresponding differences in physiological impact. It is evident that receptor function, from a physiological point of view, cannot simply be reduced to the accumulated operations of individual receptors. Far from being isolated functional units, receptors co-operate. The total receptor apparatus of individual cell types is composed of different-ligand receptors (e.g. SRIF and non-SRIF receptors) and co-expressed receptor subtypes (e.g. sst(2) and sst(5) receptors) in characteristic proportions. In other words, levels of individual receptor subtypes are highly cell-specific and vary with the co-expression of different-ligand receptors. However, the question is how to quantify the relative contributions of individual receptor subtypes to the integration of transduced signals, ultimately the result of collective receptor activity. The generation of knock-out (KO) mice, intended as a means to define the contributions made by individual receptor subtypes, necessarily marks but an approximation. Furthermore, we must now take into account the stunning complexity of receptor co-operation indicated by the observation of receptor homo- and heterodimerisation, let alone oligomerisation. Theoretically, this phenomenon adds a novel series of functional megareceptors/super-receptors, with varied pharmacological profiles, to the catalogue of monomeric receptor subtypes isolated and cloned in the past. SRIF analogues include both peptides and non-peptides, receptor agonists and antagonists. Relatively long half lives, as compared to those of the endogenous ligands, have been paramount from the outset. Motivated by theoretical puzzles or the shortcomings of present-day diagnostics and therapy, investigators have also aimed to produce subtype-selective analogues. Several have become available.
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Affiliation(s)
- Lars Neisig Møller
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
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63
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Tso PH, Wong YH. Molecular basis of opioid dependence: role of signal regulation by G-proteins. Clin Exp Pharmacol Physiol 2003; 30:307-16. [PMID: 12859419 DOI: 10.1046/j.1440-1681.2003.03835.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
1. Morphine and opiate narcotics are potent analgesics that have a high propensity to induce tolerance and physical dependence following their repeated administration. 2. The molecular basis of opiate dependence has not been completely elucidated, although the participation of opioid receptors is a prerequisite. Cellular dependence on opioids is believed to result from the chronic stimulation of opioid-regulated signalling networks. 3. As G-protein-coupled receptors, the opioid receptors must rely on heterotrimeric G-proteins for signal transduction. Recent advances in our understanding of G-protein signalling have unveiled novel signalling molecules and mechanisms, some of which may be intricately involved in the manifestation of opiate dependence. 4. In the present review, we will attempt to trace chronic opioid signals along elaborate G-protein-regulated pathways.
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Affiliation(s)
- Prudence H Tso
- Department of Biochemistry, the Molecular Neuroscience Center and The Biotechnology Research Institute, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
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64
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Abstract
Cells use signalling networks to translate with high fidelity extracellular signals into specific cellular functions. Signalling networks are often composed of multiple signalling pathways that act in concert to regulate a particular cellular function. In the centre of the networks are the receptors that receive and transduce the signals. A versatile family of receptors that detect a remarkable variety of signals are the G protein-coupled receptors (GPCRs). Virtually all cells express several GPCRs that use the same biochemical machinery to transduce their signals. Considering the specificity and fidelity of signal transduction, a central question in cell signalling is how signalling specificity is achieved, in particular among GPCRs that use the same biochemical machinery. Ca(2+) signalling is particularly suitable to address such questions, since [Ca(2+)](i) can be recorded with excellent spatial and temporal resolutions in living cells and tissues and now in living animals. Ca(2+) is a unique second messenger in that both biochemical and biophysical components form the Ca(2+) signalling complex to regulate its concentration. Both components act in concert to generate repetitive [Ca(2+)](i) oscillations that can be either localized or in the form of global, propagating Ca(2+) waves. Most of the key proteins that form Ca(2+) signalling complexes are known and their activities are reasonably well understood on the biochemical and biophysical levels. We review here the information gained from studying Ca(2+) signalling by GPCRs to gain further understanding of the mechanisms used to generate cellular signalling specificity.
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Affiliation(s)
- Kirill Kiselyov
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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65
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Stanfield PR, Nakajima S, Nakajima Y. Constitutively active and G-protein coupled inward rectifier K+ channels: Kir2.0 and Kir3.0. Rev Physiol Biochem Pharmacol 2002; 145:47-179. [PMID: 12224528 DOI: 10.1007/bfb0116431] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Peter R Stanfield
- Molecular Physiology Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
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66
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Zill P, Baghai TC, Zwanzger P, Schüle C, Minov C, Behrens S, Rupprecht R, Möller HJ, Engel R, Bondy B. Association analysis of a polymorphism in the G-protein stimulatory alpha subunit in patients with major depression. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 114:530-2. [PMID: 12116190 DOI: 10.1002/ajmg.10409] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Growing evidence suggests that G-proteins may be involved in pathogenesis and treatment of affective disorders. Several studies have reported altered levels and/or activities of stimulatory G-proteins in depression. The aim of this study was to investigate whether a polymorphism in the stimulatory alpha subunit of G-proteins (T/C point mutation in exon 5; ATT --> ATC at codon 131) is associated with major depression or response to antidepressant treatment. Therefore, we performed a case-control association study with 212 depressive patients and 137 healthy, unrelated controls. There was no evidence for an association between the investigated polymorphism in the G(alpha)(s) gene and major depression, as well as to treatment response. The results of our study are in concordance with recently published findings which do not support the hypothesis that the gene for the stimulatory alpha subunit of G-proteins is a major susceptibility factor in the pathophysiology of major depression.
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Affiliation(s)
- Peter Zill
- Psychiatric Hospital of the Ludwig-Maximilians-University, Munich, Germany.
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67
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Dingus J, McIntire WE, Wilcox MD, Hilderbrandt JD. Purification of G protein isoforms GOA and GOC from bovine brain. Methods Enzymol 2002; 344:176-85. [PMID: 11771382 DOI: 10.1016/s0076-6879(02)44714-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- Jane Dingus
- Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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68
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Berlot CH. A highly effective dominant negative alpha s construct containing mutations that affect distinct functions inhibits multiple Gs-coupled receptor signaling pathways. J Biol Chem 2002; 277:21080-5. [PMID: 11927592 DOI: 10.1074/jbc.m201330200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate the subcellular organization of receptor-G protein signaling pathways, a robust dominant negative alpha(s) mutant containing substitutions that alter distinct functions was produced and tested for its effects on G(s)-coupled receptor activity in HEK-293 cells. Mutations in the alpha3beta5 loop region, which increase receptor affinity, decrease receptor-mediated activation, and impair activation of adenylyl cyclase, were combined with G226A, which increases affinity for betagamma, and A366S, which decreases affinity for GDP. This triple alpha(s) mutant can inhibit signaling to G(s) from the luteinizing hormone receptor by 97% and from the calcitonin receptor by 100%. In addition, this alpha(s) mutant blocks all signaling from the calcitonin receptor to G(q). These results lead to two conclusions about receptor-G protein signaling. First, individual receptors have access to multiple types of G proteins in HEK-293 cell membranes. Second, different G protein alpha subunits can compete with each other for binding to the same receptor. This dominant negative alpha(s) construct will be useful for determining interrelationships among distinct receptor-G protein interactions in a wide variety of cells and tissues.
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Affiliation(s)
- Catherine H Berlot
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520-8026, USA.
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69
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Kim Y, Oh S. Changes of the level of G protein alpha-subunit mRNA by tolerance to and withdrawal from pentobarbital in rats. Neurochem Res 2002; 27:527-33. [PMID: 12199159 DOI: 10.1023/a:1019808905500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Pentobarbital was continuously infused intracerebroventricularly (i.c.v.) at the rate of 300 micrograms/10 microliters/h for 7 days, and withdrawal from pentobarbital was rendered 24 h after the stopping of the infusion. To eliminate the induction of hepatic metabolism by systemic administration of pentobarbital, an i.c.v. infusion model of tolerance to and withdrawal from pentobarbital was used. Little is known about the functional modulation of the G protein alpha-subunits at the molecular level. The effects of continuous infusion of pentobarbital on the modulation of G protein alpha-subunits mRNA were investigated by using in situ hybridization study. In situ hybridization showed that the level of G alpha s mRNA was increased in the septum and brainstem, and the level of G alpha o mRNA was elevated in the cortex during the pentobarbital withdrawal. The level of G alpha i mRNA was significantly elevated in almost all area of brain during the pentobarbital withdrawal. These results suggest that region-specific changes of G protein alpha-subunit mRNA were involved in the withdrawal from pentobarbital, whereas alpha-subunit is not so highly involved in the pentobarbital tolerance.
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Affiliation(s)
- Younghwa Kim
- Department of Anatomy, College of Medicine, Ewha Womans University, Seoul 158-710, Korea
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70
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Serretti A, Lorenzi C, Lilli R, Mandelli L, Pirovano A, Smeraldi E. Pharmacogenetics of lithium prophylaxis in mood disorders: analysis of COMT, MAO-A, and Gbeta3 variants. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 114:370-9. [PMID: 11992559 DOI: 10.1002/ajmg.10357] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We studied the possible association between the prophylactic efficacy of lithium in mood disorders and the following gene variants: catechol-O-methyltransferase (COMT) G158A, monoamine oxydase A (MAO-A) 30-bp repeat, G-protein beta 3-subunit (Gbeta3) C825T. A total of 201 subjects affected by bipolar (n = 160) and major depressive (n = 41) disorder were followed prospectively for an average of 59.8 months and were typed for their gene variants using PCR techniques. COMT, MAO-A, and Gbeta3 variants were not associated with lithium outcome, even when possible stratification effects such as sex, polarity, age at onset, duration of lithium treatment, and previous episodes were included in the model. The pathways influenced by those variants are not therefore involved with long-term lithium outcome in our sample.
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Affiliation(s)
- Alessandro Serretti
- Department of Psychiatry, Vita-Salute University, Fondazione Centro San Raffaele del Monte Tabor, Milan, Italy.
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71
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Hur EM, Kim KT. G protein-coupled receptor signalling and cross-talk: achieving rapidity and specificity. Cell Signal 2002; 14:397-405. [PMID: 11882384 DOI: 10.1016/s0898-6568(01)00258-3] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Activation of a given type of G protein-coupled receptor (GPCR) triggers a limited set of signalling events in a very rapid and specific manner. The classical paradigm of GPCR signalling was rather linear and sequential. Emerging evidence, however, has revealed that this is only a part of the complex signalling mediated by GPCR. Propagation of GPCR signalling involves cross-regulation of many but specific pathways, including cross-talks between different GPCRs as well as with other signalling pathways. Moreover, it is increasingly apparent that GPCRs can activate both heterotrimeric G protein-dependent and G protein-independent signalling pathways. In this review, we discuss how the signallings initiated by GPCRs achieve rapidity as well as specificity, and how the GPCRs can cross-regulate other specific signalling pathways at the same time. New concepts regarding GPCR signalling have been arising to address this issue, which include multiprotein signalling complex and signalling compartment in microdomain concepts that enable close colocalization or even contact among the proteins engaged in the specific signal transduction. The final outcome of a stimulation of GPCR will thus be the sum of its own specific set of intracellular signalling pathways it regulates.
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Affiliation(s)
- Eun Mi Hur
- Department of Life Science, Division of Molecular and Life Sciences, Pohang University of Science and Technology, San 31, Hyoja Dong, 790-784, Pohang, South Korea
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72
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Abstract
This review focuses on the coupling specificity of the Galpha and Gbetagamma subunits of pertussis toxin (PTX)-sensitive G(i/o) proteins that mediate diverse signaling pathways, including regulation of ion channels and other effectors. Several lines of evidence indicate that specific combinations of G protein alpha, beta and gamma subunits are required for different receptors or receptor-effector networks, and that a higher degree of specificity for Galpha and Gbetagamma is observed in intact systems than reported in vitro. The structural determinants of receptor-G protein specificity remain incompletely understood, and involve receptor-G protein interaction domains, and perhaps other scaffolding processes. By identifying G protein specificity for individual receptor signaling pathways, ligands targeted to disrupt individual pathways of a given receptor could be developed.
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Affiliation(s)
- Paul R Albert
- Ottawa Health Research Institute, Neuroscience, University of Ottawa, 451 Smyth Road, K1H-8M5, Ottawa, ON, Canada.
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73
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Berger M, Budhu S, Lu E, Li Y, Loike D, Silverstein SC, Loike JD. Different G
i
‐coupled chemoattractant receptors signal qualitatively different functions in human neutrophils. J Leukoc Biol 2002. [DOI: 10.1189/jlb.71.5.798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Miles Berger
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - Sadna Budhu
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - Emily Lu
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - Yongmei Li
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - Devora Loike
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - Samuel C. Silverstein
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
| | - John D. Loike
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York
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74
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McIntire WE, Myung CS, MacCleery G, Wang Q, Garrison JC. Reconstitution of G protein-coupled receptors with recombinant G protein alpha and beta gamma subunits. Methods Enzymol 2002; 343:372-93. [PMID: 11665579 DOI: 10.1016/s0076-6879(02)43146-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
The methods outlined in this article describe experiments that can probe the first steps in receptor:G protein interaction using defined, recombinant receptors and G proteins. The protocols have the advantages that the receptors are inserted properly in a cell membrane and that the investigator has complete control of the proteins reconstituted with the receptor. Specific mutations in the receptors or G proteins are studied easily and the protocols allow precise examination of the stoichiometry of the receptor:alpha:beta gamma interaction.
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Affiliation(s)
- William E McIntire
- Department of Pharmacology, University of Virginia Health System, Charlottesville, Virginia 22908, USA
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75
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Varadi A, Rutter GA. Dynamic imaging of endoplasmic reticulum Ca2+ concentration in insulin-secreting MIN6 Cells using recombinant targeted cameleons: roles of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)-2 and ryanodine receptors. Diabetes 2002; 51 Suppl 1:S190-201. [PMID: 11815480 DOI: 10.2337/diabetes.51.2007.s190] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The endoplasmic reticulum (ER) plays a pivotal role in the regulation of cytosolic Ca(2+) concentrations ([Ca(2+)](cyt)) and hence in insulin secretion from pancreatic beta-cells. However, the molecular mechanisms involved in both the uptake and release of Ca(2+) from the ER are only partially defined in these cells, and the presence and regulation of ER ryanodine receptors are a matter of particular controversy. To monitor Ca(2+) fluxes across the ER membrane in single live MIN6 beta-cells, we have imaged changes in the ER intralumenal free Ca(2+) concentration ([Ca(2+)](ER)) using ER-targeted cameleons. Resting [Ca(2+)](ER) (approximately 250 micromol/l) was markedly reduced after suppression (by approximately 40%) of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)-2b but not the SERCA3 isoform by microinjection of antisense oligonucleotides, implicating SERCA2b as the principle ER Ca(2+)-ATPase in this cell type. Nutrient secretagogues that elevated [Ca(2+)](cyt) also increased [Ca(2+)](ER), an effect most marked at the cell periphery, whereas inositol 1,4,5-trisphosphate-generating agents caused a marked and homogenous lowering of [Ca(2+)](ER). Demonstrating the likely presence of ryanodine receptors (RyRs), caffeine and 4-chloro-3-ethylphenol both caused an almost complete emptying of ER Ca(2+) and marked increases in [Ca(2+)](cyt). Furthermore, photolysis of caged cyclic ADP ribose increased [Ca(2+)](cyt), and this effect was largely abolished by emptying ER/Golgi stores with thapsigargin. Expression of RyR protein in living MIN6, INS-1, and primary mouse beta-cells was also confirmed by the specific binding of cell-permeate BODIPY TR-X ryanodine. RyR channels are likely to play an important part in the regulation of intracellular free Ca(2+) changes in the beta-cell and thus in the regulation of insulin secretion.
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Affiliation(s)
- Aniko Varadi
- Department of Biochemistry, University of Bristol, Bristol, U.K
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76
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Li Y, Loike JD, Ember JA, Cleary PP, Lu E, Budhu S, Cao L, Silverstein SC. The bacterial peptide N-formyl-Met-Leu-Phe inhibits killing of Staphylococcus epidermidis by human neutrophils in fibrin gels. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:816-24. [PMID: 11777977 DOI: 10.4049/jimmunol.168.2.816] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
To study human neutrophil (polymorphonuclear leukocyte (PMN)) migration and killing of bacteria in an environment similar to that found in inflamed tissues in vivo, we have used fibrin gels. Fibrin gels (1500 microm thick) containing Staphylococcus epidermidis were formed in Boyden-type chemotaxis chambers. PMN migrated < 300 microm into these gels in 6 h and did not kill S. epidermidis when the gels contained heat-inactivated serum, C5-deficient serum, a streptococcal peptidase specific for a fragment of cleaved C5 (C5a), or anti-C5aR IgG. In contrast, in gels containing normal human serum, PMN migrated approximately 1000 microm into the gels in 4 h and into the full thickness of the gels in 6 h, and killed 90% of S. epidermidis in 6 h. fMLP reduced PMN migration into fibrin gels and allowed S. epidermidis to increase by approximately 300% in 4 h, whereas leukotriene B(4) stimulated PMN to migrate the full thickness of the gels and to kill 80% of S. epidermidis in 4 h. We conclude that both complement opsonization and C5a-stimulated chemotaxis are required for PMN bacterial killing in fibrin gels, and that fMLP inhibits PMN bactericidal activity in fibrin gels. The latter finding is surprising and suggests that in the presence of fibrin fMLP promotes bacterial virulence.
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Affiliation(s)
- Yongmei Li
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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77
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Jian X, Clark WA, Kowalak J, Markey SP, Simonds WF, Northup JK. Gbetagamma affinity for bovine rhodopsin is determined by the carboxyl-terminal sequences of the gamma subunit. J Biol Chem 2001; 276:48518-25. [PMID: 11602594 DOI: 10.1074/jbc.m107129200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two native betagamma dimers, beta(1)gamma(1) and beta(1)gamma(2), display very different affinities for receptors. Since these gamma subunits differ in both primary structure and isoprenoid modification, we examined the relative contributions of each to Gbetagamma interaction with receptors. We constructed baculoviruses encoding gamma(1) and gamma(2) subunits with altered CAAX (where A is an aliphatic amino acid) motifs to direct alternate or no prenylation of the gamma chains and a set of gamma(1) and gamma(2) chimeras with the gamma(2) CAAX motif at the carboxyl terminus. All the gamma constructs coexpressed with beta(1) in Sf9 cells yielded beta(1)gamma dimers, which were purified to near homogeneity, and their affinities for receptors and Galpha were quantitatively determined. Whereas alteration of the isoprenoid of gamma(1) from farnesyl to geranylgeranyl and of gamma(2) from geranylgeranyl to farnesyl had no impact on the affinities of beta(1)gamma dimers for Galpha(t), the non-prenylated beta(1)gamma(2) dimer had significantly diminished affinity. Altered prenylation resulted in a <2-fold decrease in affinity of the beta(1)gamma(2) dimer for rhodopsin and a <3-fold change for the beta(1)gamma(1) dimer. In each case with identical isoprenylation, the beta(1)gamma(2) dimer displayed significantly greater affinity for rhodopsin compared with the beta(1)gamma(1) dimer. Furthermore, dimers containing chimeric Ggamma chains with identical geranylgeranyl modification displayed rhodopsin affinities largely determined by the carboxyl-terminal one-third of the protein. These results indicate that isoprenoid modification of the Ggamma subunit is essential for binding to both Galpha and receptors. The isoprenoid type influences the binding affinity for receptors, but not for Galpha. Finally, the primary structure of the Ggamma subunit provides a major contribution to receptor binding of Gbetagamma, with the carboxyl-terminal sequence conferring receptor selectivity.
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Affiliation(s)
- X Jian
- Laboratory of Cellular Biology, NIDCD, National Institutes of Health, Bethesda, Maryland 20892, USA
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78
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Perroy J, Gutierrez GJ, Coulon V, Bockaert J, Pin JP, Fagni L. The C terminus of the metabotropic glutamate receptor subtypes 2 and 7 specifies the receptor signaling pathways. J Biol Chem 2001; 276:45800-5. [PMID: 11584003 DOI: 10.1074/jbc.m106876200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There is accumulating evidence that the specificity of the transduction cascades activated by G protein-coupled receptors cannot solely depend on the nature of the coupled G protein. To identify additional structural determinants, we studied two metabotropic glutamate (mGlu) receptors, the mGlu2 and mGlu7 receptors, that are both coupled to G(o) proteins but are known to affect different effectors in neurons. Thus, the mGlu2 receptor selectively blocks N- and L-type Ca(2+) channels via a protein kinase C-independent pathway, whereas the mGlu7 receptor selectively blocks P/Q-type Ca(2+) channels via a protein kinase C-dependent pathway, and both effects are pertussis toxin-sensitive. We examined the role of the C-terminal domain of these receptors in this coupling. Chimeras were constructed by exchanging the C terminus of these receptors and transfected into neurons. Different chimeric receptors bearing the C terminus of mGlu7 receptor blocked selectively P/Q-type Ca(2+) channels, whereas chimeras bearing the C terminus of mGlu2 receptor selectively blocked N- and L-type Ca(2+) channels. These results show that the C terminus of mGlu2 and mGlu7 receptors is a key structural determinant that allows these receptors to select a specific signaling pathway in neurons.
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Affiliation(s)
- J Perroy
- CNRS, UPR 9023, CCIPE, 34094 Montpellier Cedex 5, France
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79
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Evanko DS, Thiyagarajan MM, Siderovski DP, Wedegaertner PB. Gbeta gamma isoforms selectively rescue plasma membrane localization and palmitoylation of mutant Galphas and Galphaq. J Biol Chem 2001; 276:23945-53. [PMID: 11294873 DOI: 10.1074/jbc.m101154200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutation of Galpha(q) or Galpha(s) N-terminal contact sites for Gbetagamma resulted in alpha subunits that failed to localize at the plasma membrane or undergo palmitoylation when expressed in HEK293 cells. We now show that overexpression of specific betagamma subunits can recover plasma membrane localization and palmitoylation of the betagamma-binding-deficient mutants of alpha(s) or alpha(q). Thus, the betagamma-binding-defective alpha is completely dependent on co-expression of exogenous betagamma for proper membrane localization. In this report, we examined the ability of beta(1-5) in combination with gamma(2) or gamma(3) to promote proper localization and palmitoylation of mutant alpha(s) or alpha(q). Immunofluorescence localization, cellular fractionation, and palmitate labeling revealed distinct subtype-specific differences in betagamma interactions with alpha subunits. These studies demonstrate that 1) alpha and betagamma reciprocally promote the plasma membrane targeting of the other subunit; 2) beta(5), when co-expressed with gamma(2) or gamma(3), fails to localize to the plasma membrane or promote plasma membrane localization of mutant alpha(s) or alpha(q); 3) beta(3) is deficient in promoting plasma membrane localization of mutant alpha(s) and alpha(q), whereas beta(4) is deficient in promoting plasma membrane localization of mutant alpha(q); 4) both palmitoylation and interactions with betagamma are required for plasma membrane localization of alpha.
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Affiliation(s)
- D S Evanko
- Department of Microbiology and Immunology and Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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80
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Hou Y, Chang V, Capper AB, Taussig R, Gautam N. G Protein beta subunit types differentially interact with a muscarinic receptor but not adenylyl cyclase type II or phospholipase C-beta 2/3. J Biol Chem 2001; 276:19982-8. [PMID: 11262394 DOI: 10.1074/jbc.m010424200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In comparison with the alpha subunit of G proteins, the role of the beta subunit in signaling is less well understood. During the regulation of effectors by the betagamma complex, it is known that the beta subunit contacts effectors directly, whereas the role of the beta subunit is undefined in receptor-G protein interaction. Among the five G protein beta subunits known, the beta(4) subunit type is the least studied. We compared the ability of betagamma complexes containing beta(4) and the well characterized beta(1) to stimulate three different effectors: phospholipase C-beta2, phospholipase C-beta3, and adenylyl cyclase type II. beta(4)gamma(2) and beta(1)gamma(2) activated all three of these effectors with equal efficacy. However, nucleotide exchange in a G protein constituting alpha(o)beta(4)gamma(2) was stimulated significantly more by the M2 muscarinic receptor compared with alpha(o)beta(1)gamma(2). Because alpha(o) forms heterotrimers with beta(4)gamma(2) and beta(1)gamma(2) equally well, these results show that the beta subunit type plays a direct role in the receptor activation of a G protein.
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Affiliation(s)
- Y Hou
- Departments of Anesthesiology and Genetics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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81
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McIntire WE, MacCleery G, Garrison JC. The G protein beta subunit is a determinant in the coupling of Gs to the beta 1-adrenergic and A2a adenosine receptors. J Biol Chem 2001; 276:15801-9. [PMID: 11278863 DOI: 10.1074/jbc.m011233200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signaling specificity of five purified G protein betagamma dimers, beta(1)gamma(2), beta(2)gamma(2), beta(3)gamma(2), beta(4)gamma(2), and beta(5)gamma(2), was explored by reconstituting them with G(s) alpha and receptors or effectors in the adenylyl cyclase cascade. The ability of the five betagamma dimers to support receptor-alpha-betagamma interactions was examined using membranes expressing the beta(1)-adrenergic or A2a adenosine receptors. These receptors discriminated among the defined heterotrimers based solely on the beta isoform. The beta(4)gamma(2) dimer demonstrated the highest coupling efficiency to either receptor. The beta(5)gamma(2) dimer coupled poorly to each receptor, with EC(50) values 40-200-fold higher than those observed with beta(4)gamma(2). Strikingly, whereas the EC(50) of the beta(1)gamma(2) dimer at the beta(1)-adrenergic receptor was similar to beta(4)gamma(2), its EC(50) was 20-fold higher at the A2a adenosine receptor. Inhibition of adenylyl cyclase type I (AC1) and stimulation of type II (AC2) by the betagamma dimers were measured. betagamma dimers containing Gbeta(1-4) were able to stimulate AC2 similarly, and beta(5)gamma(2) was much less potent. beta(1)gamma(2), beta(2)gamma(2), and beta(4)gamma(2) inhibited AC1 equally; beta(3)gamma(2) was 10-fold less effective, and beta(5)gamma(2) had no effect. These data argue that the beta isoform in the betagamma dimer can determine the specificity of signaling at both receptors and effectors.
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Affiliation(s)
- W E McIntire
- Department of Pharmacology, University of Virginia Health System, Charlottesville, Virginia 22908, USA
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82
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Vanderbeld B, Kelly GM. New thoughts on the role of the beta-gamma subunit in G-protein signal transduction. Biochem Cell Biol 2001; 78:537-50. [PMID: 11103944 DOI: 10.1139/o00-075] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Heterotrimeric G proteins are involved in numerous biological processes, where they mediate signal transduction from agonist-bound G-protein-coupled receptors to a variety of intracellular effector molecules and ion channels. G proteins consist of two signaling moieties: a GTP-bound alpha subunit and a beta-gamma heterodimer. The beta-gamma dimer, recently credited as a significant modulator of G-protein-mediated cellular responses, is postulated to be a major determinant of signaling fidelity between G-protein-coupled receptors and downstream effectors. In this review we have focused on the role of beta-gamma signaling and have included examples to demonstrate the heterogeneity in the heterodimer composition and its implications in signaling fidelity. We also present an overview of some of the effectors regulated by beta-gamma and draw attention to the fact that, although G proteins and their associated receptors play an instrumental role in development, there is rather limited information on beta-gamma signaling in embryogenesis.
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Affiliation(s)
- B Vanderbeld
- Department of Zoology, University of Western Ontario, London, Canada
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83
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Johansen PW, Lund HW, Gordeladze JO. Specific combinations of G-protein subunits discriminate hormonal signalling in rat pituitary (GH(3)) cells in culture. Cell Signal 2001; 13:251-6. [PMID: 11306242 DOI: 10.1016/s0898-6568(01)00144-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It was previously shown that hormone receptor coupling to voltage-dependent calcium channels in prolactin and growth hormone-producing GH(3) cells was heavily dependent on the specific heterotrimeric combinations of alpha, beta, and gamma subunits of the guanosine triphosphate (GTP)-binding protein family. Consequently, we assessed whether this was also the case for hormonal modulation of the adenylate cyclase (AC) and phospholipase C (PL-C) effector enzymes in GH(3) cells in culture. By employing polyclonal antibodies directed towards C-terminal decapeptides of various alpha subunits in membrane assays, as well as antisense oligonucleotides towards certain beta- and gamma-subunit genes in whole-cell incubations, it was possible to unravel a tentative profile of heterotrimers preferred by some of the seven-transmembrane-stretch receptors in their modulation of AC and PL-C activities. Vasoactive intestinal peptide (VIP) and thyroliberin (TRH) activate membrane-bound AC through alpha(s)beta(2)gamma(2), while somatostatin (SRIH) and dopamine (DA) inhibited the AC through alpha(i2)beta(1)gamma(3). TRH activated membrane-bound PL-C through alpha(q/11)beta(4)gamma(2), while DA inhibition of the PL-C was accomplished via alpha(o)beta(3)gamma(4). Hence, it seems that not only the specificity of alpha subunits determines the coupling between G protein-associated receptors in GH cells, the receptor binding to G proteins also requires certain combinations of beta and gamma subunits.
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Affiliation(s)
- P W Johansen
- Institute of Medical Biochemistry, University of Oslo, Oslo, Norway.
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84
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Abstract
Sixty years after its initial discovery, the octapeptide hormone angiotensin II (AngII) has proved to play numerous physiological roles that reach far beyond its initial description as a hypertensive factor. In spite of the host of target tissues that have been identified, only two major receptor subtypes, AT1 and AT2, are currently fully identified. The specificity of the effects of AngII relies upon numerous and complex intracellular signaling pathways that often mobilize calcium ions from intracellular stores or from the extracellular medium. Various types of calcium channels (store- or voltage-operated channels) endowed with distinct functional properties play a crucial role in these processes. The activity of these channels can be modulated by AngII in a positive and/or negative fashion, depending on the cell type under observation. This chapter reviews the main characteristics of AngII receptor subtypes and of the various calcium channels as well as the involvement of the multiple signal transduction mechanisms triggered by the hormone in the cell-specific modulation of the activity of these channels.
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Affiliation(s)
- M F Rossier
- Department of Internal Medicine, University Hospital, Geneva, Switzerland
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85
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Abstract
Somatostatin, and the recently discovered neuropeptide cortistatin, exert their physiological actions via a family of six G protein-coupled receptors (sst1, sst2A, sst2B, sst3, sst4, sst5). Following the cloning of somatostatin receptors significant advances have been made in our understanding of their molecular, pharmacological and signaling properties although much progress remains to be done to define their physiological role in vivo. In this review, the present knowledge regarding neuroanatomical localization, signal transduction pathways, desensitization and internalization properties of somatostatin receptors is summarized. Evidence that somatostatin receptors can form homo- and heterodimers and can physically interact with members of the SSTRIP/Shank/ProSAP1/CortBP1 family is also discussed.
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Affiliation(s)
- Z Csaba
- Inserm U549, IFR Broca-Sainte Anne, Centre Paul Broca, Paris, France
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86
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Casarosa P, Bakker RA, Verzijl D, Navis M, Timmerman H, Leurs R, Smit MJ. Constitutive signaling of the human cytomegalovirus-encoded chemokine receptor US28. J Biol Chem 2001; 276:1133-7. [PMID: 11050102 DOI: 10.1074/jbc.m008965200] [Citation(s) in RCA: 190] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Previously it was shown that the HHV-8-encoded chemokine receptor ORF74 shows considerable agonist-independent, constitutive activity giving rise to oncogenic transformation (Arvanitakis, L., Geras-Raaka, E., Varma, A., Gershengorn, M. C., and Cesarman, E. (1997) Nature 385, 347-350). In this study we report that a second viral-encoded chemokine receptor, the human cytomegalovirus-encoded US28, also efficiently signals in an agonist-independent manner. Transient expression of US28 in COS-7 cells leads to the constitutive activation of phospholipase C and NF-kappaB signaling via G(q/11) protein-dependent pathways. Whereas phospholipase C activation is mediated via Galpha(q/11) subunits, the activation of NF-kappaB strongly depends on betagamma subunits with a preference for the beta(2)gamma(1) dimer. The CC chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and MCP-1 (monocyte chemotactic protein-1) act as neutral antagonists at US28, whereas the CX(3)C chemokine fractalkine acts as a partial inverse agonist with IC(50) values of 1-5 nm. Our data suggest that a high level of constitutive activity might be a more general characteristic of viral G protein-coupled receptors and that human cytomegalovirus might exploit this G protein-coupled receptor property to modulate the homeostasis of infected cells via the early gene product US28.
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Affiliation(s)
- P Casarosa
- Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
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87
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Cooper CB, Arnot MI, Feng ZP, Jarvis SE, Hamid J, Zamponi GW. Cross-talk between G-protein and protein kinase C modulation of N-type calcium channels is dependent on the G-protein beta subunit isoform. J Biol Chem 2000; 275:40777-81. [PMID: 11053424 DOI: 10.1074/jbc.c000673200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The modulation of N-type calcium current by protein kinases and G-proteins is a factor in the fine tuning of neurotransmitter release. We have previously shown that phosphorylation of threonine 422 in the alpha(1B) calcium channel domain I-II linker region resulted in a dramatic reduction in somatostatin receptor-mediated G-protein inhibition of the channels and that the I-II linker consequently serves as an integration center for cross-talk between protein kinase C (PKC) and G-proteins (Hamid, J., Nelson, D., Spaetgens, R., Dubel, S. J., Snutch, T. P., and Zamponi, G. W. (1999) J. Biol. Chem. 274, 6195-6202). Here we show that opioid receptor-mediated inhibition of N-type channels is affected to a lesser extent compared with that seen with somatostatin receptors, hinting at the possibility that PKC/G-protein cross-talk might be dependent on the G-protein subtype. To address this issue, we have examined the effects of four different types of G-protein beta subunits on both wild type and mutant alpha(1B) calcium channels in which residue 422 has been replaced by glutamate to mimic PKC-dependent phosphorylation and on channels that have been directly phosphorylated by protein kinase C. Our data show that phosphorylation or mutation of residue 422 antagonizes the effect of Gbeta(1) on channel activity, whereas Gbeta(2), Gbeta(3), and Gbeta(4) are not affected. Our data therefore suggest that the observed cross-talk between G-proteins and protein kinase C modulation of N-type channels is a selective feature of the Gbeta(1) subunit.
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Affiliation(s)
- C B Cooper
- Departments of Physiology & Biophysics and Pharmacology & Therapeutics, Neuroscience and Smooth Muscle Research Groups, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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88
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Ivanina T, Blumenstein Y, Shistik E, Barzilai R, Dascal N. Modulation of L-type Ca2+ channels by gbeta gamma and calmodulin via interactions with N and C termini of alpha 1C. J Biol Chem 2000; 275:39846-54. [PMID: 10995757 DOI: 10.1074/jbc.m005881200] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal voltage-dependent Ca(2+) channels of the N (alpha(1B)) and P/Q (alpha(1A)) type are inhibited by neurotransmitters that activate G(i/o) G proteins; a major part of the inhibition is voltage-dependent, relieved by depolarization, and results from a direct binding of Gbetagamma subunit of G proteins to the channel. Since cardiac and neuronal L-type (alpha(1C)) voltage-dependent Ca(2+) channels are not modulated in this way, they are presumed to lack interaction with Gbetagamma. However, here we demonstrate that both Gbetagamma and calmodulin directly bind to cytosolic N and C termini of the alpha(1C) subunit. Coexpression of Gbetagamma reduces the current via the L-type channels. The inhibition depends on the presence of calmodulin, occurs at basal cellular levels of Ca(2+), and is eliminated by EGTA. The N and C termini of alpha(1C) appear to serve as partially independent but interacting inhibitory gates. Deletion of the N terminus or of the distal half of the C terminus eliminates the inhibitory effect of Gbetagamma. Deletion of the N terminus profoundly impairs the Ca(2+)/calmodulin-dependent inactivation. We propose that Gbetagamma and calmodulin regulate the L-type Ca(2+) channel in a concerted manner via a molecular inhibitory scaffold formed by N and C termini of alpha(1C).
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Affiliation(s)
- T Ivanina
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
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89
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Ha JH, Dhanasekaran N, Koh HC, Lee CH. Single amino acid of g(alpha16) (Ala(228)) is responsible for the ability of chemoattractant C5a receptor to induce G(alpha16)-mediated inositol phosphate release. Biochem Biophys Res Commun 2000; 278:426-31. [PMID: 11097853 DOI: 10.1006/bbrc.2000.3817] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous study suggested that the region encompassing residues 220-240 on G(alpha16) is important in coupling with C5a receptor (Lee et al. (1995) Mol. Pharmacol. 47, 218-223). When aligned sequences are compared in the residue 220-240 segment of G(alpha16), there is a block of eight amino acids extending from residue 227 to residue 234 (227-Ile-Ala-Leu-Ile-Tyr-Leu-Ala-Ser-234) in G(alpha16) that is replaced by a heterologous block extending from amino acid residue 224 to residue 231 (224-Thr-Ser-Ile-Met-Phe-Leu-Val-Ala-231) in G(alpha11). In order to identify the specific amino acid residue necessary for coupling to C5a receptor within the extension of eight amino acids in G(alpha16), a series of chimeric G(alpha11)/G(alpha16) cDNA constructs and mutant G(alpha16) cDNAs were expressed. Then the ability of chimeras and mutant proteins to mediate C5a-induced release of inositol phosphate in transfected Cos-7 cells was tested. The results show that single amino acid Ala(228) is responsible for conferring about 40-50% of the activity of G(alpha16) induced by C5a receptor stimulation.
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Affiliation(s)
- J H Ha
- Department of Pharmacology and Institute of Biomedical Sciences, College of Medicine Hanyang University, Seoul, 133-791, Korea
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90
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Robillard L, Ethier N, Lachance M, Hébert TE. Gbetagamma subunit combinations differentially modulate receptor and effector coupling in vivo. Cell Signal 2000; 12:673-82. [PMID: 11080620 DOI: 10.1016/s0898-6568(00)00118-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In vitro, little specificity is seen for modulation of effectors by different combinations of Gbetagamma subunits from heterotrimeric G proteins. Here, we demonstrate that the coupling of specific combinations of Gbetagamma subunits to different receptors leads to a differential ability to modulate effectors in vivo. We have shown that the beta(1)AR and beta(2)AR can activate homomultimers of the human inwardly rectifying potassium channel Kir 3.2 when coexpressed in Xenopus oocytes, and that this requires a functional mammalian Gs heterotrimer. Modulation was independent of cAMP production, suggesting a membrane-delimited mechanism. To analyze further the importance of different Gbetagamma combinations, we have tested the facilitation of Kir 3.2 activation by betaAR mediated by different Gbetagamma subunits. The subunits tested were Gbeta(1,5) and Ggamma(1,2,7,11). These experiments demonstrated significant variation between the ability of the Gbetagamma combinations to activate the channels after receptor stimulation. This was in marked contrast to the situation in vitro where little specificity for binding of a Kir 3.1 C-terminal GST fusion protein by different Gbetagamma combinations was detected. More importantly, neither receptor, although homologous both structurally and functionally, shared the same preference for Gbetagamma subunits. In the presence of beta(1)AR, Gbeta(5)gamma(1) and Gbeta(5)gamma(11) activated Kir 3.2 to the greatest extent, while for the beta(2)AR, Gbeta(1)gamma(7), Gbeta(1)gamma(11,) and Gbeta(5)gamma(2) produced the greatest responses. Interestingly, no preference was seen in the ability of different Gbetagamma subunits to facilitate receptor-stimulated GTPase activity of the Gsalpha. These results suggest that it is not the receptor/G protein alpha subunit interaction or the Gbetagamma/effector interaction that is altered by Gbetagamma, but rather that the ability of the receptor to interact productively with the Gbetagamma subunit directly and/or the G protein/effector complex is dependent on the specific G protein heterotrimer associated with the receptor.
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Affiliation(s)
- L Robillard
- Centre de recherche, Institut de cardiologie de Montréal et Département d'anésthesie-réanimation, Université de Montréal 5000 rue Bélanger est, H1T 1C8, Montréal, PQ, Canada
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91
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Siffert W. G protein beta 3 subunit 825T allele, hypertension, obesity, and diabetic nephropathy. Nephrol Dial Transplant 2000; 15:1298-306. [PMID: 10978382 DOI: 10.1093/ndt/15.9.1298] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The 825T allele of the gene GNB3 which encodes the beta 3 subunit of heterotrimeric G proteins is associated with enhanced signal transduction via G proteins through the generation of a splice variant termed Gbeta3s. It was detected following a classical candidate gene approach using cell lines from patients with enhanced signal transduction and essential hypertension. The high frequency of the 825T allele in 'old' ethnicities, e.g. bushmen and Australian aborigines as well as in black populations, together with its strong association with obesity suggests that the 825T allele is a true 'thrifty genotype'. Development of obesity associated with the 825T allele is strongly influenced by lifestyle, e.g. physical activity, and other exogenous influences like pregnancy. In hypertension the 825T allele is associated with low renin activity and appears to strongly predict the development of left ventricular hypertrophy. In type 2 diabetes the 825T allele was reported to be predispose for end-stage renal disease, whereas this effect has not yet been confirmed for patients with type 1 diabetes.
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Affiliation(s)
- W Siffert
- Institut für Pharmakologie, Universitätsklinikum Essen, Essen, Germany
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92
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Bautista D, Baker D, Wang D, Fischer D, Van Brocklyn J, Spiegel S, Tigyi G, Parrill A. Dynamic modeling of EDG1 receptor structural changes induced by site-directed mutations. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0166-1280(00)00549-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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93
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Raben DM, Baldassare JJ. Phospholipid metabolism and nuclear envelope signaling. ADVANCES IN ENZYME REGULATION 2000; 40:97-123. [PMID: 10828348 DOI: 10.1016/s0065-2571(99)00023-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- D M Raben
- Department of Physiology, The Johns Hopkins University School of Medicine, 735 North Wolfe Street, Baltimore, MD 21205, USA
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94
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Le Mellay V, Lieberherr M. Membrane signaling and progesterone in female and male osteoblasts. II. Direct involvement of G alpha q/11 coupled to PLC-beta 1 and PLC-beta 3. J Cell Biochem 2000; 79:173-81. [PMID: 10967545 DOI: 10.1002/1097-4644(20001101)79:2<173::aid-jcb10>3.0.co;2-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We have shown that progesterone (10 pM-10 nM) and progesterone covalently bound to bovine serum albumin (P-CMO BSA; 100 pM-1 microM) rapidly increased (within 5 s) the cytosolic free Ca(2+) concentration and inositol 1,4,5 trisphosphate (InsP(3)) formation in confluent female and male rat osteoblasts via a pertussis toxin-insensitive G-protein. The activation of G-proteins coupled to effectors such as phospholipase C (PLC) is an early event in the signal transduction pathway leading to InsP(3) formation. We used antibodies against the various PLC isoforms to show that only PLC-beta1 and PLC-beta 3 were involved in the Ca(2+) mobilization and InsP(3) formation induced by both progestins in female and male osteoblasts, whereas PLC-beta 2, PLC-gamma 1, and PLC-gamma 2 were not. We also used antibodies against the subunits of heterotrimeric G-proteins to show that the activation of PLC-beta 1 and PLC-beta 3 by both progestins involved the G alpha q/11 subunit, which was insensitive to pertussis toxin, whereas G alpha i, G alpha s, and G beta gamma subunits were not. The membrane effects were independent of the concentration of nuclear progesterone receptor, because the concentration of nuclear progesterone receptors was lower in male than in female osteoblasts. These data suggest that progesterone and P-CMO BSA, which does not enter the cell, directly activate G-protein leading to the very rapid formation of second messengers without involving the nuclear receptor.
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Affiliation(s)
- V Le Mellay
- The Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
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95
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Mikulits W, Pradet‐Balade B, Habermann B, Beug H, Garcia‐SANZ JA, Müllner EW. Isolation of translationally controlled mRNAs by differential screening. FASEB J 2000. [DOI: 10.1096/fj.99-0852com] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Wolfgang Mikulits
- Institute of Molecular BiologyVienna BiocenterUniversity of ViennaDr. Bohr‐Gasse, A‐1030 ViennaAustria
- Institute of Molecular PathologyVienna BiocenterUniversity of ViennaDr. Bohr‐Gasse, A‐1030 ViennaAustria
| | - Bérengère Pradet‐Balade
- Department of Immunology and OncologyCentro Nacional de Biotecnologia‐CSICCampus de Cantoblanco de la Universidad Autonoma, E‐28049 MadridSpain
| | - Bianca Habermann
- Institute of Molecular PathologyVienna BiocenterUniversity of ViennaDr. Bohr‐Gasse, A‐1030 ViennaAustria
| | - Hartmut Beug
- Institute of Molecular PathologyVienna BiocenterUniversity of ViennaDr. Bohr‐Gasse, A‐1030 ViennaAustria
| | - Jose A. Garcia‐SANZ
- Department of Immunology and OncologyCentro Nacional de Biotecnologia‐CSICCampus de Cantoblanco de la Universidad Autonoma, E‐28049 MadridSpain
| | - Ernst W. Müllner
- Institute of Molecular BiologyVienna BiocenterUniversity of ViennaDr. Bohr‐Gasse, A‐1030 ViennaAustria
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96
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Obrdlik P, Neuhaus G, Merkle T. Plant heterotrimeric G protein beta subunit is associated with membranes via protein interactions involving coiled-coil formation. FEBS Lett 2000; 476:208-12. [PMID: 10913615 DOI: 10.1016/s0014-5793(00)01706-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gbeta subunits from animals are anchored to membranes via Ggamma subunits. No Ggamma has been identified in plants to date. Using differential centrifugation of Arabidopsis and broccoli extracts, Gbeta was highly enriched in the microsomal pellet. Treatment of microsomes with detergents and salts indicates that plant Gbeta is located at the membrane surface and attached to membranes by hydrophobic interactions. Analysis of transgenic plants expressing Gbeta-GFP fusion proteins showed that mutations in the heptad repeat domain of Gbeta severely diminished their membrane association. We propose that plant Gbeta is anchored to membranes by an unknown protein similar to animal Gbeta by Ggamma, via coiled-coil formation.
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Affiliation(s)
- P Obrdlik
- Institut für Biologie II, Zellbiologie, Universität Freiburg, Schänzlestr. 1, D-79104, Freiburg, Germany
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97
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Balcueva EA, Wang Q, Hughes H, Kunsch C, Yu Z, Robishaw JD. Human G protein gamma(11) and gamma(14) subtypes define a new functional subclass. Exp Cell Res 2000; 257:310-9. [PMID: 10837145 DOI: 10.1006/excr.2000.4893] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mammalian gamma subunit family consists of a minimum of 12 members. Analysis of the amino acid sequence conservation suggests that the gamma subunit family can be divided into three distinct subclasses. The division of the gamma subunit family into these classes is based not only on amino acid homology, but also to some extent on functional similarities. In the present study, two new members of the gamma subunit family, the gamma(11) and gamma(14) subunits, are identified and characterized in terms of their expression and function. The gamma(11) and gamma(14) subunits are most closely related to the gamma(1) subunit and share similar biochemical properties, suggesting their inclusion in class I. However, despite their close phylogenetic relationship and similar biochemical properties, the gamma(1), gamma(11), and gamma(14) subunits exhibit very distinct expression patterns, suggesting that class I should be further subdivided and that the signaling functions of each subgroup are distinct. In this regard, the gamma(11) and gamma(14) subunits represent a new subgroup of farnesylated gamma subunits that are expressed outside the retina and have functions other than phototransduction.
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Affiliation(s)
- E A Balcueva
- Henry Hood M.D. Research Program, Pennsylvania State University College of Medicine, Danville, Pennsylvania, 17822, USA
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98
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Maher CE, Selley DE, Childers SR. Relationship of mu opioid receptor binding to activation of G-proteins in specific rat brain regions. Biochem Pharmacol 2000; 59:1395-401. [PMID: 10751548 DOI: 10.1016/s0006-2952(00)00272-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This study investigated the relationship between mu receptor binding and mu agonist activation of G-proteins in the rat brain. To directly compare agonist potencies in receptor binding (K(i) values) and G-protein activation (K(s) values), both agonist-stimulated [(35)S]guanosine-5'-O-(gamma-thio)-triphosphate ([(35)S]GTPgammaS) and [(3)H]naloxone binding assays were conducted under identical conditions, using the full mu agonist [d-Ala(2), N-Me(4), Gly(5)-ol]-enkephalin (DAMGO). DAMGO exhibited biphasic competition of [(3)H]naloxone binding and stimulation of [(35)S]GTPgammaS binding in most regions. Whereas the high-affinity component represented a large percentage (50-80%) of total receptor sites, the high-affinity component of DAMGO-stimulated [(35)S]GTPgammaS binding was much lower, <30% of the total, and in most regions significant stimulation of [(35)S]GTPgammaS binding did not occur until the high-affinity binding sites were completely occupied. Moreover, the low-affinity potencies for DAMGO in receptor binding and G-protein activation were the same across different regions. Receptor-transducer amplification factors were calculated by the ratio of the apparent B(max) of net agonist-stimulated [(35)S]GTPgammaS binding to the B(max) of receptor binding. Amplification factors for the nine regions examined were relatively high and varied significantly across regions, from a ratio of 8 in the thalamus to 38 in the cortex, suggesting that the efficiency of mu opioid receptor coupling to G-proteins varies across brain regions.
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Affiliation(s)
- C E Maher
- Department of Physiology and Pharmacology, Center for the Neurobiological Investigation of Drug Abuse, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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99
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Tso PH, Yung LY, Wong YH. Regulation of adenylyl cyclase, ERK1/2, and CREB by Gz following acute and chronic activation of the delta-opioid receptor. J Neurochem 2000; 74:1685-93. [PMID: 10737627 DOI: 10.1046/j.1471-4159.2000.0741685.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Opioid tolerance and physical dependence in mammals can be rapidly induced by chronic exposure to opioid agonists. Recently, opioid receptors have been shown to interact with the pertussis toxin (PTX)-insensitive Gz (a member of the Gi subfamily), which inhibits adenylyl cyclase and stimulates mitogen-activated protein kinases (MAPKs). Here, we established stable human embryonic kidney 293 cell lines expressing delta-opioid receptors with or without Gz to examine the role of Gz in opioid receptor-regulated signaling systems. Each cell line was acutely or chronically treated with [D-Pen2,D-Pen5]enkephalin (DPDPE), a delta-selective agonist, in the absence or presence of PTX. Subsequently, the activities of adenylyl cyclase, cyclic AMP (cAMP)-dependent response element-binding proteins (CREBs), and MAPKs were measured by determining cAMP accumulation and phosphorylation of CREBs and the extracellular signal-regulated protein kinases (ERKs) 1 and 2. In cells coexpressing Gz, DPDPE inhibited forskolin-stimulated cAMP accumulation in a PTX-insensitive manner, but Gz could not replace Gi to mediate adenylyl cyclase supersensitization upon chronic opioid treatment. DPDPE-induced adenylyl cyclase supersensitization was not associated with an increase in the phosphorylation of CREBs. Both Gi and Gz mediated DPDPE-induced activation of ERK1/2, but these responses were abolished by chronic opioid treatment. Collectively, our results show that although Gz mediated opioid-induced inhibition of adenylyl cyclase and activation of ERK1/2, Gz alone was insufficient to mediate opioid-induced adenylyl cyclase supersensitization.
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Affiliation(s)
- P H Tso
- Department of Biology and Biotechnology Research Institute, Hong Kong University of Science and Technology, China
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100
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Siffert W, Rosskopf D, Erbel R. [Genetic polymorphism of the G-protein beta3 subunit, obesity and essential hypertension]. Herz 2000; 25:26-33. [PMID: 10713907 DOI: 10.1007/bf03044121] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Following a classical candidate gene approach we have detected a C825T polymorphism in the gene GNB3 which encodes the G beta 3 subunit of heterotrimeric G proteins. The 825T allele causes alternative splicing of the gene and the generation of a truncated but functionally active splice variant of G beta 3 which is referred to as G beta 3s. Thus, genotyping for the C825T polymorphism is predictive for the activation of certain G proteins in humans. The 825T allele is significantly associated with an increased risk for hypertension in Caucasians, most likely "low renin hypertension" and it accumulates significantly in individuals with a strong family history of hypertension. Highest frequencies of the 825T allele (up to 80%) are found in old ethnicities, e.g. black Africans, African Americans, bushmen, and Australian aborigines. This suggests that enhanced G protein activation represents a thrifty genotype which might have facilitated survival in our ancestors. Frequencies of the 825T allele are significant lower in Asians (approximately 40 to 50%) and Caucasians (30%). More recent studies show that young 825T allele carriers are predisposed for obesity and this association could be confirmed across different ethnicities including young Germans, as well as Chinese and black African individuals. Thus, genotyping at the GNB3 locus represents an ideal tool for preventive medicine in that individuals at risk for obesity and hypertension can be identified early and counteract their genetic predisposition through changes in lifestyle. In individuals with borderline hypertension genotyping can facilitate the decision for medical treatment as a positive test result confirms an inherited form of hypertension.
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Affiliation(s)
- W Siffert
- Institut für Pharmakologie, Universitätsklinikum Essen.
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