551
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Walworth NC, Goud B, Kabcenell AK, Novick PJ. Mutational analysis of SEC4 suggests a cyclical mechanism for the regulation of vesicular traffic. EMBO J 1989; 8:1685-93. [PMID: 2504585 PMCID: PMC401010 DOI: 10.1002/j.1460-2075.1989.tb03560.x] [Citation(s) in RCA: 225] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mutant alleles of SEC4, an essential gene required for the final stage of secretion in yeast, have been generated by in vitro mutagenesis. Deletion of the two cysteine residues at the C terminus of the protein results in a soluble non-functional protein, indicating that those two residues are required for normal localization of Sec4p to secretory vesicles and the plasma membrane. A mutant allele of SEC4 generated to mimic an activated, transforming allele of H-ras, as predicted, does not bind GTP. The presence of this allele in cells containing wild-type SEC4 causes a secretory defect and the accumulation of secretory vesicles. The results of genetic studies indicate that this allele behaves as a dominant loss of function mutant and as such prevents wild-type protein from functioning properly. We propose a model in which Sec4p cycles between an active and an inactive state in order to mediate the fusion of vesicles to the plasma membrane.
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Affiliation(s)
- N C Walworth
- Department of Cell Biology, Yale University School of Medicine, New Haven CT 06510
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552
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Woon CW, Heasley L, Osawa S, Johnson GL. Mutation of glycine 49 to valine in the alpha subunit of GS results in the constitutive elevation of cyclic AMP synthesis. Biochemistry 1989; 28:4547-51. [PMID: 2548581 DOI: 10.1021/bi00437a006] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The G-protein GS couples hormone-activated receptors with adenylyl cyclase and stimulates increased cyclic AMP synthesis. Transient expression in COS-1 cells of cDNAs coding for the GS alpha-subunit (alpha S) or alpha S cDNAs having single amino acid mutations Gly49----Val or Gly225----Thr elevated cyclic AMP levels, resulting in the activation of cyclic AMP dependent protein kinase. Stable expression in Chinese hamster ovary cells of alpha S Val49 cDNA resulted in a small constitutive elevation of cyclic AMP that was sufficient to persistently activate cyclic AMP dependent protein kinase activity 1.5-2-fold over basal activity. Stable expression of wild-type alpha S or alpha S Thr225 in Chinese hamster ovary cells was less effective in sustaining elevated cyclic AMP synthesis and kinase activation compared to alpha SVal49.
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Affiliation(s)
- C W Woon
- Department of Biochemistry, University of Massachusetts Medical School, Worcester 01655
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553
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Gautam N, Baetscher M, Aebersold R, Simon MI. A G protein gamma subunit shares homology with ras proteins. Science 1989; 244:971-4. [PMID: 2499046 DOI: 10.1126/science.2499046] [Citation(s) in RCA: 137] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Guanine nucleotide binding proteins (G proteins) that transduce signals from cell surface receptors to effector molecules are made up of three subunits, alpha, beta, and gamma. A complementary DNA clone that encodes a 71-amino acid protein was isolated from bovine brain; this protein contains peptide sequences that were derived from the purified gamma subunit of Gi and Go. The primary sequence of this G protein gamma subunit (G gamma) has 55 percent homology to the gamma subunit of transducin (T gamma) and also has homology to functional domains of mammalian ras proteins. The probe for isolating the clone was generated with the use of the polymerase chain reaction (PCR). The extent of divergence between T gamma and G gamma, the isolation of homologous PCR-generated fragments, and the differences between the predicted amino acid sequence of G gamma and that derived from the gamma subunit of Gi and Go indicate that gamma subunits are encoded by a family of genes.
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Affiliation(s)
- N Gautam
- Division of Biology, California Institute of Technology, Pasadena 91125
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554
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Harada H, Ueda H, Wada Y, Katada T, Ui M, Satoh M. Phosphorylation of mu-opioid receptors--a putative mechanism of selective uncoupling of receptor--Gi interaction, measured with low-Km GTPase and nucleotide-sensitive agonist binding. Neurosci Lett 1989; 100:221-6. [PMID: 2548127 DOI: 10.1016/0304-3940(89)90688-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The mu-opioid receptor agonist stimulation of low-Km GTPase in rat striatal membranes was abolished by islet-activating protein (IAP) treatment, and recovered by Gi reconstitution. When the IAP-treated membranes were phosphorylated with a cAMP-dependent protein kinase, there was no such recovery by Gi. The agonist binding was not affected with respect to Kd, Bmax and sensitivity to guanine nucleotides in the phosphorylated membranes. These findings suggest that phosphorylation of mu-opioid receptors dissociates the agonist change in G-protein activity from the guanine nucleotide-sensitive agonist binding.
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Affiliation(s)
- H Harada
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyoto University, Japan
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555
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Ros M, Watkins DC, Rapiejko PJ, Malbon CC. Glucocorticoids modulate mRNA levels for G-protein beta-subunits. Biochem J 1989; 260:271-5. [PMID: 2505749 PMCID: PMC1138656 DOI: 10.1042/bj2600271] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Adrenalectomy decreases, whereas glucocorticoid treatment increases, the steady-state levels of G-protein beta-subunits (G beta) in rat fat-cells. A DNA-excess solution-hybridization assay was established to define the steady-state mRNA levels for G beta [5.8 +/- 0.4 amol/micrograms of RNA (n = 5) in control fat-cells]. G beta mRNA levels decrease by 20% after adrenalectomy; dexamethasone treatment reverses the decline. Dexamethasone treatment itself increases G beta mRNA levels by 50%.
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Affiliation(s)
- M Ros
- Department of Pharmacological Sciences, School of Medicine, State University of New York, Stony Brook 11794-8651
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556
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Rouot B, Carrette J, Lafontan M, Lan Tran P, Fehrentz JA, Bockaert J, Toutant M. The adipocyte Go alpha-immunoreactive polypeptide is different from the alpha subunit of the brain Go protein. Biochem J 1989; 260:307-10. [PMID: 2505750 PMCID: PMC1138665 DOI: 10.1042/bj2600307] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rat adipose tissue possesses two Bordetella pertussis toxin (PTX) substrates and, in the same 39-41 kDa molecular mass range, positive immunoreactivity has also been reported with antibodies against the alpha subunit of Go, the major brain GTP-binding protein (G-protein). In this study, the presence of the brain Go alpha subunit at 39 kDa in adipocytes was reassessed, since direct correspondence between PTX substrates and Go alpha immunoreactivity has not yet been clearly established. On resolutive SDS/polyacrylamide-gel electrophoresis, the PTX substrates of human adipocytes were compared with the three PTX substrates found in brain. No ADP-ribosylated substrate at the level of the 39 kDa brain Go alpha could be detected in adipocyte membranes. Immunoblotting of human adipocyte membranes stained with our anti-Go alpha antibodies confirmed the presence of a positive immunoreactivity in this tissue, but the apparent molecular mass of the immunoreactive polypeptide in adipocytes was higher than that found in nervous tissues. Taken together, these results indicate that the brain Go alpha subunit is not present in adipose tissue. They also suggest the existence of a G-protein in adipocytes which is immunologically related to Go alpha but having a slightly higher molecular mass.
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Affiliation(s)
- B Rouot
- Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Montpellier, France
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557
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Carraway KL, Carraway CA. Membrane-cytoskeleton interactions in animal cells. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 988:147-71. [PMID: 2524216 DOI: 10.1016/0304-4157(89)90017-8] [Citation(s) in RCA: 128] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- K L Carraway
- Department of Anatomy, University of Miami School of Medicine, FL 33101
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558
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Bagnasco M, Nunes J, Lopez M, Cerdan C, Pierres A, Mawas C, Olive D. T cell activation via the CD2 molecule is associated with protein kinase C translocation from the cytosol to the plasma membrane. Eur J Immunol 1989; 19:823-7. [PMID: 2567674 DOI: 10.1002/eji.1830190507] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
T cell activation via the CD2 molecule involves phospholipase C and phosphoinositide hydrolysis. Here we demonstrate that the triggering of subclones of the human T leukemia Jurkat cell line by anti-CD2 as well as anti-CD3 monoclonal antibodies is able to induce activation (i.e. translocation from cytosol to cell membrane) of protein kinase C (PKC), which is dependent on the formation of 1,2-diacylglycerol from inositol 4-5-bisphosphate. The kinetics of PKC translocation parallels the rise in intracellular calcium following both CD2 and CD3 stimulations. These results further demonstrate that CD2 and CD3 activation pathways use similar signal transduction mechanisms.
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Affiliation(s)
- M Bagnasco
- Unité de Cancérologie et Thérapeutique, Expérimentales U. 119, INSERM, Marseille
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559
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Two different G-proteins mediate neuropeptide Y and bradykinin-stimulated phospholipid breakdown in cultured rat sensory neurons. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83236-7] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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560
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Smith MR, Ryu SH, Suh PG, Rhee SG, Kung HF. S-phase induction and transformation of quiescent NIH 3T3 cells by microinjection of phospholipase C. Proc Natl Acad Sci U S A 1989; 86:3659-63. [PMID: 2726744 PMCID: PMC287197 DOI: 10.1073/pnas.86.10.3659] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Two inositol phospholipid-specific phospholipase C (PLC) isozymes (PLC-I and -II) have been purified from bovine brain. When PLC-I or PLC-II was microinjected (100-700 micrograms/ml) into quiescent NIH 3T3 cells, a time- and dose-dependent induction of DNA synthesis occurred, as demonstrated by [3H]thymidine incorporation into nuclear DNA. In addition, approximately to 8 hr after PLC injection, NIH 3T3 fibroblasts appeared spindle-shaped, refractile, and highly vacuolated, displaying a morphology similar to transformed cells. The morphologic transformation was apparent for 26-30 hr after which the injected cells reverted back to a normal phenotype. Microinjected PLC at a high concentration (1 mg/ml) was cytotoxic, dissolving the cytoplasmic membrane and leaving behind cellular ghosts. PLC is a key regulatory enzyme involved in cellular membrane signal transduction. Introduction of exogenous PLC into NIH 3T3 cells by microinjection induced a growth and oncogenic potential, as demonstrated by the ability of microinjected PLC (approximately 10,000 molecules per cell) to override the cellular G0 block, inducing DNA synthesis and morphologic transformation of growth-arrested fibroblast cells.
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Affiliation(s)
- M R Smith
- Biological Carcinogenesis and Development Program, National Cancer Institute-Frederick Cancer Research Facility, MD 21701
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561
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López-López J, González C, Ureña J, López-Barneo J. Low pO2 selectively inhibits K channel activity in chemoreceptor cells of the mammalian carotid body. J Gen Physiol 1989; 93:1001-15. [PMID: 2738574 PMCID: PMC2216240 DOI: 10.1085/jgp.93.5.1001] [Citation(s) in RCA: 168] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The hypothesis that changes in environmental O2 tension (pO2) could affect the ionic conductances of dissociated type I cells of the carotid body was tested. Cells were subjected to whole-cell patch clamp and ionic currents were recorded in a control solution with normal pO2 (pO2 = 150 mmHg) and 3-5 min after exposure to the same solution with a lower pO2. Na and Ca currents were unaffected by lowering pO2 to 10 mmHg, however, in all cells studied (n = 42) exposure to hypoxia produced a reversible reduction of the K current. In 14 cells exposed to a pO2 of 10 mmHg peak K current amplitude decreased to 35 +/- 8% of the control value. The effect of low pO2 was independent of the internal Ca2+ concentration and was observed in the absence of internal exogenous nucleotides. Inhibition of K channel activity by hypoxia is a graded phenomenon and in the range between 70 and 120 mmHg, which includes normal pO2 values in arterial blood, it is directly correlated with pO2 levels. Low pO2 appeared to slow down the activation time course of the K current but deactivation kinetics seemed to be unaltered. Type I cells subjected to current clamp generate large Na- and Ca-dependent action potentials repetitively. Exposure to low pO2 produces a 4-10 mV increase in the action potential amplitude and a faster depolarization rate of pacemaker potentials, which leads to an increase in the firing frequency. Repolarization rate of individual action potentials is, however, unaffected, or slightly increased. The selective inhibition of K channel activity by low pO2 is a phenomenon without precedents in the literature that explains the chemoreceptive properties of type I cells. The nature of the interaction of molecular O2 with the K channel protein is unknown, however, it is argued that a hemoglobin-like O2 sensor, perhaps coupled to a G protein, could be involved.
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Affiliation(s)
- J López-López
- Departamento de Fisiologia y Biofisica, Facultad de Medicina, Universidad de Sevilla, Spain
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562
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Brüne B, Lapetina EG. Activation of a Cytosolic ADP-ribosyltransferase by Nitric Oxide-generating Agents. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)81808-7] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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563
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Kumagai A, Pupillo M, Gundersen R, Miake-Lye R, Devreotes PN, Firtel RA. Regulation and function of G alpha protein subunits in Dictyostelium. Cell 1989; 57:265-75. [PMID: 2539262 DOI: 10.1016/0092-8674(89)90964-1] [Citation(s) in RCA: 200] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have examined the developmental regulation and function of two G alpha protein subunits, G alpha 1 and G alpha 2, from Dictyostelium. G alpha 1 is expressed in vegetative cells through aggregate stages while G alpha 2 is inducible by cAMP pulses and preferentially expressed in aggregation. Our results suggest that G alpha 2 encodes the G alpha protein subunit associated with the cAMP receptor and mediates all known receptor-activated intracellular signal transduction processes, including chemotaxis and gene regulation. G alpha 1 appears to function in both the cell cycle and development. Overexpression of G alpha 1 results in large, multinucleated cells that develop abnormally. The central role that these G alpha proteins play in signal transduction processes and in controlling Dictyostelium development is discussed.
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Affiliation(s)
- A Kumagai
- Department of Biology, University of California, San Diego, La Jolla 92093
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564
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Spiegel S. Possible Involvement of a GTP-binding Protein in a Late Event During Endogenous Ganglioside-modulated Cellular Proliferation. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83495-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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565
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Poteat HT, Kadison P, McGuire K, Park L, Park RE, Sodroski JG, Haseltine WA. Response of the human T-cell leukemia virus type 1 long terminal repeat to cyclic AMP. J Virol 1989; 63:1604-11. [PMID: 2538645 PMCID: PMC248402 DOI: 10.1128/jvi.63.4.1604-1611.1989] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The sequences that control transcriptional initiation of the provirus of the human T-cell leukemia virus type 1 (HTLV-1) are shown to be responsive to intracellular levels of cyclic AMP. A heptanucleotide sequence present within the 21-nucleotide repeat sequence that is similar to the cyclic AMP-responsive consensus (CRE) sequence was required for cyclic AMP-mediated increase in gene expression. Although the CRE-like sequences were contained within sequences that were responsive to the virally encoded trans-activator (tax), the evidence presented indicates that the mechanisms of promoter induction by the tax product and cyclic AMP are independent. The implication of cyclic AMP stimulation of HTLV-1 provirus gene expression for long-term persistence of infected T cells and for virus-induced transformation is discussed.
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Affiliation(s)
- H T Poteat
- Department of Cancer Biology, Harvard School of Public Health, Boston, Massachusetts
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566
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Crane JK, Hewlett EL, Weikel CS. Failure of pertussis toxin to inhibit activation of guanylate cyclase by the heat-stable enterotoxin of Escherichia coli (STa) in the T84 cell line. Infect Immun 1989; 57:1186-91. [PMID: 2564375 PMCID: PMC313249 DOI: 10.1128/iai.57.4.1186-1191.1989] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The heat-stable enterotoxin (STa) of Escherichia coli causes intestinal secretion by stimulating guanylate cyclase, an enzyme believed to be distinct from the STa receptor. Pertussis toxin (PT) has been reported to block the ability of STa to stimulate guanylate cyclase in rat intestinal mucosa (S. A. Epstein, R. A. Giannella, and H. J. Brandwein, FEBS Lett. 203:44-48, 1986). This suggested that a guanine nucleotide regulatory protein (G protein) coupled the STa receptor to guanylate cyclase, a function not previously recognized for G proteins. We sought to explore this phenomenon and, if possible, to identify this G protein. Initial experiments with the human colon carcinoma cell line T84 revealed that higher-than-expected concentrations (1 micrograms/ml) of PT were needed to intoxicate cells, as assessed by ADP-ribosylation of endogenous PT substrate, but that 99 to 100% intoxication could be achieved. Homogenates made from fully intoxicated cells did not differ from controls in basal or STa-stimulated guanylate cyclase activity, and cyclic GMP accumulation in intact T84 cells was not changed by PT treatment. We conclude that a PT-sensitive G protein is not involved in the stimulation of cyclic GMP production by the enterotoxin STa.
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Affiliation(s)
- J K Crane
- Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville 22908
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567
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Lapadat MA, Spremulli LL. Effect of Guanine Nucleotides on the Conformation and Stability of Chloroplast Elongation Factor Tu. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83574-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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568
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569
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White RE, Hartzell HC. Magnesium ions in cardiac function. Regulator of ion channels and second messengers. Biochem Pharmacol 1989; 38:859-67. [PMID: 2467677 DOI: 10.1016/0006-2952(89)90272-4] [Citation(s) in RCA: 138] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- R E White
- Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
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570
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Holbrook SR, Kim SH. Molecular model of the G protein alpha subunit based on the crystal structure of the HRAS protein. Proc Natl Acad Sci U S A 1989; 86:1751-5. [PMID: 2494654 PMCID: PMC286782 DOI: 10.1073/pnas.86.6.1751] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A structural model of guanine nucleotide-binding regulatory protein alpha subunits (G alpha subunits) is proposed based on the crystal structure of the catalytic domain of the human HRAS protein (p21ras). Because of low overall sequence similarity, structural and functional constraints were used to align the G alpha consensus sequence with that of p21ras. The resulting G alpha model specifies the spatial relationship among the guanine nucleotide-binding site, the binding site of the beta gamma subunit complex, likely regions of effector and receptor interaction, and sites of cholera and pertussis toxin modification. The locations in the model of the experimentally determined sites of proteolytic digestion, point mutation, monoclonal antibody binding, and toxin modification are consistent with and help explain the observed biological activity. Two important findings from our model are (i) the orientation of the G alpha model with respect to the membrane and (ii) the identification of the spatial proximity of the N- and C-terminal regions. Furthermore, by analogy to p21ras, the model assigns specific residues in G alpha required for binding the guanosine (G-box) and phosphates (PO4-box) and identifies residues potentially involved in the conformational switch mechanism (S-box). Specification of these critical regions in the G alpha model suggests guidelines for construction of mutants and chimeric proteins to experimentally test structural and functional hypotheses.
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Affiliation(s)
- S R Holbrook
- Division of Chemical Biodynamics, Lawrence Berkeley Laboratory, University of California, Berkeley 94720
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571
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Negishi M, Ito S, Hayaishi O. Prostaglandin E receptors in bovine adrenal medulla are coupled to adenylate cyclase via Gi and to phosphoinositide metabolism in a pertussis toxin-insensitive manner. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84940-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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572
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Kroll S, Phillips WJ, Cerione RA. The regulation of the cyclic GMP phosphodiesterase by the GDP-bound form of the α subunit of transducin. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83770-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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573
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Janssens PMW, De Jong CCC, Vink AA, Van Haastert PJM. Regulatory properties of magnesium-dependent guanylate cyclase in Dictyostelium discoideum membranes. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83745-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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574
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Ueda H, Yoshihara Y, Misawa H, Fukushima N, Katada T, Ui M, Takagi H, Satoh M. The kyotorphin (Tyrosine-Arginine) Receptor and a Selective Reconstitution with Purified Gi, Measured with GTPase and Phospholipase C Assays. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84911-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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575
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Purification, characterization, and amino-terminal sequence of rat ovarian receptor for luteinizing hormone/human choriogonadotropin. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83790-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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576
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ENGEL WKING. High-dose TRH Treatment of Neuromuscular Diseases: Summary of Mechanisms and Critique of Clinical Studies. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb54511.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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577
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Engel WK. High-dose TRH treatment of neuromuscular diseases: summary of mechanisms and critique of clinical studies. Summary of section IX. Ann N Y Acad Sci 1989; 553:462-72. [PMID: 2497686 DOI: 10.1111/j.1749-6632.1989.tb46665.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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578
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Abstract
The spermatozoon contains cell surface receptors for various egg-associated molecules, one of which has now been identified as the enzyme guanylate cyclase. A single membrane-spanning region divides the enzyme such that about one-half is extracellular and one-half is intracellular. A new paradigm for signal/transduction is established by these observations, in that a hormone or effector molecule binding to an extracellular site activates the catalytic domain of the same protein, resulting in the increased formation of a low molecular weight second messenger. Research on signalling mechanisms in the spermatozoon clearly apply to a diversity of cellular processes as well as to fertilization.
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Affiliation(s)
- D L Garbers
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-0295
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579
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Damonte G, Morelli A, Piu M, Longone P, De Flora A. "In situ" characterization of guanine nucleotide-binding properties of erythrocyte membranes. Biochem Biophys Res Commun 1989; 159:41-7. [PMID: 2647084 DOI: 10.1016/0006-291x(89)92401-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Unsealed membranes from human erythrocytes bind GTP and GTP analogs according to first order kinetics, a single rate constant being observed. With [35S]GTP gamma S this is 0.15 +/- 0.2 min-1. Treatment of the membranes with detergents decreases binding considerably. Scatchard plots reveal uncomplicated patterns of ligand association, with Kd values of 10.2 +/- 2.3 nM [35S]GTP gamma S, of 18.2 +/- 4.3 nM [alpha-32P]GTP and of 28.6 +/- 3.5 nM [alpha-32P]GDP, respectively. The stoichiometry with the three ligands is strictly comparable, i.e. 65 +/- 7 picomoles/mg of membrane protein. Binding of each labeled nucleotide is competitively inhibited by the other two unlabeled ligands, the inhibition constants being very close to the corresponding Kd values. Metabolic depletion and subsequent repletion of intact erythrocytes result in membrane preparations still active in guanine nucleotide binding, with unmodified Kd values. However, the stoichiometry falls to 35 picomoles/mg protein with the "depleted" erythrocyte membranes and regains higher values (50 picomoles/mg protein) with the "repleted" cell membranes. Accordingly, the "in situ" characterization of guanine nucleotide-binding properties of erythrocyte membranes seems to represent a new tool for monitoring the metabolic state of intact erythrocytes.
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Affiliation(s)
- G Damonte
- Institute of Biochemistry, University of Genoa, Italy
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580
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Yokokawa N, Komatsu M, Takeda T, Aizawa T, Yamada T. Mastoparan, a wasp venom, stimulates insulin release by pancreatic islets through pertussis toxin sensitive GTP-binding protein. Biochem Biophys Res Commun 1989; 158:712-6. [PMID: 2493246 DOI: 10.1016/0006-291x(89)92779-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A wasp venom, mastoparan, rapidly stimulated insulin release by rat pancreatic islets in a dose-related manner. The amount of insulin released in response to 58 microM mastoparan far exceeded that induced by 27.8 mM glucose. Mastoparan stimulated insulin release to similar degrees at ambient glucose concentrations of 1.7 mM and 5.6 mM. The islets obtained from pertussis toxin-treated rats showed unequivocally less response to mastoparan. Pretreatment of islets with bromophenacyl bromide, a phospholipase A2 inhibitor, abolished their responsiveness to mastoparan. Pretreatment of islets with nifedipine, a Ca2+ channel blocker, was without effect. Mastoparan is a unique stimulator of insulin release by the pancreatic islets, which acts through GTP-binding protein(s) and phospholipase A2.
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Affiliation(s)
- N Yokokawa
- Department of Gerontology, Endocrinology and Metabolism, School of Medicine, Shinshu University, Nagano-ken, Japan
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581
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Ashkenazi A, Peralta EG, Winslow JW, Ramachandran J, Capon DJ. Functionally distinct G proteins selectively couple different receptors to PI hydrolysis in the same cell. Cell 1989; 56:487-93. [PMID: 2492452 DOI: 10.1016/0092-8674(89)90251-1] [Citation(s) in RCA: 234] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The number of G proteins identified by molecular cloning exceeds the number of known G protein functions. Here we show that a cell can possess multiple G proteins that carry out a similar function, the activation of phospholipase C, but couple selectively to different receptors, which are endogenous to the cell or introduced by DNA transfection. These G proteins (termed Gp) can be distinguished by their sensitivity to pertussis toxin. The assignment of a given Gp pathway to specific receptors is confirmed by the additivity relationships of the PI hydrolysis response mediated by the different receptors. Significantly different amounts of PI hydrolysis are activated through each Gp pathway, suggesting that Gp proteins also differ in their coupling to phospholipase C. These results indicate that distinct Gp pathways in a given cell exist to couple different receptors to PI hydrolysis selectively, and may specify the nature of the cellular response to different receptors by determining the magnitude of PI hydrolysis.
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Affiliation(s)
- A Ashkenazi
- Department of Molecular Biology Genentech, Inc., South San Francisco, California 94080
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582
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Whiteway M, Hougan L, Dignard D, Thomas DY, Bell L, Saari GC, Grant FJ, O'Hara P, MacKay VL. The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein. Cell 1989; 56:467-77. [PMID: 2536595 DOI: 10.1016/0092-8674(89)90249-3] [Citation(s) in RCA: 446] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The STE4 and STE18 genes are required for haploid yeast cell mating. Sequencing of the cloned genes revealed that the STE4 polypeptide shows extensive homology to the beta subunits of mammalian G proteins, while the STE18 polypeptide shows weak similarity to the gamma subunit of transducin. Null mutations in either gene can suppress the haploid-specific cell-cycle arrest caused by mutations in the SCG1 gene (previously shown to encode a protein with similarity to the alpha subunit of G proteins). We propose that the products of the STE4 and STE18 genes comprise the beta and gamma subunits of a G protein complex coupled to the mating pheromone receptors. The genetic data suggest pheromone-receptor binding leads to the dissociation of the alpha subunit from beta gamma (as shown for mammalian G proteins), and the free beta gamma element initiates the pheromone response.
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Affiliation(s)
- M Whiteway
- Genetic Engineering Section NRC Biotechnology Research Institute, Montreal, Quebec, Canada
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583
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Kim D, Lewis DL, Graziadei L, Neer EJ, Bar-Sagi D, Clapham DE. G-protein beta gamma-subunits activate the cardiac muscarinic K+-channel via phospholipase A2. Nature 1989; 337:557-60. [PMID: 2492640 DOI: 10.1038/337557a0] [Citation(s) in RCA: 361] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Muscarinic receptors of cardiac pacemaker and atrial cells are linked to a potassium channel (IK.ACh) by a pertussis toxin-sensitive GTP-binding protein. The dissociation of G-proteins leads to the generation of two potential transducing elements, alpha-GTP and beta gamma. IK.ACh is activated by G-protein alpha- and beta gamma-subunits applied to the intracellular surface of inside-out patches of membrane. beta gamma has been shown to activate the membrane-bound enzyme phospholipase A2 in retinal rods. Arachidonic acid, which is produced from the action of phospholipase A2 on phospholipids, is metabolized to compounds which may act as second messengers regulating ion channels in Aplysia. Muscarinic receptor activation leads to the generation of arachidonic acid in some cell lines. We therefore tested the hypothesis that beta gamma activates IK.ACh by stimulation of phospholipase A2. When patches were first incubated with antibody that blocks phospholipase A2 activity, or with the lipoxygenase inhibitor, nordihydroguaiaretic acid, beta gamma failed to activate IK.ACh. Arachidonic acid and several of its metabolites derived from the 5-lipoxygenase pathway, activated the channel. Blockade of the cyclooxygenase pathway did not inhibit arachidonic acid-induced channel activation. We conclude that the beta gamma-subunit of G-proteins activates IK.ACh by stimulating the production of lipoxygenase-derived second messengers.
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Affiliation(s)
- D Kim
- Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905
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584
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Affiliation(s)
- H R Bourne
- Department of Pharmacology, University of California School of Medicine, San Francisco 94143-0450
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585
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Ewald DA, Pang IH, Sternweis PC, Miller RJ. Differential G protein-mediated coupling of neurotransmitter receptors to Ca2+ channels in rat dorsal root ganglion neurons in vitro. Neuron 1989; 2:1185-93. [PMID: 2560387 DOI: 10.1016/0896-6273(89)90185-2] [Citation(s) in RCA: 153] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The peptides neuropeptide Y (NPY) and bradykinin (BK) both inhibited Ca2+ currents in rat dorsal root ganglion neurons (DRG) in vitro. The effects of both peptides were completely blocked by treatment of cells with pertussis toxin. Based on antigenic determinants, DRG cells contained at least two pertussis toxin substrates, alpha o (Mr, 39 kd) and alpha i2 (Mr, 40 kd). We examined the ability of three purified bovine alpha subunits (identified with antibodies as alpha o, alpha i1, and alpha i2) to reconstitute the inhibitory effects of NPY and BK. Reconstitution of NPY effects occurred according to the potency series alpha o greater than alpha i1 much greater than alpha i2. However, in the case of BK all three G proteins were approximately equally effective. Whereas complete reconstitution of NPY effects could be obtained with alpha o, no single alpha subunit produced complete reconstitution of BK. Combinations of alpha o and alpha i2, however, were able to completely reconstitute the effects of BK. Thus several G proteins can effect the regulation of Ca2+ channels in these cells. However, neurotransmitters may be selective in the G proteins or combinations of G proteins utilized to achieve this regulation.
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Affiliation(s)
- D A Ewald
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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586
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Ott S, Costa T, Herz A. Opioid receptors of neuroblastoma cells are in two domains of the plasma membrane that differ in content of G proteins. J Neurochem 1989; 52:619-26. [PMID: 2536079 DOI: 10.1111/j.1471-4159.1989.tb09164.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Opioid receptors of NG 108-15 cell membranes are distributed in two membrane fractions sedimenting at 20,000 g (P2) and 200,000 g(P3). The number of receptors is identical in P2 and P3, but in P2 all sites are present in one high-affinity state (2 nM), whereas in P3 60% of these receptors display lower affinity (150 nM). Upon addition of GTP or pretreatment with pertussis toxin, 80% of the sites exist in low affinity in both P2 and P3. Therefore, the effect of GTP and pertussis toxin on agonist binding appears to be smaller in P2 than in P3. In contrast, sodium inhibits agonist binding in P2 and P3 to the same extent and with identical potency. Opioid-mediated stimulation of GTPase is much greater in P2 than in P3, whereas inhibition of adenylate cyclase does not differ in the two fractions. Using site-specific antibodies and pertussis toxin-catalyzed ADP-ribosylation, we found that the amount of G proteins in P3 is only 30-50% of that in P2. Treatment of intact cells with the hydrophilic protein-modifying agent sulfosuccinimido-biotin results in biotinylation of proteins from both fractions and in a similar reduction of opioid binding in P2 and P3. Likewise, exposure of intact cells to the alkylating opioid antagonist, chlornaltrexamine, produces identical degrees of receptor inactivation in P2 and P3. The rate of in vivo pertussis toxin-mediated modification of G proteins is not different in the two fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Ott
- Department of Neuropharmacology, Max-Planck-Institut für Psychiatrie, Planegg-Martinsried, F.R.G
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587
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Abstract
Substance P and related tachykinin peptides probably act as neurotransmitters or modulators of neurotransmission, and regulate biological processes as diverse as salivary secretion and transmission of pain signals. Substance P peptide sequences are expressed in three distinct mRNAs that are generated from one gene by differential RNA splicing. In addition to substance P, as many as three other tachykinin peptides can be generated from the polyprotein precursors by differential posttranslational processing. Three tachykinin receptor subtypes have been extensively characterized which differentially interact with the naturally occurring tachykinin peptides. Therefore, the generation of diversity of tachykinin peptides results from differential precursor RNA splicing and differential posttranslational processing. The specificity of peptide responses is the result of selective receptor subtype expression.
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588
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Dunne MJ, Bullett MJ, Li GD, Wollheim CB, Petersen OH. Galanin activates nucleotide-dependent K+ channels in insulin-secreting cells via a pertussis toxin-sensitive G-protein. EMBO J 1989; 8:413-20. [PMID: 2470586 PMCID: PMC400821 DOI: 10.1002/j.1460-2075.1989.tb03392.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The effects of galanin (7-70 nM) on ATP-sensitive K+ channels (KATP channels), membrane potential and the release of insulin have been studied in the insulinoma cell line, RINm5F. Single-channel currents have been recorded from excised outside-out membrane patches as well as intact insulin-secreting cells and it is shown that galanin, added to the outside of the membrane, specifically activates KATP channels. Studies carried out using the fluorescent probe bisoxonol demonstrate that galanin hyperpolarizes RINm5F cells. Galanin was also found to abolish glyceraldehyde-stimulated immunoreactive insulin release from the insulinoma cells. Both the galanin-evoked hyperpolarization and inhibition of insulin release were abolished in cells pre-exposed to pertussis toxin. The possibility that the gating of KATP channels could be mediated by a G-protein was studied in patch-clamp experiments by adding F- to the solution bathing the inside of the cell membranes (open-cell), in order to generate the alumino-fluoride complex AlF4-. F- (1-10 mM) evoked dose-dependent activation of KATP channels and this effect was fully reversible. F- was also able to activate K+ channels inhibited by ATP. That the fluoride activation of KATP channels is mediated by the complex AlF4- was indicated by experiments in which AlCl3 (10 microM) was found to enhance further the activation of K+ channels evoked by 1 mM F- and by results showing that F(-)-stimulation of KATP channels was (i) abolished in the continued presence of F- by the Al3+ chelator deferoxamine (0.5 mM) and (ii) could be mimicked by VO4(3-) which has a structure similar to that of the AlF4- complex.
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Affiliation(s)
- M J Dunne
- Physiological Laboratory, University of Liverpool, UK
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589
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Hathaway DR, March KL. Molecular cardiology: new avenues for the diagnosis and treatment of cardiovascular disease. J Am Coll Cardiol 1989; 13:265-82. [PMID: 2643653 DOI: 10.1016/0735-1097(89)90498-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This review summarizes some of the major advances in the investigation of molecular mechanisms underlying both normal and abnormal cardiovascular function. Four major areas are highlighted including cardiac muscle, the blood vessel, atherosclerosis and thrombosis/thrombolysis. The remarkable strides in understanding multifactorial diseases such as atherosclerosis, and the development of innovative new therapies such as the use of thrombolytic agents produced by recombinant deoxyribonucleic acid (DNA) technology, are noted. Moreover, it is concluded that the past decade of basic research has provided a solid framework for improvements in the diagnosis and therapy of other forms of cardiovascular disease as well. An evaluation of current trends in basic cardiovascular research suggests that diagnostic and therapeutic approaches to disease will increasingly target specific molecular processes underlying the pathophysiologic state.
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Affiliation(s)
- D R Hathaway
- Krannert Institute of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis 46223
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590
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Tischler AS. The dispersed neuroendocrine cells: the structure, function, regulation and effects of xenobiotics on this system. Toxicol Pathol 1989; 17:307-16. [PMID: 2675281 DOI: 10.1177/019262338901700207] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cells which express morphological and functional markers originally described in neurons and neural crest-derived endocrine cells are now known to originate from both ectodermal and endodermal progenitors. These cells are organized to secrete peptides, amines, and other regulatory products in response to neurogenic or chemical stimulation. Individual products may function in endocrine, paracrine, neurotransmitter, or neuromodulatory roles. Multiple products are often produced by individual cells and stored in the same secretory granules. The hormonal profiles of particular types of neuroendocrine cells can, to varying degrees, be changed by environmental signals during development or in adult life. These changes are caused both by transcriptional and post-transcriptional mechanisms. Hormonal profiles are also altered during the development and progression of neoplasia. Signals which stimulate hormone secretion produce a number of ancillary effects, including activation and induction of enzymes which replenish hormone stores, activation of cellular oncogenes, and stimulation of cell proliferation. The effects of environmental signals on neuroendocrine cells are mediated by intracellular transduction pathways which involve cyclic AMP, phosphatidylinositol, calcium, and receptor protein kinase activity. These effects can be potentiated, inhibited, or qualitatively altered by exogenous agents.
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Affiliation(s)
- A S Tischler
- Department of Pathology, Tufts University School of Medicine, Boston, Massachusetts 02111
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591
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Dérijard B, Ben Aïssa M, Lubochinsky B, Cenatiempo Y. Evidence for a membrane-associated GTP-binding protein in Stigmatella aurantiaca, a prokaryotic cell. Biochem Biophys Res Commun 1989; 158:562-8. [PMID: 2492803 DOI: 10.1016/s0006-291x(89)80086-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Signal transducing G proteins are present in all eukaryotic cells, but they have not been found in prokaryotes so far. Myxobacteria, especially Stigmatella aurantiaca, are prokaryotic organisms able to exchange signals. Moreover, they exhibit an active phosphoinositide metabolism, whose intensity is dependent on the physiological state of the cell. Therefore G proteins potentially involved in the activation of phospholipid metabolism or any other event stimulated by external signals were looked for in S. aurantiaca membranes. Using a photoaffinity technique based on cross-linking of radioactive GTP to membrane-associated proteins under UV irradiation, only one major band in the range of 54 kDa was detected. This GTP-binding protein present specifically in membrane preparations binds also GDP, whereas it does not react with other nucleotides, such as ATP, UTP and CTP. The membrane-bound G protein of S. aurantiaca needs further characterization but could be homologous to G alpha subunits found in cytoplasmic membranes of eukaryotes.
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Affiliation(s)
- B Dérijard
- Laboratoires de Biochimie Cellulaire et de Biologie Moléculaire, Université de Poitiers, France
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592
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Fleming N, Sliwinski-Lis E, Burke DN. G regulatory proteins and muscarinic receptor signal transduction in mucous acini of rat submandibular gland. Life Sci 1989; 44:1027-35. [PMID: 2538696 DOI: 10.1016/0024-3205(89)90554-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The involvement of G regulatory proteins in muscarinic receptor signal transduction was examined in electrically permeabilized rat submandibular acinar cells. The guanine nucleotide analog, GTP gamma S, caused the dose dependent hydrolysis of membrane phosphatidylinositol 4,5-bisphosphate to release IP3. This response was insensitive to pertussis toxin treatment and was duplicated by NaF but not by GDP beta S. Enhanced IP3 synthesis was observed with a combination of GTP gamma S and carbachol. Exogenous IP3, as well as carbachol and GTP gamma S, provoked the release of sequestered 45Ca2+ from non-mitochondrial stores. In intact cells, carbachol significantly reduced the level of cyclic AMP induced by the beta-adrenergic agonist, isoproterenol, to 69% of its normal value. Pertussis toxin abolished this inhibitory action of carbachol on cyclic nucleotide levels. These results suggest that muscarinic receptors are coupled to two separate G regulatory proteins in submandibular mucous acini-the pertussis toxin-insensitive Gp of the phosphoinositide transduction pathway associated with elevated cytosolic calcium levels, and the pertussis toxin-sensitive Gi inhibitory protein of the adenylate cyclase complex.
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Affiliation(s)
- N Fleming
- Faculty of Dentistry, Department of Oral Biology, University of Manitoba, Winnipeg, Canada
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593
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Millner PA, Robinson PS. ADP-ribosylation of thylakoid membrane polypeptides by cholera toxin is correlated with inhibition of thylakoid GTPase activity and protein phosphorylation. Cell Signal 1989; 1:421-33. [PMID: 2561911 DOI: 10.1016/0898-6568(89)90028-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Incubation of pea thylakoid membranes with [32P]-NAD+ in the presence of cholera toxin resulted in the [32P]-ADP-ribosylation of a 60 kDa thylakoid membrane polypeptide. When ATP was included in the incubation mixture, a 29 kDa polypeptide was also labelled. In the absence of electron transfer cofactors or inhibitors, the extent of labelling depended on whether the membranes were preincubated in the light or dark and also on the developmental stage of the leaves used for thylakoid isolation. Irrespective of the latter, the strongest labelling was observed when DCMU was present in the light. After pretreatment of the thylakoid membranes with cholera toxin plus NAD+ under the same conditions, light-stimulated GTPase activity and protein phosphorylation were inhibited. The extent of inhibition for both processes appeared to be correlated with the amount of [32P]-ADP-ribosylation found when [32P]-NAD+ was included in the pretreatment mixture. The data presented are fully consistent with the 60 and 29 kDa polypeptides functioning as thylakoid membrane associated guanine nucleotide binding regulatory proteins.
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Affiliation(s)
- P A Millner
- Department of Biochemistry, University of Leeds, U.K
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594
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Ransnäs LA, Insel PA. Quantitation of a guanine nucleotide binding regulatory protein by an enzyme-linked immunosorbent competition assay. Anal Biochem 1989; 176:185-90. [PMID: 2496621 DOI: 10.1016/0003-2697(89)90291-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have developed a new method using a competitive enzyme-linked immunosorbent assay, ELISA, for the determination of levels of the stimulatory guanine nucleotide binding protein, Gs, in membrane extracts. The method is based on the use of antipeptide antibodies generated in rabbits directed against amino acids 28-42 in the alpha-subunit, alpha s, of Gs. The peptide is utilized as the stationary phase in the ELISA and anti-alpha s antibody bound to the microtiter plate is assessed by a peroxidase-coupled anti-rabbit immunoglobulin G antibody that yields detectable color development at 490 nm. Gs purified from rabbit liver is utilized as the standard to assess the ability of Gs present in cholate extracts of membrane samples to compete with bound peptides for primary antibody. This assay provides a direct means to quantify changes in levels of native Gs in membranes and cells.
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Affiliation(s)
- L A Ransnäs
- Department of Pharmacology, University of California, San Diego, La Jolla 92093
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595
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Affiliation(s)
- R M Greene
- Department of Anatomy, Thomas Jefferson University, Philadelphia, Pennsylvania
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596
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Ashcroft FM, Rorsman P. Electrophysiology of the pancreatic beta-cell. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1989; 54:87-143. [PMID: 2484976 DOI: 10.1016/0079-6107(89)90013-8] [Citation(s) in RCA: 772] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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597
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598
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Burnette WN, Whiteley DW, Mar VL, Burns DL, Kaslow HR, Cieplak W, Keith JM, Bartley TD. Developments toward a recombinant pertussis vaccine. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1989; 251:1-7. [PMID: 2692423 DOI: 10.1007/978-1-4757-2046-4_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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599
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Lang J, Schulz R. Chronic opiate receptor activation in vivo alters the level of G-protein subunits in guinea-pig myenteric plexus. Neuroscience 1989; 32:503-10. [PMID: 2555743 DOI: 10.1016/0306-4522(89)90097-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Studies with the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum were undertaken to investigate the relationship between guanine nucleotide-binding proteins (G-proteins) and chronic opioid receptor activation in vivo. Treatment with the narcotic agonist fentanyl, at doses which render the preparation tolerant and dependent, led to an increase of pertussis toxin-catalysed incorporation of ADP-ribose in a protein of approximately 40,000 mol. wt. Quantitative immunoblotting, using site-directed antisera, demonstrated an upregulation of G alpha i/G alpha o and, to an even greater degree, of G beta. However, the level of G alpha s was decreased by the same treatment. All alterations observed were abolished by the concomitant presence of the antagonist naloxone. The implications of this differential regulation of G-protein subunits for opiate-induced tolerance and dependence are discussed.
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Affiliation(s)
- J Lang
- Max-Planck-Institut für Psychiatrie, Abt. Neuropharmacokologie, Martinsried, F.R.G
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600
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Robins RK, Ojo-Amaize E, Parandoosh Z, Cottam HB, Matsumoto SS, Revankar GR, Smee DF, Fujitaki JM, Willis RC, Rubalcava B. Nucleoside and nucleotide modulation of genetic expression--a new approach to chemotherapy. ADVANCES IN ENZYME REGULATION 1989; 29:97-121. [PMID: 2517379 DOI: 10.1016/0065-2571(89)90096-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Unlike conventional enzymes, receptors that activate G proteins do not catalyze the direct formation or cleavage of covalent bonds but act instead as a catalyst for the exchange of GTP vs GDP, which results in major conformational changes in the alpha subunit of G proteins and dissociation and selective binding of the alpha subunit which provokes direct enzyme activation eventually resulting in stimulation of protein kinase A, B or C. Each of these kinases can phosphorylate specific DNA binding proteins which allow new portions of DNA to be read and expressed. Such a series of events can act as switches to control cellular genetic expression resulting in cellular proliferation, differentiation or hormonal secretion of growth factors (Scheme I). Examples of nucleosides and nucleotides which appear to exert their therapeutic effects via G protein control of cellular proliferation resulting in differentiation are tiazofurin, selenazofurin, and 8-chloro-cAMP which have been synthesized and studied in our laboratories. The clinical application of these nucleosides in cancer treatment is presently underway and offers a viable alternative to chemotherapy with highly cytotoxic agents. The use of these derivatives result in down-regulation of the G protein regulatory pathways responsible for rapid cell division. Alternatively, a series of guanosine analogs prepared in our laboratories, 8-bromoguanosine, 8-mercaptoguanosine, 7-methyl-8-oxoguanosine and 7-thia-8-oxoguanosine, all activate various aspects of the immune response by up-regulation of G protein regulatory pathways in various lymphocyte derived cells. Guanosine-like nucleosides which function in this manner could have major clinical application as antitumor, antiviral and antimetastatic agents providing the desired specificity can be achieved. Specific immune enhancement of the aged might be an attainable goal if suitable orally active guanosine derivatives with high specificity can be achieved. The G protein regulatory pathways for modulation of genetic expression in specific cell types provide a major modern approach to new chemotherapeutic agents.
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Affiliation(s)
- R K Robins
- ICN Nucleic Acid Research Institute, Costa Mesa, California 92626
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