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Abstract
Somatostatin (SRIF) induces its multiple biological actions by interacting with a family of receptors, referred to as SSTR1-SSTR5. These receptors are capable of associating with particular guanine nucleotide binding proteins to couple the receptors to distinct cellular effector systems. Therefore, G proteins have an important role in directing SRIF signalling and may provide the molecular basis for the diverse cellular actions of SRIF.
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Affiliation(s)
- S F Law
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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52
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Milligan G. Signal sorting by G-protein-linked receptors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1995; 32:1-29. [PMID: 7748794 DOI: 10.1016/s1054-3589(08)61010-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- G Milligan
- Division of Biochemistry and Molecular Biology, University of Glasgow, Scotland, United Kingdom
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53
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Bucharles C, Vaudry H, Leroux P. Pharmacological characterization of somatostatin receptors in rat cerebellar nuclei. Eur J Pharmacol 1994; 271:79-86. [PMID: 7698215 DOI: 10.1016/0014-2999(94)90267-4] [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: 01/26/2023]
Abstract
Rat cerebellar nuclei contain somatotropin release-inhibiting factor (SRIF) receptors that bind [125I][Leu8,D-Trp22,Tyr25]SRIF-28 but do not bind [125I][Tyr0,D-Trp8]SRIF-14. The aim of the present study was to investigate the pharmacological profile of these receptors by means of binding experiments on tissue sections and quantitative autoradiography. Competition experiments indicated the presence of a single class of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 binding sites in the lateral cerebellar nuclei, showing similar affinities for SRIF-14 and SRIF-28, but low affinity for short-chained analogs. The IC50 values for somatostatin analogs to compete with the binding of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 in the lateral cerebellar nuclei ranked as follows: [Leu8,D-Trp22,Tyr25]SRIF-28 approximately SRIF-14 approximately SRIF-28 < CGP 23996 < D-Phe-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-NH2 (BIM 23052) < SMS 201-995 approximately N-Ahep-(7-10)SRIF-14-Bzl << MK 678 < D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-D-Nal-NH2 (BIM 23056) < D-Phe-c[Cys-Tyr-D-Trp-Lys-Abu-Cys]Nal-NH2 (NC 8-12). Optimum binding of [125I][Leu8,D-Trp22,Tyr25]SRIF-28 did not require divalent cations, and was partly inhibited by guanosine 5' triphosphate. It appears from this study that the rat lateral cerebellar nuclei contain a pure population of receptors exhibiting the same binding characteristics as the recently cloned sstr1 somatostatin receptor. These nuclei could thus provide a useful model in which to investigate the characteristics of native sstr1.
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Affiliation(s)
- C Bucharles
- European Institute for Peptide Research, INSERM U 413, UA CNRS, University of Rouen, Mont-Saint-Aignan, France
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54
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Ward CR, Kopf GS, Storey BT. Solubilization and partial purification from mouse sperm membranes of the specific binding activity for 3-quinuclidinyl benzilate, a potent inhibitor of the zona pellucida-induced acrosome reaction. Mol Reprod Dev 1994; 39:423-32. [PMID: 7893491 DOI: 10.1002/mrd.1080390411] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
3-Quinuclidinyl benzilate (QNB), a potent antagonist of muscarinic acetylcholine receptors, has been demonstrated to inhibit specifically the zona pellucida (ZP)-induced acrosome reaction (AR) in mouse sperm (Florman and Storey, 1982; Dev Biol 91:121-130). In this study we describe the solubilization and partial purification of the mouse sperm QNB binding activity which may represent a component of the putative receptor complex for ZP on the sperm plasma membrane. Sperm membranes were isolated from cell homogenates of washed, capacitated, epididymal mouse sperm. Scatchard plots of QNB binding to these membranes indicated a single class of binding sites with KD = 7.2 nM and Bmax = 8700 sites/cell. These binding characteristics are similar to those seen with QNB binding to whole cells (Florman and Storey, 1982, J Androl 3:157-164). Sperm membranes were solubilized using 1% digitonin/0.2% cholate, and the resultant detergent-soluble fraction possessed QNB binding activity similar to that of intact membranes. The detergent-soluble fraction maintained intact ZP receptor(s)-G protein coupling in that treatment of this fraction with either ZP or mastoparan resulted in a 35% or 65% increase in specific GTP gamma S binding, respectively. The solubilized membrane preparation was fractionated by gel permeation HPLC. A majority of specific QNB binding activity was confined to one HPLC fraction. Analysis of this fraction by SDS-PAGE revealed a complex of approximately 5 proteins unique to this fraction. The most prominent protein had a M(r) of 72 kDa, which is within the M(r) range for muscarinic receptors. A protein with M(r) = 41 kDa was also present within this fraction. Subsequent pertussis toxin (PTX)-catalyzed ADP-ribosylation of this fraction revealed this protein to be the alpha subunit of the G(i) class of G proteins. Although the QNB binding activity could not be positively identified, we propose that it is contained in one or more of the proteins unique to this fraction and that these proteins, including G(i), may act as part of a sperm receptor complex for the ZP.
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Affiliation(s)
- C R Ward
- Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia
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55
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West RE, Myers J, Zweig A, Siegel MI, Egan RW, Clark MA. Steroid-sensitivity of agonist binding to pituitary cell line histamine H3 receptors. Eur J Pharmacol 1994; 267:343-8. [PMID: 8088374 DOI: 10.1016/0922-4106(94)90160-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Histamine H3 receptors have been identified in rat and guinea-pig pituitary glands and in the mouse pituitary tumor cell line, AtT-20. Histamine H3 receptor agonists are reported to stimulate adrenocorticotropic hormone (ACTH) release from AtT-20 cells, an effect blocked by histamine H3 but not H1 or H2 receptor antagonists. To determine whether negative feedback regulation of the histamine H3 receptor-mediated effect might occur, we tested the effects of steroid treatment upon binding of the agonist [3H]N alpha-methylhistamine to AtT-20 cell membranes. Consistent with feedback regulation, steroid treatment of the cells reduced [3H]N alpha-methylhistamine binding. The effect was dose-dependent and was greatest for glucocorticoids among the steroids tested. As the duration of steroid treatment increased, the amount of [3H]N alpha-methylhistamine binding decreased, to 15% of control at 36 h. However, the effect was not specific for histamine H3 receptors. Somatostatin inhibits ACTH release from these cells and its binding was similarly reduced by steroid treatment. Because steroids have been reported to modulate levels of guanine nucleotide-binding proteins, the lack of receptor specificity could reflect an indirect effect of steroids upon agonist binding and, in fact, we show that [3H]N alpha-methylhistamine binding to these cells, like somatostatin, is pertussis toxin-sensitive. However, steroid treatment does not alter the apparent levels of pertussis toxin substrate in these cells. Whether steroid treatment affects histamine H3 receptors of these cells directly or through some more subtle effect upon the guanine nucleotide-binding proteins to which they couple, the result is a negative feedback loop that attenuates [3H]N alpha-methylhistamine binding to these cells.
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Affiliation(s)
- R E West
- Schering-Plough Research Institute, Kenilworth, NJ
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56
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Ward C, Storey B, Kopf G. Selective activation of Gi1 and Gi2 in mouse sperm by the zona pellucida, the egg's extracellular matrix. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36826-6] [Citation(s) in RCA: 23] [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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57
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Liu Y, Jakobs K, Rasenick M, Albert P. G protein specificity in receptor-effector coupling. Analysis of the roles of G0 and Gi2 in GH4C1 pituitary cells. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36729-7] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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58
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Puebla L, Arilla E. Somatostatin receptor-GTP binding regulatory protein-adenylyl cyclase system in hippocampal membranes of strychnine-treated rats. Brain Res 1994; 644:59-66. [PMID: 7913402 DOI: 10.1016/0006-8993(94)90347-6] [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: 01/27/2023]
Abstract
Wistar rats were injected with either a non-convulsive dose (37.5 micrograms/100 g body weight (b.wt.), intravenously (i.v.)) or a convulsive dose (50 or 80 micrograms/100 g b.w.t, i.v.) of strychnine. Binding of 125I-Tyr11-somatostatin (125I-Tyr11-SS) to its specific receptors was measured in hippocampal membranes 15 min after strychnine injection at these three doses. The non-convulsive dose of strychnine did not affect binding of SS in the hippocampus whereas both convulsive doses decreased the number of specific SS receptors without influencing their apparent affinity. Somatostatin-like immunoreactivity (SSLI), SS-modulated adenylyl cyclase (AC) activity and the inhibitory guanine-nucleotide binding regulatory protein were also measured in rats treated with 80 micrograms/100 g b.wt. of strychnine. SSLI content remained stable. No significant differences were seen for the basal and forskolin (FK)-stimulated AC enzyme activities in the hippocampus of strychnine-treated rats when compared to the control group. The capacity of SS to inhibit basal and FK-stimulated AC activity in the hippocampus was significantly lower in the strychnine group than in the control group. The ability of the stable GTP analogue 5'-guanylylimidodiphosphate [Gpp(NH)p] to inhibit FK-stimulated AC activity was also decreased in hippocampal membranes from strychnine-treated rats. These results suggest that the attenuated inhibition of AC by SS in hippocampal membranes from strychnine-treated rats may be caused by decreases in both Gi activity and in the number of SS receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Puebla
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
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59
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Gettys TW, Fields TA, Raymond JR. Selective activation of inhibitory G-protein alpha-subunits by partial agonists of the human 5-HT1A receptor. Biochemistry 1994; 33:4283-90. [PMID: 8155646 DOI: 10.1021/bi00180a024] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Plasma membranes from Chinese hamster ovary (CHO) cells transfected with the serotonin 5-HT1A receptor have been incubated with full or partial receptor agonists and the photoreactive GTP analog, 4-azidoanilido-[alpha-32P]-GTP ([32P]-AA-GTP), to characterize the resulting receptor-G-protein interactions. Subsequent solubilization and immunoprecipitation of the membranes with anti-G(i)alpha-2 or anti-G(i)alpha-3 immunoglobulins revealed that full and partial agonists produce concentration-dependent labeling of the respective G-proteins with [32P]-AA-GTP. Full agonists of the 5-HT1A receptor [serotonin 5-hydroxytryptamine (5-HT) and 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT)] produced a 7-12-fold increase in the labeling of G(i)alpha-2 and G(i)alpha-3, whereas partial agonists (rauwolscine and ipsapirone) produced a smaller incorporation (2-5-fold) of [32P]-AA-GTP by the same G-proteins. The concentration of agonist producing half-maximal binding of [32P]-AA-GTP by G(i)alpha-3 [5-HT, 48 +/- 1 nM; 8-OH-DPAT, 28 +/- 1 nM; ipsapirone, 22 +/- 6 nM] compared to G(i)alpha-2 [5-HT, 124 +/- 38 nM; 8-OH-DPAT, 40 +/- 1 nM, ipsapirone, 82 +/- 7 nM] was lower with all agonists except rauwolscine, where the EC50's were similar (G(i)alpha-2, 604 +/- 145 nM; Gi alpha-3, 708 +/- 130 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T W Gettys
- Department of Medicine, Medical University of South Carolina, Charleston 29425
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60
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Hou C, Gilbert R, Barber D. Subtype-specific signaling mechanisms of somatostatin receptors SSTR1 and SSTR2. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34068-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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61
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Baffy G, Yang L, Raj S, Manning D, Williamson J. G protein coupling to the thrombin receptor in Chinese hamster lung fibroblasts. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37219-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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62
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63
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Milligan G. Specificity and functional applications of antipeptide antisera which identify G-protein alpha subunits. Methods Enzymol 1994; 237:268-83. [PMID: 7935003 DOI: 10.1016/s0076-6879(94)37068-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- G Milligan
- Department of Biochemistry, University of Glasgow, Scotland, United Kingdom
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64
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Goetzl E, Shames R, Yang J, Birke F, Liu Y, Albert P, An S. Inhibition of human HL-60 cell responses to chemotactic factors by antisense messenger RNA depletion of G proteins. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42181-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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65
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Wax M, Patil R. A rationale for gene targeting in glaucoma therapy. JOURNAL OF OCULAR PHARMACOLOGY 1994; 10:403-10. [PMID: 8207343 DOI: 10.1089/jop.1994.10.403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
One of the mainstays of glaucoma treatment is the use of drugs that decrease the secretion of aqueous humor fluid from the ciliary epithelium. Unfortunately, many currently available drugs that decrease aqueous humor production such as beta-adrenergic antagonists, may cause serious systemic side effects such as cardiac arrhythmias and arrest, pulmonary dysfunction, and CNS side effects such as decreased libido and depression. Efforts to develop effective aqueous suppressants that offer decreased morbidity and mortality in comparison to those currently available will likely rely on the ability to alter the function of specific cellular events which underlie aqueous humor production by the ciliary epithelium. However, the secretory process which results in aqueous humor production is incompletely understood and the identification of precise cellular mechanisms which underlie this process remain to be established. We will present a rationale for genetic approaches to regulate gene expression so that aqueous humor production may be specifically targeted in glaucoma patients. Techniques of gene transfer including homologous exchange recombination, and expression of antisense genes, will be discussed.
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Affiliation(s)
- M Wax
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri
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66
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Albert PR. Heterologous expression of G protein-linked receptors in pituitary and fibroblast cell lines. VITAMINS AND HORMONES 1994; 48:59-109. [PMID: 7941429 DOI: 10.1016/s0083-6729(08)60496-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- P R Albert
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
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67
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Laugwitz KL, Spicher K, Schultz G, Offermanns S. Identification of receptor-activated G proteins: selective immunoprecipitation of photolabeled G-protein alpha subunits. Methods Enzymol 1994; 237:283-94. [PMID: 7935004 DOI: 10.1016/s0076-6879(94)37069-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- K L Laugwitz
- Institut für Pharmakologie, Freie Universität Berlin, Germany
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68
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Raymond JR, Olsen CL, Gettys TW. Cell-specific physical and functional coupling of human 5-HT1A receptors to inhibitory G protein alpha-subunits and lack of coupling to Gs alpha. Biochemistry 1993; 32:11064-73. [PMID: 8218170 DOI: 10.1021/bi00092a016] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have studied the physical and functional linkages of heterologously expressed human 5-HT1A receptors to G protein alpha-subunits in HeLa and CHO-K1 cells. HeLa cells expressed immunoreactivity to G(i) proteins with an apparent rank order of G(i) alpha 3 (approximately 1 pmol/mg of protein) >> G(i) alpha 1 (approximately 0.1 pmol/mg) >> G(i) alpha 2 (< 0.02 pmol/mg), whereas CHO-K1 cells expressed immunoreactivity to G(i) alpha 2 (approximately 5 pmol/mg) >> G(i) alpha 3 (approximately 0.7 pmol/mg), but not to G(i) alpha 1. Both cell lines expressed large and small forms of Gs alpha, but neither expressed detectable G(o) alpha. Agonist-promotable physical coupling of the 5-HT1A receptor to G proteins was examined with high-affinity agonist binding and with co-immunoprecipitation using rabbit anti-receptor IgG fractions. Agonist treatment induced coupling of the 5-HT1A receptors to G proteins with an apparent rank order of G(i) alpha 3 > G(i) alpha 1, G(i) alpha 2 in HeLa cells and G(i) alpha 3 > G(i) alpha 2 in CHO-K1 cells. Agonist-promotable functional coupling of the 5-HT1A receptors to inhibition of adenylylcyclase was measured in membranes derived from HeLa and CHO-K1 cells expressing approximately 2.5-3 pmol of receptors/mg of protein by preincubation with antisera raised against the carboxyl termini of the G(i) protein alpha-subunits. A noteworthy difference between the two cell types was that antisera against the predominant G protein (G(i) alpha 2) were substantially more efficacious than G(i) alpha 3 antisera at blocking functional coupling to adenylylcyclase inhibition in CHO-K1 cells, whereas in HeLa cells, antisera against nonpredominant G proteins (G(i) alpha 1/G(i) alpha 2) were equally as effective as those against the predominant G protein (G(i) alpha 3). No physical or functional coupling of the 5-HT1A receptor to Gs alpha isoforms was detected in either cell line. These findings suggest that the 5-HT1A receptor can physically couple to multiple distinct G(i) proteins in mammalian cell membranes and that functional coupling to adenylylcyclase inhibition may be mediated by G(i) alpha 1, G(i) alpha 2, and G(i) alpha 3. One factor influencing the relative importance of those G proteins for 5-HT1A receptor-inhibited adenylylcyclase activity appears to be their-relative levels of expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J R Raymond
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
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69
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Kaupmann K, Bruns C, Hoyer D, Seuwen K, Lübbert H. Distribution and second messenger coupling of four somatostatin receptor subtypes expressed in brain. FEBS Lett 1993; 331:53-9. [PMID: 8405411 DOI: 10.1016/0014-5793(93)80296-7] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The mRNA distribution in the brain and the coupling to cellular effector systems of four somatostatin receptors (SSTR1-4) was studied. All four SRIF receptor subtypes were expressed in cortex and hippocampus. In addition, SSTR1 mRNA was relatively abundant in the spinal cord whereas SSTR2 mRNA was also present in the striatum. The SSTR3 gene was predominantly expressed in the olfactory bulb and in the cerebellum. Conflicting results about the effector coupling of SSTR1-3 have been published previously. We have stably expressed human SSTR1-4 in HEK 293 human embryonal kidney cells. Agonist binding to the receptor subtypes, including the recently cloned SSTR4, inhibited the formation of forskolin-induced cAMP. Is is concluded that, in an appropriate cellular environment, all four receptor subtypes can functionally couple to the inhibition of adenylyl cyclase.
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70
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Hedin KE, Duerson K, Clapham DE. Specificity of receptor-G protein interactions: searching for the structure behind the signal. Cell Signal 1993; 5:505-18. [PMID: 8312128 DOI: 10.1016/0898-6568(93)90046-o] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- K E Hedin
- Department of Pharmacology, Mayo Foundation, Rochester, MN 55905
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71
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Cote TE, Gosse ME, Weems HB. Solubilization of high-affinity, guanine nucleotide-sensitive mu-opioid receptors from 7315c cell membranes. J Neurochem 1993; 61:973-8. [PMID: 8395567 DOI: 10.1111/j.1471-4159.1993.tb03610.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: 01/30/2023]
Abstract
High-affinity mu-opioid receptors have been solubilized from 7315c cell membranes. Occupancy of the membrane-associated receptors with morphine before their solubilization in the detergent 3-[(3-cholamidopropyl) dimethyl]-1-propane sulfonate was critical for stabilization of the receptor. The solubilized opioid receptor bound [3H]-etorphine with high affinity (KD = 0.304 +/- 0.06 nM; Bmax = 154 +/- 33 fmol/mg of protein). Of the membrane-associated [3H]etorphine binding sites, 40 +/- 5% were recovered in the solubilized fraction. Both mu-selective and non-selective enkephalins competed with [3H]etorphine for the solubilized binding sites; in contrast, delta- and kappa-opioid enkephalins failed to compete with [3H]etorphine for the solubilized binding sites at concentrations of < 1 microM. The mu-selective ligand [3H][D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin also bound with high affinity (KD = 0.79 nM; Bmax = 108 +/- 17 fmol/mg of protein) to the solubilized material. Of the membrane-associated [3H][D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin binding sites, 43 +/- 3% were recovered in the solubilized material. Guanosine 5'-O-(3-thiotriphosphate), GTP, and guanosine 5'-O-(2-thiodiphosphate), but not adenylylimidodiphosphate, diminished [3H][D-Ala2,N-Me-Phe4,Gly5-ol] enkephalin binding in a concentration-dependent manner. Finally, mu-opioid receptors from rat brain membranes were also solubilized in a high-affinity, guanine nucleotide-sensitive state if membrane-associated receptors were occupied with morphine before and during their solubilization with the detergent 3-[(3-cholamidopropyl)dimethyl]-1-propane sulfonate.
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Affiliation(s)
- T E Cote
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799
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72
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Abstract
As the properties of more and more isoforms of the molecules involved in G-protein-mediated signal transduction pathways are unravelled, surprising diversity and versatility are being revealed. The path from receptor to effector is not dictated exclusively by the alpha subunits of heterotrimetric G proteins. The nature of the beta lambda subunit complex probably controls interactions of G(alpha) with receptors. In addition, dissociation of G(alpha)-GTP from G(beta lambda)provides two signalling complexes, and these proteins regulate effectors independently or synergistically. Synergistic or conditional regulation of effectors by G(alpha) and G(beta lambda)can provide a molecular signal that records the association of independent events.
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Affiliation(s)
- J Iñiguez-Lluhi
- Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235, USA
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73
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Liapakis G, Politou E, Thermos K. Solubilization of active somatostatin receptors from rabbit retina. Biochem Pharmacol 1993; 45:1821-8. [PMID: 8494540 DOI: 10.1016/0006-2952(93)90439-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Somatostatin receptors from rabbit retinal membranes were solubilized in an active form using a mixture of the detergent n-octyl b-D-glucopyranoside (OG) and CHAPS. The binding of [125I]-Try11-somatostatin to the soluble extract was saturable and of high affinity, with an apparent affinity constant (Kd) of 0.60 +/- 0.20 nM and a maximum number of binding sites (Bmax) of 80 +/- 48 fmol/mg protein. The specific binding of [125I]Tyr11-somatostatin was inhibited in a dose-dependent manner only by the somatostatinergic analogs. The biochemical characteristics of both the membrane-bound and soluble receptors were studied by photoaffinity labeling techniques. Analysis by SDS-PAGE and subsequent autoradiography revealed the presence of a major protein of similar relative molecular mass (M(r) 54,000 and 57,000 for membrane and soluble sites, respectively). The photolabeling of this protein was specifically inhibited by somatostatin-28, somatostatin-14, SMS 201-995 (a synthetic octapeptide analog of somatostatin) but not by bombesin and somatostatin-28(1-14). The non-hydrolysable GTP analog guanosine-5'-O-(3-thio-triphosphate) (GTP gamma S) regulated the photolabeling of [125I]Tyr11-somatostatin to the membrane and soluble receptors. These studies describe for the first time the successful solubilization of the somatostatin receptor and the biochemical characterization of both membrane-bound and soluble receptors from rabbit retina.
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Affiliation(s)
- G Liapakis
- Department of Basic Sciences, School of Health Sciences, University of Crete, Stavrakia, Heraklion, Greece
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74
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Vardi N, Matesic DF, Manning DR, Liebman PA, Sterling P. Identification of a G-protein in depolarizing rod bipolar cells. Vis Neurosci 1993; 10:473-8. [PMID: 8388245 DOI: 10.1017/s0952523800004697] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Synaptic transmission from photoreceptors to depolarizing bipolar cells is mediated by the APB glutamate receptor. This receptor apparently is coupled to a G-protein which activates cGMP-phosphodiesterase to modulate cGMP levels and thus a cGMP-gated cation channel. We attempted to localize this system immunocytochemically using antibodies to various components of the rod phototransduction cascade, including Gt (transducin), phosphodiesterase, the cGMP-gated channel, and arrestin. All of these antibodies reacted strongly with rods, but none reacted with bipolar cells. Antibodies to a different G-protein, G(o), reacted strongly with rod bipolar cells of three mammalian species (which are depolarizing and APB-sensitive). Also stained were subpopulations of cone bipolar cells but not the major depolarizing type in cat (b1). G(o) antibody also stained certain salamander bipolar cells. Thus, across a wide range of species, G(o) is present in retinal bipolar cells, and at least some of these are depolarizing and APB-sensitive.
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Affiliation(s)
- N Vardi
- Department of Anatomy, University of Pennsylvania, Philadelphia 19104-6058
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75
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Brown P, Schonbrunn A. Affinity purification of a somatostatin receptor-G-protein complex demonstrates specificity in receptor-G-protein coupling. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53302-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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76
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Identification and quantification of Gi-type GTP-binding proteins that copurify with a pituitary somatostatin receptor. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53417-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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77
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Taylor JE. Somatostatin analogues and small-cell lung carcinoma. Recent Results Cancer Res 1993; 129:71-82. [PMID: 8102490 DOI: 10.1007/978-3-642-84956-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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78
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Abstract
The neuropeptide somatostatin (SRIF) has diverse physiological actions in the brain and endocrine organs. A family of SRIF receptors has recently been cloned that may mediate the distinct biological effects of SRIF. These receptors have a high degree of amino acid sequence similarity among themselves, but their sequences are different from any other receptors, indicating that they represent a distinct neurotransmitter receptor subfamily. The availability of the cloned receptors will now allow for detailed structure-function analysis of SRIF receptors and will facilitate development of subtype-selective agonists and antagonists that could be useful in the treatment of central nervous system and endocrine disorders.
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Affiliation(s)
- G I Bell
- Howard Hughes Medical Institute, University of Chicago, IL 60637
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79
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Shapiro MS, Hille B. Substance P and somatostatin inhibit calcium channels in rat sympathetic neurons via different G protein pathways. Neuron 1993; 10:11-20. [PMID: 7678964 DOI: 10.1016/0896-6273(93)90237-l] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We studied inhibition of N-type Ca2+ channels in rat superior cervical ganglion neurons by substance P (SP) and somatostatin-14 (Som). In whole-cell clamp, 70 of 82 acutely dissociated neurons showed inhibition (mean 37%) by 500 nM SP, and 54 of 61 showed inhibition by 240 nM Som (mean 57%). Pertussis toxin (PTX) blocked Som but not SP inhibition; intracellular dialysis with 2 mM GDP-beta-S attenuated inhibition with either peptide. Inhibition was voltage dependent with Som but not with SP. Neurokinin A (1 microM) or B was without effect, implicating NK1 tachykinin receptors. In cell-attached patches with bath-applied drugs, to test for a diffusible messenger, inhibition by SP or Som was only 8%. Thus, SP signaling is voltage independent and PTX insensitive; Som inhibition is voltage dependent and PTX sensitive; and both are membrane delimited.
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Affiliation(s)
- M S Shapiro
- Department of Physiology and Biophysics, University of Washington, Seattle 98195
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80
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Nakabayashi IO, Nakabayashi H. Monoclonal antibodies to somatostatin receptor of rat brain. Hybridoma (Larchmt) 1992; 11:789-94. [PMID: 1294456 DOI: 10.1089/hyb.1992.11.789] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Murine Monoclonal antibodies (MAbs) to the rat brain somatostatin (SRIF) receptor were produced. Sp 2/0 myeloma cells were fused with splenocytes of Balb/c mice immunized with the soluble rat brain SRIF receptor which was partially purified by gel-filtration chromatography. Screening by radioligand ([125I-Tyr11]SRIF-14) binding inhibition assay yielded three stable cell lines producing IgG1, IgM, or IgA antibody. Autoradiographic study of the polyacrylamide gel electrophoresed under nondenaturing conditions revealed that these MAbs inhibited the ligand binding to the receptor, regardless of their incubation with the receptor prior to the ligand binding. The results suggest that the MAbs produced are the antibodies to the ligand binding site of the receptor, and bind to the receptor in competition with the ligand.
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Affiliation(s)
- I O Nakabayashi
- Department of Immunology, Kanazawa University, Ishikawa, Japan
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81
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Iñiguez-Lluhi J, Simon M, Robishaw J, Gilman A. G protein beta gamma subunits synthesized in Sf9 cells. Functional characterization and the significance of prenylation of gamma. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)50106-x] [Citation(s) in RCA: 234] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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82
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Vanetti M, Kouba M, Wang X, Vogt G, Höllt V. Cloning and expression of a novel mouse somatostatin receptor (SSTR2B). FEBS Lett 1992; 311:290-4. [PMID: 1397330 DOI: 10.1016/0014-5793(92)81122-3] [Citation(s) in RCA: 192] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A mouse somatostatin (SS) receptor cDNA was cloned from neuroblastoma x glioma (NG108-15) cells. The sequence is almost identical to that of the mouse SSTR2 receptor [(1992) Proc. Natl. Acad. Sci. USA 89, 251)] but lacks about 300 nucleotides between transmembrane domain VII and the C-terminus. This spliced variant of SSTR2 (designated SSTR2B) encodes a protein which is 23 residues shorter than that predicted from the SSTR2 sequence, and differs in 15 amino acids at the C-terminus. mRNA corresponding to SSTR2B occurs in mouse tissues in higher abundance than that of SSTR2. SSTR2B binds SS peptides with high affinity when expressed in mammalian cells.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Blotting, Northern
- Cloning, Molecular
- DNA/genetics
- Gene Expression
- Glioma
- Humans
- Hybrid Cells
- Kinetics
- Mice
- Molecular Sequence Data
- Neuroblastoma
- Polymerase Chain Reaction
- RNA, Messenger/genetics
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- Receptors, Somatostatin/genetics
- Receptors, Somatostatin/metabolism
- Sequence Homology, Nucleic Acid
- Transcription, Genetic
- Tumor Cells, Cultured
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Affiliation(s)
- M Vanetti
- Department of Physiology, University of Munich, Germany
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83
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Surprenant A, Horstman DA, Akbarali H, Limbird LE. A point mutation of the alpha 2-adrenoceptor that blocks coupling to potassium but not calcium currents. Science 1992; 257:977-80. [PMID: 1354394 DOI: 10.1126/science.1354394] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The alpha 2A-adrenergic receptor (adrenoceptor) was stably expressed in AtT20 mouse pituitary tumor cells; adrenoceptor agonists inhibited adenylyl cyclase, inhibited voltage-dependent calcium currents, and increased inwardly rectifying potassium currents. An aspartic acid residue (Asp79) highly conserved among guanine nucleotide-binding protein (G protein)-coupled receptors was mutated to asparagine; in cells transfected with the mutant alpha 2-receptor, agonists inhibited adenylyl cyclase and calcium currents but did not increase potassium currents. Because distinct G proteins appear to couple adrenoceptors to potassium and calcium currents, the present findings suggest that the mutant alpha 2-adrenoceptor cannot achieve the conformation necessary to activate G proteins that mediate potassium channel activation.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Asparagine
- Aspartic Acid
- Brimonidine Tartrate
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels/physiology
- Cell Line
- Clonidine/pharmacology
- GTP-Binding Proteins/metabolism
- Membrane Potentials/drug effects
- Mutagenesis, Site-Directed
- Potassium Channels/drug effects
- Potassium Channels/metabolism
- Potassium Channels/physiology
- Quinoxalines/pharmacology
- Receptors, Adrenergic, alpha/drug effects
- Receptors, Adrenergic, alpha/metabolism
- Receptors, Adrenergic, alpha/physiology
- Receptors, Neurotransmitter/drug effects
- Receptors, Neurotransmitter/physiology
- Receptors, Somatostatin
- Recombinant Proteins/drug effects
- Recombinant Proteins/metabolism
- Somatostatin/metabolism
- Somatostatin/pharmacology
- Transfection
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Affiliation(s)
- A Surprenant
- Vollum Institute, Oregon Health Sciences University, Portland 97201
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84
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Raymond JR, Albers FJ, Middleton JP. Functional expression of human 5-HT1A receptors and differential coupling to second messengers in CHO cells. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1992; 346:127-37. [PMID: 1448178 DOI: 10.1007/bf00165293] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The signal transduction linkages of the cloned human 5-HT1A receptor as expressed stably in CHO cells were studied. A transfected clonal cell line which expresses 900 +/- 36 fmol 5-HT1A receptor/mg protein (designated CHO-5-HT1A/WT-27) responded to 5-HT and/or 8-OH-DPAT by coupling to several second messenger pathways. The 5-HT1A receptor inhibited, but did not stimulate, membrane adenylyl cyclase activity and whole cell cAMP accumulation in a dose-dependent manner (for 5-HT, IC50 = 146 +/- 27 and 55 +/- 12 nM, respectively). Activation of the receptor was associated with other signal transduction linkages: (i) a 40-50% increase in hydrolysis of inositol phosphates (for 5-HT, EC50 = 1.33 +/- 0.15 microM for 5-HT), (ii) a transient elevation of cytosolic Ca2+ levels (apparent at 1-100 microM 5-HT) which was not affected by chelation of extracellular Ca2+ by EGTA, and (iii) an augmentation of [3H]-arachidonic acid release pharmacologically with the calcium ionophore A23187 or by activation of endogenous thrombin or P2 purinergic receptors (for 5-HT, EC50 = 1.22 +/- 0.17 microM). This pathway may be an amplification mechanism for signaling in anatomic regions with high concentrations of several neuro-transmitters, hormones or autacoids, such as at neuronal junctions or near areas of platelet aggregation. All linkages were sensitive to pertussis toxin pre-treatment (IC50 approximately 0.5-0.6 ng/ml x 4.5 h for all pathways), suggesting the involvement of Gi protein(s) in these signal transduction pathways. Coupling to varied signal transduction pathways in a single cell system may be a common feature of receptors which classically inhibit adenylyl cyclase such as the 5-HT1A receptor.
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Affiliation(s)
- J R Raymond
- Department of Medicine (Nephrology), Duke University Medical Center, Durham, NC 27710
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85
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Kleuss C, Scherübl H, Hescheler J, Schultz G, Wittig B. Different beta-subunits determine G-protein interaction with transmembrane receptors. Nature 1992; 358:424-6. [PMID: 1322501 DOI: 10.1038/358424a0] [Citation(s) in RCA: 300] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Regulatory GTP-binding proteins (G proteins) are membrane-attached heterotrimers (alpha, beta, gamma) that mediate cellular responses to a wide variety of extracellular stimuli. They undergo a cycle of guanine-nucleotide exchange and GTP hydrolysis, during which they dissociate into alpha-subunit and beta gamma complex. The roles of G-protein alpha-subunits in these processes and for the specificity of signal transduction are largely established; the beta- and gamma-subunits are essential for receptor-induced G-protein activation and seem to be less diverse and less specific. Although the complementary DNAs for several beta-subunits have been cloned, isolated subunits have only been studied as beta gamma complexes. Functional differences have been ascribed to the gamma-subunit on the basis of extensive sequence similarity among beta-subunits and apparent heterogeneity in gamma-subunit sequences. Beta gamma complexes can interact directly or indirectly with different effectors. They seem to be interchangeable in their interaction with pertussis toxin-sensitive alpha-subunits, so we tested this by microinjecting antisense oligonucleotides into nuclei of a rat pituitary cell line to suppress the synthesis of individual beta-subunits selectively. Here we show that two out of four subtypes of beta-subunits tested (beta 1 and beta 3) are selectively involved in the signal transduction cascades from muscarinic M4 (ref. 4) and somatostatin receptors, respectively, to voltage-dependent Ca2+ channels.
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Affiliation(s)
- C Kleuss
- Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Germany
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86
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Bar-Sinai A, Marbach I, Shorr RG, Levitzki A. The GppNHp-activated adenylyl cyclase complex from turkey erythrocyte membranes can be isolated with its beta gamma subunits. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:703-8. [PMID: 1633821 DOI: 10.1111/j.1432-1033.1992.tb17098.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The adenylyl cyclase complex, derived from turkey erythrocyte membranes, was activated using guanosine 5'-[beta, gamma-imido]triphosphate (Gpp[NH]p) and separated under low-detergent and low-salt conditions using conventional molecular-sieve chromatography followed by high-pressure ion-exchange and molecular-sieve chromatography. Although the complex remains activated with Gpp[NH]p throughout the isolation, the beta gamma subunits copurify with the cyclase. The stoichiometry of the cyclase to the alpha subunit of the stimulatory guanosine-nucleotide-binding regulatory protein (alpha s) to the beta subunit is close to unity, demonstrating that the beta gamma subunits do not dissociate from the Gs.cyclase complex (Gs, guanosine-nucleotide-binding regulatory protein) upon activation of the enzyme. If the final purification step was performed at high-salt concentrations, the beta gamma subunits could be separated from the alpha s.cyclase complex. Previously reported results on bovine brain cyclase also showed that the Gs.cyclase complex remains intact subsequent to activation by hormone and Gpp[NH]p [Marbach, I., Bar-Sinai, A., Minich, M. and Levitzki, A. (1990) J. Biol. Chem. 265, 9999-10,004]. These results, using adenylyl cyclase from two different sources, support our previous kinetic experiments which first suggested that beta gamma subunits are not released from Gs upon cyclase activation. We, therefore, argue that the mode of adenylyl cyclase inhibition by the inhibitory guanosine-nucleotide-binding regulatory protein cannot be via shifting the alpha s to beta gamma equilibrium as is commonly believed, and an alternate hypothesis is proposed.
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Affiliation(s)
- A Bar-Sinai
- Department of Biological Chemistry, Hebrew University of Jerusalem, Israel
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87
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Okuma Y, Reisine T. Immunoprecipitation of alpha 2a-adrenergic receptor-GTP-binding protein complexes using GTP-binding protein selective antisera. Changes in receptor/GTP-binding protein interaction following agonist binding. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42114-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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88
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Affiliation(s)
- S Rens-Domiano
- Department of Pharmacology, University of Pennsylvania Medical School, Philadelphia 19104
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89
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Abstract
The diversity of the G protein-coupled receptor superfamily is now being realised with the molecular cloning of DNA encoding many new receptors and receptor subfamilies. The existing pharmacological definitions of receptor subtypes have been extended dramatically with identification of additional subtypes at the molecular level. Functional analysis of cloned receptors by expression in heterologous cell types has demonstrated that individual receptor subtypes can couple to a variety of different effector systems.
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Affiliation(s)
- T P Iismaa
- Garvan Institute of Medical Research, St Vincent's Hospital, Sydney, Australia
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90
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Heithier H, Fröhlich M, Dees C, Baumann M, Häring M, Gierschik P, Schiltz E, Vaz WL, Hekman M, Helmreich EJ. Subunit interactions of GTP-binding proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 204:1169-81. [PMID: 1312936 DOI: 10.1111/j.1432-1033.1992.tb16744.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fluorescence energy transfer [cf. Förster, T. (1948) Ann. Phys. 6, 55-75] was tested for its suitability to study quantitative interactions of subunits of G0 with each other and these subunits or trimeric G0 with the beta 1-adrenoceptor in detergent micelles or after reconstitution into lipid vesicles [according to Feder, D., Im, M.-J., Klein, H. W., Hekman, M., Holzhöfer, A, Dees, C., Levitzki, A., Helmreich, E. J. M. & Pfeuffer, T. (1986) EMBO J. 5, 1509-1514]. For this purpose, alpha 0- and beta gamma-subunits and trimeric G0 purified from bovine brain, the beta gamma-subunits from bovine rod outer segment membranes and the beta 1-adrenoceptor from the turkey erythrocyte were all labelled with either tetramethylrhodamine maleimide or fluorescein isothiocyanate under conditions which leave the labelled proteins functionally intact. In the case of alpha 0- and beta gamma-interactions, specific high-affinity binding interactions (Kd approximately 10 nM) and nonspecific low-affinity binding interactions (Kd approximately 1 microM) could be readily distinguished by comparing fluorescence energy transfer before and after dissociation with 10 microM guanosine 5'-O-[gamma-thio]triphosphate and 10 mM MgCl2 where only low-affinity binding interactions remained. Interactions between alpha 0- and beta gamma-subunits from bovine brain or from bovine retinal transducin did not differ much. The beta gamma-subunits from bovine brain were found to bind with high transfer efficiency and comparable affinities to the hormone-activated and the nonactivated beta 1-receptor reconstituted in lipid vesicles: Kd = 100 +/- 20 and 120 +/- 20 nM, respectively; however, beta gamma-subunits from transducin appeared to bind more weakly to the beta 1-adrenoceptor than beta gamma-subunits from bovine brain. Separated purified homologous alpha 0- and beta gamma-subunits from bovine brain interfered mutually with each other in binding to the beta 1-adrenoceptor presumably because they had a greater affinity for each other than for the receptor. These findings attest to the suitability of fluorescence energy transfer for studying protein-protein interactions of G-proteins and G-protein-linked receptors. Moreover, they supported the previous finding [Kurstjens, N. P., Fröhlich, M., Dees, C., Cantrill, R. C., Hekman, M. & Helmreich, E. J. M. (1991) Eur. J. Biochem. 197, 167-176] that beta gamma-subunits can bind to the nonactivated beta 1-adrenoceptor.
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Affiliation(s)
- H Heithier
- Department of Physiological Chemistry, University of Würzburg Medical School, Federal Republic of Germany
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91
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Murray-Whelan R, Schlegel W. Brain somatostatin receptor-G protein interaction. G alpha C-terminal antibodies demonstrate coupling of the soluble receptor with Gi(1-3) but not with Go. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50680-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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92
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Reisine T, Law SF. Pertussis Toxin in Analysis of Receptor Mechanisms. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/b978-0-12-185266-5.50031-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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