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Amaya CN, Perkins M, Belmont A, Herrera C, Nasrazadani A, Vargas A, Khayou T, Montoya A, Ballou Y, Galvan D, Rivas A, Rains S, Patel L, Ortega V, Lopez C, Chow W, Dickerson EB, Bryan BA. Non-selective beta blockers inhibit angiosarcoma cell viability and increase progression free- and overall-survival in patients diagnosed with metastatic angiosarcoma. Oncoscience 2018; 5:109-119. [PMID: 29854879 PMCID: PMC5978448 DOI: 10.18632/oncoscience.413] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 03/02/2018] [Indexed: 12/18/2022] Open
Abstract
Patients with metastatic angiosarcoma undergoing chemotherapy, radiation, and/or surgery experience a median progression free survival of less than 6 months and a median overall survival of less than 12 months. Given the aggressive nature of this cancer, angiosarcoma clinical responses to chemotherapy or targeted therapeutics are generally very poor. Inhibition of beta adrenergic receptor (β-AR) signaling has recently been shown to decrease angiosarcoma tumor cell viability, abrogate tumor growth in mouse models, and decrease proliferation rates in preclinical and clinical settings. In the current study we used cell and animal tumor models to show that β-AR antagonism abrogates mitogenic signaling and reduces angiosarcoma tumor cell viability, and these molecular alterations translated into patient tumors. We demonstrated that non-selective β-AR antagonists are superior to selective β-AR antagonists at inhibiting angiosarcoma cell viability. A prospective analysis of non- selective β-AR antagonists in a single arm clinical study of metastatic angiosarcoma patients revealed that incorporation of either propranolol or carvedilol into patients' treatment regimens leads to a median progression free and overall survival of 9 and 36 months, respectively. These data suggest that incorporation of non-selective β-AR antagonists into existing therapies against metastatic angiosarcoma can enhance clinical outcomes.
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Affiliation(s)
- Clarissa N Amaya
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Mariah Perkins
- Department of Biochemistry, Baylor University, Waco, TX, USA
| | - Andres Belmont
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Connie Herrera
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Arezo Nasrazadani
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Alejandro Vargas
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Thuraieh Khayou
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Alexa Montoya
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA.,Department of Biology, University of Texas, El Paso, TX, USA
| | - Yessenia Ballou
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Dana Galvan
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Alexandria Rivas
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Steven Rains
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Luv Patel
- Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Vanessa Ortega
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - Christopher Lopez
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA
| | - William Chow
- Mohs Micrographic Surgery and Cutaneous Oncology, San Leandro, CA, USA
| | - Erin B Dickerson
- Department of Veterinary Clinical Sciences, University of Minnesota, St. Paul, MN, USA.,Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Brad A Bryan
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, TX, USA.,Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, TX, USA
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2
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Burt R, Graves BM, Gao M, Li C, Williams DL, Fregoso SP, Hoover DB, Li Y, Wright GL, Wondergem R. 9-Phenanthrol and flufenamic acid inhibit calcium oscillations in HL-1 mouse cardiomyocytes. Cell Calcium 2013; 54:193-201. [PMID: 23831210 DOI: 10.1016/j.ceca.2013.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 05/27/2013] [Accepted: 06/09/2013] [Indexed: 11/17/2022]
Abstract
It is well established that intracellular calcium ([Ca2+]i) controls the inotropic state of the myocardium, and evidence mounts that a "Ca2+ clock" controls the chronotropic state of the heart. Recent findings describe a calcium-activated nonselective cation channel (NSCCa) in various cardiac preparations sharing hallmark characteristics of the transient receptor potential melastatin 4 (TRPM4). TRPM4 is functionally expressed throughout the heart and has been implicated as a NSCCa that mediates membrane depolarization. However, the functional significance of TRPM4 in regards to Ca2+ signaling and its effects on cellular excitability and pacemaker function remains inconclusive. Here, we show by Fura2 Ca-imaging that pharmacological inhibition of TRPM4 in HL-1 mouse cardiac myocytes by 9-phenanthrol (10 μM) and flufenamic acid (10 and 100 μM) decreases Ca2+ oscillations followed by an overall increase in [Ca2+]i. The latter occurs also in HL-1 cells in Ca(2+)-free solution and after depletion of sarcoplasmic reticulum Ca2+ with thapsigargin (10 μM). These pharmacologic agents also depolarize HL-1 cell mitochondrial membrane potential. Furthermore, by on-cell voltage clamp we show that 9-phenanthrol reversibly inhibits membrane current; by fluorescence immunohistochemistry we demonstrate that HL-1 cells display punctate surface labeling with TRPM4 antibody; and by immunoblotting using this antibody we show these cells express a 130-150 kDa protein, as expected for TRPM4. We conclude that 9-phenanthrol inhibits TRPM4 ion channels in HL-1 cells, which in turn decreases Ca2+ oscillations followed by a compensatory increase in [Ca2+]i from an intracellular store other than the sarcoplasmic reticulum. We speculate that the most likely source is the mitochondrion.
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Affiliation(s)
- Rees Burt
- Department of Biomedical Sciences, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA
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Koçer SS, Wang HY, Malbon CC. "Shaping" of cell signaling via AKAP-tethered PDE4D: Probing with AKAR2-AKAP5 biosensor. J Mol Signal 2012; 7:4. [PMID: 22583680 PMCID: PMC3493269 DOI: 10.1186/1750-2187-7-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 04/15/2012] [Indexed: 11/25/2022] Open
Abstract
Background PKA, a key regulator of cell signaling, phosphorylates a diverse and important array of target molecules and is spatially docked to members of the A-kinase Anchoring Protein (AKAP) family. AKAR2 is a biosensor which yields a FRET signal in vivo, when phosphorylated by PKA. AKAP5, a prominent member of the AKAP family, docks several signaling molecules including PKA, PDE4D, as well as GPCRs, and is obligate for the propagation of the activation of the mitogen-activated protein kinase cascade from GPCRs to ERK1,2. Results Using an AKAR2-AKAP5 fusion “biosensor”, we investigated the spatial-temporal activation of AKAP5 undergoing phosphorylation by PKA in response to β-adrenergic stimulation. The pattern of PKA activation reported by AKAR2-AKAP5 is a more rapid and spatially distinct from those “sensed” by AKAR2-AKAP12. Spatial-temporal restriction of activated PKA by AKAP5 was found to “shape” the signaling response. Phosphatase PDE4D tethered to AKAP5 also later reverses within 60 s elevated intracellular cyclic AMP levels stimulated by β-adrenergic agonist. AKAP12, however, fails to attenuate the rise in cyclic AMP over this time. Fusion of the AKAP5 PDE4D-binding-domain to AKAP12 was found to accelerate a reversal of accumulation of intracellular cyclic AMP. Conclusion AKAPs, which are scaffolds with tethered enzymes, can “shape” the temporal and spatial aspects of cell signaling.
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Affiliation(s)
- Salih S Koçer
- Department of Pharmacological Sciences, Health Sciences Center, BST-7, SUNY at Stony Brook, School of Medicine, Stony Brook, New York 11794-8651, USA.
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Tao J, Wang HY, Malbon CC. AKAR2-AKAP12 fusion protein "biosenses" dynamic phosphorylation and localization of a GPCR-based scaffold. J Mol Signal 2010; 5:3. [PMID: 20412577 PMCID: PMC2871262 DOI: 10.1186/1750-2187-5-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 04/22/2010] [Indexed: 11/24/2022] Open
Abstract
Background The cAMP-dependent protein kinase A (PKA) plays a pivotal role in virtually all cells, there being a multitude of important target molecules that are substrates for PKA in cell signaling. The spatial-temporal dynamics of PKA activation in living cells has been made accessible by the development of clever biosensors that yield a FRET signal in response to the phosphorylation by PKA. AKAR2 is genetically encoded fluorescent probe that acts as a biosensor for PKA activation. AKAP12 is a scaffold that docks PKA, G-protein-coupled receptors, cell membrane negatively-charged phospholipids, and catalyzes receptor resensitization and recycling. In the current work, the AKAR2 biosensor was fused to the N-terminus of AKAP12 to evaluate its ability to function and report on dynamic phosphorylation of the AKAP12 scaffold. Results AKAR2-AKAP12 can be expressed in mammalian cells, is fully functional, and reveals the spatial-temporal activation of AKAP12 undergoing phosphorylation by PKA in response to beta-adrenergic activation in human epidermoid carcinoma A431 cells. Conclusion The dynamic phosphorylation of AKAP12 "biosensed" by AKAR2-AKAP12 reveals the scaffold in association with the cell membrane, undergoing rapid phosphorylation by PKA. The perinuclear, cytoplasmic accumulation of phosphorylated scaffold reflects the phosphorylated, PKA-activated form of AKAP12, which catalyzes the resensitization and recycling of desensitized, internalized G-protein-coupled receptors.
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Affiliation(s)
- Jiangchuan Tao
- Department of Pharmacology, School of Medicine, Heath Sciences Center, SUNY/Stony Brook, Stony Brook, NY 11794-8651, USA.
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5
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Tao J, Malbon CC. G-protein-coupled receptor-associated A-kinase anchoring proteins AKAP5 and AKAP12: differential signaling to MAPK and GPCR recycling. J Mol Signal 2008; 3:19. [PMID: 19055733 PMCID: PMC2621157 DOI: 10.1186/1750-2187-3-19] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2008] [Accepted: 12/02/2008] [Indexed: 11/10/2022] Open
Abstract
Background A-kinase Anchoring Protein AKAP5 and AKAP12 both dock to the β2-adrenergic receptor, the former constitutively, the latter dynamically in response to activation of the receptor with agonist. Results In the current work we analyze the ability of each AKAP to contribute to two downstream signaling events, the activation of mitogen-activate protein kinase and the resensitization/recycling of the internalized, desensitized β2-adrenergic receptor to the cell membrane. Although both AKAP share a large number of docking partners in common (e.g., β2-adrenergic receptor, protein kinases A and C, protein phosphatase-2B, and negatively-charged membrane phospholipids), AKAP5 and AKAP12 are shown to segregate with respect to activation of Erk1,2 and to resensitization/recycling of β2-adrenergic receptor. A431 cells were found to highly express AKAP12, but little of AKAP5. HEK293 cells, in contrast, were found to highly express AKAP5, but little of AKAP12. Suppression of the expression of AKAP5 in either A431 cells or HEK293 cells leads to loss of the ability of the β2-adrenergic receptor to activate Erk1,2. Suppression of the expression of AKAP12 in either cell line leads to loss of the ability of these cells to resensitize the β2-adrenergic receptor. Conclusion Knock-down experiments of endogenous AKAP 5 and AKAP12 in two cell lines used commonly to study β2-adrenergic receptor signaling clearly discriminate between the activation of mitogen-activated protein kinase (a downstream read-out solely mediated by AKAP5) and receptor recycling (a downstream read-out solely mediated by AKAP12).
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Affiliation(s)
- Jiangchuan Tao
- Department of Pharmacology, School of Medicine, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
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6
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Doronin S, Shumay E, Wang HY, Malbon CC. Akt mediates sequestration of the beta(2)-adrenergic receptor in response to insulin. J Biol Chem 2002; 277:15124-31. [PMID: 11809767 DOI: 10.1074/jbc.m108771200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The counterregulation of catecholamine action by insulin includes insulin-stimulated sequestration of the beta(2)-adrenergic receptor. Herein we examined the signaling downstream of insulin receptor activation, focusing upon the role of 1-phosphatidylinositol 3-kinase and the serine-threonine protein kinase Akt (also known as protein kinase B) in the internalization of beta(2)-adrenergic receptors. Inhibition of 1-phosphatidylinositol 3-kinase by LY294002 blocks insulin-induced sequestration of the beta(2)-adrenergic receptor, implicating Akt in downstream signaling to the beta(2)-adrenergic receptor. Phosphorylation studies of the C-terminal cytoplasmic domain of the beta(2)-adrenergic receptor by Akt in vitro identified Ser(345) and Ser(346) within a consensus motif for Akt phosphorylation. Double mutation (i.e. S345A/S346A) within this motif abolishes insulin counterregulation of beta-adrenergic stimulation of cyclic AMP accumulation as well as insulin-stimulated sequestration. Furthermore, expression of constitutively activated Akt (T308D/S473D) mimics insulin action on cyclic AMP responses and beta(2)-adrenergic receptor internalization. Expression of the dominant-negative version of Akt (K179A/T308A/S473A), in contrast, abolishes both insulin counterregulation of the cyclic AMP response as well as insulin-stimulated sequestration of the beta(2)-adrenergic receptor. The action of the serine-threonine protein kinase Akt in insulin counterregulation mirrors the central role of protein kinase A in beta-agonist-induced desensitization.
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Affiliation(s)
- Sergey Doronin
- Department of Molecular Pharmacology, University Medical Center, State University of New York/Stony Brook, Stony Brook, New York 11794-8651, USA
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7
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Li M, Li C, Weingarten P, Bunzow JR, Grandy DK, Zhou QY. Association of dopamine D(3) receptors with actin-binding protein 280 (ABP-280). Biochem Pharmacol 2002; 63:859-63. [PMID: 11911837 DOI: 10.1016/s0006-2952(01)00932-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteins that bind to G protein-coupled receptors have been identified as regulators of receptor localization and signaling. In our previous studies, a cytoskeletal protein, actin-binding protein 280 (ABP-280), was found to associate with the third cytoplasmic loop of dopamine D(2) receptors. In this study, we demonstrate that ABP-280 also interacts with dopamine D(3) receptors, but not with D(4) receptors. Similar to the dopamine D(2) receptor, the D(3)/ABP-280 association is of signaling importance. In human melanoma M2 cells lacking ABP-280, D(3) receptors were unable to inhibit forskolin-stimulated cyclic AMP (cAMP) production significantly. D(4) receptors, however, exhibited a similar degree of inhibition of forskolin-stimulated cAMP production in ABP-280-deficient M2 cells and ABP-280-replent M2 subclones (A7 cells). Further experiments revealed that the D(3)/ABP-280 interaction was critically dependent upon a 36 amino acid carboxyl domain of the D(3) receptor third loop, which is conserved in the D(2) receptor but not in the D(4) receptor. Our results demonstrate a subtype-specific regulation of dopamine D(2)-family receptor signaling by the cytoskeletal protein ABP-280.
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Affiliation(s)
- Ming Li
- Department of Pharmacology, University of California, Room 360, Med. Surge II, Irvine, CA 92697-4625, USA
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8
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Doronin S, Shumay E, Wang HY, Malbon CC. Lithium suppresses signaling and induces rapid sequestration of beta2-adrenergic receptors. Biochem Biophys Res Commun 2001; 288:151-5. [PMID: 11594766 DOI: 10.1006/bbrc.2001.5755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lithium is a monovalent cation used therapeutically to treat a range of affective disorders (1), although the cellular mechanisms of lithium regulation that might contribute to its therapeutic effects at the level of neurotransmitter receptors are not known. Herein we report the ability of lithium to stimulate the internalization of beta2-adrenergic receptors. Lithium treatment of A431 human epidermoid carcinoma cells resulted in a rapid, prominent desensitization and internalization of beta2-adrenergic receptors. The ability of these receptors to generate a cyclic AMP response was strongly inhibited by lithium, at concentrations therapeutic in humans. Receptors for the serotonin (5HT1c) and for opiates (mu-opioid), in sharp contrast, resisted the effects of lithium on internalization. These data provide the first receptor-based mechanism to be described for lithium that could explain, in part, the therapeutic effects of lithium on affective disorders.
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Affiliation(s)
- S Doronin
- Department of Molecular Pharmacology, University Medical Center, SUNY/Stony Brook, NY 11794-8651, USA
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9
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Brydon L, Barrett P, Morgan PJ, Strosberg AD, Jockers R. Investigation of the human Mel 1a melatonin receptor using anti-receptor antibodies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 460:215-20. [PMID: 10810516 DOI: 10.1007/0-306-46814-x_23] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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10
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Li M, Bermak JC, Wang ZW, Zhou QY. Modulation of dopamine D(2) receptor signaling by actin-binding protein (ABP-280). Mol Pharmacol 2000; 57:446-52. [PMID: 10692483 DOI: 10.1124/mol.57.3.446] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Proteins that bind to G protein-coupled receptors have recently been identified as regulators of receptor anchoring and signaling. In this study, actin-binding protein 280 (ABP-280), a widely expressed cytoskeleton-associated protein that plays an important role in regulating cell morphology and motility, was found to associate with the third cytoplasmic loop of dopamine D(2) receptors. The specificity of this interaction was originally identified in a yeast two-hybrid screen and confirmed by protein binding. The functional significance of the D(2) receptor-ABP-280 association was evaluated in human melanoma cells lacking ABP-280. D(2) receptor agonists were less potent in inhibiting forskolin-stimulated cAMP production in these cells. Maximal inhibitory responses of D(2) receptor activation were also reduced. Further yeast two-hybrid experiments showed that ABP-280 association is critically dependent on the carboxyl domain of the D(2) receptor third cytoplasmic loop, where there is a potential serine phosphorylation site (S358). Serine 358 was replaced with aspartic acid to mimic the effects of receptor phosphorylation. This mutant (D(2)S358D) displayed compromised binding to ABP-280 and coupling to adenylate cyclase. PKC activation also generated D(2) receptor signaling attenuation, but only in ABP-containing cells, suggesting a PKC regulatory role in D(2)-ABP association. A mechanism for these results may be derived from a role of ABP-280 in the clustering of D(2) receptors, as determined by immunocytochemical analysis in ABP-deficient and replete cells. Our results suggest a new molecular mechanism of modulating D(2) receptor signaling by cytoskeletal protein interaction.
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Affiliation(s)
- M Li
- Department of Pharmacology, University of California, Irvine, California, USA
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11
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Schwencke C, Okumura S, Yamamoto M, Geng YJ, Ishikawa Y. Colocalization of ?-adrenergic receptors and caveolin within the plasma membrane. J Cell Biochem 1999. [DOI: 10.1002/(sici)1097-4644(19991001)75:1<64::aid-jcb7>3.0.co;2-l] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
Heterotrimeric G proteins in vertebrates constitute a family molecular switches that transduce the activation of a populous group of cell-surface receptors to a group of diverse effector units. The receptors include the photopigments such as rhodopsin and prominent families such as the adrenergic, muscarinic acetylcholine, and chemokine receptors involved in regulating a broad spectrum of responses in humans. Signals from receptors are sensed by heterotrimeric G proteins and transduced to effectors such as adenylyl cyclases, phospholipases, and various ion channels. Physiological regulation of G protein-linked receptors allows for integration of signals that directly or indirectly effect the signaling from receptor-->G protein-->effector(s). Steroid hormones can regulate signaling via transcriptional control of the activities of the genes encoding members of G protein-linked pathways. Posttranscriptional mechanisms are under physiological control, altering the stability of preexisting mRNA and affording an additional level for regulation. Protein phosphorylation, protein prenylation, and proteolysis constitute major posttranslational mechanisms employed in the physiological regulation of G protein-linked signaling. Drawing upon mechanisms at all three levels, physiological regulation permits integration of demands placed on G protein-linked signaling.
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Affiliation(s)
- A J Morris
- Department of Molecular Pharmacology, Diabetes and Metabolic Diseases Research Center, University Medical Center, State University of New York/Stony Brook, Stony Brook, New York 11794-8651, USA
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13
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Shih M, Lin F, Scott JD, Wang HY, Malbon CC. Dynamic complexes of beta2-adrenergic receptors with protein kinases and phosphatases and the role of gravin. J Biol Chem 1999; 274:1588-95. [PMID: 9880537 DOI: 10.1074/jbc.274.3.1588] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signals mediated by G-protein-linked receptors display agonist-induced attenuation and recovery involving both protein kinases and phosphatases. The role of protein kinases and phosphatases in agonist-induced attenuation and recovery of beta-adrenergic receptors was explored by two complementary approaches, antisense RNA suppression and co-immunoprecipitation of target elements. Protein phosphatases 2A and 2B are associated with the unstimulated receptor, the latter displaying a transient decrease followed by a 2-fold increase in the levels of association at 30 min following challenge with agonist. Protein kinase A displays a robust, agonist-induced association with beta-adrenergic receptors over the same period. Suppression of phosphatases 2A and 2B with antisense RNA or inhibition of their activity with calyculin A and FK506, respectively, blocks resensitization following agonist removal. Recycling of receptors to the plasma membrane following agonist-promoted sequestration is severely impaired by loss of either phosphatase 2B or protein kinase C. In addition, loss of protein kinase C diminishes association of phosphatase 2B with beta-adrenergic receptors. Overlay assays performed with the RII subunit of protein kinase A and co-immunoprecipitations reveal proteins of the A kinase-anchoring proteins (AKAP) family, including AKAP250 also known as gravin, associated with the beta-adrenergic receptor. Suppression of gravin expression disrupts recovery from agonist-induced desensitization, confirming the role of gravin in organization of G-protein-linked signaling complexes. The Ht31 peptide, which blocks AKAP protein-protein interactions, blocks association of beta-adrenergic receptors with protein kinase A. These data are the first to reveal dynamic complexes of beta-adrenergic receptors with protein kinases and phosphatases acting via an anchoring protein, gravin.
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Affiliation(s)
- M Shih
- Department of Molecular Pharmacology, Diabetes & Metabolic Diseases Research Program, University Medical Center, State University of New York, Stony Brook, New York 11794-8651, USA
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14
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Neylon CB, Nickashin A, Tkachuk VA, Bobik A. Heterotrimeric Gi protein is associated with the inositol 1,4,5-trisphosphate receptor complex and modulates calcium flux. Cell Calcium 1998; 23:281-9. [PMID: 9681191 DOI: 10.1016/s0143-4160(98)90024-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In vascular smooth muscle, pertussis toxin (PT) inhibits thrombin-induced Ca2+ release by a mechanism independent of its effect on IP3 formation. Thus, the possibility of a direct role of G alpha i proteins in regulating IP3-sensitive Ca2+ release was investigated by examining whether G alpha i proteins are associated with the IP3 receptor complex. Purified microsomal membranes were prepared and separated by sucrose density gradient centrifugation. The relative density of [3H]-IP3 binding sites between the microsomal fractions was inversely related to the distribution of the plasma membrane marker. The relative distribution of G alpha i3 determined by immunoblotting was closely correlated with the density of [3H]-IP3 binding. Levels of G alpha i2 were more evenly distributed with highest levels present in plasma membrane-enriched fractions. IP3 receptor immunoprecipitated from triton-solubilized microsomal membranes contained G alpha i3 immunoreactivity. To determine whether G alpha i proteins influence IP3-induced Ca2+ release, the effect of PT on Ca2+ release from digitonin-permeabilized cell suspensions using Fluo-3 was examined. Exposure to PT (0.1 microgram/ml, 5 min) attenuated the initial rate of IP3 (1 microM)-induced Ca2+ release. Together, these findings are consistent with the hypothesis that a heterotrimeric G alpha i protein directly regulates IP3-dependent Ca2+ release.
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MESH Headings
- Adenosine Diphosphate Ribose/metabolism
- Animals
- Aorta/cytology
- Calcium/metabolism
- Calcium Channels/drug effects
- Calcium Channels/physiology
- Cell Membrane Permeability/drug effects
- Cells, Cultured
- Digitonin/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/chemistry
- GTP-Binding Protein alpha Subunits, Gi-Go/physiology
- Inositol 1,4,5-Trisphosphate/physiology
- Inositol 1,4,5-Trisphosphate Receptors
- Ion Transport/drug effects
- Macromolecular Substances
- Microsomes/drug effects
- Microsomes/metabolism
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Pertussis Toxin
- Rats
- Rats, Inbred WKY
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/physiology
- Signal Transduction/physiology
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- C B Neylon
- Baker Medical Research Institute, Prahran, Victoria, Australia.
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15
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Huang C, Hepler JR, Chen LT, Gilman AG, Anderson RG, Mumby SM. Organization of G proteins and adenylyl cyclase at the plasma membrane. Mol Biol Cell 1997; 8:2365-78. [PMID: 9398661 PMCID: PMC25713 DOI: 10.1091/mbc.8.12.2365] [Citation(s) in RCA: 167] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/1997] [Accepted: 09/15/1997] [Indexed: 02/05/2023] Open
Abstract
There is mounting evidence for the organization and compartmentation of signaling molecules at the plasma membrane. We find that hormone-sensitive adenylyl cyclase activity is enriched in a subset of regulatory G protein-containing fractions of the plasma membrane. These subfractions resemble, in low buoyant density, structures of the plasma membrane termed caveolae. Immunofluorescence experiments revealed a punctate pattern of G protein alpha and beta subunits, consistent with concentration of these proteins at distinct sites on the plasma membrane. Partial coincidence of localization of G protein alpha subunits with caveolin (a marker for caveolae) was observed by double immunofluorescence. Results of immunogold electron microscopy suggest that some G protein is associated with invaginated caveolae, but most of the protein resides in irregular structures of the plasma membrane that could not be identified morphologically. Because regulated adenylyl cyclase activity is present in low-density subfractions of plasma membrane from a cell type (S49 lymphoma) that does not express caveolin, this protein is not required for organization of the adenylyl cyclase system. The data suggest that hormone-sensitive adenylyl cyclase systems are localized in a specialized subdomain of the plasma membrane that may optimize the efficiency and fidelity of signal transduction.
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Affiliation(s)
- C Huang
- Department of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-9041, USA
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16
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Nomura R, Inuo C, Takahashi Y, Asano T, Fujimoto T. Two-dimensional distribution of Gi2alpha in the plasma membrane: a critical evaluation by immunocytochemistry. FEBS Lett 1997; 415:139-44. [PMID: 9350984 DOI: 10.1016/s0014-5793(97)01114-9] [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: 02/05/2023]
Abstract
Caveolae have been postulated as a center for signal transduction, because many signaling molecules are concentrated in caveolin-rich fractions. We took Gi2alpha as an example and examined whether it is constitutively concentrated in caveolae. First, the behavior of caveolin and Gi2alpha in density-equilibrium ultracentrifugation was reexamined. By collecting fractions efficiently, caveolin and Gi2alpha were found to distribute differently. Secondly, by novel immunocytochemical methods it was found that the labeling density of Gi2alpha was 2.29 times higher in caveolae than in the non-caveolar plasma membrane. The results indicate that the concentration of Gi2alpha in caveolae is lower than deduced from most biochemical studies.
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Affiliation(s)
- R Nomura
- Department of Anatomy and Cell Biology, Gunma University School of Medicine, Maebashi, Japan
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17
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Hill RA, Sillence MN. Improved membrane isolation in the purification of beta 2-adrenoceptors from transgenic Escherichia coli. Protein Expr Purif 1997; 10:162-7. [PMID: 9179303 DOI: 10.1006/prep.1997.0732] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
beta 2-Adrenoceptors (beta 2-AR) have been purified from many mammalian tissues. Unfortunately, other beta-AR subtypes expressed in the same cells are usually copurified, contaminating the preparation and interfering with subsequent investigations such as receptor characterization, ligand binding studies, immunoprecipitation, or development of anti-receptor antibodies. The advent of molecular biology techniques has facilitated the expression of beta 2-AR in cells in which no other similar molecules are present; thus, receptor purification has been simplified. beta 2-AR expressed in Escherichia coli provides a convenient source of receptor without the need for specialized culture facilities required for eukaryotic cells. The greater complexity of the gram-negative cell wall structure, however, complicates the purification of membrane-bound receptor from this source. In this report, we describe a reliable method for the partial purification of membrane-bound beta 2-AR from transgenic E. coli. Spheroplast formation followed by cell disruption and a carbonate wash procedure provided beta 2-AR bound to bacterial inner membrane in high yield.
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Affiliation(s)
- R A Hill
- Tropical Beef Centre, Queensland Department of Primary Industries, Australia.
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18
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Bégin-Heick N, Black MA, Gaffield J, Cadrin M. Subcellular localization of G-proteins in primary-cultured mouse preadipocytes and adipocytes. J Cell Biochem 1997; 65:259-66. [PMID: 9136083 DOI: 10.1002/(sici)1097-4644(199705)65:2<259::aid-jcb11>3.0.co;2-d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The subcellular localization of G5 alpha, Gi alpha 1&2, Gi alpha 3, and G beta was studied in primary-cultured undifferentiated and differentiated, lipid replete, adipose cells. The results show a distinct distribution for each of these G-proteins and differences between differentiated and undifferentiated cells. All the G-proteins examined had a cytoplasmic localization; only Gi alpha 1 and 2 showed a significant colocalization with the plasma membrane and this only in differentiated cells. Most studies using cells in culture have reported an intracellular localization for G-proteins, whereas in tissue sections the localization has been reported to be largely with the plasma membrane, with some intracellular localization. The results suggest that the cell-cell interactions or the specific geometry imposed by culture conditions favor the intracellular compared to peripheral localization of G-proteins. Alternately, the posttranslational modifications necessary for G-protein insertion in the plasma membrane may be deficient in cultured cells.
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Affiliation(s)
- N Bégin-Heick
- Department of Biochemistry, University of Ottawa, Ontario, Canada.
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19
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Allgeier A, Laugwitz KL, Van Sande J, Schultz G, Dumont JE. Multiple G-protein coupling of the dog thyrotropin receptor. Mol Cell Endocrinol 1997; 127:81-90. [PMID: 9099903 DOI: 10.1016/s0303-7207(96)03996-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We investigated, in dog thyroid membranes, the ability of the dog thyrotropin (TSH) receptor to interact with the endogenous G proteins expressed in this tissue. Activation of the receptor led to increased incorporation of the photoreactive GTP analog [alpha-(32)P]GTP azidoanilide into immunoprecipitated alpha subunits of three G protein families: G(s), G(q/11), G(i/o). This effect was not due to a general loss of receptor G protein specificity since carbamylcholine, in the same membrane preparations, only stimulated the binding of the GTP analog to the alpha subunits of G(q/11) proteins. To investigate the multiple coupling of the dog TSH receptor in intact cells, cyclic AMP accumulation, IP(3) formation and (45)Ca2+ efflux experiments were performed. When thyrocytes were pretreated with pertussis toxin (PTX), the TSH receptor-mediated accumulation of cAMP increased by approximately 45% with TSH at 1 mU/ml, suggesting that the TSH receptor coupled to both G(s) and G(i) in vivo. On the other hand, no increase in IP(3) accumulation nor Ca2+ efflux was observed in the presence of thyrotropin. These data in intact cells are thus in contradiction with those obtained in membranes, suggesting that receptor-mediated transmembrane signalling may implicate a specificity which itself may reflect a localization and organization of the different components (receptors, G proteins, ...) in the plasma membrane of intact cells. As in some cells, G(i) activates mitogenesis by hormone activated G-protein-coupled receptors, we tested its role in the stimulation by TSH of the proliferation of thyrocytes. This was not affected by PTX, suggesting that the mitogenic effect of TSH does not involve G(i)-proteins.
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Affiliation(s)
- A Allgeier
- Institute of Interdisciplinary Research, University of Brussels, Belgium
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20
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Exton JH. Cell signalling through guanine-nucleotide-binding regulatory proteins (G proteins) and phospholipases. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 243:10-20. [PMID: 9030716 DOI: 10.1111/j.1432-1033.1997.t01-1-00010.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Phospholipases are important enzymes in cell signal transduction since they hydrolyze membrane phospholipids to generate signalling molecules. Heterotrimeric guanine-nucleotide-binding regulatory proteins (G proteins) play a major role in their regulation by a variety of agonists that activate receptors with seven membrane-spanning domains. Phospholipases of the C type, which hydrolyze inositol phospholipids to yield inositol trisphosphate and diacylglycerol, are regulated by the alpha and betagamma subunits of certain heterotrimeric G proteins as well as by receptor-associated and non-receptor-associated tyrosine kinases. Phospholipases of the D type, which hydrolyze phosphatidylcholine to phosphatidic acid, are regulated by members of the ADP-ribosylation factor and Rho subfamilies of small G proteins, and by protein kinase C and other factors. This review presents recent information concerning the molecular details of G protein regulation of these phospholipases.
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Affiliation(s)
- J H Exton
- Howard Hughes Medical Institute, Department of Molecular Physiology, Vanderbilt University School of Medicine, Nashville, TN 37295, USA
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21
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Cadrin M, McFarlane-Anderson N, Harper ME, Gaffield J, Bégin-Heick N. Comparison of the subcellular distribution of G-proteins in hepatocytes in situ and in primary cultures. J Cell Biochem 1996; 62:334-41. [PMID: 8872605 DOI: 10.1002/(sici)1097-4644(199609)62:3<334::aid-jcb4>3.0.co;2-s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The subcellular localization of the heterotrimeric G-proteins in hepatocytes in situ was compared to that in hepatocytes in primary culture. The ability of various ligands to activate adenylyl cyclase (AC) in membrane preparations was also investigated. In hepatocytes in situ the G proteins were mainly localized at the plasma membrane while in hepatocytes in culture they were predominantly cytoplasmic. The localization of the G-proteins in hepatocytes in situ correlates with their role in signal transduction. In homogenates prepared from the cultured cells, ligands which stimulate AC via Gs alpha were without effect, which was consistent with the localization of Gs alpha in the cytoplasmic and nuclear compartments. The "relocalization" of the G proteins to the cytoplasm when cells are cultured suggests that transmembrane signalling may be regulated by cell differentiation and cell-cell and cell-extracellular matrix interactions.
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Affiliation(s)
- M Cadrin
- Department of Biochemistry, University of Ottawa, Canada
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22
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Ng GY, Trogadis J, Stevens J, Bouvier M, O'Dowd BF, George SR. Agonist-induced desensitization of dopamine D1 receptor-stimulated adenylyl cyclase activity is temporally and biochemically separated from D1 receptor internalization. Proc Natl Acad Sci U S A 1995; 92:10157-61. [PMID: 7479745 PMCID: PMC40755 DOI: 10.1073/pnas.92.22.10157] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The regulation of the dopamine D1 receptor was investigated by using c-myc epitope-tagged D1 receptors expressed in Sf9 (fall armyworm ovary) cells. Treatment of D1 receptors with 10 microM dopamine for 15 min led to a loss of the dopamine-detected high-affinity state of the receptor accompanying a 40% reduction in the ability of the receptor to mediate maximal dopamine stimulation of adenylyl cyclase activity. After 60 min of agonist exposure, 45 min after the occurrence of desensitization, 28% of the cell surface receptors were internalized into an intracellular light vesicular membrane fraction as determined by radioligand binding and supported by photoaffinity labeling, immunocytochemical staining, and immunoblot analysis. Pretreatment of cells with concanavalin A or sucrose completely blocked agonist-induced D1 receptor internalization without preventing agonist-induced desensitization, indicating a biochemical separation of these processes. Collectively, these findings indicate that the desensitization of D1 receptor-coupled adenylyl cyclase activity and D1 receptor internalization are temporarily and biochemically distinct mechanisms regulating D1 receptor function following agonist activation.
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Affiliation(s)
- G Y Ng
- Department of Pharmacology, University of Toronto, Canada
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23
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Scotland G, Houslay MD. Chimeric constructs show that the unique N-terminal domain of the cyclic AMP phosphodiesterase RD1 (RNPDE4A1A; rPDE-IVA1) can confer membrane association upon the normally cytosolic protein chloramphenicol acetyltransferase. Biochem J 1995; 308 ( Pt 2):673-81. [PMID: 7772057 PMCID: PMC1136979 DOI: 10.1042/bj3080673] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A novel plasmid was generated which allowed the expression of the cytosolic bacterial enzyme chloramphenicol acetyl transferase (CAT) in COS-7 cells. Upon transfection, the majority of the novel CAT activity was found in the cytosol fraction of COS cells. Chimeric molecules were made between N-terminal portions of the type IVA cyclic AMP-specific rat 'dunce-like' phosphodiesterase (RD1) (RNPDE4A1A; rPDE-IVA1) fused to CAT at its N-terminus. Expression in COS-7 cells of chimeras formed from 1-100RD1-CAT and 1-25RD1-CAT now showed CAT activity associated with the membrane fraction. In contrast, a chimera formed from 26-100RD1-CAT showed an identical expression pattern to native CAT, with the major fraction of CAT activity occurring in the cytosol fraction. Membrane-bound CAT activity provided by 1-100RD1-CAT and 1-25RD1-CAT was not released by either high-salt or washing treatments but was solubilized in a dose-dependent fashion by the non-ionic detergent Triton X-100. Subcellular fractionation of COS-7 cells showed that, as with RD1, the membrane-bound activity of the RD1-CAT chimera followed that of the plasma membrane marker 5'-nucleotidase. Plasmids containing chimeric cDNAs were exposed to a coupled transcription-translation system that, in addition to the full-length chimeras, was found to generate a range of N-terminal truncated species due to initiation at different methionine residues. Incubation of the mature protein products formed in this system with a COS cell membrane fraction showed that only those chimeric CAT constructs containing the first 25 amino acids of RD1 became membrane-associated. The unique 25 amino acid N-terminal domain of RD1 contains structural information that can confer membrane association upon an essentially soluble protein.
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Affiliation(s)
- G Scotland
- Department of Biochemistry, University of Glasgow, U.K
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24
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Shakur Y, Wilson M, Pooley L, Lobban M, Griffiths SL, Campbell AM, Beattie J, Daly C, Houslay MD. Identification and characterization of the type-IVA cyclic AMP-specific phosphodiesterase RD1 as a membrane-bound protein expressed in cerebellum. Biochem J 1995; 306 ( Pt 3):801-9. [PMID: 7702577 PMCID: PMC1136592 DOI: 10.1042/bj3060801] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An antiserum was generated against a dodecapeptide whose sequence is found at the C-terminus of a cyclic AMP (cAMP)-specific, type-IVA phosphodiesterase encoded by the rat 'dunc-like' cyclic AMP phosphodiesterase (RD1) cDNA. This antiserum identified a single approximately 73 kDa protein species upon immunoblotting of cerebellum homogenates. This species co-migrated upon SDS/PAGE with a single immunoreactive species observed in COS cells transfected with the cDNA for RD1. Native RD1 in cerebellum was found to be predominantly (approximately 93%) membrane-associated and could be found in isolated synaptosome populations, in particular those enriched in post-synaptic densities. Fractionation of lysed synaptosomes on sucrose density gradients identified RD1 as co-migrating with the plasma membrane marker 5'-nucleotidase. Laser scanning confocal and digital deconvolution immunofluorescence studies done on intact COS cells transfected with RD1 cDNA showed RD1 to be predominantly localized to plasma membranes but also associated with the Golgi apparatus and intracellular vesicles. RD1-specific antisera immunoprecipitated phosphodiesterase activity from solubilized cerebellum membranes. This activity had the characteristics expected of the type-IV cAMP phosphodiesterase RD1 in that it was cAMP specific, exhibited a low Km cAMP of 2.3 microM, high sensitivity to inhibition by 4-[3-(cyclopentoxyl)-4-methoxyphenyl]-2-pyrrolidone (rolipram) (Ki approximately 0.7 microM) and was unaffected by Ca2+/calmodulin and low concentrations of cyclic GMP. The phosphodiesterase activities of RD1 solubilized from both cerebellum and transfected COS cell membranes showed identical first-order thermal denaturation kinetics at 50 degrees C. Native RD1 from cerebellum was shown to be an integral protein in that it was solubilized using the non-ionic detergent Triton X-100 but not by either re-homogenization or high NaCl concentrations. The observation that hydroxylamine was unable to cause the release of RD1 from either cerebellum or COS membranes and that [3H]palmitate was not incorporated into the RD1 protein immunoprecipitated from COS cells transfected with RD1 cDNA, indicated that RD1 was not anchored by N-terminal acylation. The engineered deletion of the 25 residues forming the unique N-terminal domain of RD1 caused both a profound increase in its activity (approximately 2-fold increase in Vmax) and a profound change in intracellular distribution. Thus, immunofluorescence studies identified the N-terminal truncated species as occurring exclusively ion the cytosol of transfected COS cells. The cDNA for RD1 thus appears to encode a native full-length type-IVA phosphodiesterase that is expressed in cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- Y Shakur
- Division of Biochemistry and Molecular Biology, University of Glasgow, Scotland, U.K
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25
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Kwon G, Axelrod D, Neubig RR. Lateral mobility of tetramethylrhodamine (TMR) labelled G protein alpha and beta gamma subunits in NG 108-15 cells. Cell Signal 1994; 6:663-79. [PMID: 7857770 DOI: 10.1016/0898-6568(94)90049-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Multi-step signal transducing events, such as those mediated by G proteins, have been difficult to study in intact cells. We prepared fluorescently labelled G protein subunits, tetramethylrhodamine-alpha o (TMR-alpha o) and TMR-beta gamma, in order to study their subcellular distribution and lateral mobility. Heterotrimeric G proteins labelled in the alpha (TMR-alpha o/beta gamma) or beta (TMR-beta gamma/alpha o) subunit were reconstituted into lipid vesicles and fused to NG-108-15 cells using polyethylene glycol (PEG). Vesicles fused completely to the cells as determined by dequenching of a fluorescent lipid probe, octadecyl rhodamine B. The orientation of G protein beta gamma subunits after fusion followed the expected random distribution; the quenching of surface fluorescence with anti-fluorescein antibodies showed that about 50% of the label was accessible extracellularly. G proteins incorporated by the fusion method were able to couple to endogenous alpha 2 adrenergic receptors based on the restoration of high affinity agonist binding to pertussis toxin-treated cells. The subcellular localization of TMR-alpha o and TMR-beta gamma determined by differential centrifugation and confocal microscopy indicated that TMR-alpha o was present in the plasma membrane and in intracellular membranes, whereas TMR-beta gamma was mainly localized in the plasma membrane. The lateral mobility of TMR-alpha o and TMR-beta gamma measured using fluorescence recovery after photobleaching (FRAP) demonstrated low mobile fractions of 0.34 +/- 0.03 and 0.16 +/- 0.03, respectively. The translational diffusion coefficients of the mobile components were similar, 4.0 x 10(-9) and 2.0 x 10(-9) cm2/s, for alpha and beta gamma respectively. Neither activation of Gi-linked receptors nor cytoskeletal disruption with nocodozole or cytochalasin D changed the mobile fraction or diffusion coefficient of the alpha or beta gamma subunits. The FRAP data combined with the localization of fluorescent subunits by confocal microscopy suggest that the beta gamma subunits are highly constrained to localized regions of the plasma membrane while the alpha subunit may diffuse in intracellular regions to transmit signals from receptors to effector proteins.
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Affiliation(s)
- G Kwon
- Department of Pharmacology, University of Michigan, Ann Arbor 48109-0626
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26
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Fisher RS, Levine MS, Sibley DR, Ariano MA. D2 dopamine receptor protein location: Golgi impregnation-gold toned and ultrastructural analysis of the rat neostriatum. J Neurosci Res 1994; 38:551-64. [PMID: 7529326 DOI: 10.1002/jnr.490380508] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The neostriatal distribution of D2 dopamine receptor protein has been assessed using subtype-selective polyclonal antibodies generated against three unique polypeptide sequences of the receptor. The experimental tissues were processed by peroxidase based immunohistochemical procedures for routine light microscopy, Golgi impregnation-gold toned morphological characterization, and correlative light/electron microscopy. The results demonstrated a regional gradient of D2-like dopamine receptor expression in the neostriatum, where lateral portions in the nucleus exhibited more reactive cell bodies than medial portions. D2-like expression was detected in the three populations of neostriatal neurons, i.e., the medium-sized spiny projection neurons, and the medium- and large-sized aspiny interneuron types. Morphometric measurements of labeled neurons verified that medium and large diameter neurons expressed the D2-like receptor subtype. D2-like immunoreactivity was distributed throughout the cytoplasm in dendritic processes, and in presynaptic terminal boutons. Immunoreactivity for the receptor protein was also detected in small, thinly myelinated axons, suggesting the possibilities of anterograde transport of the receptor from cell bodies in the substantia nigra to their neostriatal terminal fields, as well as from local axon collaterals of neostriatal projections neurons. These findings provide evidence of widespread distribution of the D2-like receptor protein in neostriatal neurons, and showed that the presynaptic D2 receptors contain analogous epitopes to the postsynaptic receptor subtype.
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Affiliation(s)
- R S Fisher
- Mental Retardation Research Center, UCLA School of Medicine
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27
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Ariano MA, Sibley DR. Dopamine receptor distribution in the rat CNS: elucidation using anti-peptide antisera directed against D1A and D3 subtypes. Brain Res 1994; 649:95-110. [PMID: 7953659 DOI: 10.1016/0006-8993(94)91052-9] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Anti-peptide antibodies were generated against amino acid sequences of intracellular and extracellular portions of the native proteins for the cloned rat D1A and D3 dopamine receptor subtypes in order to determine the cellular distribution of these specific forms in the brain. These polyclonal antisera exhibited high specific titers, assessed by ELISA and immunofluorescent detection of functional recombinant receptor proteins expressed in stably transfected Chinese hamster ovary (CHO) cells. Central nervous system (CNS) areas of the male rat were examined using standard immunofluorescent methods in fresh frozen tissues. This paradigm detected D1A-like and D3-like dopamine receptor staining primarily in larger-sized neurons throughout layers 3 and 5 of the cortex, in medium-diameter somata of the striatum, and in the densely packed cells of the olfactory tubercle and hippocampal formation. More attenuated immunoreactivity for both dopamine receptor subtypes was noted in the substantia nigra, not associated with perikarya. Differences in cellular staining patterns and intensity were evident between the D1A-like and D3-like dopamine receptor subtypes. Equivalent morphological elements exhibited dopamine receptor expression following incubation using antisera generated against either extracellular or intracellular epitopes of either the D1A or D3 native proteins. Dopamine receptor immunoreactivity could not be detected in the cerebellum at equivalent antisera dilutions used to discriminate cellular staining patterns within the forebrain. Fluorescent-labeled latex microspheres were infused into the substantia nigra terminal fields to retrogradely identify the cell bodies of the striatonigral projection system. This paradigm showed that 80% of striatonigral neurons expressed D1A-like receptors, while 65% demonstrated D3-like dopamine receptor staining. This distribution for the D1A-like and D3-like receptor subtypes suggests that overlap may occur in the expression of the receptors in the striatonigral neuron population. Our previous results localizing cellular D2-like receptor expression patterns in this projection system of the rat neostriatum implies that all three of these dopamine receptor subtypes may be co-expressed in this efferent system.
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Affiliation(s)
- M A Ariano
- Department of Neuroscience, Chicago Medical School, North Chicago, IL 60064
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28
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McFarlane-Anderson N, Cadrin M, Bégin-Heick N. Identification and localization of G-proteins in the clonal adipocyte cell lines HGFu and Ob17. J Cell Biochem 1993; 52:463-75. [PMID: 8227177 DOI: 10.1002/jcb.240520410] [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: 01/29/2023]
Abstract
HGFu and Ob17 are cell lines derived from adipose tissue of lean (+/?) and ob/ob mice, respectively. Neither adenylyl cyclase activity nor G protein abundance and subcellular distribution have been assessed previously in these cells. Cyclase activity was low and resistant to catecholamine stimulation in both cell lines. However, the enzyme could be stimulated to high levels by forskolin and Mn2+. Gs alpha (largely the long isoform), Gi alpha 2, and G beta were the major G protein subunits identified. The levels of G protein mRNA expression were similar in both cell lines and, unlike actin expression, did not change as a result of differentiation. Immunoblotting and ADP-ribosylation of the G peptides corroborated these results. Assessment of the subcellular localization of the subunits by indirect epifluorescence and scanning confocal microscopy showed that each of the subunits had a characteristic subcellular pattern. Gs alpha showed vesicular cytoplasmic and nuclear staining; Gi alpha 2 colocalized with actin stress fibers and disruption of these structures altered the distribution of Gi alpha 2; beta subunits showed some colocalization with the stress fibers as well as a cytoplasmic vesicular and nuclear pattern. As a result of differentiation, there was reorganization of the actin, together with the Gi alpha 2 and beta fibrous patterns. Both cell lines showed similar modifications. The induction of differentiation in these cells is therefore not associated with changes in adenylyl cyclase activity nor of the abundance of G-protein subunits, although reorganization of some of these subunits does accompany actin reorganization.
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30
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Port J, Hadcock J, Malbon C. Cross-regulation between G-protein-mediated pathways. Acute activation of the inhibitory pathway of adenylylcyclase reduces beta 2-adrenergic receptor phosphorylation and increases beta-adrenergic responsiveness. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42468-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Muntz KH, Sternweis PC, Gilman AG, Mumby SM. Influence of gamma subunit prenylation on association of guanine nucleotide-binding regulatory proteins with membranes. Mol Biol Cell 1992; 3:49-61. [PMID: 1550955 PMCID: PMC275501 DOI: 10.1091/mbc.3.1.49] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Two approaches were taken to address the possible role of gamma-subunit prenylation in dictating the cellular distribution of guanine nucleotide-binding regulatory proteins. Prenylation of gamma subunits was prevented by site-directed mutagenesis or by inhibiting the synthesis of mevalonate, the precursor of cellular isoprenoids. When beta or gamma subunits were transiently expressed in COS-M6 simian kidney cells (COS) cells, the proteins were found in the membrane fraction by immunoblotting. Immunofluorescence experiments indicated that the proteins were distributed to intracellular structures in addition to plasma membranes. Replacement of Cys68 of gamma with Ser prevented prenylation of the mutant protein and association of the protein with the membrane fraction of COS cells. Immunoblotting results demonstrated that some of the beta subunits were found in the cytoplasm when coexpressed with the nonprenylated mutant gamma subunit. When Neuro 2A cells were treated with compactin to inhibit protein prenylation, a fraction of endogenous beta and gamma was distributed in the cytoplasm. It is concluded that prenylation facilitates association of gamma subunits with membranes, that the cellular location of gamma influences the distribution of beta, and that prenylation is not an absolute requirement for interaction of beta and gamma.
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Affiliation(s)
- K H Muntz
- Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235
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32
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Bahouth SW, Wang HY, Malbon CC. Immunological approaches for probing receptor structure and function. Trends Pharmacol Sci 1991; 12:338-43. [PMID: 1659002 DOI: 10.1016/0165-6147(91)90593-h] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Molecular cloning has revealed the primary sequence of numerous membrane receptors, and this information catalysed two important efforts: modeling of receptor structure by hydropathy analysis and generating sequence-specific immunological probes with which these models can be tested experimentally. Craig Malbon and his colleagues outline the recent advances that illustrate how anti-peptide antibodies raised to synthetic sequences of membrane receptor have generated new information on the topology, functional domains and cellular localization of transmembrane signaling elements. They focus on two examples, the G protein-linked beta-adrenoceptor, and the nicotinic acetylcholine receptor, an intrinsic ion channel receptor. These two classes of receptor provide templates for the analysis of topographical models of membrane proteins with immunological probes, especially anti-peptide antibodies, and demonstrate how these results complement those obtained from molecular, biochemical and biophysical techniques. Although this powerful strategy is not without faults, it is likely to continue to be applied successfully to the analysis of the structure and function of receptors, ion channels and other membrane proteins.
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Affiliation(s)
- S W Bahouth
- Department of Pharmacology, College of Medicine, University of Tennessee, Memphis 38163
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33
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Cross-regulation between G-protein-mediated pathways. Activation of the inhibitory pathway of adenylylcylclase increases the expression of beta 2-adrenergic receptors. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99045-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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34
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Morris GM, Hadcock JR, Malbon CC. Cross-regulation between G-protein-coupled receptors. Activation of beta 2-adrenergic receptors increases alpha 1-adrenergic receptor mRNA levels. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52233-x] [Citation(s) in RCA: 47] [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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Wang HY, Berrios M, Hadcock JR, Malbon CC. The biology of beta-adrenergic receptors: analysis in human epidermoid carcinoma A431 cells. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1991; 23:7-20. [PMID: 1850702 DOI: 10.1016/0020-711x(91)90003-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. G-protein-linked transmembrane signaling has emerged as a major pathway for information transduction across the cell membrane. 2. In addition to photopigments that propagate the signal from light, cell-surface receptors for hormones, neurotransmitters, and autacoids propagate signals from ligand binding to membrane-bound effector units via G-proteins. 3. Biochemical and molecular features of one prominent member of these receptors, the beta-adrenergic receptor, will be highlighted in the present article. 4. The role of the human epidermoid carcinoma A431 cells as a model for the study of the structure and biology of beta-adrenergic receptors will be emphasized. 5. A model for receptor regulation, gleaned from recent advances in the biochemistry, cell and molecular biology of beta-adrenergic receptors, is discussed.
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Affiliation(s)
- H Y Wang
- Department of Biochemistry, National Defence Medical Center, Taipei, Taiwan, Republic of China
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Hadcock J, Ros M, Watkins D, Malbon C. Cross-regulation between G-protein-mediated pathways. Stimulation of adenylyl cyclase increases expression of the inhibitory G-protein, Gi alpha 2. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77181-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Nakamura S, Rodbell M. Octyl glucoside extracts GTP-binding regulatory proteins from rat brain "synaptoneurosomes" as large, polydisperse structures devoid of beta gamma complexes and sensitive to disaggregation by guanine nucleotides. Proc Natl Acad Sci U S A 1990; 87:6413-7. [PMID: 2117281 PMCID: PMC54544 DOI: 10.1073/pnas.87.16.6413] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
GTP-binding regulatory proteins are generally purified from cholate-extracted membranes in the form of heterotrimers (G proteins) consisting of a GTP-binding subunit (alpha protein) complexed with a tightly interacted heterodimer termed beta gamma. In this study we extracted the proteins from rat brain "synaptoneurosomes" using the neutral detergent 1-octyl beta-D-glucopyranoside (octyl glucoside). Using specific antibodies for detection by immunoblotting and sucrose gradients for analyzing hydrodynamic properties, we found that each species of alpha protein (alpha subunits of stimulatory, inhibitory, and brain GTP-binding proteins) exhibited a broad range (4 S to greater than 12 S) of polydisperse structures with peak values (5 S to 7 S) considerably greater than that of heterotrimeric G proteins. The beta subunit proteins, for example, appeared as a homogeneous peak at 4.4 S within which only a fraction of the total alpha proteins can be associated. Incubation of octyl glucose extracts at 30 degrees C rapidly sedimented the alpha proteins but not the beta proteins. Incubation at 30 degrees C with guanosine 5'[gamma-thio]triphosphate (10-100 microM) prevented rapid sedimentation. Hydrodynamic analysis revealed that all alpha proteins were converted to approximately 4 S structures by the actions of guanosine 5'-[gamma-thio]triphosphate without change in the hydrodynamic properties of the beta proteins. Extraction of the membranes with sodium cholate instead of octyl glucoside resulted in complete loss of the large, polydisperse structures of the alpha proteins; the S values were approximately 4 S, in the range for beta proteins. These findings suggest that the transducing GTP-binding proteins in synaptoneurosomes exist as polydisperse, possibly multimer, structures of various size that are stable in octyl glucoside but destroyed by cholate. The polydisperse structures are not associated with beta gamma complexes and are sensitive to the disaggregating effects of guanosine 5'-[gamma-thio]triphosphate.
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Affiliation(s)
- S Nakamura
- Section on Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
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Wang HY, Berrios M, Malbon CC. Localization of beta-adrenergic receptors in A431 cells in situ. Effect of chronic exposure to agonist. Biochem J 1989; 263:533-8. [PMID: 2556997 PMCID: PMC1133460 DOI: 10.1042/bj2630533] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The status of beta-adrenergic receptors was investigated in A431 cells exposed to chronic stimulation by the beta-adrenergic agonist, (-)-isoproterenol. Specific binding of beta-adrenergic antagonist (-)-[125I]iodocyanopindolol declined to 60-80% below control values within 12 h of agonist treatment. This decline in ligand binding was also observed in high-speed membrane fractions prepared from agonist-treated cells. Immunoblots probed with anti-receptor antibodies revealed both that beta-adrenergic receptors from untreated and treated cells migrated as 65,000-Mr peptides and that the cellular complement of receptor was unchanged. Indirect immunofluorescence localization of beta-adrenergic receptors was comparable in control (untreated) cells and cells challenged with (-)-isoproterenol for 1, 12, or 24 h. Thus receptor complement, migration on SDS/polyacrylamide-gel electrophoresis, and localization in situ are largely unaffected by agonist stimulation. Receptor binding of antagonist radioligands, in contrast, is markedly down-regulated in cells stimulated chronically with beta-adrenergic agonists. These data argue in favour of agonist-induced alteration(s) in the conformation of the receptor that preclude radioligand binding rather than agonist-induced receptor sequestration and/or degradation.
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Affiliation(s)
- H Y Wang
- Department of Pharmacology, State University of New York, Stony Brook 11794-8651
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