851
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Kilts JD, Gerhardt MA, Richardson MD, Sreeram G, Mackensen GB, Grocott HP, White WD, Davis RD, Newman MF, Reves JG, Schwinn DA, Kwatra MM. Beta(2)-adrenergic and several other G protein-coupled receptors in human atrial membranes activate both G(s) and G(i). Circ Res 2000; 87:705-9. [PMID: 11029407 DOI: 10.1161/01.res.87.8.705] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cardiac G protein-coupled receptors that couple to Galpha(s) and stimulate cAMP formation (eg, beta-adrenergic, histamine, serotonin, and glucagon receptors) play a key role in cardiac inotropy. Recent studies in rodent cardiac myocytes and transfected cells have revealed that one of these receptors, the beta(2)-adrenergic receptor (AR), also couples to the inhibitory G protein Galpha(i) (activation of which inhibits cAMP formation). If beta(2)ARs could be shown to couple to Galpha(i) in the human heart, it would have important ramifications, because levels of Galpha(i) increase with age and in failing human heart. Therefore, we investigated whether beta(2)ARs in the human heart activate Galpha(i). By photoaffinity labeling human atrial membranes with [(32)P]azidoanilido-GTP, followed by immunoprecipitation with antibodies specific for Galpha(i), we found that Galpha(i) is activated by stimulation of beta(2)ARs but not of beta(1)ARs. In addition, we found that other Galpha(s)-coupled receptors also couple to Galpha(i), including histamine, serotonin, and glucagon. When coupling of these receptors to Galpha(i) is disrupted by pertussis toxin, their ability to stimulate adenylyl cyclase is enhanced. These data provide the first evidence that beta(2)AR and many other Galpha(s)-coupled receptors in human atrium also couple to Galpha(i) and that abolishing the coupling of these receptors to Galpha(i) increases the receptor-mediated adenylyl cyclase activity.
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MESH Headings
- Adenylate Cyclase Toxin
- Adenylyl Cyclases/metabolism
- Adrenergic beta-1 Receptor Antagonists
- Adrenergic beta-2 Receptor Antagonists
- Adrenergic beta-Agonists/pharmacology
- Aged
- Atrial Appendage/chemistry
- Atrial Appendage/metabolism
- Cell Membrane/chemistry
- Dobutamine/pharmacology
- Ethanolamines/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Humans
- Isoproterenol/pharmacology
- Middle Aged
- Myocardial Contraction/physiology
- Pertussis Toxin
- Photoaffinity Labels
- Precipitin Tests
- Receptors, Adrenergic, beta-1/analysis
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/analysis
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Cell Surface/analysis
- Receptors, Cell Surface/metabolism
- Receptors, Glucagon/metabolism
- Receptors, Histamine/metabolism
- Receptors, Serotonin/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- J D Kilts
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
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852
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853
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Cremaschi GA, Genaro AM, Cazaux CA, Anesini C, Wald M, Borda T, Sterin-Borda L. Altered beta-adrenoceptor function associated to protein kinase C activation in hyperproliferative T lymphocytes. J Neuroimmunol 2000; 110:57-65. [PMID: 11024534 DOI: 10.1016/s0165-5728(00)00333-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
beta-Adrenoceptor (betaAR) expression and function as well as its modulation via intracellular transduction signals, were analyzed on the T cell lymphoma BW5147. Independently to the kinetic of proliferation and relative to the number of receptors displayed in normal T lymphocytes, BW5147 cells displayed a decreased number of betaAR, uncoupled to adenylate cyclase, but coupled to protein kinase C stimulation. This last effect was impaired by a beta-antagonist and by blockers of the enzymatic pathways involved in T lymphocyte proliferation, inducing a recovery of betaAR sites. Down-regulation of betaAR would implicate the loss of a negative neuroimmune control mechanism for lymphocyte proliferation. The coupling of the remaining sites to a positive signal for cellular activation, would contribute to establish an hyperproliferative state.
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Affiliation(s)
- G A Cremaschi
- Centro de Estudios Farmacológicos y Botánicos (CEFYBO), CONICET, Serrano 669, 1414, Buenos Aires, Argentina.
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854
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Houslay MD, Kolch W. Cell-Type Specific Integration of Cross-Talk between Extracellular Signal-Regulated Kinase and cAMP Signaling. Mol Pharmacol 2000. [DOI: 10.1124/mol.58.4.659] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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855
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Filardo EJ, Quinn JA, Bland KI, Frackelton AR. Estrogen-induced activation of Erk-1 and Erk-2 requires the G protein-coupled receptor homolog, GPR30, and occurs via trans-activation of the epidermal growth factor receptor through release of HB-EGF. Mol Endocrinol 2000; 14:1649-60. [PMID: 11043579 DOI: 10.1210/mend.14.10.0532] [Citation(s) in RCA: 946] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Estrogen rapidly activates the mitogen-activated protein kinases, Erk-1 and Erk-2, via an as yet unknown mechanism. Here, evidence is provided that estrogen-induced Erk-1/-2 activation occurs independently of known estrogen receptors, but requires the expression of the G protein-coupled receptor homolog, GPR30. We show that 17beta-estradiol activates Erk-1/-2 not only in MCF-7 cells, which express both estrogen receptor alpha (ER alpha) and ER beta, but also in SKBR3 breast cancer cells, which fail to express either receptor. Immunoblot analysis using GPR30 peptide antibodies showed that this estrogen response was associated with the presence of GPR30 protein in these cells. MDA-MB-231 breast cancer cells (ER alpha-, ER beta+) are GPR30 deficient and insensitive to Erk-1/-2 activation by 17beta-estradiol. Transfection of MDA-MB-231 cells with a GPR30 complementary DNA resulted in overexpression of GPR30 protein and conversion to an estrogen-responsive phenotype. In addition, GPR30-dependent Erk-1/-2 activation was triggered by ER antagonists, including ICI 182,780, yet not by 17alpha-estradiol or progesterone. Consistent with acting through a G protein-coupled receptor, estradiol signaling to Erk-1/-2 occurred via a Gbetagamma-dependent, pertussis toxin-sensitive pathway that required Src-related tyrosine kinase activity and tyrosine phosphorylation of tyrosine 317 of the Shc adapter protein. Reinforcing this idea, estradiol signaling to Erk-1/-2 was dependent upon trans-activation of the epidermal growth factor (EGF) receptor via release of heparan-bound EGF (HB-EGF). Estradiol signaling to Erk-1/-2 could be blocked by: 1) inhibiting EGF-receptor tyrosine kinase activity, 2) neutralizing HB-EGF with antibodies, or 3) down-modulating HB-EGF from the cell surface with the diphtheria toxin mutant, CRM-197. Our data imply that ER-negative breast tumors that continue to express GPR30 may use estrogen to drive growth factor-dependent cellular responses.
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Affiliation(s)
- E J Filardo
- Department of Medicine and Surgery, Rhode Island Hospital and Brown University, Providence 02903, USA.
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856
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Gong H, Adamson DL, Ranu HK, Koch WJ, Heubach JF, Ravens U, Zolk O, Harding SE. The effect of Gi-protein inactivation on basal, and beta(1)- and beta(2)AR-stimulated contraction of myocytes from transgenic mice overexpressing the beta(2)-adrenoceptor. Br J Pharmacol 2000; 131:594-600. [PMID: 11015312 PMCID: PMC1572349 DOI: 10.1038/sj.bjp.0703591] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The atria and ventricles of transgenic mice (TGbeta(2)) with cardiac overexpression of the human beta(2)-adrenoceptor (beta(2)AR) were initially reported to show maximum contractility in the absence of beta-AR stimulation. However, we have previously observed a different phenotype in these mice, with myocytes showing normal contractility but reduced betaAR responses. We have investigated the roles of cyclic AMP and Gi in basal and betaAR function in these myocytes. ICI 118,551 at inverse agonist concentrations decreased contraction by 32%. However, the cyclic AMP antagonist Rp-cAMPS had no effect on contraction in TGbeta(2) myocytes, indicating that there was no tonic influence of raised cyclic AMP. These findings cannot be explained by the proposed model for inverse agonism, where the activated receptor (R*) raises cyclic AMP levels and so increases contraction in the absence of agonist. After pertussis toxin (PTX) pretreatment to produce inactivation of Gi, the basal contraction in 1 mM Ca(2+) was increased in TGbeta(2) mice (7.82+/-0.47%, n=23) compared to LM mice (3.60+/-0.59%, n=11) (P<0.001). The contraction amplitude of myocytes to the maximal concentration of isoprenaline was also increased significantly by PTX in TGbeta(2) mice (9.40+/-1.22%, n=8) and was no longer reduced compared to LM mice (8.93+/-1.50%, n=11). Both beta(1)- and beta(2)AR subtypes were affected both by the original desensitization and by the resensitization with PTX. PTX treatment has therefore restored the original phenotype, with high basal contractility and little further effect of isoprenaline. We suggest that both beta-AR desensitization and lack of increased basal contraction in ventricular myocytes from our colony of TGbeta(2) mice were due to increased activity of PTX-sensitive G-proteins.
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MESH Headings
- Animals
- Calcium/pharmacology
- Cyclic AMP/metabolism
- GTP-Binding Protein alpha Subunits, Gi-Go/physiology
- Heart Ventricles/cytology
- Humans
- In Vitro Techniques
- Isoproterenol/pharmacology
- Mice
- Mice, Transgenic
- Myocardial Contraction/physiology
- Pertussis Toxin
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/biosynthesis
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/physiology
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- Haibin Gong
- National Heart and Lung Institute, Imperial College School of Medicine, London
| | - Dawn L Adamson
- National Heart and Lung Institute, Imperial College School of Medicine, London
| | - Hardeep K Ranu
- National Heart and Lung Institute, Imperial College School of Medicine, London
| | - Walter J Koch
- Institute of Pharmacology and Toxicology, Dresden University of Technology, Germany
| | - Jürgen F Heubach
- Department of Experimental Surgery, Duke University Medical Center Durham, North Carolina, U.S.A
| | - Ursula Ravens
- Department of Experimental Surgery, Duke University Medical Center Durham, North Carolina, U.S.A
| | - Oliver Zolk
- Institute of Pharmacology, University of Erlangen, Germany
| | - Sian E Harding
- National Heart and Lung Institute, Imperial College School of Medicine, London
- Author for correspondence:
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857
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Murthy KS, Grider JR, Makhlouf GM. Heterologous desensitization of response mediated by selective PKC-dependent phosphorylation of G(i-1) and G(i-2). Am J Physiol Cell Physiol 2000; 279:C925-34. [PMID: 11003572 DOI: 10.1152/ajpcell.2000.279.4.c925] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the ability of protein kinase C (PKC) to induce heterologous desensitization by targeting specific G proteins and limiting their ability to transduce signals in smooth muscle. Activation of PKC by pretreatment of intestinal smooth muscle cells with phorbol 12-myristate 13-acetate, cholecystokinin octapeptide, or the phosphatase 1 and phosphatase 2A inhibitor, calyculin A, selectively phosphorylated Galpha(i-1) and Galpha(i-2), but not Galpha(i-3) or Galpha(o), and blocked inhibition of adenylyl cyclase mediated by somatostatin receptors coupled to G(i-1) and opioid receptors coupled to G(i-2), but not by muscarinic M(2) and adenosine A(1) receptors coupled to G(i-3). Phosphorylation of Galpha(i-1) and Galpha(i-2) and blockade of cyclase inhibition were reversed by calphostin C and bisindolylmaleimide, and additively by selective inhibitors of PKCalpha and PKCepsilon. Blockade of inhibition was prevented by downregulation of PKC. Phosphorylation of Galpha-subunits by PKC also affected responses mediated by betagamma-subunits. Pretreatment of muscle cells with cANP-(4-23), a selective agonist of the natriuretic peptide clearance receptor, NPR-C, which activates phospholipase C (PLC)-beta3 via the betagamma-subunits of G(i-1) and G(i-2), inhibited the PLC-beta response to somatostatin and [D-Pen(2,5)]enkephalin. The inhibition was partly reversed by calphostin C. Short-term activation of PKC had no effect on receptor binding or effector enzyme (adenylyl cyclase or PLC-beta) activity. We conclude that selective phosphorylation of Galpha(i-1) and Galpha(i-2) by PKC partly accounts for heterologous desensitization of responses mediated by the alpha- and betagamma-subunits of both G proteins. The desensitization reflects a decrease in reassociation and thus availability of heterotrimeric G proteins.
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MESH Headings
- Adenylyl Cyclase Inhibitors
- Adenylyl Cyclases/metabolism
- Animals
- Blotting, Western
- Cells, Cultured
- Colforsin/pharmacology
- Cyclic AMP/metabolism
- Dose-Response Relationship, Drug
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Enzyme Inhibitors/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/agonists
- GTP-Binding Protein alpha Subunits, Gi-Go/antagonists & inhibitors
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Hormones/pharmacology
- Isoenzymes/antagonists & inhibitors
- Isoenzymes/metabolism
- Muscle, Smooth/cytology
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Naphthalenes/pharmacology
- Phospholipase C beta
- Phosphoric Monoester Hydrolases/antagonists & inhibitors
- Phosphorylation/drug effects
- Precipitin Tests
- Protein Isoforms/metabolism
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Rabbits
- Signal Transduction/drug effects
- Sincalide/pharmacology
- Tetradecanoylphorbol Acetate/pharmacology
- Type C Phospholipases/metabolism
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Affiliation(s)
- K S Murthy
- Departments of Medicine and Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298-0711, USA
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858
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DeFea KA, Vaughn ZD, O'Bryan EM, Nishijima D, Déry O, Bunnett NW. The proliferative and antiapoptotic effects of substance P are facilitated by formation of a beta -arrestin-dependent scaffolding complex. Proc Natl Acad Sci U S A 2000; 97:11086-91. [PMID: 10995467 PMCID: PMC27152 DOI: 10.1073/pnas.190276697] [Citation(s) in RCA: 332] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A requirement for scaffolding complexes containing internalized G protein-coupled receptors and beta-arrestins in the activation and subcellular localization of extracellular signal-regulated kinases 1 and 2 (ERK1/2) has recently been proposed. However, the composition of these complexes and the importance of this requirement for function of ERK1/2 appear to differ between receptors. Here we report that substance P (SP) activation of neurokinin-1 receptor (NK1R) stimulates the formation of a scaffolding complex comprising internalized receptor, beta-arrestin, src, and ERK1/2 (detected by gel filtration, immunoprecipitation, and immunofluorescence). Inhibition of complex formation, by expression of dominant-negative beta-arrestin or a truncated NK1R that fails to interact with beta-arrestin, inhibits both SP-stimulated endocytosis of the NK1R and activation of ERK1/2, which is required for the proliferative and antiapoptotic effects of SP. Thus, formation of a beta-arrestin-containing complex facilitates the proliferative and antiapoptotic effects of SP, and these effects of SP could be diminished in cells expressing truncated NK1R corresponding to a naturally occurring variant.
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Affiliation(s)
- K A DeFea
- Department of Surgery, University of California, San Francisco, 521 Parnassus Avenue, San Francisco, CA 94143-0660, USA
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859
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Koch WJ, Lefkowitz RJ, Rockman HA. Functional consequences of altering myocardial adrenergic receptor signaling. Annu Rev Physiol 2000; 62:237-60. [PMID: 10845091 DOI: 10.1146/annurev.physiol.62.1.237] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
From the ability to successfully manipulate the mouse genome has come important transgenic and gene-targeted knockout models that impact many areas of biomedical research. Genetically engineered mouse models geared toward the study of cardiovascular regulation have recently been described and provide powerful tools to study normal and compromised cardiac physiology. The genetic manipulation of the adrenergic receptor (AR) signaling system in the heart, including its regulation by desensitizing kinases, has shed light on the role of this signaling pathway in the regulation of cardiac contractility. One major finding, supported by several mouse models, is that in vivo contractility can be enhanced via alteration of myocardial AR signaling. Thus genetic manipulation of this critical receptor system in the heart represents a novel therapeutic approach for improving function of the failing heart.
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Affiliation(s)
- W J Koch
- Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA.
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860
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Nagykaldi Z, Kem D, Lazzara R, Szabo B. Conditioning of beta(1)-adrenoceptor effect via beta(2)-subtype on L-type Ca(2+) current in canine ventricular myocytes. Am J Physiol Heart Circ Physiol 2000; 279:H1329-37. [PMID: 10993800 DOI: 10.1152/ajpheart.2000.279.3.h1329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the roles of beta(1)- and beta(2)-receptors (beta-AR) in adrenergic enhancement of L-type Ca(2+) current (I(CaL)) in canine ventricular myocytes. Isoproterenol and l-norepinephrine produced a monophasic and a biphasic concentration-I(CaL) relationship (CR), respectively. alpha(1)-AR inhibition with prazosin and beta(2)-AR stimulation with zinterol or l-epinephrine shifted the CR of l-norepinephrine leftward. Zinterol (50 nM) and l-epinephrine (10 nM), but not prazosin, altered the biphasic CR of l-norepinephrine to a monophasic CR. Zinterol and l-epinephrine applied after l-norepinephrine had no effect on I(CaL). beta(2)-AR inhibition with ICI-118551 reduced the E(max) of isoproterenol and l-norepinephrine by 60% and abolished the augmentation of l-norepinephrine by zinterol and l-epinephrine. Carbachol (100 nM) modestly reduced the I(CaL) response to beta(1)-AR stimulation but abolished the enhancement via beta(2)-AR. Zinterol augmented the enhancement of I(CaL) by forskolin, IBMX, and theophylline, but not in the presence of CGP-20712A. We conclude that selective beta(2)-AR stimulation does not increase I(CaL) but enhances adenylyl cyclase activity when stimulated via beta(1)-AR and with forskolin. beta(2)-AR activity preconditions adenylyl cyclase for beta(1)-AR stimulation.
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Affiliation(s)
- Z Nagykaldi
- Section of Endocrinology, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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861
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Schmitt JM, Stork PJ. beta 2-adrenergic receptor activates extracellular signal-regulated kinases (ERKs) via the small G protein rap1 and the serine/threonine kinase B-Raf. J Biol Chem 2000; 275:25342-50. [PMID: 10840035 DOI: 10.1074/jbc.m003213200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors can induce cellular proliferation by stimulating the mitogen-activated protein (MAP) kinase cascade. Heterotrimeric G proteins are composed of both alpha and betagamma subunits that can signal independently to diverse intracellular signaling pathways including those that activate MAP kinases. In this study, we examined the ability of isoproterenol, an agonist of the beta(2)-adrenergic receptor (beta(2)AR), to stimulate extracellular signal-regulated kinases (ERKs). Using HEK293 cells, which express endogenous beta(2)AR, we show that isoproterenol stimulates ERKs via beta(2)AR. This action of isoproterenol requires cAMP-dependent protein kinase and is insensitive to pertussis toxin, suggesting that Galpha(s) activation of cAMP-dependent protein kinase is required. Interestingly, beta(2)AR activates both the small G proteins Rap1 and Ras, but only Rap1 is capable of coupling to Raf isoforms. beta(2)AR inhibits the Ras-dependent activation of both Raf isoforms Raf-1 and B-Raf, whereas Rap1 activation by isoproterenol recruits and activates B-Raf. beta(2)AR activation of ERKs is not blocked by expression of RasN17, an interfering mutant of Ras, but is blocked by expression of either RapN17 or Rap1GAP1, both of which interfere with Rap1 signaling. We propose that isoproterenol can activate ERKs via Rap1 and B-Raf in these cells.
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Affiliation(s)
- J M Schmitt
- Vollum Institute and the Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland 97201, USA
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862
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Abstract
Several lines of evidence show that neurohumoral systems, especially those involving catecholamines, play a crucial role in cardiac diseases. Changes in the beta-adrenergic receptor (beta-AR) system such as receptor down-regulation, uncoupling from G-proteins, receptor internalization and receptor degradation may account for some of the abnormalities of contractile function in this disease. Increases in the level of inhibitory G-protein subunits also appears to be involved in attenuating the beta-AR signal. Finally beta-AR signalling is strongly regulated by members of the G-protein-coupled receptor kinase family (GRKs), the best known of which is beta-adrenergic receptor kinase 1 (beta-ARK1). beta-ARK1 mRNA, protein level and enzymatic activity is increased in heart disease, further contributing to an attenuation in beta-AR signalling. The combination of these negative alterations are presumably related to the contractile dysfunction seen in human heart disease. The combination of biochemical, physiological and molecular biological studies bearing on the normal function and regulation of these various molecules should provide strategies for elucidating the pharmacological basis of the regulation of myocardial contractility in the normal and failing heart.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Aging
- Animals
- Calcium/metabolism
- Cyclic AMP-Dependent Protein Kinases/chemistry
- Cytoskeleton/metabolism
- Ethanol/pharmacology
- Heart/drug effects
- Heart/physiology
- Heart Diseases/enzymology
- Heart Diseases/metabolism
- Heart Diseases/therapy
- Humans
- Mice
- Mice, Transgenic
- Models, Biological
- Myocardium/enzymology
- Myocardium/metabolism
- Oxidants/physiology
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta/physiology
- Signal Transduction
- beta-Adrenergic Receptor Kinases
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Affiliation(s)
- S Chakraborti
- Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India
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863
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Lindquist JM, Fredriksson JM, Rehnmark S, Cannon B, Nedergaard J. Beta 3- and alpha1-adrenergic Erk1/2 activation is Src- but not Gi-mediated in Brown adipocytes. J Biol Chem 2000; 275:22670-7. [PMID: 10770951 DOI: 10.1074/jbc.m909093199] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel signaling pathway for mediation of beta(3)-adrenergic activation of the mitogen-activated protein kinases Erk1/2 (associated with proliferation, differentiation, and apoptosis) has recently been proposed, which implies mediation via constitutively coupled G(i)-proteins and Gbetagamma-subunits, distinct from the classical cAMP pathway of beta-adrenergic stimulation. To verify the significance of this pathway in cells in primary cultures that entopically express beta(3)-adrenoreceptors, we examined the functionality of this pathway in cultured brown adipocytes. Norepinephrine activated Erk1/2 via both beta(3) receptors and alpha(1) receptors but not via alpha(2) receptors. Forskolin induced Erk1/2 activation similarly to beta(3) activation, indicating cAMP-mediation; this induction could be inhibited with H89, implying protein kinase A mediation. The G(i)-pathway was functional in these cells, as pertussis toxin increased agonist-induced cAMP accumulation. However, pertussis toxin was unable to affect adrenergically induced Erk1/2 activation. Also, wortmannin was without effect, implying that Gbetagamma activation of the phosphatidylinositol 3-kinase pathway was not involved. PP1/2, which inhibits Src, abolished both beta(3)- and alpha(1)-induced Erk1/2 activation. Thus, the proposed novel G(i) pathway for beta(3) mediation is not universal, because it is not functional in the untransformed primary cell culture system with entopically expressed beta(3) receptors examined here. Here, the beta(3) signal is mediated classically via cAMP/protein kinase A. beta(3) and alpha(1) signals converge at Src, which thus mediates Erk1/2 activation in both pathways.
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Affiliation(s)
- J M Lindquist
- Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden.
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864
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Abstract
In addition to protein kinase A (PKA), cAMP regulates the activity of cAMP-gated channels and Rap1-specific guanine nucleotide exchange factors. We tested the hypothesis that the targets of cAMP might also include regulators of the Ras protooncogene. In rat thyroid cells, thyrotropin (TSH) stimulates proliferation through a cAMP-mediated pathway that requires Ras activity. Interference with Ras impairs DNA synthesis stimulated by TSH as well as cAMP elevating agents and analogs, demonstrating that the requirement for Ras lies down-stream of cAMP. Although cAMP stimulates proliferation, microinjection of the purified PKA catalytic subunit failed to do so, suggesting that factors in addition to PKA are required for cAMP-stimulated cell cycle progression. When added to thyroid cells expressing human Ha-Ras, TSH rapidly and markedly increased the proportion of GTP-bound Ras. Ras activity was increased within 1 min of TSH addition, maximal at 5-15 min, and declined to basal levels 30-60 min after hormone treatment. Cyclic AMP elevating agents elicited similar effects on Ras, indicating that TSH activates Ras through a cAMP-mediated pathway. Although cAMP-mediated, Ras activation by TSH and cAMP was independent of PKA activity. Moreover, cAMP-stimulated Ras activation was not impaired by tyrosine kinase inhibitors. These results indicate that cAMP activates targets in addition to PKA in thyroid cells, and that these targets may include regulators of Ras. The ability of cAMP elevating agents to activate Ras in addition to PKA may explain the inability of the PKA catalytic subunit to stimulate DNA synthesis in thyroid cells.
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Affiliation(s)
- O M Tsygankova
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6084, USA
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865
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Zaugg M, Xu W, Lucchinetti E, Shafiq SA, Jamali NZ, Siddiqui MA. Beta-adrenergic receptor subtypes differentially affect apoptosis in adult rat ventricular myocytes. Circulation 2000; 102:344-50. [PMID: 10899100 DOI: 10.1161/01.cir.102.3.344] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND-Catecholamine-induced apoptosis is mediated by activation of the beta-adrenergic signaling pathway. We tested the hypothesis that beta(1)- and beta(2)-adrenergic receptor (AR) subtypes differentially affect apoptosis in adult rat ventricular myocytes in vitro. METHODS AND RESULTS-Myocytes were first exposed to norepinephrine (NE) alone (10 mcmol/L) or NE+atenolol (AT) (10 mcmol/L) for 12 hours. AT, a beta(1)-selective AR antagonist, abolished the NE-induced increase in nick end-labeling (TUNEL)-positive cells compared with control (NE, 33+/-3% versus control, 3+/-1%, P<0.0001; NE+AT, 4+/-2% versus control, 3+/-1%, P=0. 98). Annexin V staining, DNA laddering, and caspase activity determinations corroborated these results. Subsequent experiments under prazosin treatment established the apoptosis dose-response curves for the increasingly beta(2)-selective AR agonists isoproterenol (ISO) (beta(1) approximately beta(2)) and albuterol (ALB) (beta(2)>beta(1)). ISO and ALB induced significantly less apoptosis than NE (beta(1)>beta(2)) at equimolar concentrations as assessed by TUNEL staining [1 mcmol/L: NE (8+/-2%) approximately ISO (7+/-1%)>ALB (2+/-1%); 10 mcmol/L: NE (35+/-2%)>ISO (23+/-1%)>ALB (3+/-1%); 100 mcmol/L: NE (50+/-2%)>ISO (29+/-2%)>ALB (14+/-1%), P<0.0001 except for NE versus ISO at 1 mcmol/L with P=0.62]. ALB-induced apoptosis at 100 mcmol/L was abolished by AT (10 mcmol/L), indicating a beta(1)AR-mediated effect. Importantly, ICI 118551 (0.1 mcmol/L), a highly selective beta(2)AR antagonist, did not decrease the percentage of NE-, ISO-, and ALB-induced apoptosis. Reverse transcription-polymerase chain reaction studies revealed that AT completely reversed the beta-adrenergic signaling-induced changes in the Bcl-2-to-Bax ratio. CONCLUSIONS-These observations provide evidence that beta AR-mediated apoptotic death signaling is largely dissociated from beta(2)ARs and selectively mediated by beta(1)ARs in adult rat ventricular myocytes.
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Affiliation(s)
- M Zaugg
- Department of Anesthesiology, Health Science Center at Brooklyn, State University of New York, USA
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866
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Le Péchon-Vallée C, Magalon K, Rasolonjanahary R, Enjalbert A, Gérard C. Vasoactive intestinal polypeptide and pituitary adenylate cyclase-activating polypeptides stimulate mitogen-activated protein kinase in the pituitary cell line GH4C1 by a 3',5'-cyclic adenosine monophosphate pathway. Neuroendocrinology 2000; 72:46-56. [PMID: 10940738 DOI: 10.1159/000054570] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP38) regulate anterior pituitary cell secretion and proliferation. In the somatolactotrope GH4C1 cell line, these effects are mediated through the type-II-like PACAP receptor (VPAC2) coupled to the cAMP pathway. In this study, the control of the extracellularly responsive kinases (ERKs) by VIP and PACAP38 was investigated in GH4C1 cells. VIP and PACAP38 increased ERK1 and ERK2 phosphorylation and were equipotent stimulators of both kinases. ERK activation was mimicked by cholera toxin, forskolin and 8bromo-cAMP. VIP and PACAP38 activation of ERK2 was blocked by the protein kinase A inhibitor H89, whereas the protein kinase C inhibitor GF109203X, or prior PMA-induced depletion of the protein kinases C, failed to inhibit VIP and PACAP38 activation of ERK2. In contrast, thyrotropin-releasing hormone (TRH) elicited ERK activation by a PKC-dependent process. ERK activation by VIP or PACAP38 and TRH were additive and both sensitive to the MEK inhibitors PD98059 and U0126. In parallel, U0126 reduced prolactin (PRL) mRNA levels induced by VIP. These results demonstrate for the first time that VIP and PACAP38 activate ERK in GH4C1 cells. Cyclic AMP increase is sufficient to elicit ERK activation in these cells and thus likely to represent the transduction pathway underlying VIP- and PACAP38-dependent ERK activation. This mechanism seems to be involved in VIP-induced PRL gene regulation.
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Affiliation(s)
- C Le Péchon-Vallée
- Interactions Cellulaires Neuroendocriniennes, UMR 6544 CNRS, IFR Jean Roche, Université de la Méditerranée, Marseille, France.
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867
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Adamson DL, Money-Kyrle AR, Harding SE. Functional evidence for a cyclic-AMP related mechanism of action of the beta(2)-adrenoceptor in human ventricular myocytes. J Mol Cell Cardiol 2000; 32:1353-60. [PMID: 10860775 DOI: 10.1006/jmcc.2000.1171] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human ventricle contains both beta(1)- and beta(1)-adrenoceptors (AR) and both have been shown to be present on a single myocyte. In animal ventricular myocardium there is evidence that beta(1)ARs increase cardiac contraction by non-cAMP-dependent mechanisms. We have used the anti-adrenergic effects of carbachol and the cAMP antagonist Rp -cAMPS to investigate the functional contribution of cAMP to beta(2)AR responses in human ventricular myocytes isolated from cardiac biopsies or explants. Concentration-response curves to isoproterenol (Iso) were constructed in the absence and presence of a beta(1)AR antagonist, CGP 207 12A (300 nmol/l) to determine the contribution of the beta(2)AR to contraction. The cells were rechallenged with sub-maximal dose of Iso under beta(2)AR-specific conditions and Rp -cAMPS (100-200 micromol/l) or carbachol (1-3 microm/l) added. Rp -cAMPS significantly decreased contraction amplitude (% shortening; Iso 7.1+/-0.7, Iso+Rp -cAMPS 3.5+/-0.5, n=7, P<0.001) though not completely to the baseline (2.2+/-0.6, n=7). Rechallenge with Iso alone reversed the effects of Rp -cAMPS, and subsequent addition of the beta(1)AR antagonist ICI 118,551 reduced the response to baseline (1.6+/-0.3, n=4) confirming beta(2)AR involvement. Similarly, carbachol decreased Iso-stimulated contraction from 7.5+/-1.2% to 3.2+/-0.9% (P<0.05, n=4), but not completely to basal levels (1.6+/-0.3%). These results provide functional evidence for a predominantly cAMP-mediated mechanism of contractile stimulation by beta(1)ARs in human ventricular myocardium, although a small contribution from a non-cAMP dependent pathway may occur.
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Affiliation(s)
- D L Adamson
- NHLI, Imperial College School of Medicine, Dovehouse Street, London, SW3 6LY.
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868
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Budd DC, McDonald JE, Tobin AB. Phosphorylation and regulation of a Gq/11-coupled receptor by casein kinase 1alpha. J Biol Chem 2000; 275:19667-75. [PMID: 10777483 DOI: 10.1074/jbc.m000492200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agonist-mediated receptor phosphorylation by one or more of the members of the G-protein receptor kinase (GRK) family is an established model for G-protein-coupled receptor (GPCR) phosphorylation resulting in receptor desensitization. Our recent studies have, however, suggested that an alternative route to GPCR phosphorylation may be an operation involving casein kinase 1alpha (CK1alpha). In the current study we investigate the involvement of CK1alpha in the phosphorylation of the human m3-muscarinic receptor in intact cells. We show that expression of a catalytically inactive mutant of CK1alpha, designed to act in a dominant negative manner, inhibits agonist-mediated receptor phosphorylation by approximately 40% in COS-7 and HEK-293 cells. Furthermore, we present evidence that a peptide corresponding to the third intracellular loop of the m3-muscarinic receptor (Ser(345)-Leu(463)) is an inhibitor of CK1alpha due to its ability to both act as a pseudo-substrate for CK1alpha and form a high affinity complex with CK1alpha. Expression of this peptide was able to reduce both basal and agonist-mediated m3-muscarinic receptor phosphorylation in intact cells. These results support the notion that CK1alpha is able to mediate GPCR phosphorylation in an agonist-dependent manner and that this may provide a novel mechanism for GPCR phosphorylation. The functional role of phosphorylation was investigated using a mutant of the m3-muscarinic receptor that showed an approximately 80% reduction in agonist-mediated phosphorylation. Surprisingly, this mutant underwent agonist-mediated desensitization suggesting that, unlike many GPCRs, desensitization of the m3-muscarinic receptor is not mediated by receptor phosphorylation. The inositol (1,4, 5)-trisphosphate response did, however, appear to be dramatically potentiated in the phosphorylation-deficient mutant indicating that phosphorylation may instead control the magnitude of the initial inositol phosphate response.
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Affiliation(s)
- D C Budd
- Department of Cell Physiology and Pharmacology, University of Leicester, P. O. Box 138, Medical Sciences Building, University Road, Leicester LE1 9HN, United Kingdom
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869
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Communal C, Colucci WS, Singh K. p38 mitogen-activated protein kinase pathway protects adult rat ventricular myocytes against beta -adrenergic receptor-stimulated apoptosis. Evidence for Gi-dependent activation. J Biol Chem 2000; 275:19395-400. [PMID: 10770956 DOI: 10.1074/jbc.m910471199] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown that stimulation of beta-adrenergic receptors (beta-AR) by norepinephrine (NE) increases apoptosis in adult rat ventricular myocytes (ARVMs) via a cAMP-dependent mechanism that is antagonized by activation of G(i) protein. The family of mitogen-activated protein kinases (MAPKs) is involved in the regulation of cardiac myocyte growth and apoptosis. Here we show that beta-AR stimulation activates p38 kinase, c-jun N-terminal kinases (JNKs), and extracellular signal-regulated kinase (ERK1/2) in ARVMs. Inhibition of p38 kinase with SB-202190 (10 micrometer) potentiated beta-AR-stimulated apoptosis as measured by flow cytometry and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. SB-202190 at this concentration specifically blocked beta-AR-stimulated activation of p38 kinase and its downstream substrate MAPK-activated protein kinase-2 (MAPKAPK2). Pertussis toxin, an inhibitor of G(i)/G(o) proteins, blocked the activation of p38 kinase and potentiated beta-AR-stimulated apoptosis. Activation of G(i) protein with the muscarinic receptor agonist carbachol protected against beta-AR-stimulated apoptosis. Carbachol also activated p38 kinase, and the protective effect of carbachol was abolished by SB-202190. PD-98059 (10 micrometer), an inhibitor of ERK1/2 pathway, blocked beta-AR-stimulated activation of ERK1/2 but had no effect on apoptosis. These data suggest that 1) beta-AR stimulation activates p38 kinase, JNKs, and ERK1/2; 2) activation of p38 kinase plays a protective role in beta-AR-stimulated apoptosis in cardiac myocytes; and 3) the protective effects of G(i) are mediated via the activation of p38 kinase.
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Affiliation(s)
- C Communal
- Myocardial Biology Unit and Cardiovascular Division, Boston University Medical Center, Boston Veterans Affairs Medical Center and Boston University School of Medicine, Massachusetts 02118, USA
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870
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Ranu HK, Mak JC, Barnes PJ, Harding SE. G(i)-dependent suppression of beta(1)-adrenoceptor effects in ventricular myocytes from NE-treated guinea pigs. Am J Physiol Heart Circ Physiol 2000; 278:H1807-14. [PMID: 10843876 DOI: 10.1152/ajpheart.2000.278.6.h1807] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been suggested that there is a preferential coupling in heart muscle between the inhibitory G protein (G(i)) and the beta(2)-subtype of the beta-adrenergic receptor (beta-AR), since pertussis toxin (which inactivates G(i)) reveals latent beta(2)-ARs in rat and mouse myocytes. We have previously shown that guinea pigs treated with norepinephrine (NE) for 7 days have myocytes that are desensitized to beta-AR-agonist stimulation, and that pertussis toxin restores these responses. The purpose of the present investigation was to determine whether pertussis toxin specifically upregulated beta(2)-ARs in myocytes from NE-treated guinea pigs. The sole beta-AR subtype in control guinea pig myocytes was confirmed as beta(1)-AR by radioligand binding, single-cell autoradiography, and concentration-response curves to isoproterenol in contracting myocytes. In contrast, a minor pool of beta(2)-ARs was observed in rat myocytes by use of the same methods. NE treatment decreased the maximum isoproterenol response (relative to high Ca(2+)) from 0.89 +/- 0.06 to 0.58 +/- 0.08 (n = 7, P < 0.01) and the pD(2) (-log EC(50)) from 8.8 +/- 0.2 to 7.5 +/- 0.2 (n = 7, P < 0.01). Pertussis toxin treatment increased the isoproterenol-to-Ca(2+) ratio to 0.88 +/- 0.04 (n = 6, P < 0.05) and the pD(2) to 8.6 +/- 0.3 (P < 0.01). This was not mediated by increases in either number or function of beta(2)-ARs. G(i) is therefore able to modulate beta(1)-AR responses in guinea pig myocytes.
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Affiliation(s)
- H K Ranu
- Cardiac Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London, United Kingdom
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871
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Disa J, Parameswaran N, Nambi P, Aiyar N. Involvement of cAMP-dependent protein kinase and pertussis toxin-sensitive G-proteins in CGRP mediated JNK activation in human neuroblastoma cell line. Neuropeptides 2000; 34:229-33. [PMID: 11021985 DOI: 10.1054/npep.2000.0810] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Calcitonin gene-related peptide (CGRP) is a neuropeptide with potent cardiovascular effects, which include positive inotropic and chronotropic actions, systemic vasodilation, and hypotension in animal and human studies. Human neuroblastoma cells (SK-N-MC) have been used as a model system to study the CGRP receptors and downstream signaling pathways. This investigation was undertaken to study the role of CGRP in the activation of mitogen-activated protein kinases. While exposure of these cells to CGRP had no significant effect on ERK-1 or p38 MAP kinases, JNK activity was stimulated by CGRP in a time- and concentration-dependent fashion. CGRP-mediated JNK-activation was inhibited by CGRP receptor antagonist, CGRP8-37, confirming that this is a receptor-mediated event. In addition, pretreatment of the cells with H-89, protein kinase A inhibitor or pertussis toxin greatly attenuated CGRP-mediated JNK activation suggesting the requirement of cAMP-dependent protein kinase activation and involvement of pertussis toxin-sensitive G-protein in CGRP-mediated JNK activation.
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Affiliation(s)
- J Disa
- Department of Pharmacology, SmithKline Beecham Pharmaceuticals, 709 Swedeland Road, King of Prussia, PA 19406-0939, USA
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872
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Werstiuk ES, Lee RMKW. Vascular β-adrenoceptor function in hypertension and in ageing. Can J Physiol Pharmacol 2000. [DOI: 10.1139/y00-015] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functional β-adrenoceptors (β-AR) have been identified and characterized in blood vessels under in vivo conditions as well as in vascular smooth muscle cells (SMC) grown in culture. Agonist occupancy of β-AR activates adenylyl cyclase (AC) via the stimulatory guanine nucleotide-binding protein (Gs) and leads to elevations in intracellular adenosine 3',5'-cyclic monophosphate levels (cAMP). Increased cAMP activates the cAMP-dependent protein kinase (PKA), with subsequent phosphorylation of various target proteins. This β-AR pathway interacts with several other intracellular signalling pathways via cross-talk, so that activation by β-AR agonists may also modulate other second messengers and protein kinases. SMC β-AR play an important role in SMC function. In intact blood vessels they mediate SMC relaxation by various intracellular mechanisms, ultimately causing a decrease in intracellular Ca2+ levels. In cultured SMC, activation of the β-AR pathway results in inhibition of cellular proliferation, the development of SMC polyploidy, and SMC apoptosis. Blood vessels from hypertensive animals are characterized by an increase in SMC cell mass, a greater incidence of SMC polyploidy in the aorta, and an impairment in the β-agonist-mediated SMC relaxation. Some of these changes may result from an attenuation of β-AR function due to agonist-induced receptor desensitization caused by the uncoupling of receptors from the Gs-AC system. The phosphorylated β-AR may in turn trigger new signals and activate different intracellular pathways. However, the details of these mechanisms are still unresolved. Since functional β-AR play such a prominent and multi-faceted role in SMC function, it is important to understand how these diverse physiological effects are mediated by this receptor system, and how they contribute to the development of hypertension. With ageing, a decrease in β-AR-Gs-AC coupling is observed, and this is implicated in the reduced responsiveness of SMC. The similarities in SMC β-AR functional changes in hypertension and in ageing suggest that the underlying mechanisms are also analogous.Key words: smooth muscle, β-adrenoceptors, cyclic AMP, protein kinase A, cell proliferation, polyploidy, relaxation, apoptosis, hypertension, ageing.
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873
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He Q, Wu G, Lapointe MC. Isoproterenol and cAMP regulation of the human brain natriuretic peptide gene involves Src and Rac. Am J Physiol Endocrinol Metab 2000; 278:E1115-23. [PMID: 10827015 DOI: 10.1152/ajpendo.2000.278.6.e1115] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Brain natriuretic peptide (BNP) gene expression and chronic activation of the sympathetic nervous system are characteristics of the development of heart failure. We studied the role of the beta-adrenergic signaling pathway in regulation of the human BNP (hBNP) promoter. An hBNP promoter (-1818 to +100) coupled to a luciferase reporter gene was transferred into neonatal cardiac myocytes, and luciferase activity was measured as an index of promoter activity. Isoproterenol (ISO), forskolin, and cAMP stimulated the promoter, and the beta(2)-antagonist ICI 118,551 abrogated the effect of ISO. In contrast, the protein kinase A (PKA) inhibitor H-89 failed to block the action of cAMP and ISO. Pertussis toxin (PT), which inactivates Galpha(i), inhibited ISO- and cAMP-stimulated hBNP promoter activity. The Src tyrosine kinase inhibitor PP1 and a dominant-negative mutant of the small G protein Rac also abolished the effect of ISO and cAMP. Finally, we studied the involvement of M-CAT-like binding sites in basal and inducible regulation of the hBNP promoter. Mutation of these elements decreased basal and cAMP-induced activity. These data suggest that beta-adrenergic regulation of hBNP is PKA independent, involves a Galpha(i)-activated pathway, and targets regulatory elements in the proximal BNP promoter.
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Affiliation(s)
- Q He
- Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, Michigan 48202, USA
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874
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Francesconi A, Duvoisin RM. Opposing effects of protein kinase C and protein kinase A on metabotropic glutamate receptor signaling: selective desensitization of the inositol trisphosphate/Ca2+ pathway by phosphorylation of the receptor-G protein-coupling domain. Proc Natl Acad Sci U S A 2000; 97:6185-90. [PMID: 10823959 PMCID: PMC18579 DOI: 10.1073/pnas.97.11.6185] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Signaling by the metabotropic glutamate receptor 1alpha (mGluR1alpha) can lead to the accumulation of inositol 1,4, 5-trisphosphate (InsP(3)) and cAMP and to the modulation of K(+) and Ca(2+) channel opening. At present, very little is known about how these different actions are integrated and eventually turned off. Unraveling the molecular mechanisms underlying these functions is crucial for understanding mGluR-mediated regulation of synaptic transmission. It has been shown that receptor-induced activation of the InsP(3) pathway is subject to feedback inhibition mediated by protein kinase C (PKC). In this study, we provide evidence for a differential regulation by PKC and protein kinase A of two distinct mGluR1alpha-dependent signaling pathways. PKC activation selectively inhibits agonist-dependent stimulation of the InsP(3) pathway but does not affect receptor signaling via cAMP. In contrast, protein kinase A potentiates agonist-independent signaling of the receptor via InsP(3). Furthermore, we demonstrate that the selectivity of PKC action on receptor signaling rests on phosphorylation of a threonine residue located in the G protein-interacting domain of the receptor. Modification at Thr(695) selectively disrupts mGluR1alpha-G(q/11) interaction without affecting signaling through G(s). Together, these data provide insight on the mechanisms by which selective down-regulation of a specific receptor-dependent signaling pathway can be achieved and on how cross-talk between different second messenger cascades may contribute to fine-tune short- and long-term receptor activity.
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Affiliation(s)
- A Francesconi
- Department of Ophthalmology, Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
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875
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Choi DJ, Rockman HA. Beta-adrenergic receptor desensitization in cardiac hypertrophy and heart failure. Cell Biochem Biophys 2000; 31:321-9. [PMID: 10736754 DOI: 10.1007/bf02738246] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- D J Choi
- Department of Medicine, University of North Carolina at Chapel Hill 27599, USA
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876
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Morisco C, Zebrowski D, Condorelli G, Tsichlis P, Vatner SF, Sadoshima J. The Akt-glycogen synthase kinase 3beta pathway regulates transcription of atrial natriuretic factor induced by beta-adrenergic receptor stimulation in cardiac myocytes. J Biol Chem 2000; 275:14466-75. [PMID: 10799529 DOI: 10.1074/jbc.275.19.14466] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We examined the mechanism of atrial natriuretic factor (ANF) transcription by isoproterenol (ISO), an agonist for the beta-adrenergic receptor (betaAR), in cardiac myocytes. ISO only modestly activated members of the mitogen-activated protein kinase family. ISO-induced ANF transcription was not affected by inhibition of mitogen-activated protein kinases, whereas it was significantly inhibited by KN93, an inhibitor of Ca(2+)/calmodulin-dependent kinase (CaM kinase II). Production of 3'-phosphorylated phosphatidylinositides (3 phosphoinositides) was also required for ISO-induced ANF transcription. ISO caused phosphorylation (Ser-473) and activation of Akt through CaM kinase II- and 3 phosphoinositides-dependent mechanisms. Constitutively active Akt increased myocyte surface area, total protein content, and ANF expression, whereas dominant negative Akt blocked ISO-stimulated ANF transcription. ISO caused Ser-9 phosphorylation and decreased activities of GSK3beta. Overexpression of GSK3beta inhibited ANF transcription, which was reversed by ISO. ISO failed to reverse the inhibitory effect of GSK3beta(S9A), an Akt-insensitive mutant. Kinase-inactive GSK3beta increased ANF transcription. Cyclosporin A partially inhibited ISO-stimulated ANF transcription, indicating that calcineurin only partially mediates ANF transcription. These results suggest that both CaM kinase II and 3 phosphoinositides mediate betaAR-induced Akt activation and ANF transcription in cardiac myocytes. Furthermore, betaAR-stimulated ANF transcription is predominantly mediated by activation of Akt and subsequent phosphorylation/inhibition of GSK3beta.
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Affiliation(s)
- C Morisco
- Weis Center for Research, Department of Molecular Cellular Physiology, Pennsylvania State University College of Medicine, Danville, Pennsylvania 17822, USA
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877
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Gilbert EM, Port JD. Deactivation of the sympathetic nervous system in patients with chronic congestive heart failure. Curr Cardiol Rep 2000; 2:225-32. [PMID: 10980897 DOI: 10.1007/s11886-000-0073-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In this article, we review the basic biology, signal transduction pathways, and clinical pharmacology associated with cardiac beta-adrenergic receptors (beta-ARs) in the context of the use of beta-blocking agents in patients with chronic congestive heart failure. Adrenergic receptors, particularly the beta-AR subtypes (beta(1)-AR and beta(2)-AR), are known to play a critical role in the modulation of cardiac function, providing for both "adaptive" and "maladaptive" compensatory changes. In the context of exercise or self-preservation, the adrenergic nervous system, acting via beta-ARs permits an appropriately rapid, highly-dynamic increase in cardiac function. Conversely, in individuals with chronic congestive heart failure, the sustained, heightened activation of adrenergic nervous system, as manifested by increases in circulating catecholamines, results in down- regulation and desensitization of myocardial beta-ARs, and potentially, significant myocardial damage. A number of recent clinical trials have demonstrated a marked mortality benefit from using beta-blocking agents such as metoprolol and carvedilol in patients with heart failure. The pharmacologic properties of several of these drugs and some of the specifics of their usefulness and limitations are discussed herein.
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Affiliation(s)
- E M Gilbert
- Division of Cardiology 4A-100, University of Utah Health Sciences Center, 50 North Medical Drive, Salt Lake City, UT 84132, USA.
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878
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Müllner C, Vorobiov D, Bera AK, Uezono Y, Yakubovich D, Frohnwieser-Steinecker B, Dascal N, Schreibmayer W. Heterologous facilitation of G protein-activated K(+) channels by beta-adrenergic stimulation via cAMP-dependent protein kinase. J Gen Physiol 2000; 115:547-58. [PMID: 10779313 PMCID: PMC2217221 DOI: 10.1085/jgp.115.5.547] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To investigate possible effects of adrenergic stimulation on G protein-activated inwardly rectifying K(+) channels (GIRK), acetylcholine (ACh)-evoked K(+) current, I(KACh), was recorded from adult rat atrial cardiomyocytes using the whole cell patch clamp method and a fast perfusion system. The rise time of I(KACh ) was 0. 4 +/- 0.1 s. When isoproterenol (Iso) was applied simultaneously with ACh, an additional slow component (11.4 +/- 3.0 s) appeared, and the amplitude of the elicited I(KACh) was increased by 22.9 +/- 5.4%. Both the slow component of activation and the current increase caused by Iso were abolished by preincubation in 50 microM H89 (N-[2-((p -bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, a potent inhibitor of PKA). This heterologous facilitation of GIRK current by beta-adrenergic stimulation was further studied in Xenopus laevis oocytes coexpressing beta(2)-adrenergic receptors, m(2 )-receptors, and GIRK1/GIRK4 subunits. Both Iso and ACh elicited GIRK currents in these oocytes. Furthermore, Iso facilitated ACh currents in a way, similar to atrial cells. Cytosolic injection of 30-60 pmol cAMP, but not of Rp-cAMPS (a cAMP analogue that is inhibitory to PKA) mimicked the beta(2)-adrenergic effect. The possibility that the potentiation of GIRK currents was a result of the phosphorylation of the beta-adrenergic receptor (beta(2)AR) by PKA was excluded by using a mutant beta(2)AR in which the residues for PKA-mediated modulation were mutated. Overexpression of the alpha subunit of G proteins (Galpha(s)) led to an increase in basal as well as agonist-induced GIRK1/GIRK4 currents (inhibited by H89). At higher levels of expressed Galpha(s), GIRK currents were inhibited, presumably due to sequestration of the beta/gamma subunit dimer of G protein. GIRK1/GIRK5, GIRK1/GIRK2, and homomeric GIRK2 channels were also regulated by cAMP injections. Mutant GIRK1/GIRK4 channels in which the 40 COOH-terminal amino acids (which contain a strong PKA phosphorylation consensus site) were deleted were also modulated by cAMP injections. Hence, the structural determinant responsible is not located within this region. We conclude that, both in atrial myocytes and in Xenopus oocytes, beta-adrenergic stimulation potentiates the ACh-evoked GIRK channels via a pathway that involves PKA-catalyzed phosphorylation downstream from beta(2)AR.
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Affiliation(s)
- Carmen Müllner
- Institute for Medical Physics and Biophysics, Graz University, A-8010 Graz, Austria
| | - Dimitry Vorobiov
- Department of Physiology and Pharmacology, Tel Aviv University School of Medicine, Tel Aviv 69978, Israel
| | - Amal Kanti Bera
- Department of Physiology and Pharmacology, Tel Aviv University School of Medicine, Tel Aviv 69978, Israel
| | - Yasuhito Uezono
- Department of Physiology and Pharmacology, Tel Aviv University School of Medicine, Tel Aviv 69978, Israel
| | - Daniel Yakubovich
- Department of Physiology and Pharmacology, Tel Aviv University School of Medicine, Tel Aviv 69978, Israel
| | | | - Nathan Dascal
- Department of Physiology and Pharmacology, Tel Aviv University School of Medicine, Tel Aviv 69978, Israel
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879
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Poznansky MC, Olszak IT, Foxall R, Evans RH, Luster AD, Scadden DT. Active movement of T cells away from a chemokine. Nat Med 2000; 6:543-8. [PMID: 10802710 DOI: 10.1038/75022] [Citation(s) in RCA: 246] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Movement towards or away from a given stimulus guides the directional migration of prokaryotes, simple eukaryotes and neurons. As bi-directional cues may influence entry and exit of immune effector cells from tissue sites, we evaluated the migratory responses of T-cell subsets to varying concentrations of the chemokine stromal cell derived factor-1 (SDF-1). There was selective repulsion of subpopulations of T cells at high concentrations of recombinant SDF-1 or naturally occurring bone marrow-derived SDF-1, which could be inhibited by pertussis toxin and antibody against the chemokine receptor CXCR4. Distinct sensitivity profiles to genistein, herbimycin and 8-Br-cAMP biochemically distinguished movement of cells towards or away from an SDF-1 gradient. In vivo, antigen-induced T-cell recruitment into the peritoneal cavity was reversed by high but not low concentrations of SDF-1. The phenomenon of movement away from a chemokine represents a previously unknown mechanism regulating the localization of mature T cells. It adds to the functional repertoire of chemokines that may participate in immune physiology and may be applied therapeutically to alter the immune response.
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Affiliation(s)
- M C Poznansky
- AIDS Research Center and MGH Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachussetts 02129, USA
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880
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Bisognano JD, Weinberger HD, Bohlmeyer TJ, Pende A, Raynolds MV, Sastravaha A, Roden R, Asano K, Blaxall BC, Wu SC, Communal C, Singh K, Colucci W, Bristow MR, Port DJ. Myocardial-directed overexpression of the human beta(1)-adrenergic receptor in transgenic mice. J Mol Cell Cardiol 2000; 32:817-30. [PMID: 10775486 DOI: 10.1006/jmcc.2000.1123] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The beta(1)-adrenergic receptor (AR) is the dominant subtype in non-failing and failing myocardium. beta(1)-AR signaling, by the endogenous neurotransmitter norepinephrine, is central to the regulation of myocardial contractility. In heart failure, the beta(1)-AR undergoes subtype-selective downregulation which may protect against the increased cardiac adrenergic drive associated with this pathophysiological state. To examine the hypothesis that chronically increased beta(1)-AR mediated signaling has adverse myocardial effects, transgenic mice overexpressing the human beta(1)-AR in a cardiac-selective context were produced, utilizing an alpha-myosin heavy chain (MHC) promoter. In these mice, beta(1)-AR protein abundance was approximately 24-46-fold (1-2 pmol/mg protein) that of wild-type mice. Histopathological examination of young (4 months old) and old (approximately 9 months old) transgenic mouse hearts consistently demonstrated large areas of interstitial replacement fibrosis, marked myocyte hypertrophy and myofibrilar disarray. In addition, increased expression of the pre-apoptotic marker, Bax, was observed coincident with regions of fibrosis accompanied by an increased apoptotic index, as measured by TUNEL assay. Older non-transgenic mice exhibited a slight tendency towards a decreased fractional shortening, whereas older beta(1)-AR transgenic mice had a marked reduction in fractional shortening (%FS approximately 30) as determined by echocardiography. Additionally, older beta(1)-AR transgenic mice had an increased left ventricular chamber size. In summary, cardiac-directed overexpression of the human beta(1)-AR in transgenic mice leads to a significant histopathological phenotype with no apparent functional consequence in younger mice and a variable degree of cardiac dysfunction in older animals. This model system may ultimately prove useful for investigating the biological basis of adrenergically-mediated myocardial damage in humans.
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Affiliation(s)
- J D Bisognano
- Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado, 80262, USA
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881
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Affiliation(s)
- B Kobilka
- Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology and Division of Cardiovascular Medicine, Stanford University Medical School, Stanford CA 94305, USA.
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882
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Miller WE, Maudsley S, Ahn S, Khan KD, Luttrell LM, Lefkowitz RJ. beta-arrestin1 interacts with the catalytic domain of the tyrosine kinase c-SRC. Role of beta-arrestin1-dependent targeting of c-SRC in receptor endocytosis. J Biol Chem 2000; 275:11312-9. [PMID: 10753943 DOI: 10.1074/jbc.275.15.11312] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta-Arrestins can act as adapter molecules, coupling G-protein-coupled receptors to proteins involved in mitogenic as well as endocytic pathways. We have previously identified c-SRC as a molecule that is rapidly recruited to the beta2-adrenergic receptor in a beta-arrestin1-dependent manner. Recruitment of c-SRC to the receptor appears to be involved in pathways leading to receptor internalization and mitogen-activated protein kinase activation. This recruitment of c-SRC to the receptor involves an interaction between the amino-terminal proline-rich region of beta-arrestin1 and the Src homology 3 (SH3) domain of c-SRC, but deletion of the proline-rich domain does not totally ablate the interaction. We have found that a major interaction also exists between beta-arrestin1 and the catalytic or kinase domain (SH1) of c-SRC. We therefore hypothesized that a catalytically inactive mutant of the isolated catalytic subunit, SH1(kinase dead) (SH1(KD)), would specifically block those cellular actions of c-SRC that are mediated by beta-arrestin1 recruitment to the G-protein-coupled receptor. In contrast, the majority of cellular phosphorylations catalyzed by c-SRC, which do not involve interaction with the SH1 domain, would be predicted to be unaffected. The SH1(KD) mutant did indeed block beta2-adrenergic receptor internalization and receptor-stimulated tyrosine phosphorylation of dynamin, actions previously shown to be c-SRC-dependent. In contrast, SAM-68 and whole cell tyrosine phosphorylation by c-SRC was unaffected, indicating that the SH1(KD) mutant did not inhibit c-SRC tyrosine kinase activity in general. These results not only clarify the nature of the beta-arrestin1/c-SRC interaction but also implicate beta-arrestin1 as an important mediator of receptor internalization by recruiting tyrosine kinase activity to the cell surface to phosphorylate key endocytic intermediates, such as dynamin.
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Affiliation(s)
- W E Miller
- Department of Medicine, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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883
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884
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Fraser ID, Cong M, Kim J, Rollins EN, Daaka Y, Lefkowitz RJ, Scott JD. Assembly of an A kinase-anchoring protein-beta(2)-adrenergic receptor complex facilitates receptor phosphorylation and signaling. Curr Biol 2000; 10:409-12. [PMID: 10753752 DOI: 10.1016/s0960-9822(00)00419-x] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Phosphorylation of G-protein-coupled receptors by second-messenger-stimulated kinases is central to the process of receptor desensitization [1-3]. Phosphorylation of the beta(2)-adrenergic receptor (beta(2)-AR) by protein kinase A (PKA), in addition to uncoupling adenylate cyclase activation, is obligatory for receptor-mediated activation of mitogen-activated protein kinase (MAP kinase) cascades [4] [5]. Although mechanisms for linking G-protein-coupled receptor kinases to the activated receptor are well established, analogous mechanisms for targeting second messenger kinases to the beta(2)-AR at the plasma membrane have not been elucidated. Here we show that the A-kinase-anchoring protein, AKAP79/150, co-precipitates with the beta(2)-AR in cell and tissue extracts, nucleating a signaling complex that includes PKA, protein kinase C (PKC) and protein phosphatase PP2B. The anchoring protein directly and constitutively interacts with the beta(2)-AR and promotes receptor phosphorylation following agonist stimulation. Functional studies show that PKA anchoring is required to enhance beta(2)-AR phosphorylation and to facilitate downstream activation of the MAP kinase pathway. This defines a role for AKAP79/150 in the recruitment of second-messenger-regulated signaling enzymes to a G-protein-coupled receptor.
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Affiliation(s)
- I D Fraser
- Howard Hughes Medical Institute, Vollum Institute L-474, Oregon Health Sciences University, Portland, 97201, USA
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885
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Krudewig R, Langer B, Vögler O, Markschies N, Erl M, Jakobs KH, van Koppen CJ. Distinct internalization of M2 muscarinic acetylcholine receptors confers selective and long-lasting desensitization of signaling to phospholipase C. J Neurochem 2000; 74:1721-30. [PMID: 10737631 DOI: 10.1046/j.1471-4159.2000.0741721.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although M1-M4 muscarinic acetylcholine receptors (mAChRs) in HEK-293 cells internalize on agonist stimulation, only M1, M3, and M4 but not M2 mAChRs recycle to the plasma membrane. To investigate the functional consequences of this phenomenon, we compared desensitization and resensitization of M2 versus M4 mAChRs. Treatment with 1 mM carbachol for 1 h at 37 degrees C reduced numbers of cell surface M2 and M4 mAChRs by 40-50% and M2 and M4 mAChR-mediated inhibition of adenylyl cyclase, intracellular Ca2+ concentration ([Ca2+]i) increases, and phospholipase C (PLC) activation by 60-70%. Receptor-mediated inhibition of adenylyl cyclase and [Ca2+]i increases significantly resensitized within 3 h. However, M4 but not M2 mAChR-mediated PLC activation resensitized. At 16 degrees C, M2 mAChR-mediated [Ca2+]i increases and PLC stimulation desensitized to a similar extent as at 37 degrees C. However, at 16 degrees C, where M2 mAChR internalization is negligible, both M2 mAChR responses resensitized, demonstrating that M2 mAChR resensitization proceeds at the plasma membrane. Examination of M2 mAChR responses following inactivation of cell surface mAChRs by quinuclidinyl benzilate revealed substantial receptor reserve for coupling to [Ca2+]i increases but not to PLC. We conclude that M2 mAChR internalization induces long-lasting PLC desensitization predominantly because receptor loss is not compensated for by receptor recycling or receptor reserve.
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Affiliation(s)
- R Krudewig
- Institut für Pharmakologie, Universität GH Essen, Germany
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886
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Abstract
The G proteins are components of a complex membrane signaling system designed to modulate extracellular signals as they are transmitted into the cell. The principal components are the receptor, the G proteins including the alpha, beta, gamma subunits and the effector. Associated with these molecules are several molecular processes by which the signal is transmitted, and regulated including desensitization. Molecules such as arrestin, the RGS (regulators of the G-protein signaling) as well as downstream kinases associated with cyclic AMP are key to regulating the G protein signal. Membrane lipids are key for both anchoring this signal system to the plasma membrane but also in defining the signaling process. Through understanding the biology of the signal system, a number of diseases have been linked to dysfunction of the G protein system. It is clear that this important membrane signal system will become the target for more intense investigation and pharmacologic manipulation to treat critical illness.
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Affiliation(s)
- R A Forse
- Department of Surgery, Boston University School of Medicine, MA, USA
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887
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Maudsley S, Pierce KL, Zamah AM, Miller WE, Ahn S, Daaka Y, Lefkowitz RJ, Luttrell LM. The beta(2)-adrenergic receptor mediates extracellular signal-regulated kinase activation via assembly of a multi-receptor complex with the epidermal growth factor receptor. J Biol Chem 2000; 275:9572-80. [PMID: 10734107 DOI: 10.1074/jbc.275.13.9572] [Citation(s) in RCA: 322] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many G protein-coupled receptors (GPCRs) activate MAP kinases by stimulating tyrosine kinase signaling cascades. In some systems, GPCRs stimulate tyrosine phosphorylation by inducing the "transactivation" of a receptor tyrosine kinase (RTK). The mechanisms underlying GPCR-induced RTK transactivation have not been clearly defined. Here we report that GPCR activation mimics growth factor-mediated stimulation of the epidermal growth factor receptor (EGFR) with respect to many facets of RTK function. beta(2)-Adrenergic receptor (beta(2)AR) stimulation of COS-7 cells induces EGFR dimerization, tyrosine autophosphorylation, and EGFR internalization. Coincident with EGFR transactivation, isoproterenol exposure induces the formation of a multireceptor complex containing both the beta(2)AR and the "transactivated" EGFR. beta(2)AR-mediated EGFR phosphorylation and subsequent beta(2)AR stimulation of extracellular signal-regulated kinase (ERK) 1/2 are sensitive to selective inhibitors of both EGFR and Src kinases, indicating that both kinases are required for EGFR transactivation. beta(2)AR-dependent signaling to ERK1/2, like direct EGF stimulation of ERK1/2 activity, is sensitive to inhibitors of clathrin-mediated endocytosis, suggesting that signaling downstream of both the EGF-activated and the GPCR-transactivated EGFRs requires a productive engagement of the complex with the cellular endocytic machinery. Thus, RTK transactivation is revealed to be a process involving both association of receptors of distinct classes and the interaction of the transactivated RTK with the cells endocytic machinery.
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Affiliation(s)
- S Maudsley
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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888
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DeFea KA, Zalevsky J, Thoma MS, Déry O, Mullins RD, Bunnett NW. beta-arrestin-dependent endocytosis of proteinase-activated receptor 2 is required for intracellular targeting of activated ERK1/2. J Cell Biol 2000; 148:1267-81. [PMID: 10725339 PMCID: PMC2174299 DOI: 10.1083/jcb.148.6.1267] [Citation(s) in RCA: 642] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/1999] [Accepted: 02/04/2000] [Indexed: 01/19/2023] Open
Abstract
Recently, a requirement for beta-arrestin-mediated endocytosis in the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) by several G protein-coupled receptors (GPCRs) has been proposed. However, the importance of this requirement for function of ERK1/2 is unknown. We report that agonists of Galphaq-coupled proteinase-activated receptor 2 (PAR2) stimulate formation of a multiprotein signaling complex, as detected by gel filtration, immunoprecipitation and immunofluorescence. The complex, which contains internalized receptor, beta-arrestin, raf-1, and activated ERK, is required for ERK1/2 activation. However, ERK1/2 activity is retained in the cytosol and neither translocates to the nucleus nor causes proliferation. In contrast, a mutant PAR2 (PAR2deltaST363/6A), which is unable to interact with beta-arrestin and, thus, does not desensitize or internalize, activates ERK1/2 by a distinct pathway, and fails to promote both complex formation and cytosolic retention of the activated ERK1/2. Whereas wild-type PAR2 activates ERK1/2 by a PKC-dependent and probably a ras-independent pathway, PAR2(deltaST363/6A) appears to activate ERK1/2 by a ras-dependent pathway, resulting in increased cell proliferation. Thus, formation of a signaling complex comprising PAR2, beta-arrestin, raf-1, and activated ERK1/2 might ensure appropriate subcellular localization of PAR2-mediated ERK activity, and thereby determine the mitogenic potential of receptor agonists.
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Affiliation(s)
- K A DeFea
- Department of Surgery, University of California, San Francisco, San Francisco, California 94143-0660, USA.
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889
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Affiliation(s)
- F Roka
- Institute of Pharmacology, University of Vienna, Währinger Str. 13a; A-1090, Vienna, Austria
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890
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Dautzenberg FM, Higelin J, Teichert U. Functional characterization of corticotropin-releasing factor type 1 receptor endogenously expressed in human embryonic kidney 293 cells. Eur J Pharmacol 2000; 390:51-9. [PMID: 10708706 DOI: 10.1016/s0014-2999(99)00915-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The endogenous expression in human embryonic kidney 293 (HEK293) cells of corticotropin-releasing factor (CRF) receptors was detected. High-affinity binding sites for human CRF (K(i)=3.6 nM), ovine CRF (K(i)=4.6 nM), rat urocortin (K(i)=2.2 nM), sauvagine (K(i)=2.4 nM) and astressin (K(i)=4.3 nM) with the pharmacological characteristics for CRF type 1 (CRF(1)) receptors and B(max) values of approximately 30 fmol/mg protein were determined. The four CRF receptor agonists nonselectively stimulated cAMP production in HEK293 cells at low agonist concentrations, whereas the antagonist astressin shifted the dose-response curve for ovine CRF significantly rightward. Transfection of the pcDNA3 vector into HEK293 cells strongly reduced the expression of the endogenous CRF receptor. Northern blot analysis revealed the expression of a CRF(1) transcript in human neuronal tissues, HEK293, human NTera-2 (NT2) carcinoma, Y-79 retinoblastoma and African green monkey kidney (COS-7) cells. Neither by Northern blot analysis nor by reverse transcriptase PCR (RT-PCR), the expression of CRF(2) could be detected. In cAMP stimulation experiments, functional CRF receptors were detected in these cell lines. These data show that HEK293 and other cell lines endogenously express CRF(1) receptors.
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Affiliation(s)
- F M Dautzenberg
- Pharma Division, Preclinical Research, F. Hoffmann-La Roche, 4070, Basel, Switzerland.
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891
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Parameswaran N, Disa J, Spielman WS, Brooks DP, Nambi P, Aiyar N. Activation of multiple mitogen-activated protein kinases by recombinant calcitonin gene-related peptide receptor. Eur J Pharmacol 2000; 389:125-30. [PMID: 10688975 DOI: 10.1016/s0014-2999(99)00874-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Calcitonin gene-related peptide is a 37-amino-acid neuropeptide and a potent vasodilator. Although calcitonin gene-related peptide has been shown to have a number of effects in a variety of systems, the mechanisms of action and the intracellular signaling pathways, especially the regulation of mitogen-activated protien kinase (MAPK) pathway, is not known. In the present study we investigated the role of calcitonin gene-related peptide in the regulation of MAPKs in human embryonic kidney (HEK) 293 cells stably transfected with a recombinant porcine calcitonin gene-related peptide-1 receptor. Calcitonin gene-related peptide caused a significant dose-dependent increase in cAMP response and the effect was inhibited by calcitonin gene-related peptide(8-37), the calcitonin gene-related peptide-receptor antagonist. Calcitonin gene-related peptide also caused a time- and concentration-dependent increase in extracellular signal-regulated kinase (ERK) and P38 mitogen-activated protein kinase (P38 MAPK) activities, with apparently no significant change in cjun-N-terminal kinase (JNK) activity. Forskolin, a direct activator of adenylyl cyclase also stimulated ERK and P38 activities in these cells suggesting the invovement of cAMP in this process. Calcitonin gene-related peptide-stimulated ERK and P38 MAPK activities were inhibited significantly by calcitonin gene-related peptide receptor antagonist, calcitonin gene-related peptide-(8-37) suggesting the involvement of calcitonin gene-related peptide-1 receptor. Preincubation of the cells with the cAMP-dependent protein kinase inhibitor, H89 [¿N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, hydrochloride¿] inhibited calcitonin gene-related peptide-mediated activation of ERK and p38 kinases. On the other hand, preincubation of the cells with wortmannin ¿[1S-(1alpha,6balpha,9abeta,11alpha, 11bbeta)]-11-(acetyloxy)-1,6b,7,8,9a,10,11, 11b-octahydro-1-(methoxymethyl)-9a,11b-dimethyl-3H-furo[4,3, 2-de]indeno[4,5-h]-2-benzopyran-3,6,9-trione¿, a PI3-kinase inhibitor, attenuated only calcitonin gene-related peptide-induced ERK and not P38 MAPK activation. Thus, these data suggest that activation of ERK by calcitonin gene-related peptide involves a H89-sensitive protein kinase A and a wortmannin-sensitive PI3-kinase while activation of p38 MAPK by calcitonin gene-related peptide involves only the H89 sensitive pathway and is independent of PI3 kinase. This also suggests that although both ERK and P38 can be activated by protein kinase A, the distal signaling components to protein kinase A in the activation of these two kinases (ERK and P38) are different.
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Affiliation(s)
- N Parameswaran
- Department of Physiology, Michigan State University, East Lansing, MI, USA
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892
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Gintzler AR, Chakrabarti S. Opioid tolerance and the emergence of new opioid receptor-coupled signaling. Mol Neurobiol 2000; 21:21-33. [PMID: 11327148 DOI: 10.1385/mn:21:1-2:021] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Multiple cellular adaptations are elicited by chronic exposure to opioids. These include diminution of spare opioid receptors, decreased opioid receptor density, and G-protein content and coupling thereof. All imply that opioid tolefance is a manifestation of a loss of opioid function, i.e., desensitization. Recent observations challenge the exclusiveness of this formulation and indicate that opioid tolerance also results from qualitative changes in opioid signaling. In this article, Gintzler and Chakrabarti discuss the evidence that suggests that opioid tolerance results not only from impaired opioid receptor functionality, but also from altered consequences of coupling. Underlying the latter are fundamental changes in the nature of effectors that are coupled to the opioid receptor/G-protein signaling pathway. These molecular changes include the upregulation of adenylyl cyclase isoforms of the type II family as well as a substantial increase in their phosphorylation state. As a result, there is a shift in opioid receptor/G-protein signaling from predominantly Gialpha inhibitory to Gbetagamma stimulatory following chronic in vivo morphine exposure. These adaptations to chronic morphine indicate the plasticity of opioid-signal transduction mechanisms and the ability of chronic morphine to augment new signaling strategies.
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Affiliation(s)
- A R Gintzler
- Department of Biochemistry, State University of New York Health Science Center at Brooklyn, 11203, USA.
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893
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Krieger-Brauer HI, Medda PK, Sattel B, Kather H. Inhibitory effect of isoproterenol on NADPH-dependent H(2)O(2) generation in human adipocyte plasma membranes is mediated by betagamma-subunits derived from G(s). J Biol Chem 2000; 275:2486-90. [PMID: 10644703 DOI: 10.1074/jbc.275.4.2486] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies revealed that human fat cell plasma membranes contain a multireceptor-linked H(2)O(2)-generating system that is under antagonistic control by hormones and cytokines and is stimulated by insulin via Galpha(i2). In this report, it is shown that the inhibitory action of the beta-adrenergic agonist isoproterenol is mediated by G protein betagamma-subunits, based on observations that its action was specifically reversed by anti-Gbeta antibodies or a C-terminal beta-adrenergic receptor kinase-1 fragment containing the Gbetagamma-binding site of the enzyme, and was mimicked by exogenously supplied G protein betagamma-subunits. Isoproterenol signals through a prototypical G(s)-coupled receptor. Consistent with these results, direct activation of G(s) by cholera toxin or by an anti-Galpha(s) antibody exhibiting beta-adrenergic receptor-mimetic properties (K-20) resulted in an isoproterenol-like inhibition of NADPH-dependent H(2)O(2) generation. In addition, a peptide corresponding to the target sequence of K-20 blocked the action of the catecholamine, apparently by competition between the peptide and G(s) for activated beta-adrenergic receptors, indicating that the G protein betagamma-subunits mediating the inhibitory effects of the catecholamine were in fact derived from G(s).
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Affiliation(s)
- H I Krieger-Brauer
- Klinisches Institut für Herzinfarktforschung an der Medizinischen Universitätsklinik Heidelberg, Bergheimerstrasse 58, D-69115 Heidelberg, Germany
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894
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Thomas WG, Qian H, Chang CS, Karnik S. Agonist-induced phosphorylation of the angiotensin II (AT(1A)) receptor requires generation of a conformation that is distinct from the inositol phosphate-signaling state. J Biol Chem 2000; 275:2893-900. [PMID: 10644757 DOI: 10.1074/jbc.275.4.2893] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors are thought to isomerize between distinct inactive and active conformations, an idea supported by receptor mutations that induce constitutive (agonist-independent) activation. The agonist-promoted active state initiates signaling and, presumably, is then phosphorylated and internalized to terminate the signal. In this study, we examined the phosphorylation and internalization of wild type and constitutively active mutants (N111A and N111G) of the type 1 (AT(1A)) angiotensin II receptor. Cells expressing these receptors were stimulated with angiotensin II (AngII) and [Sar(1),Ile(4),Ile(8)]AngII, an analog that only activates signaling through the constitutive receptors. Wild type AT(1A) receptors displayed a basal level of phosphorylation, which was stimulated by AngII. Unexpectedly, the constitutively active AT(1A) receptors did not exhibit an increase in basal phosphorylation nor was phosphorylation enhanced by AngII stimulation. Phosphorylation of the constitutively active receptors was unaffected by pretreatment with the non-peptide AT(1) receptor inverse agonist, EXP3174, and was not stimulated by the selective ligand, [Sar(1),Ile(4),Ile(8)]AngII. Paradoxically, [Sar(1),Ile(4), Ile(8)]AngII produced a robust ( approximately 85% of AngII), dose-dependent phosphorylation of the wild type AT(1A) receptor at sites in the carboxyl terminus similar to those phosphorylated by AngII. Moreover, internalization of both wild type and constitutive receptors was induced by AngII, but not [Sar(1),Ile(4),Ile(8)]AngII, providing a differentiation between the phosphorylated and internalized states. These data suggest that the AT(1A) receptor can attain a conformation for phosphorylation without going through the conformation required for inositol phosphate signaling and provide evidence for a transition of the receptor through multiple states, each associated with separate stages of receptor activation and regulation. Separate transition states may be a common paradigm for G protein-coupled receptors.
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Affiliation(s)
- W G Thomas
- Molecular Endocrinology Laboratory, Baker Medical Research Institute, Melbourne 8008, Australia.
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895
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Leaney JL, Milligan G, Tinker A. The G protein alpha subunit has a key role in determining the specificity of coupling to, but not the activation of, G protein-gated inwardly rectifying K(+) channels. J Biol Chem 2000; 275:921-9. [PMID: 10625628 DOI: 10.1074/jbc.275.2.921] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In neuronal and atrial tissue, G protein-gated inwardly rectifying K(+) channels (Kir3.x family) are responsible for mediating inhibitory postsynaptic potentials and slowing the heart rate. They are activated by Gbetagamma dimers released in response to the stimulation of receptors coupled to inhibitory G proteins of the G(i/o) family but not receptors coupled to the stimulatory G protein G(s). We have used biochemical, electrophysiological, and molecular biology techniques to examine this specificity of channel activation. In this study we have succeeded in reconstituting such specificity in an heterologous expression system stably expressing a cloned counterpart of the neuronal channel (Kir3.1 and Kir3.2A heteromultimers). The use of pertussis toxin-resistant G protein alpha subunits and chimeras between G(i1) and G(s) indicate a central role for the G protein alpha subunits in determining receptor specificity of coupling to, but not activation of, G protein-gated inwardly rectifying K(+) channels.
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Affiliation(s)
- J L Leaney
- Centre for Clinical Pharmacology, Department of Medicine, University College London, Rayne Institute, 5 University Street, London WC1E 6JJ, United Kingdom
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896
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Ambrosini A, Tininini S, Barassi A, Racagni G, Sturani E, Zippel R. cAMP cascade leads to Ras activation in cortical neurons. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 75:54-60. [PMID: 10648887 DOI: 10.1016/s0169-328x(99)00294-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Monoaminergic G protein-coupled receptors (GPCRs) are highly expressed in the CNS at the cerebrocortical level, where they support a variety of behavioural responses. To elucidate possible intracellular signalling pathways coupled to these receptors, we have studied their ability to activate extracellular signal-regulated kinases (ERKs) in cultured cortical neurons. An increase in ERK activity was observed after stimulation of neurons with dopamine or serotonin, and with agonists selective for various GPCRs. In addition, ERK activation was also observed following treatment with phorbol dibutyrate (PdBu) and forskolin, activators of protein kinase C (PKC) and protein kinase A (PKA), respectively. Concomitant with ERK activation, all the monoaminergic agonists tested also increased the level of active Ras (Ras-GTP). Surprisingly, Ras activation was also observed after activation of cAMP pathway, and this effect was at least in part mediated by PKA. Ras activation by cAMP was unique for neurons, since in PC12 cells forskolin caused activation of ERK but did not increase Ras-GTP level. These results highlight the relevance of Ras as a target for multiple signalling cascades leading to activation of the ERK pathway in neurons.
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Affiliation(s)
- A Ambrosini
- Centre of Neuropharmacology, Institute of Pharmacological Sciences, University of Milan, Via Balzaretti, 9-20133, Milan, Italy
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897
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Bulleit RF, Hsieh T. MEK inhibitors block BDNF-dependent and -independent expression of GABA(A) receptor subunit mRNAs in cultured mouse cerebellar granule neurons. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2000; 119:1-10. [PMID: 10648867 DOI: 10.1016/s0165-3806(99)00119-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) can regulate the maturation of developing cerebellar granule neurons. Within 1-2 days of culture, BDNF induces the expression of granule neuron terminal differentiation markers, particularly GABA(A) receptor alpha6 subunit (GABA(A)alpha6) mRNA. Other trophic factors including insulin-like growth factor, the neurotrophin NT-3, pituitary adenylate cyclase-activating polypeptide (PACAP), and fetal bovine serum failed to induce this early expression. The expression of other GABA(A) receptor subunits, including alpha1 and gamma2, was also enhanced by exposure of developing granule neurons to BDNF. This BDNF-dependent expression of GABA(A) receptor subunit mRNAs could be effectively blocked by treatment with the mitogen-activated protein kinase kinase (MEK) inhibitors, PD98059 or U0126. In the absence of BDNF, GABA(A)alpha6 expression occurs but not until 3-4 days of culture. This BDNF-independent expression of GABA(A)alpha6 was also inhibited by PD98059. Further studies showed that the BDNF-dependent expression GABA(A)alpha6 could also be reduced by LY294002, an inhibitor of the phosphatidylinositol 3-kinase, or depolarizing concentrations of KCl. These results thus suggest that both BDNF-dependent and -independent expressions of GABA(A) receptor subunits require the activation of MEK and the mitogen-activated protein kinase (MAPK) pathway. However, it is also likely that other signaling pathways modulate this maturation process.
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Affiliation(s)
- R F Bulleit
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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898
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Tepe NM, Liggett SB. Functional receptor coupling to Gi is a mechanism of agonist-promoted desensitization of the beta2-adrenergic receptor. J Recept Signal Transduct Res 2000; 20:75-85. [PMID: 10711498 DOI: 10.3109/10799890009150038] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The beta2-adrenergic receptor (beta2AR) couples to Gs activating adenylyl cyclase (AC) and increasing cAMP. Such signaling undergoes desensitization with continued agonist exposure. Beta2AR also couple to Gi after receptor phosphorylation by the cAMP dependent protein kinase A, but the efficiency of such coupling is not known. Given the PKA dependence of beta2AR-Gi coupling, we explored whether this may be a mechanism of agonist-promoted desensitization. HEK293 cells were transfected to express beta2AR or beta2AR and Gialpha2, and then treated with vehicle or the agonist isoproterenol to evoke agonist-promoted beta2AR desensitization. Membrane AC activities showed that Gialpha2 overexpression decreased basal levels, but the fold-stimulation of the AC over basal by agonist was not altered. However, with treatment of the cells with isoproterenol prior to membrane preparation, a marked decrease in agonist-stimulated AC was observed with the cells overexpressing Gialpha2. In the absence of such overexpression, beta2AR desensitization was 23+/-7%, while with 5-fold Gialpha2 overexpression desensitization was 58+/-5% (p<0.01, n=4). The effect of Gi on desensitization was receptor-specific, in that forskolin responses were not altered by G(i)alpha2 overexpression. Thus, acquired beta2AR coupling to Gi is an important mechanism of agonist-promoted desensitization, and pathologic conditions that increase Gi levels contribute to beta2AR dysfunction.
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Affiliation(s)
- N M Tepe
- Department of Pharmacology, University of Cincinnati College of Medicine, OH 45267-0564, USA
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899
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Vollmer JY, Alix P, Chollet A, Takeda K, Galzi JL. Subcellular compartmentalization of activation and desensitization of responses mediated by NK2 neurokinin receptors. J Biol Chem 1999; 274:37915-22. [PMID: 10608858 DOI: 10.1074/jbc.274.53.37915] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A functional fluorescent neurokinin NK2 receptor was constructed by joining enhanced green fluorescent protein to the amino-terminal end of the rat NK2 receptor and was expressed in human embryonic kidney cells. On cell suspensions, the binding of fluorescent Bodipy-labeled neurokinin A results in a saturatable and reversible decrease of NK2 receptor fluorescence via fluorescence resonance energy transfer. This can be quantified for nM to microM agonist concentrations and monitored in parallel with intracellular calcium responses. On single cells, receptor site occupancy and local agonist concentration can be determined in real time from the decrease in receptor fluorescence. Simultaneous measurement of intracellular calcium responses and agonist binding reveals that partial receptor site occupancy is sufficient to desensitize cellular response to a second agonist application to the same membrane area. Subsequent stimulation of a distal membrane area leads to a second response to agonist, provided that it had not been exposed to agonist during the first application. Together with persistent translocation of fluorescent protein kinase C to the membrane area exposed to agonist, the present data support that not only homologous desensitization but also heterologous desensitization of NK2 receptors is compartmentalized to discrete membrane domains.
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Affiliation(s)
- J Y Vollmer
- Département Récepteurs et Protéines Membranaires, CNRS UPR 9050, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard Sébastien Brant, 67400 Illkirch, France
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900
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Xu F, Bose SC, McClintock TS. Lobster G-protein coupled receptor kinase that associates with membranes and G(beta) in response to odorants and neurotransmitters. J Comp Neurol 1999; 415:449-59. [PMID: 10570455 DOI: 10.1002/(sici)1096-9861(19991227)415:4<449::aid-cne3>3.0.co;2-u] [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: 11/09/2022]
Abstract
A cDNA clone (lobGRK2) encoding a protein of 690 amino acids with significant similarity to the GRK2 subfamily of G-protein coupled receptor kinases was isolated. lobGRK2 was widely expressed as a 9-kb major transcript and a protein of 80 kDa. It was most abundant in the brain and the olfactory organ but was absent in the eye/eyestalk. Immunocytochemistry revealed lobGRK2 immunoreactivity in the outer dendritic segments of the olfactory receptor neurons, the site of olfactory transduction. LobGRK2 immunoreactivity was observed in most neuronal structures in the brain, although with varying intensity. It was strongest in neuropil, especially the olfactory and accessory lobes but was also detectable in neuronal cell bodies. Stimulation of brain homogenates with a mixture of neurotransmitters increased the association of lobGRK2 with membranes and with G(beta). Similarly, stimulation of olfactory dendrite homogenates with an odorant mixture caused lobGRK2 to associate with G(beta). These results support the conclusion that lobGRK2 responds to odorants and to neurotransmitters and may act to initiate desensitization by phosphorylating G-protein-coupled receptors in the olfactory organ and the brain, respectively.
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Affiliation(s)
- F Xu
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, 40536-0298, USA
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