101
|
Ukhanov K, Corey EA, Brunert D, Klasen K, Ache BW. Inhibitory odorant signaling in Mammalian olfactory receptor neurons. J Neurophysiol 2009; 103:1114-22. [PMID: 20032232 DOI: 10.1152/jn.00980.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Odorants inhibit as well as excite olfactory receptor neurons (ORNs) in many species of animals. Cyclic nucleotide-dependent activation of canonical mammalian ORNs is well established but it is still unclear how odorants inhibit these cells. Here we further implicate phosphoinositide-3-kinase (PI3K), an indispensable element of PI signaling in many cellular processes, in olfactory transduction in rodent ORNs. We show that odorants rapidly and transiently activate PI3K in the olfactory cilia and in the olfactory epithelium in vitro. We implicate known G-protein-coupled isoforms of PI3K and show that they modulate not only the magnitude but also the onset kinetics of the electrophysiological response of ORNs to complex odorants. Finally, we show that the ability of a single odorant to inhibit another can be PI3K dependent. Our collective results provide compelling support for the idea that PI3K-dependent signaling mediates inhibitory odorant input to mammalian ORNs and at least in part contributes to the mixture suppression typically seen in the response of ORNs to complex natural odorants.
Collapse
Affiliation(s)
- Kirill Ukhanov
- Whitney Laboratory, Center for Smell and Taste, University of Florida, Gainesville, FL 32610-0127, USA.
| | | | | | | | | |
Collapse
|
102
|
Adderley SP, Sridharan M, Bowles EA, Stephenson AH, Ellsworth ML, Sprague RS. Protein kinases A and C regulate receptor-mediated increases in cAMP in rabbit erythrocytes. Am J Physiol Heart Circ Physiol 2009; 298:H587-93. [PMID: 20008267 DOI: 10.1152/ajpheart.00975.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of the beta-adrenergic receptor (beta-AR) or the prostacyclin receptor (IPR) results in increases in cAMP and ATP release from erythrocytes. cAMP levels depend on a balance between synthesis via adenylyl cyclase and hydrolysis by phosphodiesterases (PDEs). Previously, we reported that cAMP increases associated with activation of the beta-AR and IPR in rabbit and human erythrocytes are tightly regulated by distinct PDEs. Importantly, inhibitors of these PDEs potentiated both increases in cAMP and ATP release. It has been shown that increases in protein kinase (PK) activity can activate PDE3 and PDE4. Both PKA and PKC are present in the erythrocyte and can phosphorylate and activate these PDEs. Here we investigate the hypothesis that PKA regulates PDE activity associated with the beta-AR and both PKA and PKC regulate the PDE activity associated with the IPR in rabbit erythrocytes. Pretreatment of erythrocytes with the PKA inhibitor, H89 (10 microM), in the presence of the PDE4 inhibitor, rolipram (10 microM), augmented isoproterenol (1 microM)-induced cAMP increases. In contrast, in the presence of the PDE3 inhibitor, cilostazol (10 microM), pretreatment of erythrocytes with either H89 (1 microM) or two chemically dissimilar inhibitors of PKC, calphostin C (1 microM) or GFX109203X (1 microM), potentiated iloprost (1 microM)-induced cAMP increases. Furthermore, pretreatment of erythrocytes with both H89 and GFX109203X in the presence of cilostazol augmented the iloprost-induced increases in cAMP to a greater extent than either PK inhibitor individually. These results support the hypothesis that PDEs associated with receptor-mediated increases in cAMP in rabbit erythrocytes are regulated by kinases specific to the receptor's signaling pathway.
Collapse
Affiliation(s)
- Shaquria P Adderley
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, Saint Louis, Missouri, USA.
| | | | | | | | | | | |
Collapse
|
103
|
Liu R, Ramani B, Soto D, De Arcangelis V, Xiang Y. Agonist dose-dependent phosphorylation by protein kinase A and G protein-coupled receptor kinase regulates beta2 adrenoceptor coupling to G(i) proteins in cardiomyocytes. J Biol Chem 2009; 284:32279-87. [PMID: 19706594 DOI: 10.1074/jbc.m109.021428] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adrenoceptors receptors (ARs) play a pivotal role in regulating cardiovascular response to catecholamines during stress. beta(2)ARs, prototypical G protein-coupled receptors (GPCRs), expressed in animal hearts, display dual coupling to both G(s) and G(i) proteins to control the adenylyl cyclase-cAMP dependent protein kinase A (PKA) pathway to regulate contraction responses. Here, we showed that the beta(2)AR coupling to G(i) proteins was agonist dose-dependent and occurred only at high concentrations in mouse cardiac myocytes. Both the beta(2)AR-induced PKA activity, measured by fluorescence resonance energy transfer (FRET) imaging, and the increase in myocyte contraction rate displayed sensitivity to the G(i) inhibitor pertussis toxin (PTX). Further studies revealed that activated beta(2)ARs underwent PKA phosphorylation at a broad range of agonist concentrations. Disruption of the PKA phosphorylation sites on the beta(2)AR blocked receptor/G(i) coupling. However, a sufficient beta(2)AR/G(i) coupling was also dependent on the G protein-coupled receptor kinase (GRK)-mediated phosphorylation of the receptors, which only occurred at high concentrations of agonist (> or = 100 nm). Disruption of the GRK phosphorylation sites on the beta(2)AR blocked receptor internalization and coupling to G(i) proteins, probably by preventing the receptor's transportation to access G(i) proteins. Furthermore, neither PKA nor GRK site mutated receptors displayed sensitivity to the G(i)-specific inhibitor, G(i)CT. Together, our studies revealed distinct roles of PKA and GRK phosphorylation of the beta(2)AR for agonist dose-dependent coupling to G(i) proteins in cardiac myocytes, which may protect cells from overstimulation under high concentrations of catecholamines.
Collapse
Affiliation(s)
- Ruijie Liu
- Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801, USA
| | | | | | | | | |
Collapse
|
104
|
Current concepts of neurohormonal activation in heart failure: mediators and mechanisms. AACN Adv Crit Care 2009; 19:364-85; quiz 386-7. [PMID: 18981739 DOI: 10.1097/01.aacn.0000340718.93742.c4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Neurohormonal activation is a commonly cited array of phenomena in the body's physiologic response to heart failure. Although various neurohormones and pharmacologic agents that moderate their pathophysiologic effects have been reviewed in the nursing literature, both the mechanisms of neurohormonal system activation and cellular and organ system effects have been described only in brief. Accordingly, this article reviews mechanisms of neurohormonal activation and describes cellular and cardiovascular effects of the (1) sympathetic nervous system, (2) renin-angiotensin-aldosterone system, (3) kallikrein-kininogen-kinin system, (4) vasopressinergic system, (5) natriuretic peptide systems, and (6) endothelin in the context of heart failure. This article implicitly details the physiologic basis for numerous current and potential future pharmacologic agents used in the management of heart failure. It is intended that this article be used as a reference for advanced clinical nursing practice, research, and education.
Collapse
|
105
|
Siedlecka U, Arora M, Kolettis T, Soppa GKR, Lee J, Stagg MA, Harding SE, Yacoub MH, Terracciano CMN. Effects of clenbuterol on contractility and Ca2+ homeostasis of isolated rat ventricular myocytes. Am J Physiol Heart Circ Physiol 2008; 295:H1917-26. [PMID: 18775853 DOI: 10.1152/ajpheart.00258.2008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clenbuterol, a compound classified as a beta2-adrenoceptor (AR) agonist, has been employed in combination with left ventricular assist devices (LVADs) to treat patients with severe heart failure. Previous studies have shown that chronic administration of clenbuterol affects cardiac excitation-contraction coupling. However, the acute effects of clenbuterol and the signaling pathway involved remain undefined. We investigated the acute effects of clenbuterol on isolated ventricular myocyte sarcomere shortening, Ca2+ transients, and L-type Ca2+ current and compared these effects to two other clinically used beta2-AR agonists: fenoterol and salbutamol. Clenbuterol (30 microM) produced a negative inotropic response, whereas fenoterol showed a positive inotropic response. Salbutamol had no significant effects. Clenbuterol reduced Ca2+ transient amplitude and L-type Ca2+ current. Selective beta1-AR blockade did not affect the action of clenbuterol on sarcomere shortening but significantly reduced contractility in the presence of fenoterol and salbutamol (P < 0.05). Incubation with 2 microg/ml pertussis toxin significantly reduced the negative inotropic effects of 30 microM clenbuterol. In addition, overexpression of inhibitory G protein (Gi) by adenoviral transfection induced a stronger clenbuterol-mediated negative inotropic effect, suggesting the involvement of the Gi protein. We conclude that clenbuterol does not increase and, at high concentrations, significantly depresses contractility of isolated ventricular myocytes, an effect not seen with fenoterol or salbutamol. In its negative inotropism, clenbuterol predominantly acts through Gi, and the consequent downstream signaling pathways activation may explain the beneficial effects observed during chronic administration of clenbuterol in patients treated with LVADs.
Collapse
Affiliation(s)
- U Siedlecka
- Heart Science Centre, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
106
|
Hutchinson DS, Summers RJ, Bengtsson T. Regulation of AMP-activated protein kinase activity by G-protein coupled receptors: Potential utility in treatment of diabetes and heart disease. Pharmacol Ther 2008; 119:291-310. [DOI: 10.1016/j.pharmthera.2008.05.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Accepted: 05/27/2008] [Indexed: 12/25/2022]
|
107
|
Bruss MD, Richter W, Horner K, Jin SLC, Conti M. Critical role of PDE4D in beta2-adrenoceptor-dependent cAMP signaling in mouse embryonic fibroblasts. J Biol Chem 2008; 283:22430-42. [PMID: 18508768 DOI: 10.1074/jbc.m803306200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
One of the defining properties of beta2-adrenergic receptor (beta(2)AR) signaling is the transient and rapidly reversed accumulation of cAMP. Here we have investigated the contribution of different PDE4 proteins to the generation of this transient response. To this aim, mouse embryonic fibroblasts deficient in PDE4A, PDE4B, or PDE4D were generated, and the regulation of PDE activity, the accumulation of cAMP, and CREB phosphorylation in response to isoproterenol were monitored. Ablation of PDE4D, but not PDE4A or PDE4B, had a major effect on the beta-agonist-induced PDE activation, with only a minimal increase in PDE activity being retained in PDE4D knock-out (KO) cells. Accumulation of cAMP was markedly enhanced, and the kinetics of cAMP accumulation were altered in their properties in PDE4DKO but not PDE4BKO cells. Modest effects were observed in PDE4AKO mouse embryonic fibroblasts. The return to basal levels of both cAMP accumulation and CREB phosphorylation was greatly delayed in the PDE4DKO cells, suggesting that PDE4D is critical for dissipation of the beta2AR stimulus. This effect of PDE4D ablation was in large part due to inactivation of a negative feedback mechanism consisting of the PKA-mediated activation of PDE4D in response to elevated cAMP levels, as indicated by experiments using the cAMP-dependent protein kinase inhibitors H89 and PKI. Finally, PDE4D ablation affected the kinetics of beta2AR desensitization as well as the interaction of the receptor with Galphai. These findings demonstrate that PDE4D plays a major role in shaping the beta2AR signal.
Collapse
Affiliation(s)
- Matthew D Bruss
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California 94143, USA
| | | | | | | | | |
Collapse
|
108
|
Desrues L, Lefebvre T, Diallo M, Gandolfo P, Leprince J, Chatenet D, Vaudry H, Tonon MC, Castel H. Effect of GABA A receptor activation on UT-coupled signaling pathways in rat cortical astrocytes. Peptides 2008; 29:727-34. [PMID: 18355946 DOI: 10.1016/j.peptides.2008.01.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/21/2008] [Accepted: 01/25/2008] [Indexed: 02/07/2023]
Abstract
Cultured rat cortical astrocytes express two types of urotensin II (UII) binding sites: a high affinity site corresponding to the UT (GPR14) receptor and a low affinity site that has not been fully characterized. Activation of the high affinity site in astroglial cells stimulates polyphosphoinositide (PIP) turnover and provokes an increase in intracellular calcium concentration. We have hypothesized that the existence of distinct affinity sites for UII in rat cortical astrocytes could be accounted for by a possible cross-talk between UT and the ligand-gated ion channel GABA(A) receptor (GABA A R). Exposure of cultured astrocytes to UII provoked a bell-shaped increase in cAMP production, with an EC50 stimulating value of 0.83+/-0.04 pM, that was totally blocked in the presence of the adenylyl cyclase inhibitor SQ 22,536. In contrast, UII was found to inhibit forskolin-induced cAMP formation. In the presence of the specific PKA inhibitor H89, UII provoked a sustained stimulation of cAMP formation. Inhibition of PKA by H89 strongly reduced the stimulatory effect of UII on PIP metabolism. GABA and the GABA A R agonist isoguvacine provoked a marked inhibition of UII-induced cAMP synthesis and a significant reduction of UII-evoked PIP turnover. These data suggest that functional interaction between UT and GABA(A)R negatively regulates coupling of UT to the classical PLC/IP(3) signaling cascade as well as to the adenylyl cyclase/PKA pathway.
Collapse
Affiliation(s)
- Laurence Desrues
- INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, 76821 Mont-Saint-Aignan, France
| | | | | | | | | | | | | | | | | |
Collapse
|
109
|
Abstract
Heart failure, or congestive heart failure, is a condition in which the heart cannot supply the body's tissues with enough blood. The result is a cascade of changes that lead to severe fatigue, breathlessness and, ultimately, death. In the past quarter century, much progress has been made in understanding the molecular and cellular processes that contribute to heart failure, leading to the development of effective therapies. Despite this, chronic heart failure remains a major cause of illness and death. And because the condition becomes more common with increasing age, the number of affected individuals is rising with the rapidly ageing global population. New treatments that target disease mechanisms at the cellular and whole-organ level are needed to halt and reverse the devastating consequences of this disease.
Collapse
|
110
|
Hong CS, Kwon SJ, Cho MC, Kwak YG, Ha KC, Hong B, Li H, Chae SW, Chai OH, Song CH, Li Y, Kim JC, Woo SH, Lee SY, Lee CO, Kim DH. Overexpression of junctate induces cardiac hypertrophy and arrhythmia via altered calcium handling. J Mol Cell Cardiol 2008; 44:672-82. [PMID: 18353357 DOI: 10.1016/j.yjmcc.2008.01.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2007] [Revised: 01/15/2008] [Accepted: 01/29/2008] [Indexed: 12/14/2022]
Abstract
Junctate-1 is a newly identified integral endoplasmic/sarcoplasmic reticulum Ca2+ binding protein. However, its functional role in the heart is unknown. In the present study, the consequences of constitutively overexpressed junctate in cardiomyocytes were investigated using transgenic (TG) mice overexpressing junctate-1. TG mice (8 weeks old) showed cardiac remodeling such as marked bi-atrial enlargement with intra-atrial thrombus and biventricular hypertrophy. The TG mice also showed bradycardia with atrial fibrillation, reduced amplitude and elongated decay time of Ca2+ transients, increased L-type Ca2+ current and prolonged action potential durations. Time-course study (2-8 weeks) showed an initially reduced SR function due to down-regulation of SERCA2 and calsequestrin followed by sarcolemmal protein expression and cardiac hypertrophy at later age. These sequential changes could well be correlated with the physiological changes. Adrenergic agonist treatment and subsequent biochemical study showed that junctate-1 TG mice (8 weeks old) were under local PKA signaling that could cause increased L-type Ca2+ current and reduced SR function. Junctate-1 in the heart is closely linked to the homeostasis of E-C coupling proteins and a sustained increase of junctate-1 expression leads to a severe cardiac remodeling and arrhythmias.
Collapse
Affiliation(s)
- Chang-Soo Hong
- Department of Biological Science, College of Natural Sciences, Daegu University, Gyeongsan, South Korea
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
111
|
Morisco C, Marrone C, Galeotti J, Shao D, Vatner DE, Vatner SF, Sadoshima J. Endocytosis machinery is required for beta1-adrenergic receptor-induced hypertrophy in neonatal rat cardiac myocytes. Cardiovasc Res 2008; 78:36-44. [PMID: 18194989 DOI: 10.1093/cvr/cvn008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
AIMS Cardiac hypertrophy by activation of the beta-adrenergic receptor (beta AR) is mediated more efficiently by the beta1-AR than by the beta2-AR. We investigated the signalling mechanism by which the beta1-AR mediates cardiac hypertrophy. METHODS AND RESULTS Experiments were performed in cultured neonatal rat cardiomyocytes. Hypertrophy was determined by the protein/DNA content and atrial natriuretic factor transcription. Phosphorylation of Akt and Src was assessed by immunoblotting. Isoproterenol (ISO, 10 microM), a non-selective beta-AR agonist, caused selective downregulation of the beta1-AR (control beta1 vs. beta2: 35 vs. 65%, Bmax 78 +/- 4 fmol/mg; 4 h, 10 vs. 90%, 61 +/- 5 fmol/mg). Concanavalin A (Con A, 0.5 microg/mL), an inhibitor of endocytosis, prevented downregulation of beta1-ARs by ISO treatment (4 h, 35 vs. 65%, 73 +/- 8 fmol/mg), suggesting that beta1-ARs selectively undergo endocytosis. Interference with beta1-AR endocytosis by Con A, carboxyl terminal peptide of beta-AR kinase-1, dominant negative (DN) beta-arrestin-1, or DN dynamin inhibited beta-adrenergic hypertrophy, suggesting that the endocytosis machinery plays a key role in mediating beta-adrenergic hypertrophy. Activation of Akt by the beta1-AR was blocked by inhibition of the endocytosis machinery, suggesting that endocytosis mediates activation of Akt. Akt plays a critical role in beta-adrenergic hypertrophy, since DN Akt blocked ISO-induced hypertrophy. beta-Adrenergic activation of Akt is mediated by Src, which associates with the endocytosis machinery and is necessary and sufficient to mediate beta-adrenergic hypertrophy. CONCLUSION Activation of the endocytosis machinery is required for activation of Akt, which, in turn, critically mediates beta1-AR-induced cardiac hypertrophy.
Collapse
Affiliation(s)
- Carmine Morisco
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, UMDNJ, New Jersey Medical School, 185 South Orange Avenue, MSB G-609, Newark, NJ 07103, USA
| | | | | | | | | | | | | |
Collapse
|
112
|
Magocsi M, Vizi ES, Selmeczy Z, Brózik A, Szelenyi J. Multiple G-protein-coupling specificity of beta-adrenoceptor in macrophages. Immunology 2007; 122:503-13. [PMID: 17949419 DOI: 10.1111/j.1365-2567.2007.02658.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Adrenergic signalling of the immune system is one of the important modulator pathways of the inflammatory immune response realized via G protein-mediated pathways. The resulted signal depends on the type of the receptor-coupled G-protein (GPCR) that, according to the classical paradigm in the case of beta-adrenergic receptor (beta-AR), is Gs-type. Recently, alternate and/or multiple G protein coupling specificity of GPCRs have been demonstrated including a switch from Gs to Gi binding. The possibility of a Gs/Gi switch and its role in the immune response of macrophages has not been investigated yet. In this study, we demonstrate that beta-adrenergic stimulation itself is able to induce a transient mitogen-activated protein kinase phosphorylation in murine peritoneal macrophages in a pertussis toxin-sensitive manner, suggesting that the Gs/Gi switch also occurs in the immune system. Although this process is very rapid, it can influence different signalling pathways and can reprogramme effector functions suggesting that sympathetic modulation of the defence mechanism of the innate immune system has an additional, Gs/Gi switch-dependent component.
Collapse
Affiliation(s)
- Maria Magocsi
- Institute of Haematology and Immunology, National Medical Centre, Budapest, Hungary.
| | | | | | | | | |
Collapse
|
113
|
Lin R, Peng H, Nguyen LP, Dudekula NB, Shardonofsky F, Knoll BJ, Parra S, Bond RA. Changes in beta 2-adrenoceptor and other signaling proteins produced by chronic administration of 'beta-blockers' in a murine asthma model. Pulm Pharmacol Ther 2007; 21:115-24. [PMID: 17689122 PMCID: PMC2775056 DOI: 10.1016/j.pupt.2007.06.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 06/19/2007] [Indexed: 12/20/2022]
Abstract
BACKGROUND We have previously reported that chronic treatment with certain 'beta-blockers' reduces airway hyperresponsiveness (AHR) to methacholine in a murine model of asthma. METHODS Airway resistance was measured using the forced oscillation technique in ovalbulmin-sensitized and ovalbulmin-challenged mice treated with several beta-adrenoceptor (beta-AR) ligands. We used the selective beta 2-AR ligand ICI 118,551 and the preferential beta 1-AR ligand metoprolol to investigate the receptor subtype mediating the beneficial effect. Expression of beta-ARs was evaluated using immunofluorescence. We evaluated several signaling proteins by western blot using lung homogenates, and measured the relaxation of the isolated trachea produced by EP2 and IP receptor agonists. RESULTS Four findings were associated with the decreased AHR after chronic beta-blocker treatment: (1) the highly selective beta 2-AR antagonist/inverse agonist, ICI 118,551 produced the bronchoprotective effect; (2) beta 2-AR up-regulation resulted from chronic 'beta-blocker' treatment; (3) reduced expression of certain proteins involved in regulating bronchial tone, namely, Gi, phosphodiesterase 4D and phospholipase C-beta 1; and (4) an enhanced bronchodilatory response to prostanoid agonists for the IP and EP2 receptors. CONCLUSIONS These data suggest that in the murine model of asthma, several compensatory changes associated with either increased bronchodilator signaling or decreased bronchoconstrictive signaling, result from the chronic administration of certain 'beta-blockers'.
Collapse
Affiliation(s)
- Rui Lin
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
| | - Hui Peng
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
| | - Long P. Nguyen
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
| | - Noor B. Dudekula
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
| | - Felix Shardonofsky
- Department of Pediatrics, University of Texas, Southwestern Medical Center, Dallas, TX, USA
| | - Brian J. Knoll
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
| | - Sergio Parra
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
| | - Richard A. Bond
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX, USA
- Corresponding author. Tel.: +1 713 743 1210; fax: +1 713 743 1229. address: (R.A. Bond)
| |
Collapse
|
114
|
Warrier S, Ramamurthy G, Eckert RL, Nikolaev VO, Lohse MJ, Harvey RD. cAMP microdomains and L-type Ca2+ channel regulation in guinea-pig ventricular myocytes. J Physiol 2007; 580:765-76. [PMID: 17289786 PMCID: PMC2075464 DOI: 10.1113/jphysiol.2006.124891] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Many different receptors can stimulate cAMP synthesis in the heart, but not all elicit the same functional responses. For example, it has been recognized for some time that prostaglandins such as PGE1 increase cAMP production and activate PKA, but they do not elicit responses like those produced by beta-adrenergic receptor (betaAR) agonists such as isoproterenol (isoprenaline), even though both stimulate the same signalling pathway. In the present study, we confirm that isoproterenol, but not PGE1, is able to produce cAMP-dependent stimulation of the L-type Ca(2+) current in guinea pig ventricular myocytes. This is despite finding evidence that these cells express EP(4) prostaglandin receptors, which are known to activate G(s)-dependent signalling pathways. Using fluorescence resonance energy transfer-based biosensors that are either freely diffusible or bound to A kinase anchoring proteins, we demonstrate that the difference is due to the ability of isoproterenol to stimulate cAMP production in cytosolic and caveolar compartments of intact cardiac myocytes, while PGE1 only stimulates cAMP production in the cytosolic compartment. Unlike other receptor-mediated responses, compartmentation of PGE1 responses was not due to concurrent activation of a G(i)-dependent signalling pathway or phosphodiesterase activity. Instead, compartmentation of the PGE1 response in cardiac myocytes appears to be due to transient stimulation of cAMP in a microdomain that can communicate directly with the bulk cytosolic compartment but not the caveolar compartment associated with betaAR regulation of L-type Ca(2+) channel function.
Collapse
Affiliation(s)
- Sunita Warrier
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA
| | | | | | | | | | | |
Collapse
|
115
|
Hulme JT, Westenbroek RE, Scheuer T, Catterall WA. Phosphorylation of serine 1928 in the distal C-terminal domain of cardiac CaV1.2 channels during beta1-adrenergic regulation. Proc Natl Acad Sci U S A 2006; 103:16574-9. [PMID: 17053072 PMCID: PMC1637623 DOI: 10.1073/pnas.0607294103] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During the fight-or-flight response, epinephrine and norepinephrine released by the sympathetic nervous system increase L-type calcium currents conducted by Ca(V)1.2a channels in the heart, which contributes to enhanced cardiac performance. Activation of beta-adrenergic receptors increases channel activity via phosphorylation by cAMP-dependent protein kinase (PKA) tethered to the distal C-terminal domain of the alpha(1) subunit via an A-kinase anchoring protein (AKAP15). Here we measure phosphorylation of S1928 in dissociated rat ventricular myocytes in response to beta-adrenergic receptor stimulation by using a phosphospecific antibody. Isoproterenol treatment increased phosphorylation of S1928 in the distal C-terminal domain, and a similar increase was observed with a direct activator of adenylyl cyclase, forskolin, confirming that the cAMP and PKA are responsible. Pretreatment with selective beta1- and beta2-adrenergic antagonists reduced the increase in phosphorylation by 79% and 42%, respectively, and pretreatment with both agents completely blocked it. In contrast, treatment with these agents in the presence of 1,2-bis(2-aminophenoxy)ethane-N',N'-tetraacetic acid (BAPTA)-acetoxymethyl ester to buffer intracellular calcium results in only beta1-stimulated phosphorylation of S1928. Whole-cell patch clamp studies with intracellular BAPTA demonstrated that 98% of the increase in calcium current was attributable to beta1-adrenergic receptors. Thus, beta-adrenergic stimulation results in phosphorylation of S1928 on the Ca(V)1.2 alpha1 subunit in intact ventricular myocytes via both beta1- and beta2-adrenergic receptor pathways, but the beta2-dependent increase in phosphorylation depends on elevated intracellular calcium and does not contribute to regulation of whole-cell calcium currents at basal calcium levels. Our results correlate phosphorylation of S1928 with beta1-adrenergic functional up-regulation of cardiac calcium channels in the presence of BAPTA in intact ventricular myocytes.
Collapse
Affiliation(s)
- Joanne T. Hulme
- Department of Pharmacology, University of Washington, Mailstop 357280, Seattle, WA 98195-7280
| | - Ruth E. Westenbroek
- Department of Pharmacology, University of Washington, Mailstop 357280, Seattle, WA 98195-7280
| | - Todd Scheuer
- Department of Pharmacology, University of Washington, Mailstop 357280, Seattle, WA 98195-7280
| | - William A. Catterall
- Department of Pharmacology, University of Washington, Mailstop 357280, Seattle, WA 98195-7280
- *To whom correspondence should be addressed. E-mail:
| |
Collapse
|
116
|
Schutzer WE, Xue H, Reed JF, Mader SL. Effect of age on vascular beta2-adrenergic receptor desensitization is not mediated by the receptor coupling to Galphai proteins. J Gerontol A Biol Sci Med Sci 2006; 61:899-906. [PMID: 16960020 DOI: 10.1093/gerona/61.9.899] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Beta-adrenergic receptor (beta-AR)-mediated vasorelaxation declines with age. In the vasculature, beta2-AR undergoes protein kinase A-mediated desensitization that causes a switch in the G protein coupled to beta2-AR; Galphai links instead of Galphas. We exposed Fischer 344 rat aortae of increasing age to a desensitizing dose of isoproterenol, and determined its effect on beta2-AR-mediated vasorelaxation. Desensitization decreased beta2-AR-mediated vasorelaxation in young aortae only. Subsequently, we used pertussis toxin to block Galphai to determine whether changes in beta2-AR/G protein coupling occurred. Galphai inhibition did not reverse desensitization or the age-related change, but there appears to be a population of beta2-AR linked to Galphai, as pertussis toxin treatment improved beta2-AR-mediated vasorelaxation in aortae from animals of all ages. These findings suggest aortic beta2-AR in older animals may be maximally desensitized, which would explain impaired vasorelaxation. Our results also imply that protein kinase A-mediated beta2-AR desensitization may not be responsible for the age-related decline.
Collapse
|
117
|
Molenaar P, Chen L, Parsonage WA. Cardiac implications for the use of beta2-adrenoceptor agonists for the management of muscle wasting. Br J Pharmacol 2006; 147:583-6. [PMID: 16432500 PMCID: PMC1751344 DOI: 10.1038/sj.bjp.0706670] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
There are proposals for the implementation of beta(2)-adrenoceptor agonists for the management of muscle wasting diseases. The idea has been initiated by studies in animal models which show that beta(2)-adrenoceptor agonists cause hypertrophy of skeletal muscle. Their use in clinical practice will also need an understanding of possible effects of activation of human heart beta(2)-adrenoceptors. Consequences could include an increased probability of arrhythmias in susceptible patients.
Collapse
Affiliation(s)
- Peter Molenaar
- Discipline of Medicine, The University of Queensland, The Prince Charles Hospital, Chermside, Queensland 4032, Australia.
| | | | | |
Collapse
|
118
|
Ganesan AN, Maack C, Johns DC, Sidor A, O'Rourke B. Beta-adrenergic stimulation of L-type Ca2+ channels in cardiac myocytes requires the distal carboxyl terminus of alpha1C but not serine 1928. Circ Res 2006; 98:e11-8. [PMID: 16397147 PMCID: PMC2692538 DOI: 10.1161/01.res.0000202692.23001.e2] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Beta-adrenoceptor stimulation robustly increases cardiac L-type Ca2+ current (ICaL); yet the molecular mechanism of this effect is still not well understood. Previous reports have shown in vitro phosphorylation of a consensus protein kinase A site at serine 1928 on the carboxyl terminus of the alpha1C subunit; however, the functional role of this site has not been investigated in cardiac myocytes. Here, we examine the effects of truncating the distal carboxyl terminus of the alpha1C subunit at amino acid residue 1905 or mutating the putative protein kinase A site at serine 1928 to alanine in adult guinea pig myocytes, using novel dihydropyridine-insensitive alpha1C adenoviruses, coexpressed with beta2 subunits. Expression of alpha1C truncated at 1905 dramatically attenuated the increase of peak ICaL induced by isoproterenol. However, the point mutation S1928A did not significantly attenuate the beta-adrenergic response. The findings indicate that the distal carboxyl-terminus of alpha1C plays an important role in beta-adrenergic upregulation of cardiac L-type Ca2+ channels, but that phosphorylation of serine 1928 is not required for this effect.
Collapse
Affiliation(s)
- Anand N Ganesan
- Institute of Molecular Cardiobiology, The Johns Hopkins University, Baltimore, MD 21205, USA
| | | | | | | | | |
Collapse
|
119
|
Shenoy SK, Drake MT, Nelson CD, Houtz DA, Xiao K, Madabushi S, Reiter E, Premont RT, Lichtarge O, Lefkowitz RJ. beta-arrestin-dependent, G protein-independent ERK1/2 activation by the beta2 adrenergic receptor. J Biol Chem 2005; 281:1261-73. [PMID: 16280323 DOI: 10.1074/jbc.m506576200] [Citation(s) in RCA: 593] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Physiological effects of beta adrenergic receptor (beta2AR) stimulation have been classically shown to result from G(s)-dependent adenylyl cyclase activation. Here we demonstrate a novel signaling mechanism wherein beta-arrestins mediate beta2AR signaling to extracellular-signal regulated kinases 1/2 (ERK 1/2) independent of G protein activation. Activation of ERK1/2 by the beta2AR expressed in HEK-293 cells was resolved into two components dependent, respectively, on G(s)-G(i)/protein kinase A (PKA) or beta-arrestins. G protein-dependent activity was rapid, peaking within 2-5 min, was quite transient, was blocked by pertussis toxin (G(i) inhibitor) and H-89 (PKA inhibitor), and was insensitive to depletion of endogenous beta-arrestins by siRNA. beta-Arrestin-dependent activation was slower in onset (peak 5-10 min), less robust, but more sustained and showed little decrement over 30 min. It was insensitive to pertussis toxin and H-89 and sensitive to depletion of either beta-arrestin1 or -2 by small interfering RNA. In G(s) knock-out mouse embryonic fibroblasts, wild-type beta2AR recruited beta-arrestin2-green fluorescent protein and activated pertussis toxin-insensitive ERK1/2. Furthermore, a novel beta2AR mutant (beta2AR(T68F,Y132G,Y219A) or beta2AR(TYY)), rationally designed based on Evolutionary Trace analysis, was incapable of G protein activation but could recruit beta-arrestins, undergo beta-arrestin-dependent internalization, and activate beta-arrestin-dependent ERK. Interestingly, overexpression of GRK5 or -6 increased mutant receptor phosphorylation and beta-arrestin recruitment, led to the formation of stable receptor-beta-arrestin complexes on endosomes, and increased agonist-stimulated phospho-ERK1/2. In contrast, GRK2, membrane translocation of which requires Gbetagamma release upon G protein activation, was ineffective unless it was constitutively targeted to the plasma membrane by a prenylation signal (CAAX). These findings demonstrate that the beta2AR can signal to ERK via a GRK5/6-beta-arrestin-dependent pathway, which is independent of G protein coupling.
Collapse
Affiliation(s)
- Sudha K Shenoy
- Howard Hughes Medical Institute at Duke University Medical Center, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
120
|
Abstract
Recently, low--but abnormal--rates of cardiomyocyte apoptosis have been observed in failing human hearts. Genetic and pharmacological studies suggest that this cell death is causally linked to heart failure in rodent models. Herein, we review these data and discuss potential therapeutic implications.
Collapse
Affiliation(s)
- Roger S-Y Foo
- Department of Medicine, Cardiovascular Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | |
Collapse
|
121
|
Hoogland TM, Saggau P. Facilitation of L-type Ca2+ channels in dendritic spines by activation of beta2 adrenergic receptors. J Neurosci 2005; 24:8416-27. [PMID: 15456814 PMCID: PMC6729902 DOI: 10.1523/jneurosci.1677-04.2004] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We studied the contribution of L-type Ca2+ channels to action potential-evoked Ca2+ influx in dendritic spines of CA1 pyramidal neurons and the modulation of these channels by the beta2 adrenergic receptor. Backpropagating action potentials (bAPs) (three at 50 Hz) were evoked by brief somatic current injections, and Ca2+ transients were recorded in proximal basal dendrites and associated spines. The R- and T-type Ca2+ channel blocker NiCl2 (100 microm) significantly reduced Ca2+ transients in both spines and their parent dendrites (approximately 50%), suggesting that these channels are the major source of bAP-evoked Ca2+ influx in these structures. The L-type Ca2+ channel blockers nimodipine and nifedipine (both 10 microm) reduced spine Ca2+ transients by approximately 10%, whereas the L-type Ca2+ channel activators FPL 64176 (2,5-dimethyl-4-[2-(phenylmethyl)benzoyl]-1H-pyrrole-3-carboxylic acid methylester) and Bay K 8644 ((+/-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)-phenyl]-3-pyridine carboxylic acid methyl ester) (both 10 microm) significantly enhanced the spine Ca2+ transients by 40-50%. Activation of beta2 adrenergic receptors with salbutamol (40 microm) or formoterol (5 microm) resulted in significant enhancements of the spine (40-50%) but not dendritic Ca2+ transients. This increase was prevented when L-type Ca2+ channels were blocked with nimodipine (10 microm) or when cAMP-dependent protein kinase A (PKA) was inhibited with KT5720 (3 microm), Rp-cAMPS (Rp-adenosine cyclic 3',5'-phosphorothioate) (100 microm), or PKI (100 microm). The above data suggest that L-type Ca2+ channels are functionally present in dendritic spines of CA1 pyramidal neurons, contribute to spine Ca2+ influx, and can be modulated by the beta2 adrenergic receptor through PKA in a highly compartmentalized manner.
Collapse
Affiliation(s)
- Tycho M Hoogland
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
| | | |
Collapse
|
122
|
Guimond J, Mamarbachi AM, Allen BG, Rindt H, Hébert TE. Role of specific protein kinase C isoforms in modulation of β1- and β2-adrenergic receptors. Cell Signal 2005; 17:49-58. [PMID: 15451024 DOI: 10.1016/j.cellsig.2004.05.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Revised: 05/14/2004] [Accepted: 05/24/2004] [Indexed: 11/30/2022]
Abstract
The function of beta-adrenergic receptor (betaAR) is modulated by the activity status of alpha1-adrenergic receptors (alpha1ARs) via molecular crosstalk, and this becomes evident when measuring cardiac contractile responses to adrenergic stimulation. The molecular mechanism underlying this crosstalk is unknown. We have previously demonstrated that overexpression of alpha1B-adrenergic receptor (alpha1BAR) in transgenic mice leads to a marked desensitization of betaAR-mediated adenylyl cyclase stimulation which is correlated with increased levels of activated protein kinase C (PKC) beta, delta and [J. Mol. Cell. Cardiol. 30 (1998) 1827]. Therefore, we wished to determine which PKC isoforms play a role in heterologous betaAR desensitization and also which isoforms of the betaAR were the molecular target(s) for PKC. In experiments using constitutively activated PKC expression constructs transfected into HEK 293 cells also expressing the beta2AR, constitutively active (CA)-PKC overexpression was first confirmed by immunoblots using specific anti-PKC antibodies. We then demonstrated that the different PKC subtypes lead to a decreased maximal cAMP accumulation following isoproterenol stimulation with a rank order of PKCalpha > or = PKCzeta>PKC>PKCbetaII. However, a much more dramatic desensitization of adenylyl cyclase stimulation was observed in cells co-transfected with different PKC isoforms and beta1AR. Further, the modulation of beta1AR by PKC isoforms had a different rank order than for the beta2AR: PKCbetaII>PKCalpha>PKC>PKCzeta. PKC-mediated desensitization was reduced by mutating consensus cAMP-dependent protein kinase (PKA)/PKC sites in the third intracellular loop and/or the carboxy-terminal tail of either receptor. Our results demonstrate therefore that the beta1AR is the most likely molecular target for PKC-mediated heterologous desensitization in the mammalian heart and that modulation of adrenergic receptor activity in any given cell type will depend on the complement of PKC isoforms present.
Collapse
Affiliation(s)
- Julie Guimond
- Centre de Recherche, Institut de Cardiologie de Montréal, 5000 rue Bélanger est, Montréal, PQ, Canada H1T 1C8
| | | | | | | | | |
Collapse
|
123
|
Liu G, Shi J, Yang L, Cao L, Park SM, Cui J, Marx SO. Assembly of a Ca2+-dependent BK channel signaling complex by binding to beta2 adrenergic receptor. EMBO J 2004; 23:2196-205. [PMID: 15141163 PMCID: PMC419908 DOI: 10.1038/sj.emboj.7600228] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 04/14/2004] [Indexed: 01/08/2023] Open
Abstract
Large-conductance voltage and Ca2+-activated potassium channels (BKCa) play a critical role in modulating contractile tone of smooth muscle, and neuronal processes. In most mammalian tissues, activation of beta-adrenergic receptors and protein kinase A (PKAc) increases BKCa channel activity, contributing to sympathetic nervous system/hormonal regulation of membrane excitability. Here we report the requirement of an association of the beta2-adrenergic receptor (beta2AR) with the pore forming alpha subunit of BKCa and an A-kinase-anchoring protein (AKAP79/150) for beta2 agonist regulation. beta2AR can simultaneously interact with both BKCa and L-type Ca2+ channels (Cav1.2) in vivo, which enables the assembly of a unique, highly localized signal transduction complex to mediate Ca2+- and phosphorylation-dependent modulation of BKCa current. Our findings reveal a novel function for G protein-coupled receptors as a scaffold to couple two families of ion channels into a physical and functional signaling complex to modulate beta-adrenergic regulation of membrane excitability.
Collapse
MESH Headings
- Animals
- Aorta/metabolism
- Brain/metabolism
- Calcium/metabolism
- Cell Line
- Cloning, Molecular
- Dimerization
- Electrophysiology
- Female
- Gene Expression Regulation
- Glutathione Transferase/metabolism
- Humans
- Immunohistochemistry
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
- Lung/metabolism
- Models, Biological
- Muscle, Smooth/metabolism
- Oocytes/physiology
- Patch-Clamp Techniques
- Phosphorylation
- Potassium Channels/genetics
- Potassium Channels/metabolism
- Potassium Channels, Calcium-Activated/metabolism
- Precipitin Tests
- RNA, Messenger/genetics
- Rats
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/metabolism
- Signal Transduction
- Up-Regulation
- Urinary Bladder/metabolism
- Xenopus
Collapse
Affiliation(s)
- Guoxia Liu
- Division of Cardiology and Center for Molecular Cardiology, Department of Medicine and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Jingyi Shi
- Cardiac Bioelectricity Research and Training Center and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Lin Yang
- Division of Cardiology and Center for Molecular Cardiology, Department of Medicine and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Luxiang Cao
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Soo Mi Park
- Division of Cardiology and Center for Molecular Cardiology, Department of Medicine and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Jianmin Cui
- Cardiac Bioelectricity Research and Training Center and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Steven O Marx
- Division of Cardiology and Center for Molecular Cardiology, Department of Medicine and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Division of Cardiology and Center for Molecular Cardiology, Department of Medicine and Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA. Tel.: +1 212 305 0271; Fax: +1 212 342 0475; E-mail:
| |
Collapse
|
124
|
Barouch LA, Berkowitz DE, Harrison RW, O'Donnell CP, Hare JM. Disruption of leptin signaling contributes to cardiac hypertrophy independently of body weight in mice. Circulation 2003; 108:754-9. [PMID: 12885755 DOI: 10.1161/01.cir.0000083716.82622.fd] [Citation(s) in RCA: 241] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Whether left ventricular hypertrophy (LVH) in obesity results from increased hemodynamic load or altered neurohormonal signaling remains controversial. Dysregulation of leptin, a neurohormone essential to energy homeostasis, is implicated in the pathogenesis of obesity. Because leptin has cardiovascular bioactivity, we hypothesized that disruption of leptin signaling mediates the development of obesity-associated LVH. METHODS AND RESULTS We measured left ventricular (LV) wall thickness and LV mass with echocardiography in mice lacking leptin (ob/ob, n=15) or functional receptor (db/db, n=10) and controls at 2, 4, and 6 months of age. None of the mice had LVH at 2 months. Progressive obesity developed in ob/ob and db/db mice. At 6 months, LVH occurred in ob/ob and db/db compared with controls. We observed corresponding myocyte hypertrophy by light microscopy. To separate the direct contribution of leptin deficiency from mechanical effects of obesity, we induced weight loss in 6- to 8-month-old ob/ob mice either by leptin infusion or caloric restriction. Mice in both groups lost similar weight compared with placebo-treated controls. Leptin infusion completely reversed the increase in wall thickness with partial resolution of myocyte hypertrophy, whereas calorie-restricted mice had no decrease in wall thickness and a lesser change in myocyte size. CONCLUSIONS Together these data show that the effect of leptin on LV remodeling is not attributable to weight loss alone, indicating that leptin has antihypertrophic effects on the heart, either directly or through a leptin-regulated neurohumoral pathway. Disruption of leptin signaling may represent a novel mechanism in LVH and related cardiovascular disorders.
Collapse
Affiliation(s)
- Lili A Barouch
- Department of Medicine, Division of Cardiology, Johns Hopkins Hospital, 600 North Wolfe St, Baltimore, Md 21287, USA
| | | | | | | | | |
Collapse
|
125
|
Hermans E. Biochemical and pharmacological control of the multiplicity of coupling at G-protein-coupled receptors. Pharmacol Ther 2003; 99:25-44. [PMID: 12804697 DOI: 10.1016/s0163-7258(03)00051-2] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
For decades, it has been generally proposed that a given receptor always interacts with a particular GTP-binding protein (G-protein) or with multiple G-proteins within one family. However, for several G-protein-coupled receptors (GPCR), it now becomes generally accepted that simultaneous functional coupling with distinct unrelated G-proteins can be observed, leading to the activation of multiple intracellular effectors with distinct efficacies and/or potencies. Multiplicity in G-protein coupling is frequently observed in artificial expression systems where high densities of receptors are obtained, raising the question of whether such complex signalling reveals artefactual promiscuous coupling or is a genuine property of GPCRs. Multiple biochemical and pharmacological evidence in favour of an intrinsic property of GPCRs were obtained in recent studies. Thus, there are now many examples showing that the coupling to multiple signalling pathways is dependent on the agonist used (agonist trafficking of receptor signals). In addition, the different couplings were demonstrated to involve distinct molecular determinants of the receptor and to show distinct desensitisation kinetics. Such multiplicity of signalling at the level of G-protein coupling leads to a further complexity in the functional response to agonist stimulation of one of the most elaborate cellular transmission systems. Indeed, the physiological relevance of such versatility in signalling associated with a single receptor requires the existence of critical mechanisms of dynamic regulation of the expression, the compartmentalisation, and the activity of the signalling partners. This review aims at summarising the different studies that support the concept of multiplicity of G-protein coupling. The physiological and pharmacological relevance of this coupling promiscuity will be discussed.
Collapse
Affiliation(s)
- Emmanuel Hermans
- Laboratoire de Pharmacologie Expérimentale, Université Catholique de Louvain, FARL 54.10, Avenue Hippocrate 54, B-1200 Brussels, Belgium.
| |
Collapse
|
126
|
Pönicke K, Heinroth-Hoffmann I, Brodde OE. Role of beta 1- and beta 2-adrenoceptors in hypertrophic and apoptotic effects of noradrenaline and adrenaline in adult rat ventricular cardiomyocytes. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2003; 367:592-9. [PMID: 12750877 DOI: 10.1007/s00210-003-0754-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2002] [Accepted: 03/18/2003] [Indexed: 12/20/2022]
Abstract
In adult rat ventricular cardiomyocytes alpha1-adrenoceptor (AR) stimulation causes increases in protein synthesis. On the other hand beta1-AR stimulation inhibits protein synthesis, and evokes apoptotic cell death. We studied, in adult rat ventricular cardiomyocytes, effects of noradrenaline (NA), adrenaline (ADR) and phenylephrine (PE) on protein synthesis (assessed by [3H]-phenylalanine incorporation into the cardiomyocytes) in relation to effects on early apoptosis (measured by Annexin V/propidium iodide staining). PE (10(-9)-10(-5) M) induced protein synthesis was not affected by the beta1-AR blocker CGP 20712A (CGP, 300 nM) or beta2-AR blocker ICI 118,551 (ICI, 55 nM). ADR (10(-9)-10(-5) M) induced protein synthesis was enhanced by CGP and decreased by ICI. Pretreatment of the cardiomyocytes with pertussis toxin (PTX) decreased NA- and ADR- induced protein synthesis, but did not affect PE-effects. NA (10(-5) M) and ADR (10(-5) M) caused a significant increase in the number of apoptotic cells; these effects were enhanced by PTX-treatment, abolished by CGP, but not significantly affected by ICI. Furthermore, there was a significant negative correlation between catecholamine-evoked apoptosis and catecholamine-induced hypertrophic effects. We conclude that, in ventricular cardiomyocytes of adult rats, growth-promoting effects of NA and ADR are composed of alpha1A-AR mediated increase in protein synthesis and beta1-AR mediated apoptosis that counteracts increases in protein synthesis. The role of beta2-adrenoceptor appears to be a balance of antiapoptotic effects via a PTX-sensitive pathway and proapoptotic effects via a GS-adenylyl cyclase pathway.
Collapse
Affiliation(s)
- Klaus Pönicke
- Institute of Pharmacology, University of Halle, 06097 Halle (Saale), Germany
| | | | | |
Collapse
|
127
|
Zhu WZ, Wang SQ, Chakir K, Yang D, Zhang T, Brown JH, Devic E, Kobilka BK, Cheng H, Xiao RP. Linkage of beta1-adrenergic stimulation to apoptotic heart cell death through protein kinase A-independent activation of Ca2+/calmodulin kinase II. J Clin Invest 2003; 111:617-25. [PMID: 12618516 PMCID: PMC151893 DOI: 10.1172/jci16326] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
beta(1)-adrenergic receptor (beta(1)AR) stimulation activates the classic cAMP/protein kinase A (PKA) pathway to regulate vital cellular processes from the change of gene expression to the control of metabolism, muscle contraction, and cell apoptosis. Here we show that sustained beta(1)AR stimulation promotes cardiac myocyte apoptosis by activation of Ca(2+)/calmodulin kinase II (CaMKII), independently of PKA signaling. beta(1)AR-induced apoptosis is resistant to inhibition of PKA by a specific peptide inhibitor, PKI14-22, or an inactive cAMP analogue, Rp-8-CPT-cAMPS. In contrast, the beta(1)AR proapoptotic effect is associated with non-PKA-dependent increases in intracellular Ca(2+) and CaMKII activity. Blocking the L-type Ca(2+) channel, buffering intracellular Ca(2+), or inhibiting CaMKII activity fully protects cardiac myocytes against beta(1)AR-induced apoptosis, and overexpressing a cardiac CaMKII isoform, CaMKII-deltaC, markedly exaggerates the beta(1)AR apoptotic effect. These findings indicate that CaMKII constitutes a novel PKA-independent linkage of beta(1)AR stimulation to cardiomyocyte apoptosis that has been implicated in the overall process of chronic heart failure.
Collapse
Affiliation(s)
- Wei-Zhong Zhu
- Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
128
|
Sambrano GR, Fraser I, Han H, Ni Y, O'Connell T, Yan Z, Stull JT. Navigating the signalling network in mouse cardiac myocytes. Nature 2002; 420:712-4. [PMID: 12478303 DOI: 10.1038/nature01306] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cardiac myocytes have a complex network of signals that regulates their essential role in the rhythmic pumping of the heart. This network is an appealing model system in which to study the basic principles underlying cellular signalling mechanisms. Progress in this effort has come through the establishment of standardized myocyte isolation and culture procedures and characterization of important signalling responses.
Collapse
Affiliation(s)
- Gilberto R Sambrano
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, California 94143, USA.
| | | | | | | | | | | | | |
Collapse
|
129
|
Xiang Y, Devic E, Kobilka B. The PDZ binding motif of the beta 1 adrenergic receptor modulates receptor trafficking and signaling in cardiac myocytes. J Biol Chem 2002; 277:33783-90. [PMID: 12097326 DOI: 10.1074/jbc.m204136200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Beta(1) and beta(2) adrenergic receptors (AR) regulate the intrinsic contraction rate in neonatal mouse cardiac myocytes through distinct signaling pathways. It has been shown that stimulation of beta(1)ARs leads to a protein kinase A-dependent increase in contraction rate. In contrast, stimulation of beta(2)ARs has a biphasic effect on contraction rate, with an initial protein kinase A-independent increase followed by a sustained decrease that is blocked by pertussis toxin. The beta(2)AR undergoes agonist-induced endocytosis in cardiac myocytes while the beta(1)AR remains on the cell surface. It has been shown that a PDZ domain binding motif at the carboxyl terminus of beta(1)AR interacts with the postsynaptic density protein PSD-95 when both are expressed in HEK293 cells. We found that mutation of this PDZ binding motif in the beta(1)AR (beta(1)AR-PDZ) enabled agonist-induced internalization in cardiac myocytes. Moreover, stimulation of beta(1)AR-PDZ had a biphasic effect on the myocyte contraction rate similar to that observed following stimulation of the beta(2)AR. The secondary decrease in the contraction rate was mediated by G(i) and could be blocked by pertussis toxin. Furthermore, a non-selective endocytosis inhibitor, concanavalin A, inhibited the internalization of wild type beta(2)AR and the mutated beta(1)AR-PDZ, and blocked the coupling of both receptors to G(i). Finally, treating myocytes with a membrane-permeable peptide representing beta(1)AR PDZ motif caused the endogenous beta(1)AR to behave like beta(1)AR-PDZ. These studies suggest that association of the beta(1)AR with PSD-95 or a related protein dictates signaling specificity by retaining the receptor at the cell surface and preventing interaction with G(i).
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Amino Acid Motifs
- Animals
- Animals, Newborn
- Binding Sites
- Biological Transport
- Cells, Cultured
- Cyclic AMP/metabolism
- Discs Large Homolog 1 Protein
- GTP-Binding Proteins/physiology
- Guanylate Kinases
- Heart/physiology
- Membrane Proteins
- Mice
- Mice, Knockout
- Nerve Tissue Proteins/physiology
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/physiology
Collapse
Affiliation(s)
- Yang Xiang
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institution, B157 Beckman Center, Stanford Medical Center, Palo Alto, CA 94043, USA
| | | | | |
Collapse
|