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Lohse MJ, Bock A, Zaccolo M. G Protein-Coupled Receptor Signaling: New Insights Define Cellular Nanodomains. Annu Rev Pharmacol Toxicol 2024; 64:387-415. [PMID: 37683278 DOI: 10.1146/annurev-pharmtox-040623-115054] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/10/2023]
Abstract
G protein-coupled receptors are the largest and pharmacologically most important receptor family and are involved in the regulation of most cell functions. Most of them reside exclusively at the cell surface, from where they signal via heterotrimeric G proteins to control the production of second messengers such as cAMP and IP3 as well as the activity of several ion channels. However, they may also internalize upon agonist stimulation or constitutively reside in various intracellular locations. Recent evidence indicates that their function differs depending on their precise cellular localization. This is because the signals they produce, notably cAMP and Ca2+, are mostly bound to cell proteins that significantly reduce their mobility, allowing the generation of steep concentration gradients. As a result, signals generated by the receptors remain confined to nanometer-sized domains. We propose that such nanometer-sized domains represent the basic signaling units in a cell and a new type of target for drug development.
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Affiliation(s)
- Martin J Lohse
- ISAR Bioscience Institute, Planegg/Munich, Germany;
- Rudolf Boehm Institute of Pharmacology and Toxicology, Leipzig University, Leipzig, Germany
| | - Andreas Bock
- Rudolf Boehm Institute of Pharmacology and Toxicology, Leipzig University, Leipzig, Germany
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics and National Institute for Health and Care Research Oxford Biomedical Research Centre, University of Oxford, Oxford, United Kingdom;
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Ahn S, Maarsingh H, Walker JK, Liu S, Hegde A, Sumajit HC, Kahsai AW, Lefkowitz RJ. Allosteric modulator potentiates β2AR agonist-promoted bronchoprotection in asthma models. J Clin Invest 2023; 133:e167337. [PMID: 37432742 PMCID: PMC10503797 DOI: 10.1172/jci167337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 07/06/2023] [Indexed: 07/12/2023] Open
Abstract
Asthma is a chronic inflammatory disease associated with episodic airway narrowing. Inhaled β2-adrenergic receptor (β2AR) agonists (β2-agonists) promote - with limited efficacy - bronchodilation in asthma. All β2-agonists are canonical orthosteric ligands that bind the same site as endogenous epinephrine. We recently isolated a β2AR-selective positive allosteric modulator (PAM), compound-6 (Cmpd-6), which binds outside of the orthosteric site and modulates orthosteric ligand functions. With the emerging therapeutic potential of G-protein coupled receptor allosteric ligands, we investigated the impact of Cmpd-6 on β2AR-mediated bronchoprotection. Consistent with our findings using human β2ARs, Cmpd-6 allosterically potentiated β2-agonist binding to guinea pig β2ARs and downstream signaling of β2ARs. In contrast, Cmpd-6 had no such effect on murine β2ARs, which lack a crucial amino acid in the Cmpd-6 allosteric binding site. Importantly, Cmpd-6 enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in guinea pig lung slices, but - in line with the binding studies - not in mice. Moreover, Cmpd-6 robustly potentiated β2 agonist-mediated bronchoprotection against allergen-induced airway constriction in lung slices obtained from a guinea pig model of allergic asthma. Cmpd-6 similarly enhanced β2 agonist-mediated bronchoprotection against methacholine-induced bronchoconstriction in human lung slices. Our results highlight the potential of β2AR-selective PAMs in the treatment of airway narrowing in asthma and other obstructive respiratory diseases.
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Affiliation(s)
- Seungkirl Ahn
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Harm Maarsingh
- Department of Pharmaceutical Sciences, Lloyd L. Gregory School of Pharmacy, Palm Beach Atlantic University, West Palm Beach, Florida, USA
| | - Julia K.L. Walker
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
- School of Nursing, Duke University, Durham, North Carolina, USA
| | - Samuel Liu
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Akhil Hegde
- School of Nursing, Duke University, Durham, North Carolina, USA
| | - Hyeje C. Sumajit
- Department of Pharmaceutical Sciences, Lloyd L. Gregory School of Pharmacy, Palm Beach Atlantic University, West Palm Beach, Florida, USA
| | - Alem W. Kahsai
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
| | - Robert J. Lefkowitz
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Biochemistry and
- Howard Hughes Medical Institute, Duke University School of Medicine, Durham, North Carolina, USA
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Chen H, Zhang S, Zhang X, Liu H. QR code model: a new possibility for GPCR phosphorylation recognition. Cell Commun Signal 2022; 20:23. [PMID: 35236365 PMCID: PMC8889771 DOI: 10.1186/s12964-022-00832-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/23/2022] [Indexed: 12/13/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest family of membrane proteins in the human body and are responsible for accurately transmitting extracellular information to cells. Arrestin is an important member of the GPCR signaling pathway. The main function of arrestin is to assist receptor desensitization, endocytosis and signal transduction. In these processes, the recognition and binding of arrestin to phosphorylated GPCRs is fundamental. However, the mechanism by which arrestin recognizes phosphorylated GPCRs is not fully understood. The GPCR phosphorylation recognition "bar code model" and "flute" model describe the basic process of receptor phosphorylation recognition in terms of receptor phosphorylation sites, arrestin structural changes and downstream signaling. These two models suggest that GPCR phosphorylation recognition is a process involving multiple factors. This process can be described by a "QR code" model in which ligands, GPCRs, G protein-coupled receptor kinase, arrestin, and phosphorylation sites work together to determine the biological functions of phosphorylated receptors. Video Abstract.
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Affiliation(s)
- Hao Chen
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, 10 Xitoutiao, You An Men Street, Beijing, 100069, People's Republic of China
| | - Suli Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, 10 Xitoutiao, You An Men Street, Beijing, 100069, People's Republic of China.,Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Xi Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, 10 Xitoutiao, You An Men Street, Beijing, 100069, People's Republic of China
| | - Huirong Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, 10 Xitoutiao, You An Men Street, Beijing, 100069, People's Republic of China. .,Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China.
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Pathological cardiac hypertrophy: the synergy of adenylyl cyclases inhibition in cardiac and immune cells during chronic catecholamine stress. J Mol Med (Berl) 2019; 97:897-907. [PMID: 31062036 DOI: 10.1007/s00109-019-01790-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 04/18/2019] [Accepted: 04/26/2019] [Indexed: 12/21/2022]
Abstract
Response to stressors in our environment and daily lives is an adaptation conserved through evolution as it is beneficial in enhancing the survival and continuity of humans. Although stressors have evolved, the drastic physiological response they elicit still remains unchanged. The chronic secretion and circulation of catecholamines to produce physical responses when they are not required may result in pathological consequences which affect cardiac function drastically. This review seeks to point out the probable implication of chronic stress in inducing an inflammation disorder in the heart. We discussed the likely synergy of a G protein-independent stimuli signaling via β2-adrenergic receptors in both cardiomyocytes and immune cells during chronic catecholamine stress. To explain this synergy, we hypothesized the possibility of adenylyl cyclases having a regulatory effect on G protein-coupled receptor kinases. This was based on the negative correlations they exhibit during normal cardiac function and heart failures. As such, the downregulation of adenylyl cyclases in cardiomyocytes and immune cells during chronic catecholamine stress enhances the expressions of G protein-coupled receptor kinases. In addition, we explain the maladaptive roles played by G protein-coupled receptor kinase and extracellular signal-regulated kinase in the synergistic cascade that pathologically remodels the heart. Finally, we highlighted the therapeutic potentials of an adenylyl cyclases stimulator to attenuate pathological cardiac hypertrophy (PCH) and improve cardiac function in patients developing cardiac disorders due to chronic catecholamine stress.
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Chao PK, Chang HF, Ou LC, Chuang JY, Lee PT, Chang WT, Chen SC, Ueng SH, Hsu JTA, Tao PL, Law PY, Loh HH, Yeh SH. Convallatoxin enhance the ligand-induced mu-opioid receptor endocytosis and attenuate morphine antinociceptive tolerance in mice. Sci Rep 2019; 9:2405. [PMID: 30787373 PMCID: PMC6382827 DOI: 10.1038/s41598-019-39555-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 01/07/2019] [Indexed: 11/29/2022] Open
Abstract
Morphine is a unique opioid analgesic that activates the mu-opioid receptor (MOR) without efficiently promoting its endocytosis that may underlie side effects. Our objective was to discover a novel enhancer of ligand-induced MOR endocytosis and determine its effects on analgesia, tolerance and dependence. We used high-throughput screening to identify convallatoxin as an enhancer of ligand-induced MOR endocytosis with high potency and efficacy. Treatment of cells with convallatoxin enhanced morphine-induced MOR endocytosis through an adaptor protein 2 (AP2)/clathrin-dependent mechanism, attenuated morphine-induced phosphorylation of MOR, and diminished desensitization of membrane hyperpolarization. Furthermore, co-treatment with chronic convallatoxin reduced morphine tolerance in animal models of acute thermal pain and chronic inflammatory pain. Acute convallatoxin administration reversed morphine tolerance and dependence in morphine-tolerant mice. These findings suggest convallatoxin are potentially therapeutic for morphine side effects and open a new avenue to study MOR trafficking.
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Affiliation(s)
- Po-Kuan Chao
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Hsiao-Fu Chang
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Li-Chin Ou
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Jian-Ying Chuang
- The PhD Program for Neural Regenerative Medicine, Taipei Medical University, Taipei, 110, Taiwan
| | - Pin-Tse Lee
- Cellular Pathobiology Section, Intramural Research Program, National Institute on Drug Abuse, NIH/DHHS, Baltimore, MD, 21224, USA
| | - Wan-Ting Chang
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Shu-Chun Chen
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Shau-Hua Ueng
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - John Tsu-An Hsu
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan
| | - Pao-Luh Tao
- Center for Neuropsychiatric Research, National Heath Research Institutes, Zhunan, 35053, Taiwan
| | - Ping-Yee Law
- Department of Pharmacology, Medical School University of Minnesota, Minneapolis, MN, 55455-0217, USA
| | - Horace H Loh
- Department of Pharmacology, Medical School University of Minnesota, Minneapolis, MN, 55455-0217, USA
| | - Shiu-Hwa Yeh
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan, 35053, Taiwan. .,The PhD Program for Neural Regenerative Medicine, Taipei Medical University, Taipei, 110, Taiwan.
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Abstract
Diabetes is a major risk factor for the development of heart failure. One of the hallmarks of diabetes is insulin resistance associated with hyperinsulinemia. The literature shows that insulin and adrenergic signaling is intimately linked to each other; however, whether and how insulin may modulate cardiac adrenergic signaling and cardiac function remains unknown. Notably, recent studies have revealed that insulin receptor and β2 adrenergic receptor (β2AR) forms a membrane complex in animal hearts, bringing together the direct contact between 2 receptor signaling systems, and forming an integrated and dynamic network. Moreover, insulin can drive cardiac adrenergic desensitization via protein kinase A and G protein-receptor kinases phosphorylation of the β2AR, which compromises adrenergic regulation of cardiac contractile function. In this review, we will explore the current state of knowledge linking insulin and G protein-coupled receptor signaling, especially β-adrenergic receptor signaling in the heart, with emphasis on molecular insights regarding its role in diabetic cardiomyopathy.
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Amano T, Shitara Y, Fujii N, Inoue Y, Kondo N. Evidence for β-adrenergic modulation of sweating during incremental exercise in habitually trained males. J Appl Physiol (1985) 2017; 123:182-189. [DOI: 10.1152/japplphysiol.00220.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/20/2017] [Accepted: 05/01/2017] [Indexed: 11/22/2022] Open
Abstract
The aim of the present study was to determine the β-adrenergic contribution to sweating during incremental exercise in habitually trained males. Nine habitually trained and 11 untrained males performed incremental cycling until exhaustion (20 W/min). Bilateral forearm sweat rates (ventilated capsule) were measured at two skin sites that were transdermally administered via iontophoresis with either 1% propranolol (Propranolol, a nonselective β-adrenergic receptor antagonist) or saline (Control). The sweat rate was evaluated as a function of both relative (percentage of maximum workload) and absolute exercise intensities. The sweat rate at the Propranolol site was lower than the control during exercise at 80 (0.57 ± 0.21 and 0.45 ± 0.19 mg·cm−2·min−1 for Control and Propranolol, respectively) and 90% (0.74 ± 0.22 and 0.65 ± 0.17 mg·cm−2·min−1, respectively) of maximum workload in trained males (all P < 0.05). By contrast, no between-site differences in sweat rates were observed in untrained counterparts (all P > 0.05). At the same absolute intensity, higher sweat rates on the control site were observed in trained males relative to the untrained during exercise at 160 (0.23 ± 0.20 and 0.04 ± 0.05 mg·cm−2·min−1 for trained and untrained, respectively) and 180 W (0.40 ± 0.20 and 0.13 ± 0.13 mg·cm−2·min−1, respectively) (all P < 0.05), whereas this between-group difference was not observed at the Propranolol site (all P > 0.05). We show that the β-adrenergic mechanism does modulate sweating during exercise at a submaximal high relative intensity in habitually trained males. The β-adrenergic mechanism may in part contribute to the greater sweat production in habitually trained males than in untrained counterparts during exercise. NEW & NOTEWORTHY We demonstrated for the first time that the β-adrenergic mechanism does modulate sweating (i.e., β-adrenergic sweating) during exercise using a localized β-adrenoceptor blockade in humans in vivo. β-Adrenergic sweating was evident in habitually trained individuals during exercise at a submaximal high relative intensity (80–90% maximal work). This observation advances our understanding of human thermoregulation during exercise and of the mechanism that underlies sweat gland adaptation to habitual exercise training.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Yosuke Shitara
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Naoto Fujii
- Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan; and
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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Davis A, Abraham E, McEvoy E, Sonnenfeld S, Lewis C, Hubbard CS, Dolence EK, Rose JD, Coddington E. Corticosterone suppresses vasotocin-enhanced clasping behavior in male rough-skinned newts by novel mechanisms interfering with V1a receptor availability and receptor-mediated endocytosis. Horm Behav 2015; 69:39-49. [PMID: 25528549 DOI: 10.1016/j.yhbeh.2014.12.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 11/14/2014] [Accepted: 12/11/2014] [Indexed: 12/17/2022]
Abstract
In rough-skinned newts, Taricha granulosa, exposure to an acute stressor results in the rapid release of corticosterone (CORT), which suppresses the ability of vasotocin (VT) to enhance clasping behavior. CORT also suppresses VT-induced spontaneous activity and sensory responsiveness of clasp-controlling neurons in the rostromedial reticular formation (Rf). The cellular mechanisms underlying this interaction remain unclear. We hypothesized that CORT blocks VT-enhanced clasping by interfering with V1a receptor availability and/or VT-induced endocytosis. We administered a physiologically active fluorescent VT conjugated to Oregon Green (VT-OG) to the fourth ventricle 9 min after an intraperitoneal injection of CORT (0, 10, 40 μg/0.1mL amphibian Ringers). The brains were collected 30 min post-VT-OG, fixed, and imaged with confocal microscopy. CORT diminished the number of endocytosed vesicles, percent area containing VT-OG, sum intensity of VT-OG, and the amount of VT-V1a within each vesicle; indicating that CORT was interfering with V1a receptor availability and VT-V1a receptor-mediated endocytosis. CORT actions were brain location-specific and season-dependent in a manner that is consistent with the natural and context-dependent expression of clasping behavior. Furthermore, the sensitivity of the Rf to CORT was much higher in animals during the breeding season, arguing for ethologically appropriate seasonal variation in CORT's ability to prevent VT-induced endocytosis. Our data are consistent with the time course and interaction effects of CORT and VT on clasping behavior and neurophysiology. CORT interference with VT-induced endocytosis may be a common mechanism employed by hormones across taxa for mediating rapid context- and season-specific behavioral responses.
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Affiliation(s)
- Audrey Davis
- Department of Biology, Willamette University, Salem, OR 97301, USA
| | - Emily Abraham
- Department of Biology, Willamette University, Salem, OR 97301, USA
| | - Erin McEvoy
- Department of Biology, Willamette University, Salem, OR 97301, USA
| | - Sarah Sonnenfeld
- Department of Biology, Willamette University, Salem, OR 97301, USA
| | - Christine Lewis
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
| | - Catherine S Hubbard
- Department of Neural & Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA
| | - E Kurt Dolence
- School of Pharmacy, University of Wyoming, Laramie, WY, USA
| | - James D Rose
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
| | - Emma Coddington
- Department of Biology, Willamette University, Salem, OR 97301, USA.
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G protein-coupled receptor accessory proteins and signaling: pharmacogenomic insights. Methods Mol Biol 2014; 1175:121-52. [PMID: 25150869 DOI: 10.1007/978-1-4939-0956-8_7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The identification and characterization of the genes encoding G protein-coupled receptors (GPCRs) and the proteins necessary for the processes of ligand binding, GPCR activation, inactivation, and receptor trafficking to the membrane are discussed in the context of human genetic disease. In addition to functional GPCR variants, the identification of genetic disruptions affecting proteins necessary to GPCR functions have provided insights into the function of these pathways. Gsα and Gβ subunit polymorphisms have been found to result in complex phenotypes. Disruptions in accessory proteins that normally modify or organize heterotrimeric G-protein coupling may also result in disease states. These include the contribution of variants of the regulator of G protein signaling (RGS) protein to hypertension; the role variants of the activator of G protein signaling (AGS) proteins to phenotypes (such as the type III AGS8 variant to hypoxia); the contribution of G protein-coupled receptor kinase (GRK) proteins, such as GRK4, in disorders such as hypertension. The role of accessory proteins in GPCR structure and function is discussed in the context of genetic disorders associated with disruption of the genes that encode them. An understanding of the pharmacogenomics of GPCR and accessory protein signaling provides the basis for examining both GPCR pharmacogenetics and the genetics of monogenic disorders that result from disruption of given receptor systems.
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Cottrell GS. Roles of proteolysis in regulation of GPCR function. Br J Pharmacol 2013; 168:576-90. [PMID: 23043558 DOI: 10.1111/j.1476-5381.2012.02234.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 09/03/2012] [Accepted: 09/24/2012] [Indexed: 12/18/2022] Open
Abstract
The enzymatic activity of peptidases must be tightly regulated to prevent uncontrolled hydrolysis of peptide bonds, which could have devastating effects on biological systems. Peptidases are often generated as inactive propeptidases, secreted with endogenous inhibitors, or they are compartmentalized. Propeptidases become active after proteolytic removal of N-terminal activation peptides by other peptidases. Some peptidases only become active towards substrates only at certain pHs, thus confining activity to specific compartments or conditions. This review discusses the different roles proteolysis plays in regulating GPCRs. At the cell-surface, certain GPCRs are regulated by the hydrolytic inactivation of bioactive peptides by membrane-anchored peptidases, which prevent signalling. Conversely, cell-surface peptidases can also generate bioactive peptides, which directly activate GPCRs. Alternatively, cell-surface peptidases activated by GPCRs, can generate bioactive peptides to cause transactivation of receptor tyrosine kinases, thereby promoting signalling. Certain peptidases can signal directly to cells, by cleaving GPCR to initiate intracellular signalling cascades. Intracellular peptidases also regulate GPCRs; lysosomal peptidases destroy GPCRs in lysosomes to permanently terminate signalling and mediate down-regulation; endosomal peptidases cleave internalized peptide agonists to regulate GPCR recycling, resensitization and signalling; and soluble intracellular peptidases also participate in GPCR function by regulating the ubiquitination state of GPCRs, thereby altering GPCR signalling and fate. Although the use of peptidase inhibitors has already brought success in the treatment of diseases such as hypertension, the discovery of new regulatory mechanisms involving proteolysis that control GPCRs may provide additional targets to modulate dysregulated GPCR signalling in disease.
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Affiliation(s)
- G S Cottrell
- Reading School of Pharmacy, University of Reading, Reading, UK.
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Cho DI, Zheng M, Min C, Kwon KJ, Shin CY, Choi HK, Kim KM. ARF6 and GASP-1 are post-endocytic sorting proteins selectively involved in the intracellular trafficking of dopamine D₂ receptors mediated by GRK and PKC in transfected cells. Br J Pharmacol 2013; 168:1355-74. [PMID: 23082996 PMCID: PMC3596642 DOI: 10.1111/bph.12025] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 09/07/2012] [Accepted: 09/28/2012] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE GPCRs undergo both homologous and heterologous regulatory processes in which receptor phosphorylation plays a critical role. The protein kinases responsible for each pathway are well established; however, other molecular details that characterize each pathway remain unclear. In this study, the molecular mechanisms that determine the differences in the functional roles and intracellular trafficking between homologous and PKC-mediated heterologous internalization pathways for the dopamine D₂ receptor were investigated. EXPERIMENTAL APPROACH All of the S/T residues located within the intracellular loops of D₂ receptor were mutated, and the residues responsible for GRK- and PKC-mediated internalization were determined in HEK-293 cells and SH-SY5Y cells. The functional role of receptor internalization and the cellular components that determine the post-endocytic fate of internalized D₂ receptors were investigated in the transfected cells. KEY RESULTS T134, T225/S228/S229 and S325 were involved in PKC-mediated D₂ receptor desensitization. S229 and adjacent S/T residues mediated the PKC-dependent internalization of D₂ receptors, which induced down-regulation and desensitization. S/T residues within the second intracellular loop and T225 were the major residues involved in GRK-mediated internalization of D₂ receptors, which induced receptor resensitization. ARF6 mediated the recycling of D₂ receptors internalized in response to agonist stimulation. In contrast, GASP-1 mediated the down-regulation of D₂ receptors internalized in a PKC-dependent manner. CONCLUSIONS AND IMPLICATIONS GRK- and PKC-mediated internalizations of D₂ receptors occur through different intracellular trafficking pathways and mediate distinct functional roles. Distinct S/T residues within D₂ receptors and different sorting proteins are involved in the dissimilar regulation of D₂ receptors by GRK2 and PKC.
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Affiliation(s)
- D I Cho
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju, Korea
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Opioid Receptor Trafficking and Signaling: What Happens After Opioid Receptor Activation? Cell Mol Neurobiol 2011; 32:167-84. [DOI: 10.1007/s10571-011-9755-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 09/04/2011] [Indexed: 01/14/2023]
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Dillon PF, Root-Bernstein R, Robinson NE, Abraham WM, Berney C. Receptor-mediated enhancement of beta adrenergic drug activity by ascorbate in vitro and in vivo. PLoS One 2010; 5:e15130. [PMID: 21179213 PMCID: PMC3001466 DOI: 10.1371/journal.pone.0015130] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 10/25/2010] [Indexed: 11/25/2022] Open
Abstract
Rationale Previous in vitro research demonstrated that ascorbate enhances potency and duration of activity of agonists binding to alpha 1 adrenergic and histamine receptors. Objectives Extending this work to beta 2 adrenergic systems in vitro and in vivo. Methods Ultraviolet spectroscopy was used to study ascorbate binding to adrenergic receptor preparations and peptides. Force transduction studies on acetylcholine-contracted trachealis preparations from pigs and guinea pigs measured the effect of ascorbate on relaxation due to submaximal doses of beta adrenergic agonists. The effect of inhaled albuterol with and without ascorbate was tested on horses with heaves and sheep with carbachol-induced bronchoconstriction. Measurements Binding constants for ascorbate binding to beta adrenergic receptor were derived from concentration-dependent spectral shifts. Dose- dependence curves were obtained for the relaxation of pre-contracted trachealis preparations due to beta agonists in the presence and absence of varied ascorbate. Tachyphylaxis and fade were also measured. Dose response curves were determined for the effect of albuterol plus-and-minus ascorbate on airway resistance in horses and sheep. Main Results Ascorbate binds to the beta 2 adrenergic receptor at physiological concentrations. The receptor recycles dehydroascorbate. Physiological and supra-physiological concentrations of ascorbate enhance submaximal epinephrine and isoproterenol relaxation of trachealis, producing a 3–10-fold increase in sensitivity, preventing tachyphylaxis, and reversing fade. In vivo, ascorbate improves albuterol's effect on heaves and produces a 10-fold enhancement of albuterol activity in “asthmatic” sheep. Conclusions Ascorbate enhances beta-adrenergic activity via a novel receptor-mediated mechanism; increases potency and duration of beta adrenergic agonists effective in asthma and COPD; prevents tachyphylaxis; and reverses fade. These novel effects are probably caused by a novel mechanism involving phosphorylation of aminergic receptors and have clinical and drug-development applications.
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Affiliation(s)
- Patrick F. Dillon
- Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America
| | - Robert Root-Bernstein
- Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
| | - N. Edward Robinson
- Department of Large Animal Clinical Science, Michigan State University, East Lansing, Michigan, United States of America
| | - William M. Abraham
- Department of Research, Mount Sinai Medical Center, Miami Beach, Florida, United States of America
| | - Catherine Berney
- Department of Large Animal Clinical Science, Michigan State University, East Lansing, Michigan, United States of America
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Is the lifetime of light-stimulated cGMP phosphodiesterase regulated by recoverin through its regulation of rhodopsin phosphorylation? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00039522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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18
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19
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20
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21
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22
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23
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24
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Targeted transgenesis reveals discrete attenuator functions of GRK and PKA in airway beta2-adrenergic receptor physiologic signaling. Proc Natl Acad Sci U S A 2009; 106:15007-12. [PMID: 19706446 DOI: 10.1073/pnas.0906034106] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Phosphorylation by protein kinase A (PKA) and G protein-coupled receptor kinases (GRKs) desensitize beta2-adrenergic receptor (beta2AR) signaling, and these are thought to be mechanisms involved with cell and organ homeostasis and tolerance to agonists. However, there is little direct evidence that these events are relevant to beta2AR physiological function, such as airway smooth muscle (ASM) relaxation leading to bronchodilation. To maintain cell- and receptor-specificity without altering the natural complement of kinases/arrestins, transgenic mice were generated expressing the human WT and mutated beta2ARs lacking PKA and/or GRK phosphorylation sites on ASM at approximately 4-fold over background. Functional gains in response to beta-agonist from the selective loss of these mechanisms were determined in mouse airways. Relaxation kinetics were altered in all mutant airways compared with beta2WT. At low receptor occupancy, beta2PKA(-) had enhanced agonist-promoted relaxation, while beta2GRK(-) airways were unaffected. In contrast, at saturating agonist concentrations, the greatest relaxation enhancement was with beta2GRK(-), with no evidence for additivity when PKA sites were also removed. For the full range of responses, the beta2PKA(-)/GRK(-) airways had the greatest relaxation efficiency, indicating a graded effect of GRKs as agonist concentration increased. ASM cAMP levels paralleled relaxation phenotypes. No interaction between PKA phosphorylation of beta2AR and GRK-promoted events was identified by beta-arrestin-2 recruitment. Thus, these two mechanisms indeed impact a relevant beta2AR physiologic function, acting as attenuators of the acute response, and represent specific interfaces where adjunct therapy or biased ligands may improve beta-agonist treatment of obstructive lung disease.
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Abstract
Development of therapeutic measures to reduce the risk of potentially fatal episodes of hypoglycaemia and thus to achieve the full benefits of intensive insulin therapy in diabetic patients requires a complete understanding of the multi-factorial mechanisms for repeated hypoglycaemia-induced blunting of the sympatho-adrenal response (BSAR). After critical analysis of the hypotheses, this review paper suggests a heuristic theory. This theory suggests two mechanisms for the BSAR, each involving a critical role for the central brain noradrenergic system. Furthermore, this theory also suggests that the lateral hypothalamus (LH) plays an important role in this phenomenon. Within the framework of this theory, explanations for 1) sexual dimorphism in the adrenomedullary response (AR), 2) dissociation in the blunting of the AR and the sympathetic response (SR) and 3) antecedent exercise-induced blunting of the AR are provided. In addition, habituation of orexin-A neurons is suggested to cause defective awakening. Moreover, potential therapeutics measures have been also suggested that will reduce or prevent severe episodes of hypoglycaemia.
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Affiliation(s)
- B Parekh
- Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
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26
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Callander GE, Thomas WG, Bathgate RAD. Prolonged RXFP1 and RXFP2 signaling can be explained by poor internalization and a lack of beta-arrestin recruitment. Am J Physiol Cell Physiol 2009; 296:C1058-66. [PMID: 19279230 DOI: 10.1152/ajpcell.00581.2008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Relaxin induces sustained physiological responses, which brings into question the deactivation processes typical of most G protein-coupled receptors (GPCR) for its receptor, relaxin family peptide receptor 1 (RXFP1). Here, we examined relaxin-dependent phosphorylation of RXFP1 and the related insulin-like peptide 3 (INSL3) receptor, RXFP2, as well as the capacity of these receptors to recruit beta-arrestins and internalize in response to ligand stimulation. We confirmed in human embryonic kidney (HEK)-293T cells, expressing RXFP1 or RXFP2, that both receptors elicit prolonged cAMP responses up to 6 h after stimulation. Receptors immunoprecipitated from (32)P metabolically labeled cells were used to investigate the agonist-specific phosphorylation. Rapid and robust receptor phosphorylation was not observed for either RXFP1 or RXFP2, although some (32)P-incorporation was observed at 30 min; however, this was not statistically significant. In accord with this result, RXFP1 and RXFP2 demonstrated poor internalization in response to relaxin or INSL3, as compared with the angiotensin II type 1 receptor (AT(1)R), which undergoes rapid and robust phosphorylation and internalization in response to angiotensin II. Additionally, coexpression of GPCR kinases has no effect on the rate of internalization for either RXFP1 or RXFP2. Confocal microscopy was used to follow the trafficking of green fluorescent protein-labeled beta-arrestins after receptor activation. Neither RXFP1 nor RXFP2 activation results in recruitment of beta-arrestins to the cell surface, whereas AT(1)R rapidly recruits both beta-arrestins-1 and -2. The apparent lack of classical regulation for RXFP1 and RXFP2 provides the molecular basis for the prolonged signaling and physiological actions of relaxin and related peptides.
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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.
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Affiliation(s)
- Matthew D Bruss
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California 94143, USA
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Hendrix S, Picker B, Liezmann C, Peters EMJ. Skin and hair follicle innervation in experimental models: a guide for the exact and reproducible evaluation of neuronal plasticity. Exp Dermatol 2008; 17:214-27. [PMID: 18261087 DOI: 10.1111/j.1600-0625.2007.00653.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The remodelling of skin innervation is an instructive example of neuronal plasticity in the peripheral nervous system. Cutaneous innervation displays dramatic plasticity during morphogenesis, adult remodelling, skin diseases and after skin nerve lesions. To recognize even subtle changes or abnormalities of cutaneous innervation under different experimental conditions, it is critically important to use a quantitative approach. Here, we introduce a simple, fast and reproducible quantitative method based on immunofluorescence histochemistry for the exact quantification of peripheral nerve fibres. Computer-generated schematic representations of cutaneous innervation in defined skin compartments are presented with the aim of standardizing reports on gene and protein expression patterns. This guide should become a useful tool when screening new mouse mutants, disease models affecting innervation or mice treated with pharmaceuticals for discrete morphologic abnormalities of skin innervation in a highly reproducible and quantifiable manner. Moreover, this method can be easily transferred to other densely innervated peripheral organs.
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Affiliation(s)
- Sven Hendrix
- Institute for Cell Biology and Neurobiology, Center for Anatomy, Charité-Universitätsmedizin, Berlin, Germany
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29
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Optical techniques to analyze real-time activation and signaling of G-protein-coupled receptors. Trends Pharmacol Sci 2008; 29:159-65. [PMID: 18262662 DOI: 10.1016/j.tips.2007.12.002] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 12/14/2007] [Accepted: 12/17/2007] [Indexed: 12/29/2022]
Abstract
The activation of G-protein-coupled receptors (GPCRs) is traditionally measured either by monitoring downstream physiological events or by membrane-based biochemical assays. Neither of these approaches permits detailed kinetic or spatial analysis of receptor activation and signaling. Recently, several optical techniques have been developed to monitor receptor activation either by using purified reconstituted GPCRs or by observing GPCRs, G proteins and second messengers in intact cells. These techniques are providing, literally, new views on both the mechanistic basis of the signaling process and the kinetic and spatial properties of GPCR-mediated signals. They suggest that agonists can activate GPCRs within milliseconds, that different compounds can induce distinct active conformations of GPCRs, that G-protein activation is the rate-limiting step in GPCR signaling, and that cellular signals can be temporally and spatially confined. They are also raising controversial issues, such as whether or not receptors and G proteins are pre-coupled and whether G proteins dissociate during activation.
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30
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Abstract
Almost all G-protein coupled receptors (GPCRs) are regulated by phosphorylation and this process is a key event in determining the signalling properties of this receptor super-family. Receptors are multiply phosphorylated at sites that can occur throughout the intracellular regions of the receptor. This diversity of phospho-acceptor sites together with a lack of consensus phosphorylation sequences has led to the suggestion that the precise site of phosphorylation is not important in the phosphorylation-dependent regulation of GPCR function but rather it is the increase in bulk negative charge of the intracellular face of the receptor which is the significant factor. This review investigates the possibility that the multi-site nature of GPCR phosphorylation reflects the importance of specific phosphorylation events which mediate distinct signalling outcomes. In this way receptor phosphorylation may provide for a flexible regulatory mechanism that can be tailored in a tissue specific manner to regulate physiological processes. By understanding the flexible nature of GPCR phosphorylation if may be possible to develop agonists or allosteric modulators that promote a subset of phosphorylation events on the target GPCR and thereby restrict the action of the drug to a particular receptor mediated signalling response.
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31
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Thompson MD, Cole DEC, Jose PA. Pharmacogenomics of G protein-coupled receptor signaling: insights from health and disease. Methods Mol Biol 2008; 448:77-107. [PMID: 18370232 DOI: 10.1007/978-1-59745-205-2_6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The identification and characterization of the processes of G protein-coupled receptor (GPCR) activation and inactivation have refined not only the study of the GPCRs but also the genomics of many accessory proteins necessary for these processes. This has accelerated progress in understanding the fundamental mechanisms involved in GPCR structure and function, including receptor transport to the membrane, ligand binding, activation and inactivation by GRK-mediated (and other) phosphorylation. The catalog of G(s)alpha and Gbeta subunit polymorphisms that result in complex phenotypes has complemented the effort to catalog the GPCRs and their variants. The study of the genomics of GPCR accessory proteins has also provided insight into pathways of disease, such as the contributions of regulator of G protein signaling (RGS) protein to hypertension and activator of G protein signaling (AGS) proteins to the response to hypoxia. In the case of the G protein-coupled receptor kinases (GRKs), identified originally in the retinal tissues that converge on rhodopsin, proteins such as GRK4 have been identified that have been subsequently associated with hypertension. Here, we review the structure and function of GPCR and associated proteins in the context of the gene families that encode them and the genetic disorders associated with their altered function. An understanding of the pharmacogenomics of GPCR signaling provides the basis for examining the GPCRs disrupted in monogenic disease and the pharmacogenetics of a given receptor system.
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Affiliation(s)
- Miles D Thompson
- Department of Laboratory Medicine and Pathobiology, Banting Institute, University of Toronto, Toronto, Ontario, Canada
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32
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Self TJ, Oakley SM, Hill SJ. Clathrin-independent internalization of the human histamine H1-receptor in CHO-K1 cells. Br J Pharmacol 2006; 146:612-24. [PMID: 16086035 PMCID: PMC1751180 DOI: 10.1038/sj.bjp.0706337] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The aim of the present study was to investigate the cellular pathway involved in histamine-stimulated internalization of the human H1-receptor in CHO-K1 cells expressing N-terminal myc-tagged H1-receptor (Myc-H1) or N-terminal myc-C-terminal green fluorescent protein (Myc-GFP H1) versions of the receptor. Studies of 3H-mepyramine binding and histamine-stimulated 3H-inositol phosphate accumulation in these cells showed that the Myc-H1 and Myc-GFP H1-receptors had identical pharmacology to the wild-type H1-receptor. The Myc-H1-receptor was rapidly internalized in CHO-K1 cells following stimulation with histamine (0.1 mM). This response occurred within 15 min, and could be prevented by the quaternary H1-receptor antagonist alpha-pirdonium. Similar data were obtained with the Myc-GFP H1-receptors. Internalization of the Myc-GFP H1-receptor was maintained in the absence of extracellular calcium and was not inhibited by the CAM kinase II inhibitor KN-62 (10 microM). Phorbol dibutyrate, an activator of protein kinase C, was also able to stimulate internalization of the H1-receptor. However, inhibition or downregulation of protein kinase C (which significantly modified histamine-stimulated inositol phosphate responses) was without effect on the internalization of the H1-receptor stimulated by histamine. Hypertonic sucrose did not prevent histamine-induced internalization of the Myc-GFP H1-receptor, but was able to attenuate internalization of transferrin via clathrin-mediated endocytosis in the same cells. In contrast, preincubation of cells with filipin or nystatin, which disrupts caveolae and lipid rafts, completely inhibited the histamine-induced internalization of the Myc-GFP H1-receptor, but was without effect on the sequestration of transferrin. The H1-receptor and cholera toxin subunit B were colocalized under resting conditions at the cell surface. Immunohistochemical studies with an antibody to caveolin-1 confirmed that this protein was also localized predominantly to the plasma membrane. However, following stimulation of CHO-Myc-GFP H1 cells with histamine, there was no evidence for internalization of caveolin-1 in parallel with the H1-receptor. These data provide strong evidence that the H1-receptor is internalized via a clathrin-independent mechanism and most likely involves lipid rafts.
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Affiliation(s)
- Timothy J Self
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
| | - Sarah M Oakley
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
| | - Stephen J Hill
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH
- Author for correspondence:
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33
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Bailey CP, Smith FL, Kelly E, Dewey WL, Henderson G. How important is protein kinase C in μ-opioid receptor desensitization and morphine tolerance? Trends Pharmacol Sci 2006; 27:558-65. [PMID: 17000011 DOI: 10.1016/j.tips.2006.09.006] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Revised: 08/21/2006] [Accepted: 09/12/2006] [Indexed: 11/30/2022]
Abstract
The repeated administration of opiate drugs such as morphine results in the development of tolerance to their analgesic, rewarding (euphoric) and respiratory-depressant effects; thus, to obtain the same level of response with subsequent administrations, a greater dose must be used. Tolerance can limit the clinical efficacy of opiate drugs and enhance the social problems that are inherent in recreational opioid abuse. Surprisingly, the mechanism (or mechanisms) underlying the development of morphine tolerance remains controversial. Here, we propose that protein kinase C could have a crucial role in the desensitization of mu-opioid receptors by morphine and that this cellular process could contribute to the development and maintenance of morphine tolerance in vivo.
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Affiliation(s)
- Chris P Bailey
- Department of Pharmacology, University of Bristol, Bristol BS8 1TD, UK
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34
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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.
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35
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Thompson MD, Burnham WM, Cole DEC. The G protein-coupled receptors: pharmacogenetics and disease. Crit Rev Clin Lab Sci 2005; 42:311-92. [PMID: 16281738 DOI: 10.1080/10408360591001895] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Genetic variation in G-protein coupled receptors (GPCRs) is associated with a wide spectrum of disease phenotypes and predispositions that are of special significance because they are the targets of therapeutic agents. Each variant provides an opportunity to understand receptor function that complements a plethora of available in vitro data elucidating the pharmacology of the GPCRs. For example, discrete portions of the proximal tail of the dopamine D1 receptor have been discovered, in vitro, that may be involved in desensitization, recycling and trafficking. Similar in vitro strategies have been used to elucidate naturally occurring GPCR mutations. Inactive, over-active or constitutively active receptors have been identified by changes in ligand binding, G-protein coupling, receptor desensitization and receptor recycling. Selected examples reviewed include those disorders resulting from mutations in rhodopsin, thyrotropin, luteinizing hormone, vasopressin and angiotensin receptors. By comparison, the recurrent pharmacogenetic variants are more likely to result in an altered predisposition to complex disease in the population. These common variants may affect receptor sequence without intrinsic phenotype change or spontaneous induction of disease and yet result in significant alteration in drug efficacy. These pharmacogenetic phenomena will be reviewed with respect to a limited sampling of GPCR systems including the orexin/hypocretin system, the beta2 adrenergic receptors, the cysteinyl leukotriene receptors and the calcium-sensing receptor. These developments will be discussed with respect to strategies for drug discovery that take into account the potential for the development of drugs targeted at mutated and wild-type proteins.
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Affiliation(s)
- Miles D Thompson
- Department of Laboratory Medicine and Pathobiology, Banting Institute, University of Toronto, ON, Canada.
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36
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Heijink IH, Vellenga E, Oostendorp J, de Monchy JGR, Postma DS, Kauffman HF. Exposure to TARC alters beta2-adrenergic receptor signaling in human peripheral blood T lymphocytes. Am J Physiol Lung Cell Mol Physiol 2005; 289:L53-9. [PMID: 15749741 DOI: 10.1152/ajplung.00357.2004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The beta(2)-adrenergic receptor (beta(2)-AR) negatively regulates T cell activity through the activation of the G(s)/adenylyl cyclase/cAMP pathway. beta(2)-AR desensitization, which can be induced by its phosphorylation, may have important consequences for the regulation of T cell function in asthma. In the present study we demonstrate that the C-C chemokine thymus and activation-regulated chemokine (TARC) impairs the ability of beta(2)-agonist fenoterol to activate the cAMP downstream effector cAMP-responsive element binding protein (CREB) in freshly isolated human T cells. The TARC-induced activation of Src kinases resulted in membrane translocation of both G protein-coupled receptor kinase (GRK) 2 and beta-arrestin. Moreover, TARC was able to induce Src-dependent serine phosphorylation of the beta(2)-AR as well as its association with GRK2 and beta-arrestin. Finally, in contrast to CREB, phosphorylation of Src and extracellular signal-regulated kinase was enhanced by fenoterol upon TARC pretreatment. In summary, we show for the first time that TARC exposure impairs beta(2)-AR function in T cells. Our data suggest that this is mediated by Src-dependent activation of GRK2, resulting in receptor phosphorylation, binding to beta-arrestin, and a switch from cAMP-dependent signaling to activation of the MAPK pathway. We propose that aberrant T cell control in the presence of endogenous beta-agonists promotes T cell-mediated inflammation in asthma.
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Affiliation(s)
- Irene H Heijink
- Department of Allergology, University Medical Center Groningen, The Netherlands
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37
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Prasanna G, Narayan S, Krishnamoorthy RR, Yorio T. Eyeing endothelins: a cellular perspective. Mol Cell Biochem 2004; 253:71-88. [PMID: 14619958 DOI: 10.1023/a:1026005418874] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Endothelin is an endogenous vasoactive peptide that is considered among the most potent vasoconstrictor substances known. In addition to its vascular effects, endothelins and their receptors have been shown to be present in the eye and to have a number of ocular actions that may be important for ocular homeostasis, but, in excess can be a potential contributor to ocular neuropathy in glaucoma. The current review focuses on the cellular and molecular aspects of endothelins and its receptors in the eye with an emphasis on its relationship to ocular function and its potential role in the etiology of glaucoma pathophysiology.
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Affiliation(s)
- Ganesh Prasanna
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, USA
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38
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Rapacciuolo A, Suvarna S, Barki-Harrington L, Luttrell LM, Cong M, Lefkowitz RJ, Rockman HA. Protein kinase A and G protein-coupled receptor kinase phosphorylation mediates beta-1 adrenergic receptor endocytosis through different pathways. J Biol Chem 2003; 278:35403-11. [PMID: 12821660 DOI: 10.1074/jbc.m305675200] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Agonist-induced phosphorylation of beta-adrenergic receptors (beta ARs) by G protein-coupled receptor kinases (GRKs) results in their desensitization followed by internalization. Whether protein kinase A (PKA)-mediated phosphorylation of beta ARs, particularly the beta 1AR subtype, can also trigger internalization is currently not known. To test this, we cloned the mouse wild type beta 1AR (WT beta 1AR) and created 3 mutants lacking, respectively: the putative PKA phosphorylation sites (PKA-beta 1AR), the putative GRK phosphorylation sites (GRK-beta 1AR), and both sets of phosphorylation sites (PKA-/GRK-beta 1AR). Following agonist stimulation, both PKA-beta 1AR and GRK-beta 1AR mutants showed comparable increases in phosphorylation and desensitization. Saturating concentrations of agonist induced only 50% internalization of either mutant compared with wild type, suggesting that both PKA and GRK phosphorylation of the receptor contributed to receptor sequestration in an additive manner. Moreover, in contrast to the WT beta 1AR and PKA-beta 1AR, sequestration of the GRK-beta 1AR and PKA-/GRK-beta 1AR was independent of beta-arrestin recruitment. Importantly, clathrin inhibitors abolished agonist-dependent internalization for both the WT beta 1AR and PKA-beta 1AR, whereas caveolae inhibitors prevented internalization only of the GRK-beta 1AR mutant. Taken together, these data demonstrate that: 1) PKA-mediated phosphorylation can trigger agonist-induced internalization of the beta 1AR and 2) the pathway selected for beta 1AR internalization is primarily determined by the kinase that phosphorylates the receptor, i.e. PKA-mediated phosphorylation directs internalization via a caveolae pathway, whereas GRK-mediated phosphorylation directs it through clathrin-coated pits.
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MESH Headings
- Animals
- Binding Sites
- Cell Line
- Cloning, Molecular
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Dobutamine/pharmacology
- Endocytosis/physiology
- GTP-Binding Proteins/physiology
- Humans
- Mice
- Models, Molecular
- Phosphorylation
- Protein Structure, Secondary
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/physiology
- Recombinant Proteins/metabolism
- Sequence Deletion
- Transfection
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Affiliation(s)
- Antonio Rapacciuolo
- Department of Medicine and Cell Biology, Medical Center, Duke University, Durham, North Carolina 27710, USA
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39
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Schutzer WE, Mader SL. Age-related changes in vascular adrenergic signaling: clinical and mechanistic implications. Ageing Res Rev 2003; 2:169-90. [PMID: 12605959 DOI: 10.1016/s1568-1637(02)00063-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A large and growing segment of the general population are age 65 or older, and this percentage will continue to rise. Primary care of this population has, and is becoming a priority for clinicians. Hypertension, orthostatic hypotension, arterial insufficiency, and atherosclerosis are common disorders in the elderly that lead to significant morbidity and mortality. One common factor to these conditions is an age-related decline in beta-adrenergic receptor (beta-AR)-mediated function and subsequent cAMP generation. Presently, there is no single cellular factor that can explain this age-related decline, and thus the primary cause of this homeostatic imbalance is yet to be identified. However, the etiology is clearly associated with an age-related change in the ability of beta-AR receptor to respond to agonist at the cellular level. This article will review what is presently understood regarding the molecular and biochemical basis of age-impaired beta-AR receptor-mediated signaling. A fundamental understanding of why beta-AR-mediated vasorelaxation is impaired with age will provide new insights and innovative strategies for the management of the multiple clinical disorders that effect older people.
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Affiliation(s)
- William E Schutzer
- Research Service, Portland VA Medical Center and School of Medicine, Oregon Health & Science University, PO Box 1034, Portland, OR 97201, USA
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40
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Pollok-Kopp B, Schwarze K, Baradari VK, Oppermann M. Analysis of ligand-stimulated CC chemokine receptor 5 (CCR5) phosphorylation in intact cells using phosphosite-specific antibodies. J Biol Chem 2003; 278:2190-8. [PMID: 12403770 DOI: 10.1074/jbc.m209844200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human CC chemokine receptor 5 (CCR5), a member of the superfamily of G protein-coupled receptors, regulates the activation and directed migration of leukocytes and serves as the main coreceptor for the entry of R5 tropic strains of human immunodeficiency viruses. We have previously shown that RANTES/CCL5 binding to CCR5 induces GPCR kinase (GRK)- and protein kinase C (PKC)-mediated phosphorylation of four distinct C-terminal serine residues. To study these phosphorylation events in vivo, we have generated monoclonal antibodies, which specifically react only with either phosphorylated or nonphosphorylated CCR5. These phosphosite-specific antibodies reveal that following ligand stimulation of the receptor serine 337 is exclusively phosphorylated by a PKC-mediated mechanism, while GRKs phosphorylate serine 349. GRK-mediated receptor phosphorylation proceeds in a regular time-dependent manner (t(12) approximately 2 min) with an apparent EC(50) of 5 nm. In contrast, PKC phosphorylates serine 337 at 50-fold lower concentrations and in a very rapid, albeit transient manner. Protein phosphatases that are active at neutral pH and are inhibited by okadaic acid rapidly dephosphorylate phosphoserine 337, but less efficiently phosphoserine 349, in intact cells and in an in vitro assay. Immunofluorescence microscopy demonstrates that phosphorylated receptors accumulate in a perinuclear compartment, which resembles recycling endosomes. This study is the first to analyze in detail the spatial and temporal dynamics of GRK- versus PKC-mediated phosphorylation of a G protein-coupled receptor and its subsequent dephosphorylation on the level of individual phosphorylation sites.
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Kohout TA, Lefkowitz RJ. Regulation of G protein-coupled receptor kinases and arrestins during receptor desensitization. Mol Pharmacol 2003; 63:9-18. [PMID: 12488531 DOI: 10.1124/mol.63.1.9] [Citation(s) in RCA: 307] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Affiliation(s)
- Trudy A Kohout
- The Howard Hughes Medical Institute and the Departments of Medicine and Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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42
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Hanania NA, Sharafkhaneh A, Barber R, Dickey BF. Beta-agonist intrinsic efficacy: measurement and clinical significance. Am J Respir Crit Care Med 2002; 165:1353-8. [PMID: 12016095 DOI: 10.1164/rccm.2109060] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Nicola A Hanania
- Section of Pulmonary and Critical Care Medicine, Department of Medicine, Baylor College of Medicine and the Houston Veterans Administration Medical Center, Texas 77030, USA.
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43
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Cheng KW, Leung PCK. The expression, regulation and signal transduction pathways of the mammalian gonadotropin-releasing hormone receptor. Can J Physiol Pharmacol 2000. [DOI: 10.1139/y00-096] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Normal mammalian sexual maturation and reproductive functions require the integration and precise coordination of hormones at the hypothalamic, pituitary, and gonadal levels. Hypothalamic gonadotropin-releasing hormone (GnRH) is a key regulator in this system; after binding to its receptor (GnRHR), it stimulates de novo synthesis and release of gonadotropins in anterior pituitary gonadotropes. Since the isolation of the GnRHR cDNA, the expression of GnRHR mRNA has been detected not only in the pituitary, but also in extrapituitary tissues, including the ovary and placenta. It has been shown that change in GnRHR mRNA is one of the mechanisms for regulating the expression of the GnRHR. To help understand the molecular mechanism(s) involved in transcriptional regulation of the GnRHR gene, the 5' flanking region of the GnRHR gene has recently been isolated. Initial characterization studies have identified several DNA regions in the GnRHR 5' flanking region which are responsible for both basal expression and GnRH-mediated homologous regulation of this gene in pituitary cells. The mammalian GnRHR lacks a C-terminus and possesses a relatively short third intracellular loop; both features are important in desensitization of many others G-protein coupled receptors (GPCRs), Homologous desensitization of GnRHR has been shown to be regulated by various serine-threonine protein kinases including protein kinase A (PKA) and protein kinase C (PKC), as well as by G-protein coupled receptor kinases (GRKs). Furthermore, GnRHR was demonstrated to couple with multiple G proteins (Gq/11, Gs, and Gi), and to activate cascades that involved the PKC, PKA, and mitogen-activator protein kinases. These results suggest the diversity of GnRHR-G protein coupling and signal transduction systems. The identification of second form of GnRH (GnRH-II) in mammals adds to the complexity of the GnRH-GnRHR system. This review summaries our recent progress in understanding the regulation of GnRHR gene expression and the GnRHR signal transduction pathways.Key words: gonadotropin-releasing hormone receptor, transcriptional regulation, desensitization, signal transduction.
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Abstract
Understanding of the pathophysiology of chronic systolic heart failure evolved from a purely mechanical model to one in which a cascade of neurohormones and biologically active molecules are thought to be critical in the development, maintenance, and progression of the disease. Two important neurohormonal systems are the sympathetic nervous and renin-angiotensin-aldosterone systems. Initially, increases in norepinephrine concentrations from the sympathetic nervous system and in angiotensin II and aldosterone are beneficial in the short term to maintain cardiac output after an insult to the myocardium. However, long-term exposure to these neurohormones causes alterations of myocytes and interstitial make-up of the heart. These alterations in myocardium lead to progression of heart failure and, eventually, death.
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Affiliation(s)
- B E Bleske
- University of Michigan College of Pharmacy, University of Michigan Health Systems, Ann Arbor 48109-1065, USA
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de Vries B, Meurs H, Roffel AF, Elzinga CR, Hoiting BH, de Vries MM, Zaagsma J. Beta-agonist-induced constitutive beta(2)-adrenergic receptor activity in bovine tracheal smooth muscle. Br J Pharmacol 2000; 131:915-20. [PMID: 11053211 PMCID: PMC1572420 DOI: 10.1038/sj.bjp.0703664] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
According to the two state receptor model, the beta(2)-adrenergic receptor (beta(2)-AR) isomerizes between an inactive state and a constitutively active state, which couples to the stimulatory G-protein in the absence of agonist. In bovine tracheal smooth muscle (BTSM), we investigated the effect of short and long term beta(2)-AR activation by fenoterol on constitutive receptor activity. Preincubation of the BTSM strips for 5 min, 30 min and 18 h with 10 microM fenoterol, followed by extensive washout (3 h, 37 degrees C), caused a rapid and time-dependent inhibition of KCl-induced contraction, reaching 68+/-10, 51+/-6 and 46+/-4% of control, respectively, at 40 mM KCl (P:<0.05 all). At all time points, the EC(50) values to KCl were significantly reduced as well. Preincubation of BTSM with 0.1, 1.0 and 10 microM fenoterol during 18 h caused a concentration-dependent decrease of the 40 mM KCl response to 70+/-5, 47+/-12 and 43+/-9% of control, respectively (P:<0.05 all). The reduced KCl contractions were reversed in the presence of 1 microM timolol. Moreover, the sensitivity to KCl in the presence of timolol was enhanced after fenoterol incubation. Inverse agonism was also found for other beta-blockers, with a rank order of efficacy of pindolol >/=timolol=propranolol>alprenolol>/=sotalol>labetalol. At 25 mM KCl-induced tone, the contraction induced by cumulative timolol administration was competitively antagonized by the less efficacious inverse agonist labetalol, indicating that the fenoterol-induced effects cannot be explained by residual beta-agonist binding. In conclusion, fenoterol treatment of BTSM causes a time- and concentration-dependent development of constitutive beta(2)-AR activity, which can be reversed by various inverse agonists. The beta-agonist-induced changes could represent a novel regulation mechanism of beta(2)-AR activity.
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Affiliation(s)
- B de Vries
- Department of Molecular Pharmacology, University Centre for Pharmacy, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Tiruppathi C, Yan W, Sandoval R, Naqvi T, Pronin AN, Benovic JL, Malik AB. G protein-coupled receptor kinase-5 regulates thrombin-activated signaling in endothelial cells. Proc Natl Acad Sci U S A 2000; 97:7440-5. [PMID: 10861009 PMCID: PMC16564 DOI: 10.1073/pnas.97.13.7440] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We studied the function of G protein-coupled receptor kinases (GRKs) in the regulation of thrombin-activated signaling in endothelial cells. GRK2, GRK5, and GRK6 isoforms were expressed predominantly in endothelial cells. The function of these isoforms was studied by expressing wild-type and dominant negative (dn) mutants in endothelial cells. We determined the responses to thrombin, which activates intracellular signaling in endothelial cells by cleaving the NH(2) terminus of the G protein-coupled proteinase-activated receptor-1 (PAR-1). We measured changes in phosphoinositide hydrolysis and intracellular Ca(2+) concentration ([Ca(2+)](i)) in response to thrombin as well as the state of endothelial activation. In the latter studies, the transendothelial monolayer electrical resistance, a measure of the loss of endothelial barrier function, was measured in real time. Of the three isoforms, GRK5 overexpression was selective in markedly reducing the thrombin-activated phosphoinositide hydrolysis and increased [Ca(2+)](i). GRK5 overexpression also inhibited the thrombin-induced decrease in endothelial monolayer resistance by 75%. These effects of GRK5 overexpression occurred in association with the specific increase in the thrombin-induced phosphorylation of PAR-1. In contrast to the effects of GRK5 overexpression, the expression of the dn-GRK5 mutant produced a long-lived increase in [Ca(2+)](i) in response to thrombin, whereas dn-GRK2 had no effect. These results indicate the crucial role of the GRK5 isoform in the mechanism of thrombin-induced desensitization of PAR-1 in endothelial cells.
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Affiliation(s)
- C Tiruppathi
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, IL 60612, USA.
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Abstract
Since we have recently shown that the beta 2-adrenoreceptor (beta 2-AR) expression of selected regions of the hair follicle (HF) epithelium as well as the number of adrenergic nerve fibers in murine skin change in a hair cycle-dependent manner, this has raised the possibility that adrenergic nerves may exert "trophic" functions during HF cycling. To further explore this concept, we have investigated the effect of neuro-pharmacological manipulations on hair growth (anagen) induction in quiescent telogen mouse skin in vivo. Here, we demonstrate that subcutaneous injections of the noradrenaline (NA)-depleting agent guanethidine, or of the neurotoxin 6-hydroxydopamine, but not of the beta 2-AR agonist isoproterenol induce a premature onset of anagen in the lower back skin of C57BL/6 mice. On day 20 after the start of treatment, more than 80% of the guanethidine-treated mice and ca. 65% of the 6-hydroxydopamine-treated (6-OHDA) mice exhibited premature skin darkening and hair growth at the site of drug application, whereas less than one-third of all control animals showed macroscopic signs of anagen development. This was confirmed by histology, demonstrating mature anagen VI HFs only at the immediate site of treatment with guanethidine or 6-OHDA as opposed to resting telogen HFs in the neighboring untreated skin area. This observation further supports the concept that sympathetic nerves are intimately involved in hair growth control and invites one to explore the neuro-pharmacological manipulation of piloneural interactions as a novel therapeutic strategy for the management of hair growth disorders.
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Affiliation(s)
- E M Peters
- Department of Dermatology, Charité, Humboldt-Universität zu Berlin, Germany
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Abstract
G-protein coupled receptors (GPCRs) comprise one of the largest classes of signalling molecules. A wide diversity of activating ligands induce the active conformation of GPCRs and lead to signalling via heterotrimeric G-proteins and downstream effectors. In addition, a complex series of reactions participate in the 'turn-off' of GPCRs in both physiological and pharmacological settings. Some key players in the inactivation or 'desensitization' of GPCRs have been identified, whereas others remain the target of ongoing studies. G-protein coupled receptor kinases (GRKs) specifically phosphorylate activated GPCRs and initiate homologous desensitization. Uncoupling proteins, such as members of the arrestin family, bind to the phosphorylated and activated GPCRs and cause desensitization by precluding further interactions of the GPCRs and G-proteins. Adaptor proteins, including arrestins, and endocytic machinery participate in the internalization of GPCRs away from their normal signalling milieu. In this review we discuss the roles of these regulatory molecules as modulators of GPCR signalling.
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Affiliation(s)
- M Bünemann
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue S215, Chicago, IL 60611, USA
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Zhang J, Barak LS, Anborgh PH, Laporte SA, Caron MG, Ferguson SS. Cellular trafficking of G protein-coupled receptor/beta-arrestin endocytic complexes. J Biol Chem 1999; 274:10999-1006. [PMID: 10196181 DOI: 10.1074/jbc.274.16.10999] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta-Arrestins are multifunctional proteins identified on the basis of their ability to bind and uncouple G protein-coupled receptors (GPCR) from heterotrimeric G proteins. In addition, beta-arrestins play a central role in mediating GPCR endocytosis, a key regulatory step in receptor resensitization. In this study, we visualize the intracellular trafficking of beta-arrestin2 in response to activation of several distinct GPCRs including the beta2-adrenergic receptor (beta2AR), angiotensin II type 1A receptor (AT1AR), dopamine D1A receptor (D1AR), endothelin type A receptor (ETAR), and neurotensin receptor (NTR). Our results reveal that in response to beta2AR activation, beta-arrestin2 translocation to the plasma membrane shares the same pharmacological profile as described for receptor activation and sequestration, consistent with a role for beta-arrestin as the agonist-driven switch initiating receptor endocytosis. Whereas redistributed beta-arrestins are confined to the periphery of cells and do not traffic along with activated beta2AR, D1AR, and ETAR in endocytic vesicles, activation of AT1AR and NTR triggers a clear time-dependent redistribution of beta-arrestins to intracellular vesicular compartments where they colocalize with internalized receptors. Activation of a chimeric AT1AR with the beta2AR carboxyl-terminal tail results in a beta-arrestin membrane localization pattern similar to that observed in response to beta2AR activation. In contrast, the corresponding chimeric beta2AR with the AT1AR carboxyl-terminal tail gains the ability to translocate beta-arrestin to intracellular vesicles. These results demonstrate that the cellular trafficking of beta-arrestin proteins is differentially regulated by the activation of distinct GPCRs. Furthermore, they suggest that the carboxyl-tail of the receptors might be involved in determining the stability of receptor/betaarrestin complexes and cellular distribution of beta-arrestins.
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Affiliation(s)
- J Zhang
- Howard Hughes Medical Institute Laboratories, Departments of Cell Biology and Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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50
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Oppermann M, Mack M, Proudfoot AE, Olbrich H. Differential effects of CC chemokines on CC chemokine receptor 5 (CCR5) phosphorylation and identification of phosphorylation sites on the CCR5 carboxyl terminus. J Biol Chem 1999; 274:8875-85. [PMID: 10085131 DOI: 10.1074/jbc.274.13.8875] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The binding of CC chemokines to CC chemokine receptor 5 (CCR5) triggers cellular responses that, generally, are only transient in nature. To explore the potential role of G protein-coupled receptor kinases (GRKs) in the regulation of CCR5, we performed phosphorylation experiments in a rat basophilic leukemia cell line stably expressing CCR5. The ability of various CCR5 ligands to stimulate calcium mobilization in these cells correlated with their ability to induce receptor phosphorylation, desensitization, internalization, and GRK association with the receptor. Aminooxypentane-RANTES, a potent inhibitor of human immunodeficiency virus infection, has been proposed to act through enhanced CCR5 internalization and inhibition of receptor recycling. Aminooxypentane-RANTES profoundly induced CCR5 phosphorylation, but had no effect on CCR1. In permeabilized rat basophilic leukemia CCR5 cells, monoclonal antibodies with specificity for GRK2/3 inhibited RANTES-induced receptor phosphorylation. Consistent with a role for these kinases in CCR5 regulation, 1-2 x 10(5) copies of GRK2 or GRK3 were found to be expressed in peripheral blood leukocytes. Phosphoamino acid analysis revealed that RANTES-induced CCR5 phosphorylation selectively occurs on serine residues. Our findings with receptor mutants indicate that serine residues at positions 336, 337, 342, and 349 represent GRK phosphorylation sites on CCR5. This study demonstrates that chemokines differ in their ability to induce CCR5 phosphorylation and desensitization and provides a molecular mechanism for the agonist-induced attenuation of CCR5 signaling.
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Affiliation(s)
- M Oppermann
- Department of Immunology, University of Göttingen, 37075 Göttingen, Germany.
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