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Hopkins MM, Liu Z, Meier KE. Positive and Negative Cross-Talk between Lysophosphatidic Acid Receptor 1, Free Fatty Acid Receptor 4, and Epidermal Growth Factor Receptor in Human Prostate Cancer Cells. J Pharmacol Exp Ther 2016; 359:124-33. [PMID: 27474750 PMCID: PMC5034703 DOI: 10.1124/jpet.116.233379] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 07/22/2016] [Indexed: 12/22/2022] Open
Abstract
Lysophosphatidic acid (LPA) is a lipid mediator that mediates cellular effects via G protein-coupled receptors (GPCRs). Epidermal growth factor (EGF) is a peptide that acts via a receptor tyrosine kinase. LPA and EGF both induce proliferation of prostate cancer cells and can transactivate each other's receptors. The LPA receptor LPA1 is particularly important for LPA response in human prostate cancer cells. Previous work in our laboratory has demonstrated that free fatty acid 4 (FFA4), a GPCR activated by ω-3 fatty acids, inhibits responses to both LPA and EGF in these cells. One potential mechanism for the inhibition involves negative interactions between FFA4 and LPA1, thereby suppressing responses to EGF that require LPA1 In the current study, we examined the role of LPA1 in mediating EGF and FFA4 agonist responses in two human prostate cancer cell lines, DU145 and PC-3. The results show that an LPA1-selective antagonist inhibits proliferation and migration to both LPA and EGF. Knockdown of LPA1 expression, using silencing RNA, blocks responses to LPA and significantly inhibits responses to EGF. The partial response to EGF that is observed after LPA1 knockdown is not inhibited by FFA4 agonists. Finally, the role of arrestin-3, a GPCR-binding protein that mediates many actions of activated GPCRs, was tested. Knockdown of arrestin-3 completely inhibits responses to both LPA and EGF in prostate cancer cells. Taken together, these results suggest that LPA1 plays a critical role in EGF responses and that FFA4 agonists inhibit proliferation by suppressing positive cross-talk between LPA1 and the EGF receptor.
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Affiliation(s)
- Mandi M Hopkins
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Ze Liu
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Kathryn E Meier
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
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Hypocretin/Orexin Peptides Alter Spike Encoding by Serotonergic Dorsal Raphe Neurons through Two Distinct Mechanisms That Increase the Late Afterhyperpolarization. J Neurosci 2016; 36:10097-115. [PMID: 27683906 DOI: 10.1523/jneurosci.0635-16.2016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 08/11/2016] [Indexed: 01/02/2023] Open
Abstract
UNLABELLED Orexins (hypocretins) are neuropeptides that regulate multiple homeostatic processes, including reward and arousal, in part by exciting serotonergic dorsal raphe neurons, the major source of forebrain serotonin. Here, using mouse brain slices, we found that, instead of simply depolarizing these neurons, orexin-A altered the spike encoding process by increasing the postspike afterhyperpolarization (AHP) via two distinct mechanisms. This orexin-enhanced AHP (oeAHP) was mediated by both OX1 and OX2 receptors, required Ca(2+) influx, reversed near EK, and decayed with two components, the faster of which resulted from enhanced SK channel activation, whereas the slower component decayed like a slow AHP (sAHP), but was not blocked by UCL2077, an antagonist of sAHPs in some neurons. Intracellular phospholipase C inhibition (U73122) blocked the entire oeAHP, but neither component was sensitive to PKC inhibition or altered PKA signaling, unlike classical sAHPs. The enhanced SK current did not depend on IP3-mediated Ca(2+) release but resulted from A-current inhibition and the resultant spike broadening, which increased Ca(2+) influx and Ca(2+)-induced-Ca(2+) release, whereas the slower component was insensitive to these factors. Functionally, the oeAHP slowed and stabilized orexin-induced firing compared with firing produced by a virtual orexin conductance lacking the oeAHP. The oeAHP also reduced steady-state firing rate and firing fidelity in response to stimulation, without affecting the initial rate or fidelity. Collectively, these findings reveal a new orexin action in serotonergic raphe neurons and suggest that, when orexin is released during arousal and reward, it enhances the spike encoding of phasic over tonic inputs, such as those related to sensory, motor, and reward events. SIGNIFICANCE STATEMENT Orexin peptides are known to excite neurons via slow postsynaptic depolarizations. Here we elucidate a significant new orexin action that increases and prolongs the postspike afterhyperpolarization (AHP) in 5-HT dorsal raphe neurons and other arousal-system neurons. Our mechanistic studies establish involvement of two distinct Ca(2+)-dependent AHP currents dependent on phospholipase C signaling but independent of IP3 or PKC. Our functional studies establish that this action preserves responsiveness to phasic inputs while attenuating responsiveness to tonic inputs. Thus, our findings bring new insight into the actions of an important neuropeptide and indicate that, in addition to producing excitation, orexins can tune postsynaptic excitability to better encode the phasic sensory, motor, and reward signals expected during aroused states.
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103
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Balki M, Ramachandran N, Lee S, Talati C. The Recovery Time of Myometrial Responsiveness After Oxytocin-Induced Desensitization in Human Myometrium In Vitro. Anesth Analg 2016; 122:1508-15. [PMID: 27007079 DOI: 10.1213/ane.0000000000001268] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Postpartum hemorrhage secondary to uterine atony is a leading cause of maternal morbidity. Prolonged exposure to oxytocin for labor augmentation can result in the desensitization phenomenon, a decrease in the responsiveness of myometrium to further oxytocin. It is currently not known whether waiting for a specific time interval after the cessation of oxytocin allows the oxytocin receptors to resensitize and recover, thereby improving subsequent oxytocin-induced myometrial contractility. We aimed to investigate the effect of a rest period of 30, 60, and 90 minutes after oxytocin administration on the recovery of oxytocin-desensitized human myometrium in vitro. We hypothesized that the longer the rest period, the better the responsiveness and subsequent oxytocin-induced contractility of the myometrium. METHODS Myometrial tissue was obtained from women undergoing elective cesarean deliveries. The myometrial sample was dissected into 4 strips, and each strip was mounted in a single organ bath with physiological salt solution (PSS) under homeostatic conditions and then pretreated for 2 hours with oxytocin 10 M. After pretreatment, each strip was washed with PSS and allowed to rest in PSS solution for 30, 60, or 90 minutes. At the end of the rest period, dose-response testing to oxytocin 10 to 10 M was performed. A control group consisted of oxytocin dose-response testing without any oxytocin pretreatment. Contractile parameters were measured and compared among the groups after square root transformation. The primary outcome was motility index (frequency × amplitude), and secondary outcomes included frequency, amplitude, and area under the curve. RESULTS Fifty-five experiments were conducted from samples obtained from 16 women. The mean motility index (√g·contractions/10 min) during the dose-response curve (oxytocin 10 to 10 M) in the control group was significantly greater than all the experimental groups; the mean estimated differences (95% confidence intervals) were -1.33 (-2.50 to -0.15, P = 0.02), -1.59 (-2.68 to -0.50, P = 0.004), and -1.88 (-2.97 to -0.80, P = 0.001) for the 30-, 60-, and 90-minute groups, respectively. When the experimental groups were compared, there were no significant differences in any of the contractility parameters; however, confidence intervals were wide. CONCLUSIONS Our study shows that oxytocin pretreatment attenuates oxytocin-induced contractility in human myometrium despite a rest period of up to 90 minutes after oxytocin administration. However, we were unable to determine whether increasing the rest period from 30 to 90 minutes results in improvement in myometrial contractility because of our small sample size relative to the variability in the contractile parameters. Further laboratory and clinical in vivo studies are necessary to determine whether a rest period up to 90 minutes results in improvement in myometrial contractility. In addition, further experimental studies are necessary to determine the key mechanisms of oxytocin receptor resensitization.
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Affiliation(s)
- Mrinalini Balki
- From the *Department of Anesthesia and Pain Management, Mount Sinai Hospital, University of Toronto, Toronto, Canada; and †Department of Anesthesia and Pain Management, Mount Sinai Hospital, University of Toronto, Toronto, Canada
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104
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Henckens MJAG, Deussing JM, Chen A. Region-specific roles of the corticotropin-releasing factor-urocortin system in stress. Nat Rev Neurosci 2016; 17:636-51. [PMID: 27586075 DOI: 10.1038/nrn.2016.94] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Dysregulation of the corticotropin-releasing factor (CRF)-urocortin (UCN) system has been implicated in stress-related psychopathologies such as depression and anxiety. It has been proposed that CRF-CRF receptor type 1 (CRFR1) signalling promotes the stress response and anxiety-like behaviour, whereas UCNs and CRFR2 activation mediate stress recovery and the restoration of homeostasis. Recent findings, however, provide clear evidence that this view is overly simplistic. Instead, a more complex picture has emerged that suggests that there are brain region- and cell type-specific effects of CRFR signalling that are influenced by the individual's prior experience and that shape molecular, cellular and ultimately behavioural responses to stressful challenges.
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Affiliation(s)
- Marloes J A G Henckens
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 7610001, Israel.,Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, 80804 Munich, Germany.,Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, 6500 HB Nijmegen, The Netherlands
| | - Jan M Deussing
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, 80804 Munich, Germany
| | - Alon Chen
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 7610001, Israel.,Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, 80804 Munich, Germany
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Heterologous, PKC-Mediated Desensitization of Human Histamine H3 Receptors Expressed in CHO-K1 Cells. Neurochem Res 2016; 41:2415-24. [PMID: 27350581 DOI: 10.1007/s11064-016-1954-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 05/06/2016] [Accepted: 05/11/2016] [Indexed: 12/11/2022]
Abstract
Desensitization is a major mechanism to regulate the functional response of G protein-coupled receptors. In this work we studied whether the human histamine H3 receptor of 445 amino acids (hH3R445) experiences heterologous desensitization mediated by PKC activation. Bioinformatic analysis indicated the presence of Serine and Threonine residues susceptible of PKC-mediated phosphorylation on the third intracellular loop and the carboxyl terminus of the hH3R445. In CHO-K1 cells stably transfected with the hH3R445 direct PKC activation by phorbol 12-myristate 13-acetate (TPA, 200 nM) abolished H3R-mediated inhibition of forskolin-stimulated cAMP accumulation. Activation of endogenous purinergic receptors by ATP (adenosine 5'-triphosphate, 10 μM) increased the free calcium intracellular concentration ([Ca(2+)]i) confirming their coupling to phospholipase C stimulation. Incubation with ATP also abolished H3R-mediated inhibition of forskolin-induced cAMP accumulation, and this effect was prevented by the PKC inhibitors Ro-31-8220 and Gö-6976. Pre-incubation with TPA or ATP reduced H3R-mediated stimulation of [(35)S]-GTPγS binding to membranes from CHO-K1-hH3R445 cells by 39.7 and 54.2 %, respectively, with no change in the agonist potency, and the effect was prevented by either Ro-31-8220 or Gö-6976. Exposure to ATP or TPA also resulted in the loss of cell surface H3Rs (-30.4 and -45.1 %) as evaluated by [(3)H]-NMHA binding to intact cells. These results indicate that the hH3R445 undergoes heterologous desensitization upon activation of receptors coupled to PKC stimulation.
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106
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Zhang X, Sun N, Zheng M, Kim KM. Clathrin-mediated endocytosis is responsible for the lysosomal degradation of dopamine D3 receptor. Biochem Biophys Res Commun 2016; 476:245-251. [PMID: 27240955 DOI: 10.1016/j.bbrc.2016.05.104] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Accepted: 05/20/2016] [Indexed: 11/30/2022]
Abstract
GRK2-/β-Arrestin- and PKA-/PKC-mediated desensitization, internalization, and degradation are three representative pathways for regulating G protein-coupled receptors (GPCRs). Compared with GRK2/β-arrestin-mediated ones, functional relationship among the aforementioned three regulatory processes mediated by PKA/PKC is less clear. Dopamine D3 receptor (D3R), a major target of currently available antipsychotic drugs, is a typical GPCR that selectively undergoes PKC-mediated regulation. In the present study, we examined PKC-mediated internalization of D3R in correlation with its roles in desensitization and degradation. Our results showed that the kinase activity of PKCβII and the 229th and 257th serine residues of D3R were required for PKC-mediated desensitization, internalization, and degradation of D3R. PMA treatment ubiquitinated D3R and induced its degradation through lysosomal pathway. Blockade of clathrin-mediated internalization inhibited PKC-mediated lysosomal degradation of D3R but did not affect its desensitization. These results suggested that PKC-mediated phosphorylation of D3R involved clathrin-mediated internalization, which was important for the lysosomal degradation of D3R.
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Affiliation(s)
- Xiaohan Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, GwangJu 61186, Republic of Korea
| | - Ningning Sun
- Department of Pharmacology, College of Pharmacy, Chonnam National University, GwangJu 61186, Republic of Korea
| | - Mei Zheng
- Department of Pharmacology, College of Pharmacy, Chonnam National University, GwangJu 61186, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, GwangJu 61186, Republic of Korea.
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Taguchi K, Matsumoto T, Kobayashi T. G-protein-coupled receptor kinase 2 and endothelial dysfunction: molecular insights and pathophysiological mechanisms. J Smooth Muscle Res 2016; 51:37-49. [PMID: 26447102 PMCID: PMC5137304 DOI: 10.1540/jsmr.51.37] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Smooth muscle cells (SMC) and endothelial cells are the major cell types in blood
vessels. The principal function of vascular SMC in the body is to regulate blood flow and
pressure through contraction and relaxation. The endothelium performs a crucial role in
maintaining vascular integrity by achieving whole-organ metabolic homeostasis via the
production of factors associated with vasoconstriction or vasorelaxation. In this review,
we have focused on the production of nitric oxide (NO), a vasorelaxation factor. The
extent of NO production represents a key marker in vascular health. A decrease in NO is
capable of inducing pathological conditions associated with endothelial dysfunction, such
as obesity, diabetes, cardiovascular disease, and atherosclerosis. Recent studies have
strongly implicated the involvement of G-protein-coupled receptor kinase 2 (GRK2) in the
progression of cardiovascular disease. Vasculature which is affected by insulin resistance
and type 2 diabetes expresses high levels of GRK2, which may induce endothelial
dysfunction by reducing intracellular NO. GRK2 activation also induces changes in the
subcellular localization of GRK2 itself and also of β-arrestin 2, a downstream protein. In
this review, we describe the pathophysiological mechanisms of insulin resistance and
diabetes, focusing on the signal transduction for NO production via GRK2 and β-arrestin 2,
providing novel insights into the potential field of translational investigation in the
treatment of diabetic complications.
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Affiliation(s)
- Kumiko Taguchi
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Tokyo, Japan
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108
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Bhattacharyya S. Inside story of Group I Metabotropic Glutamate Receptors (mGluRs). Int J Biochem Cell Biol 2016; 77:205-12. [PMID: 26987586 DOI: 10.1016/j.biocel.2016.03.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/10/2016] [Accepted: 03/11/2016] [Indexed: 12/31/2022]
Abstract
Metabotropic glutamate receptors (mGluRs) are G-protein coupled receptors (GPCRs) that are activated by the neurotransmitter glutamate in the central nervous system. Among the eight subtypes, mGluR1 and mGluR5 belong to the group I family. These receptors play important roles in the brain and are believed to be involved in multiple forms of experience dependent synaptic plasticity including learning and memory. In addition, group I mGluRs also have been implicated in various neuropsychiatric disorders like Fragile X syndrome, autism etc. The normal signaling depends on the precise location of these receptors in specific region of the neuron and the process of receptor trafficking plays a crucial role in controlling this localization. Intracellular trafficking could also regulate the desensitization, resensitization, down-regulation and intracellular signaling of these receptors. In this review I focus on the current understanding of group I mGluR regulation in the central nervous system and also their role in neuropsychiatric disorders.
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Affiliation(s)
- Samarjit Bhattacharyya
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge city, Sector-81, SAS Nagar, PO: 140306, Punjab, India.
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Hill R, Lyndon A, Withey S, Roberts J, Kershaw Y, MacLachlan J, Lingford-Hughes A, Kelly E, Bailey C, Hickman M, Henderson G. Ethanol Reversal of Tolerance to the Respiratory Depressant Effects of Morphine. Neuropsychopharmacology 2016; 41:762-73. [PMID: 26171718 PMCID: PMC4610039 DOI: 10.1038/npp.2015.201] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/23/2015] [Accepted: 07/01/2015] [Indexed: 11/09/2022]
Abstract
Opioids are the most common drugs associated with unintentional drug overdose. Death results from respiratory depression. Prolonged use of opioids results in the development of tolerance but the degree of tolerance is thought to vary between different effects of the drugs. Many opioid addicts regularly consume alcohol (ethanol), and post-mortem analyses of opioid overdose deaths have revealed an inverse correlation between blood morphine and ethanol levels. In the present study, we determined whether ethanol reduced tolerance to the respiratory depressant effects of opioids. Mice were treated with opioids (morphine, methadone, or buprenorphine) for up to 6 days. Respiration was measured in freely moving animals breathing 5% CO2 in air in plethysmograph chambers. Antinociception (analgesia) was measured as the latency to remove the tail from a thermal stimulus. Opioid tolerance was assessed by measuring the response to a challenge dose of morphine (10 mg/kg i.p.). Tolerance developed to the respiratory depressant effect of morphine but at a slower rate than tolerance to its antinociceptive effect. A low dose of ethanol (0.3 mg/kg) alone did not depress respiration but in prolonged morphine-treated animals respiratory depression was observed when ethanol was co-administered with the morphine challenge. Ethanol did not alter the brain levels of morphine. In contrast, in methadone- or buprenorphine-treated animals no respiratory depression was observed when ethanol was co-administered along with the morphine challenge. As heroin is converted to morphine in man, selective reversal of morphine tolerance by ethanol may be a contributory factor in heroin overdose deaths.
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Affiliation(s)
- Rob Hill
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Abi Lyndon
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Sarah Withey
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Joanne Roberts
- School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow, UK
| | - Yvonne Kershaw
- School of Clinical Sciences, University of Bristol, Bristol, UK
| | - John MacLachlan
- School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow, UK
| | - Anne Lingford-Hughes
- Division of Brain Sciences, Centre for Neuropsychopharmacology, Imperial College, London, UK
| | - Eamonn Kelly
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Chris Bailey
- Department of Pharmacy and Pharmacology, University of Bath, Bath, UK
| | - Matthew Hickman
- School of Social and Community Medicine, University of Bristol, Bristol, UK
| | - Graeme Henderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Abstract
The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are important regulators of insulin and glucagon secretion as well as lipid metabolism and appetite. These biological functions make their respective receptors (GIPR and GLP-1R) attractive targets in the treatment of both type 2 diabetes mellitus (T2DM) and obesity. The use of these native peptides in the treatment of these conditions is limited by their short half-lives. However, long-acting GLP-1R agonists and inhibitors of the enzyme that rapidly inactivates GIP and GLP-1 (dipeptidyl peptidase IV) are in clinical use. Although there is a loss of response to both hormones in T2DM, this effect appears to be more pronounced for GIP. This has made targeting GIPR less successful than GLP-1R. Furthermore, results demonstrating that GIPR knockout mice were resistant to diet-induced obesity suggested that GIPR antagonists may prove to be useful therapeutics. More recently, molecules that activate both receptors have shown promise in terms of glycemic and body weight control. This review focused on recent advances in the understanding of the signaling mechanisms and regulation of these two clinically important receptors.
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Affiliation(s)
- Suleiman Al-Sabah
- *Dr. Suleiman Al-Sabah, Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110 (Kuwait), E-Mail
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111
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Mocking TAM, Bosma R, Rahman SN, Verweij EWE, McNaught-Flores DA, Vischer HF, Leurs R. Molecular Aspects of Histamine Receptors. HISTAMINE RECEPTORS 2016. [DOI: 10.1007/978-3-319-40308-3_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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112
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“Barcode” and Differential Effects of GPCR Phosphorylation by Different GRKs. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2016. [DOI: 10.1007/978-1-4939-3798-1_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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113
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Recruitment of β-Arrestin into Neuronal Cilia Modulates Somatostatin Receptor Subtype 3 Ciliary Localization. Mol Cell Biol 2015; 36:223-35. [PMID: 26503786 DOI: 10.1128/mcb.00765-15] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 10/20/2015] [Indexed: 01/09/2023] Open
Abstract
Primary cilia are essential sensory and signaling organelles present on nearly every mammalian cell type. Defects in primary cilia underlie a class of human diseases collectively termed ciliopathies. Primary cilia are restricted subcellular compartments, and specialized mechanisms coordinate the localization of proteins to cilia. Moreover, trafficking of proteins into and out of cilia is required for proper ciliary function, and this process is disrupted in ciliopathies. The somatostatin receptor subtype 3 (Sstr3) is selectively targeted to primary cilia on neurons in the mammalian brain and is implicated in learning and memory. Here, we show that Sstr3 localization to cilia is dynamic and decreases in response to somatostatin treatment. We further show that somatostatin treatment stimulates β-arrestin recruitment into Sstr3-positive cilia and this recruitment can be blocked by mutations in Sstr3 that impact agonist binding or phosphorylation. Importantly, somatostatin treatment fails to decrease Sstr3 ciliary localization in neurons lacking β-arrestin 2. Together, our results implicate β-arrestin in the modulation of Sstr3 ciliary localization and further suggest a role for β-arrestin in the mediation of Sstr3 ciliary signaling.
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114
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Fitting S, Zou S, El-Hage N, Suzuki M, Paris JJ, Schier CJ, Rodríguez JW, Rodriguez M, Knapp PE, Hauser KF. Opiate addiction therapies and HIV-1 Tat: interactive effects on glial [Ca²⁺]i, oxyradical and neuroinflammatory chemokine production and correlative neurotoxicity. Curr HIV Res 2015; 12:424-34. [PMID: 25760046 PMCID: PMC4475822 DOI: 10.2174/1570162x1206150311161147] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 12/13/2014] [Accepted: 02/12/2015] [Indexed: 01/05/2023]
Abstract
Few preclinical studies have compared the relative therapeutic efficacy of medications used to treat opiate addiction in relation to neuroAIDS. Here we compare the ability of methadone and buprenorphine, and the prototypic opiate morphine, to potentiate the neurotoxic and proinflammatory ([Ca2+]i, ROS, H2O2, chemokines) effects of HIV-1 Tat in neuronal and/or mixed-glial co-cultures. Repeated observations of neurons during 48 h exposure to combinations of Tat, equimolar concentrations (500 nM) of morphine, methadone, or buprenorphine exacerbated neurotoxicity significantly above levels seen with Tat alone. Buprenorphine alone displayed marked neurotoxicity at 500 nM, prompting additional studies of its neurotoxic effects at 5 nM and 50 nM concentrations ± Tat. In combination with Tat, buprenorphine displayed paradoxical, concentration-dependent, neurotoxic and neuroprotective actions. Buprenorphine neurotoxicity coincided with marked elevations in [Ca2+]i, but not increases in glial ROS or chemokine release. Tat by itself elevated the production of CCL5/RANTES, CCL4/MIP-1β, and CCL2/MCP-1. Methadone and buprenorphine alone had no effect, but methadone interacted with Tat to further increase production of CCL5/RANTES. In combination with Tat, all drugs significantly increased glial [Ca2+]i, but ROS was only significantly increased by co-exposure with morphine. Taken together, the increases in glial [Ca2+]i, ROS, and neuroinflammatory chemokines were not especially accurate predictors of neurotoxicity. Despite similarities, opiates displayed differences in their neurotoxic and neuroinflammatory interactions with Tat. Buprenorphine, in particular, was partially neuroprotective at a low concentration, which may result from its unique pharmacological profile at multiple opioid receptors. Overall, the results reveal differences among addiction medications that may impact neuroAIDS.
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115
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Philip JL, Razzaque MA, Han M, Li J, Theccanat T, Xu X, Akhter SA. Regulation of mitochondrial oxidative stress by β-arrestins in cultured human cardiac fibroblasts. Dis Model Mech 2015; 8:1579-89. [PMID: 26449263 PMCID: PMC4728312 DOI: 10.1242/dmm.019968] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 08/24/2015] [Indexed: 12/13/2022] Open
Abstract
Oxidative stress in cardiac fibroblasts (CFs) promotes transformation to myofibroblasts and collagen synthesis leading to myocardial fibrosis, a precursor to heart failure (HF). NADPH oxidase 4 (Nox4) is a major source of cardiac reactive oxygen species (ROS); however, mechanisms of Nox4 regulation are unclear. β-arrestins are scaffold proteins that signal in G-protein-dependent and -independent pathways; for example, in ERK activation. We hypothesize that β-arrestins regulate oxidative stress in a Nox4-dependent manner and increase fibrosis in HF. CFs were isolated from normal and failing adult human left ventricles. Mitochondrial ROS/superoxide production was quantitated using MitoSox. β-arrestin and Nox4 expressions were manipulated using adenoviral overexpression or short interfering RNA (siRNA)-mediated knockdown. Mitochondrial oxidative stress and Nox4 expression in CFs were significantly increased in HF. Nox4 knockdown resulted in inhibition of mitochondrial superoxide production and decreased basal and TGF-β-stimulated collagen and α-SMA expression. CF β-arrestin expression was upregulated fourfold in HF. β-arrestin knockdown in failing CFs decreased ROS and Nox4 expression by 50%. β-arrestin overexpression in normal CFs increased mitochondrial superoxide production twofold. These effects were prevented by inhibition of either Nox or ERK. Upregulation of Nox4 seemed to be a primary mechanism for increased ROS production in failing CFs, which stimulates collagen deposition. β-arrestin expression was upregulated in HF and plays an important and newly identified role in regulating mitochondrial superoxide production via Nox4. The mechanism for this effect seems to be ERK-mediated. Targeted inhibition of β-arrestins in CFs might decrease oxidative stress as well as pathological cardiac fibrosis. Summary: β-arrestins regulate oxidative stress in a Nox4-dependent manner leading to increased extracellular-matrix protein synthesis by cardiac fibroblasts (CFs). Targeted inhibition of β-arrestins in CFs might decrease pathological fibrosis.
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Affiliation(s)
- Jennifer L Philip
- Department of Surgery, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Md Abdur Razzaque
- Department of Surgery, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Mei Han
- Department of Surgery, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Jinju Li
- Section of Cardiac and Thoracic Surgery, University of Chicago Medical Center, Chicago, IL 60637, USA
| | - Tiju Theccanat
- Section of Cardiac and Thoracic Surgery, University of Chicago Medical Center, Chicago, IL 60637, USA
| | - Xianyao Xu
- Department of Surgery, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
| | - Shahab A Akhter
- Department of Surgery, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
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Mahato P, Pandey S, Bhattacharyya S. Differential effects of protein phosphatases in the recycling of metabotropic glutamate receptor 5. Neuroscience 2015; 306:138-50. [DOI: 10.1016/j.neuroscience.2015.08.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 07/28/2015] [Accepted: 08/14/2015] [Indexed: 10/23/2022]
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Emery MA, Bates MLS, Wellman PJ, Eitan S. Differential Effects of Oxycodone, Hydrocodone, and Morphine on Activation Levels of Signaling Molecules. PAIN MEDICINE 2015; 17:908-914. [PMID: 26349634 DOI: 10.1111/pme.12918] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Opioids alter the responses of D2-like dopamine receptors (D2DRs), known to be involved in the pathology of addiction and other mental illnesses. Importantly, our recent results demonstrated that various opioids differentially modulate the behavioral responses of D2DRs. OBJECTIVE To examine the effect of various opioids on striatal activation levels of Akt and ERK1/2, as well as the signaling responses of D2DRs following opioid exposure. METHODS Mice were pre-treated with 20 mg/kg morphine, hydrocodone, oxycodone, or saline for 6 days. Twenty-four hours later, mice were injected with vehicle or a D2/D3 receptor agonist, quinpirole. Thirty minutes later, dorsal striatum was collected and analyzed using Western blot. RESULTS In morphine-pretreated animals, baseline Akt activation level was unchanged, but was reduced in response to quinpirole. In contrast, baseline Akt activation levels were reduced in mice pretreated with hydrocodone and oxycodone, but were unchanged in response to quinpirole. In mice pretreated with all opioids, baseline ERK2 activation levels were unchanged and increased in response to quinpirole. However, quinpirole-induced ERK2 activation was significantly higher than drug naïve animals only in the morphine-pretreated mice. CONCLUSIONS Various opioids differentially modulate the baseline activation levels of signaling molecules, which in turn results in ligand-selective effects on the responses to a D2/D3 dopamine receptor agonist. This demonstrates a complex interplay between opioid receptors and D2DRs, and supports the notion that various opioids carry differential risks to the dopamine reward system. This information should be considered when prescribing opioid pain medication, to balance effectiveness with minimal risk.
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Affiliation(s)
- Michael A Emery
- Department of Psychology, Behavioral and Cellular Neuroscience Program, and the Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, 4235 TAMU, College Station, TX, USA
| | - M L Shawn Bates
- Department of Psychology, Behavioral and Cellular Neuroscience Program, and the Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, 4235 TAMU, College Station, TX, USA
| | - Paul J Wellman
- Department of Psychology, Behavioral and Cellular Neuroscience Program, and the Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, 4235 TAMU, College Station, TX, USA
| | - Shoshana Eitan
- Department of Psychology, Behavioral and Cellular Neuroscience Program, and the Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, 4235 TAMU, College Station, TX, USA
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Song WY, Aihara Y, Hashimoto T, Kanazawa K, Mizuno M. (-)-Epigallocatechin-3-gallate induces secretion of anorexigenic gut hormones. J Clin Biochem Nutr 2015; 57:164-9. [PMID: 26388676 PMCID: PMC4566026 DOI: 10.3164/jcbn.15-50] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 06/19/2015] [Indexed: 12/24/2022] Open
Abstract
The anorexigenic gut hormones, cholecystokinin (CCK), glucagon-like peptide (GLP)-1 and peptide tyrosine-tyrosine (PYY), are released in response to food intake from the intestines. Dietary nutrients have been shown to stimulate these hormones. Some non-nutrients such as polyphenols show anorexigenic effects on humans. In the present study, we examined whether dietary polyphenols can stimulate secretion of these gut hormones. Caco-2 cells expressed mRNA of the gut hormones, CCK, PC1 (prohormone convertase 1), GCG (glucagon) and PYY. CCK, GLP-1 and PYY were secreted from Caco-2 cells after adding sugars, amino acids or fatty acids. Using Caco-2 cells, epigallocatechin-3-gallate (EGCG), chlorogenic acid and ferulic acid induced secretion of anorexigenic gut hormones. Particularly, EGCG induced secretion of all three hormones. In an ex vivo assay using murine intestines, EGCG also released CCK from the duodenum, and GLP-1 from the ileum. These results suggest that EGCG may affect appetite via gut hormones.
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Affiliation(s)
- Won-Young Song
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Yoshiko Aihara
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Takashi Hashimoto
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Kazuki Kanazawa
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Masashi Mizuno
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
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Jamshidi RJ, Jacobs BA, Sullivan LC, Chavera TA, Saylor RM, Prisinzano TE, Clarke WP, Berg KA. Functional selectivity of kappa opioid receptor agonists in peripheral sensory neurons. J Pharmacol Exp Ther 2015; 355:174-82. [PMID: 26297384 DOI: 10.1124/jpet.115.225896] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 08/19/2015] [Indexed: 01/12/2023] Open
Abstract
Activation of kappa opioid receptors (KORs) expressed by peripheral sensory neurons that respond to noxious stimuli (nociceptors) can reduce neurotransmission of pain stimuli from the periphery to the central nervous system. We have previously shown that the antinociception dose-response curve for peripherally restricted doses of the KOR agonist (-)-(trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide (U50488) has an inverted U shape. Here, we found that the downward phase of the U50488 dose-response curve was blocked by an inhibitor of extracellular signal-regulated kinase (ERK) activation U0126. Local administration of the selective KOR agonist salvinorin A (Sal-A), also resulted in an inverted U-shaped curve; however, the downward phase was insensitive to U0126. By contrast, inhibition of c-Jun N-terminal kinase (JNK) partially blocked the downward phase of the dose-response curve to Sal-A, suggesting a role for JNK. In cultures of peripheral sensory neurons, U50488 and Sal-A inhibited adenylyl cyclase activity with similar efficacies; however, their ability to activate ERK and JNK differed. Whereas U50488 activated ERK but not JNK, Sal-A activated JNK but not ERK. Moreover, although both U50488 and Sal-A produced homologous desensitization, desensitization to U50488 was blocked by inhibition of ERK activation, whereas desensitization to Sal-A was blocked by inhibition of JNK. Substitution of an ethoxymethyl ether for the C2 position acetyl group of Sal-A reduced stimulation of JNK, prevented desensitization by ethoxymethyl ether for the C2 position acetyl group of Sal-A, and resulted in a monotonic antinociception dose-response curve. Collectively, these data demonstrate the functional selectivity of KOR ligands for signaling in peripheral sensory neurons, which results in differential effects on behavioral responses in vivo.
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Affiliation(s)
- Raehannah J Jamshidi
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Blaine A Jacobs
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Laura C Sullivan
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Teresa A Chavera
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Rachel M Saylor
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Thomas E Prisinzano
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - William P Clarke
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
| | - Kelly A Berg
- Department of Pharmacology (R.J.J., B.A.J., L.C.S., T.A.C., W.P.C., K.A.B.), University of Texas Health Science Center, San Antonio, Texas; and Department of Medicinal Chemistry (R.M.S., T.E.P.), University of Kansas School of Pharmacy, Lawrence, Kansas
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Waters RP, Rivalan M, Bangasser DA, Deussing JM, Ising M, Wood SK, Holsboer F, Summers CH. Evidence for the role of corticotropin-releasing factor in major depressive disorder. Neurosci Biobehav Rev 2015; 58:63-78. [PMID: 26271720 DOI: 10.1016/j.neubiorev.2015.07.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 06/24/2015] [Accepted: 07/24/2015] [Indexed: 01/05/2023]
Abstract
Major depressive disorder (MDD) is a devastating disease affecting over 300 million people worldwide, and costing an estimated 380 billion Euros in lost productivity and health care in the European Union alone. Although a wealth of research has been directed toward understanding and treating MDD, still no therapy has proved to be consistently and reliably effective in interrupting the symptoms of this disease. Recent clinical and preclinical studies, using genetic screening and transgenic rodents, respectively, suggest a major role of the CRF1 gene, and the central expression of CRF1 receptor protein in determining an individual's risk of developing MDD. This gene is widely expressed in brain tissue, and regulates an organism's immediate and long-term responses to social and environmental stressors, which are primary contributors to MDD. This review presents the current state of knowledge on CRF physiology, and how it may influence the occurrence of symptoms associated with MDD. Additionally, this review presents findings from multiple laboratories that were presented as part of a symposium on this topic at the annual 2014 meeting of the International Behavioral Neuroscience Society (IBNS). The ideas and data presented in this review demonstrate the great progress that has been made over the past few decades in our understanding of MDD, and provide a pathway forward toward developing novel treatments and detection methods for this disorder.
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Affiliation(s)
| | | | | | - J M Deussing
- Max Planck Institute of Psychiatry, Munich, Germany
| | - M Ising
- Max Planck Institute of Psychiatry, Munich, Germany
| | - S K Wood
- University of South Carolina School of Medicine, Columbia, SC, USA
| | - F Holsboer
- Max Planck Institute of Psychiatry, Munich, Germany; HMNC GmbH, Munich, Germany
| | - Cliff H Summers
- University of South Dakota, Vermillion, SD, USA; Sanford School of Medicine, Vermillion, SD, USA.
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121
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Hothersall JD, Brown AJ, Dale I, Rawlins P. Can residence time offer a useful strategy to target agonist drugs for sustained GPCR responses? Drug Discov Today 2015; 21:90-96. [PMID: 26226643 DOI: 10.1016/j.drudis.2015.07.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/24/2015] [Accepted: 07/21/2015] [Indexed: 01/28/2023]
Abstract
Residence time describes the how long a ligand is bound to its target, and is attracting interest in drug discovery as a potential means of improving clinical efficacy by increasing target coverage. This concept, as originally applied to antagonists, is more complicated for G-protein-coupled receptor (GPCR) agonists because of the transiency of receptor responses (via desensitization and internalization). However, in some cases sustained GPCR agonist responses have been observed, with evidence consistent with a role for slow binding kinetics. We propose a model to explain our understanding of how residence time and rebinding might influence sustained signaling by internalized receptors. We also highlight the anticipated benefit for drug discovery of fully understanding and exploiting these phenomena to target desirable receptor response profiles selectively.
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Affiliation(s)
| | | | - Ian Dale
- AstraZeneca, Discovery Sciences, Cambridge Science Park, Cambridge CB4 0WG, UK
| | - Philip Rawlins
- AstraZeneca, Discovery Sciences, Cambridge Science Park, Cambridge CB4 0WG, UK.
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122
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Vischer HF, Castro M, Pin JP. G Protein-Coupled Receptor Multimers: A Question Still Open Despite the Use of Novel Approaches. Mol Pharmacol 2015; 88:561-71. [PMID: 26138074 DOI: 10.1124/mol.115.099440] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 07/02/2015] [Indexed: 12/11/2022] Open
Abstract
Heteromerization of G protein-coupled receptors (GPCRs) can significantly change the functional properties of involved receptors. Various biochemical and biophysical methodologies have been developed in the last two decades to identify and functionally evaluate GPCR heteromers in heterologous cells, with recent approaches focusing on GPCR complex stoichiometry and stability. Yet validation of these observations in native tissues is still lagging behind for the majority of GPCR heteromers. Remarkably, recent studies, particularly some involving advanced fluorescence microscopy techniques, are contributing to our current knowledge of aspects that were not well known until now, such as GPCR complex stoichiometry and stability. In parallel, a growing effort is being applied to move the field forward into native systems. This short review will highlight recent developments to study the stoichiometry and stability of GPCR complexes and methodologies to detect native GPCR dimers.
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Affiliation(s)
- Henry F Vischer
- Amsterdam Institute for Molecules, Medicines and Systems, Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands (H.F.V.); Molecular Pharmacology Laboratory, Biofarma Research Group (GI-1685), University of Santiago de Compostela, Center for Research in Molecular Medicine and Chronic Diseases, Santiago de Compostela, Spain (M.C.); and Centre National de la Recherche Scientifique, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France (J.-P.P.)
| | - Marián Castro
- Amsterdam Institute for Molecules, Medicines and Systems, Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands (H.F.V.); Molecular Pharmacology Laboratory, Biofarma Research Group (GI-1685), University of Santiago de Compostela, Center for Research in Molecular Medicine and Chronic Diseases, Santiago de Compostela, Spain (M.C.); and Centre National de la Recherche Scientifique, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France (J.-P.P.)
| | - Jean-Philippe Pin
- Amsterdam Institute for Molecules, Medicines and Systems, Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands (H.F.V.); Molecular Pharmacology Laboratory, Biofarma Research Group (GI-1685), University of Santiago de Compostela, Center for Research in Molecular Medicine and Chronic Diseases, Santiago de Compostela, Spain (M.C.); and Centre National de la Recherche Scientifique, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France (J.-P.P.)
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Maycas M, Ardura JA, de Castro LF, Bravo B, Gortázar AR, Esbrit P. Role of the Parathyroid Hormone Type 1 Receptor (PTH1R) as a Mechanosensor in Osteocyte Survival. J Bone Miner Res 2015; 30:1231-44. [PMID: 25529820 DOI: 10.1002/jbmr.2439] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 11/22/2014] [Accepted: 12/22/2014] [Indexed: 12/13/2022]
Abstract
Osteocytes have a major role in the control of bone remodeling. Mechanical stimulation decreases osteocyte apoptosis and promotes bone accrual, whereas skeletal unloading is deleterious in both respects. PTH1R ablation or overexpression in osteocytes in mice produces trabecular bone loss or increases bone mass, respectively. The latter effect was related to a decreased osteocyte apoptosis. Here, the putative role of PTH1R activation in osteocyte protection conferred by mechanical stimulation was assessed. Osteocytic MLO-Y4 cells were subjected to mechanical stimuli represented by hypotonic shock (216 mOsm/kg) or pulsatile fluid flow (8 Hz, 10 dynes/cm(2)) for a short pulse (10 min), with or without PTH1R antagonists or after transfection with specific PTHrP or PTH1R siRNA. These mechanical stimuli prevented cell death induced within 6 hours by etoposide (50 μM), related to PTHrP overexpression; and this effect was abolished by the calcium antagonist verapamil (1 μM), a phospholipase C (PLC) inhibitor (U73122; 10 μM), and a PKA activation inhibitor, Rp-cAMPS (25 μM), in these cells. Each mechanical stimulus also rapidly induced β-catenin stabilization and nuclear ERK translocation, which were inhibited by the PTH1R antagonist PTHrP(7-34) (1 μM), or PTH1R siRNA, and mimicked by PTHrP(1-36) (100 nM). Mechanical stretching by hypotonic shock did not affect cAMP production but rapidly (<1 min) stimulated Ca(i)(2+) transients in PTH1R-overexpressing HEK-293 cells and in MLO-Y4 cells, in which calcium signaling was unaffected by the presence of a PTHrP antiserum or PTHrP siRNA but inhibited by knocking down PTH1R. These novel findings indicate that PTH1R is an important component of mechanical signal transduction in osteocytic MLO-Y4 cells, and that PTH1R activation by PTHrP-independent and dependent mechanisms has a relevant role in the prosurvival action of mechanical stimulus in these cells.
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Affiliation(s)
- Marta Maycas
- Instituto de, Investigación Sanitaria (IIS)-, Fundación Jiménez Díaz, Universidad Autónoma de Madrid (UAM) and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
| | - Juan A Ardura
- Instituto de, Investigación Sanitaria (IIS)-, Fundación Jiménez Díaz, Universidad Autónoma de Madrid (UAM) and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
| | - Luis F de Castro
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, Madrid, Spain
| | - Beatriz Bravo
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, Madrid, Spain
| | - Arancha R Gortázar
- Instituto de Medicina Molecular Aplicada (IMMA), Facultad de Medicina, Universidad San Pablo-CEU, Madrid, Spain
| | - Pedro Esbrit
- Instituto de, Investigación Sanitaria (IIS)-, Fundación Jiménez Díaz, Universidad Autónoma de Madrid (UAM) and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
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Hothersall JD, Bussey CE, Brown AJ, Scott JS, Dale I, Rawlins P. Sustained wash-resistant receptor activation responses of GPR119 agonists. Eur J Pharmacol 2015; 762:430-42. [PMID: 26101059 DOI: 10.1016/j.ejphar.2015.06.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 06/15/2015] [Accepted: 06/16/2015] [Indexed: 12/16/2022]
Abstract
G protein-coupled receptor 119 (GPR119) is involved in regulating metabolic homoeostasis, with GPR119 agonists targeted for the treatment of type-2 diabetes and obesity. Using the endogenous agonist oleoylethanolamide and a number of small molecule synthetic agonists we have investigated the temporal dynamics of receptor signalling. Using both a dynamic luminescence biosensor-based assay and an endpoint cAMP accumulation assay we show that agonist-driven desensitization is not a major regulatory mechanism for GPR119 despite robust activation responses, regardless of the agonist used. Temporal analysis of the cAMP responses demonstrated sustained signalling resistant to washout for some, but not all of the agonists tested. Further analysis indicated that the sustained effects of one synthetic agonist AR-231,453 were consistent with a role for slow dissociation kinetics. In contrast, the sustained responses to MBX-2982 and AZ1 appeared to involve membrane deposition. We also detect wash-resistant responses to AR-231,453 at the level of physiologically relevant responses in an endogenous expression system (GLP-1 secretion in GLUTag cells). In conclusion, our findings indicate that in a recombinant expression system GPR119 activation is sustained, with little evidence of pronounced receptor desensitization, and for some ligands persistent agonist responses continue despite removal of excess agonist. This provides novel understanding of the temporal responses profiles of potential drug candidates targetting GPR119, and highlights the importance of carefully examining the the mechanisms through which GPCRs generate sustained responses.
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Affiliation(s)
| | | | - Alastair J Brown
- AstraZeneca, Alderley Park, Macclesfield SK10 4TG, UK; Heptares Therapeutics Limited, Welwyn Garden City AL7 3AX, UK
| | - James S Scott
- AstraZeneca, Alderley Park, Macclesfield SK10 4TG, UK
| | - Ian Dale
- AstraZeneca, Cambridge Science Park, Cambridge CB4 0WG, UK
| | - Philip Rawlins
- AstraZeneca, Cambridge Science Park, Cambridge CB4 0WG, UK
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125
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Lowe JD, Sanderson HS, Cooke AE, Ostovar M, Tsisanova E, Withey SL, Chavkin C, Husbands SM, Kelly E, Henderson G, Bailey CP. Role of G Protein-Coupled Receptor Kinases 2 and 3 in μ-Opioid Receptor Desensitization and Internalization. Mol Pharmacol 2015; 88:347-56. [PMID: 26013542 DOI: 10.1124/mol.115.098293] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 05/26/2015] [Indexed: 01/12/2023] Open
Abstract
There is ongoing debate about the role of G protein-coupled receptor kinases (GRKs) in agonist-induced desensitization of the μ-opioid receptor (MOPr) in brain neurons. In the present paper, we have used a novel membrane-permeable, small-molecule inhibitor of GRK2 and GRK3, Takeda compound 101 (Cmpd101; 3-[[[4-methyl-5-(4-pyridyl)-4H-1,2,4-triazole-3-yl] methyl] amino]-N-[2-(trifuoromethyl) benzyl] benzamidehydrochloride), to study the involvement of GRK2/3 in acute agonist-induced MOPr desensitization. We observed that Cmpd101 inhibits the desensitization of the G protein-activated inwardly-rectifying potassium current evoked by receptor-saturating concentrations of methionine-enkephalin (Met-Enk), [d-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO), endomorphin-2, and morphine in rat and mouse locus coeruleus (LC) neurons. In LC neurons from GRK3 knockout mice, Met-Enk-induced desensitization was unaffected, implying a role for GRK2 in MOPr desensitization. Quantitative analysis of the loss of functional MOPrs following acute agonist exposure revealed that Cmpd101 only partially reversed MOPr desensitization. Inhibition of extracellular signal-regulated kinase 1/2, protein kinase C, c-Jun N-terminal kinase, or GRK5 did not inhibit the Cmpd101-insensitive component of desensitization. In HEK 293 cells, Cmpd101 produced almost complete inhibition of DAMGO-induced MOPr phosphorylation at Ser(375), arrestin translocation, and MOPr internalization. Our data demonstrate a role for GRK2 (and potentially also GRK3) in agonist-induced MOPr desensitization in the LC, but leave open the possibility that another, as yet unidentified, mechanism of desensitization also exists.
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Affiliation(s)
- Janet D Lowe
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Helen S Sanderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Alexandra E Cooke
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Mehrnoosh Ostovar
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Elena Tsisanova
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Sarah L Withey
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Charles Chavkin
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Stephen M Husbands
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Eamonn Kelly
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Graeme Henderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Chris P Bailey
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
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Birdsong WT, Arttamangkul S, Bunzow JR, Williams JT. Agonist Binding and Desensitization of the μ-Opioid Receptor Is Modulated by Phosphorylation of the C-Terminal Tail Domain. Mol Pharmacol 2015; 88:816-24. [PMID: 25934731 DOI: 10.1124/mol.114.097527] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/30/2015] [Indexed: 11/22/2022] Open
Abstract
Sustained activation of G protein-coupled receptors can lead to a rapid decline in signaling through acute receptor desensitization. In the case of the μ-opioid receptor (MOPr), this desensitization may play a role in the development of analgesic tolerance. It is understood that phosphorylation of MOPr promotes association with β-arrestin proteins, which then facilitates desensitization and receptor internalization. Agonists that induce acute desensitization have been shown to induce a noncanonical high-affinity agonist binding state in MOPr, conferring a persistent memory of prior receptor activation. In the current study, live-cell confocal imaging was used to investigate the role of receptor phosphorylation in agonist binding to MOPr. A phosphorylation cluster in the C-terminal tail of MOPr was identified as a mediator of agonist-induced affinity changes in MOPr. This site is unique from the primary phosphorylation cluster responsible for β-arrestin binding and internalization. Electrophysiologic measurements of receptor function suggest that both phosphorylation clusters may play a parallel role during acute receptor desensitization. Desensitization was unaffected by alanine mutation of either phosphorylation cluster, but was largely eliminated when both clusters were mutated. Overall, this work suggests that there are multiple effects of MOPr phosphorylation that appear to regulate MOPr function: one affecting β-arrestin binding and a second affecting agonist binding.
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Affiliation(s)
| | | | - James R Bunzow
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
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127
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de Munnik SM, Smit MJ, Leurs R, Vischer HF. Modulation of cellular signaling by herpesvirus-encoded G protein-coupled receptors. Front Pharmacol 2015; 6:40. [PMID: 25805993 PMCID: PMC4353375 DOI: 10.3389/fphar.2015.00040] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/12/2015] [Indexed: 12/22/2022] Open
Abstract
Human herpesviruses (HHVs) are widespread infectious pathogens that have been associated with proliferative and inflammatory diseases. During viral evolution, HHVs have pirated genes encoding viral G protein-coupled receptors (vGPCRs), which are expressed on infected host cells. These vGPCRs show highest homology to human chemokine receptors, which play a key role in the immune system. Importantly, vGPCRs have acquired unique properties such as constitutive activity and the ability to bind a broad range of human chemokines. This allows vGPCRs to hijack human proteins and modulate cellular signaling for the benefit of the virus, ultimately resulting in immune evasion and viral dissemination to establish a widespread and lifelong infection. Knowledge on the mechanisms by which herpesviruses reprogram cellular signaling might provide insight in the contribution of vGPCRs to viral survival and herpesvirus-associated pathologies.
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Affiliation(s)
- Sabrina M de Munnik
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Martine J Smit
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Rob Leurs
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Henry F Vischer
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
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128
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Sawamura R, Kawabata Y, Kawabata F, Nishimura S, Tabata S. The role of G-protein-coupled receptor 120 in fatty acids sensing in chicken oral tissues. Biochem Biophys Res Commun 2015; 458:387-91. [DOI: 10.1016/j.bbrc.2015.01.125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 01/25/2015] [Indexed: 10/24/2022]
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129
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Ghosh M, Pearse DD. The role of the serotonergic system in locomotor recovery after spinal cord injury. Front Neural Circuits 2015; 8:151. [PMID: 25709569 PMCID: PMC4321350 DOI: 10.3389/fncir.2014.00151] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 12/28/2014] [Indexed: 11/30/2022] Open
Abstract
Serotonin (5-HT), a monoamine neurotransmitter synthesized in various populations of brainstem neurons, plays an important role in modulating the activity of spinal networks involved in vertebrate locomotion. Following spinal cord injury (SCI) there is a disruption of descending serotonergic projections to spinal motor areas, which results in a subsequent depletion in 5-HT, the dysregulation of 5-HT transporters as well as the elevated expression, super-sensitivity and/or constitutive auto-activation of specific 5-HT receptors. These changes in the serotonergic system can produce varying degrees of locomotor dysfunction through to paralysis. To date, various approaches targeting the different components of the serotonergic system have been employed to restore limb coordination and improve locomotor function in experimental models of SCI. These strategies have included pharmacological modulation of serotonergic receptors, through the administration of specific 5-HT receptor agonists, or by elevating the 5-HT precursor 5-hydroxytryptophan, which produces a global activation of all classes of 5-HT receptors. Stimulation of these receptors leads to the activation of the locomotor central pattern generator (CPG) below the site of injury to facilitate or improve the quality and frequency of movements, particularly when used in concert with the activation of other monoaminergic systems or coupled with electrical stimulation. Another approach has been to employ cell therapeutics to replace the loss of descending serotonergic input to the CPG, either through transplanted fetal brainstem 5-HT neurons at the site of injury that can supply 5-HT to below the level of the lesion or by other cell types to provide a substrate at the injury site for encouraging serotonergic axon regrowth across the lesion to the caudal spinal cord for restoring locomotion.
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Affiliation(s)
- Mousumi Ghosh
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine Miami, FL, USA ; Department of Neurological Surgery, University of Miami Miller School of Medicine Miami, FL, USA
| | - Damien D Pearse
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine Miami, FL, USA ; Department of Neurological Surgery, University of Miami Miller School of Medicine Miami, FL, USA ; The Neuroscience Program, University of Miami Miller School of Medicine Miami, FL, USA ; The Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine Miami, FL, USA
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130
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Raveh A, Turecek R, Bettler B. Mechanisms of fast desensitization of GABA(B) receptor-gated currents. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 73:145-65. [PMID: 25637440 DOI: 10.1016/bs.apha.2014.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors (GABA(B)Rs) regulate the excitability of most neurons in the central nervous system by modulating the activity of enzymes and ion channels. In the sustained presence of the neurotransmitter γ-aminobutyric acid, GABA(B)Rs exhibit a time-dependent decrease in the receptor response-a phenomenon referred to as homologous desensitization. Desensitization prevents excessive receptor influences on neuronal activity. Much work focused on the mechanisms of GABA(B)R desensitization that operate at the receptor and control receptor expression at the plasma membrane. Over the past few years, it became apparent that GABA(B)Rs additionally evolved mechanisms for faster desensitization. These mechanisms operate at the G protein rather than at the receptor and inhibit G protein signaling within seconds of agonist exposure. The mechanisms for fast desensitization are ideally suited to regulate receptor-activated ion channel responses, which influence neuronal activity on a faster timescale than effector enzymes. Here, we provide an update on the mechanisms for fast desensitization of GABA(B)R responses and discuss physiological and pathophysiological implications.
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Affiliation(s)
- Adi Raveh
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland; Department of Auditory Neuroscience, Institute of Experimental Medicine, ASCR, Prague, Czech Republic
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland.
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131
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Arttamangkul S, Birdsong W, Williams JT. Does PKC activation increase the homologous desensitization of μ opioid receptors? Br J Pharmacol 2015; 172:583-92. [PMID: 24697621 PMCID: PMC4292970 DOI: 10.1111/bph.12712] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 03/19/2014] [Accepted: 03/23/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE This study examined the role of agents known to activate PKC on morphine-induced desensitization of μ-opioid receptors (MOP receptors) in brain slices containing locus coeruleus neurons. EXPERIMENTAL APPROACH Intracellular recordings were obtained from rat locus coeruleus neurons. Two measurements were used to characterize desensitization, the decline in hyperpolarization induced by application of a saturating concentration of agonist (acute desensitization) and the decrease in hyperpolarization induced by a subsaturating concentration of [Met](5) enkephalin (ME) following washout of the saturating concentration (sustained desensitization). Internalization of MOP receptors was studied in brain slices prepared from transgenic mice expressing Flag-MOP receptors. The subcellular distribution of activated PKC was examined using a novel fluorescent sensor of PKC in HEK293 cells. KEY RESULTS The phorbol esters (PMA and PDBu) and muscarine increased acute desensitization induced by a saturating concentration of morphine and ME. These effects were not sensitive to staurosporine. Staurosporine did not block the decline in hyperpolarization induced by muscarine. PDBu and muscarine did not affect sustained desensitization induced by ME nor did phorbol esters or muscarine change the trafficking of MOP receptors induced by morphine or ME. The distribution of activated PKC measured in HEK293 cells differed depending on which phorbol ester was applied. CONCLUSIONS AND IMPLICATIONS This study demonstrates a distinct difference in two measurements that are often used to evaluate desensitization. The measure of decline correlated well with the reduction in peak amplitudes caused by PKC activators implicating the modification of other factors rather than MOP receptors. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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132
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Specific α-arrestins negatively regulate Saccharomyces cerevisiae pheromone response by down-modulating the G-protein-coupled receptor Ste2. Mol Cell Biol 2014; 34:2660-81. [PMID: 24820415 DOI: 10.1128/mcb.00230-14] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are integral membrane proteins that initiate responses to extracellular stimuli by mediating ligand-dependent activation of cognate heterotrimeric G proteins. In yeast, occupancy of GPCR Ste2 by peptide pheromone α-factor initiates signaling by releasing a stimulatory Gβγ complex (Ste4-Ste18) from its inhibitory Gα subunit (Gpa1). Prolonged pathway stimulation is detrimental, and feedback mechanisms have evolved that act at the receptor level to limit the duration of signaling and stimulate recovery from pheromone-induced G1 arrest, including upregulation of the expression of an α-factor-degrading protease (Bar1), a regulator of G-protein signaling protein (Sst2) that stimulates Gpa1-GTP hydrolysis, and Gpa1 itself. Ste2 is also downregulated by endocytosis, both constitutive and ligand induced. Ste2 internalization requires its phosphorylation and subsequent ubiquitinylation by membrane-localized protein kinases (Yck1 and Yck2) and a ubiquitin ligase (Rsp5). Here, we demonstrate that three different members of the α-arrestin family (Ldb19/Art1, Rod1/Art4, and Rog3/Art7) contribute to Ste2 desensitization and internalization, and they do so by discrete mechanisms. We provide genetic and biochemical evidence that Ldb19 and Rod1 recruit Rsp5 to Ste2 via PPXY motifs in their C-terminal regions; in contrast, the arrestin fold domain at the N terminus of Rog3 is sufficient to promote adaptation. Finally, we show that Rod1 function requires calcineurin-dependent dephosphorylation.
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133
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Morgan MM, Reid RA, Saville KA. Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray. PLoS One 2014; 9:e114269. [PMID: 25503060 PMCID: PMC4263532 DOI: 10.1371/journal.pone.0114269] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 11/09/2014] [Indexed: 12/29/2022] Open
Abstract
Functionally selective signaling appears to contribute to the variability in mechanisms that underlie tolerance to the antinociceptive effects of opioids. The present study tested this hypothesis by examining the contribution of G protein-coupled receptor kinase (GRK)/Protein kinase C (PKC) and C-Jun N-terminal kinase (JNK) activation on both the expression and development of tolerance to morphine and fentanyl microinjected into the ventrolateral periaqueductal gray of the rat. Microinjection of morphine or fentanyl into the periaqueductal gray produced a dose-dependent increase in hot plate latency. Microinjection of the non-specific GRK/PKC inhibitor Ro 32-0432 into the periaqueductal gray to block mu-opioid receptor phosphorylation enhanced the antinociceptive effect of morphine but had no effect on fentanyl antinociception. Microinjection of the JNK inhibitor SP600125 had no effect on morphine or fentanyl antinociception, but blocked the expression of tolerance to repeated morphine microinjections. In contrast, a microinjection of Ro 32-0432 blocked the expression of fentanyl, but not morphine tolerance. Repeated microinjections of Ro 32-0432 blocked the development of morphine tolerance and inhibited fentanyl antinociception whether rats were tolerant or not. Repeated microinjections of SP600125 into the periaqueductal gray blocked the development of tolerance to both morphine and fentanyl microinjections. These data demonstrate that the signaling molecules that contribute to tolerance vary depending on the opioid and methodology used to assess tolerance (expression vs. development of tolerance). This signaling difference is especially clear for the expression of tolerance in which JNK contributes to morphine tolerance and GRK/PKC contributes to fentanyl tolerance.
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Affiliation(s)
- Michael M. Morgan
- Department of Psychology, Washington State University Vancouver, Vancouver, Washington, 98686, United States of America
- * E-mail:
| | - Rachel A. Reid
- Department of Psychology, Washington State University Vancouver, Vancouver, Washington, 98686, United States of America
| | - Kimber A. Saville
- Department of Psychology, Washington State University Vancouver, Vancouver, Washington, 98686, United States of America
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Ahmed D, Muddana HS, Lu M, French JB, Ozcelik A, Fang Y, Butler PJ, Benkovic SJ, Manz A, Huang TJ. Acoustofluidic chemical waveform generator and switch. Anal Chem 2014; 86:11803-10. [PMID: 25405550 PMCID: PMC4255676 DOI: 10.1021/ac5033676] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Eliciting a cellular response to a changing chemical microenvironment is central to many biological processes including gene expression, cell migration, differentiation, apoptosis, and intercellular signaling. The nature and scope of the response is highly dependent upon the spatiotemporal characteristics of the stimulus. To date, studies that investigate this phenomenon have been limited to digital (or step) chemical stimulation with little control over the temporal counterparts. Here, we demonstrate an acoustofluidic (i.e., fusion of acoustics and microfluidics) approach for generating programmable chemical waveforms that permits continuous modulation of the signal characteristics including the amplitude (i.e., sample concentration), shape, frequency, and duty cycle, with frequencies reaching up to 30 Hz. Furthermore, we show fast switching between multiple distinct stimuli, wherein the waveform of each stimulus is independently controlled. Using our device, we characterized the frequency-dependent activation and internalization of the β2-adrenergic receptor (β2-AR), a prototypic G-protein coupled receptor (GPCR), using epinephrine. The acoustofluidic-based programmable chemical waveform generation and switching method presented herein is expected to be a powerful tool for the investigation and characterization of the kinetics and other dynamic properties of many biological and biochemical processes.
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Affiliation(s)
- Daniel Ahmed
- Department of Engineering Science and Mechanics, ‡Biomedical Engineering, §Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
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Characterization of a prawn OA/TA receptor in Xenopus oocytes suggests functional selectivity between octopamine and tyramine. PLoS One 2014; 9:e111314. [PMID: 25350749 PMCID: PMC4211885 DOI: 10.1371/journal.pone.0111314] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 09/30/2014] [Indexed: 11/19/2022] Open
Abstract
Here we report the characterization of an octopamine/tyramine (OA/TA or TyrR1) receptor (OA/TAMac) cloned from the freshwater prawn, Macrobrachium rosenbergii, an animal used in the study of agonistic social behavior. The invertebrate OA/TA receptors are seven trans-membrane domain G-protein coupled receptors that are related to vertebrate adrenergic receptors. Behavioral studies in arthropods indicate that octopaminergic signaling systems modulate fight or flight behaviors with octopamine and/or tyramine functioning in a similar way to the adrenalins in vertebrate systems. Despite the importance of octopamine signaling in behavioral studies of decapod crustaceans there are no functional data available for any of their octopamine or tyramine receptors. We expressed OA/TAMac in Xenopus oocytes where agonist-evoked trans-membrane currents were used as readouts of receptor activity. The currents were most effectively evoked by tyramine but were also evoked by octopamine and dopamine. They were effectively blocked by yohimbine. The electrophysiological approach we used enabled the continuous observation of complex dynamics over time. Using voltage steps, we were able to simultaneously resolve two types of endogenous currents that are affected over different time scales. At higher concentrations we observe that octopamine and tyramine can produce different and opposing effects on both of these currents, presumably through the activity of the single expressed receptor type. The pharmacological profile and apparent functional-selectivity are consistent with properties first observed in the OA/TA receptor from the insect Drosophila melanogaster. As the first functional data reported for any crustacean OA/TA receptor, these results suggest that functional-selectivity between tyramine and octopamine is a feature of this receptor type that may be conserved among arthropods.
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136
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Kelly E. Efficacy and ligand bias at the μ-opioid receptor. Br J Pharmacol 2014; 169:1430-46. [PMID: 23646826 DOI: 10.1111/bph.12222] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 04/10/2013] [Accepted: 04/20/2013] [Indexed: 12/11/2022] Open
Abstract
In order to describe drug action at a GPCR, a full understanding of the pharmacological terms affinity, efficacy and potency is necessary. This is true whether comparing the ability of different agonists to produce a measurable response in a cell or tissue, or determining the relative ability of an agonist to activate a single receptor subtype and produce multiple responses. There is a great deal of interest in the μ-opioid receptor (MOP receptor) and the ligands that act at this GPCR not only because of the clinically important analgesic effects produced by MOP agonists but also because of their liability to induce adverse effects such as respiratory depression and dependence. Our understanding of the mechanisms underlying these effects, as well as the ability to develop new, more effective MOP receptor drugs, depends upon the accurate determination of the efficacy with which these ligands induce coupling of MOP receptors to downstream signalling events. In this review, which is written with the minimum of mathematical content, the basic meaning of terms including efficacy, intrinsic activity and intrinsic efficacy is discussed, along with their relevance to the field of MOP receptor pharmacology, and in particular in relation to biased agonism at this important GPCR.
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Affiliation(s)
- E Kelly
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK.
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137
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Harwood BN, Draper I, Kopin AS. Targeted inactivation of the rickets receptor in muscle compromises Drosophila viability. ACTA ACUST UNITED AC 2014; 217:4091-8. [PMID: 25278473 DOI: 10.1242/jeb.110098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Bursicon is a hormone that modulates wing expansion, cuticle hardening and melanization in Drosophila melanogaster. Bursicon activity is mediated through its cognate G protein-coupled receptor (GPCR), rickets. We have developed a membrane-tethered bursicon construct that enables spatial modulation of rickets-mediated physiology in transgenic flies. Ubiquitous expression of tethered bursicon throughout development results in arrest at the pupal stage. The few organisms that eclose fail to undergo wing expansion. These phenotypes suggest that expression of tethered bursicon inhibits rickets-mediated function. Consistent with this hypothesis, we show in vitro that sustained stimulation of rickets by tethered bursicon leads to receptor desensitization. Furthermore, tissue-specific expression of the tethered bursicon inhibitor unraveled a critical role for rickets in a subset of adult muscles. Taken together, our findings highlight the utility of membrane-tethered inhibitors as important genetic/pharmacological tools to dissect the tissue-specific roles of GPCRs in vivo.
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Affiliation(s)
- Benjamin N Harwood
- Tufts Medical Center, Molecular Cardiology Research Institute, Molecular Pharmacology Research Center, 800 Washington St, Box 7703, Boston, MA 02111, USA Program in Genetics, Sackler School of Graduate Biomedical Sciences, Tufts University, 145 Harrison Avenue, Boston, MA 02111, USA
| | - Isabelle Draper
- Tufts Medical Center, Molecular Cardiology Research Institute, Molecular Pharmacology Research Center, 800 Washington St, Box 7703, Boston, MA 02111, USA
| | - Alan S Kopin
- Tufts Medical Center, Molecular Cardiology Research Institute, Molecular Pharmacology Research Center, 800 Washington St, Box 7703, Boston, MA 02111, USA Program in Genetics, Sackler School of Graduate Biomedical Sciences, Tufts University, 145 Harrison Avenue, Boston, MA 02111, USA
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138
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Funk AJ, Haroutunian V, Meador-Woodruff JH, McCullumsmith RE. Increased G protein-coupled receptor kinase (GRK) expression in the anterior cingulate cortex in schizophrenia. Schizophr Res 2014; 159:130-5. [PMID: 25153362 PMCID: PMC4177355 DOI: 10.1016/j.schres.2014.07.040] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 07/18/2014] [Accepted: 07/20/2014] [Indexed: 01/11/2023]
Abstract
BACKGROUND Current pharmacological treatments for schizophrenia target G protein-coupled receptors (GPCRs), including dopamine receptors. Ligand-bound GPCRs are regulated by a family of G protein-coupled receptor kinases (GRKs), members of which uncouple the receptor from heterotrimeric G proteins, desensitize the receptor, and induce receptor internalization via the arrestin family of scaffolding and signaling molecules. GRKs initiate the activation of downstream signaling pathways, can regulate receptors and signaling molecules independent of GPCR phosphorylation, and modulate epigenetic regulators like histone deacetylases (HDACs). We hypothesize that the expression of GRK proteins is altered in schizophrenia, consistent with previous findings of alterations upstream and downstream from this family of molecules that facilitate intracellular signaling processes. METHODS In this study, we measured protein expression via Western blot analysis for GRKs 2, 3, 5, and 6 in the anterior cingulate cortex of patients with schizophrenia (n=36) and a comparison group (n=33). To control for antipsychotic treatment, we measured these same targets in haloperidol-treated vs. untreated rats (n=10 for both). RESULTS We found increased levels of GRK5 in schizophrenia. No changes were detected in GRK protein expression in rats treated with haloperidol decanoate for 9 months. CONCLUSION These data suggest that increased GRK5 expression may contribute to the pathophysiology of schizophrenia via abnormal regulation of the cytoskeleton, endocytosis, signaling, GPCRs, and histone modification.
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Affiliation(s)
- Adam J. Funk
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, CARE 5830, 231 Albert Sabin Way, Cincinnati, OH 45267-0583
| | - Vahram Haroutunian
- Department of Psychiatry, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1230, New York, NY 10029
| | - James H. Meador-Woodruff
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama Birmingham, SC 560, 1530 3 Avenue South, Birmingham, AL 35294,Evelyn F. McKnight Brain Institute, University of Alabama Birmingham, Shelby 911, 1530 3 Avenue South, Birmingham, AL 35294
| | - Robert E. McCullumsmith
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, CARE 5830, 231 Albert Sabin Way, Cincinnati, OH 45267-0583
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139
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Pandey S, Mahato PK, Bhattacharyya S. Metabotropic glutamate receptor 1 recycles to the cell surface in protein phosphatase 2A-dependent manner in non-neuronal and neuronal cell lines. J Neurochem 2014; 131:602-14. [DOI: 10.1111/jnc.12930] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/30/2014] [Accepted: 08/08/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Saurabh Pandey
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
| | - Prabhat Kumar Mahato
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
| | - Samarjit Bhattacharyya
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
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140
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Lamberts JT, Traynor JR. Opioid receptor interacting proteins and the control of opioid signaling. Curr Pharm Des 2014; 19:7333-47. [PMID: 23448476 DOI: 10.2174/138161281942140105160625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 12/31/2022]
Abstract
Opioid receptors are seven-transmembrane domain receptors that couple to intracellular signaling molecules by activating heterotrimeric G proteins. However, the receptor and G protein do not function in isolation but their activities are modulated by several accessory and scaffolding proteins. Examples include arrestins, kinases, and regulators of G protein signaling proteins. Accessory proteins contribute to the observed potency and efficacy of agonists, but also to the direction of signaling and the phenomenon of biased agonism. This review will present current knowledge of such proteins and how they may provide targets for future drug design.
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Affiliation(s)
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, 1301 MSRB III, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5632, USA.
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141
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A naturally occurring GIP receptor variant undergoes enhanced agonist-induced desensitization, which impairs GIP control of adipose insulin sensitivity. Mol Cell Biol 2014; 34:3618-29. [PMID: 25047836 DOI: 10.1128/mcb.00256-14] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP), an incretin hormone secreted from gastrointestinal K cells in response to food intake, has an important role in the control of whole-body metabolism. GIP signals through activation of the GIP receptor (GIPR), a G-protein-coupled receptor (GPCR). Dysregulation of this pathway has been implicated in the development of metabolic disease. Here we demonstrate that GIPR is constitutively trafficked between the plasma membrane and intracellular compartments of both GIP-stimulated and unstimulated adipocytes. GIP induces a downregulation of plasma membrane GIPR by slowing GIPR recycling without affecting internalization kinetics. This transient reduction in the expression of GIPR in the plasma membrane correlates with desensitization to the effects of GIP. A naturally occurring variant of GIPR (E354Q) associated with an increased incidence of insulin resistance, type 2 diabetes, and cardiovascular disease in humans responds to GIP stimulation with an exaggerated downregulation from the plasma membrane and a delayed recovery of GIP sensitivity following cessation of GIP stimulation. This perturbation in the desensitization-resensitization cycle of the GIPR variant, revealed in studies of cultured adipocytes, may contribute to the link of the E354Q variant to metabolic disease.
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142
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Boland JW, McWilliams K, Ahmedzai SH, Pockley AG. Effects of opioids on immunologic parameters that are relevant to anti-tumour immune potential in patients with cancer: a systematic literature review. Br J Cancer 2014; 111:866-73. [PMID: 25025960 PMCID: PMC4150281 DOI: 10.1038/bjc.2014.384] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 06/02/2014] [Accepted: 06/10/2014] [Indexed: 01/18/2023] Open
Abstract
Background: The immune system has a central role in controlling cancer, and factors that influence protective antitumour immunity could therefore have a significant impact on the course of malignant disease. Opioids are essential for the management of cancer pain, and preclinical studies indicate that opioids have the potential to influence these tumour immune surveillance mechanisms. The aim of this systematic literature review is to evaluate the clinical effects of opioids on the immune system of patients with cancer. Methods: A systematic search of Ovid MEDLINE (PubMed) and Embase, Cochrane database and Web of Knowledge for clinical studies, which evaluated the effects of opioids on the immune system in patients with cancer, was performed. Results: Five human studies, which have assessed the effects of opioids on the immune system in patients with cancer, were identified. Although all of these evaluated the effect of morphine on immunologic end points in patients with cancer, none measured the clinical effects. Conclusions: Evidence from preclinical, healthy volunteer and surgical models suggests that different opioids variably influence protective anti-tumour immunity; however, actual data derived from cancer populations are inconclusive and definitive recommendations cannot be made. Appropriately designed and powered studies assessing clinical outcomes of opioid use in people with cancer are therefore required to inform oncologists and others involved in cancer care about the rational use of opioids in this patient group.
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Affiliation(s)
- J W Boland
- Hull York Medical School, University of Hull, Hull HU6 7RX, UK
| | - K McWilliams
- Palliative Medicine Research Department, Beatson Oncology Centre, Glasgow G11 0YN, UK
| | - S H Ahmedzai
- Department of Oncology, The Medical School, University of Sheffield, Sheffield S10 2RX, UK
| | - A G Pockley
- John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham NG11 8NS, UK
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143
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Clark PJ, Ghasem PR, Mika A, Day HE, Herrera JJ, Greenwood BN, Fleshner M. Wheel running alters patterns of uncontrollable stress-induced cfos mRNA expression in rat dorsal striatum direct and indirect pathways: A possible role for plasticity in adenosine receptors. Behav Brain Res 2014; 272:252-63. [PMID: 25017571 DOI: 10.1016/j.bbr.2014.07.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 05/22/2014] [Accepted: 07/03/2014] [Indexed: 01/22/2023]
Abstract
Emerging evidence indicates that adenosine is a major regulator of striatum activity, in part, through the antagonistic modulation of dopaminergic function. Exercise can influence adenosine and dopamine activity, which may subsequently promote plasticity in striatum adenosine and dopamine systems. Such changes could alter activity of medium spiny neurons and impact striatum function. The purpose of this study was twofold. The first was to characterize the effect of long-term wheel running on adenosine 1 (A1R), adenosine 2A (A2AR), dopamine 1 (D1R), and dopamine 2 (D2R) receptor mRNA expression in adult rat dorsal and ventral striatum structures using in situ hybridization. The second was to determine if changes to adenosine and dopamine receptor mRNA from running are associated with altered cfos mRNA induction in dynorphin- (direct pathway) and enkephalin- (indirect pathway) expressing neurons of the dorsal striatum following stress exposure. We report that chronic running, as well as acute uncontrollable stress, reduced A1R and A2AR mRNA levels in the dorsal and ventral striatum. Running also modestly elevated D2R mRNA levels in striatum regions. Finally, stress-induced cfos was potentiated in dynorphin and attenuated in enkephalin expressing neurons of running rats. These data suggest striatum adenosine and dopamine systems are targets for neuroplasticity from exercise, which may contribute to changes in direct and indirect pathway activity. These findings may have implications for striatum mediated motor and cognitive processes, as well as exercise facilitated stress-resistance.
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Affiliation(s)
- Peter J Clark
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States.
| | - Parsa R Ghasem
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States
| | - Agnieszka Mika
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States
| | - Heidi E Day
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States; Department of Psychology & Neuroscience, University of Colorado Boulder, Muenzinger D244, 345 UCB, Boulder, CO 80309, United States
| | - Jonathan J Herrera
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States
| | - Benjamin N Greenwood
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States
| | - Monika Fleshner
- Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States
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144
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Knapman A, Connor M. Cellular signalling of non-synonymous single-nucleotide polymorphisms of the human μ-opioid receptor (OPRM1). Br J Pharmacol 2014; 172:349-63. [PMID: 24527749 DOI: 10.1111/bph.12644] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 01/21/2014] [Accepted: 02/07/2014] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED There is significant variability in individual responses to opioid drugs, which is likely to have a significant genetic component. A number of non-synonymous single-nucleotide polymorphisms (SNPs) in the coding regions of the μ-opioid receptor gene (OPRM1) have been postulated to contribute to this variability. Although many studies have investigated the clinical influences of these μ-opioid receptor variants, the outcomes are reported in the context of thousands of other genes and environmental factors, and we are no closer to being able to predict individual response to opioids based on genotype. Investigation of how μ-opioid receptor SNPs affect their expression, coupling to second messengers, desensitization and regulation is necessary to understand how subtle changes in receptor structure can impact individual responses to opioids. To date, the few functional studies that have investigated the consequences of SNPs on the signalling profile of the μ-opioid receptor in vitro have shown that the common N40D variant has altered functional responses to some opioids, while other, rarer, variants display altered signalling or agonist-dependent regulation. Here, we review the data available on the effects of μ-opioid receptor polymorphisms on receptor function, expression and regulation in vitro, and discuss the limitations of the studies to date. Whether or not μ-opioid receptor SNPs contribute to individual variability in opioid responses remains an open question, in large part because we have relatively little good data about how the amino acid changes affect μ-opioid receptor function. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Alisa Knapman
- Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
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145
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Cooke AE, Oldfield S, Krasel C, Mundell SJ, Henderson G, Kelly E. Morphine-induced internalization of the L83I mutant of the rat μ-opioid receptor. Br J Pharmacol 2014; 172:593-605. [PMID: 24697554 DOI: 10.1111/bph.12709] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 03/17/2014] [Accepted: 03/26/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND AND PURPOSE Naturally occurring single-nucleotide polymorphisms (SNPs) within GPCRs can result in alterations in various pharmacological parameters. Understanding the regulation and function of endocytic trafficking of the μ-opioid receptor (MOP receptor) is of great importance given its implication in the development of opioid tolerance. This study has compared the agonist-dependent trafficking and signalling of L83I, the rat orthologue of a naturally occurring variant of the MOP receptor. EXPERIMENTAL APPROACH Cell surface elisa, confocal microscopy and immunoprecipitation assays were used to characterize the trafficking properties of the MOP-L83I variant in comparison with the wild-type receptor in HEK 293 cells. Functional assays were used to compare the ability of the L83I variant to signal to several downstream pathways. KEY RESULTS Morphine-induced internalization of the L83I MOP receptor was markedly increased in comparison with the wild-type receptor. The altered trafficking of this variant was found to be specific to morphine and was both G-protein receptor kinase- and dynamin-dependent. The enhanced internalization of L83I variant in response to morphine was not due to increased phosphorylation of serine 375, arrestin association or an increased ability to signal. CONCLUSIONS AND IMPLICATIONS These results suggest that morphine promotes a specific conformation of the L83I variant that makes it more liable to internalize in response to morphine, unlike the wild-type receptor that undergoes significantly less morphine-stimulated internalization, providing an example of a ligand-selective biased receptor. The presence of this SNP within an individual may consequently affect the development of tolerance and analgesic responses. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- A E Cooke
- School of Physiology and Pharmacology, University of Bristol, Bristol, BS8 1TD, UK
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146
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Mann A, Illing S, Miess E, Schulz S. Different mechanisms of homologous and heterologous μ-opioid receptor phosphorylation. Br J Pharmacol 2014; 172:311-6. [PMID: 24517854 DOI: 10.1111/bph.12627] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 01/16/2014] [Accepted: 01/19/2014] [Indexed: 01/14/2023] Open
Abstract
UNLABELLED The efficiency of μ-opioid receptor signalling is tightly regulated and ultimately limited by the coordinated phosphorylation of intracellular serine and threonine residues. Here, we review and discuss recent progress in the generation and application of phosphosite-specific μ-opioid receptor antibodies, which have proved to be excellent tools for monitoring the spatial and temporal dynamics of receptor phosphorylation and dephosphorylation. Agonist-induced phosphorylation of μ-opioid receptors occurs at a conserved 10 residue sequence (370) TREHPSTANT(379) in the receptor's carboxyl-terminal cytoplasmic tail. Diverse opioids induce receptor phosphorylation at S375, present in the middle of this sequence, but only high-efficacy opioids have the ability to drive higher order phosphorylation on flanking residues (T370, T376 and T379). S375 is the initiating residue in a hierarchical phosphorylation cascade. In contrast, agonist-independent heterologous μ-opioid receptor phosphorylation occurs primarily at T370. The combination of phosphosite-specific antibodies and siRNA knockdown screening also facilitated the identification of relevant kinases and phosphatases. In fact, morphine induces a selective S375 phosphorylation that is predominantly catalysed by GPCR kinase 5 (GRK5), whereas multisite phosphorylation induced by high-efficacy opioids specifically requires GRK2/3. By contrast, T370 phosphorylation stimulated by phorbol esters or heterologous activation of Gq -coupled receptors is mediated by PKCα. Rapid μ-opioid receptor dephosphorylation occurs at or near the plasma membrane and is catalysed by protein phosphatase 1γ (PP1γ). These findings suggest that there are distinct phosphorylation motifs for homologous and heterologous regulation of μ-opioid receptor phosphorylation. However, it remains to be seen to what extent different μ-opioid receptor phosphorylation patterns contribute to the development of tolerance and dependence in vivo. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Anika Mann
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany
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147
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Macey TA, Bobeck EN, Suchland KL, Morgan MM, Ingram SL. Change in functional selectivity of morphine with the development of antinociceptive tolerance. Br J Pharmacol 2014; 172:549-61. [PMID: 24666417 DOI: 10.1111/bph.12703] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 03/14/2014] [Accepted: 03/18/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Opioids, such as morphine, are the most effective treatment for pain but their efficacy is diminished with the development of tolerance following repeated administration. Recently, we found that morphine activated ERK in opioid-tolerant but not in naïve rats, suggesting that morphine activation of μ-opioid receptors is altered following repeated morphine administration. Here, we have tested the hypothesis that μ-opioid receptor activation of ERK in the ventrolateral periaqueductal gray (vlPAG) is dependent on dynamin, a protein implicated in receptor endocytosis. EXPERIMENTAL APPROACH Rats were made tolerant to repeated microinjections of morphine into the vlPAG. The effects of dynamin on ERK activation and antinociception were assessed by microinjecting myristoylated dominant-negative dynamin peptide (Dyn-DN) or a scrambled control peptide into the vlPAG. Microinjection of a fluorescent dermorphin analogue (DERM-A594) into the vlPAG was used to monitor μ-opioid receptor internalization. KEY RESULTS Morphine did not activate ERK and Dyn-DN administration had no effect on morphine-induced antinociception in saline-pretreated rats. In contrast, morphine-induced ERK activation in morphine-pretreated rats that was blocked by Dyn-DN administration. Dyn-DN also inhibited morphine antinociception. Finally, morphine reduced DERM-A594 internalization only in morphine-tolerant rats indicating that μ-opioid receptors were internalized and unavailable to bind DERM-A594. CONCLUSIONS AND IMPLICATIONS Repeated morphine administration increased μ-opioid receptor activation of ERK signalling via a dynamin-dependent mechanism. These results demonstrate that the balance of agonist signalling to G-protein and dynamin-dependent pathways is altered, effectively changing the functional selectivity of the agonist-receptor complex. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- T A Macey
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA
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148
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Lowe JD, Bailey CP. Functional selectivity and time-dependence of μ-opioid receptor desensitization at nerve terminals in the mouse ventral tegmental area. Br J Pharmacol 2014; 172:469-81. [PMID: 24467517 PMCID: PMC4292961 DOI: 10.1111/bph.12605] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 01/08/2014] [Accepted: 01/17/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE The majority of studies examining desensitization of the μ-opioid receptor (MOR) have examined those located at cell bodies. However, MORs are extensively expressed at nerve terminals throughout the mammalian nervous system. This study is designed to investigate agonist-induced MOR desensitization at nerve terminals in the mouse ventral tegmental area (VTA). EXPERIMENTAL APPROACH MOR function was measured in mature mouse brain slices containing the VTA using whole-cell patch-clamp electrophysiology. Presynaptic MOR function was isolated from postsynaptic function and the functional selectivity, time-dependence and mechanisms of agonist-induced MOR desensitization were examined. KEY RESULTS MORs located at GABAergic nerve terminals in the VTA were completely resistant to rapid desensitization induced by the high-efficacy agonists DAMGO and Met-enkephalin. MORs located postsynaptically on GABAergic cell bodies readily underwent rapid desensitization in response to DAMGO. However, after prolonged (>7 h) treatment with Met-enkephalin, profound homologous MOR desensitization was observed. Morphine could induce rapid MOR desensitization at nerve terminals when PKC was activated. CONCLUSIONS AND IMPLICATIONS Agonist-induced MOR desensitization in GABAergic neurons in the VTA is compartment-selective as well as agonist-selective. When MORs are located at cell bodies, higher-efficacy agonists induce greater levels of rapid desensitization than lower-efficacy agonists. However, the converse is true at nerve terminals where agonists that induce MOR desensitization via PKC are capable of rapid agonist-induced desensitization while higher-efficacy agonists are not. MOR desensitization induced by higher-efficacy agonists at nerve terminals only takes place after prolonged receptor activation. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2
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Affiliation(s)
- J D Lowe
- Department of Pharmacy & Pharmacology, University of Bath, Bath, UK; School of Physiology & Pharmacology, University of Bristol, Bristol, UK
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149
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Fisher GW, Fuhrman MH, Adler SA, Szent-Gyorgyi C, Waggoner AS, Jarvik JW. Self-Checking Cell-Based Assays for GPCR Desensitization and Resensitization. ACTA ACUST UNITED AC 2014; 19:1220-6. [DOI: 10.1177/1087057114534299] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 04/09/2014] [Indexed: 11/15/2022]
Abstract
G protein–coupled receptors (GPCRs) play stimulatory or modulatory roles in numerous physiological states and processes, including growth and development, vision, taste and olfaction, behavior and learning, emotion and mood, inflammation, and autonomic functions such as blood pressure, heart rate, and digestion. GPCRs constitute the largest protein superfamily in the human and are the largest target class for prescription drugs, yet most are poorly characterized, and of the more than 350 nonolfactory human GPCRs, over 100 are orphans for which no endogenous ligand has yet been convincingly identified. We here describe new live-cell assays that use recombinant GPCRs to quantify two general features of GPCR cell biology—receptor desensitization and resensitization. The assays employ a fluorogen-activating protein (FAP) reporter that reversibly complexes with either of two soluble organic molecules (fluorogens) whose fluorescence is strongly enhanced when complexed with the FAP. Both assays require no wash or cleanup steps and are readily performed in microwell plates, making them adaptable to high-throughput drug discovery applications.
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Affiliation(s)
- Gregory W. Fisher
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Margaret H. Fuhrman
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Sally A. Adler
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Christopher Szent-Gyorgyi
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Alan S. Waggoner
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Jonathan W. Jarvik
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, USA
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150
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Jaremko KM, Thompson NL, Reyes BAS, Jin J, Ebersole B, Jenney CB, Grigson PS, Levenson R, Berrettini WH, Van Bockstaele EJ. Morphine-induced trafficking of a mu-opioid receptor interacting protein in rat locus coeruleus neurons. Prog Neuropsychopharmacol Biol Psychiatry 2014; 50:53-65. [PMID: 24333843 PMCID: PMC3928604 DOI: 10.1016/j.pnpbp.2013.12.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 11/26/2013] [Accepted: 12/05/2013] [Indexed: 12/14/2022]
Abstract
Opiate addiction is a devastating health problem, with approximately 2million people currently addicted to heroin or non-medical prescription opiates in the United States alone. In neurons, adaptations in cell signaling cascades develop following opioid actions at the mu opioid receptor (MOR). A novel putative target for intervention involves interacting proteins that may regulate trafficking of MOR. Morphine has been shown to induce a re-distribution of a MOR-interacting protein Wntless (WLS, a transport molecule necessary for secretion of neurotrophic Wnt proteins), from cytoplasmic to membrane compartments in rat striatal neurons. Given its opiate-sensitivity and its well-characterized molecular and cellular adaptations to morphine exposure, we investigated the anatomical distribution of WLS and MOR in the rat locus coeruleus (LC)-norepinephrine (NE) system. Dual immunofluorescence microscopy was used to test the hypothesis that WLS is localized to noradrenergic neurons of the LC and that WLS and MOR co-exist in common LC somatodendritic processes, providing an anatomical substrate for their putative interactions. We also hypothesized that morphine would influence WLS distribution in the LC. Rats received saline, morphine or the opiate agonist [d-Ala2, N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO), and tissue sections through the LC were processed for immunogold-silver detection of WLS and MOR. Statistical analysis showed a significant re-distribution of WLS to the plasma membrane following morphine treatment in addition to an increase in the proximity of gold-silver labels for MOR and WLS. Following DAMGO treatment, MOR and WLS were predominantly localized within the cytoplasmic compartment when compared to morphine and control. In a separate cohort of rats, brains were obtained from saline-treated or heroin self-administering male rats for pulldown co-immunoprecipitation studies. Results showed an increased association of WLS and MOR following heroin exposure. As the LC-NE system is important for cognition as well as decisions underlying substance abuse, adaptations in WLS trafficking and expression may play a role in modulating MOR function in the LC and contribute to the negative sequelae of opiate exposure on executive function.
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Affiliation(s)
- Kellie M Jaremko
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Nicholas L Thompson
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Beverly A S Reyes
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States.
| | - Jay Jin
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Brittany Ebersole
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Christopher B Jenney
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Patricia S Grigson
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Robert Levenson
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033, United States
| | - Wade H Berrettini
- Department of Psychiatry, Center for Neurobiology and Behavior, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, United States
| | - Elisabeth J Van Bockstaele
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
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