51
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Membrane-delimited proteolytic regulation of opioid receptors. Brain Res 2011; 1386:25-34. [DOI: 10.1016/j.brainres.2011.02.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/31/2011] [Accepted: 02/14/2011] [Indexed: 11/21/2022]
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52
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Abstract
The critical involvement of GPCRs (G-protein-coupled receptors) in nearly all physiological processes, and the presence of these receptors at the interface between the extracellular and the intracellular milieu, has positioned these receptors as pivotal therapeutic targets. Although a large number of drugs targeting GPCRs are currently available, significant efforts have been directed towards understanding receptor properties, with the goal of identifying and designing improved receptor ligands. Recent advances in GPCR pharmacology have demonstrated that different ligands binding to the same receptor can activate discrete sets of downstream effectors, a phenomenon known as 'ligand-directed signal specificity', which is currently being explored for drug development due to its potential therapeutic advantage. Emerging studies suggest that GPCR responses can also be modulated by contextual factors, such as interactions with other GPCRs. Association between different GPCR types leads to the formation of complexes, or GPCR heteromers, with distinct and unique signalling properties. Some of these heteromers activate discrete sets of signalling effectors upon activation by the same ligand, a phenomenon termed 'heteromer-directed signalling specificity'. This has been shown to be involved in the physiological role of receptors and, in some cases, in disease-specific dysregulation of a receptor effect. Hence targeting GPCR heteromers constitutes an emerging strategy to select receptor-specific responses and is likely to be useful in achieving specific beneficial therapeutic effects.
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53
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Zheng H, Chu J, Zhang Y, Loh HH, Law PY. Modulating micro-opioid receptor phosphorylation switches agonist-dependent signaling as reflected in PKCepsilon activation and dendritic spine stability. J Biol Chem 2011; 286:12724-33. [PMID: 21292762 DOI: 10.1074/jbc.m110.177089] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A new role of G protein-coupled receptor (GPCR) phosphorylation was demonstrated in the current studies by using the μ-opioid receptor (OPRM1) as a model. Morphine induces a low level of receptor phosphorylation and uses the PKCε pathway to induce ERK phosphorylation and receptor desensitization, whereas etorphine, fentanyl, and [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) induce extensive receptor phosphorylation and use the β-arrestin2 pathway. Blocking OPRM1 phosphorylation (by mutating Ser363, Thr370 and Ser375 to Ala) enabled etorphine, fentanyl, and DAMGO to use the PKCε pathway. This was not due to the decreased recruitment of β-arrestin2 to the receptor signaling complex, because these agonists were unable to use the PKCε pathway when β-arrestin2 was absent. In addition, overexpressing G protein-coupled receptor kinase 2 (GRK2) decreased the ability of morphine to activate PKCε, whereas overexpressing dominant-negative GRK2 enabled etorphine, fentanyl, and DAMGO to activate PKCε. Furthermore, by overexpressing wild-type OPRM1 and a phosphorylation-deficient mutant in primary cultures of hippocampal neurons, we demonstrated that receptor phosphorylation contributes to the differential effects of agonists on dendritic spine stability. Phosphorylation blockage made etorphine, fentanyl, and DAMGO function as morphine in the primary cultures. Therefore, agonist-dependent phosphorylation of GPCR regulates the activation of the PKC pathway and the subsequent responses.
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Affiliation(s)
- Hui Zheng
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455-0217, USA.
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54
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Tumati S, Roeske WR, Largent-Milnes T, Wang R, Vanderah TW, Varga EV. Sustained morphine-mediated pain sensitization and antinociceptive tolerance are blocked by intrathecal treatment with Raf-1-selective siRNA. Br J Pharmacol 2010; 161:51-64. [PMID: 20718739 DOI: 10.1111/j.1476-5381.2010.00869.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Long-term morphine treatment enhances pain neurotransmitter [such as calcitonin gene-related peptide (CGRP)] levels in the spinal cord. It has been suggested previously that increased spinal CGRP may contribute to sustained morphine-mediated paradoxical pain sensitization and antinociceptive tolerance. Previous in vitro studies from our group indicated that Raf-1 kinase-mediated adenylyl cyclase superactivation played a crucial role in sustained morphine-mediated augmentation of basal and evoked CGRP release from cultured primary sensory neurons. The present study was aimed to evaluate the physiological significance of this molecular mechanism in vivo, in rats. EXPERIMENTAL APPROACH Rats were intrathecally (i.th) injected with a Raf-1-selective small interfering RNA (siRNA) mixture for 3 days and were subsequently infused with saline or morphine, s.c. for 7 days. Thermal and mechanical sensory thresholds of the animals were assessed by daily behavioural tests. After final behavioural testing (day 6), spinal cords were isolated from each animal group and spinal CGRP and Raf-1 protein levels were measured using elisa and immunohistochemistry. KEY RESULTS Selective knockdown of spinal Raf-1 protein levels by i.th Raf-1-selective siRNA pretreatment significantly attenuated sustained morphine-mediated up-regulation of CGRP immunoreactivity in the spinal cord of rats and prevented the development of thermal hyperalgesia, mechanical allodynia and antinociceptive tolerance. CONCLUSIONS AND IMPLICATIONS Raf-1 played a significant role in sustained morphine-mediated paradoxical pain sensitization and antinociceptive tolerance in vivo. These findings suggest novel pharmacological approaches to improve the long-term utility of opioids in the treatment of chronic pain.
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Affiliation(s)
- S Tumati
- Department of Pharmacology, The University of Arizona, Tucson, AZ, USA
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55
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Bou Khalil M, Hou W, Zhou H, Elisma F, Swayne LA, Blanchard AP, Yao Z, Bennett SAL, Figeys D. Lipidomics era: accomplishments and challenges. MASS SPECTROMETRY REVIEWS 2010; 29:877-929. [PMID: 20931646 DOI: 10.1002/mas.20294] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Lipid mediators participate in signal transduction pathways, proliferation, apoptosis, and membrane trafficking in the cell. Lipids are highly complex and diverse owing to the various combinations of polar headgroups, fatty acyl chains, and backbone structures. This structural diversity continues to pose a challenge for lipid analysis. Here we review the current state of the art in lipidomics research and discuss the challenges facing this field. The latest technological developments in mass spectrometry, the role of bioinformatics, and the applications of lipidomics in lipid metabolism and cellular physiology and pathology are also discussed.
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Affiliation(s)
- Maroun Bou Khalil
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5
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56
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Spartà A, Baiula M, Campbell G, Spampinato S. β-Arrestin 2-mediated heterologous desensitization of IGF-IR by prolonged exposure of SH-SY5Y neuroblastoma cells to a mu opioid agonist. FEBS Lett 2010; 584:3580-6. [DOI: 10.1016/j.febslet.2010.07.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 07/14/2010] [Accepted: 07/15/2010] [Indexed: 12/22/2022]
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57
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Zheng H, Zeng Y, Chu J, Kam AY, Loh HH, Law PY. Modulations of NeuroD activity contribute to the differential effects of morphine and fentanyl on dendritic spine stability. J Neurosci 2010; 30:8102-10. [PMID: 20554861 PMCID: PMC2913383 DOI: 10.1523/jneurosci.6069-09.2010] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 03/25/2010] [Accepted: 03/30/2010] [Indexed: 01/14/2023] Open
Abstract
The cellular level of neurogenic differentiation 1 (NeuroD) is modulated differentially by mu-opioid receptor agonists; fentanyl increases NeuroD level by reducing the amount of microRNA-190 (miR-190), an inhibitor of NeuroD expression, whereas morphine does not alter NeuroD level. In the current study, NeuroD activity was demonstrated to be also under agonist-dependent regulation. After 3 d of treatment, morphine and fentanyl decreased the activity of the Ca(2+)/calmodulin-dependent protein kinase II alpha (CaMKIIalpha), which phosphorylates and activates NeuroD. Because NeuroD activity is determined by both the CaMKIIalpha activity and the cellular NeuroD level, the overall NeuroD activity was reduced by morphine, but maintained during fentanyl treatment. The differential effects of agonists on NeuroD activity were further confirmed by measuring the mRNA levels of four NeuroD downstream targets: doublecortin, Notch1, neurogenic differentiation 4, and Roundabout 1. Decreased dendritic spine stability and mu-opioid receptor signaling capability were also observed when NeuroD activity was attenuated by miR-190 overexpression or treatment with KN93, a CaMKIIalpha inhibitor. The decrease could be rescued by NeuroD overexpression, which restored NeuroD activity to the basal level. Furthermore, elevating NeuroD activity attenuated the morphine-induced decrease in dendritic spine stability. Therefore, by regulating NeuroD activity, mu-opioid receptor agonists modulate the stability of dendritic spines.
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MESH Headings
- Animals
- Basic Helix-Loop-Helix Transcription Factors/genetics
- Basic Helix-Loop-Helix Transcription Factors/metabolism
- Benzylamines/pharmacology
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Cells, Cultured
- Dendritic Spines/drug effects
- Dendritic Spines/physiology
- Dose-Response Relationship, Drug
- Doublecortin Domain Proteins
- Doublecortin Protein
- Enzyme Inhibitors/pharmacology
- Fentanyl/pharmacology
- Gene Expression Regulation/drug effects
- Green Fluorescent Proteins/genetics
- Hippocampus/cytology
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Morphine/pharmacology
- Narcotics/pharmacology
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neurons/drug effects
- Neurons/metabolism
- Neurons/ultrastructure
- Neuropeptides/genetics
- Neuropeptides/metabolism
- Phosphorylation/drug effects
- RNA, Messenger/metabolism
- Rats
- Receptor, Notch1/genetics
- Receptor, Notch1/metabolism
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Opioid, mu/metabolism
- Sulfonamides/pharmacology
- Time Factors
- Transduction, Genetic/methods
- Roundabout Proteins
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Affiliation(s)
- Hui Zheng
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455-0217, USA.
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58
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Berger AC, Whistler JL. How to design an opioid drug that causes reduced tolerance and dependence. Ann Neurol 2010; 67:559-69. [PMID: 20437553 DOI: 10.1002/ana.22002] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mu opioid receptor (MOR) agonists such as morphine are extremely effective treatments for acute pain. In the setting of chronic pain, however, their long-term utility is limited by the development of tolerance and physical dependence. Drug companies have tried to overcome these problems by simply "dialing up" signal transduction at the receptor, designing more potent and efficacious agonists and more long-lasting formulations. Neither of these strategies has proven to be successful, however, because the net amount of signal transduction, particularly over extended periods of drug use, is a product of much more than the pharmacokinetic properties of potency, efficacy, half-life, and bioavailability, the mainstays of traditional pharmaceutical screening. Both the quantity and quality of signal transduction are influenced by many regulated processes, including receptor desensitization, trafficking, and oligomerization. Importantly, the efficiency with which an agonist first stimulates signal transduction is not necessarily related to the efficiency with which it stimulates these other processes. Here we describe recent findings that suggest MOR agonists with diminished propensity to cause tolerance and dependence can be identified by screening drugs for the ability to induce MOR desensitization, endocytosis, and recycling. We also discuss preliminary evidence that heteromers of the delta opioid receptor and the MOR are pronociceptive, and that drugs that spare such heteromers may also induce reduced tolerance.
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Affiliation(s)
- Amy Chang Berger
- Department of Neurology, University of California, San Francisco, Ernest Gallo Clinic and Research Center, Emeryville, CA, USA
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59
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Zheng H, Chu J, Zeng Y, Loh HH, Law PY. Yin Yang 1 phosphorylation contributes to the differential effects of mu-opioid receptor agonists on microRNA-190 expression. J Biol Chem 2010; 285:21994-2002. [PMID: 20457614 DOI: 10.1074/jbc.m110.112607] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Mu-opioid receptor regulates microRNA-190 (miR-190) in an agonist-dependent manner; fentanyl, but not morphine, decreases the miR-190 level in rat primary hippocampal neuron cultures and in mouse hippocampi. In this study, the correlation between the cellular content of miR-190 and the mRNA level of its host gene, talin2, suggested that fentanyl decreases the miR-190 level by inhibiting the transcription of talin2. Fentanyl-induced beta-arrestin2-mediated ERK phosphorylation led to the phosphorylation of Yin Yang 1 (YY1). In addition, YY1 phosphorylation impaired the association of YY1 with the -208 to -200 region on the Talin2 promoter, and this association was essential for YY1 to stimulate the transcription of talin2. Thus, fentanyl decreased the transcription of talin2 and subsequently the cellular level of miR-190 by inducing YY1 phosphorylation. In contrast, because morphine induces ERK phosphorylation via the protein kinase C pathway, morphine did not induce YY1 phosphorylation and had no effect on the transcription of talin2 and the cellular content of miR-190. This study therefore delineates a signaling pathway that mediates the effects of fentanyl on miR-190 expression.
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Affiliation(s)
- Hui Zheng
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455-0217, USA.
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60
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Zheng H, Loh HH, Law PY. Agonist-selective signaling of G protein-coupled receptor: mechanisms and implications. IUBMB Life 2010; 62:112-9. [PMID: 20058265 DOI: 10.1002/iub.293] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Agonist-selective signaling or ligand-biased signaling of G protein-coupled receptor (GPCR) has become the focus of an increasing number of laboratories. The principle of this concept is that agonist possesses different abilities to activate different signaling pathways. Current review summarizes the observations of agonist-selective signaling of various GPCRs, indicating the significance of agonist-selective signaling in biological processes. In addition, current review also provides an overview on how agonist-selective signaling is initiated. Especially, the relationship between GPCR-G protein interaction and GPCR-beta-arrestin interaction is discussed in depth.
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Affiliation(s)
- Hui Zheng
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455-0217, USA.
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61
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Chu J, Zheng H, Zhang Y, Loh HH, Law PY. Agonist-dependent mu-opioid receptor signaling can lead to heterologous desensitization. Cell Signal 2010; 22:684-96. [PMID: 20043990 DOI: 10.1016/j.cellsig.2009.12.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 12/07/2009] [Accepted: 12/19/2009] [Indexed: 12/18/2022]
Abstract
Desensitization of the micro-opioid receptor (MOR) has been implicated as an important regulatory process in the development of tolerance to opiates. Monitoring the release of intracellular Ca(2+) ([Ca(2+)](i)), we reported that [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO)-induced receptor desensitization requires receptor phosphorylation and recruitment of beta-arrestins (betaArrs), while morphine-induced receptor desensitization does not. In current studies, we established that morphine-induced MOR desensitization is protein kinase C (PKC)-dependent. By using RNA interference techniques and subtype specific inhibitors, PKCepsilon was shown to be the PKC subtype activated by morphine and the subtype responsible for morphine-induced desensitization. In contrast, DAMGO did not increase PKCepsilon activity and DAMGO-induced MOR desensitization was not affected by modulating PKCepsilon activity. Among the various proteins within the receptor signaling complex, Galphai2 was phosphorylated by morphine-activated PKCepsilon. Moreover, mutating three putative PKC phosphorylation sites, Ser(44), Ser(144) and Ser(302) on Galphai2 to Ala attenuated morphine-induced, but not DAMGO-induced desensitization. In addition, pretreatment with morphine desensitized cannabinoid receptor CB1 agonist WIN 55212-2-induced [Ca(2+)](i) release, and this desensitization could be reversed by pretreating the cells with PKCepsilon inhibitor or overexpressing Galphai2 with the putative PKC phosphorylation sites mutated. Thus, depending on the agonist, activation of MOR could lead to heterologous desensitization and probable crosstalk between MOR and other Galphai-coupled receptors, such as the CB1.
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Affiliation(s)
- Ji Chu
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church St. S.E., Minneapolis, Minnesota 55455-0217, USA.
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62
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Abstract
This paper is the 31st consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2008 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd, Flushing, NY 11367, United States.
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63
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Ge X, Qiu Y, Loh HH, Law PY. GRIN1 regulates micro-opioid receptor activities by tethering the receptor and G protein in the lipid raft. J Biol Chem 2009; 284:36521-36534. [PMID: 19861419 DOI: 10.1074/jbc.m109.024109] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The lipid raft location of mu-opioid receptor (MOR) determines the receptor activities. However, the manner in which MOR is anchored within the lipid rafts is undetermined. Using the targeted proteomic approach and mass spectrometry analyses, we have identified GRIN1 (G protein-regulated inducer of neurite outgrowth 1) can tether MOR with the G protein alpha-subunit and subsequently regulate the receptor distribution within the lipid rafts. Glutathione S-transferase fusion pulldown and receptor mutational analyses indicate that GRIN1-MOR interaction involves a receptor sequence (267)GSKEK(271) within the MOR third intracellular loop that is not involved in Galpha interaction. The GRIN1 domains involved in MOR interaction are also distinct from those involved in Galpha interaction. Pertussis toxin pretreatment reduced the amount of GRIN1 co-immunoprecipitated with MOR but not the amount with Galpha. Furthermore, overexpression of GRIN1 significantly enhanced the amount of MOR in lipid raft and the receptor signaling magnitude as measured by Src kinase activation. Such increase in MOR signaling was demonstrated further by determining the GRIN1-dependent pertussis toxin-sensitive neurite outgrowth. In contrast to minimal neurite outgrowth induced by etorphine in control neuroblastoma N2A cells, overexpression of GRIN1 resulted in the increase in etorphine- and non-morphine-induced neurite outgrowth in these cells. Knocking down endogenous GRIN1 by small interfering RNA attenuated the agonist-induced neurite outgrowth. Disrupting lipid raft by methyl-beta-cyclodextrin also blocked neurite outgrowth. Hence, by tethering Galpha with MOR, GRIN1 stabilizes the receptor within the lipid rafts and potentiates the receptor signaling in the neurite outgrowth processes.
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Affiliation(s)
- Xin Ge
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455.
| | - Yu Qiu
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455
| | - Horace H Loh
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455
| | - Ping-Yee Law
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455
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64
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Zheng H, Zeng Y, Zhang X, Chu J, Loh HH, Law PY. mu-Opioid receptor agonists differentially regulate the expression of miR-190 and NeuroD. Mol Pharmacol 2009; 77:102-9. [PMID: 19854889 DOI: 10.1124/mol.109.060848] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The agonists of mu-opioid receptor (OPRM1) induce extracellular signal-regulated kinase (ERK) phosphorylation through different pathways: morphine uses the protein kinase C (PKC)-pathway, whereas fentanyl functions in a beta-arrestin2-dependent manner. In addition, the two pathways result in the different cellular location of phosphorylated ERK and the activation of different sets of transcriptional factors. In the current study, the influence of the two pathways on the expression of microRNAs (miRNAs) was investigated. After treating the primary culture of rat hippocampal neurons and the mouse hippocampi with morphine or fentanyl for 3 days, seven miRNAs regulated by one or two of the agonists were identified. One of the identified miRNAs, miR-190, was down-regulated by fentanyl but not by morphine. This down-regulation was attenuated by 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U0126), which blocks the phosphorylation of ERK. When fentanyl-induced but not morphine-induced ERK phosphorylation was blocked in the primary cultures from beta-arrestin2(-/-) mouse, fentanyl did not decrease the expression of miR-190. However, a PKC inhibitor that blocked morphine-induced ERK phosphorylation specifically had no effect on the miR-190 down-regulation. Therefore the decrease in miR-190 expression resulted from the agonist-selective ERK phosphorylation. In addition, the expressional changes in one of the miR-190 targets, neurogenic differentiation 1 (NeuroD), correlated with those in miR-190 expression, suggesting the OPRM1 could regulate the NeuroD pathways via the control of miR-190 expression.
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Affiliation(s)
- Hui Zheng
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455-0217, USA.
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65
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van Rijn RM, Whistler JL, Waldhoer M. Opioid-receptor-heteromer-specific trafficking and pharmacology. Curr Opin Pharmacol 2009; 10:73-9. [PMID: 19846340 DOI: 10.1016/j.coph.2009.09.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 09/16/2009] [Accepted: 09/17/2009] [Indexed: 12/22/2022]
Abstract
Homomerization and heteromerization of 7 transmembrane spanning (7TM)/G-protein-coupled receptors (GPCRs) have been an important field of study. Whereas initial studies were performed in artificial cell systems, recent publications are shifting the focus to the in vivo relevance of heteromerization. This is especially apparent for the field of opioid receptors. Drugs have been identified that selectively target opioid heteromers of the delta-opioid receptor with the kappa and the mu-opioid receptors that influence nociception and ethanol consumption, respectively. In addition, in several cases, the specific physiological response produced by the heteromer may be directly attributed to a difference in receptor trafficking properties of the heteromers compared with their homomeric counterparts. This review attempts to highlight some of the latest developments with regard to opioid receptor heteromer trafficking and pharmacology.
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Affiliation(s)
- Richard M van Rijn
- Ernest Gallo Clinic and Research Center, University of California San Francisco, Department of Neurology, Emeryville, CA 94608, USA
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66
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Eisinger DA, Ammer H. Down-regulation of c-Cbl by morphine accounts for persistent ERK1/2 signaling in delta-opioid receptor-expressing HEK293 cells. J Biol Chem 2009; 284:34819-28. [PMID: 19828455 DOI: 10.1074/jbc.m109.042937] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Opioids display ligand-specific differences in the time course of ERK1/2 signaling. Whereas full agonists, like etorphine, induce only transient activation of ERK1/2, the partial agonist morphine mediates persistent stimulation of mitogenic signaling. Here we report that in stably delta-opioid receptor (DOR)-expressing HEK293 (HEK/DOR) cells, the transient nature of etorphine-induced ERK1/2 signaling is due to desensitization of epidermal growth factor (EGF) receptor-mediated activation of the Ras/Raf-1/ERK1/2 cascade. Desensitization of ERK1/2 activity by etorphine is associated with down-regulation of EGF receptors, an effect mediated by the ubiquitin ligase c-Cbl. In contrast, chronic morphine treatment failed to desensitize EGF receptors, resulting in unimpeded ERK1/2 signaling. The failure of morphine to desensitize ERK1/2 signaling is mediated by persistent activation of c-Src, which induces degradation of c-Cbl. The role of c-Src in opioid-specific ERK1/2 signaling is further demonstrated by pretreatment of the cells with PP2 and SKI-I as well as overexpression of a dominant negative c-Src mutant (c-Src(dn)) or a c-Src-resistant c-Cbl mutant (CblY3F), both of which facilitate desensitization of ERK1/2 signaling by morphine. Conversely, overexpression of c-Src as well as down-regulation of c-Cbl by small interfering RNA results in persistent etorphine-induced stimulation of ERK1/2 activity. Subcellular fractionation experiments finally attributed the ability of morphine to persistently activate c-Src to its redistribution from Triton X-100-insensitive membrane rafts to DOR and EGF receptor containing high density membrane compartments implicated in ERK1/2 signaling. These results demonstrate that agonist-specific differences in the temporal and spatial pattern of c-Src activation determine the kinetics of DOR-mediated regulation of ERK1/2 signaling.
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Affiliation(s)
- Daniela A Eisinger
- Institute of Pharmacology, Toxicology and Pharmacy, Ludwig-Maximilians-University Munich, 80539 Muenchen, Germany.
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67
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Lam RS, Nahirney D, Duszyk M. Cholesterol-dependent regulation of adenosine A2A receptor-mediated anion secretion in colon epithelial cells. Exp Cell Res 2009; 315:3028-35. [DOI: 10.1016/j.yexcr.2009.06.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 06/08/2009] [Accepted: 06/08/2009] [Indexed: 11/29/2022]
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68
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Kendall RT, Luttrell LM. Diversity in arrestin function. Cell Mol Life Sci 2009; 66:2953-73. [PMID: 19597700 PMCID: PMC11115578 DOI: 10.1007/s00018-009-0088-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 05/09/2009] [Accepted: 05/12/2009] [Indexed: 01/08/2023]
Abstract
The termination of heptahelical receptor signaling is a multilevel process coordinated, in large part, by members of the arrestin family of proteins. Arrestin binding to agonist-occupied receptors promotes desensitization by interrupting receptor-G protein coupling, while simultaneously recruiting machinery for receptor endocytosis, vesicular trafficking, and receptor fate determination. By simultaneously binding other proteins, arrestins also act as ligand-regulated scaffolds that recruit protein and lipid kinase, phosphatase, phosphodiesterase, and ubiquitin ligase activity into receptor-based multiprotein 'signalsome' complexes. Arrestin-binding thus 'switches' receptors from a transient G protein-coupled state to a persistent arrestin-coupled state that continues to signal as the receptor transits intracellular compartments. While it is clear that signalsome assembly has profound effects on the duration and spatial characteristics of heptahelical receptor signals, the physiologic functions of this novel signaling mechanism are poorly understood. Growing evidence suggests that signalsomes regulate such diverse processes as endocytosis and exocytosis, cell migration, survival, and contractility.
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Affiliation(s)
- Ryan T. Kendall
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425 USA
| | - Louis M. Luttrell
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425 USA
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425 USA
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401 USA
- Division of Endocrinology, Diabetes and Medical Genetics, Medical University of South Carolina, 96 Jonathan Lucas Street, Suite 816 CSB, MSC 624, Charleston, SC 29425 USA
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Boxer SG, Kraft ML, Weber PK. Advances in imaging secondary ion mass spectrometry for biological samples. Annu Rev Biophys 2009; 38:53-74. [PMID: 19086820 DOI: 10.1146/annurev.biophys.050708.133634] [Citation(s) in RCA: 206] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Imaging mass spectrometry combines the power of mass spectrometry to identify complex molecules based on mass with sample imaging. Recent advances in secondary ion mass spectrometry have improved sensitivity and spatial resolution, so that these methods have the potential to bridge between high-resolution structures obtained by X-ray crystallography and cyro-electron microscopy and ultrastructure visualized by conventional light microscopy. Following background information on the method and instrumentation, we address the key issue of sample preparation. Because mass spectrometry is performed in high vacuum, it is essential to preserve the lateral organization of the sample while removing bulk water, and this has been a major barrier for applications to biological systems. Recent applications of imaging mass spectrometry to cell biology, microbial communities, and biosynthetic pathways are summarized briefly, and studies of biological membrane organization are described in greater depth.
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Affiliation(s)
- Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
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Correll JA, Noel DM, Sheppard AB, Thompson KN, Li Y, Yin D, Brown RW. Nicotine sensitization and analysis of brain-derived neurotrophic factor in adolescent beta-arrestin-2 knockout mice. Synapse 2009; 63:510-9. [PMID: 19224602 DOI: 10.1002/syn.20625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nicotine sensitization and levels of brain-derived neurotrophic factor (BDNF) were analyzed in adolescent beta-arrestin-2 knockout (betaA-2 KO) and wild type (WT) mice. The beta-arrestin-2 protein has been shown to be important in G-protein hydrolysis and receptor internalization. Four- to five-week-old adolescent betaA-2 KO and WT C57/Bl6 mice were administered either nicotine (0.5 mg/kg free base) or saline 10 min before being placed into a locomotor arena on each of 7 (Experiment 1) or 14 (Experiment 2) consecutive days. A nicotine challenge was given 7 days after sensitization was complete. In Experiment 1, betaA-2 KO mice administered nicotine or saline and WT mice administered nicotine demonstrated significant hypoactivity during early in testing, and neither WT nor betaA-2 KO mice administered nicotine demonstrated sensitization. On the nicotine challenge, WT mice administered nicotine demonstrated significantly higher activity levels compared to all groups, and this same group demonstrated significantly higher levels of accumbal BDNF compared to all groups. In Experiment 2, betaA-2 KO mice were again hypoactive compared to WT mice, whereas WT mice administered nicotine demonstrated significant hypoactivity during initial testing and significantly higher levels of activity compared to all other groups late in testing. On the nicotine challenge, WT mice that received nicotine demonstrated a significant increase in activity compared to all groups, and showed increased accumbal BDNF compared to all groups. These results show that the beta-arrestin-2 protein is important in induction and expression of nicotine sensitization as well as nicotine's effects on accumbal BDNF.
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Affiliation(s)
- Jennifer A Correll
- Department of Psychology, East Tennessee State University, Johnson City, Tennessee 37614, USA
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71
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Russo A, Soh UJK, Trejo J. Proteases display biased agonism at protease-activated receptors: location matters! Mol Interv 2009; 9:87-96. [PMID: 19401541 DOI: 10.1124/mi.9.2.8] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Protease-activated receptors (PARs) are G protein-coupled receptors (GPCRs) that transmit cellular responses begun by the actions of extracellular proteases. The activation of a PAR occurs by a unique mechanism whereby the extracellular N-terminal segment of the inactive receptor undergoes proteolytic cleavage, resulting in irreversible activation--unlike most GPCRs that are reversibly activated. PARs mediate cellular responses to coagulant proteases in various cell types localized within the vasculature. Additionally, PARs are expressed in other cell types and respond to a plethora of proteases. Recent studies have revealed that different proteases elicit distinct responses through the activation of the same PAR. This phenomenon appears to involve stabilization of distinct active PAR conformations that facilitates selectively coupling to different effectors and is localized to caveolae, a subtype of lipid rafts.
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Affiliation(s)
- Angela Russo
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
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Zhang L, Brass LF, Manning DR. The Gq and G12 families of heterotrimeric G proteins report functional selectivity. Mol Pharmacol 2008; 75:235-41. [PMID: 18952767 DOI: 10.1124/mol.108.050906] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Receptors coupled to the G(q) and G(12) families of heterotrimeric G proteins have surfaced rarely in the context of functional selectivity and always indirectly. We explore here the differential engagement of G(q) and G(13) (of the G(12) family) by the thromboxane A(2) receptor alpha (TPalpha), via agonist-effected [(35)S]-guanosine 5'-O-(3-thio)triphosphate binding when the G proteins themselves are used as reporters. We find for TPalpha introduced into human embryonic kidney 293 cells and for the receptor expressed normally in human platelets an agonist-selective engagement of G(q) versus G(13). Pinane thromboxane A(2) (PTA(2)) activates G(q) in preference to G(13), whereas 8-iso-prostaglandin F(2alpha) activates G(13) in preference to G(q). 9,11-Dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid (U46619), in contrast, exhibits no preference. Reserve of receptor in relation to G protein and of G protein in relation to downstream events is apparent in some instances but does not have a bearing on selectivity. Activation of G proteins by PTA(2) is right-shifted from binding of the ligand to receptor, a manifestation of which is a bimodal action: PTA(2) is an antagonist at low concentrations and an agonist at higher concentrations. We posit two populations of TPalpha, or two intrinsic sites of ligand binding, with selectivity evident not only in terms of the G proteins activated but properties of antagonism versus agonism.
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Affiliation(s)
- Li Zhang
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
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