1
|
Kagiampaki Z, Rohner V, Kiss C, Curreli S, Dieter A, Wilhelm M, Harada M, Duss SN, Dernic J, Bhat MA, Zhou X, Ravotto L, Ziebarth T, Wasielewski LM, Sönmez L, Benke D, Weber B, Bohacek J, Reiner A, Wiegert JS, Fellin T, Patriarchi T. Sensitive multicolor indicators for monitoring norepinephrine in vivo. Nat Methods 2023; 20:1426-1436. [PMID: 37474807 PMCID: PMC7615053 DOI: 10.1038/s41592-023-01959-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 06/16/2023] [Indexed: 07/22/2023]
Abstract
Genetically encoded indicators engineered from G-protein-coupled receptors are important tools that enable high-resolution in vivo neuromodulator imaging. Here, we introduce a family of sensitive multicolor norepinephrine (NE) indicators, which includes nLightG (green) and nLightR (red). These tools report endogenous NE release in vitro, ex vivo and in vivo with improved sensitivity, ligand selectivity and kinetics, as well as a distinct pharmacological profile compared with previous state-of-the-art GRABNE indicators. Using in vivo multisite fiber photometry recordings of nLightG, we could simultaneously monitor optogenetically evoked NE release in the mouse locus coeruleus and hippocampus. Two-photon imaging of nLightG revealed locomotion and reward-related NE transients in the dorsal CA1 area of the hippocampus. Thus, the sensitive NE indicators introduced here represent an important addition to the current repertoire of indicators and provide the means for a thorough investigation of the NE system.
Collapse
Affiliation(s)
| | - Valentin Rohner
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Cedric Kiss
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Sebastiano Curreli
- Optical Approaches to Brain Function Laboratory, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Alexander Dieter
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Neurophysiology, MCTN, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Maria Wilhelm
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Masaya Harada
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Sian N Duss
- Institute for Neuroscience, Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland
| | - Jan Dernic
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Musadiq A Bhat
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Xuehan Zhou
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Luca Ravotto
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
| | - Tim Ziebarth
- Cellular Neurobiology, Department of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Laura Moreno Wasielewski
- Cellular Neurobiology, Department of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Latife Sönmez
- Cellular Neurobiology, Department of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
- Neuroscience Center Zurich, University and ETH Zürich, Zürich, Switzerland
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland
- Neuroscience Center Zurich, University and ETH Zürich, Zürich, Switzerland
| | - Johannes Bohacek
- Institute for Neuroscience, Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland
- Neuroscience Center Zurich, University and ETH Zürich, Zürich, Switzerland
| | - Andreas Reiner
- Cellular Neurobiology, Department of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - J Simon Wiegert
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Neurophysiology, MCTN, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Tommaso Fellin
- Optical Approaches to Brain Function Laboratory, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Tommaso Patriarchi
- Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland.
- Neuroscience Center Zurich, University and ETH Zürich, Zürich, Switzerland.
| |
Collapse
|
2
|
Chetwynd SA, Andrews S, Inglesfield S, Delon C, Ktistakis NT, Welch HCE. Functions and mechanisms of the GPCR adaptor protein Norbin. Biochem Soc Trans 2023; 51:1545-1558. [PMID: 37503670 PMCID: PMC10586782 DOI: 10.1042/bst20221349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/27/2023] [Accepted: 07/07/2023] [Indexed: 07/29/2023]
Abstract
Norbin (Neurochondrin, NCDN) is a highly conserved 79 kDa adaptor protein that was first identified more than a quarter of a century ago as a gene up-regulated in rat hippocampus upon induction of long-term potentiation. Most research has focussed on the role of Norbin in the nervous system, where the protein is highly expressed. Norbin regulates neuronal morphology and synaptic plasticity, and is essential for normal brain development and homeostasis. Dysregulation of Norbin is linked to a variety of neurological conditions. Recently, Norbin was shown to be expressed in myeloid cells as well as neurons. Myeloid-cell specific deletion revealed an important role of Norbin as a suppressor of neutrophil-derived innate immunity. Norbin limits the ability of neutrophils to clear bacterial infections by curbing the responsiveness of these cells to inflammatory and infectious stimuli. Mechanistically, Norbin regulates cell responses through binding to its interactors, in particular to a wide range of G protein-coupled receptors (GPCRs). Norbin association with GPCRs controls GPCR trafficking and signalling. Other important Norbin interactors are the Rac guanine-nucleotide exchange factor P-Rex1 and protein kinase A. Downstream signalling pathways regulated by Norbin include ERK, Ca2+ and the small GTPase Rac. Here, we review the current understanding of Norbin structure, expression and its roles in health and disease. We also explore Norbin signalling through its interactors, with a particular focus on GPCR trafficking and signalling. Finally, we discuss avenues that could be pursued in the future to increase our understanding of Norbin biology.
Collapse
Affiliation(s)
| | - Simon Andrews
- Bioinformatics Facility, Babraham Institute, Cambridge, U.K
| | | | | | | | | |
Collapse
|
3
|
Chmielarz P, Kuśmierczyk J, Rafa-Zabłocka K, Chorązka K, Kowalska M, Satała G, Nalepa I. Antidepressants Differentially Regulate Intracellular Signaling from α1-Adrenergic Receptor Subtypes In Vitro. Int J Mol Sci 2021; 22:ijms22094817. [PMID: 34062902 PMCID: PMC8124549 DOI: 10.3390/ijms22094817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 11/16/2022] Open
Abstract
Currently utilized antidepressants have limited effectiveness and frequently incur undesired effects. Most antidepressants are thought to act via the inhibition of monoamine reuptake; however, direct binding to monoaminergic receptors has been proposed to contribute to both their clinical effectiveness and their side effects, or lack thereof. Among the target receptors of antidepressants, α1‑adrenergic receptors (ARs) have been implicated in depression etiology, antidepressant action, and side effects. However, differences in the direct effects of antidepressants on signaling from the three subtypes of α1-ARs, namely, α1A-, α1B- and α1D‑ARs, have been little explored. We utilized cell lines overexpressing α1A-, α1B- or α1D-ARs to investigate the effects of the antidepressants imipramine (IMI), desipramine (DMI), mianserin (MIA), reboxetine (REB), citalopram (CIT) and fluoxetine (FLU) on noradrenaline-induced second messenger generation by those receptors. We found similar orders of inhibition at α1A-AR (IMI < DMI < CIT < MIA < REB) and α1D‑AR (IMI = DMI < CIT < MIA), while the α1B-AR subtype was the least engaged subtype and was inhibited with low potency by three drugs (MIA < IMI = DMI). In contrast to their direct antagonistic effects, prolonged incubation with IMI and DMI increased the maximal response of the α1B-AR subtype, and the CIT of both the α1A- and the α1B-ARs. Our data demonstrate a complex, subtype-specific modulation of α1-ARs by antidepressants of different groups.
Collapse
Affiliation(s)
- Piotr Chmielarz
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
| | - Justyna Kuśmierczyk
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
| | - Katarzyna Rafa-Zabłocka
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
| | - Katarzyna Chorązka
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
| | - Marta Kowalska
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
| | - Grzegorz Satała
- Department of Medicinal Chemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland;
| | - Irena Nalepa
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland; (P.C.); (J.K.); (K.R.-Z.); (K.C.); (M.K.)
- Correspondence: ; Tel.: +48-12-6623225
| |
Collapse
|
4
|
de-Los-Santos-Cocotle G, Martínez-Morales JC, Romero-Ávila MT, Reyes-Cruz G, García-Sáinz JA. Effects of agonists and phorbol esters on α 1A-adrenergic receptor-Rab protein interactions. Eur J Pharmacol 2020; 885:173423. [PMID: 32750368 DOI: 10.1016/j.ejphar.2020.173423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 07/21/2020] [Accepted: 07/25/2020] [Indexed: 11/29/2022]
Abstract
In a cell line, stably expressing α1A-adrenoceptors fused to the mCherry red fluorescent protein, noradrenaline, methoxamine, and oxymetazoline induced concentration-dependent increases in intracellular calcium. All of these agents increase α1A-adrenoceptor phosphorylation and internalization. Transient co-expression of these receptors with Rab proteins tagged with the enhanced Green Fluorescent Protein was employed to estimate α1A-adrenoceptor-Rab interaction using Förster Resonance Energy Transfer. Noradrenaline and methoxamine increased α1A-adrenoceptor interaction with Rab5 and Rab7 but did not modify it with Rab9. Oxymetazoline induced adrenoceptor interaction with Rab5 and Rab9 and only an insignificant increase in Rab7 signal. Phorbol myristate acetate increased α1A-adrenoceptor interaction with Rab5 and Rab9 but did not modify it with Rab7. The agonists and the active phorbol ester, all of which induce receptor phosphorylation and internalization, favor receptor interaction with Rab5, i.e., association with early endosomes. Cell stimulation with phorbol myristate acetate induced the α1A-adrenoceptors to interact with the late endosomal marker, Rab9, suggesting that the receptors are directed to slow recycling endosomes once they have transited to the Trans-Golgi network to be retrieved to the plasma membrane. The agonists noradrenaline and methoxamine likely induce a faster recycling and might direct some of the adrenoceptors toward degradation and/or very slow recycling to the plasma membrane. Oxymetazoline produced a mixed pattern of interaction with the Rab proteins. These data indicate that α1A-adrenoceptor agonists can trigger different vesicular traffic and receptor fates within the cells.
Collapse
Affiliation(s)
- Gustavo de-Los-Santos-Cocotle
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Juan Carlos Martínez-Morales
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - M Teresa Romero-Ávila
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Guadalupe Reyes-Cruz
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional-CINVESTAV, Av. Instituto Politécnico Nacional 2508; Col, San Pedro Zacatenco, Mexico City, Mexico
| | - J Adolfo García-Sáinz
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
| |
Collapse
|
5
|
Michel MC, Michel-Reher MB, Hein P. A Systematic Review of Inverse Agonism at Adrenoceptor Subtypes. Cells 2020; 9:E1923. [PMID: 32825009 PMCID: PMC7564766 DOI: 10.3390/cells9091923] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/16/2020] [Accepted: 08/18/2020] [Indexed: 12/18/2022] Open
Abstract
As many, if not most, ligands at G protein-coupled receptor antagonists are inverse agonists, we systematically reviewed inverse agonism at the nine adrenoceptor subtypes. Except for β3-adrenoceptors, inverse agonism has been reported for each of the adrenoceptor subtypes, most often for β2-adrenoceptors, including endogenously expressed receptors in human tissues. As with other receptors, the detection and degree of inverse agonism depend on the cells and tissues under investigation, i.e., they are greatest when the model has a high intrinsic tone/constitutive activity for the response being studied. Accordingly, they may differ between parts of a tissue, for instance, atria vs. ventricles of the heart, and within a cell type, between cellular responses. The basal tone of endogenously expressed receptors is often low, leading to less consistent detection and a lesser extent of observed inverse agonism. Extent inverse agonism depends on specific molecular properties of a compound, but inverse agonism appears to be more common in certain chemical classes. While inverse agonism is a fascinating facet in attempts to mechanistically understand observed drug effects, we are skeptical whether an a priori definition of the extent of inverse agonism in the target product profile of a developmental candidate is a meaningful option in drug discovery and development.
Collapse
Affiliation(s)
- Martin C. Michel
- Department of Pharmacology, Johannes Gutenberg University, 55131 Mainz, Germany;
| | | | | |
Collapse
|
6
|
Alfonzo-Méndez MA, Alcántara-Hernández R, García-Sáinz JA. Novel Structural Approaches to Study GPCR Regulation. Int J Mol Sci 2016; 18:E27. [PMID: 28025563 PMCID: PMC5297662 DOI: 10.3390/ijms18010027] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/15/2016] [Accepted: 12/21/2016] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Upon natural agonist or pharmacological stimulation, G protein-coupled receptors (GPCRs) are subjected to posttranslational modifications, such as phosphorylation and ubiquitination. These posttranslational modifications allow protein-protein interactions that turn off and/or switch receptor signaling as well as trigger receptor internalization, recycling or degradation, among other responses. Characterization of these processes is essential to unravel the function and regulation of GPCR. METHODS In silico analysis and methods such as mass spectrometry have emerged as novel powerful tools. Both approaches have allowed proteomic studies to detect not only GPCR posttranslational modifications and receptor association with other signaling macromolecules but also to assess receptor conformational dynamics after ligand (agonist/antagonist) association. RESULTS this review aims to provide insights into some of these methodologies and to highlight how their use is enhancing our comprehension of GPCR function. We present an overview using data from different laboratories (including our own), particularly focusing on free fatty acid receptor 4 (FFA4) (previously known as GPR120) and α1A- and α1D-adrenergic receptors. From our perspective, these studies contribute to the understanding of GPCR regulation and will help to design better therapeutic agents.
Collapse
Affiliation(s)
- Marco A Alfonzo-Méndez
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México 04510, Mexico.
| | - Rocío Alcántara-Hernández
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México 04510, Mexico.
| | - J Adolfo García-Sáinz
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México 04510, Mexico.
| |
Collapse
|
7
|
Beaudoin S, Rondeau A, Martel O, Bonin MA, van Lier JE, Leyton JV. ChAcNLS, a Novel Modification to Antibody-Conjugates Permitting Target Cell-Specific Endosomal Escape, Localization to the Nucleus, and Enhanced Total Intracellular Accumulation. Mol Pharm 2016; 13:1915-26. [PMID: 27112376 DOI: 10.1021/acs.molpharmaceut.6b00075] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The design of antibody-conjugates (ACs) for delivering molecules for targeted applications in humans has sufficiently progressed to demonstrate clinical efficacy in certain malignancies and reduced systemic toxicity that occurs with standard nontargeted therapies. One area that can advance clinical success for ACs will be to increase their intracellular accumulation. However, entrapment and degradation in the endosomal-lysosomal pathway, on which ACs are reliant for the depositing of their molecular payload inside target cells, leads to reduced intracellular accumulation. Innovative approaches that can manipulate this pathway may provide a strategy for increasing accumulation. We hypothesized that escape from entrapment inside the endosomal-lysosomal pathway and redirected trafficking to the nucleus could be an effective approach to increase intracellular AC accumulation in target cells. Cholic acid (ChAc) was coupled to the peptide CGYGPKKKRKVGG containing the nuclear localization sequence (NLS) from SV-40 large T-antigen, which is termed ChAcNLS. ChAcNLS was conjugated to the mAb 7G3 (7G3-ChAcNLS), which has nanomolar affinity for the cell-surface leukemic antigen interleukin-3 receptor-α (IL-3Rα). Our aim was to determine whether 7G3-ChAcNLS increased intracellular accumulation while retaining nanomolar affinity and IL-3Rα-positive cell selectivity. Competition ELISA and cell treatment assays were performed. Cell fractionation, confocal microscopy, flow cytometry, and Western blot techniques were used to determine the level of antibody accumulation inside cells and in corresponding nuclei. In addition, the radioisotope copper-64 ((64)Cu) was also utilized as a surrogate molecular cargo to evaluate nuclear and intracellular accumulation by radioactivity counting. 7G3-ChAcNLS effectively escaped endosome entrapment and degradation resulting in a unique intracellular distribution pattern. mAb modification with ChAcNLS maintained 7G3 nM affinity and produced high selectivity for IL-3Rα-positive cells. In contrast, 7G3 ACs with the ability to either escape endosome entrapment or traffic to the nucleus was not superior to 7G3-ChAcNLS for increasing intracellular accumulation. Transportation of (64)Cu when complexed to 7G3-ChAcNLS also resulted in increased nuclear and intracellular radioactivity accumulation. Thus, ChAcNLS is a novel mAb functionalizing technology that demonstrates its ability to increase AC intracellular accumulation in target cells through escaping endosome entrapment coupled to nuclear trafficking.
Collapse
Affiliation(s)
- Simon Beaudoin
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| | - Andreanne Rondeau
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| | - Olivier Martel
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| | - Marc-Andre Bonin
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| | - Johan E van Lier
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| | - Jeffrey V Leyton
- Departément de médecine nucléaire et radiobiologie, ‡Plateforme de synthèse de peptides et de sondes d'imageries, Faculté de médecine et sciences de la santé, and §Centre d'imagerie moléculaire de Sherbrooke (CIMS), Université de Sherbrooke , 3001 12e Avenue Nord, Sherbrooke, Québec J1H5N4, Canada
| |
Collapse
|
8
|
Novel effects of FTY720 on perinuclear reorganization of keratin network induced by sphingosylphosphorylcholine: Involvement of protein phosphatase 2A and G-protein-coupled receptor-12. Eur J Pharmacol 2016; 775:86-95. [PMID: 26872988 DOI: 10.1016/j.ejphar.2016.02.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Revised: 01/31/2016] [Accepted: 02/08/2016] [Indexed: 01/09/2023]
Abstract
Sphingosylphosphorylcholine (SPC) evokes perinuclear reorganization of keratin 8 (K8) filaments and regulates the viscoelasticity of metastatic cancer cells leading to enhanced migration. Few studies have addressed the compounds modulating the viscoelasticity of metastatic cancer cells. We studied the effects of sphingosine (SPH), sphingosine 1-phosphate (S1P), FTY720 and FTY720-phosphate (FTY720P) on SPC-induced K8 phosphorylation and reorganization using Western blot and confocal microscopy, and also evaluated the elasticity of PANC-1 cells by atomic force microscopy. FTY720, FTY720P, SPH, and S1P concentration-dependently inhibited SPC-evoked phosphorylation and reorganization of K8, and migration of PANC-1 cells. SPC triggered reduction and narrow distribution of elastic constant K and conversely, FTY720 blocked them. A common upstream regulator of JNK and ERK, protein phosphatase 2A (PP2A) expression was reduced by SPC, but was restored by FTY720 and FTY72P. Butyryl forskolin, a PP2A activator, suppressed SPC-induced K8 phosphorylation and okadaic acid, a PP2A inhibitor, induced K8 phosphorylation. Gene silencing of PP2A also led to K8 phosphorylation, reorganization and migration. We also investigated the involvement of GPR12, a high-affinity SPC receptor, in SPC-evoked keratin phosphorylation and reorganization. GPR12 siRNA suppressed the SPC-triggered phosphorylation and reorganization of K8. GPR12 overexpression stimulated keratin phosphorylation and reorganization even without SPC. FTY720 and FTY720P suppressed the GPR12-induced phosphorylation and reorganization of K8. The collective data indicates that FTY720 and FTY720P suppress SPC-induced phosphorylation and reorganization of K8 in PANC-1 cells by restoring the expression of PP2A via GPR12. These findings might be helpful in the development of compounds that modulate the viscoelasticity of metastatic cancer cells and various SPC actions.
Collapse
|
9
|
McGrath JC. Localization of α-adrenoceptors: JR Vane Medal Lecture. Br J Pharmacol 2015; 172:1179-94. [PMID: 25377869 PMCID: PMC4337695 DOI: 10.1111/bph.13008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 10/06/2014] [Accepted: 10/27/2014] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED This review is based on the JR Vane Medal Lecture presented at the BPS Winter Meeting in December 2011 by J.C. McGrath. A recording of the lecture is included as supporting information. It covers his laboratory's work from 1990 to 2010 on the localization of vascular α1 -adrenoceptors in native tissues, mainly arteries. MAIN POINTS (i) α1 -adrenoceptors are present on several cell types in arteries, not only on medial smooth muscle, but also on adventitial, endothelial and nerve cells; (ii) all three receptor subtypes (α1 A , α1 B , α1 D ) are capable of binding ligands at the cell surface, strongly indicating that they are capable of function and not merely expressed. (iii) all of these cell types can take up an antagonist ligand into the intracellular compartments to which endocytosing receptors move; (iv) each individual subtype can exist at the cell surface and intracellularly in the absence of the other subtypes. As functional pharmacological experiments show variations in the involvement of the different subtypes in contractions of different arteries, it is concluded that the presence and disposition of α1 -adrenoceptors in arteries is not a simple guide to their involvement in function. Similar locations of the subtypes, even in different cell types, suggest that differences between the distribution of subtypes in model systems do not directly correlate with those in native tissues. This review includes a historical summary of the alternative terms used for adrenoceptors (adrenergic receptors, adrenoreceptors) and the author's views on the use of colours to illustrate different items, given his partial colour-blindness.
Collapse
Affiliation(s)
- John C McGrath
- School of Life Sciences, University of GlasgowGlasgow, UK
| |
Collapse
|
10
|
Copik AJ, Baldys A, Nguyen K, Sahdeo S, Ho H, Kosaka A, Dietrich PJ, Fitch B, Raymond JR, Ford APDW, Button D, Milla ME. Isoproterenol acts as a biased agonist of the alpha-1A-adrenoceptor that selectively activates the MAPK/ERK pathway. PLoS One 2015; 10:e0115701. [PMID: 25606852 PMCID: PMC4301629 DOI: 10.1371/journal.pone.0115701] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 11/26/2014] [Indexed: 11/24/2022] Open
Abstract
The α1A-AR is thought to couple predominantly to the Gαq/PLC pathway and lead to phosphoinositide hydrolysis and calcium mobilization, although certain agonists acting at this receptor have been reported to trigger activation of arachidonic acid formation and MAPK pathways. For several G protein-coupled receptors (GPCRs) agonists can manifest a bias for activation of particular effector signaling output, i.e. not all agonists of a given GPCR generate responses through utilization of the same signaling cascade(s). Previous work with Gαq coupling-defective variants of α1A-AR, as well as a combination of Ca2+ channel blockers, uncovered cross-talk between α1A-AR and β2-AR that leads to potentiation of a Gαq-independent signaling cascade in response to α1A-AR activation. We hypothesized that molecules exist that act as biased agonists to selectively activate this pathway. In this report, isoproterenol (Iso), typically viewed as β-AR-selective agonist, was examined with respect to activation of α1A-AR. α1A-AR selective antagonists were used to specifically block Iso evoked signaling in different cellular backgrounds and confirm its action at α1A-AR. Iso induced signaling at α1A-AR was further interrogated by probing steps along the Gαq /PLC, Gαs and MAPK/ERK pathways. In HEK-293/EBNA cells transiently transduced with α1A-AR, and CHO_α1A-AR stable cells, Iso evoked low potency ERK activity as well as Ca2+ mobilization that could be blocked by α1A-AR selective antagonists. The kinetics of Iso induced Ca2+ transients differed from typical Gαq- mediated Ca2+ mobilization, lacking both the fast IP3R mediated response and the sustained phase of Ca2+ re-entry. Moreover, no inositol phosphate (IP) accumulation could be detected in either cell line after stimulation with Iso, but activation was accompanied by receptor internalization. Data are presented that indicate that Iso represents a novel type of α1A-AR partial agonist with signaling bias toward MAPK/ERK signaling cascade that is likely independent of coupling to Gαq.
Collapse
Affiliation(s)
- Alicja. J. Copik
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Aleksander Baldys
- Nephrology Division, Department of Medicine, Medical University of South Carolina, and Medical and Research Services, Ralph H Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, United States of America
| | - Khanh Nguyen
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Sunil Sahdeo
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Hoangdung Ho
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Alan Kosaka
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Paul J. Dietrich
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Bill Fitch
- Discovery Technologies, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - John R. Raymond
- Nephrology Division, Department of Medicine, Medical University of South Carolina, and Medical and Research Services, Ralph H Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425, United States of America
| | - Anthony P. D. W. Ford
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Donald Button
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
| | - Marcos E. Milla
- Biochemical Pharmacology, Inflammation Discovery, Roche Palo Alto LLC, 3401 Hillview Drive, Palo Alto, CA 94304, United States of America
- * E-mail:
| |
Collapse
|
11
|
Qian J, Wu C, Chen X, Li X, Ying G, Jin L, Ma Q, Li G, Shi Y, Zhang G, Zhou N. Differential requirements of arrestin-3 and clathrin for ligand-dependent and -independent internalization of human G protein-coupled receptor 40. Cell Signal 2014; 26:2412-23. [DOI: 10.1016/j.cellsig.2014.07.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 06/06/2014] [Accepted: 07/10/2014] [Indexed: 10/25/2022]
|
12
|
Arg347Cys polymorphism of α1a-adrenergic receptor in vasovagal syncope. Case–control study in a Mexican population. Auton Neurosci 2014; 183:66-71. [DOI: 10.1016/j.autneu.2014.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 12/26/2013] [Accepted: 01/13/2014] [Indexed: 01/10/2023]
|
13
|
Osorio-Espinoza A, Escamilla-Sánchez J, Aquino-Jarquin G, Arias-Montaño JA. Homologous desensitization of human histamine H₃ receptors expressed in CHO-K1 cells. Neuropharmacology 2013; 77:387-97. [PMID: 24161268 DOI: 10.1016/j.neuropharm.2013.09.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 11/18/2022]
Abstract
Histamine H₃ receptors (H₃Rs) modulate the function of the nervous system at the pre- and post-synaptic levels. In this work we aimed to determine whether, as other G protein-coupled receptors (GPCRs), H₃Rs desensitize in response to agonist exposure. By using CHO-K1 cells stably transfected with the human H₃R (hH3R) we show that functional responses (inhibition of forskolin-induced cAMP accumulation in intact cells and stimulation of [(35)S]-GTPγS binding to cell membranes) were markedly reduced after agonist exposure. For cAMP accumulation assays the effect was significant at 60 min with a maximum at 90 min. Agonist exposure resulted in decreased binding sites for the radioligand [(3)H]-N-methyl-histamine ([(3)H]-NMHA) to intact cells and modified the sub-cellular distribution of H₃Rs, as detected by sucrose density gradients and [(3)H]-NMHA binding to cell membranes, suggesting receptor internalization. The reduction in the inhibition of forskolin-stimulated cAMP formation observed after agonist pre-incubation was prevented by incubation in hypertonic medium or in ice-cold medium. Agonist-induced loss in binding sites was also prevented by hypertonic medium or incubation at 4 °C, but not by filipin III, indicating clathrin-dependent endocytosis. Immunodetection showed that CHO-K1 cells express GPCR kinases (GRKs) 2/3, and both the GRK general inhibitor ZnCl₂ and a small interfering RNA against GRK-2 reduced receptor desensitization. Taken together these results indicate that hH₃Rs experience homologous desensitization upon prolonged exposure to agonists, and that this process involves the action of GRK-2 and internalization via clathrin-coated vesicles.
Collapse
Affiliation(s)
- Angélica Osorio-Espinoza
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico
| | - Juan Escamilla-Sánchez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico
| | - Guillermo Aquino-Jarquin
- Unidad de Investigación en Enfermedades Oncológicas, Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, 06720 México, D.F., Mexico
| | - José-Antonio Arias-Montaño
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico.
| |
Collapse
|
14
|
Lei B, Schwinn DA, Morris DP. Stimulation of α1a adrenergic receptors induces cellular proliferation or antiproliferative hypertrophy dependent solely on agonist concentration. PLoS One 2013; 8:e72430. [PMID: 23991110 PMCID: PMC3749976 DOI: 10.1371/journal.pone.0072430] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 07/08/2013] [Indexed: 12/05/2022] Open
Abstract
Stimulation of α1aAdrenergic Receptors (ARs) is known to have anti-proliferative and hypertrophic effects; however, some studies also suggests this receptor can increase cell proliferation. Surprisingly, we find the α1aAR expressed in rat-1 fibroblasts can produce either phenotype, depending exclusively on agonist concentration. Stimulation of the α1aAR by high dose phenylephrine (>10−7 M) induces an antiproliferative, hypertrophic response accompanied by robust and extended p38 activation. Inhibition of p38 with SB203580 prevented the antiproliferative response, while inhibition of Erk or Jnk had no effect. In stark contrast, stimulation of the α1aAR with low dose phenylephrine (∼10−8 M) induced an Erk-dependent increase in cellular proliferation. Agonist-induced Erk phosphorylation was preceded by rapid FGFR and EGFR transactivation; however, only EGFR inhibition blocked Erk activation and proliferation. The general matrix metalloprotease inhibitor, GM6001, blocked agonist induced Erk activation within seconds, strongly suggesting EGFR activation involved extracellular triple membrane pass signaling. Erk activation required little Ca2+ release and was blocked by PLCβ or PKC inhibition but not by intracellular Ca2+ chelation, suggesting Ca2+ independent activation of novel PKC isoforms. In contrast, Ca2+ release was essential for PI3K/Akt activation, which was acutely maximal at non-proliferative doses of agonist. Remarkably, our data suggests EGFR transactivation leading to Erk induced proliferation has the lowest activation threshold of any α1aAR response. The ability of α1aARs to induce proliferation are discussed in light of evidence suggesting antagonistic growth responses reflect native α1aAR function.
Collapse
Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Debra A. Schwinn
- Departments of Anesthesiology, Pharmacology, Biochemistry, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Daniel P. Morris
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, Washington, United States of America
- * E-mail:
| |
Collapse
|
15
|
Perez-Aso M, Segura V, Montó F, Barettino D, Noguera MA, Milligan G, D'Ocon P. The three α1-adrenoceptor subtypes show different spatio-temporal mechanisms of internalization and ERK1/2 phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2322-33. [PMID: 23797059 DOI: 10.1016/j.bbamcr.2013.06.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 06/12/2013] [Accepted: 06/13/2013] [Indexed: 12/21/2022]
Abstract
We analyzed the kinetic and spatial patterns characterizing activation of the MAP kinases ERK 1 and 2 (ERK1/2) by the three α1-adrenoceptor (α1-AR) subtypes in HEK293 cells and the contribution of two different pathways to ERK1/2 phosphorylation: protein kinase C (PKC)-dependent ERK1/2 activation and internalization-dependent ERK1/2 activation. The different pathways of phenylephrine induced ERK phosphorylation were determined by western blot, using the PKC inhibitor Ro 31-8425, the receptor internalization inhibitor concanavalin A and the siRNA targeting β-arrestin 2. Receptor internalization properties were studied using CypHer5 technology and VSV-G epitope-tagged receptors. Activation of α1A- and α1B-ARs by phenylephrine elicited rapid ERK1/2 phosphorylation that was directed to the nucleus and inhibited by Ro 31-8425. Concomitant with phenylephrine induced receptor internalization α1A-AR, but not α1B-AR, produced a maintained and PKC-independent ERK phosphorylation, which was restricted to the cytosol and inhibited by β-arrestin 2 knockdown or concanavalin A treatment. α1D-AR displayed constitutive ERK phosphorylation, which was reduced by incubation with prazosin or the selective α1D antagonist BMY7378. Following activation by phenylephrine, α1D-AR elicited rapid, transient ERK1/2 phosphorylation that was restricted to the cytosol and not inhibited by Ro 31-8425. Internalization of the α1D-AR subtype was not observed via CypHer5 technology. The three α1-AR subtypes present different spatio-temporal patterns of receptor internalization, and only α1A-AR stimulation translates to a late, sustained ERK1/2 phosphorylation that is restricted to the cytosol and dependent on β-arrestin 2 mediated internalization.
Collapse
Affiliation(s)
- M Perez-Aso
- Departament de Farmacologia, Universitat de València, Spain
| | | | | | | | | | | | | |
Collapse
|
16
|
Segura V, Pérez-Aso M, Montó F, Carceller E, Noguera MA, Pediani J, Milligan G, McGrath IC, D’Ocon P. Differences in the signaling pathways of α(1A)- and α(1B)-adrenoceptors are related to different endosomal targeting. PLoS One 2013; 8:e64996. [PMID: 23717684 PMCID: PMC3663791 DOI: 10.1371/journal.pone.0064996] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 04/20/2013] [Indexed: 01/14/2023] Open
Abstract
AIMS To compare the constitutive and agonist-dependent endosomal trafficking of α(1A)- and α(1B)-adrenoceptors (ARs) and to establish if the internalization pattern determines the signaling pathways of each subtype. METHODS Using CypHer5 technology and VSV-G epitope tagged α(1A)- and α(1B)-ARs stably and transiently expressed in HEK 293 cells, we analyzed by confocal microscopy the constitutive and agonist-induced internalization of each subtype, and the temporal relationship between agonist induced internalization and the increase in intracellular calcium (determined by FLUO-3 flouorescence), or the phosphorylation of ERK1/2 and p38 MAP kinases (determined by Western blot). RESULTS AND CONCLUSIONS Constitutive as well as agonist-induced trafficking of α(1A) and α(1B) ARs maintain two different endosomal pools of receptors: one located close to the plasma membrane and the other deeper into the cytosol. Each subtype exhibited specific characteristics of internalization and distribution between these pools that determines their signaling pathways: α(1A)-ARs, when located in the plasma membrane, signal through calcium and ERK1/2 pathways but, when translocated to deeper endosomes, through a mechanism sensitive to β-arrestin and concanavalin A, continue signaling through ERK1/2 and also activate the p38 pathway. α(1B)-ARs signal through calcium and ERK1/2 only when located in the membrane and the signals disappear after endocytosis and by disruption of the membrane lipid rafts by methyl-β-cyclodextrin.
Collapse
Affiliation(s)
- Vanessa Segura
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Miguel Pérez-Aso
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Fermí Montó
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Elena Carceller
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - María Antonia Noguera
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - John Pediani
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences. University of Glasgow, Glasgow, United Kingdom
- Autonomic Physiology Unit, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Graeme Milligan
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences. University of Glasgow, Glasgow, United Kingdom
| | - Ian Christie McGrath
- Autonomic Physiology Unit, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Pilar D’Ocon
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| |
Collapse
|
17
|
Simon AC, Loverdo C, Gaffuri AL, Urbanski M, Ladarre D, Carrel D, Rivals I, Leterrier C, Benichou O, Dournaud P, Szabo B, Voituriez R, Lenkei Z. Activation-dependent plasticity of polarized GPCR distribution on the neuronal surface. J Mol Cell Biol 2013; 5:250-65. [PMID: 23585691 DOI: 10.1093/jmcb/mjt014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Directionality of information flow through neuronal networks is sustained at cellular level by polarized neurons. However, specific targeting or anchoring motifs responsible for polarized distribution on the neuronal surface have only been identified for a few neuronal G-protein-coupled receptors (GPCRs). Here, through mutational and pharmacological modifications of the conformational state of two model GPCRs, the axonal CB1R cannabinoid and the somatodendritic SSTR2 somatostatin receptors, we show important conformation-dependent variations in polarized distribution. The underlying mechanisms include lower efficiency of conformation-dependent GPCR endocytosis in axons, compared with dendrites, particularly at moderate activation levels, as well as endocytosis-dependent transcytotic delivery of GPCRs from the somatodendritic domain to distal axonal portions, shown by using compartmentalized microfluidic devices. Kinetic modeling predicted that GPCR distribution polarity is highly regulated by steady-state endocytosis, which is conformation dependent and is able to regulate the relative amount of GPCRs targeted to axons and that axonally polarized distribution is an intermediary phenotype that appears at moderate basal activation levels. Indeed, we experimentally show that gradual changes in basal activation-dependent endocytosis lead to highly correlated shifts of polarized GPCR distribution on the neuronal surface, which can even result in a fully reversed polarized distribution of naturally somatodendritic or axonal GPCRs. In conclusion, polarized distribution of neuronal GPCRs may have a pharmacologically controllable component, which, in the absence of dominant targeting motifs, could even represent the principal regulator of sub-neuronal distribution. Consequently, chronic modifications of basal GPCR activation by therapeutic or abused drugs may lead to previously unanticipated changes in brain function through perturbation of polarized GPCR distribution on the neuronal surface.
Collapse
Affiliation(s)
- Anne C Simon
- Laboratoire de Neurobiologie, CNRS UMR7637, ESPCI-ParisTech, 10 Rue Vauquelin, Paris 75005, France
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Akinaga J, Lima V, Kiguti LRDA, Hebeler-Barbosa F, Alcántara-Hernández R, García-Sáinz JA, Pupo AS. Differential phosphorylation, desensitization, and internalization of α1A-adrenoceptors activated by norepinephrine and oxymetazoline. Mol Pharmacol 2013; 83:870-81. [PMID: 23364786 DOI: 10.1124/mol.112.082313] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Loss of response on repetitive drug exposure (i.e., tachyphylaxis) is a particular problem for the vasoconstrictor effects of medications containing oxymetazoline (OXY), an α1-adrenoceptor (AR) agonist of the imidazoline class. One cause of tachyphylaxis is receptor desensitization, usually accompanied by phosphorylation and internalization. It is well established that α1A-ARs are less phosphorylated, desensitized, and internalized on exposure to the phenethylamines norepinephrine (NE), epinephrine, or phenylephrine (PE) than are the α1B and α1D subtypes. However, here we show in human embryonic kidney-293 cells that the low-efficacy agonist OXY induces G protein-coupled receptor kinase 2-dependent α1A-AR phosphorylation, followed by rapid desensitization and internalization (∼40% internalization after 5 minutes of stimulation), whereas phosphorylation of α1A-ARs exposed to NE depends to a large extent on protein kinase C activity and is not followed by desensitization, and the receptors undergo delayed internalization (∼35% after 60 minutes of stimulation). Native α1A-ARs from rat tail artery and vas deferens are also desensitized by OXY, but not by NE or PE, indicating that this property of OXY is not limited to recombinant receptors expressed in cell systems. The results of the present study are clearly indicative of agonist-directed α1A-AR regulation. OXY shows functional selectivity relative to NE and PE at α1A-ARs, leading to significant receptor desensitization and internalization, which is important in view of the therapeutic vasoconstrictor effects of this drug and the varied biologic process regulated by α1A-ARs.
Collapse
Affiliation(s)
- Juliana Akinaga
- Department of Pharmacology, Instituto de Biociências, Universidade Estadual Paulista (UNESP), Botucatu, São Paulo, Brazil
| | | | | | | | | | | | | |
Collapse
|
19
|
Ford NR, Miller HE, Reeme AE, Waukau J, Bengtson C, Routes JM, Robinson RT. Inflammatory signals direct expression of human IL12RB1 into multiple distinct isoforms. THE JOURNAL OF IMMUNOLOGY 2012; 189:4684-94. [PMID: 23024274 DOI: 10.4049/jimmunol.1200606] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IL12RB1 is essential for human resistance to multiple intracellular pathogens, including Mycobacterium tuberculosis. In its absence, the proinflammatory effects of the extracellular cytokines IL-12 and IL-23 fail to occur, and intracellular bacterial growth goes unchecked. Given the recent observation that mouse leukocytes express more than one isoform from il12rb1, we examined whether primary human leukocytes similarly express more than one isoform from IL12RB1. We observed that human leukocytes express as many as 13 distinct isoforms, the relative levels of each being driven by inflammatory stimuli both in vitro and in vivo. Surprisingly, the most abundant isoform present before stimulation is a heretofore uncharacterized intracellular form of the IL-12R (termed "isoform 2") that presumably has limited contact with extracellular cytokine. After stimulation, primary PBMCs, including the CD4(+), CD8(+), and CD56(+) lineages contained therein, alter the splicing of IL12RB1 RNA to increase the relative abundance of isoform 1, which confers IL-12/IL-23 responsiveness. These data demonstrate both a posttranscriptional mechanism by which cells regulate their IL-12/IL-23 responsiveness, and that leukocytes primarily express IL12RB1 in an intracellular form located away from extracellular cytokine.
Collapse
Affiliation(s)
- Nicole R Ford
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Gaffuri AL, Ladarre D, Lenkei Z. Type-1 cannabinoid receptor signaling in neuronal development. Pharmacology 2012; 90:19-39. [PMID: 22776780 DOI: 10.1159/000339075] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 04/13/2012] [Indexed: 01/21/2023]
Abstract
The type-1 cannabinoid receptor (CB1R) was initially identified as the neuronal target of Δ(9)-tetrahydrocannabinol (THC), the major psychoactive substance of marijuana. This receptor is one of the most abundant G-protein-coupled receptors in the adult brain, the target of endocannabinoid ligands and a well-characterized retrograde synaptic regulator. However, CB1Rs are also highly and often transiently expressed in neuronal populations in the embryonic and early postnatal brain, even before the formation of synapses. This suggests important physiological roles for CB1Rs during neuronal development. Several recent reviews have summarized our knowledge about the role of the endocannabinoid (eCB) system in neurodevelopment and neurotransmission by focusing on the metabolism of endocannabinoid molecules. Here, we review current knowledge about the effects of the modulation of CB1R signaling during the different phases of brain development. More precisely, we focus on reports that directly implicate CB1Rs during progenitor cell migration and differentiation, neurite outgrowth, axonal pathfinding and synaptogenesis. Based on theoretical considerations and on the reviewed experimental data, we propose a new model to explain the diversity of experimental findings on eCB signaling on neurite growth and axonal pathfinding. In our model, cell-autonomus and paracrine eCBs acting on CB1Rs are part of a global inhibitory network of cytoskeletal effectors, which act in concert with positive-feedback local-excitation loops, to ultimately yield highly polarized neurons.
Collapse
Affiliation(s)
- Anne-Lise Gaffuri
- Neurobiology Laboratory, ESPCI-ParisTech, ESPCI-CNRS UMR 7637, Paris, France
| | | | | |
Collapse
|
21
|
Constitutive coupling of a naturally occurring human alpha1a-adrenergic receptor genetic variant to EGFR transactivation pathway. Proc Natl Acad Sci U S A 2011; 108:19796-801. [PMID: 22089237 DOI: 10.1073/pnas.1116271108] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We previously identified a naturally occurring human SNP, G247R, in the third intracellular loop of the α(1a)-adrenergic receptor (α(1a)-247R) and demonstrated that constitutive expression of α(1a)-247R results in twofold increased cell proliferation compared with WT. In the present study we elucidate molecular mechanisms and signal transduction pathways responsible for increased cell proliferation unique to α(1a)-247R, but not α(1a)-WT, α(1b), or α(1d)AR subtypes. We show that elevated levels of matrix metalloproteinase-7 (MMP7) and a disintegrin and metalloproteinase-12 (ADAM12) in α(1a)-247R-expressing cells are responsible for EGF receptor (EGFR) transactivation, downstream ERK activation, and increased cell proliferation; this pathway is confirmed using MMP, EGFR, and ERK inhibitors. We demonstrate that EGFR transactivation and downstream ERK activation depends on increased shedding of heparin-binding EGF. Finally, we demonstrate that knockdown of MMP7 or β-arrestin1 by shRNAs results in attenuation of proliferation of cells expressing α(1a)-247R. Importantly, accelerated cell proliferation triggered by the α(1a)-247R is serum- and agonist-independent, providing unique evidence for constitutive active coupling to the β-arrestin1/MMP/EGFR transactivation pathway by any G protein-coupled receptor. These findings raise the possibility of a previously unexplored mechanism for sympathetically mediated human hypertension triggered by a naturally occurring human genetic variant.
Collapse
|
22
|
Segura V, Flacco N, Oliver E, Barettino D, D'Ocon P, Ivorra MD. Alpha1-adrenoceptors in the rat cerebral cortex: new insights into the characterization of alpha1L- and alpha1D-adrenoceptors. Eur J Pharmacol 2010; 641:41-8. [PMID: 20511116 DOI: 10.1016/j.ejphar.2010.05.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 04/14/2010] [Accepted: 05/06/2010] [Indexed: 10/19/2022]
Abstract
Among the three alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) a peculiar intracellular localization and poor coupling to membrane signals of cloned alpha(1D)-adrenoceptor have been reported. In addition, the alpha(1L)-adrenoceptor (low affinity for prazosin), a functional phenotype of alpha(1A), has been described. The purpose of this work was to analyze the expression, cellular localization and coupling to membrane signalling (inositol phosphate accumulation) of alpha(1)-adrenoceptor subtypes in a native tissue, the rat cerebral cortex. mRNA for the three subtypes was quantified by real-time RT-PCR (alpha(1D)>alpha(1B)>>alpha(1A)). alpha(1)-Adrenoceptors were also detected by immunoblotting, revealing alpha(1A)- and alpha(1B)-adrenoceptors to be predominantly expressed in the membrane fraction and the alpha(1D)-adrenoceptor to be localized in the cytosolic fraction. Competitive radioligand binding studies revealed the presence of alpha(1D)-adrenoceptor in tissue homogenates, whereas only alpha(1A)- and alpha(1B)-subtypes were detected in membranes. The proportion of alpha(1A)-adrenoceptor increased after treatment with noradrenaline, suggesting differences in agonist-mediated trafficking. Saturation experiments detected high- and low (alpha(1A/L))-prazosin binding sites, the latter of which disappeared on incubation with GppNHp. The alpha(1A/L)-adrenoceptor was heavily implicated in the inositol phosphate response, while the alpha(1D)-subtype did not play a relevant role. These results suggest that the predominant cytosolic localization of alpha(1D)-adrenoceptor lies behind its poor coupling to membrane signalling such as inositol phosphate pathway. The fact that the alpha(1L)-adrenoceptor detected in radioligand binding studies disappeared in the presence of GppNHp implies that it represents a conformational state of the alpha(1A)-adrenoceptor coupled to G-protein.
Collapse
Affiliation(s)
- Vanessa Segura
- Departamento de Farmacología, Facultat de Farmàcia, Universitat de València, Avda. Vicent Andrés Estelles s/n, Valencia, Spain
| | | | | | | | | | | |
Collapse
|
23
|
Methven L, Simpson PC, McGrath JC. Alpha1A/B-knockout mice explain the native alpha1D-adrenoceptor's role in vasoconstriction and show that its location is independent of the other alpha1-subtypes. Br J Pharmacol 2010; 158:1663-75. [PMID: 19888965 DOI: 10.1111/j.1476-5381.2009.00462.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Theoretically, three alpha(1)-adrenoceptor subtypes can interact at the signalling level to alter vascular contraction or at the molecular level to alter each other's cellular location. The alpha(1A/B)-adrenoceptor knockout mouse (alpha(1A/B)-KO) was used to study the isolated alpha(1D)-adrenoceptor to consider these potential interactions in native tissue. EXPERIMENTAL APPROACH Pharmacological analysis of carotid and mesenteric arteries employed wire myography and fluorescent ligand binding (alpha(1)-adrenoceptor ligand BODIPY FL-prazosin, QAPB). KEY RESULTS alpha(1A/B)-KO carotid had clear alpha(1D)-adrenoceptor-induced contractions. In WT carotid alpha(1D)-adrenoceptor dominated but all three alpha(1)-subtypes participated. alpha(1A/B)-KO mesenteric had alpha(1D)-adrenoceptor responses with high sensitivity and small maximum, explaining how alpha(1D)-adrenoceptor could determine agonist sensitivity in WT. In both arteries alpha(1A/B)-KO fluorescence levels were reduced but pharmacologically more consistent with 'pure'alpha(1D)-adrenoceptors. alpha(1D)-Adrenoceptor binding in alpha(1A/B)-KO was observed on the cell surface and intracellularly and was present in a high proportion of smooth-muscle cells in both strains, regardless of artery type. CONCLUSIONS AND IMPLICATIONS 'Pure'alpha(1D)-adrenoceptor pharmacology in alpha(1A/B)-KO provides a quantitative standard. Functionally, the alpha(1D)- and alpha(1A)-adrenoceptors produce additive responses and do not significantly compensate for each other. alpha(1D)-Adrenoceptor contributes to sensitivity even in resistance arteries. In alpha(1A/B)-KO, the loss of alpha(1A)- and alpha(1B)-adrenoceptors is reflected by a general decrease in fluorescence, but similar binding distribution to WT indicates that the alpha(1D)-adrenoceptor location in native smooth-muscle cells is not influenced by other alpha(1)-adrenoceptors. Equivalent levels of receptors did not correspond to equivalent responses. In conclusion, alpha(1)-subtypes do not interact but provide independent alternative signals for vascular regulation.
Collapse
Affiliation(s)
- L Methven
- Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK.
| | | | | |
Collapse
|
24
|
Methven L, McBride M, Wallace GA, McGrath JC. The alpha 1B/D-adrenoceptor knockout mouse permits isolation of the vascular alpha 1A-adrenoceptor and elucidates its relationship to the other subtypes. Br J Pharmacol 2009; 158:209-24. [PMID: 19572943 PMCID: PMC2795267 DOI: 10.1111/j.1476-5381.2009.00269.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 01/30/2009] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Mesenteric and carotid arteries from the alpha(1B/D)-adrenoceptor knockout (alpha(1B/D)-KO) were employed to isolate alpha(1A)-adrenoceptor pharmacology and location and to reveal these features in the wild-type (WT) mouse. EXPERIMENTAL APPROACH Functional pharmacology by wire myography and receptor localization by confocal microscopy, using the fluorescent alpha(1)-adrenoceptor ligand BODIPY FL-Prazosin (QAPB), on mesenteric (an 'alpha(1A)-adrenoceptor' tissue) and carotid (an 'alpha(1D)-adrenoceptor' tissue) arteries. KEY RESULTS Alpha(1B/D)-KO mesenteric arteries showed straightforward alpha(1A)-adrenoceptor agonist/antagonist pharmacology. WT had complex pharmacology with alpha(1A)- and alpha(1D)-adrenoceptor components. alpha(1B/D)-KO had a larger alpha(1A)-adrenoceptor response suggesting compensatory up-regulation: no increase in fluorescent ligand binding suggests up-regulation of signalling. alpha(1B/D)-KO carotid arteries had low efficacy alpha(1A)-adrenoceptor responses. WT had complex pharmacology consistent with co-activation of all three subtypes. Fluorescent binding had straightforward alpha(1A)-adrenoceptor characteristics in both arteries of alpha(1B/D)-KO. Fluorescent binding varied between cells in relative intracellular and surface distribution. Total fluorescence was reduced in the alpha(1B/D)-KO due to fewer smooth muscle cells showing fluorescent binding. WT binding was greater and sensitive to alpha(1A)- and alpha(1D)-adrenoceptor antagonists. CONCLUSIONS AND IMPLICATIONS The straightforward pharmacology and fluorescent binding in the alpha(1B/D)-KO was used to interpret the properties of the alpha(1A)-adrenoceptor in the WT. Reduced total fluorescence in alpha(1B/D)-KO arteries, despite a clear difference in the functionally dominant subtype, indicates that measurement of receptor protein is unlikely to correlate with function. Fewer cells bound QAPB in the alpha(1B/D)-KO suggesting different cellular phenotypes of alpha(1A)-adrenoceptor exist. The alpha(1B/D)-KO provides robust assays for the alpha(1A)-adrenoceptor and takes us closer to understanding multi-receptor subtype interactions.
Collapse
MESH Headings
- Adrenergic Agonists/pharmacology
- Adrenergic Antagonists/pharmacology
- Adrenergic alpha-1 Receptor Agonists
- Animals
- Carotid Arteries/drug effects
- Carotid Arteries/physiology
- Male
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Protein Subunits/classification
- Protein Subunits/physiology
- Receptors, Adrenergic, alpha-1/classification
- Receptors, Adrenergic, alpha-1/deficiency
- Receptors, Adrenergic, alpha-1/physiology
Collapse
Affiliation(s)
- L Methven
- Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK.
| | | | | | | |
Collapse
|
25
|
Lei B, Morris DP, Smith MP, Schwinn DA. Lipid rafts constrain basal alpha(1A)-adrenergic receptor signaling by maintaining receptor in an inactive conformation. Cell Signal 2009; 21:1532-9. [PMID: 19520158 DOI: 10.1016/j.cellsig.2009.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/20/2009] [Accepted: 06/01/2009] [Indexed: 12/16/2022]
Abstract
We have reported that the alpha(1A)-adrenergic receptor (alpha(1A)AR) in rat-1 fibroblasts is a lipid raft protein. Here we examined whether disrupting lipid rafts by methyl-beta-cyclodextrin (MCD) sequestration of cholesterol affects alpha(1A)AR signaling. Unexpectedly, MCD increased alpha(1A)AR-dependent basal inositol phosphate formation and p38 mitogen-activated protein kinase activation in a cholesterol-dependent manner. It also initiated internalization of surface alpha(1A)AR, which was partially blocked by receptor inhibition. Binding assays revealed MCD-mediated increases in receptor agonist affinity as well as reciprocal decreases in inverse agonist affinity, a behavior that is usually interpreted as a shift toward the active receptor conformation. In untreated cells a fraction of the receptor was found to be present in preassociated receptor/G protein complexes, which rapidly dissociate upon receptor stimulation. Consistent with MCD-induced signaling, raft disruption resulted in an increase in receptor/G protein complexes. These results strongly suggest that lipid rafts constrain basal alpha(1A)AR activity; however, preassembled receptor/G protein complexes could still provide a mechanism for accelerating alpha(1A)AR signaling following stimulation.
Collapse
Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA.
| | | | | | | |
Collapse
|
26
|
Oliver E, Martí D, Montó F, Flacco N, Moreno L, Barettino D, Ivorra MD, D'Ocon P. The impact of alpha1-adrenoceptors up-regulation accompanied by the impairment of beta-adrenergic vasodilatation in hypertension. J Pharmacol Exp Ther 2008; 328:982-90. [PMID: 19060223 DOI: 10.1124/jpet.108.146043] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In human and animal hypertension models, increased activity of G-protein-coupled receptor kinase (GRK) 2 determines a generalized decrease of beta-adrenergic vasodilatation. We analyzed the possibility of differential changes in the expression and functionality of alpha(1A), alpha(1B), alpha(1D), beta(1), beta(2), and beta(3)-ARs also being involved in the process. We combined the quantification of mRNA levels with immunoblotting and functional studies in aortas of young and adult spontaneously hypertensive rats (SHRs) and their controls (Wistar Kyoto). We found the expression and function of beta(1)-adrenoceptors in young prehypertensive SHRs to be higher, whereas a generalized increase in the expression of the six adrenoceptors and GRK2 was observed in aortas of adult hypertensive SHRs. alpha(1D)- and beta(3)-adrenoceptors, the subtypes that are more resistant to GRK2-mediated internalization and mostly expressed in rat aorta, exhibited an increased functional role in hypertensive animals, showing two hemodynamic consequences: 1) an increased sensitivity to the vasoconstrictor stimulus accompanied by a decreased sensitivity to the vasodilator stimulus (alpha(1D)-ARs are the most sensitive to agonists, and beta(3)-ARs are the least sensitive to agonists); and 2) a slower recovery of the basal tone after adrenergic stimulus removal because of the kinetic characteristic of the alpha(1D) subtype. These functional changes might be involved in the greater sympathetic vasoconstrictor tone observed in hypertension.
Collapse
Affiliation(s)
- Eduardo Oliver
- Departamento de Farmacología, Facultat de Farmàcia, Universitat de València, Burjassot 46100, València, Spain
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Thieme K, Eguti DMN, Mello-Aires M, Oliveira-Souza M. The effect of angiotensin II on intracellular pH is mediated by AT1receptor translocation. Am J Physiol Cell Physiol 2008; 295:C138-45. [DOI: 10.1152/ajpcell.00512.2007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of ANG II on intracellular pH (pHi) recovery rate and AT1receptor translocation was investigated in transfected MDCK cells. The pHirecovery rate was evaluated by fluorescence microscopy using the fluorescent probe BCECF-AM. The human angiotensin II receptor isoform 1 (hAT1) translocation was analyzed by immunofluorescence and confocal microscope. Our data show that transfected cells in control situation have a pHirecovery rate of 0.219 ± 0.017 pH U/min ( n = 11). This value was similar to nontransfected cells [0.211 ± 0.009 pH U/min ( n = 12)]. Both values were significantly increased with ANG II (10−9M) but not with ANG II (10−6M). Losartan (10−7M) and dimethyl-BAPTA-AM (10−7M) decreased significantly the stimulatory effect of ANG II (10−9M) and induced an increase in Na+/H+exchanger 1 (NHE-1) activity with ANG II (10−6M). Immunofluorescence studies indicated that in control situation, the hAT1receptor was predominantly expressed in cytosol. However, it was translocated to plasma membrane with ANG II (10−9M) and internalized with ANG II (10−6M). Losartan (10−7M) induced hAT1translocation to plasma membrane in all studied groups. Dimethyl-BAPTA-AM (10−7M) did not change the effect of ANG II (10−9M) on the hAT1receptor distribution but induced its accumulation at plasma membrane in cells treated with ANG II (10−6M). With ionomycin (10−6M), the receptor was accumulated in cytosol. The results indicate that, in MDCK cells, the effect of ANG II on NHE-1 activity is associated with ligand binding to AT1receptor and intracellular signaling events related to AT1translocation.
Collapse
|
28
|
Huang Y, Wright CD, Kobayashi S, Healy CL, Elgethun M, Cypher A, Liang Q, O'Connell TD. GATA4 is a survival factor in adult cardiac myocytes but is not required for alpha1A-adrenergic receptor survival signaling. Am J Physiol Heart Circ Physiol 2008; 295:H699-707. [PMID: 18552157 DOI: 10.1152/ajpheart.01204.2007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recently, we defined an alpha1A-adrenergic receptor-ERK (alpha1A-AR-ERK) survival signaling pathway in adult cardiac myocytes. Previous studies in neonatal cardiac myocytes indicated that the cardiac-specific transcription factor GATA4 is a downstream mediator of alpha1-ERK signaling and that phosphorylation of GATA4 by ERK increases DNA binding and transcriptional activity. Therefore, we examined GATA4 as a potential downstream effector of alpha1A-ERK survival signaling in adult cardiac myocytes. We measured norepinephrine (NE)-induced cell death in cultured cardiac myocytes lacking alpha1-ARs (cultured from alpha1A/B-AR double-knockout mice, alpha1ABKO mice) that are susceptible to cell death induced by several proapoptotic stimuli, including NE. Our results show that overexpression of GATA4 is sufficient to protect alpha1ABKO cardiac myocytes from NE-induced cell death. However, we found that the alpha1A-subtype did not induce phosphorylation or increase the activity of GATA4 in adult mouse cardiac myocytes in culture or in vivo. Furthermore, we examined the effect of siRNA-mediated knockdown of GATA4 on alpha1A-survival signaling. In alpha1B-knockout cardiac myocytes, which express only the alpha1A-subtype and are protected from NE-induced cell death, GATA4 knockdown did not reverse alpha1A-survival signaling in response to NE. In summary, we found that GATA4 acted as a survival factor by preventing cell death in alpha1ABKO cardiac myocytes, but GATA4 was not activated by alpha1-AR stimulation and was not required for alpha1A-survival signaling in adult cardiac myocytes. This also identifies an important mechanistic difference in alpha1-signaling between adult and neonatal cardiac myocytes.
Collapse
Affiliation(s)
- Yuan Huang
- Cardiovascular Research Center, Sanford Research/Univ. of South Dakota, Dept. of Internal Medicine, Univ. of South Dakota, 1100 E. 21st St., Ste. 700, Sioux Falls, SD 57105, USA
| | | | | | | | | | | | | | | |
Collapse
|
29
|
Stanasila L, Abuin L, Dey J, Cotecchia S. Different Internalization Properties of the α1a- and α1b-Adrenergic Receptor Subtypes: The Potential Role of Receptor Interaction with β-Arrestins and AP50. Mol Pharmacol 2008; 74:562-73. [DOI: 10.1124/mol.107.043422] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
30
|
Morris DP, Lei B, Wu YX, Michelotti GA, Schwinn DA. The alpha1a-adrenergic receptor occupies membrane rafts with its G protein effectors but internalizes via clathrin-coated pits. J Biol Chem 2008; 283:2973-85. [PMID: 18048357 PMCID: PMC2566898 DOI: 10.1074/jbc.m705795200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The alpha(1a)-adrenergic receptor (alpha(1a)AR) occupies intracellular and plasma membranes in both native and heterologous expression systems. Based on multiple independent lines of evidence, we demonstrate the alpha(1a)AR at the cell surface occupies membrane rafts but exits from rafts following stimulation. In non-detergent raft preparations, basal alpha(1a)AR is present in low density membrane rafts and colocalizes with its G protein effectors on density gradients. Raft disruption by cholesterol depletion with methyl-beta-cyclodextrin eliminates these light rafts. To confirm the presence of the alpha(1a)AR in plasma membrane rafts, fluorescence resonance energy transfer measurements were used to demonstrate colocalization of surface receptor and the raft marker, cholera toxin B. This colocalization was largely lost following alpha(1a)AR stimulation with phenylephrine. Similarly, receptor stimulation causes exit of the alpha(1a)AR from light rafts within 3-10 min in contrast to the G proteins, which largely remain in light rafts. Importantly, this delayed exit of the alpha(1a)AR suggests acute receptor signaling and desensitization occur entirely within rafts. Interestingly, both confocal analysis and measurement of surface alpha(1a)AR levels indicate modest receptor internalization during the 10 min following stimulation, suggesting most of the receptor has entered non-raft plasma membrane. Nevertheless, activation does increase the rate of receptor internalization as does disruption of rafts with methyl-beta-cyclodextrin, suggesting raft exit enables internalization. Confocal analysis of surface-labeled hemagglutinin-alpha(1a)AR reveals that basal and stimulated receptor occupies clathrin pits in fixed cells consistent with previous indirect evidence. The evidence presented here strongly suggests the alpha(1a)AR is a lipid raft protein under basal conditions and implies agonist-mediated signaling occurs from rafts.
Collapse
Affiliation(s)
- Daniel P Morris
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA.
| | | | | | | | | |
Collapse
|
31
|
Chanrion B, Mannoury la Cour C, Gavarini S, Seimandi M, Vincent L, Pujol JF, Bockaert J, Marin P, Millan MJ. Inverse agonist and neutral antagonist actions of antidepressants at recombinant and native 5-hydroxytryptamine2C receptors: differential modulation of cell surface expression and signal transduction. Mol Pharmacol 2007; 73:748-57. [PMID: 18083778 DOI: 10.1124/mol.107.041574] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Despite the importance of 5-hydroxytryptamine (5-HT)(2C) (serotonin) receptors in the control of depressive states, actions of antidepressants at these receptors remain poorly characterized. This issue was addressed both in human embryonic kidney (HEK)-293 cells coexpressing unedited human 5-HT(2CINI) receptors and Galpha(q) protein and in cultured mouse cortical neurons. Indicative of constitutive activity, the inverse agonist SB206,553 decreased basal inositol phosphate (IP) production in HEK-293 cells. The tetracyclic antidepressants mirtazapine and mianserin likewise suppressed basal IP formation. Conversely, the tricyclics amitriptyline and clomipramine, the m-chlorophenylpiperazine derivatives trazodone and nefazodone, and the 5-HT reuptake inhibitors fluoxetine and citalopram were inactive alone, although they blocked 5-HT-induced IP production. Inverse agonist actions of 5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2,3-f]indole (SB206,553) and mirtazapine were abolished by the neutral antagonist 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy)pyridin-3-ylcarbamoyl]indoline (SB242,084), which was inactive alone. As assessed by confocal microscopy and enzyme-linked immunosorbent assay, prolonged treatment of HEK-293 cells with SB206,553, mirtazapine, or mianserin, but not the other antidepressants, enhanced cell surface expression of 5-HT(2C) receptors: 5-HT-induced IP production was also increased, and both these actions were blocked by SB242,084. Cortical neurons were shown by reverse transcription-polymerase chain reaction to predominantly express constitutively active 5-HT(2C) receptor isoforms. Prolonged pretreatment with SB206,553 or mirtazapine triggered an otherwise absent 5-HT-induced elevation in cytosolic Ca(2+) concentrations. SB242,084, which was inactive alone, abolished these effects of SB206,553 and mirtazapine. In conclusion, the tetracyclic antidepressants mirtazapine and mianserin, but not other clinically established antidepressants, suppress constitutive activity at recombinant and native 5-HT(2C) receptors. The clinical significance of inverse agonist versus neutral antagonist properties both during and after drug administration will be of interest to elucidate.
Collapse
Affiliation(s)
- Benjamin Chanrion
- Institut de Génomique Fonctionnelle, Universités de Montpellier, CNRS UMRS 5203, INSERM U661, 141 rue de la Cardonille, F-34094 Montpellier Cedex 5, France
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Molina-Muñoz T, Romero-Avila MT, Avendaño-Vázquez SE, García-Sáinz JA. Phosphorylation, desensitization and internalization of human alpha1B-adrenoceptors induced by insulin-like growth factor-I. Eur J Pharmacol 2007; 578:1-10. [PMID: 17915215 DOI: 10.1016/j.ejphar.2007.08.047] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/21/2007] [Accepted: 08/24/2007] [Indexed: 10/22/2022]
Abstract
The effect of insulin-like growth factor-I (IGF-I) on human alpha(1B)-adrenoceptor function, phosphorylation state and cellular location was studied. Rat-1 fibroblasts were transfected with a plasmid construction containing enhanced green fluorescent protein joined to the carboxyl terminus of the human alpha(1B)-adrenoceptor. Receptors were identified by radioligand binding and photoaffinity labeling, and were immunoprecipitated with an antiserum generated against the enhanced green fluorescent protein. The receptor was functional, as evidenced by noradrenaline action on intracellular calcium and inositol phosphate production. IGF-I had no significant effect by itself on these parameters but markedly reduced the effects of noradrenaline. IGF-I induced alpha(1B)-adrenoceptor phosphorylation, which was markedly reduced by the following agents: pertussis toxin, a metalloproteinase inhibitor, diphtheria toxin mutant CRM 197, an epidermal growth factor (EGF) receptor intrinsic kinase activity inhibitor, and by phosphoinositide 3-kinase and protein kinase C inhibitors. IGF-I action appears to involve activation of a pertussis toxin-sensitive G protein, shedding of heparin-binding EGF and autocrine activation of EGF receptors. G protein subunits and phosphotyrosine residues stimulate phosphoinositide 3-kinase activity leading to activation of protein kinase C, which in turn phosphorylates alpha(1B)-adrenoceptors. Confocal fluorescent microscopy showed that alpha(1B)-adrenoceptors fussed to the green fluorescent protein were located in plasma membrane and intracellular vesicles in the basal state. IGF-I induced receptor redistribution favoring the intracellular location; this effect was blocked by hypertonic sucrose and concanavalin A. Our data show that IGF-I induces alpha(1B)-adrenoceptor desensitization associated to receptor phosphorylation and internalization.
Collapse
Affiliation(s)
- Tzindilú Molina-Muñoz
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F. 04510, Mexico
| | | | | | | |
Collapse
|
33
|
Walwyn W, Evans CJ, Hales TG. Beta-arrestin2 and c-Src regulate the constitutive activity and recycling of mu opioid receptors in dorsal root ganglion neurons. J Neurosci 2007; 27:5092-104. [PMID: 17494695 PMCID: PMC6672367 DOI: 10.1523/jneurosci.1157-07.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 03/30/2007] [Accepted: 04/01/2007] [Indexed: 11/21/2022] Open
Abstract
Beta-arrestins bind to agonist-activated G-protein-coupled receptors regulating signaling events and initiating endocytosis. In beta-arrestin2-/- (beta arr2-/-) mice, a complex phenotype is observed that includes altered sensitivity to morphine. However, little is known of how beta-arrestin2 affects mu receptor signaling. We investigated the coupling of mu receptors to voltage-gated Ca2+ channels (VGCCs) in beta arr2+/+ and beta arr2-/- dorsal root ganglion neurons. A lack of beta-arrestin2 reduced the maximum inhibition of VGCCs by morphine and DAMGO (D-Ala2-N-Me-Phe4-glycol5-enkephalin) without affecting agonist potency, the onset of receptor desensitization, or the functional contribution of N-type VGCCs. The reduction in inhibition was accompanied by increased naltrexone-sensitive constitutive inhibitory coupling of mu receptors to VGCCs. Agonist-independent mu receptor inhibitory coupling was insensitive to CTAP (Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), a neutral antagonist that inhibited the inverse agonist action of naltrexone. These functional changes were accompanied by diminished constitutive recycling and increased cell-surface mu receptor expression in beta arr2-/- compared with beta arr2+/+ neurons. Such changes could not be explained by the classical role of beta-arrestins in agonist-induced endocytosis. The localization of the nonreceptor tyrosine kinase c-Src appeared disrupted in beta arr2-/- neurons, and there was reduced activation of c-Src by DAMGO. Using the Src inhibitor PP2 [4-amino-5-(4-chlorophenyl)-(t-butyl)pyrazolo[3,4-d]pyrimidine], we demonstrated that defective Src signaling mimics the beta arr2-/- cellular phenotype of reduced mu agonist efficacy, increased constitutive mu receptor activity, and reduced constitutive recycling. We propose that beta-arrestin2 is required to target c-Src to constitutively active mu receptors, resulting in their internalization, providing another dimension to the complex role of beta-arrestin2 and c-Src in G-protein-coupled receptor function.
Collapse
MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Arrestins/genetics
- Arrestins/metabolism
- CSK Tyrosine-Protein Kinase
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cells, Cultured
- Endocytosis/drug effects
- Endocytosis/physiology
- Female
- Ganglia, Spinal/metabolism
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Nociceptors/drug effects
- Nociceptors/metabolism
- Pain/metabolism
- Pain/physiopathology
- Patch-Clamp Techniques
- Protein Transport/drug effects
- Protein Transport/physiology
- Protein-Tyrosine Kinases/metabolism
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- beta-Arrestin 2
- beta-Arrestins
- src-Family Kinases
Collapse
Affiliation(s)
- Wendy Walwyn
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Christopher J. Evans
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Tim G. Hales
- Departments of Pharmacology and Physiology, and Anesthesiology and Critical Care Medicine, The George Washington University, Washington, DC 20037
| |
Collapse
|
34
|
Abstract
G protein-coupled receptors (GPCRs) mediate cellular responses to diverse extracellular stimuli to play a vital role in the control of physiology and behaviour. GPCR trafficking is of fundamental importance for the regulation of GPCRs signaling. In this mini review, we will discuss some of the recent findings on the mechanisms that regulate GPCR trafficking, which include (i) large dense-core vesicle (LDCV)-associated GPCR delivery which could be a general cell biological mechanism for rapid modulation of membrane receptors in response to certain stimuli; (ii) lateral diffusion of GPCRs in the plasma membrane for rapid change of the number of neurotransmitter receptors during synaptic plasticity and (iii) constitutive internalization of GPCRs, that contributes to receptor resensitization and distribution, including axonal polarization.
Collapse
Affiliation(s)
- Z-Q D Xu
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | | | | |
Collapse
|
35
|
Michelotti GA, Brinkley DM, Morris DP, Smith MP, Louie RJ, Schwinn DA. Epigenetic regulation of human alpha1d-adrenergic receptor gene expression: a role for DNA methylation in Sp1-dependent regulation. FASEB J 2007; 21:1979-93. [PMID: 17384146 PMCID: PMC2279228 DOI: 10.1096/fj.06-7118com] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A growing body of evidence implicates alpha1-adrenergic receptors (alpha1ARs) as potent regulators of growth pathways. The three alpha1AR subtypes (alpha1aAR, alpha1bAR, alpha1dAR) display highly restricted tissue expression that undergoes subtype switching with many pathological stimuli, the mechanistic basis of which remains unknown. To gain insight into transcriptional pathways governing cell-specific regulation of the human alpha1dAR subtype, we cloned and characterized the alpha1dAR promoter region in two human cellular models that display disparate levels of endogenous alpha1dAR expression (SK-N-MC and DU145). Results reveal that alpha1dAR basal expression is regulated by Sp1-dependent binding of two promoter-proximal GC boxes, the mutation of which attenuates alpha1dAR promoter activity 10-fold. Mechanistically, chromatin immunoprecipitation data demonstrate that Sp1 binding correlates with expression of the endogenous gene in vivo, correlating highly with alpha1dAR promoter methylation-dependent silencing of both episomally expressed reporter constructs and the endogenous gene. Further, analysis of methylation status of proximal GC boxes using sodium bisulfite sequencing reveals differential methylation of proximal GC boxes in the two cell lines examined. Together, the data support a mechanism of methylation-dependent disruption of Sp1 binding in a cell-specific manner resulting in repression of basal alpha1dAR expression.
Collapse
MESH Headings
- Azacitidine/analogs & derivatives
- Azacitidine/pharmacology
- Base Sequence
- Cell Line, Tumor
- Chromatin/chemistry
- DNA (Cytosine-5-)-Methyltransferases/antagonists & inhibitors
- DNA Methylation
- Decitabine
- Gene Expression Regulation
- Gene Silencing
- Humans
- Immunoprecipitation
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Promoter Regions, Genetic/genetics
- Protein Binding
- RNA, Messenger/biosynthesis
- Receptors, Adrenergic, alpha-1/biosynthesis
- Receptors, Adrenergic, alpha-1/genetics
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sp1 Transcription Factor/metabolism
- Sulfites/pharmacology
- Transcription, Genetic
Collapse
Affiliation(s)
- Gregory A Michelotti
- Department of Pharmacology/Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
| | | | | | | | | | | |
Collapse
|
36
|
Huang Y, Wright CD, Merkwan CL, Baye NL, Liang Q, Simpson PC, O'Connell TD. An α1A-Adrenergic–Extracellular Signal-Regulated Kinase Survival Signaling Pathway in Cardiac Myocytes. Circulation 2007; 115:763-72. [PMID: 17283256 DOI: 10.1161/circulationaha.106.664862] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Background—
In α1-AR knockout (α1ABKO) mice that lacked cardiac myocyte α1-adrenergic receptor (α1-AR) binding, aortic constriction induced apoptosis, dilated cardiomyopathy, and death. However, it was unclear whether these effects were attributable to a lack of cardiac myocyte α1-ARs and whether the α1A, α1B, or both subtypes mediated protection. Therefore, we investigated α1A and α1B subtype–specific survival signaling in cultured cardiac myocytes to test for a direct protective effect of α1-ARs in cardiac myocytes.
Methods and Results—
We cultured α1ABKO myocytes and reconstituted α1-AR signaling with adenoviruses expressing α1-GFP fusion proteins. Myocyte death was induced by norepinephrine, doxorubicin, or H
2
O
2
and was measured by annexin V/propidium iodide staining. In α1ABKO myocytes, all 3 stimuli significantly increased apoptosis and necrosis. Reconstitution of the α1A subtype, but not the α1B, rescued α1ABKO myocytes from cell death induced by each stimulus. To address the mechanism, we examined α1-AR activation of extracellular signal-regulated kinase (ERK). In α1ABKO hearts, aortic constriction failed to activate ERK, and in α1ABKO myocytes, expression of a constitutively active MEK1 rescued α1ABKO myocytes from norepinephrine-induced death. In addition, only the α1A-AR activated ERK in α1ABKO myocytes, and expression of a dominant-negative MEK1 completely blocked α1A survival signaling in α1ABKO myocytes.
Conclusions—
Our results demonstrate a direct protective effect of the α1A subtype in cardiac myocytes and define an α1A-ERK signaling pathway that is required for myocyte survival. Absence of the α1A-ERK pathway can explain the failure to activate ERK after aortic constriction in α1ABKO mice and can contribute to the development of apoptosis, dilated cardiomyopathy, and death.
Collapse
Affiliation(s)
- Yuan Huang
- Cardiovascular Research Institute, Sanford Research/USD, and Department of Medicine, The University of South Dakota School of Medicine, Sioux Falls, SD 57105, USA
| | | | | | | | | | | | | |
Collapse
|
37
|
Lopez-Gimenez JF, Canals M, Pediani JD, Milligan G. The alpha1b-adrenoceptor exists as a higher-order oligomer: effective oligomerization is required for receptor maturation, surface delivery, and function. Mol Pharmacol 2007; 71:1015-29. [PMID: 17220353 DOI: 10.1124/mol.106.033035] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Approaches to identify G protein-coupled receptor oligomers rather than dimers have been lacking. Using concatamers of fluorescent proteins, we established conditions to monitor sequential three-color fluorescence resonance energy transfer (3-FRET) and used these to detect oligomeric complexes of the alpha(1b)-adrenoceptor in single living cells. Mutation of putative key hydrophobic residues in transmembrane domains I and IV resulted in substantial reduction of sequential 3-FRET and was associated with lack of protein maturation, prevention of plasma membrane delivery, and elimination of signaling function. Although these mutations prevented cell surface delivery, bimolecular fluorescence complementation studies indicated that they did not ablate protein-protein interactions and confirmed endoplasmic reticulum/Golgi retention of the transmembrane domain I plus transmembrane domain IV mutated receptor. The transmembrane domain I plus transmembrane domain IV mutated receptor was a "dominant-negative" in blocking cell surface delivery of the wild-type receptor. Mutations only in transmembrane domain I did not result in a reduction in 3-FRET, whereas restricting mutation to transmembrane domain IV did result in reduced 3-FRET. Mutations in either transmembrane domain I or transmembrane domain IV, however, were sufficient to eliminate cell surface delivery. Terminal N-glycosylation is insufficient to determine cell surface delivery because both transmembrane domain I and transmembrane domain IV mutants matured as effectively as the wild-type receptor. These data indicate that the alpha(1b)-adrenoceptor is able to form oligomeric rather than only simple dimeric complexes and that disruption of effective oligomerization by introducing mutations into transmembrane domain IV has profound consequences for cell surface delivery and function.
Collapse
MESH Headings
- Cell Line
- Cell Membrane/metabolism
- Dimerization
- Fluorescence Resonance Energy Transfer
- Glycosylation
- Humans
- Mutagenesis, Site-Directed
- Protein Transport
- Receptors, Adrenergic, alpha-1/chemistry
- Receptors, Adrenergic, alpha-1/genetics
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-1/physiology
- Receptors, Cell Surface
- Transfection
Collapse
Affiliation(s)
- Juan F Lopez-Gimenez
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | | | | | | |
Collapse
|
38
|
Parallel inactivation of Y2 receptor and G-proteins in CHO cells by pertussis toxin. ACTA ACUST UNITED AC 2006; 139:128-35. [PMID: 17175038 DOI: 10.1016/j.regpep.2006.10.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 10/22/2006] [Indexed: 02/04/2023]
Abstract
The Y(2) receptor for neuropeptide Y (NPY) interacts with pertussis toxin (PTX)-sensitive G-proteins, but little is known about interdependence of their levels and functions. We found that PTX reduces Y(2) receptors expressed in CHO cells in parallel to inactivation of Gi G-proteins, to loss of inhibition by Y(2) agonists of forskolin-stimulated adenylyl cyclase, and to decrease in the binding of GTP-gamma-S. These losses were attenuated by the endosome alkalinizer ammonium chloride. Affinity of the Y(2) receptor was not changed by PTX treatment. Prolonged treatment induced a large decrease of Y(2) receptor immunoreactivity (more than 70% in 48 h). The Gi(3) alpha-subunit immunoreactivity decreased slowly (about 46% in 48 h). There was a significant increase in Gq alpha immunoreactivity and in fraction of Y(2) binding sensitive to a Gq-selective antagonist. Possibly linked to that, the surface Y(2) sites and the internalization of the Y(2) receptor were less than 40% reduced. However, the abundant masked Y(2) sites were eliminated by the toxin, and could be mainly coupled to PTX-sensitive G-proteins.
Collapse
|
39
|
Mohammad S, Baldini G, Granell S, Narducci P, Martelli AM, Baldini G. Constitutive traffic of melanocortin-4 receptor in Neuro2A cells and immortalized hypothalamic neurons. J Biol Chem 2006; 282:4963-4974. [PMID: 17166828 DOI: 10.1074/jbc.m608283200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Melanocortin-4 receptor (MC4R) is a G protein-coupled receptor (GPCR) that binds alpha-melanocyte-stimulating hormone (alpha-MSH) and has a central role in the regulation of appetite and energy expenditure. Most GPCRs are endocytosed following binding to the agonist and receptor desensitization. Other GPCRs are internalized and recycled back to the plasma membrane constitutively, in the absence of the agonist. In unstimulated neuroblastoma cells and immortalized hypothalamic neurons, epitopetagged MC4R was localized both at the plasma membrane and in an intracellular compartment. These two pools of receptors were in dynamic equilibrium, with MC4R being rapidly internalized and exocytosed. In the absence of alpha-MSH, a fraction of cell surface MC4R localized together with transferrin receptor and to clathrin-coated pits. Constitutive MC4R internalization was impaired by expression of a dominant negative dynamin mutant. Thus, MC4R is internalized together with transferrin receptor by clathrin-dependent endocytosis. Cell exposure toalpha-MSH reduced the amount of MC4R at the plasma membrane by blocking recycling of a fraction of internalized receptor, rather than by increasing its rate of endocytosis. The data indicate that, in neuronal cells, MC4R recycles constitutively and that alpha-MSH modulates MC4R residency at the plasma membrane by acting at an intracellular sorting step.
Collapse
Affiliation(s)
- Sameer Mohammad
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Giovanna Baldini
- Dipartimento di Morfologia Umana Normale, via Manzoni 16, Universita' di Trieste, I-34138 Trieste, Italy, and the
| | - Susana Granell
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Paola Narducci
- Dipartimento di Morfologia Umana Normale, via Manzoni 16, Universita' di Trieste, I-34138 Trieste, Italy, and the
| | - Alberto M Martelli
- Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia, Cell Signalling Laboratory, Universita' di Bologna, via Irnerio 48, I-40126 Bologna, Italy
| | - Giulia Baldini
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
| |
Collapse
|
40
|
Hein P, Michel MC. Signal transduction and regulation: are all alpha1-adrenergic receptor subtypes created equal? Biochem Pharmacol 2006; 73:1097-106. [PMID: 17141737 DOI: 10.1016/j.bcp.2006.11.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 10/30/2006] [Accepted: 11/01/2006] [Indexed: 02/06/2023]
Abstract
The current manuscript reviews the evidence whether and how subtypes of alpha(1)-adrenergic receptors, i.e. alpha(1A)-, alpha(1B)- and alpha(1D)-adrenergic receptors, differentially couple to signal transduction pathways and exhibit differential susceptibility to regulation. In both regards studies in tissues or cells natively expressing the subtypes are hampered because the relative expression of the subtypes is poorly controlled and the observed effects may be cell-type specific. An alternative approach, i.e. transfection of multiple subtypes into the same host cell line overcomes this limitation, but it often remains unclear whether results in such artificial systems are representative for the physiological situation. The overall evidence suggests that indeed subtype-intrinsic and cell type-specific factors interact to direct alpha(1)-adrenergic receptor signaling and regulation. This may explain why so many apparently controversial findings have been reported from various tissues and cells. One of the few consistent themes is that alpha(1D)-adrenergic receptors signal less effectively upon agonist stimulation than the other subtypes, most likely because they exhibit spontaneous internalization.
Collapse
Affiliation(s)
- Peter Hein
- Department of Pharmacology, University of Würzburg, Würzburg, Germany
| | | |
Collapse
|
41
|
Milligan G, Pediani JD, Canals M, Lopez-Gimenez JF. Oligomeric structure of the alpha1b-adrenoceptor: comparisons with rhodopsin. Vision Res 2006; 46:4434-41. [PMID: 17005232 DOI: 10.1016/j.visres.2006.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 08/07/2006] [Accepted: 08/08/2006] [Indexed: 11/20/2022]
Abstract
The structural basis of the quaternary organization of rhodopsin has recently been explored and modeled. Because information obtained from studying rhodopsin has frequently been directly applicable to other G protein-coupled receptors we wished to ascertain if dimeric and/or oligomeric forms of the alpha(1b)-adrenoceptor could be observed and if so whether rhodopsin might provide insights into the quaternary structure of this receptor. Co-immunoprecipitation and both conventional and time-resolved fluorescence resonance energy transfer studies demonstrated quaternary structure of the alpha(1b)-adrenoceptor and, in concert with the reconstitution of fragments of this receptor, provided information on the molecular basis of these interactions. Development of three color fluorescence resonance energy transfer (FRET) allowed the imaging of alpha(1b)-adrenoceptor oligomers in single living cells. Mutation of hydrophobic residues in transmembrane domains I and IV of the receptor resulted in marked reduction in three color FRET suggesting an alteration in oligomeric organization and potential similarities with rhodopsin. The mutated alpha(1b)-adrenoceptor was unable to reach the cell surface, did not become terminally N-glycosylated and was unable to signal.
Collapse
Affiliation(s)
- Graeme Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
| | | | | | | |
Collapse
|
42
|
Jacquier V, Prummer M, Segura JM, Pick H, Vogel H. Visualizing odorant receptor trafficking in living cells down to the single-molecule level. Proc Natl Acad Sci U S A 2006; 103:14325-30. [PMID: 16980412 PMCID: PMC1599963 DOI: 10.1073/pnas.0603942103] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite the importance of trafficking for regulating G protein-coupled receptor signaling, for many members of the seven transmembrane helix protein family, such as odorant receptors, little is known about this process in live cells. Here, the complete life cycle of the human odorant receptor OR17-40 was directly monitored in living cells by ensemble and single-molecule imaging, using a double-labeling strategy. While the overall, intracellular trafficking of the receptor was visualized continuously by using a GFP tag, selective imaging of cell surface receptors was achieved by pulse-labeling an acyl carrier protein tag. We found that OR17-40 efficiently translocated to the plasma membrane only at low expression, whereas at higher biosynthesis the receptor accumulated in intracellular compartments. Receptors in the plasma membrane showed high turnover resulting from constitutive internalization along the clathrin pathway, even in the absence of ligand. Single-molecule microscopy allowed monitoring of the early, dynamic processes in odorant receptor signaling. Although mobile receptors initially diffused either freely or within domains of various sizes, binding of an agonist or an antagonist increased partitioning of receptors into small domains of approximately 190 nm, which likely are precursors of clathrin-coated pits. The binding of a ligand, therefore, resulted in modulation of the continuous, constitutive internalization. After endocytosis, receptors were directed to early endosomes for recycling. This unique mechanism of continuous internalization and recycling of OR17-40 might be instrumental in allowing rapid recovery of odor perception.
Collapse
Affiliation(s)
- V. Jacquier
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - M. Prummer
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - J.-M. Segura
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - H. Pick
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - H. Vogel
- Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- *To whom correspondence should be addressed. E-mail:
| |
Collapse
|
43
|
Behrens M, Bartelt J, Reichling C, Winnig M, Kuhn C, Meyerhof W. Members of RTP and REEP gene families influence functional bitter taste receptor expression. J Biol Chem 2006; 281:20650-9. [PMID: 16720576 DOI: 10.1074/jbc.m513637200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional characterization of chemosensory receptors is usually achieved by heterologous expression in mammalian cell lines. However, many chemoreceptor genes, including bitter taste receptors (TAS2Rs), show only marginal cell surface expression. Usually, these problems are circumvented by using chimeric receptors consisting of "export tags" and the receptor sequence itself. It seems likely that chemoreceptor cells express factors for cell surface targeting of native receptor molecules in vivo. For TAS2Rs, however, such factors are still unknown. The present study investigates the influence of RTP and REEP proteins on the functional expression of human TAS2Rs in heterologous cells. We expressed hTAS2Rs in HEK 293T cells and observed dramatic differences in responsiveness to agonist stimulation. By immunocytochemistry we show accumulation of the bitter beta-glucopyranoside receptor hTAS2R16 in the Golgi compartment. Coexpression of RTP and REEP proteins changed the responses of some hTAS2Rs upon agonist stimulation, which is likely due to efficient cell surface localization as demonstrated by cell surface biotinylation experiments. The coimmunoprecipitation of hTAS2R16 and RTP3 or RTP4 suggests that the mechanism by which these cofactors influence hTAS2R16 function might involve direct protein-protein interaction. Finally, expression analyses demonstrate RTP and REEP gene expression in human circumvallate papillae and testis, both of which are sites of TAS2R gene expression.
Collapse
Affiliation(s)
- Maik Behrens
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | | | | | | | | | | |
Collapse
|
44
|
Xu Q, Xu N, Zhang T, Zhang H, Li Z, Yin F, Lu Z, Han Q, Zhang Y. Mammalian Tolloid Alters Subcellular Localization, Internalization, and Signaling of α1a-Adrenergic Receptors. Mol Pharmacol 2006; 70:532-41. [PMID: 16690783 DOI: 10.1124/mol.105.016451] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we identified the CUB5 domain of mammalian Tolloid (mTLD) as a novel protein binding to alpha(1A)-adrenergic receptor (AR) using the yeast two-hybrid system. Whereas CUB5 did not couple to either alpha(1B)-AR or alpha(1D)-AR. It was determined that amino acids 322 to 359 of alpha(1A)-AR were the major binding region for CUB5. The direct interaction between alpha(1A)-AR cytoplasmic tail and CUB5 was discovered by glutathione S-transferase pull-down assay. We confirmed the interaction of mTLD with alpha(1A)-AR in human embryonic kidney (HEK) 293 cells by immunoprecipitation, immunofluorescence, and fluorescence resonance energy transfer. Although mTLD did not affect the density and affinity of receptors in crudely prepared membranes from HEK293 cells stably expressing alpha(1A)-AR, it significantly altered the subcellular localization of the receptors. Moreover, mTLD reduced the level of cell surface alpha(1A)-ARs, delayed the initial rate of agonist-induced receptor internalization, and facilitated agonist-induced calcium transient. We have demonstrated that mTLD interacts with alpha(1A)-AR directly, alters the subcellular localization of receptor, and influences agonist-induced alpha(1A)-AR internalization and calcium signaling.
Collapse
Affiliation(s)
- Qi Xu
- Institute of Vascular Medicine, Peking University Third Hospital, No.49 Huayuan North Road, Haidian District, Beijing, P.R. China 100083
| | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Leterrier C, Lainé J, Darmon M, Boudin H, Rossier J, Lenkei Z. Constitutive activation drives compartment-selective endocytosis and axonal targeting of type 1 cannabinoid receptors. J Neurosci 2006; 26:3141-53. [PMID: 16554465 PMCID: PMC6674101 DOI: 10.1523/jneurosci.5437-05.2006] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The type 1 cannabinoid receptor (CB1R) is one of the most abundant G-protein-coupled receptors (GPCRs) in the brain, predominantly localized to axons of GABAergic neurons. Like several other neuronal GPCRs, CB1R displays significant in vitro constitutive activity (i.e., spontaneous activation in the absence of ligand). However, a clear biological role for constitutive GPCR activity is still lacking. This question was addressed by studying the consequences of constitutive activation on the intracellular trafficking of endogenous or transfected CB1Rs in cultured hippocampal neurons using optical and electron microscopy. We found that constitutive activity results in a permanent cycle of endocytosis and recycling, which is restricted to the somatodendritic compartment. Thus, CB1Rs are continuously removed by endocytosis from the plasma membrane in the somatodendritic compartment but not in axons, where CB1Rs accumulate on surface. Blocking constitutive activity by short-term incubation with inverse agonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM281) results in sequestration of recycled CB1Rs on the somatodendritic plasma membrane. Long-term inhibition of endocytosis by cotransfection of dominant-negative proteins results in impaired axonal polarization of surface-bound CB1Rs. Kinetic analysis shows that the majority of newly synthesized CB1Rs arrive first to the somatodendritic plasma membrane, from where they are rapidly removed by AM281-sensitive constitutive endocytosis before being delivered to axons. Thus, constitutive-activity driven somatodendritic endocytosis is required for the proper axonal targeting of CB1R, representing a novel, conformation-dependent targeting mechanism for axonal GPCRs.
Collapse
|
46
|
SCHAMBRA UB, MACKENSEN GB, STAFFORD-SMITH M, HAINES DE, SCHWINN DA. Neuron specific alpha-adrenergic receptor expression in human cerebellum: implications for emerging cerebellar roles in neurologic disease. Neuroscience 2006; 135:507-23. [PMID: 16112482 PMCID: PMC2277099 DOI: 10.1016/j.neuroscience.2005.06.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 06/06/2005] [Accepted: 06/15/2005] [Indexed: 12/13/2022]
Abstract
Recent data suggest novel functional roles for cerebellar involvement in a number of neurologic diseases. Function of cerebellar neurons is known to be modulated by norepinephrine and adrenergic receptors. The distribution of adrenergic receptor subtypes has been described in experimental animals, but corroboration of such studies in the human cerebellum, necessary for drug treatment, is still lacking. In the present work we studied cell-specific localizations of alpha1 adrenergic receptor subtype mRNA (alpha 1a, alpha 1b, alpha 1d), and alpha2 adrenergic receptor subtype mRNA (alpha 2a, alpha 2b, alpha 2c) by in situ hybridization on cryostat sections of human cerebellum (cortical layers and dentate nucleus). We observed unique neuron-specific alpha1 adrenergic receptor and alpha2 adrenergic receptor subtype distribution in human cerebellum. The cerebellar cortex expresses mRNA encoding all six alpha adrenergic receptor subtypes, whereas dentate nucleus neurons express all subtype mRNAs, except alpha 2a adrenergic receptor mRNA. All Purkinje cells label strongly for alpha 2a and alpha 2b adrenergic receptor mRNA. Additionally, Purkinje cells of the anterior lobe vermis (lobules I to V) and uvula/tonsil (lobules IX/HIX) express alpha 1a and alpha 2c subtypes, and Purkinje cells in the ansiform lobule (lobule HVII) and uvula/tonsil express alpha 1b and alpha 2c adrenergic receptor subtypes. Basket cells show a strong signal for alpha 1a, moderate signal for alpha 2a and light label for alpha 2b adrenergic receptor mRNA. In stellate cells, besides a strong label of alpha 2a adrenergic receptor mRNA in all and moderate label of alpha 2b message in select stellate cells, the inner stellate cells are also moderately positive for alpha 1b adrenergic receptor mRNA. Granule and Golgi cells express high levels of alpha 2a and alpha 2b adrenergic receptor mRNAs. These data contribute new information regarding specific location of adrenergic receptor subtypes in human cerebellar neurons. We discuss our observations in terms of possible modulatory roles of adrenergic receptor subtypes in cerebellar neurons responding to sensory and autonomic input signals, and review species differences in cerebellar adrenergic receptor expression.
Collapse
Affiliation(s)
- U. B. SCHAMBRA
- Department of Anatomy and Cell Biology, Quillen College of Medicine, East Tennessee State University, Box 70582, Johnson City, TN 37614-0582, USA
- *Corresponding author. Tel: +1-423-439-2014; fax: +1-423-439-2017. E-mail address: (U. B. Schambra)
| | - G. B. MACKENSEN
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - M. STAFFORD-SMITH
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - D. E. HAINES
- Department of Anatomy, University of Mississippi Medical Center, Jackson, MS 39216, USA
| | - D. A. SCHWINN
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA
- Department of Pharmacology/Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
- *Corresponding author. Tel: +1-423-439-2014; fax: +1-423-439-2017. E-mail address: (U. B. Schambra)
| |
Collapse
|
47
|
Oh DY, Kim K, Kwon HB, Seong JY. Cellular and molecular biology of orphan G protein-coupled receptors. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 252:163-218. [PMID: 16984818 DOI: 10.1016/s0074-7696(06)52003-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The superfamily of G protein-coupled receptors (GPCRs) is the largest and most diverse group of membrane-spanning proteins. It plays a variety of roles in pathophysiological processes by transmitting extracellular signals to cells via heterotrimeric G proteins. Completion of the human genome project revealed the presence of approximately 168 genes encoding established nonsensory GPCRs, as well as 207 genes predicted to encode novel GPCRs for which the natural ligands remained to be identified, the so-called orphan GPCRs. Eighty-six of these orphans have now been paired to novel or previously known molecules, and 121 remain to be deorphaned. A better understanding of the GPCR structures and classification; knowledge of the receptor activation mechanism, either dependent on or independent of an agonist; increased understanding of the control of GPCR-mediated signal transduction; and development of appropriate ligand screening systems may improve the probability of discovering novel ligands for the remaining orphan GPCRs.
Collapse
Affiliation(s)
- Da Young Oh
- Laboratory of G Protein-Coupled Receptors, Korea University College of Medicine, Seoul 136-707, Korea
| | | | | | | |
Collapse
|
48
|
Abstract
A wide range of approaches has been applied to examine the quaternary structure of G protein-coupled receptors, the basis of such protein-protein interactions and how such interactions might modulate the pharmacology and function of these receptors. These include co-immunoprecipitation, various adaptations of resonance energy transfer techniques, functional complementation studies and the analysis of ligand-binding data. Each of the available techniques has limitations that restrict interpretation of the data. However, taken together, they provide a coherent body of evidence indicating that many, if not all, G protein-coupled receptors exist and function as dimer/oligomers. Herein we assess the widely applied techniques and discuss the relative benefits and limitations of these approaches.
Collapse
Affiliation(s)
- Graeme Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, UK
| | | |
Collapse
|
49
|
Wang L, Radu CG, Yang LV, Bentolila LA, Riedinger M, Witte ON. Lysophosphatidylcholine-induced surface redistribution regulates signaling of the murine G protein-coupled receptor G2A. Mol Biol Cell 2005; 16:2234-47. [PMID: 15728718 PMCID: PMC1087231 DOI: 10.1091/mbc.e04-12-1044] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intracellular trafficking and spatial dynamics of membrane receptors critically regulate receptor function. Using microscopic and subcellular fractionation analysis, we studied the localization of the murine G protein-coupled receptor G2A (muG2A). Evaluating green fluorescent protein-tagged, exogenously expressed as well as the endogenous muG2A, we observed that this receptor was spontaneously internalized and accumulated in endosomal compartments, whereas its surface expression was enhanced and stabilized by lysophosphatidylcholine (LPC) treatment. Monensin, a general inhibitor of recycling pathways, blocked LPC-regulated surface localization of muG2A as well as muG2A-dependent extracellular signal-regulated kinase (ERK) activation and cell migration induced by LPC treatment. Mutation of the conserved DRY motif (R-->A) enhanced the surface expression of muG2A, resulting in its resistance to monensin inhibition of ERK activation. Our data suggest that intracellular sequestration and surface expression regulated by LPC, rather than direct agonistic activity control the signaling responses of murine G2A toward LPC.
Collapse
Affiliation(s)
- Li Wang
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
| | | | | | | | | | | |
Collapse
|
50
|
Guthrie CR, Murray AT, Franklin AA, Hamblin MW. Differential agonist-mediated internalization of the human 5-hydroxytryptamine 7 receptor isoforms. J Pharmacol Exp Ther 2005; 313:1003-10. [PMID: 15716386 DOI: 10.1124/jpet.104.081919] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The human 5-hydroxytryptamine 7 (5-HT(7)) serotonin receptor is a class A G-protein coupled receptor that has three isoforms, 5-HT(7(a)), 5-HT(7(b)), and 5-HT(7(d)), which are produced by alternative splicing. The 5-HT(7) receptors are expressed in discrete areas of the brain and in both vascular and gastrointestinal smooth muscle. Central nervous system 5-HT(7) receptors may play a role in mood and sleep disorders. 5-HT(7) receptors show high affinity for a number of antidepressants and typical and atypical antipsychotics. We report here that the human 5-HT(7(d)) isoform expressed in human embryonic kidney (HEK) 293 cells exhibits a pattern of receptor trafficking in response to agonist that differ from 5-HT(7(a)) or 5-HT(7(b)) isoforms. We employed a modification of a live cell-labeling technique to demonstrate that surface 5-HT(7(d)) receptors are constitutively internalized in the absence of agonist. This is in contrast to 5-HT(7(a)) and 5-HT(7(b)) isoforms, which do not show this profound agonist-independent internalization. Indeed, the 5-HT(7(d)) isoform displays this internalization in the presence of a 5-HT(7) -specific antagonist. In addition, the human 5-HT(7) isoform shows a diminished efficacy in stimulation of cAMP-responsive reporter gene activity in transfected cells compared with 5-HT(7(a)) or 5-HT(7(b)) receptors expressed at comparable levels. Thus, the carboxy-terminal tail of 5-HT(7(d)), which is the longest among known human 5-HT(7) isoforms, may contain a motif that interacts with cellular transport mechanisms that is distinct from 5-HT(7(a)) and 5-HT(7(b)).
Collapse
Affiliation(s)
- Chris R Guthrie
- Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108, USA.
| | | | | | | |
Collapse
|