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Durydivka O, Mackie K, Blahos J. SGIP1 in axons prevents internalization of desensitized CB1R and modifies its function. Front Neurosci 2023; 17:1213094. [PMID: 37547151 PMCID: PMC10397514 DOI: 10.3389/fnins.2023.1213094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/04/2023] [Indexed: 08/08/2023] Open
Abstract
In the central nervous system (CNS), cannabinoid receptor 1 (CB1R) is preferentially expressed in axons where it has a unique property, namely resistance to agonist-driven endocytosis. This review aims to summarize what we know about molecular mechanisms of CB1R cell surface stability in axonal compartments, how these impact CB1R signaling, and to consider their physiological consequences. This review then focuses on a potential candidate for maintaining axonal CB1R at the cell surface, Src homology 3-domain growth factor receptor-bound 2-like endophilin interacting protein 1 (SGIP1). SGIP1 may contribute to the polarized distribution of CB1R and modify its signaling in axons. In addition, deletion of SGIP1 results in discrete behavioral changes in modalities controlled by the endocannabinoid system in vivo. Several drugs acting directly via CB1R have important therapeutic potential, however their adverse effects limit their clinical use. Future studies might reveal chemical approaches to target the SGIP1-CB1R interaction, with the aim to exploit the endocannabinoid system pharmaceutically in a discrete way, with minimized undesired consequences.
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Affiliation(s)
- Oleh Durydivka
- Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, United States
| | - Jaroslav Blahos
- Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
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2
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Straiker A, Dvorakova M, Bosquez-Berger T, Blahos J, Mackie K. A collection of cannabinoid-related negative findings from autaptic hippocampal neurons. Sci Rep 2023; 13:9610. [PMID: 37311900 PMCID: PMC10264370 DOI: 10.1038/s41598-023-36710-3] [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: 10/13/2022] [Accepted: 06/08/2023] [Indexed: 06/15/2023] Open
Abstract
Autaptic hippocampal neurons are an architecturally simple model of neurotransmission that express several forms of cannabinoid signaling. Over the past twenty years this model has proven valuable for studies ranging from enzymatic control of endocannabinoid production and breakdown, to CB1 receptor structure/function, to CB2 signaling, understanding 'spice' (synthetic cannabinoid) pharmacology, and more. However, while studying cannabinoid signaling in these neurons, we have occasionally encountered what one might call 'interesting negatives', valid and informative findings in the context of our experimental design that, given the nature of scientific publishing, may not otherwise find their way into the scientific literature. In autaptic hippocampal neurons we have found that: (1) The fatty acid binding protein (FABP) blocker SBFI-26 does not alter CB1-mediated neuroplasticity. (2) 1-AG signals poorly relative to 2-AG in autaptic neurons. (3) Indomethacin is not a CB1 PAM in autaptic neurons. (4) The CB1-associated protein SGIP1a is not necessary for CB1 desensitization. We are presenting these negative or perplexing findings in the hope that they will prove beneficial to other laboratories and elicit fruitful discussions regarding their relevance and significance.
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Affiliation(s)
- Alex Straiker
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA.
| | - Michaela Dvorakova
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
| | - Taryn Bosquez-Berger
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
| | - Jaroslav Blahos
- Department of Molecular Pharmacology, Institute of Molecular Genetics of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague 4, Czech Republic
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Program in Neuroscience, Indiana University, Bloomington, IN, 47405, USA
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3
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Piscura MK, Sepulveda DE, Maulik M, Guindon J, Henderson-Redmond AN, Morgan DJ. Cannabinoid Tolerance in S426A/S430A x β-Arrestin 2 Knockout Double-Mutant Mice. J Pharmacol Exp Ther 2023; 385:17-34. [PMID: 36669876 PMCID: PMC10029824 DOI: 10.1124/jpet.122.001367] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 01/03/2023] [Accepted: 01/10/2023] [Indexed: 01/22/2023] Open
Abstract
Tolerance to compounds that target G protein-coupled receptors (GPCRs), such as the cannabinoid type-1 receptor (CB1R), is in part facilitated by receptor desensitization. Processes that mediate CB1R desensitization include phosphorylation of CB1R residues S426 and S430 by a GPCR kinase and subsequent recruitment of the β-arrestin2 scaffolding protein. Tolerance to cannabinoid drugs is reduced in S426A/S430A mutant mice and β-arrestin2 knockout (KO) mice according to previous work in vivo. However, the presence of additional phosphorylatable residues on the CB1R C-terminus made it unclear as to whether recruitment to S426 and S430 accounted for all desensitization and tolerance by β-arrestin2. Therefore, we assessed acute response and tolerance to the cannabinoids delta-9-tetrahydrocannabinol (Δ9-THC) and CP55,940 in S426A/S430A x β-arrestin2 KO double-mutant mice. We observed both delayed tolerance and increased sensitivity to the antinociceptive and hypothermic effects of CP55,940 in male S426A/S430A single- and double-mutant mice compared with wild-type littermates, but not with Δ9-THC. Female S426A/S430A single- and double-mutant mice were more sensitive to acute antinociception (CP55,940 and Δ9-THC) and hypothermia (CP55,940 only) exclusively after chronic dosing and did not differ in the development of tolerance. These results indicate that phosphorylation of S426 and S430 are likely responsible for β-arrestin2-mediated desensitization as double-mutant mice did not differ from the S426A/S430A single-mutant model in respect to cannabinoid tolerance and sensitivity. We also found antinociceptive and hypothermic effects from cannabinoid treatment demonstrated by sex-, agonist-, and duration-dependent features. SIGNIFICANCE STATEMENT: A better understanding of the molecular mechanisms involved in tolerance will improve the therapeutic potential of cannabinoid drugs. This study determined that further deletion of β-arrestin2 does not enhance the delay in cannabinoid tolerance observed in CB1R S426A/S430A mutant mice.
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Affiliation(s)
- Mary K Piscura
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Diana E Sepulveda
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Malabika Maulik
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Josée Guindon
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Angela N Henderson-Redmond
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Daniel J Morgan
- Department of Biomedical Sciences, Marshall University, Huntington, West Virginia (M.K.P., M.M., A.N.H.-R., D.J.M.); Department of Pharmacology (D.E.S.) and Graduate Program in Anatomy (M.K.P.), Penn State University College of Medicine, Hershey, Pennsylvania; and Department of Pharmacology and Neuroscience (J.G.) and Center of Excellence for Translational Neuroscience and Therapeutics (J.G.), Texas Tech University Health Sciences Center, Lubbock, Texas
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Manning JJ, Rawcliffe G, Finlay DB, Glass M. Cannabinoid 1 (CB 1 ) receptor arrestin subtype-selectivity and phosphorylation dependence. Br J Pharmacol 2023; 180:369-382. [PMID: 36250246 PMCID: PMC10100024 DOI: 10.1111/bph.15973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND AND PURPOSE Arrestin or G protein bias may be desirable for novel cannabinoid therapeutics. Arrestin-2 and arrestin-3 translocation to CB1 receptor have been suggested to mediate different functions that may be exploited with biased ligands. Here, the requirement of a recently described phosphorylation motif 'pxxp' (where 'p' denotes phosphorylatable serine or threonine and 'x' denotes any other amino acid) within the CB1 receptor C-terminus for interaction with different arrestin subtypes was examined. EXPERIMENTAL APPROACH Site-directed mutagenesis was conducted to generate nine different phosphorylation-impaired CB1 receptor C-terminal mutants. Bioluminescence resonance energy transfer (BRET) was employed to measure arrestin-2/3 translocation and G protein dissociation of a high efficacy agonist for each mutant. Immunocytochemistry was used to quantify receptor expression. KEY RESULTS The effects of each mutation were shared for arrestin-2 and arrestin-3 translocation to CB1 receptor pxxp motifs are partially required for arrestin-2/3 translocation, but translocation was not completely inhibited until all phosphorylation sites were mutated. The rate of arrestin translocation was reduced with simultaneous mutation of S425 and S429. Desensitisation of G protein dissociation was inhibited in different mutants proportional to the extent of their respective loss of arrestin translocation. CONCLUSIONS AND IMPLICATIONS These data do not support the existence of an 'essential' pxxp motif for arrestin translocation to CB1 receptor. These data also identify that arrestin-2 and arrestin-3 have equivalent phosphorylation requirements within the CB1 receptor C-terminus, suggesting arrestin subtype-selective biased ligands may not be viable and that different regions of the C-terminus contribute differently to arrestin translocation.
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Affiliation(s)
- Jamie J Manning
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Gabriel Rawcliffe
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - David B Finlay
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Michelle Glass
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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Saumell-Esnaola M, Elejaga-Jimeno A, Echeazarra L, Borrega-Román L, Barrondo S, López de Jesús M, González-Burguera I, Gómez-Caballero A, Goicolea MA, Sallés J, García del Caño G. Design and validation of recombinant protein standards for quantitative Western blot analysis of cannabinoid CB1 receptor density in cell membranes: an alternative to radioligand binding methods. Microb Cell Fact 2022; 21:192. [PMID: 36109736 PMCID: PMC9479267 DOI: 10.1186/s12934-022-01914-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/27/2022] [Indexed: 11/16/2022] Open
Abstract
Background Replacement of radioligand binding assays with antibody-antigen interaction-based approaches for quantitative analysis of G protein-coupled receptor (GPCR) levels requires the use of purified protein standards containing the antigen. GPCRs in general and cannabinoid CB1 receptor in particular show a progressive tendency to aggregate and precipitate in aqueous solution outside of their biological context due to the low solubility that the hydrophobic nature imprinted by their seven transmembrane domains. This renders full-length recombinant GPCRs useless for analytical purposes, a problem that can be overcome by engineering soluble recombinant fragments of the receptor containing the antigen. Results Here we generated highly soluble and stable recombinant protein constructs GST-CB1414–472 and GST-CB1414-442 containing much of the human CB1 receptor C-terminal tail for use as standard and negative control, respectively, in quantitative Western blot analysis of CB1 receptor expression on crude synaptosomes of the adult rat brain cortex. To this end we used three different antibodies, all raised against a peptide comprising the C-terminal residues 443–473 of the mouse CB1 receptor that corresponds to residues 442–472 in the human homolog. Estimated values of CB1 receptor density obtained by quantitative Western blot were of the same order of magnitude but slightly higher than values obtained by the radioligand saturation binding assay. Conclusions Collectively, here we provide a suitable Western blot-based design as a simple, cost-effective and radioactivity-free alternative for the quantitative analysis of CB1 receptor expression, and potentially of any GPCR, in a variety of biological samples. The discrepancies between the results obtained by quantitative Western blot and radioligand saturation binding techniques are discussed in the context of their particular theoretical bases and methodological constraints. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-022-01914-1.
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Gazdarica M, Noda J, Durydivka O, Novosadova V, Mackie K, Pin JP, Prezeau L, Blahos J. SGIP1 modulates kinetics and interactions of the cannabinoid receptor 1 and G protein-coupled receptor kinase 3 signalosome. J Neurochem 2021; 160:625-642. [PMID: 34970999 PMCID: PMC9306533 DOI: 10.1111/jnc.15569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 12/23/2021] [Accepted: 12/23/2021] [Indexed: 12/05/2022]
Abstract
Cannabinoid receptor 1 (CB1R), a G protein‐coupled receptor, plays a fundamental role in synaptic plasticity. Abnormal activity and deregulation of CB1R signaling result in a broad spectrum of pathological conditions. CB1R signaling is regulated by receptor desensitization including phosphorylation of residues within the intracellular C terminus by G protein‐coupled receptor kinases (GRKs) that may lead to endocytosis. Furthermore, CB1R signaling is regulated by the protein Src homology 3‐domain growth factor receptor‐bound 2‐like (SGIP1) that hinders receptor internalization, while enhancing CB1R association with β‐arrestin. It has been postulated that phosphorylation of two clusters of serine/threonine residues, 425SMGDS429 and 460TMSVSTDTS468, within the CB1R C‐tail controls dynamics of the association between receptor and its interaction partners involved in desensitization. Several molecular determinants of these events are still not well understood. We hypothesized that the dynamics of these interactions are modulated by SGIP1. Using a panel of CB1Rs mutated in the aforementioned serine and threonine residues, together with an array of Bioluminescence energy transfer‐based (BRET) sensors, we discovered that GRK3 forms complexes with Gβγ subunits of G proteins that largely independent of GRK3’s interaction with CB1R. Furthermore, CB1R interacts only with activated GRK3. Interestingly, phosphorylation of two specific residues on CB1R triggers GRK3 dissociation from the desensitized receptor. SGIP1 increases the association of GRK3 with Gβγ subunits of G proteins, and with CB1R. Altogether, our data suggest that the CB1R signalosome complex is dynamically controlled by sequential phosphorylation of the receptor C‐tail and is also modified by SGIP1.
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Affiliation(s)
- Matej Gazdarica
- Institute of Molecular Genetics, Czech Academy of Science, Videnska 1083, 14220, Prague 4, Czech Republic.,Institut de Génomique Fonctionnelle, Université Montpellier 1 and 2, Montpellier, France
| | - Judith Noda
- Institute of Molecular Genetics, Czech Academy of Science, Videnska 1083, 14220, Prague 4, Czech Republic
| | - Oleh Durydivka
- Institute of Molecular Genetics, Czech Academy of Science, Videnska 1083, 14220, Prague 4, Czech Republic
| | - Vendula Novosadova
- The Czech Center for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prumyslova 595, 252 50, Vestec, Czech Republic
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Molecular Bioscience, Indiana University, 1101 E. 10th St, Bloomington, IN, USA, 47405
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, Université Montpellier 1 and 2, Montpellier, France
| | - Laurent Prezeau
- Institut de Génomique Fonctionnelle, Université Montpellier 1 and 2, Montpellier, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Czech Academy of Science, Videnska 1083, 14220, Prague 4, Czech Republic
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Subsynaptic Distribution, Lipid Raft Targeting and G Protein-Dependent Signalling of the Type 1 Cannabinoid Receptor in Synaptosomes from the Mouse Hippocampus and Frontal Cortex. Molecules 2021; 26:molecules26226897. [PMID: 34833992 PMCID: PMC8621520 DOI: 10.3390/molecules26226897] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/05/2021] [Accepted: 11/11/2021] [Indexed: 11/16/2022] Open
Abstract
Numerous studies have investigated the roles of the type 1 cannabinoid receptor (CB1) in glutamatergic and GABAergic neurons. Here, we used the cell-type-specific CB1 rescue model in mice to gain insight into the organizational principles of plasma membrane targeting and Gαi/o protein signalling of the CB1 receptor at excitatory and inhibitory terminals of the frontal cortex and hippocampus. By applying biochemical fractionation techniques and Western blot analyses to synaptosomal membranes, we explored the subsynaptic distribution (pre-, post-, and extra-synaptic) and CB1 receptor compartmentalization into lipid and non-lipid raft plasma membrane microdomains and the signalling properties. These data infer that the plasma membrane partitioning of the CB1 receptor and its functional coupling to Gαi/o proteins are not biased towards the cell type of CB1 receptor rescue. The extent of the canonical Gαi/o protein-dependent CB1 receptor signalling correlated with the abundance of CB1 receptor in the respective cell type (glutamatergic versus GABAergic neurons) both in frontal cortical and hippocampal synaptosomes. In summary, our results provide an updated view of the functional coupling of the CB1 receptor to Gαi/o proteins at excitatory and inhibitory terminals and substantiate the utility of the CB1 rescue model in studying endocannabinoid physiology at the subcellular level.
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Fletcher-Jones A, Hildick KL, Evans AJ, Nakamura Y, Henley JM, Wilkinson KA. Protein Interactors and Trafficking Pathways That Regulate the Cannabinoid Type 1 Receptor (CB1R). Front Mol Neurosci 2020; 13:108. [PMID: 32595453 PMCID: PMC7304349 DOI: 10.3389/fnmol.2020.00108] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 05/20/2020] [Indexed: 12/29/2022] Open
Abstract
The endocannabinoid system (ECS) acts as a negative feedback mechanism to suppress synaptic transmission and plays a major role in a diverse range of brain functions including, for example, the regulation of mood, energy balance, and learning and memory. The function and dysfunction of the ECS are strongly implicated in multiple psychiatric, neurological, and neurodegenerative diseases. Cannabinoid type 1 receptor (CB1R) is the most abundant G protein-coupled receptor (GPCR) expressed in the brain and, as for any synaptic receptor, CB1R needs to be in the right place at the right time to respond appropriately to changing synaptic circumstances. While CB1R is found intracellularly throughout neurons, its surface expression is highly polarized to the axonal membrane, consistent with its functional expression at presynaptic sites. Surprisingly, despite the importance of CB1R, the interacting proteins and molecular mechanisms that regulate the highly polarized distribution and function of CB1R remain relatively poorly understood. Here we set out what is currently known about the trafficking pathways and protein interactions that underpin the surface expression and axonal polarity of CB1R, and highlight key questions that still need to be addressed.
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Affiliation(s)
- Alexandra Fletcher-Jones
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Keri L Hildick
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Ashley J Evans
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Yasuko Nakamura
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Jeremy M Henley
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Kevin A Wilkinson
- Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol, United Kingdom
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Al-Zoubi R, Morales P, Reggio PH. Structural Insights into CB1 Receptor Biased Signaling. Int J Mol Sci 2019; 20:E1837. [PMID: 31013934 PMCID: PMC6515405 DOI: 10.3390/ijms20081837] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/09/2019] [Accepted: 04/11/2019] [Indexed: 12/21/2022] Open
Abstract
The endocannabinoid system has emerged as a promising target for the treatment of numerous diseases, including cancer, neurodegenerative disorders, and metabolic syndromes. Thus far, two cannabinoid receptors, CB1 and CB2, have been discovered, which are found predominantly in the central nervous system (CB1) or the immune system (CB2), among other organs and tissues. CB1 receptor ligands have been shown to induce a complex pattern of intracellular effects. The binding of a ligand induces distinct conformational changes in the receptor, which will eventually translate into distinct intracellular signaling pathways through coupling to specific intracellular effector proteins. These proteins can mediate receptor desensitization, trafficking, or signaling. Ligand specificity and selectivity, complex cellular components, and the concomitant expression of other proteins (which either regulate the CB1 receptor or are regulated by the CB1 receptor) will affect the therapeutic outcome of its targeting. With an increased interest in G protein-coupled receptors (GPCR) research, in-depth studies using mutations, biological assays, and spectroscopic techniques (such as NMR, EPR, MS, FRET, and X-ray crystallography), as well as computational modelling, have begun to reveal a set of concerted structural features in Class A GPCRs which relate to signaling pathways and the mechanisms of ligand-induced activation, deactivation, or activity modulation. This review will focus on the structural features of the CB1 receptor, mutations known to bias its signaling, and reported studies of CB1 receptor ligands to control its specific signaling.
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Affiliation(s)
- Rufaida Al-Zoubi
- Department of Medicinal Chemistry and Pharmacognosy, Faculty of Pharmacy, Jordan University of Science & Technology, P.O.BOX 3030, Irbid 22110, Jordan.
| | - Paula Morales
- Departamento de Química-Física Biológica, Instituto de Química Física Rocasolano (IQFR-CSIC), Serrano 119, 28006 Madrid, Spain.
| | - Patricia H Reggio
- Chemistry and Biochemistry Department, UNC Greensboro, Greensboro, NC 27412, USA.
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Mascia F, Klotz L, Lerch J, Ahmed MH, Zhang Y, Enz R. CRIP1a inhibits endocytosis of G-protein coupled receptors activated by endocannabinoids and glutamate by a common molecular mechanism. J Neurochem 2017; 141:577-591. [PMID: 28295323 DOI: 10.1111/jnc.14021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 02/17/2017] [Accepted: 03/10/2017] [Indexed: 01/20/2023]
Abstract
The excitability of the central nervous system depends largely on the surface density of neurotransmitter receptors. The endocannabinoid receptor 1 (CB1 R) and the metabotropic glutamate receptor mGlu8 R are expressed pre-synaptically where they reduce glutamate release into the synaptic cleft. Recently, the CB1 R interacting protein cannabinoid receptor interacting protein 1a (CRIP1a) was identified and characterized to regulate CB1 R activity in neurons. However, underlying molecular mechanisms are largely unknown. Here, we identified a common mechanism used by CRIP1a to regulate the cell surface density of two different types of G-protein coupled receptors, CB1 R and mGlu8a R. Five amino acids within the CB1 R C-terminus were required and sufficient to reduce constitutive CB1 R endocytosis by about 72% in the presence of CRIP1a. Interestingly, a similar sequence is present in mGlu8a R and consistently, endocytosis of mGlu8a R depended on CRIP1a, as well. Docking analysis and molecular dynamics simulations identified a conserved serine in CB1 R (S468) and mGlu8a R (S894) that forms a hydrogen bond with the peptide backbone of CRIP1a at position R82. In contrast to mGlu8a R, the closely related mGlu8b R splice-variant carries a lysine (K894) at this position, and indeed, mGlu8b R endocytosis was not affected by CRIP1a. Chimeric constructs between CB1 R, mGlu8a R, and mGlu8b R underline the role of the identified five CRIP1a sensitive amino acids. In summary, we suggest that CRIP1a negatively regulates endocytosis of two different G-protein coupled receptor types, CB1 R and mGlu8a R.
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Affiliation(s)
- Fabrizio Mascia
- Institut für Biochemie (Emil-Fischer-Zentrum), Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Lisa Klotz
- Institut für Biochemie (Emil-Fischer-Zentrum), Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Judith Lerch
- Institut für Biochemie (Emil-Fischer-Zentrum), Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Mostafa H Ahmed
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Yan Zhang
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ralf Enz
- Institut für Biochemie (Emil-Fischer-Zentrum), Universität Erlangen-Nürnberg, Erlangen, Germany
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Zugaib J, Leão RM. Inhibitors of oxidative and hydrolytic endocannabinoid degradation do not enhance depolarization-induced suppression of excitation on dorsal cochlear nucleus glycinergic neurons. Synapse 2017; 71. [DOI: 10.1002/syn.21954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 12/07/2016] [Accepted: 12/07/2016] [Indexed: 12/27/2022]
Affiliation(s)
- João Zugaib
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto, São Paulo Brazil
- Research Group on the Dynamics of the Neuromusculoskeletal System, Bahiana School of Medicine and Public Health; Salvador Bahia Brazil
| | - Ricardo M. Leão
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto, São Paulo Brazil
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12
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Hájková A, Techlovská Š, Dvořáková M, Chambers JN, Kumpošt J, Hubálková P, Prezeau L, Blahos J. SGIP1 alters internalization and modulates signaling of activated cannabinoid receptor 1 in a biased manner. Neuropharmacology 2016; 107:201-214. [PMID: 26970018 DOI: 10.1016/j.neuropharm.2016.03.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 02/24/2016] [Accepted: 03/04/2016] [Indexed: 02/07/2023]
Abstract
Many diseases of the nervous system are accompanied by alterations in synaptic functions. Synaptic plasticity mediated by the endogenous cannabinoid system involves the activation of the cannabinoid receptor 1 (CB1R). The principles of CB1R signaling must be understood in detail for its therapeutic exploration. We detected the Src homology 3-domain growth factor receptor-bound 2-like (endophilin) interacting protein 1 (SGIP1) as a novel CB1R partner. SGIP1 is functionally linked to clathrin-mediated endocytosis and its overexpression in animals leads to an energy regulation imbalance resulting in obesity. We report that SGIP1 prevents the endocytosis of activated CB1R and that it alters signaling via the CB1R in a biased manner. CB1R mediated G-protein activation is selectively influenced by SGIP1, β-arrestin associated signaling is changed profoundly, most likely as a consequence of the prevention of the receptor's internalization elicited by SGIP1.
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Affiliation(s)
- Alena Hájková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Šárka Techlovská
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Michaela Dvořáková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Jayne Nicole Chambers
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Jiří Kumpošt
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Pavla Hubálková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Laurent Prezeau
- Institut de Génomique Fonctionnelle, University of Montpellier 1 and 2, Montpellier, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic.
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13
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Trautmann SM, Sharkey KA. The Endocannabinoid System and Its Role in Regulating the Intrinsic Neural Circuitry of the Gastrointestinal Tract. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 125:85-126. [PMID: 26638765 DOI: 10.1016/bs.irn.2015.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Endocannabinoids are important neuromodulators in the central nervous system. They regulate central transmission through pre- and postsynaptic actions on neurons and indirectly through effects on glial cells. Cannabinoids (CBs) also regulate neurotransmission in the enteric nervous system (ENS) of the gastrointestinal (GI) tract. The ENS consists of intrinsic primary afferent neurons, interneurons, and motor neurons arranged in two ganglionated plexuses which control all the functions of the gut. Increasing evidence suggests that endocannabinoids are potent neuromodulators in the ENS. In this review, we will highlight key observations on the localization of CB receptors and molecules involved in the synthesis and degradation of endocannabinoids in the ENS. We will discuss endocannabinoid signaling mechanisms, endocannabinoid tone and concepts of CB receptor metaplasticity in the ENS. We will also touch on some examples of enteric neural signaling in relation neuromuscular, secretomotor, and enteroendocrine transmission in the ENS. Finally, we will briefly discuss some key future directions.
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Affiliation(s)
- Samantha M Trautmann
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Keith A Sharkey
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
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14
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Guggenhuber S, Alpar A, Chen R, Schmitz N, Wickert M, Mattheus T, Harasta AE, Purrio M, Kaiser N, Elphick MR, Monory K, Kilb W, Luhmann HJ, Harkany T, Lutz B, Klugmann M. Cannabinoid receptor-interacting protein Crip1a modulates CB1 receptor signaling in mouse hippocampus. Brain Struct Funct 2015; 221:2061-74. [PMID: 25772509 DOI: 10.1007/s00429-015-1027-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 03/06/2015] [Indexed: 12/13/2022]
Abstract
The cannabinoid type 1 receptor (Cnr1, CB1R) mediates a plethora of physiological functions in the central nervous system as a presynaptic modulator of neurotransmitter release. The recently identified cannabinoid receptor-interacting protein 1a (Cnrip1a, CRIP1a) binds to the C-terminal domain of CB1R, a region known to be important for receptor desensitization and internalization. Evidence that CRIP1a and CB1R interact in vivo has been reported, but the neuroanatomical distribution of CRIP1a is unknown. Moreover, while alterations of hippocampal CRIP1a levels following limbic seizures indicate a role in controlling excessive neuronal activity, the physiological function of CRIP1a in vivo has not been investigated. In this study, we analyzed the spatial distribution of CRIP1a in the hippocampus and examined CRIP1a as a potential modulator of CB1R signaling. We found that Cnrip1a mRNA is co-expressed with Cnr1 mRNA in pyramidal neurons and interneurons of the hippocampal formation. CRIP1a protein profiles were largely segregated from CB1R profiles in mossy cell terminals but not in hippocampal CA1 region. CB1R activation induced relocalization to close proximity with CRIP1a. Adeno-associated virus-mediated overexpression of CRIP1a specifically in the hippocampus revealed that CRIP1a modulates CB1R activity by enhancing cannabinoid-induced G protein activation. CRIP1a overexpression extended the depression of excitatory currents by cannabinoids in pyramidal neurons of the hippocampus and diminished the severity of chemically induced acute epileptiform seizures. Collectively, our data indicate that CRIP1a enhances hippocampal CB1R signaling in vivo.
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Affiliation(s)
- Stephan Guggenhuber
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Alan Alpar
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 1:A1, 17177, Stockholm, Sweden
- Research Group of Experimental Neuroanatomy and Developmental Biology, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Rongqing Chen
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Nina Schmitz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Melanie Wickert
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Tobias Mattheus
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Anne E Harasta
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, UNSW, High Street, Randwick, Sydney, NSW, 2052, Australia
| | - Martin Purrio
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Nadine Kaiser
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Maurice R Elphick
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Krisztina Monory
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany
| | - Tibor Harkany
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 1:A1, 17177, Stockholm, Sweden
- Department of Molecular Neuroscience, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany.
| | - Matthias Klugmann
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, 55128, Mainz, Germany.
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, UNSW, High Street, Randwick, Sydney, NSW, 2052, Australia.
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15
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Keenan CM, Storr MA, Thakur GA, Wood JT, Wager-Miller J, Straiker A, Eno MR, Nikas SP, Bashashati M, Hu H, Mackie K, Makriyannis A, Sharkey KA. AM841, a covalent cannabinoid ligand, powerfully slows gastrointestinal motility in normal and stressed mice in a peripherally restricted manner. Br J Pharmacol 2015; 172:2406-18. [PMID: 25572435 DOI: 10.1111/bph.13069] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 12/19/2014] [Accepted: 01/02/2015] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Cannabinoid (CB) ligands have been demonstrated to have utility as novel therapeutic agents for the treatment of pain, metabolic conditions and gastrointestinal (GI) disorders. However, many of these ligands are centrally active, which limits their usefulness. Here, we examine a unique novel covalent CB receptor ligand, AM841, to assess its potential for use in physiological and pathophysiological in vivo studies. EXPERIMENTAL APPROACH The covalent nature of AM841 was determined in vitro using electrophysiological and receptor internalization studies on isolated cultured hippocampal neurons. Mouse models were used for behavioural analysis of analgesia, hypothermia and hypolocomotion. The motility of the small and large intestine was assessed in vivo under normal conditions and after acute stress. The brain penetration of AM841 was also determined. KEY RESULTS AM841 behaved as an irreversible CB1 receptor agonist in vitro. AM841 potently reduced GI motility through an action on CB1 receptors in the small and large intestine under physiological conditions. AM841 was even more potent under conditions of acute stress and was shown to normalize accelerated GI motility under these conditions. This compound behaved as a peripherally restricted ligand, showing very little brain penetration and no characteristic centrally mediated CB1 receptor-mediated effects (analgesia, hypothermia or hypolocomotion). CONCLUSIONS AND IMPLICATIONS AM841, a novel peripherally restricted covalent CB1 receptor ligand that was shown to be remarkably potent, represents a new class of potential therapeutic agents for the treatment of functional GI disorders.
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Affiliation(s)
- C M Keenan
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Alberta, Canada; Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Alberta, Canada
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16
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Ligand-specific endocytic dwell times control functional selectivity of the cannabinoid receptor 1. Nat Commun 2014; 5:4589. [PMID: 25081814 PMCID: PMC4227836 DOI: 10.1038/ncomms5589] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 07/03/2014] [Indexed: 12/20/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are the major transducers of external stimuli and
key therapeutic targets in many pathological conditions. When activated by different
ligands, one receptor can elicit multiple signalling cascades that are mediated by G
proteins or β-arrestin, a process defined as functional selectivity or
ligand bias. However, the dynamic mechanisms underlying β-arrestin
signalling remain unknown. Here by studying the cannabinoid receptor 1 (CB1R), we identify ligand-specific endocytic dwell times, that
is, the time during which receptors are clustered into clathrin pits together with
β-arrestins before endocytosis, as the mechanism controlling
β-arrestin signalling. Agonists inducing short endocytic dwell times
produce little or no β-arrestin signalling, whereas those eliciting
prolonged dwell times induce robust signalling. Remarkably, extending CB1R dwell times by preventing endocytosis
substantially increased β-arrestin signalling. These studies reveal how
receptor activation translates into β-arrestin signalling and identify a
mechanism to control this pathway. G-protein coupled receptors can signal through G-proteins or through
β-arrestin, however mechanisms determining pathway selection remain unclear.
Here the authors show that the duration of cannabinoid receptor clustering in clathrin
coated pits prior to endocytosis determines the strength of β-arrestin
signalling.
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17
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Mutation of putative GRK phosphorylation sites in the cannabinoid receptor 1 (CB1R) confers resistance to cannabinoid tolerance and hypersensitivity to cannabinoids in mice. J Neurosci 2014; 34:5152-63. [PMID: 24719095 DOI: 10.1523/jneurosci.3445-12.2014] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
For many G-protein-coupled receptors (GPCRs), including cannabinoid receptor 1 (CB1R), desensitization has been proposed as a principal mechanism driving initial tolerance to agonists. GPCR desensitization typically requires phosphorylation by a G-protein-coupled receptor kinase (GRK) and interaction of the phosphorylated receptor with an arrestin. In simple model systems, CB1R is desensitized by GRK phosphorylation at two serine residues (S426 and S430). However, the role of these serine residues in tolerance and dependence for cannabinoids in vivo was unclear. Therefore, we generated mice where S426 and S430 were mutated to nonphosphorylatable alanines (S426A/S430A). S426A/S430A mutant mice were more sensitive to acutely administered delta-9-tetrahydrocannabinol (Δ(9)-THC), have delayed tolerance to Δ(9)-THC, and showed increased dependence for Δ(9)-THC. S426A/S430A mutants also showed increased responses to elevated levels of endogenous cannabinoids. CB1R desensitization in the periaqueductal gray and spinal cord following 7 d of treatment with Δ(9)-THC was absent in S426A/S430A mutants. Δ(9)-THC-induced downregulation of CB1R in the spinal cord was also absent in S426A/S430A mutants. Cultured autaptic hippocampal neurons from S426A/S430A mice showed enhanced endocannabinoid-mediated depolarization-induced suppression of excitation (DSE) and reduced agonist-mediated desensitization of DSE. These results indicate that S426 and S430 play major roles in the acute response to, tolerance to, and dependence on cannabinoids. Additionally, S426A/S430A mice are a novel model for studying pathophysiological processes thought to involve excessive endocannabinoid signaling such as drug addiction and metabolic disease. These mice also validate the approach of mutating GRK phosphorylation sites involved in desensitization as a general means to confer exaggerated signaling to GPCRs in vivo.
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18
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Marcu J, Shore DM, Kapur A, Trznadel M, Makriyannis A, Reggio PH, Abood ME. Novel insights into CB1 cannabinoid receptor signaling: a key interaction identified between the extracellular-3 loop and transmembrane helix 2. J Pharmacol Exp Ther 2013; 345:189-97. [PMID: 23426954 DOI: 10.1124/jpet.112.201046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of the cannabinoid CB1 receptor (CB1) is modulated by aspartate residue D2.63(176) in transmembrane helix (TMH) 2. Interestingly, D2.63 does not affect the affinity for ligand binding at the CB1 receptor. Studies in class A G protein-coupled receptors have suggested an ionic interaction between residues of TMH2 and 7. In this report, modeling studies identified residue K373 in the extracellular-3 (EC-3) loop in charged interactions with D2.63. We investigated this possibility by performing reciprocal mutations and biochemical studies. D2.63(176)A, K373A, D2.63(176)A-K373A, and the reciprocal mutant with the interacting residues juxtaposed D2.63(176)K-K373D were characterized using radioligand binding and guanosine 5'-3-O-(thio)triphosphate functional assays. None of the mutations resulted in a significant change in the binding affinity of N-(piperidiny-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride (SR141716A) or (-)-3cis -[2-hydroxyl-4-(1,1-dimethyl-heptyl)phenyl]-trans-4-[3-hydroxyl-propyl] cyclohexan-1-ol (CP55,940). Modeling studies indicated that binding-site interactions and energies of interaction for CP55,940 were similar between wild-type and mutant receptors. However, the signaling of CP55,940, and (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]-pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthalenyl)-methanone mesylate (WIN55,212-2) was impaired at the D2.63(176)A-K373A and the single-alanine mutants. In contrast, the reciprocal D2.63(176)K-K373D mutant regained function for both CP55,940 and WIN55,212-2. Computational results indicate that the D2.63(176)-K373 ionic interaction strongly influences the conformation(s) of the EC-3 loop, providing a structure-based rationale for the importance of the EC-3 loop to signal transduction in CB1. The putative ionic interaction results in the EC-3 loop pulling over the top (extracellular side) of the receptor; this EC-3 loop conformation may serve protective and mechanistic roles. These results suggest that the ionic interaction between D2.63(176) and K373 is important for CB1 signal transduction.
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Affiliation(s)
- Jahan Marcu
- Department of Anatomy and Cell Biology, Center for Substance Abuse Research, Temple University, Philadelphia, PA 19140, USA
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19
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Hu H, Ho W, Mackie K, Pittman QJ, Sharkey KA. Brain CB₁ receptor expression following lipopolysaccharide-induced inflammation. Neuroscience 2012; 227:211-22. [PMID: 23041513 PMCID: PMC3505253 DOI: 10.1016/j.neuroscience.2012.09.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 09/25/2012] [Accepted: 09/26/2012] [Indexed: 01/11/2023]
Abstract
Cannabinoid 1 receptors (CB(1)) are highly expressed on presynaptic terminals in the brain where they are importantly involved in the control of neurotransmitter release. Alteration of CB(1) expression is associated with a variety of neurological and psychiatric disorders. There is now compelling evidence that peripheral inflammatory disorders are associated with depression and cognitive impairments. These can be modeled in rodents with peripheral administration of lipopolysaccharide (LPS), but central effects of this treatment remain to be fully elucidated. As a reduction in endocannabinoid tone is thought to contribute to depression, we asked whether the expression of CB(1) in the CNS is altered following LPS treatment. CD1 mice received LPS (0.1-1mg/kg, ip) and 6h later activated microglial cells were observed only in circumventricular organs and only at the higher dose. At 24h, activated microglial cells were identified in other brain regions, including the hippocampus, a structure implicated in some mood disorders. Immunohistochemistry and real-time polymerase chain reaction (PCR) were utilized to evaluate the change of CB(1) expression 24h after inflammation. LPS induced an increase of CB(1) mRNA in the hippocampus and brainstem. Subsequent immunohistochemical analysis revealed reduced CB(1) in the hippocampus, especially in CA3 pyramidal layer. Analysis of co-localization with markers of excitatory and inhibitory terminals indicated that the decrease in CB(1) expression was restricted to glutamatergic terminals. Despite widespread microglial activation, these results suggest that peripheral LPS treatment leads to limited changes in CB(1) expression in the brain.
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MESH Headings
- Animals
- Brain/drug effects
- Brain/metabolism
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/genetics
- Glutamate Decarboxylase/metabolism
- Inflammation/chemically induced
- Inflammation/pathology
- Lipopolysaccharides/toxicity
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- RNA, Messenger/metabolism
- Receptor, Cannabinoid, CB1/deficiency
- Receptor, Cannabinoid, CB1/genetics
- Receptor, Cannabinoid, CB1/metabolism
- Time Factors
- Vesicular Glutamate Transport Protein 1/metabolism
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Affiliation(s)
- Huangming Hu
- Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Winnie Ho
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana 47405,USA
| | - Quentin J. Pittman
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Keith A. Sharkey
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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20
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Atwood BK, Straiker A, Mackie K. CB₂ cannabinoid receptors inhibit synaptic transmission when expressed in cultured autaptic neurons. Neuropharmacology 2012; 63:514-23. [PMID: 22579668 DOI: 10.1016/j.neuropharm.2012.04.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/18/2012] [Accepted: 04/23/2012] [Indexed: 11/18/2022]
Abstract
The role of CB₂ in the central nervous system, particularly in neurons, has generated much controversy. Fueling the controversy are imperfect tools, which have made conclusive identification of CB₂ expressing neurons problematic. Imprecise localization of CB₂ has made it difficult to determine its function in neurons. Here we avoid the localization controversy and directly address the question if CB₂ can modulate neurotransmission. CB₂ was expressed in excitatory hippocampal autaptic neurons obtained from CB₁ null mice. Whole-cell patch clamp recordings were made from these neurons to determine the effects of CB₂ on short-term synaptic plasticity. CB₂ expression restored depolarization induced suppression of excitation to these neurons, which was lost following genetic ablation of CB₁. The endocannabinoid 2-arachidonylglycerol (2-AG) mimicked the effects of depolarization in CB₂ expressing neurons. Interestingly, ongoing basal production of 2-AG resulted in constitutive activation of CB₂, causing a tonic inhibition of neurotransmission that was relieved by the CB₂ antagonist AM630 or the diacylglycerol lipase inhibitor RHC80267. Through immunocytochemistry and analysis of spontaneous EPSCs, paired pulse ratios and coefficients of variation we determined that CB₂ exerts its function at a presynaptic site of action, likely through inhibition of voltage gated calcium channels. Therefore CB₂ expressed in neurons effectively mimics the actions of CB₁. Thus neuronal CB₂ is well suited to integrate into conventional neuronal endocannabinoid signaling processes, with its specific role determined by its unique and highly inducible expression profile.
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MESH Headings
- Animals
- Animals, Newborn
- Arachidonic Acids/antagonists & inhibitors
- Arachidonic Acids/metabolism
- Arachidonic Acids/pharmacology
- Astrocytes/cytology
- Cells, Cultured
- Endocannabinoids/antagonists & inhibitors
- Endocannabinoids/metabolism
- Endocannabinoids/pharmacology
- Enzyme Inhibitors/pharmacology
- Glycerides/antagonists & inhibitors
- Glycerides/metabolism
- Glycerides/pharmacology
- Heterozygote
- Hippocampus/cytology
- Hippocampus/drug effects
- Hippocampus/metabolism
- Lipoprotein Lipase/antagonists & inhibitors
- Mice
- Mice, Knockout
- Nerve Tissue Proteins/agonists
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neurons/cytology
- Neurons/drug effects
- Neurons/metabolism
- Patch-Clamp Techniques
- Presynaptic Terminals/drug effects
- Presynaptic Terminals/metabolism
- Receptor, Cannabinoid, CB1/genetics
- Receptor, Cannabinoid, CB1/metabolism
- Receptor, Cannabinoid, CB2/agonists
- Receptor, Cannabinoid, CB2/antagonists & inhibitors
- Receptor, Cannabinoid, CB2/genetics
- Receptor, Cannabinoid, CB2/metabolism
- Recombinant Fusion Proteins/metabolism
- Synaptic Transmission/drug effects
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Affiliation(s)
- Brady K Atwood
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, 1101 E. 10th Street, Bloomington, IN 47405, USA.
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