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Murali S, Aradhyam GK. Structure-function relationship and physiological role of apelin and its G protein coupled receptor. Biophys Rev 2023; 15:127-143. [PMID: 36919024 PMCID: PMC9995629 DOI: 10.1007/s12551-023-01044-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2023] [Indexed: 02/19/2023] Open
Abstract
Apelin receptor (APJR) is a class A peptide (apelin) binding G protein-coupled receptor (GPCR) that plays a significant role in regulating blood pressure, cardiac output, and maintenance of fluid homeostasis. It is activated by a wide range of endogenous peptide isoforms of apelin and elabela. The apelin peptide isoforms contain distinct structural features that aid in ligand recognition and activation of the receptor. Site-directed mutagenesis and structure-based studies have revealed the involvement of extracellular and transmembrane regions of the receptor in binding to the peptide isoforms. The structural features of APJR activation of the receptor as well as mediating G-protein and β-arrestin-mediated signaling are delineated by multiple mutagenesis studies. There is increasing evidence that the structural requirements of APJR to activate G-proteins and β-arrestins are different, leading to biased signaling. APJR also responds to mechanical stimuli in a ligand-independent manner. A multitude of studies has focused on developing both peptide and non-peptide agonists and antagonists specific to APJR. Apelin/elabela-activated APJR orchestrates major signaling pathways such as extracellular signal-regulated kinase (ERKs), protein kinase B (PKB/Akt), and p70S. This review focuses on the structural and functional characteristics of apelin, elabela, APJR, and their interactions involved in the binding and activation of the downstream signaling cascade. We also focus on the diverse signaling profile of APJR and its ligands and their involvement in various physiological systems.
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Affiliation(s)
- Subhashree Murali
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biological Sciences, Indian Institute of Technology Madras, Chennai, India
| | - Gopala Krishna Aradhyam
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biological Sciences, Indian Institute of Technology Madras, Chennai, India
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2
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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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3
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Ghosh S, de March CA, Branciamore S, Kaleem S, Matsunami H, Vaidehi N. Sequence coevolution and structure stabilization modulate olfactory receptor expression. Biophys J 2022; 121:830-840. [PMID: 35065915 PMCID: PMC8947990 DOI: 10.1016/j.bpj.2022.01.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 12/14/2021] [Accepted: 01/19/2022] [Indexed: 11/29/2022] Open
Abstract
Olfactory receptors (ORs) belong to class A G-protein coupled receptors (GPCRs) and are activated by a variety of odorants. To date, there is no three-dimensional structure of an OR available. One of the major bottlenecks in obtaining purified protein for structural studies of ORs is their poor expression in heterologous cells. To design mutants that enhance expression and thereby enable protein purification, we first identified computable physical properties that recapitulate OR and class A GPCR expression and further conducted an iterative computational prediction-experimental test cycle and generated human OR mutants that express as high as biogenic amine receptors for which structures have been solved. In the process of developing the computational method to recapitulate the expression of ORs in membranes, we identified properties, such as amino acid sequence coevolution, and the strength of the interactions between intracellular loop 1 (ICL1) and the helix 8 region of ORs, to enhance their heterologous expression. We identified mutations that are directly located in these regions as well as other mutations not located in these regions but allosterically strengthen the ICL1-helix 8 enhance expression. These mutants also showed functional responses to known odorants. This method to enhance heterologous expression of mammalian ORs will facilitate high-throughput "deorphanization" of ORs, and enable OR purification for biochemical and structural studies to understand odorant-OR interactions.
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Affiliation(s)
- Soumadwip Ghosh
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA
| | - Claire A. de March
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA
| | - Sergio Branciamore
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA
| | - Sahar Kaleem
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA
| | - Hiroaki Matsunami
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA; Department of Neurobiology, Duke Institute for Brain Sciences, Duke University School of Medicine, Durham, NC, USA.
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA.
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Haspula D, Clark MA. Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases. Int J Mol Sci 2020; 21:E7693. [PMID: 33080916 PMCID: PMC7590033 DOI: 10.3390/ijms21207693] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 12/16/2022] Open
Abstract
The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.
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Affiliation(s)
- Dhanush Haspula
- Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA;
| | - Michelle A. Clark
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL 33314, USA
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5
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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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6
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Singh P, Ganjiwale A, Howlett AC, Cowsik SM. Molecular Interaction between Distal C-Terminal Domain of the CB 1 Cannabinoid Receptor and Cannabinoid Receptor Interacting Proteins (CRIP1a/CRIP1b). J Chem Inf Model 2019; 59:5294-5303. [PMID: 31769975 DOI: 10.1021/acs.jcim.9b00948] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have investigated the structure of the distal C-terminal domain of the of the CB1 cannabinoid receptor (CB1R) to study its interactions with CRIP1a and CRIP1b using computational techniques. The amino acid sequence from the distal C-terminal domain of CB1R (G417-L472) was found to be unique, as it does not share sequence similarity with other protein structures, so the structure was predicted using ab initio modeling. The computed model of the distal C-terminal region of CB1R has a helical region between positions 441 and 455. The CRIP1a and CRIP1b were modeled using Rho-GDI 2 as a template. The three-dimensional model of the distal C-terminal domain of the CB1R was docked with both CRIP1a as well as CRIP1b to study the crucial interactions between CB1R and CRIP1a/b. The last nine residues of CB1R (S464TDTSAEAL4722) are known to be a CRIP1a/b binding site. The majority of the key interactions were identified in this region, but notable interactions were also observed beyond theses nine residues. The multiple interactions between Thr418 (CB1R) and Asn61 (CRIP1a) as well as Asp430 (CB1R) and Lys76 (CRIP1a) indicate their importance in the CB1R-CRIP1a interaction. In the case of CRIP1b, multiple hydrogen bond interactions between Asn437 (CB1R) and Glu77 (CRIP1b) were observed. These interactions can be critical for CB1R's interaction with CRIP1a/b, and targeting them for further experimental studies can advance information about CRIP1a/b functionality.
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Affiliation(s)
- Pratishtha Singh
- School of Life Sciences , Jawaharlal Nehru University , New Delhi - 110067 , India
| | - Anjali Ganjiwale
- Department of Life Sciences , Bangalore University , Bangalore - 560056 , India
| | - Allyn C Howlett
- Department of Physiology and Pharmacology , Wake Forest School of Medicine , Winston-Salem , North Carolina 27157 , United States
| | - Sudha M Cowsik
- School of Life Sciences , Jawaharlal Nehru University , New Delhi - 110067 , India
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7
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Pandey A, LeBlanc DM, Parmar HB, Phạm TTT, Sarker M, Xu L, Duncan R, Liu XQ, Rainey JK. Structure, amphipathy, and topology of the membrane-proximal helix 8 influence apelin receptor plasma membrane localization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183036. [PMID: 31394100 DOI: 10.1016/j.bbamem.2019.183036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 07/08/2019] [Accepted: 08/02/2019] [Indexed: 12/11/2022]
Abstract
G-protein coupled receptors (GPCRs) typically have an amphipathic helix ("helix 8") immediately C-terminal to the transmembrane helical bundle. To date, a number of functional roles have been associated with GPCR helix 8 segments, but structure-function analysis for this region remains limited. Here, we examine helix 8 of the apelin receptor (AR or APJ), a class A GPCR with wide physiological and pathophysiological relevance. The 71 residue C-terminal tail of the AR is primarily intrinsically disordered, with a detergent micelle-induced increase in helical character. This helicity was localized to the helix 8 region, in good agreement with the recent AR crystal structure. A series of helix 8 mutants were made to reduce helicity, remove amphipathy, or flip the hydrophobic and hydrophilic faces. Each mutant AR was tested both biophysically, in the isolated C-terminal tail, and functionally in HEK 293 T cells, for full-length AR. In all instances, micelle interactions were maintained, and steady-state AR expression was efficient. However, removal of amphipathy or helical character led to a significant decrease in cell surface localization. Flipping of helix 8 amphipathic topology restored cell surface localization to some degree, but still was significantly reduced relative to wild-type. Structural integrity, amphipathy to drive membrane association, and correct topology of helix 8 membrane association all thus appear important for cell surface localization of the AR. This behavior correlates well to GPCR C-terminal tail sequence motifs, implying that these serve to specify key topological features of helix 8 and its proximity to the transmembrane domain.
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Affiliation(s)
- Aditya Pandey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Danielle M LeBlanc
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Hirendrasinh B Parmar
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Trần Thanh Tâm Phạm
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Muzaddid Sarker
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Lingling Xu
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Roy Duncan
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Xiang-Qin Liu
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Jan K Rainey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
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8
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Cannabidiol binding and negative allosteric modulation at the cannabinoid type 1 receptor in the presence of delta-9-tetrahydrocannabinol: An In Silico study. PLoS One 2019; 14:e0220025. [PMID: 31335889 PMCID: PMC6650144 DOI: 10.1371/journal.pone.0220025] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 07/08/2019] [Indexed: 02/02/2023] Open
Abstract
Recent evidence has raised in discussion the possibility that cannabidiol can act as a negative allosteric modulator of the cannabinoid type 1 receptor. Here we have used computational methods to study the modulation exerted by cannabidiol on the effects of delta-9-tetrahydrocannabinol in the cannabinoid receptor type 1 and the possibility of direct receptor blockade. We propose a putative allosteric binding site that is located in the N-terminal region of receptor, partially overlapping the orthosteric binding site. Molecular dynamics simulations reveled a coordinated movement involving the outward rotation of helixes 1 and 2 and subsequent expansion of the orthosteric binding site upon cannabidiol binding. Finally, changes in the cytoplasmic region and high helix 8 mobility were related to impaired receptor internalization. Together, these results offer a possible explanation to how cannabidiol can directly modulate effects of delta-9-tetrahydrocannabinol on the cannabinoid receptor type 1.
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9
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Fletcher-Jones A, Hildick KL, Evans AJ, Nakamura Y, Wilkinson KA, Henley JM. The C-terminal helix 9 motif in rat cannabinoid receptor type 1 regulates axonal trafficking and surface expression. eLife 2019; 8:44252. [PMID: 31036155 PMCID: PMC6491034 DOI: 10.7554/elife.44252] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/29/2019] [Indexed: 12/20/2022] Open
Abstract
Cannabinoid type one receptor (CB1R) is only stably surface expressed in axons, where it downregulates neurotransmitter release. How this tightly regulated axonal surface polarity is established and maintained is unclear. To address this question, we used time-resolved imaging to determine the trafficking of CB1R from biosynthesis to mature polarised localisation in cultured rat hippocampal neurons. We show that the secretory pathway delivery of CB1R is axonally biased and that surface expressed CB1R is more stable in axons than in dendrites. This dual mechanism is mediated by the CB1R C-terminus and involves the Helix 9 (H9) domain. Removal of the H9 domain increases secretory pathway delivery to dendrites and decreases surface stability. Furthermore, CB1RΔH9 is more sensitive to agonist-induced internalisation and less efficient at downstream signalling than CB1RWT. Together, these results shed new light on how polarity of CB1R is mediated and indicate that the C-terminal H9 domain plays key roles in this process. The brain contains around 100 billion neurons that are in constant communication with one another. Each consists of a cell body, plus two components specialized for exchanging information. These are the axon, which delivers information, and the dendrites, which receive it. This exchange takes place at contact points between neurons called synapses. To send a message, a neuron releases chemicals called neurotransmitters from its axon terminals into the synapse. The neurotransmitters cross the synapse and bind to receptor proteins on the dendrites of another neuron. In doing so, they pass on the message. Cannabinoid type 1 receptors (CB1Rs) help control the flow of information at synapses. They do this by binding neurotransmitters called endocannabinoids, which are unusual among neurotransmitters. Rather than sending messages from axons to dendrites, endocannabinoids send them in the opposite direction. Thus, it is dendrites that release endocannabinoids, which then bind to CB1Rs in axon terminals. This backwards, or 'retrograde', signalling dampens the release of other neurotransmitters. This slows down brain activity, and gives rise to the 'mellow' sensation that recreational cannabis users often describe. Like most other proteins, CB1Rs are built inside the cell body. So, how do these receptors end up in the axon terminals where they are needed? Are they initially sent to both axons and dendrites, with the CB1Rs that travel to dendrites being rerouted back to axons? Or do the receptors travel directly to the axon itself? Fletcher-Jones et al. tracked newly made CB1Rs in rat neurons growing in a dish. The results revealed that the receptors go directly to the axon, before moving on to the axon terminals. A specific region of the CB1R protein is crucial for sending the receptors to the axon, and for ensuring that they do not get diverted to the dendrite surface. This region stabilizes CB1Rs at the axon surface, and helps to make the receptors available to bind endocannabinoids. CB1Rs also respond to medical marijuana, a topic that continues to generate interest as well as controversy. Activating CB1Rs could help treat a wide range of diseases, such as chronic pain, epilepsy and multiple sclerosis. Future studies should build on our understanding of CB1Rs to explore and optimize new therapeutic approaches.
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Affiliation(s)
- Alexandra Fletcher-Jones
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Keri L Hildick
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Ashley J Evans
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Yasuko Nakamura
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Kevin A Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Jeremy M Henley
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
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10
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Yang HS, Sun N, Zhao X, Kim HR, Park HJ, Kim KM, Chung KY. Role of Helix 8 in Dopamine Receptor Signaling. Biomol Ther (Seoul) 2019; 27:514-521. [PMID: 30971061 PMCID: PMC6824627 DOI: 10.4062/biomolther.2019.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 03/18/2019] [Accepted: 03/22/2019] [Indexed: 01/11/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane receptors whose agonist-induced dynamic conformational changes trigger heterotrimeric G protein activation, followed by GRK-mediated phosphorylation and arrestin-mediated desensitization. Cytosolic regions of GPCRs have been studied extensively because they are direct contact sites with G proteins, GRKs, and arrestins. Among various cytosolic regions, the role of helix 8 is least understood, although a few studies have suggested that it is involved in G protein activation, receptor localization, and/or internalization. In the present study, we investigated the role of helix 8 in dopamine receptor signaling focusing on dopamine D1 receptor (D1R) and dopamine D2 receptor (D2R). D1R couples exclusively to Gs, whereas D2R couples exclusively to Gi. Bioinformatic analysis implied that the sequences of helix 8 may affect GPCR-G protein coupling selectivity; therefore, we evaluated if swapping helix 8 between D1R and D2R changed G protein selectivity. Our results suggest that helix 8 is not involved in D1R-Gs or D2R-Gi coupling selectivity. Instead, we observed that D1R with D2R helix 8 or D1R with an increased number of hydrophobic residues in helix 8 relative to wild-type showed diminished β-arrestin-mediated desensitization, resulting in increased Gs signaling.
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Affiliation(s)
- Han-Sol Yang
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ningning Sun
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Xiaodi Zhao
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hyun-Ju Park
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
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11
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Eldeeb K, Ganjiwale AD, Chandrashekaran IR, Padgett LW, Burgess J, Howlett AC, Cowsik SM. CB1 cannabinoid receptor-phosphorylated fourth intracellular loop structure-function relationships. Pept Sci (Hoboken) 2018; 111. [PMID: 32411924 DOI: 10.1002/pep2.24104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A peptide comprising the juxtamembrane C-terminal intracellular loop 4 (IL4) of the CB1 cannabinoid receptor possesses three Serine residues (Ser402, Ser411 and Ser415). Here we report the effect of Ser phosphorylation on the CB1 IL4 peptide conformation and cellular signaling functions using nuclear magnetic resonance spectroscopy, circular dichroism, G protein activation and cAMP production. Circular dichroism studies indicated that phosphorylation at various Ser residues induced helical structure in different environments. NMR data indicates that helical content varies in the order of IL4pSer411 > IL4pSer415 > IL4 > IL4pSer402. The efficacy of phosphorylated IL4 peptides in activating Go and Gi3 ([35S]GTPγS binding) and inhibiting cAMP accumulation in N18TG2 cells were correlated with helicity changes. Treatment of cells with bradykinin, which activates PKC, augmented CB1-mediated inhibition of cAMP accumulation, and this was reversed by a PKC inhibitor, suggesting that phosphorylation of serine might be a physiologically relevant modification in vivo. We conclude that phosphorylation-dependent alterations of helicity of CB1 IL4 peptides can increase efficacy of G protein signaling.
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Affiliation(s)
- Khalil Eldeeb
- Wake Forest University Health Sciences, Winston-Salem, NC, USA.,Al Azhar Faculty of Medicine, New Damietta, Egypt
| | - Anjali D Ganjiwale
- Department of Life Sciences, Bangalore University, Bangalore, Karnataka, India
| | | | - Lea W Padgett
- J.L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | | | - Allyn C Howlett
- Wake Forest University Health Sciences, Winston-Salem, NC, USA.,J.L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
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12
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Arginine 313 of the putative 8th helix mediates Gα q/14 coupling of human CC chemokine receptors CCR2a and CCR2b. Cell Signal 2018; 53:170-183. [PMID: 30321592 DOI: 10.1016/j.cellsig.2018.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 01/29/2023]
Abstract
In man, two CC chemokine receptor isoforms, CCR2a and CCR2b, are present that belong to the rhodopsin-like G protein-coupled receptor family, and couple to Gi and Gq family members. The CCR2 receptors are known to regulate canonical functions of chemokines such as directed migration of leukocytes, and to potentially control non-canonical functions such as differentiation, proliferation, and gene transcription of immune and non-immune cells. We recently reported on the activation of phospholipase C isoenzymes and RhoA GTPases by coupling of the two CCR2 receptors to members of the Gq family, in particular Gαq and Gα14. So far little is known about the structural requirements for the CCR2/Gq/14 interaction. Interestingly, the CCR2 receptor isoforms are identical up to arginine 313 (R313) that is part of the putative 8th helix in CCR2 receptors, and the 8th helix has been implicated in the interaction of rhodopsin-like G protein-coupled receptors with Gαq. In the present work we describe that the 8th helix of both CCR2a and CCR2b is critically involved in selectively activating Gαq/14-regulated signaling. Refined analysis using various CCR2a and CCR2b mutants and analyzing their cellular signaling, e.g. ligand-dependent (i) activation of phospholipase C isoenzymes, (ii) stimulation of serum response factor-mediated gene transcription, (iii) activation of mitogen-activated protein kinases, (iv) internalization, and (v) changes in intracellular calcium concentrations, identified arginine 313 within the amino terminal portion of helix 8 to play a role for the agonist-mediated conformational changes and the formation of a Gαq/14 binding surface. We show that R313 determines Gαq/14 protein-dependent but not Gi protein-dependent cellular signaling, and plays no role in Gq/Gi-independent receptor internalization, indicating a role of R313 in biased signaling of CCR2 receptors.
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13
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Wickert M, Hildick KL, Baillie GL, Jelinek R, Aparisi Rey A, Monory K, Schneider M, Ross RA, Henley JM, Lutz B. The F238L Point Mutation in the Cannabinoid Type 1 Receptor Enhances Basal Endocytosis via Lipid Rafts. Front Mol Neurosci 2018; 11:230. [PMID: 30026687 PMCID: PMC6041392 DOI: 10.3389/fnmol.2018.00230] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 06/12/2018] [Indexed: 11/22/2022] Open
Abstract
Defining functional domains and amino acid residues in G protein coupled receptors (GPCRs) represent an important way to improve rational drug design for this major class of drug targets. The cannabinoid type 1 (CB1) receptor is one of the most abundant GPCRs in the central nervous system and is involved in many physiological and pathophysiological processes. Interestingly, cannabinoid type 1 receptor with a phenylalanine 238 to leucine mutation (CB1F238L) has been already linked to a number of both in vitro and in vivo alterations. While CB1F238L causes significantly reduced presynaptic neurotransmitter release at the cellular level, behaviorally this mutation induces increased risk taking, social play behavior and reward sensitivity in rats. However, the molecular mechanisms underlying these changes are not fully understood. In this study, we tested whether the F238L mutation affects trafficking and axonal/presynaptic polarization of the CB1 receptor in vitro. Steady state or ligand modulated surface expression and lipid raft association was analyzed in human embryonic kidney 293 (HEK293) cells stably expressing either wild-type cannabinoid type 1 receptor (CB1wt) or CB1F238L receptor. Axonal/presynaptic polarization of the CB1F238L receptor was assessed in transfected primary hippocampal neurons. We show that in vitro the CB1F238L receptor displays increased association with lipid rafts, which coincides with increased lipid raft mediated constitutive endocytosis, leading to a reduction in steady state surface expression of the CB1F238L receptor. Furthermore, the CB1F238L receptor showed increased axonal polarization in primary hippocampal neurons. These data demonstrate that endocytosis of the CB1 receptor is an important mediator of axonal/presynaptic polarization and that phenylalanine 238 plays a key role in CB1 receptor trafficking and axonal polarization.
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Affiliation(s)
- Melanie Wickert
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Keri L Hildick
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Gemma L Baillie
- Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Ruth Jelinek
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Alejandro Aparisi Rey
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Krisztina Monory
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Miriam Schneider
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.,Department of Psychology, University of Heidelberg, Heidelberg, Germany
| | - Ruth A Ross
- Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Jeremy M Henley
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.,German Resilience Center (DRZ), University Medical Center of the Johannes Gutenberg University, Mainz, Germany
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14
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Kim HR, Duc NM, Chung KY. Comprehensive Analysis of Non-Synonymous Natural Variants of G Protein-Coupled Receptors. Biomol Ther (Seoul) 2018; 26:101-108. [PMID: 28934823 PMCID: PMC5839487 DOI: 10.4062/biomolther.2017.073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 07/04/2017] [Accepted: 07/13/2017] [Indexed: 02/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane receptors and have vital signaling functions in various organs. Because of their critical roles in physiology and pathology, GPCRs are the most commonly used therapeutic target. It has been suggested that GPCRs undergo massive genetic variations such as genetic polymorphisms and DNA insertions or deletions. Among these genetic variations, non-synonymous natural variations change the amino acid sequence and could thus alter GPCR functions such as expression, localization, signaling, and ligand binding, which may be involved in disease development and altered responses to GPCR-targeting drugs. Despite the clinical importance of GPCRs, studies on the genotype-phenotype relationship of GPCR natural variants have been limited to a few GPCRs such as β-adrenergic receptors and opioid receptors. Comprehensive understanding of non-synonymous natural variations within GPCRs would help to predict the unknown genotype-phenotype relationship and yet-to-be-discovered natural variants. Here, we analyzed the non-synonymous natural variants of all non-olfactory GPCRs available from a public database, UniProt. The results suggest that non-synonymous natural variations occur extensively within the GPCR superfamily especially in the N-terminus and transmembrane domains. Within the transmembrane domains, natural variations observed more frequently in the conserved residues, which leads to disruption of the receptor function. Our analysis also suggests that only few non-synonymous natural variations have been studied in efforts to link the variations with functional consequences.
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Affiliation(s)
- Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Nguyen Minh Duc
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
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15
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Assimakopoulou M, Pagoulatos D, Nterma P, Pharmakakis N. Immunolocalization of cannabinoid receptor type 1 and CB2 cannabinoid receptors, and transient receptor potential vanilloid channels in pterygium. Mol Med Rep 2017; 16:5285-5293. [PMID: 28849159 PMCID: PMC5647061 DOI: 10.3892/mmr.2017.7246] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 01/19/2017] [Indexed: 12/17/2022] Open
Abstract
Cannabinoids, as multi-target mediators, activate cannabinoid receptors and transient receptor potential vanilloid (TRPV) channels. There is evidence to support a functional interaction of cannabinoid receptors and TRPV channels when they are coexpressed. Human conjunctiva demonstrates widespread cannabinoid receptor type 1 (CB1), CB2 and TRPV channel localization. The aim of the present study was to investigate the expression profile for cannabinoid receptors (CB1 and CB2) and TRPV channels in pterygium, an ocular surface lesion originating from the conjunctiva. Semi-serial paraffin-embedded sections from primary and recurrent pterygium samples were immunohistochemically examined with the use of specific antibodies. All of the epithelial layers in 94, 78, 96, 73 and 80% of pterygia cases, exhibited CB1, CB2, TRPV1, TRPV2 and TRPV3 cytoplasmic immunoreactivity, respectively. The epithelium of all pterygia cases (100%) showed strong, mainly nuclear, TRPV4 immunolocalization. In the pterygium stroma, scattered cells demonstrated intense CB2 immunoreactivity, whereas vascular endothelial cells were immunopositive for the cannabinoid receptors and all TRPV channels. Quantitative analyses of the immunohistochemical findings in epithelial cells demonstrated a significantly higher expression level in conjunctiva compared with primary pterygia (P=0.04) for CB1, but not for CB2 (P>0.05). Additionally, CB1 and CB2 were significantly highly expressed in primary pterygia (P=0.01), compared with recurrent pterygia. Furthermore, CB1 expression levels were significantly correlated with CB2 expression levels in primary pterygia (P=0.005), but not in recurrent pterygia (P>0.05). No significant difference was detected for all TRPV channel expression levels between pterygium (primary or recurrent) and conjunctival tissues (P>0.05). A significant correlation between the TRPV1 and TRPV3 expression levels (P<0.001) was detected independently of pterygium recurrence. Finally, TRPV channel expression was identified to be significantly higher than the expression level of cannabinoid receptors in the pterygium samples (P<0.001). The differentiated expression of cannabinoid receptors in combination with the presence of TRPV channels, in primary and recurrent pterygia, imply a potential role of these cannabinoid targets in the underlying mechanisms of pterygium.
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Affiliation(s)
- Martha Assimakopoulou
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Patras, GR‑26504 Rio, Greece
| | - Dionysios Pagoulatos
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Patras, GR‑26504 Rio, Greece
| | - Pinelopi Nterma
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Patras, GR‑26504 Rio, Greece
| | - Nikolaos Pharmakakis
- Department of Ophthalmology, School of Medicine, University of Patras, GR‑26504 Rio, Greece
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16
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Abstract
The cannabinoid CB1 receptor is abundant in the central nervous system and regulates neuronal transmission and other key physiological processes including those leading to pain, inflammation, memory, and feeding behavior. CB1 is activated by the endogenous ligands, arachidonoyl ethanolamine and 2-arachidonoyl glycerol, by various synthetic ligands (e.g., CP55940), and by Δ9-tetrahydrocannabinol, the psychoactive component of Cannabis sativa. These CB1 ligands are orthosteric and transduce downstream signals by binding CB1 and primarily inducing Gi coupling, but Gs and β-arrestin coupling are also possible. Recently, allosteric modulators for CB1 were discovered that bind to topographically distinct sites and can noncompetitively impact the potency and efficacy of orthosteric compounds. These offer the exciting potential for mechanistic analyses and for developing therapeutics. Yet, it is critical to elucidate whether a compound is a positive allosteric modulator or a negative allosteric modulator of orthosteric ligand-induced CB1 profiles to understand pathway specificity and ameliorate diseases. In this chapter, we present equilibrium and kinetic binding analysis to reveal the impact of allosteric modulators on CB1. Also described are activities consistent with CB1 activation (or inactivation) and include cellular internalization of CB1 and downstream signaling patterns. Since many CB1 allosteric modulators do not enhance G protein coupling, it is critical to distinguish CB1 activation and biased signaling patterns via β-arrestin from CB1 inactivation. These strategies can illuminate pathway specificity and are valuable for the fine-tuning of CB1 function.
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17
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Frizzled-4 C-terminus Distal to KTXXXW Motif is Essential for Normal Dishevelled Recruitment and Norrin-stimulated Activation of Lef/Tcf-dependent Transcriptional Activation. J Mol Signal 2016; 11:1. [PMID: 27096005 PMCID: PMC4834752 DOI: 10.5334/1750-2187-11-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The carboxy (C)-termini of G protein coupled receptors (GPCR) dictate essential functions. The KTXXXW motif C-terminus of Frizzleds (FZD) has been implicated in recruitment of Dishevelled (DVL). Through study of FZD4 and its associated ligand Norrin, we report that a minimum of three residues distal to the KTXXXW motif in the C-terminal tail of Frizzled-4 are essential for DVL recruitment and robust Lef/Tcf-dependent transcriptional activation in response to Norrin.
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18
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Stornaiuolo M, Bruno A, Botta L, La Regina G, Cosconati S, Silvestri R, Marinelli L, Novellino E. Endogenous vs Exogenous Allosteric Modulators in GPCRs: A dispute for shuttling CB1 among different membrane microenvironments. Sci Rep 2015; 5:15453. [PMID: 26482099 PMCID: PMC4612305 DOI: 10.1038/srep15453] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/21/2015] [Indexed: 11/26/2022] Open
Abstract
A Cannabinoid Receptor 1 (CB1) binding site for the selective allosteric modulator ORG27569 is here identified through an integrate approach of consensus pocket prediction, mutagenesis studies and Mass Spectrometry. This unprecedented ORG27569 pocket presents the structural features of a Cholesterol Consensus Motif, a cholesterol interacting region already found in other GPCRs. ORG27569 and cholesterol affects oppositely CB1 affinity for orthosteric ligands. Moreover, the rise in cholesterol intracellular level results in CB1 trafficking to the axonal region of neuronal cells, while, on the contrary, ORG27568 binding induces CB1 enrichment at the soma. This control of receptor migration among functionally different membrane regions of the cell further contributes to downstream signalling and adds a previously unknown mechanism underpinning CB1 modulation by ORG27569 , that goes beyond a mere control of receptor affinity for orthosteric ligands.
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Affiliation(s)
- Mariano Stornaiuolo
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, 80131 Naples, Italy
| | - Agostino Bruno
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, 80131 Naples, Italy
| | - Lorenzo Botta
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, 80131 Naples, Italy
| | - Giuseppe La Regina
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - Sandro Cosconati
- DiSTABiF, Seconda Università di Napoli, Via Vivaldi 43, 81100 Caserta, Italy
| | - Romano Silvestri
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - Luciana Marinelli
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, 80131 Naples, Italy
| | - Ettore Novellino
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, 80131 Naples, Italy
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de Munnik SM, Kooistra AJ, van Offenbeek J, Nijmeijer S, de Graaf C, Smit MJ, Leurs R, Vischer HF. The Viral G Protein-Coupled Receptor ORF74 Hijacks β-Arrestins for Endocytic Trafficking in Response to Human Chemokines. PLoS One 2015; 10:e0124486. [PMID: 25894435 PMCID: PMC4403821 DOI: 10.1371/journal.pone.0124486] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 03/03/2015] [Indexed: 12/21/2022] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus-infected cells express the virally encoded G protein-coupled receptor ORF74. Although ORF74 is constitutively active, it binds human CXC chemokines that modulate this basal activity. ORF74-induced signaling has been demonstrated to underlie the development of the angioproliferative tumor Kaposi’s sarcoma. Whereas G protein-dependent signaling of ORF74 has been the subject of several studies, the interaction of this viral GPCR with β-arrestins has hitherto not been investigated. Bioluminescence resonance energy transfer experiments demonstrate that ORF74 recruits β-arrestins and subsequently internalizes in response to human CXCL1 and CXCL8, but not CXCL10. Internalized ORF74 traffics via early endosomes to recycling and late endosomes. Site-directed mutagenesis and homology modeling identified four serine and threonine residues at the distal end of the intracellular carboxyl-terminal of ORF74 that are required for β-arrestin recruitment and subsequent endocytic trafficking. Hijacking of the human endocytic trafficking machinery is a previously unrecognized action of ORF74.
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Affiliation(s)
- Sabrina M. de Munnik
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Albert J. Kooistra
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Jody van Offenbeek
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Saskia Nijmeijer
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Chris de Graaf
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Martine J. Smit
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Rob Leurs
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Henry F. Vischer
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
- * E-mail:
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20
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Liu R, Nahon D, le Roy B, Lenselink EB, IJzerman AP. Scanning mutagenesis in a yeast system delineates the role of the NPxxY(x)(5,6)F motif and helix 8 of the adenosine A(2B) receptor in G protein coupling. Biochem Pharmacol 2015; 95:290-300. [PMID: 25896847 DOI: 10.1016/j.bcp.2015.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/10/2015] [Indexed: 01/05/2023]
Abstract
The adenosine receptor subfamily includes four subtypes: the A1, A2A, A2B and A3 receptors, which all belong to the superfamily of G protein-coupled receptors (GPCRs). The adenosine A2B receptor is the least investigated of the adenosine receptors, and the molecular mechanisms of its activation have hardly been explored. We used a single-GPCR-one-G protein yeast screening method in combination with mutagenesis studies, molecular modeling and bio-informatics to investigate the importance of the different amino acid residues of the NPxxY(x)6F motif and helix 8 in the human adenosine A2B receptor (hA2BR) activation. A scanning mutagenesis protocol was employed, yielding 11 single mutations and one double mutation of the NPxxY(x)6F motif and 16 single mutations of helix 8. The amino acid residues P287(7.50), Y290(7.53), R293(7.56) and I304(8.57) were found to be essential, since mutation of these amino acid residues to alanine led to a complete loss of function. Western blot analysis showed that mutant receptor R293(7.56)A was not expressed, whereas the other proteins were. Amino acid residues that are also important in receptor activation are: N286(7.49), V289(7.52), Y292(7.55), N294(8.47), F297(8.50), R298(8.51), H302(8.55) and R307(8.60). The mutation Y290(7.53)F lost 50% of efficacy, while F297(8.50)A behaved similar to wild type receptor. The double mutation, Y290(7.53)F/F297(8.50)Y, lost around 70% of efficacy and displayed a lower potency for the reference agonist 5'-(N-ethylcarboxamido)adenosine (NECA). This study provides new insight into the molecular interplay and impact of TM7 and helix 8 for hA2B receptor activation, which may be extrapolated to other adenosine receptors and possibly to other GPCRs.
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Affiliation(s)
- Rongfang Liu
- Division of Medicinal Chemistry, Leiden Academic Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Dennis Nahon
- Division of Medicinal Chemistry, Leiden Academic Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Beau le Roy
- Division of Medicinal Chemistry, Leiden Academic Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Eelke B Lenselink
- Division of Medicinal Chemistry, Leiden Academic Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Adriaan P IJzerman
- Division of Medicinal Chemistry, Leiden Academic Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
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Rognan D, Mus-Veteau I. Three-Dimensional Structure of the Smoothened Receptor: Implications for Drug Discovery. TOPICS IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1007/7355_2014_64] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
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22
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Spomer L, Gertzen CGW, Schmitz B, Häussinger D, Gohlke H, Keitel V. A membrane-proximal, C-terminal α-helix is required for plasma membrane localization and function of the G Protein-coupled receptor (GPCR) TGR5. J Biol Chem 2013; 289:3689-702. [PMID: 24338481 DOI: 10.1074/jbc.m113.502344] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The C terminus of G protein-coupled receptors (GPCRs) is important for G protein-coupling and activation; in addition, sorting motifs have been identified in the C termini of several GPCRs that facilitate correct trafficking from the endoplasmic reticulum to the plasma membrane. The C terminus of the GPCR TGR5 lacks any known sorting motif such that other factors must determine its trafficking. Here, we investigate deletion and substitution variants of the membrane-proximal C terminus of TGR5 with respect to plasma membrane localization and function using immunofluorescence staining, flow cytometry, and luciferase assays. Peptides of the membrane-proximal C-terminal variants are subjected to molecular dynamics simulations and analyzed with respect to their secondary structure. Our results reveal that TGR5 plasma membrane localization and responsiveness to extracellular ligands is fostered by a long (≥ 9 residues) α-helical stretch at the C terminus, whereas the presence of β-strands or only a short α-helical stretch leads to retention in the endoplasmic reticulum and a loss of function. As a proof-of-principle, chimeras of TGR5 containing the membrane-proximal amino acids of the β2 adrenergic receptor (β2AR), the sphingosine 1-phosphate receptor-1 (S1P1), or the κ-type opioid receptor (κOR) were generated. These TGR5β2AR, TGR5S1P1, or TGR5κOR chimeras were correctly sorted to the plasma membrane. As the exchanged amino acids of the β2AR, the S1P1, or the κOR form α-helices in crystal structures but lack significant sequence identity to the respective TGR5 sequence, we conclude that the secondary structure of the TGR5 membrane-proximal C terminus is the determining factor for plasma membrane localization and responsiveness towards extracellular ligands.
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Affiliation(s)
- Lina Spomer
- From the Clinic for Gastroenterology, Hepatology, and Infectious Diseases and
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23
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Ahn KH, Mahmoud MM, Shim JY, Kendall DA. Distinct roles of β-arrestin 1 and β-arrestin 2 in ORG27569-induced biased signaling and internalization of the cannabinoid receptor 1 (CB1). J Biol Chem 2013; 288:9790-9800. [PMID: 23449980 PMCID: PMC3617280 DOI: 10.1074/jbc.m112.438804] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 02/19/2013] [Indexed: 12/14/2022] Open
Abstract
The cannabinoid receptor 1 (CB1) is a G protein-coupled receptor primarily expressed in brain tissue that has been implicated in several disease states. CB1 allosteric compounds, such as ORG27569, offer enormous potential as drugs over orthosteric ligands, but their mechanistic, structural, and downstream effects upon receptor binding have not been established. Previously, we showed that ORG27569 enhances agonist binding affinity to CB1 but inhibits G protein-dependent agonist signaling efficacy in HEK293 cells and rat brain expressing the CB1 receptor (Ahn, K. H., Mahmoud, M. M., and Kendall, D. A. (2012) J. Biol. Chem. 287, 12070-12082). Here, we identify the mediators of CB1 receptor internalization and ORG27569-induced G protein-independent signaling. Using siRNA technology, we elucidate an ORG27569-induced signaling mechanism for CB1 wherein β-arrestin 1 mediates short term signaling to ERK1/2 with a peak at 5 min and other upstream kinase components including MEK1/2 and c-Src. Consistent with these findings, we demonstrate co-localization of CB1-GFP with red fluorescent protein-β-arrestin 1 upon ORG27569 treatment using confocal microscopy. In contrast, we show the critical role of β-arrestin 2 in CB1 receptor internalization upon treatment with CP55940 (agonist) or treatment with ORG27569. These results demonstrate for the first time the involvement of β-arrestin in CB1-biased signaling by a CB1 allosteric modulator and also define the differential role of the two β-arrestin isoforms in CB1 signaling and internalization.
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Affiliation(s)
- Kwang H Ahn
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269
| | - Mariam M Mahmoud
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269
| | - Joong-Youn Shim
- J. L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina 27707
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269.
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Walther C, Lotze J, Beck-Sickinger AG, Mörl K. The anterograde transport of the human neuropeptide Y2 receptor is regulated by a subtype specific mechanism mediated by the C-terminus. Neuropeptides 2012; 46:335-43. [PMID: 23020974 DOI: 10.1016/j.npep.2012.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 08/24/2012] [Accepted: 08/28/2012] [Indexed: 02/06/2023]
Abstract
The export of newly synthesized proteins, including G protein-coupled receptors (GPCR), from the endoplasmic reticulum (ER) and further transport to the plasma membrane is a tightly regulated process. ER export and subsequent cell surface targeting of GPCR is initially mediated through COPII-coated vesicles. It is governed by specific amino acid sequences located in extracellular as well as intracellular receptor domains, for example in the C-terminus (CT) of the receptor. Herein, we determined the role of the CT in the anterograde transport of the human neuropeptide Y receptor (hYR) type 2. We identified a short sequence motif in the membrane proximal CT: Y(x)(3)F(x)(3)F in the region of the putative 8th helix has a critical functional relevance for the anterograde transport of hY(2)R, since its deletion leads to accumulation of the receptor in the ER. It is sequence and position specific. Furthermore we identified a distinct role of C-terminal sequences in hY(1)R, hY(2)R, hY(4)R and hY(5)R. Regulation of hY(5)R export is regulated by a different mechanism as compared to hY(2)R. Different sequence elements with respect to function and localization are involved as demonstrated by the construction of a hY(2)/hY(5) receptor chimera and a noneffective deletion in the region of helix eight in the hY(5)R. In contrast to hY(2)R, deletion of the corresponding helical segment F(x)(3)L(x)(3)F has no influence on anterograde transport of hY(1)R, whereas deletion of F(x)(3)I(x)(3)V in hY(4)R restrains the receptor to the Golgi apparatus. Interestingly this pattern is not mirrored by repression of COPII vesicle transport by Sar1[H79G] overexpression. Whereas the 8th helix is involved before or at the level of Sar1 dependent export pathways in the ER for the hY(2)R, in hY(4)R helix eight is involved at later stages of anterograde transport.
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Affiliation(s)
- Cornelia Walther
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Universität Leipzig, Germany
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25
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Juhl C, Kosel D, Beck-Sickinger AG. Two motifs with different function regulate the anterograde transport of the adiponectin receptor 1. Cell Signal 2012; 24:1762-9. [DOI: 10.1016/j.cellsig.2012.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 04/22/2012] [Accepted: 05/05/2012] [Indexed: 01/16/2023]
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Membrane-sensitive conformational states of helix 8 in the metabotropic Glu2 receptor, a class C GPCR. PLoS One 2012; 7:e42023. [PMID: 22870276 PMCID: PMC3411606 DOI: 10.1371/journal.pone.0042023] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 06/29/2012] [Indexed: 11/19/2022] Open
Abstract
The recent elucidation of the X-ray structure of several class A GPCRs clearly indicates that the amphipathic helix 8 (H8) is a conserved structural domain in most crystallized GPCRs. Very little is known about the presence and the possible role of an analogous H8 domain in the distantly related class C GPCRs. In this study, we investigated the structural properties for the H8 domain of the mGluR2 receptor, a class C GPCR, by applying extended molecular dynamics simulations. Our study indicates that the amphipathic H8 adopts membrane-sensitive conformational states, which depend on the membrane composition. Cholesterol-rich membranes stabilize the helical structure of H8 whereas cholesterol-depleted membranes induce a disruption of H8. The observed link between membrane cholesterol levels and H8 conformational states suggests that H8 behaves as a sensor of cholesterol concentration.
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Aratake Y, Okuno T, Matsunobu T, Saeki K, Takayanagi R, Furuya S, Yokomizo T. Helix 8 of leukotriene B
4
receptor 1 inhibits ligand‐induced internalization. FASEB J 2012; 26:4068-78. [DOI: 10.1096/fj.12-212050] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Yoshifusa Aratake
- Department of Medical BiochemistryGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
- Department of Medicine and Bioregulatory ScienceGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
| | - Toshiaki Okuno
- Department of Medical BiochemistryGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
| | - Takehiko Matsunobu
- Department of Medical BiochemistryGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
| | - Kazuko Saeki
- Department of Medical BiochemistryGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
| | - Ryoichi Takayanagi
- Department of Medicine and Bioregulatory ScienceGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
| | - Sonoko Furuya
- Section of Brain Structure Information, Supportive Center for Brain ResearchNational Institute for Physiological SciencesAichiJapan
| | - Takehiko Yokomizo
- Department of Medical BiochemistryGraduate School of Medical SciencesKyushu UniversityFukuokaJapan
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Orel M, Padrós E, Manyosa J. Structural features of the C-terminus from the human neurokinin-1 receptor. FEBS J 2012; 279:2357-67. [DOI: 10.1111/j.1742-4658.2012.08614.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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29
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Oddi S, Dainese E, Sandiford S, Fezza F, Lanuti M, Chiurchiù V, Totaro A, Catanzaro G, Barcaroli D, De Laurenzi V, Centonze D, Mukhopadhyay S, Selent J, Howlett AC, Maccarrone M. Effects of palmitoylation of Cys(415) in helix 8 of the CB(1) cannabinoid receptor on membrane localization and signalling. Br J Pharmacol 2012; 165:2635-51. [PMID: 21895628 PMCID: PMC3423250 DOI: 10.1111/j.1476-5381.2011.01658.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 07/15/2011] [Accepted: 08/05/2011] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The CB(1) cannabinoid receptor is regulated by its association with membrane microdomains such as lipid rafts. Here, we investigated the role of palmitoylation of the CB(1) receptor by analysing the functional consequences of site-specific mutation of Cys(415) , the likely site of palmitoylation at the end of helix 8, in terms of membrane association, raft targeting and signalling. EXPERIMENTAL APPROACH The palmitoylation state of CB(1) receptors in rat forebrain was assessed by depalmitoylation/repalmitoylation experiments. Cys(415) was replaced with alanine by site-directed mutagenesis. Green fluorescence protein chimeras of both wild-type and mutant receptors were transiently expressed and functionally characterized in SH-SY5Y cells and HEK-293 cells by means of confocal microscopy, cytofluorimetry and competitive binding assays. Confocal fluorescence recovery after photobleaching was used to assess receptor membrane dynamics, whereas signalling activity was assessed by [(35) S]GTPγS, cAMP and co-immunoprecipitation assays. KEY RESULTS Endogenous CB(1) receptors in rat brain were palmitoylated. Mutation of Cys(415) prevented the palmitoylation of the receptor in transfected cells and reduced its recruitment to plasma membrane and lipid rafts; it also increased protein diffusional mobility. The same mutation markedly reduced the functional coupling of CB(1) receptors with G-proteins and adenylyl cyclase, whereas depalmitoylation abolished receptor association with a specific subset of G-proteins. CONCLUSIONS AND IMPLICATIONS CB(1) receptors were post-translationally modified by palmitoylation. Mutation of Cys(415) provides a receptor that is functionally impaired in terms of membrane targeting and signalling. LINKED ARTICLES This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.
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Affiliation(s)
- Sergio Oddi
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Enrico Dainese
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Simone Sandiford
- Neuroscience/Drug Abuse Research Program, Biomedical Biotechnology Research Institute, North Carolina Central UniversityDurham, NC, USA
| | - Filomena Fezza
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
- Department of Experimental Medicine and Biochemical Sciences, University of Rome ‘Tor Vergata’Rome, Italy
| | - Mirko Lanuti
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Valerio Chiurchiù
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Antonio Totaro
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Giuseppina Catanzaro
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
| | - Daniela Barcaroli
- Department of Biomedical Sciences, University of Chieti-Pescara ‘G. d'Annunzio’Chieti, Italy
| | - Vincenzo De Laurenzi
- Department of Biomedical Sciences, University of Chieti-Pescara ‘G. d'Annunzio’Chieti, Italy
| | - Diego Centonze
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
- Department of Neurosciences, University of Rome ‘Tor Vergata’Rome, Italy
| | - Somnath Mukhopadhyay
- Neuroscience/Drug Abuse Research Program, Biomedical Biotechnology Research Institute, North Carolina Central UniversityDurham, NC, USA
| | - Jana Selent
- Research Group of biomedical Informatics (GRIB-IMIM), University of Pompeu Fabra, Barcelona Biomedical Research Park (PRBB)Barcelona, Spain
| | - Allyn C Howlett
- Department of Physiology and Pharmacology, Wake Forest University Health SciencesWinston-Salem, NC, USA
| | - Mauro Maccarrone
- Department of Biomedical Sciences, University of TeramoTeramo, Italy
- European Center for Brain Research (CERC)/Santa Lucia Foundation I.R.C.C.S.Rome, Italy
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Ahn KH, Mahmoud MM, Kendall DA. Allosteric modulator ORG27569 induces CB1 cannabinoid receptor high affinity agonist binding state, receptor internalization, and Gi protein-independent ERK1/2 kinase activation. J Biol Chem 2012; 287:12070-82. [PMID: 22343625 DOI: 10.1074/jbc.m111.316463] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The cannabinoid receptor 1 (CB1), a member of the class A G protein-coupled receptor family, is expressed in brain tissue where agonist stimulation primarily activates the pertussis toxin-sensitive inhibitory G protein (G(i)). Ligands such as CP55940 ((1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3- hydroxypropyl)cyclohexan-1-ol) and Δ(9)-tetrahydrocannabinol are orthosteric agonists for the receptor, bind the conventional binding pocket, and trigger G(i)-mediated effects including inhibition of adenylate cyclase. ORG27569 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)ethyl]amide) has been identified as an allosteric modulator that displays positive cooperativity for CP55940 binding to CB1 yet acts as an antagonist of G protein coupling. To examine this apparent conundrum, we used the wild-type CB1 and two mutants, T210A and T210I (D'Antona, A. M., Ahn, K. H., and Kendall, D. A. (2006) Biochemistry 45, 5606-5617), which collectively cover a spectrum of receptor states from inactive to partially active to more fully constitutively active. Using these receptors, we demonstrated that ORG27569 induces a CB1 receptor state that is characterized by enhanced agonist affinity and decreased inverse agonist affinity consistent with an active conformation. Also consistent with this conformation, the impact of ORG27569 binding was most dramatic on the inactive T210A receptor and less pronounced on the already active T210I receptor. Although ORG27569 antagonized CP55940-induced guanosine 5'-3-O-(thio)triphosphate binding, which is indicative of G protein coupling inhibition in a concentration-dependent manner, the ORG27569-induced conformational change of the CB1 receptor led to cellular internalization and downstream activation of ERK signaling, providing the first case of allosteric ligand-biased signaling via CB1. ORG27569-induced ERK phosphorylation persisted even after pertussis toxin treatment to abrogate G(i) and occurs in HEK293 and neuronal cells.
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Affiliation(s)
- Kwang H Ahn
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269, USA
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Nithipatikom K, Gomez-Granados AD, Tang AT, Pfeiffer AW, Williams CL, Campbell WB. Cannabinoid receptor type 1 (CB1) activation inhibits small GTPase RhoA activity and regulates motility of prostate carcinoma cells. Endocrinology 2012; 153:29-41. [PMID: 22087025 PMCID: PMC3249681 DOI: 10.1210/en.2011-1144] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cannabinoid receptor type 1 (CB1) is a G protein-coupled receptor that is activated in an autocrine fashion by the endocannabinoids (EC), N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG). The CB1 and its endogenous and synthetic agonists are emerging as therapeutic targets in several cancers due to their ability to suppress carcinoma cell invasion and migration. However, the mechanisms that the CB1 regulates cell motility are not well understood. In this study, we examined the molecular mechanisms that diminish cell migration upon the CB1 activation in prostate carcinoma cells. The CB1 activation with the agonist WIN55212 significantly diminishes the small GTPase RhoA activity but modestly increases the Rac1 and Cdc42 activity. The diminished RhoA activity is accompanied by the loss of actin/myosin microfilaments, cell spreading, and cell migration. Interestingly, the CB1 inactivation with the selective CB1 antagonist AM251 significantly increases RhoA activity, enhances microfilament formation and cell spreading, and promotes cell migration. This finding suggests that endogenously produced EC activate the CB1, resulting in chronic repression of RhoA activity and cell migration. Consistent with this possibility, RhoA activity is significantly diminished by the exogenous application of AEA but not by 2-AG in PC-3 cells (cells with very low AEA hydrolysis). Pretreatment of cells with a monoacylglycerol lipase inhibitor, JZL184, which blocks 2-AG hydrolysis, decreases the RhoA activity. These results indicate the unique CB1 signaling and support the model that EC, through their autocrine activation of CB1 and subsequent repression of RhoA activity, suppress migration in prostate carcinoma cells.
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Affiliation(s)
- Kasem Nithipatikom
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
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The role of palmitoylation in signalling, cellular trafficking and plasma membrane localization of protease-activated receptor-2. PLoS One 2011; 6:e28018. [PMID: 22140500 PMCID: PMC3226677 DOI: 10.1371/journal.pone.0028018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 10/29/2011] [Indexed: 01/05/2023] Open
Abstract
Protease-activated receptor-2 (PAR2) is a G protein coupled receptor (GPCR) activated by proteolytic cleavage of its amino terminal domain by trypsin-like serine proteases. This irreversible activation mechanism leads to rapid receptor desensitization by internalisation and degradation. We have explored the role of palmitoylation, the post-translational addition of palmitate, in PAR2 signalling, trafficking, cell surface expression and desensitization. Experiments using the palmitoylation inhibitor 2-bromopalmitate indicated that palmitate addition is important in trafficking of PAR2 endogenously expressed by prostate cancer cell lines. This was supported by palmitate labelling using two approaches, which showed that PAR2 stably expressed by CHO-K1 cells is palmitoylated and that palmitoylation occurs on cysteine 361. Palmitoylation is required for optimal PAR2 signalling as Ca2+ flux assays indicated that in response to trypsin agonism, palmitoylation deficient PAR2 is ∼9 fold less potent than wildtype receptor with a reduction of about 33% in the maximum signal induced via the mutant receptor. Confocal microscopy, flow cytometry and cell surface biotinylation analyses demonstrated that palmitoylation is required for efficient cell surface expression of PAR2. We also show that receptor palmitoylation occurs within the Golgi apparatus and is required for efficient agonist-induced rab11a-mediated trafficking of PAR2 to the cell surface. Palmitoylation is also required for receptor desensitization, as agonist-induced β-arrestin recruitment and receptor endocytosis and degradation were markedly reduced in CHO-PAR2-C361A cells compared with CHO-PAR2 cells. These data provide new insights on the life cycle of PAR2 and demonstrate that palmitoylation is critical for efficient signalling, trafficking, cell surface localization and degradation of this receptor.
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Feierler J, Wirth M, Welte B, Schüssler S, Jochum M, Faussner A. Helix 8 plays a crucial role in bradykinin B(2) receptor trafficking and signaling. J Biol Chem 2011; 286:43282-93. [PMID: 22016392 DOI: 10.1074/jbc.m111.256909] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon activation the human bradykinin B(2) receptor (B(2)R) acts as guanine nucleotide exchange factor for the G proteins G(q/11) and G(i). Thereafter, it gets phosphorylated by G protein-coupled receptor kinases (GRKs) and recruits β-arrestins, which block further G protein activation and promote B(2)R internalization via clathrin-coated pits. As for most G protein-coupled receptors of family A, an intracellular helix 8 after transmembrane domain 7 is also predicted for the B(2)R. We show here that disruption of helix 8 in the B(2)R by either C-terminal truncation or just by mutation of a central amino acid (Lys-315) to a helix-breaking proline resulted in strong reduction of surface expression. Interestingly, this malfunction could be overcome by the addition of the membrane-permeable B(2)R antagonist JSM10292, suggesting that helix 8 has a general role for conformational stabilization that can be accounted for by an appropriate antagonist. Intriguingly, an intact helix 8, but not the C terminus with its phosphorylation sites, was indispensable for receptor sequestration and for interaction of the B(2)R with GRK2/3 and β-arrestin2 as shown by co-immunoprecipitation. Recruitment of β-arrestin1, however, required the presence of the C terminus. Taken together, our results demonstrate that helix 8 of the B(2)R plays a crucial role not only in efficient trafficking to the plasma membrane or the activation of G proteins but also for the interaction of the B(2)R with GRK2/3 and β-arrestins. Additional data obtained with chimera of B(2)R with other G protein-coupled receptors of family A suggest that helix 8 might have similar functions in other GPCRs as well.
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Affiliation(s)
- Jens Feierler
- Abteilung für Klinische Chemie und Klinische Biochemie, Ludwig-Maximilians-Universität, Nussbaumstrasse 20, D-80336 München, Germany
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Stadel R, Ahn KH, Kendall DA. The cannabinoid type-1 receptor carboxyl-terminus, more than just a tail. J Neurochem 2011; 117:1-18. [PMID: 21244428 DOI: 10.1111/j.1471-4159.2011.07186.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The cannabinoid type-1 (CB(1)) receptor is a G protein-coupled receptor that binds the main active ingredient of marijuana, Δ(9)-tetrahydrocannabinol, and has been implicated in several disease states, including drug addiction, anxiety, depression, obesity, and chronic pain. In the two decades since the discovery of CB(1), studies at the molecular level have centered on the transmembrane core. This interest has now expanded as we discover that other regions of CB(1), including the CB(1) carboxyl-terminus, have critical structures that are important for CB(1) activity and regulation. Following the recent description of the three dimensional structure of the full-length CB(1) carboxyl-terminal tail [Biopolymers (2009) vol. 91, pp. 565-573], several residues and structural motifs including two α-helices (termed H8 and H9) have been postulated to interact with common G protein-coupled receptor accessory proteins, such as G-proteins and β-arrestins. This discourse will focus on the CB(1) carboxyl-terminus; our current understanding of the structural features of this region, evidence for its interaction with proteins, and the impact of structure on the binding and regulatory function of CB(1) accessory proteins. The involvement of the carboxyl-terminus in the receptor life cycle including activation, desensitization, and internalization will be highlighted.
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Affiliation(s)
- Rebecca Stadel
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, USA
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Identification of an antithrombotic allosteric modulator that acts through helix 8 of PAR1. Proc Natl Acad Sci U S A 2011; 108:2951-6. [PMID: 21282664 DOI: 10.1073/pnas.1014863108] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G protein-coupled receptors (GPCRs) can assume multiple conformations and possess multiple binding sites. Whereas endogenous agonists acting at the orthosteric binding site stabilize the active receptor conformation, small molecules that act at nonorthosteric sites can stabilize alternative conformations. The large majority of these allosteric modulators associate with extracellular loops of GPCRs. The role of intracellular domains in mediating allosteric modulation is largely unknown. In screening a small-molecule library for inhibitors of platelet activation, we identified a family of compounds that modified PAR1-mediated granule secretion. The most potent inhibitory compound, termed JF5, also demonstrated noncompetitive inhibition of the α(2A)-adrenergic receptor. Aggregation studies using a battery of platelet GPCR agonists demonstrated that sensitivity to JF5 was limited to GPCRs that possessed a constrained eighth helix, as defined by a C-terminal palmitoylation site and interactions with TM7 and the i1 loop. Inhibition by JF5 was overcome in a PAR1 mutant in which the eighth helix was deleted, confirming a role for helix 8 in JF5 activity. Evaluation of downstream signaling showed that JF5 was selective with regard to G protein coupling, blocking signaling mediated by G(αq) but not G(α12). The compound inhibited thrombus formation in vivo following vascular injury with an IC(50) of ∼1 mg/kg. These results indicate a role for helix 8 in conferring sensitivity to small molecules, and show that this sensitivity can be exploited to control platelet activation during thrombus formation.
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