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Libanje F, Delille R, Young PA, Rolland S, Meyer-Losic F, Lewkowicz E, Klinz S. NTSR1 glycosylation and MMP dependent cleavage generate three distinct forms of the protein. Sci Rep 2023; 13:4663. [PMID: 36949141 PMCID: PMC10033925 DOI: 10.1038/s41598-023-31790-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 03/17/2023] [Indexed: 03/24/2023] Open
Abstract
NTSR1 abnormal expression by cancer cells makes it a strategic target for antitumoral therapies, such as compounds that use NTSR1 binding probes to deliver cytotoxic agents to tumor cells. Success of these therapies relies on NTSR1 protein availability and accessibility; therefore, understanding the protein's biology is crucial. We studied NTSR1 protein in exogenously and endogenously expressing non-tumoral and tumoral cells. We found NTSR1 to be expressed as three distinct protein forms: the NTSR1-high form, a glycosylated protein; the NTSR1-low form, a N-terminally cleaved and de-glycosylated protein; and the NTSR1-LP protein with the MW size predicted by its NTSR1 amino acid sequence. We show that the NTSR1-high form is cleaved by MMPs to generate the NTSR1-low form, a process that is promoted by the Neurotensin (NTS) ligand. In addition, NTS induced the internalization of plasma membrane localized NTSR1 and degradation of NTSR1-low form via the proteasome. Importantly, we found NTSR1-low form to be the most abundant form in the tumoral cells and in PDAC Patient Derived Xenograft, demonstrating its physiopathological relevance. Altogether, our work provides important technical and experimental tools as well as new crucial insights into NTSR1 protein biology that are required to develop clinically relevant NTSR1 targeting anti-tumoral therapies.
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Affiliation(s)
- Fotine Libanje
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France.
| | - Raphael Delille
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Pamela A Young
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Sylvie Rolland
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | | | - Elodie Lewkowicz
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Stephan Klinz
- Early Development and Translational Sciences, IPSEN Bioscience, Cambridge, USA
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2
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Toy-Miou-Leong M, Bachelet CM, Pélaprat D, Rostène W, Forgez P. NT Agonist Regulates Expression of Nuclear High-affinity Neurotensin Receptors. J Histochem Cytochem 2016; 52:335-45. [PMID: 14966200 DOI: 10.1177/002215540405200304] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Neurotensin (NT) exerts multiple functions in the central nervous system and peripheral tissues. Its actions are mainly mediated by a high-affinity G-protein-coupled receptor, the NT-1 receptor. In this study we demonstrated a nuclear NT binding site in different cellular models. We first noted that a large percentage of NT-1 receptor cell body immunoreactivity was located in the nuclear soma and nuclear envelope of rat substantia nigra, a brain area rich in NT-containing axon terminals. The NT-1 receptor was also visualized in purified nuclei from CHO cells stably transfected with NT-1 receptor coupled to the enhanced green fluorescence protein by immunocytochemistry. We observed that both the nuclear envelope and the nuclear soma were labeled, and the labeling intensity significantly increased after NT agonist treatment. These results suggested that NT-1 receptors, present in both the nuclear soma and the nuclear envelope, can be modulated by the ligand. Lastly, [125I]-NT binding experiments performed on isolated nuclei from a human lung cancer cell line endogenously expressing NT-1 receptor and NT, LNM35, revealed the existence of nuclear Gpp(NHp)-sensitive binding sites. These binding sites markedly decreased when cells were chronically treated with an NT-1 receptor antagonist, SR 48692. Taken together, these data suggest that the agonist regulates the expression of nuclear NT-1 receptors.
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3
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Gerbier R, Leroux V, Couvineau P, Alvear-Perez R, Maigret B, Llorens-Cortes C, Iturrioz X. New structural insights into the apelin receptor: identification of key residues for apelin binding. FASEB J 2014; 29:314-22. [PMID: 25359495 DOI: 10.1096/fj.14-256339] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Apelin is the endogenous ligand of the orphan 7-transmembrane domain GPCR APJ, now named the apelin receptor (ApelinR). Apelin plays a prominent role in body fluid and cardiovascular homeostasis. To better understand the structural organization of the ApelinR, we built 3 homology 3-dimensional (3D) models of the human ApelinR using the validated cholecystokinin receptor-1 3D model or the X-ray structures of the β2-adrenergic and CXCR4 receptors as templates. Docking of the pyroglutamyl form of apelin 13 (pE13F) into these models revealed the conservation at the bottom of the binding site of a hydrophobic cavity in which the C-terminal Phe of pE13F was embedded. In contrast, at the top of the binding site, depending on the model, different interactions were visualized between acidic residues of the ApelinR and the basic residues of pE13F. Using site-directed mutagenesis, we showed that Asp 92, Glu 172, and Asp 282 of rat ApelinR are key residues in apelin binding by interacting with Lys 8, Arg 2, and Arg 4 of pE13F, respectively. These residues are only seen in the CXCR4-based ApelinR 3D model, further validating this model. These findings bring new insights into the structural organization of the ApelinR and the mode of apelin binding.
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Affiliation(s)
- Romain Gerbier
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Vincent Leroux
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Pierre Couvineau
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Rodrigo Alvear-Perez
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Bernard Maigret
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Catherine Llorens-Cortes
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Xavier Iturrioz
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
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4
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Wu X, Xiong E, An S, Gong F, Wang W. Sequential extraction results in improved proteome profiling of medicinal plant Pinellia ternata tubers, which contain large amounts of high-abundance proteins. PLoS One 2012. [PMID: 23185632 PMCID: PMC3502364 DOI: 10.1371/journal.pone.0050497] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Pinellia ternata tuber is one of the well-known Chinese traditional medicines. In order to understand the pharmacological properties of tuber proteins, it is necessary to perform proteome analysis of P. ternata tubers. However, a few high-abundance proteins (HAPs), mainly mannose-binding lectin (agglutinin), exist in aggregates of various sizes in the tubers and seriously interfere with proteome profiling by two-dimensional electrophoresis (2-DE). Therefore, selective depletion of these HAPs is a prerequisite for enhanced proteome analysis of P. ternata tubers. Based on differential protein solubility, we developed a novel protocol involving two sequential extractions for depletion of some HAPs and prefractionation of tuber proteins prior to 2-DE. The first extraction using 10% acetic acid selectively extracted acid-soluble HAPs and the second extraction using the SDS-containing buffer extracted remaining acid-insoluble proteins. After application of the protocol, 2-DE profiles of P. ternata tuber proteins were greatly improved and more protein spots were detected, especially low-abundance proteins. Moreover, the subunit composition of P. ternata lectin was analyzed by electrophoresis. Native lectin consists of two hydrogen-bonded subunits (11 kDa and 25 kDa) and the 11 kDa subunit was a glycoprotein. Subsequently, major HAPs in the tubers were analyzed by mass spectrometry, with nine protein spots being identified as lectin isoforms. The methodology was easy to perform and required no specialized apparatus. It would be useful for proteome analysis of other tuber plants of Araceae.
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Affiliation(s)
- XiaoLin Wu
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - ErHui Xiong
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - SuFang An
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - FangPing Gong
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Wei Wang
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, College of Life Science, Henan Agricultural University, Zhengzhou, China
- * E-mail:
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5
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Iturrioz X, Gerbier R, Leroux V, Alvear-Perez R, Maigret B, Llorens-Cortes C. By interacting with the C-terminal Phe of apelin, Phe255 and Trp259 in helix VI of the apelin receptor are critical for internalization. J Biol Chem 2010; 285:32627-37. [PMID: 20675385 DOI: 10.1074/jbc.m110.127167] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Apelin is the endogenous ligand of the orphan seven-transmembrane domain (TM) G protein-coupled receptor APJ. Apelin is involved in the regulation of body fluid homeostasis and cardiovascular functions. We previously showed the importance of the C-terminal Phe of apelin 17 (K17F) in the hypotensive activity of this peptide. Here, we show either by deleting the Phe residue (K16P) or by substituting it by an Ala (K17A), that it plays a crucial role in apelin receptor internalization but not in apelin binding or in Gα(i)-protein coupling. Then we built a homology three-dimensional model of the human apelin receptor using the cholecystokinin receptor-1 model as a template, and we subsequently docked K17F into the binding site. We visualized a hydrophobic cavity at the bottom of the binding pocket in which the C-terminal Phe of K17F was embedded by Trp(152) in TMIV and Trp(259) and Phe(255) in TMVI. Using molecular modeling and site-directed mutagenesis studies, we further showed that Phe(255) and Trp(259) are key residues in triggering receptor internalization without playing a role in apelin binding or in Gα(i)-protein coupling. These findings bring new insights into apelin receptor activation and show that Phe(255) and Trp(259), by interacting with the C-terminal Phe of the pyroglutamyl form of apelin 13 (pE13F) or K17F, are crucial for apelin receptor internalization.
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Affiliation(s)
- Xavier Iturrioz
- INSERM, U691, Collège de France, Université Pierre et Marie-Curie Paris 6, Paris FR-75005, France
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6
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Ozawa A, Lindberg I, Roth B, Kroeze WK. Deorphanization of novel peptides and their receptors. AAPS JOURNAL 2010; 12:378-84. [PMID: 20446073 DOI: 10.1208/s12248-010-9198-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 04/14/2010] [Indexed: 12/31/2022]
Abstract
Peptide hormones and neuropeptides play important roles in endocrine and neural signaling, often using G protein-coupled receptor (GPCR)-mediated signaling pathways. However, the rate of novel peptide discovery has slowed dramatically in recent years. Genomic sequencing efforts have yielded a large number of cDNA sequences that potentially encode novel candidate peptide precursors, as well as hundreds of orphan GPCRs with no known cognate ligands. The complexity of peptide signaling is further highlighted by the requirement for specific posttranslational processing steps, and these must be accomplished in vitro prior to testing newly discovered peptide precursor candidates in receptor assays. In this review, we present historic as well as current approaches to peptide discovery and GPCR deorphanization. We conclude that parallel and combinatorial discovery methods are likely to represent the most fruitful avenues for both peptide discovery as well as for matching the remaining GPCRs with their peptide ligands.
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Affiliation(s)
- Akihiko Ozawa
- Department of Anatomy and Neurobiology, University of Maryland-Baltimore, 20 Penn St. HSFII Rm S251, Baltimore, Maryland 21201, USA
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7
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Iturrioz X, Alvear-Perez R, De Mota N, Franchet C, Guillier F, Leroux V, Dabire H, Le Jouan M, Chabane H, Gerbier R, Bonnet D, Berdeaux A, Maigret B, Galzi JL, Hibert M, Llorens-Cortes C. Identification and pharmacological properties of E339-3D6, the first nonpeptidic apelin receptor agonist. FASEB J 2009; 24:1506-17. [PMID: 20040517 DOI: 10.1096/fj.09-140715] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Apelin plays a prominent role in body fluid and cardiovascular homeostasis. To explore further upstream the role played by this peptide, nonpeptidic agonists and antagonists of the apelin receptor are required. To identify such compounds that do not exist to date, we used an original fluorescence resonance energy transfer-based assay to screen a G-protein-coupled receptor-focused library of fluorescent compounds on the human EGFP-tagged apelin receptor. This led to isolated E339-3D6 that displayed a 90 nM affinity and behaved as a partial agonist with regard to cAMP production and as a full agonist with regard to apelin receptor internalization. Finally, E339-3D6 induced vasorelaxation of rat aorta precontracted with noradrenaline and potently inhibited systemic vasopressin release in water-deprived mice when intracerebroventricularly injected. This compound represents the first nonpeptidic agonist of the apelin receptor, the optimization of which will allow development of a new generation of vasodilator and aquaretic agents.
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Affiliation(s)
- Xavier Iturrioz
- INSERM U691, Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
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8
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Grimsey NL, Narayan PJ, Dragunow M, Glass M. A novel high-throughput assay for the quantitative assessment of receptor trafficking. Clin Exp Pharmacol Physiol 2008; 35:1377-82. [PMID: 18565191 DOI: 10.1111/j.1440-1681.2008.04991.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. Receptor transport between intracellular compartments has important consequences for receptor function and is an exciting area of current study. Existing methods for studying receptor trafficking often require labour-intensive techniques or are difficult to quantify reliably. We report a novel high-throughput method that uses automated imaging and analysis tools to accurately quantify cannabinoid CB1 receptor trafficking. 2. Haemagglutinin (HA)-tagged CB1 was stably expressed in HEK-293 cells and cell surface or total receptors were detected immunocytochemically. Images of receptor and nuclear staining were acquired with an automated fluorescent microscope (Discovery-1; Molecular Devices, Sunnyvale, CA, USA) and quantified at high throughput with MetaMorph (Molecular Devices) software. The 'Granularity' assay measured internalization by counting receptor clusters that appear during receptor endocytosis, a well-established approach. Our assay, referred to as 'Total Grey Value per Cell' (TGVC), measures the total fluorescence above background, normalized to cell count. 3. Incubation with the cannabinoid agonist HU-210 (100 nmol/L) resulted in rapid CB1 internalization, reaching a maximum within 20 min. Whether quantified by Granularity or TGVC, the time-course of endocytosis could be modelled with exponentially derived curves and with similar half-lives. We demonstrate the sensitivity of our TGVC method by measuring the concentration dependence of CB1 internalization and its versatility by measuring downregulation following chronic agonist exposure, whereby total CB1 was reduced to approximately 55% of basal after 3 h. 4. The TGVC quantification method described is efficient, accurate and versatile and is likely to provide a valuable tool in receptor trafficking studies.
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Affiliation(s)
- Natasha L Grimsey
- Department of Pharmacology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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9
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Abstract
The hyperactivity of the brain renin-angiotensin system (RAS) has been implicated in the development and maintenance of hypertension in several types of experimental and genetic hypertension animal models. Among the main bioactive peptides of the brain RAS, angiotensin (Ang) II and Ang III display the same affinity for type 1 and type 2 Ang II receptors. Both peptides, injected intracerebroventricularly, similarly increase arginine vasopressin (AVP) release and blood pressure (BP); however, because Ang II is converted in vivo to Ang III, the identity of the true effector is unknown. We review new insights into the predominant role of brain Ang III in the control of BP, underlining the fact that brain aminopeptidase A (APA), the enzyme generating brain Ang III, may therefore be an interesting candidate target for the treatment of hypertension. This justifies the development of potent systemically active APA inhibitors, such as RB150, as prototypes of a new class of antihypertensive agents for the treatment of certain forms of hypertension. We also searched for a putative angiotensin receptor subtype specific for Ang III and isolated a seven transmembrane-domain G protein-coupled receptor corresponding to the receptor for apelin, a newly-discovered peptide isolated from bovine stomach. Apelin and its receptor are expressed in magnocellular vasopressinergic neurones in the hypothalamus. The central injection of apelin in lactating rats decreases the phasic electrical activity of vasopressinergic neurones and the systemic secretion of AVP, inducing water diuresis. Apelin is therefore a natural inhibitor of the antidiuretic effect of AVP. In addition, systemic administration of apelin decreases BP, improves cardiac contractility and reduces cardiac loading. The development of nonpeptide agonists of the apelin receptor may provide new therapeutic tools for treating water retention, hyponatraemia and cardiovascular diseases. Angiotensins and apelin thus exert opposing but complementary effects, and are thereby determinant for the maintenance of body fluid homeostasis and cardiovascular functions.
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10
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Goulpeau J, Lonetti B, Trouchet D, Ajdari A, Tabeling P. Building up longitudinal concentration gradients in shallow microchannels. LAB ON A CHIP 2007; 7:1154-61. [PMID: 17713614 DOI: 10.1039/b706340g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We demonstrate a compact and low consumption (60 nL) method for generating concentration gradients along microchannels with shallow parabolic cross-sections. The regimes of dispersion at work in such systems and the resulting concentration fields are described theoretically and experimentally. Experiments are performed in PDMS (polydimethylsiloxane) microchannels actuated by integrated valves. Detailed comparison between theory and experiment for the "short time" and "long time" regimes leads to excellent agreement. The system is used to successfully set up a series of isolated microchambers with mixtures of increasing solute concentrations, which may be a first step towards devices for screening.
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Affiliation(s)
- Jacques Goulpeau
- Théorie et Microfluidique, CNRS-ESPCI UMR 7083, 10 rue vauquelin, 75005 Paris, France.
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11
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Mazella J, Vincent JP. Internalization and recycling properties of neurotensin receptors. Peptides 2006; 27:2488-92. [PMID: 16901585 DOI: 10.1016/j.peptides.2006.02.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Accepted: 02/12/2006] [Indexed: 11/16/2022]
Abstract
The targeting, internalization and recycling of membrane receptors in response to extracellular ligands involve a series of molecular mechanisms which are beginning to be better understood. The receptor-dependent internalization of neurotensin has been widely investigated using endogenous or heterologous receptor expression systems. This review focuses on the general properties of neurotensin sequestration and on the characterization of the receptors involved in this process.
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Affiliation(s)
- Jean Mazella
- Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097 du Centre National de la Recherche Scientifique, et de l'Université de Nice-Sophia Antipolis, Sophia Antipolis, 06560 Valbonne, France.
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12
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Savdie C, Ferguson SSG, Vincent JP, Beaudet A, Stroh T. Cell-type-specific pathways of neurotensin endocytosis. Cell Tissue Res 2005; 324:69-85. [PMID: 16374621 DOI: 10.1007/s00441-005-0102-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Accepted: 10/18/2005] [Indexed: 12/01/2022]
Abstract
The neurotensin receptor subtype 1 (NTS1) is a G-protein-coupled receptor (GPCR) mediating a large number of central and peripheral effects of neurotensin. Upon stimulation, NTS1 is rapidly internalized and targeted to lysosomes. This process depends on the interaction of the phosphorylated receptor with beta-arrestin. Little is known about other accessory endocytic proteins potentially involved. Here, we investigated the involvement of dynamin, amphiphysin, and intersectin in the internalization of NTS1 receptor-ligand complexes in transfected COS-7 and HEK 293 cells, by using the transferrin receptor as an internal control for the constitutive endocytic pathway. We found that NTS1 endocytosis was not only arrestin-dependent, but also dynamin-dependent in both COS-7 and HEK 293 cells, whereas internalization of the transferrin receptor was independent of arrestin but required dynamin. Overexpression of the SH3 domain of amphiphysin II had no effect on receptor internalization in either cell type. By contrast, overexpression of full-length intersectin or of its SH3 domain (but not of its EH domain) inhibited NTS1 internalization in COS-7 but not in HEK 293 cells. This difference between COS-7 and HEK 293 cells was not attributable to differences in endogenous intersectin levels between the two cell lines. Indeed, the same constructs inhibited transferrin endocytosis equally well in COS-7 and HEK 293 cells. However, immunogold electron microscopy revealed that internalized NTS1 receptors were associated with clathrin-coated pits in COS-7 cells but with smooth vesicles in HEK 293 cells, suggesting that NTS1 internalization proceeds via different endocytic pathways in these two cell types.
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Affiliation(s)
- Cheryl Savdie
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montréal, Québec, Canada
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13
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Arun KHS, Kaul CL, Ramarao P. Green fluorescent proteins in receptor research: An emerging tool for drug discovery. J Pharmacol Toxicol Methods 2005; 51:1-23. [PMID: 15596111 DOI: 10.1016/j.vascn.2004.07.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Accepted: 07/27/2004] [Indexed: 01/20/2023]
Abstract
In the last five years, green fluorescent protein (GFP) has emerged from being a mere curiosity to become a reliable tool for molecular pharmacological research. GFP produces an intense and stable green fluorescence noncatalytically by absorbing blue light maximally at 395 nm and emitting green light with a peak at 509 nm. It consists of 238 amino acids and its molecular mass is 27-30 kDa. GFP fluorescence occurs without cofactors and this property allows GFP fluorescence to be utilised in nonnative organisms, wherein it can be used as a reporter. This use of GFP permits real-time analysis of receptor dynamics. The emitted fluorescence can be used as a nontoxic marker and detected using fluorescence-activated cell sorting (FACS), thus avoiding any staining procedure, expensive mRNA analysis or hazardous radiolabeled binding assays. The potential value of GFP has also been recognized in orphan receptor research, where various GFP-tagged therapeutic proteins have been constructed in an attempt to identify the endogenous ligand(s). These chimeric proteins have been used to determine the site and time course of receptor expression and to relate receptor dynamics with therapeutic outcome. The preparation of new GFP constructs for identifying germ layer cells (endodermal, ectodermal, and mesodermal), as well as neuronal, haematopoietic, endothelial, and cartilage cells, has provided a useful battery of tissue/receptor-specific screening assays for new chemical entities. Genetically engineered cells with GFP expression have provided a valuable tool for automated analysis, and can be adapted for high-throughput systems. GFP is being increasingly utilised for the study of receptor dynamics, where, having already proved beneficial, it will likely continue to contribute towards the search for new classes of drugs, as well as to "de-orphaning" orphan receptors.
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Affiliation(s)
- K H S Arun
- Cardiovascular and Receptorology Laboratory, Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Phase-X, Sector 67, S.A.S. Nagar (Mohali)-160 062, Punjab, India
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14
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De Mota N, Reaux-Le Goazigo A, El Messari S, Chartrel N, Roesch D, Dujardin C, Kordon C, Vaudry H, Moos F, Llorens-Cortes C. Apelin, a potent diuretic neuropeptide counteracting vasopressin actions through inhibition of vasopressin neuron activity and vasopressin release. Proc Natl Acad Sci U S A 2004; 101:10464-9. [PMID: 15231996 PMCID: PMC478592 DOI: 10.1073/pnas.0403518101] [Citation(s) in RCA: 263] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Indexed: 11/18/2022] Open
Abstract
Apelin, a recently isolated neuropeptide that is expressed in the supraoptic and the paraventricular nuclei, acts on specific receptors located on vasopressinergic neurons. The increased phasic pattern of these neurons facilitates sustained antidiuresis during dehydration or lactation. Here, we investigated whether apelin interacts with arginine vasopressin (AVP) to maintain body fluid homeostasis. We first characterized the predominant molecular forms of endogenous hypothalamic and plasma apelin as corresponding to apelin 13 and, to a lesser extent, to apelin 17. We then demonstrated that, in lactating rats, apelin was colocalized with AVP in supraoptic nucleus magnocellular neurons and given intracerebroventricularly inhibited the phasic electrical activity of AVP neurons. In lactating mice, intracerebroventricular administration of apelin 17 reduced plasma AVP levels and increased diuresis. Moreover, water deprivation, which increases systemic AVP release and causes depletion of hypothalamic AVP stores, decreased plasma apelin concentrations and induced hypothalamic accumulation of the peptide, indicating that AVP and apelin are conversely regulated to facilitate systemic AVP release and suppress diuresis. Opposite effects of AVP and apelin are likely to occur at the hypothalamic level through autocrine modulation of the phasic electrical activity of AVP neurons. Altogether, these data demonstrate that apelin acts as a potent diuretic neuropeptide counteracting AVP actions through inhibition of AVP neuron activity and AVP release. The coexistence of apelin and AVP in magnocellular neurons, their opposite biological effects, and regulation are likely to play a key role for maintaining body fluid homeostasis.
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Affiliation(s)
- Nadia De Mota
- Institut National de la Santé et de la Recherche Médicale, Unité 36, Collège de France, 75231 Paris, France
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15
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Leterrier C, Bonnard D, Carrel D, Rossier J, Lenkei Z. Constitutive endocytic cycle of the CB1 cannabinoid receptor. J Biol Chem 2004; 279:36013-21. [PMID: 15210689 DOI: 10.1074/jbc.m403990200] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The CB1 cannabinoid receptor (CB1R) displays a significant level of ligand-independent (i.e. constitutive) activity, either when heterologously expressed in nonneuronal cells or in neurons where CB1Rs are endogenous. The present study investigates the consequences of constitutive activity on the intracellular trafficking of CB1R. When transfected in HEK-293 cells, CB1R is present at the plasma membrane, but a substantial proportion ( approximately 85%) of receptors is localized in intracellular vesicles. Detailed analysis of CB1-EGFP expressed in HEK-293 cells shows that the intracellular CB1R population is mostly of endocytic origin and that treatment with inverse agonist AM281 traps CB1R at the plasma membrane through a monensin-sensitive recycling pathway. Co-transfection with dominant positive or dominant negative mutants of the small GTPases Rab5 and Rab4, but not Rab11, profoundly modifies the steady-state and ligand-induced intracellular distribution of CB1R, indicating that constitutive endocytosis is Rab5-dependent, whereas constitutive recycling is mediated by Rab4. In conclusion, our results indicate that, due to its natural constitutive activity, CB1R permanently and constitutively cycles between plasma membrane and endosomes, leading to a predominantly intracellular localization at steady state.
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Affiliation(s)
- Christophe Leterrier
- ESPCI-CNRS UMR 7637, Laboratoire Neurobiologie et Diversité Cellulaire, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75231 Paris Cedex 05, France
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Camiña JP, Carreira MC, El Messari S, Llorens-Cortes C, Smith RG, Casanueva FF. Desensitization and endocytosis mechanisms of ghrelin-activated growth hormone secretagogue receptor 1a. Endocrinology 2004; 145:930-40. [PMID: 14576181 DOI: 10.1210/en.2003-0974] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In this study, a sequential analysis of pathways involved in the regulation of GH secretagogue receptor subtype 1a (GHSR-1a) signaling has been undertaken to characterize the process of rapid desensitization that is observed after ghrelin binding. This process was evaluated by studying the binding of [(125)I]ghrelin, measurement of intracellular calcium mobilization, and confocal microscopy. The results indicate that GHSR-1a is mainly localized at the plasma membrane under unstimulated conditions and rapidly desensitizes after stimulation. The agonist-dependent desensitization is not mediated by protein kinase C because phorbol ester, phorbol-12-myristate-13-acetate, failed to block the ghrelin-induced calcium response. The ghrelin/GHSR-1a complex progressively disappears from the plasma membrane after 20 min exposure to ghrelin and accumulates in the perinuclear region after 60 min. Colocalization of the internalized GHSR-1a with the early endosome marker (EEA1) after 20 min exposure to ghrelin suggests that endocytosis occurs via clathrin-coated pits, which is consistent with the lack of internalization of this receptor observed after potassium depletion. Different from other G protein-coupled receptors, GHSR-1a showed slow recycling. Surface binding slowly recovered after agonist treatment and returned to control levels within 360 min. Furthermore, inhibition of vacuolar H(+)-ATPases prevented recycling of the receptor, suggesting that the nondissociation of the ligand/receptor complex is responsible for this effect. The GHSR-1a internalization may explain the characteristic physiological responses mediated by this receptor.
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Affiliation(s)
- Jesus P Camiña
- Molecular and Cellular Endocrinology Laboratory, Department of Medicine, Complejo Hospitalario Universitario de Santiago-Universidad de Santiago de Compostela, P.O. Box 56, E-15780 Santiago de Compostela, Spain
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Toy-Miou-Leong M, Cortes CL, Beaudet A, Rostène W, Forgez P. Receptor trafficking via the perinuclear recycling compartment accompanied by cell division is necessary for permanent neurotensin cell sensitization and leads to chronic mitogen-activated protein kinase activation. J Biol Chem 2003; 279:12636-46. [PMID: 14699144 DOI: 10.1074/jbc.m303384200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Most G protein-coupled receptors are internalized after interaction with their respective ligand, a process that subsequently contributes to cell desensitization, receptor endocytosis, trafficking, and finally cell resensitization. Although cellular mechanisms leading to cell desensitization have been widely studied, those responsible for cell resensitization are still poorly understood. We examined here the traffic of the high affinity neurotensin receptor (NT1 receptor) following prolonged exposure to high agonist concentration. Fluorescence and confocal microscopy of Chinese hamster ovary, human neuroblastoma (CHP 212), and murine neuroblastoma (N1E-115) cells expressing green fluorescent protein-tagged NT1 receptor revealed that under prolonged treatment with saturating concentrations of neurotensin (NT) agonist, NT1 receptor and NT transiently accumulated in the perinuclear recycling compartment (PNRC). During this cellular event, cell surface receptors remained markedly depleted as detected by both confocal microscopy and (125)I-NT binding assays. In dividing cells, we observed that following prolonged NT agonist stimulation, NT1 receptors were removed from the PNRC, accumulated in dispersed vesicles inside the cytoplasm, and subsequently reappeared at the cell surface. This NT binding recovery allowed for constant cell sensitization and led to a chronic activation of mitogen-activated protein kinases p42 and p44. Under these conditions, the constant activation of NT1 receptor generates an oncogenic regulation. These observations support the potent role for neuropeptides, such as NT, in cancer progression.
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Affiliation(s)
- Mireille Toy-Miou-Leong
- INSERM Unit 482, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, 75012 Paris, France
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Kotarsky K, Nilsson NE, Olde B, Owman C. Progress in Methodology Improved Reporter Gene Assays Used to Identify Ligands Acting on Orphan Seven-Transmembrane Receptors. ACTA ACUST UNITED AC 2003; 93:249-58. [PMID: 14675457 DOI: 10.1111/j.1600-0773.2003.pto930601.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Seven-transmembrane G-protein-coupled receptors play a central role in physiology by facilitating cell communication through recognition of a wide range of ligands. Even more important, they represent important drug targets. Unfortunately, for many of these receptors the endogenous ligands, and hence their functions, remain to be identified. These receptors are referred to as "orphan" receptors. A pre-requisite for the identification of ligands activating orphan receptors is powerful assay systems. Until now, reporter gene assays have not been in common use in this process. Here, we summarize our development of improved reporter gene assays. We optimized reporter gene assays in respect of (i) the promoter region of the construct, (ii) the reporter enzyme used, (iii) and the assay procedure. Furthermore, an unique fluorescence-based clone selection step was introduced, allowing rapid selection of the most sensitive reporter cell clones when establishing stable reporter cell lines. Mathematical formulae are provided to enable a simple and reliable comparison between different cell lines, when tested with a compound of interest. The resulting reporter cell lines responded in a very sensitive way to the stimulation of various test receptors. The reporter system was termed HighTRACE (high-throughput reporter assay with clone election). Its high assay quality makes it suitable as a primary screening tool. Ligands for two recently unknown 7TM receptors were identified using the HighTRACE system i.e., two cell surface free fatty acid receptors, GPR40 (FFA1R) and GPR43 (FFA2R). The identification was accomplished using a reverse pharmacology approach.
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Affiliation(s)
- Knut Kotarsky
- Division of Molecular Neurobiology, Department of Physiological Sciences, Wallenberg Neuroscience Center, S-221 84 Lund, Sweden
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Kline TR, Pang J, Hefta SA, Opiteck GJ, Kiefer SE, Scheffler JE. A high-yield method to extract peptides from rat brain tissue. Anal Biochem 2003; 315:183-8. [PMID: 12689828 DOI: 10.1016/s0003-2697(03)00027-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A process to extract and enrich extracellular peptides and proteins from tissues should have broad utility in the burgeoning proteomics field. To address this need, a novel three-step protocol was developed to extract polypeptides from whole tissue samples and enrich the extracellular components. The initial homogenization of rat brain was carried out at neutral pH to optimize protein and peptide stability and solubility. Subsequent covalent chromatography on an activated thiopropyl resin was employed to debulk the tissue extract by selectively removing a substantial fraction of the intracellular protein component under nondenaturing conditions. Finally, extraction with 0.1% trifluoroacetic acid was used to selectively precipitate large proteins while enhancing the solubility of smaller proteins and peptides. The fractions from each step in the process were compared to a single extract obtained by homogenization in 0.5 M acetic acid. The recovery and yields of endogenous neuropeptides and an exogenously added peptide were evaluated by enzyme immunoassay and Western blotting, respectively. In summary, the three-step protocol was superior to the extraction of tissue with 0.5 M acetic acid in terms of peptide recovery, enrichment, and sample stability. Enrichment of the extracellular protein compartment from tissues should be valuable in proteomics experiments aimed at identifying biomarkers that can partition into serum.
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Affiliation(s)
- Tiffany R Kline
- Department of Proteomics, Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 5400, Princeton, NJ 08543-5400, USA
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Miserey-Lenkei S, Parnot C, Bardin S, Corvol P, Clauser E. Constitutive internalization of constitutively active agiotensin II AT(1A) receptor mutants is blocked by inverse agonists. J Biol Chem 2002; 277:5891-901. [PMID: 11729186 DOI: 10.1074/jbc.m108398200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As constitutively active mutants (CAMs) mimic an active conformation, they can be used to characterize the process of G protein-coupled receptor activation. Here, we used CAMs to study the link between activation and internalization of the angiotensin II AT(1A) receptor. The cellular localization of fluorescently tagged N111A, I245T, and L305Q mutants was determined by confocal microscopy. In the absence of ligand, CAMs were mostly located in intracellular vesicles, whereas the wild-type AT(1A) was found at the cell surface. After 2 h incubation with inverse agonist, losartan, CAMs were translocated to the plasma membrane. Similar observations were made in H295, a human adrenocortical cell line which expresses physiologically the AT(1) receptor. This phenomenon, which was not dependent on protein synthesis and the pharmacology and kinetics of which were similar to the recycling of the wild-type receptor, was called "externalization". After externalization and losartan removal, the L305Q CAM underwent rapid ligand-independent endocytosis, with the same kinetics and temperature sensitivity as the angiotensin II-induced internalization of the wild-type AT(1A). Moreover, the addition of a second mutation known to block internalization (Delta 329 truncation) prevented intracellular localization of the CAM. These data show that AT(1A) CAMs are constitutively and permanently internalized and recycled. This mechanism is different from the down-regulation observed for CAMs of other G protein-coupled receptors and thus defines a new paradigm for the cellular regulation of CAMs.
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Reaux A, De Mota N, Skultetyova I, Lenkei Z, El Messari S, Gallatz K, Corvol P, Palkovits M, Llorens-Cortès C. Physiological role of a novel neuropeptide, apelin, and its receptor in the rat brain. J Neurochem 2001; 77:1085-96. [PMID: 11359874 DOI: 10.1046/j.1471-4159.2001.00320.x] [Citation(s) in RCA: 282] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Apelin, a peptide recently isolated from bovine stomach tissue extracts, has been identified as the endogenous ligand of the human orphan APJ receptor. We established a stable Chinese hamster ovary (CHO) cell line expressing a gene encoding the rat apelin receptor fused to the enhanced green fluorescent protein, to investigate internalization and the pharmacological profile of the apelin receptor. Stimulation of this receptor by the apelin fragments K17F (Lys1-Phe-Arg-Arg-Gln-Arg-Pro-Arg-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) and pE13F (pGlu5-Arg-Pro-Arg-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) resulted in a dose-dependent inhibition of forskolin-induced cAMP production and promoted its internalization. In contrast, the apelin fragments R10F (Arg8-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) and G5F (Gly13-Pro-Met-Pro-Phe17) were inactive. The physiological role of apelin and its receptor was then investigated by showing for the first time in rodent brain: (i) detection of apelin neurons in the supraoptic and paraventricular nuclei by immunohistochemistry with a specific polyclonal anti-apelin K17F antibody; (ii) detection of apelin receptor mRNA in supraoptic vasopressinergic neurons by in situ hybridization and immunohistochemistry; and (iii) a decrease in vasopressin release following intracerebroventricular injection of K17F, or pE13F, but not R10F. Thus, apelin locally synthesized in the supraoptic nucleus could exert a direct inhibitory action on vasopressinergic neuron activity via the apelin receptors synthesized in these cells. Furthermore, central injection of pE13F significantly decreased water intake in dehydrated normotensive rats but did not affect blood pressure. Together, these results suggest that neuronal apelin plays an important role in the central control of body fluid homeostasis.
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Affiliation(s)
- A Reaux
- Institut National de la Santé et de la Recherche Médicale, Paris, France Laboratory of Neuromorphology, Faculty of Medicine Semmelweis University, Budapest, Hungary
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