1
|
Işbilir A, Serfling R, Möller J, Thomas R, De Faveri C, Zabel U, Scarselli M, Beck-Sickinger AG, Bock A, Coin I, Lohse MJ, Annibale P. Determination of G-protein-coupled receptor oligomerization by molecular brightness analyses in single cells. Nat Protoc 2021; 16:1419-1451. [PMID: 33514946 DOI: 10.1038/s41596-020-00458-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 11/03/2020] [Indexed: 02/08/2023]
Abstract
Oligomerization of membrane proteins has received intense research interest because of their importance in cellular signaling and the large pharmacological and clinical potential this offers. Fluorescence imaging methods are emerging as a valid tool to quantify membrane protein oligomerization at high spatial and temporal resolution. Here, we provide a detailed protocol for an image-based method to determine the number and oligomerization state of fluorescently labeled prototypical G-protein-coupled receptors (GPCRs) on the basis of small out-of-equilibrium fluctuations in fluorescence (i.e., molecular brightness) in single cells. The protocol provides a step-by-step procedure that includes instructions for (i) a flexible labeling strategy for the protein of interest (using fluorescent proteins, small self-labeling tags or bio-orthogonal labeling) and the appropriate controls, (ii) performing temporal and spatial brightness image acquisition on a confocal microscope and (iii) analyzing and interpreting the data, excluding clusters and intensity hot-spots commonly observed in receptor distributions. Although specifically tailored for GPCRs, this protocol can be applied to diverse classes of membrane proteins of interest. The complete protocol can be implemented in 1 month.
Collapse
Affiliation(s)
- Ali Işbilir
- Max Delbrück Center for Molecular Medicine, Berlin, Germany.,Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | - Robert Serfling
- Institute of Biochemistry, Faculty of Life Sciences, University of Leipzig, Leipzig, Germany
| | - Jan Möller
- Max Delbrück Center for Molecular Medicine, Berlin, Germany.,Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | - Romy Thomas
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Chiara De Faveri
- Institute of Biochemistry, Faculty of Life Sciences, University of Leipzig, Leipzig, Germany
| | - Ulrike Zabel
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | - Marco Scarselli
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | | | - Andreas Bock
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Irene Coin
- Institute of Biochemistry, Faculty of Life Sciences, University of Leipzig, Leipzig, Germany
| | - Martin J Lohse
- Max Delbrück Center for Molecular Medicine, Berlin, Germany. .,Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany. .,ISAR Bioscience Institute, Munich, Germany.
| | - Paolo Annibale
- Max Delbrück Center for Molecular Medicine, Berlin, Germany.
| |
Collapse
|
2
|
Lesiak L, Zhou X, Fang Y, Zhao J, Beck JR, Stains CI. Imaging GPCR internalization using near-infrared Nebraska red-based reagents. Org Biomol Chem 2020; 18:2459-2467. [PMID: 32167123 DOI: 10.1039/d0ob00043d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Internalization of G protein-coupled receptor (GPCRs) represents a nearly universal pathway for receptor downregulation. Imaging this process provides a means for the identification of pharmaceutical agents as well as potential ligands for orphan receptors. However, there is a need for the further development of near-infrared (NIR) probes capable of monitoring internalization in order to enable multiplexing with existing green fluorescent GPCR activity assays. Our laboratory has recently described a series of near-infrared (NIR) fluorophores in which a phosphinate functionality is inserted at the bridging position of the xanthene scaffold. These fluorophores, termed Nebraska Red (NR) dyes, provide attractive reagents for imaging protein localization. Herein, we disclose the development of NR-based HaloTag ligands for imaging membrane proteins on living cells. These new probes are utilized to image membrane pools of the human orexin type 2 receptor, an established target for the treatment of insomnia. We demonstrate the ability of fetal bovine serum (FBS) to noncovalently associate with a spirolactonized NR probe, enabling no-wash imaging with a 45-fold enhancement of fluorescence. Furthermore, we characterize the utility of NR-based HaloTag ligands for real-time monitoring of receptor internalization upon agonist stimulation. These new reagents enable potential multiplexing with existing GPCR activity assays in order to identify new modulators of GPCR activity as well as ligands for orphan receptors.
Collapse
Affiliation(s)
- Lauren Lesiak
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA.
| | - Xinqi Zhou
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA.
| | - Yuan Fang
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA. and Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Jia Zhao
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA.
| | - Jon R Beck
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA.
| | - Cliff I Stains
- Department of Chemistry, University of Nebraska - Lincoln, Lincoln, NE 68588, USA. and Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA and Nebraska Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, NE 68588, USA and Cancer Genes and Molecular Regulation Program, Fred & Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| |
Collapse
|
3
|
Li Y, Cui ZJ. Photodynamic Activation of Cholecystokinin 1 Receptor with Different Genetically Encoded Protein Photosensitizers and from Varied Subcellular Sites. Biomolecules 2020; 10:biom10101423. [PMID: 33050050 PMCID: PMC7601527 DOI: 10.3390/biom10101423] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 10/01/2020] [Accepted: 10/06/2020] [Indexed: 02/07/2023] Open
Abstract
Cholecystokinin 1 receptor (CCK1R) is activated by singlet oxygen (1O2) generated in photodynamic action with sulphonated aluminum phthalocyanine (SALPC) or genetically encoded protein photosensitizer (GEPP) KillerRed or mini singlet oxygen generator (miniSOG). A large number of GEPP with varied 1O2 quantum yields have appeared recently; therefore, in the present work, the efficacy of different GEPP to photodynamically activate CCK1R was examined, as monitored by Fura-2 calcium imaging. KillerRed, miniSOG, miniSOG2, singlet oxygen protein photosensitizer (SOPP), flavin-binding fluorescent protein from Methylobacterium radiotolerans with point mutation C71G (Mr4511C71G), and flavin-binding fluorescent protein from Dinoroseobacter shibae (DsFbFP) were expressed at the plasma membrane (PM) in AR4-2J cells, which express endogenous CCK1R. Light irradiation (KillerRed: white light 85.3 mW‧cm-2, 4' and all others: LED 450 nm, 85 mW·cm-2, 1.5') of GEPPPM-expressing AR4-2J was found to all trigger persistent calcium oscillations, a hallmark of permanent photodynamic CCK1R activation; DsFbFP was the least effective, due to poor expression. miniSOG was targeted to PM, mitochondria (MT) or lysosomes (LS) in AR4-2J in parallel experiments; LED light irradiation was found to all induce persistent calcium oscillations. In miniSOGPM-AR4-2J cells, light emitting diode (LED) light irradiation-induced calcium oscillations were readily inhibited by CCK1R antagonist devazepide 2 nM; miniSOGMT-AR4-2J cells were less susceptible, but miniSOGLS-AR4-2J cells were not inhibited. In conclusion, different GEPPPM could all photodynamically activate CCK1R. Intracellular GEPP photodynamic action may prove particularly suited to study intracellular GPCR.
Collapse
|
4
|
Bi X, Yin J, Zhang D, Zhang X, Balamkundu S, Lescar J, Dedon PC, Tam JP, Liu CF. Tagging Transferrin Receptor with a Disulfide FRET Probe To Gauge the Redox State in Endosomal Compartments. Anal Chem 2020; 92:12460-12466. [DOI: 10.1021/acs.analchem.0c02264] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Xiaobao Bi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Juan Yin
- Program in Neuroscience and Behavioural Disorders, Duke-NUS Medical School, 8 College Road, Singapore169857, Singapore
| | - Dingpeng Zhang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Xiaohong Zhang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Seetharamsing Balamkundu
- Singapore-MIT Alliance for Research and Technology Centre, 1 Create Way, #10-01 Create Tower, Singapore 138602, Singapore
| | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Peter C. Dedon
- Singapore-MIT Alliance for Research and Technology Centre, 1 Create Way, #10-01 Create Tower, Singapore 138602, Singapore
| | - James P. Tam
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Chuan-Fa Liu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| |
Collapse
|
5
|
Synthesis and biological evaluation of fluorescent GAT-ligands based on asymmetric substituted BODIPY dyes. Med Chem Res 2020. [DOI: 10.1007/s00044-020-02521-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
6
|
14-3-3 signal adaptor and scaffold proteins mediate GPCR trafficking. Sci Rep 2019; 9:11156. [PMID: 31371790 PMCID: PMC6673703 DOI: 10.1038/s41598-019-47478-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 07/18/2019] [Indexed: 11/09/2022] Open
Abstract
Receptor trafficking is pivotal for the temporal and spatial control of GPCR signaling and is regulated by multiple cellular proteins. We provide evidence that GPCRs interact with 14-3-3 signal adaptor/scaffold proteins and that this interaction regulates receptor trafficking in two ways. We found GPCR/14-3-3 interaction signals can be agonist-induced or agonist-inhibited. Some GPCRs associate with 14-3-3 proteins at the cell membrane and agonist treatments result in disrupted GPCR/14-3-3 interaction signals. The diminished GPCR/14-3-3 interaction signals are temporally correlated with increased GPCR/β-arrestin interaction signals in response to agonist treatment. Other GPCRs showed agonist-induced GPCR/14-3-3 interaction signal increases that occur later than agonist-induced GPCR/β-arrestin interaction signals, indicating that GPCR/14-3-3 interaction occurred after receptor endocytosis. These two types of GPCR/14-3-3 interaction patterns correlate with different receptor trafficking patterns. In addition, the bioinformatic analysis predicts that approximately 90% of GPCRs contain at least one putative 14-3-3 binding motif, suggesting GPCR/14-3-3 association could be a general phenomenon. Based on these results and collective evidence, we propose a working model whereby 14-3-3 serves as a sorting factor to regulate receptor trafficking.
Collapse
|
7
|
Chen X, Chen J, Fu R, Rao P, Weller R, Bradshaw J, Liu S. Can the Cellular Internalization of Cargo Proteins Be Enhanced by Fusing a Tat Peptide in the Center of Proteins? A Fluorescence Study. J Pharm Sci 2018; 107:879-886. [DOI: 10.1016/j.xphs.2017.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/31/2017] [Accepted: 11/01/2017] [Indexed: 11/27/2022]
|
8
|
Scaglione A, Montemiglio LC, Parisi G, Asteriti IA, Bruni R, Cerutti G, Testi C, Savino C, Mancia F, Lavia P, Vallone B. Subcellular localization of the five members of the human steroid 5α-reductase family. BIOCHIMIE OPEN 2017; 4:99-106. [PMID: 29082129 PMCID: PMC5656259 DOI: 10.1016/j.biopen.2017.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In humans the steroid 5α-reductase (SRD5A) family comprises five integral membrane enzymes that carry out reduction of a double bond in lipidic substrates: Δ4-3-keto steroids, polyprenol and trans-enoyl CoA. The best-characterized reaction is the conversion of testosterone into the more potent dihydrotestosterone carried out by SRD5A1-2. Some controversy exists on their possible nuclear or endoplasmic reticulum localization. We report the cloning and transient expression in HeLa cells of the five members of the human steroid 5α-reductase family as both N- and C-terminus green fluorescent protein tagged protein constructs. Following the intrinsic fluorescence of the tag, we have determined that the subcellular localization of these enzymes is in the endoplasmic reticulum, upon expression in HeLa cells. The presence of the tag at either end of the polypeptide chain can affect protein expression and, in the case of trans enoyl-CoA reductase, it induces the formation of protein aggregates. All members of human testosterone 5α-reductase family were expressed in HeLa cells. Subcellular localization of SRD5A proteins in the endoplasmic reticulum is reported. The effect of GFP tagging at N- or C-term on SRD5A proteins expression was assessed. The TECRL gene is expressed for the first time and its product localizes in the ER.
Collapse
Affiliation(s)
- Antonella Scaglione
- Dept. of Biochemical Sciences, Sapienza University of Rome, P.le A.Moro 5, 00185, Rome, Italy
| | - Linda Celeste Montemiglio
- Dept. of Biochemical Sciences, Sapienza University of Rome, P.le A.Moro 5, 00185, Rome, Italy.,Istituto Pasteur-Fondazione Cenci Bolognetti Dept. of Biochemical Sciences, Sapienza University of Rome
| | - Giacomo Parisi
- Dept. of Biochemical Sciences, Sapienza University of Rome, P.le A.Moro 5, 00185, Rome, Italy
| | | | - Renato Bruni
- New York Consortium on Membrane Protein Structure, New York, NY 10027, USA
| | - Gabriele Cerutti
- Dept. of Biochemical Sciences, Sapienza University of Rome, P.le A.Moro 5, 00185, Rome, Italy
| | - Claudia Testi
- Center for Life Nano Science@Sapienza, IIT, V.le Regina Elena 291, Rome I-00185, Italy
| | | | - Filippo Mancia
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | | | - Beatrice Vallone
- Dept. of Biochemical Sciences, Sapienza University of Rome, P.le A.Moro 5, 00185, Rome, Italy.,Istituto Pasteur-Fondazione Cenci Bolognetti Dept. of Biochemical Sciences, Sapienza University of Rome.,Schaefer Research Scholar at Columbia University and Fellow of the Italian Academy for Advanced Studies in America at Columbia University
| |
Collapse
|
9
|
Hunyady L, Gáborik Z, Vauquelin G, Catt KJ. Review: Structural requirements for signalling and regulation of AT1-receptors. J Renin Angiotensin Aldosterone Syst 2016; 2:S16-S23. [DOI: 10.1177/14703203010020010301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Affiliation(s)
- László Hunyady
- Department of Physiology, Semmelweis University Medical
School, Budapest, Hungary,
| | - Zsuzsanna Gáborik
- Department of Physiology, Semmelweis University Medical
School, Budapest, Hungary
| | - Georges Vauquelin
- Department of Molecular and Biochemical Pharmacology,
Institute of Molecular Biology and Biotechnology, Free University of Brussels
(VUB), Sint-Genesius Rode, Belgium
| | - Kevin J Catt
- Endocrinology and Reproduction Research Branch, National
Institute of Child Health and Human Development, National Institutes of Health,
Bethesda, USA
| |
Collapse
|
10
|
Tian H, Fürstenberg A, Huber T. Labeling and Single-Molecule Methods To Monitor G Protein-Coupled Receptor Dynamics. Chem Rev 2016; 117:186-245. [DOI: 10.1021/acs.chemrev.6b00084] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- He Tian
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Alexandre Fürstenberg
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| | - Thomas Huber
- Laboratory of Chemical Biology
and Signal Transduction, The Rockefeller University, 1230 York
Avenue, New York, New York 10065, United States
| |
Collapse
|
11
|
He H, Wang X, Cheng T, Xia Y, Lao J, Ge B, Ren H, Khan NU, Huang F. An Ultra-High Fluorescence Enhancement and High Throughput Assay for Revealing Expression and Internalization of Chemokine Receptor CXCR4. Chemistry 2016; 22:5863-7. [DOI: 10.1002/chem.201600245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 01/30/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Hua He
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Xiaojuan Wang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Tiantian Cheng
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Yongqing Xia
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Jun Lao
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Baosheng Ge
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Hao Ren
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Naseer Ullah Khan
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology; China University of Petroleum (East China); Qingdao 266580 P. R. China
| |
Collapse
|
12
|
Gaudet HM, Cheng SB, Christensen EM, Filardo EJ. The G-protein coupled estrogen receptor, GPER: The inside and inside-out story. Mol Cell Endocrinol 2015; 418 Pt 3:207-19. [PMID: 26190834 DOI: 10.1016/j.mce.2015.07.016] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 07/15/2015] [Accepted: 07/15/2015] [Indexed: 02/06/2023]
Abstract
GPER possesses structural and functional characteristics shared by members of the G-protein-coupled receptor (GPCR) superfamily, the largest class of plasma membrane receptors. This newly appreciated estrogen receptor is localized predominately within intracellular membranes in most, but not all, cell types and its surface expression is modulated by steroid hormones and during tissue injury. An intracellular staining pattern is not unique among GPCRs, which employ a diverse array of molecular mechanisms that restrict cell surface expression and effectively regulating receptor binding and activation. The finding that GPER displays an intracellular predisposition has created some confusion as the estrogen-inducible transcription factors, ERα and ERβ, also reside intracellularly, and has led to complex suggestions of receptor interaction. GPER undergoes constitutive retrograde trafficking from the plasma membrane to the endoplasmic reticulum and recent studies indicate its interaction with PDZ binding proteins that sort transmembrane receptors to synaptosomes and endosomes. Genetic targeting and selective ligand approaches as well as cell models that express GPER in the absence of ERs clearly supports GPER as a bonafide "stand alone" receptor. Here, the molecular details that regulate GPER action, its cell biological activities and its implicated roles in physiological and pathological processes are reviewed.
Collapse
Affiliation(s)
- H M Gaudet
- Wheaton College, Department of Chemistry, Norton, MA, 02766, USA
| | - S B Cheng
- Women & Infants Hospital, Brown University, Providence, RI, 02903, USA
| | - E M Christensen
- Wheaton College, Department of Chemistry, Norton, MA, 02766, USA
| | - E J Filardo
- Rhode Island Hospital, Brown University, Providence, RI, 02903, USA.
| |
Collapse
|
13
|
Abstract
Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder that is characterized by intermittent abdominal pain/discomfort, altered bowel habits and abdominal bloating/distension. This review aimed at presenting the recent developments concerning the role of diet in the pathophysiology and management of IBS. There is no convincing evidence that IBS patients suffer from food allergy/intolerance, and there is no evidence that gluten causes the debated new diagnosis of non-coeliac gluten sensitivity (NCGS). The component in wheat that triggers symptoms in NCGS appears to be the carbohydrates. Patients with NCGS appear to be IBS patients who are self-diagnosed and self-treated with a gluten-free diet. IBS symptoms are triggered by the consumption of the poorly absorbed fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) and insoluble fibre. On reaching the distal small intestine and colon, FODMAPS and insoluble fibre increase the osmotic pressure in the large-intestine lumen and provide a substrate for bacterial fermentation, with consequent gas production, abdominal distension and abdominal pain or discomfort. Poor FODMAPS and insoluble fibres diet reduces the symptom and improve the quality of life in IBS patients. Moreover, it changes favourably the intestinal microbiota and restores the abnormalities in the gastrointestinal endocrine cells. Five gastrointestinal endocrine cell types that produce hormones regulating appetite and food intake are abnormal in IBS patients. Based on these hormonal abnormalities, one would expect that IBS patients to have increased food intake and body weight gain. However, the link between obesity and IBS is not fully studied. Individual dietary guidance for intake of poor FODMAPs and insoluble fibres diet in combination with probiotics intake and regular exercise is to be recommended for IBS patients.
Collapse
Affiliation(s)
- Magdy El-Salhy
- Department of Medicine, Section for Gastroenterology, Stord Hospital, Stord, Norway. .,Department of Clinical Medicine, Section for Gastroenterology, University of Bergen, Box 4000, 54 09, Stord, Norway. .,Department of Medicine, National Centre for Functional Gastrointestinal Disorders, Haukeland University Hospital, Bergen, Norway.
| | - Doris Gundersen
- Department of Research, Helse-Fonna, Haugesund Hospital, Haugesund, Norway.
| |
Collapse
|
14
|
Xu F, Luk CC, Wiersma-Meems R, Baehre K, Herman C, Zaidi W, Wong N, Syed NI. Neuronal somata and extrasomal compartments play distinct roles during synapse formation between Lymnaea neurons. J Neurosci 2014; 34:11304-15. [PMID: 25143611 PMCID: PMC6615512 DOI: 10.1523/jneurosci.1651-14.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/07/2014] [Accepted: 07/15/2014] [Indexed: 12/21/2022] Open
Abstract
Proper synapse formation is pivotal for all nervous system functions. However, the precise mechanisms remain elusive. Moreover, compared with the neuromuscular junction, steps regulating the synaptogenic program at central cholinergic synapses remain poorly defined. In this study, we identified different roles of neuronal compartments (somal vs extrasomal) in chemical and electrical synaptogenesis. Specifically, the electrically synapsed Lymnaea pedal dorsal A cluster neurons were used to study electrical synapses, whereas chemical synaptic partners, visceral dorsal 4 (presynaptic, cholinergic), and left pedal dorsal 1 (LPeD1; postsynaptic) were explored for chemical synapse formation. Neurons were cultured in a soma-soma or soma-axon configuration and synapses explored electrophysiologically. We provide the first direct evidence that electrical synapses develop in a soma-soma, but not soma-axon (removal of soma) configuration, indicating the requirement of gene transcription regulation in the somata of both synaptic partners. In addition, the soma-soma electrical coupling was contingent upon trophic factors present in Lymnaea brain-conditioned medium. Further, we demonstrate that chemical (cholinergic) synapses between soma-soma and soma-axon pairs were indistinguishable, with both exhibiting a high degree of contact site and target cell type specificity. We also provide direct evidence that presynaptic cell contact-mediated, clustering of postsynaptic cholinergic receptors at the synaptic site requires transmitter-receptor interaction, receptor internalization, and a protein kinase C-dependent lateral migration toward the contact site. This study provides novel insights into synaptogenesis between central neurons revealing both distinct and synergistic roles of cell-cell signaling and extrinsic trophic factors in executing the synaptogenic program.
Collapse
Affiliation(s)
- Fenglian Xu
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Collin C Luk
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Ryanne Wiersma-Meems
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Kelly Baehre
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Cameron Herman
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Wali Zaidi
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Noelle Wong
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| | - Naweed I Syed
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta T2N 4Z6, Canada
| |
Collapse
|
15
|
Beltran-Sastre V, Navarro E. Measuring activity of endocytosis-regulating factors in T-lymphocytes by flow cytometry. Cytotechnology 2014; 67:551-8. [PMID: 24504563 DOI: 10.1007/s10616-014-9696-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 01/24/2014] [Indexed: 11/25/2022] Open
Abstract
Elucidation of the mechanisms regulating membrane traffic of lymphocyte receptors is of great interest to manipulate the immune response, as well as for accurately delivering drugs and nanoprobes to cells. Aiming to detect and characterize regulators of endocytosis and intracellular traffic, we have modified the FACS-based endocytosis assay to measure and quantify the activity of putative endocytic regulators as EGFP chimeras. To study the activity of putative endocytosis regulators, we transfected Jurkat T-lymphocytes with EGFP-tagged constructs of the regulators to be tested. Cells were then incubated with a αCD3(APC) antibody, and were allowed to internalize the label. After acid-washing the cells, APC fluorescence was measured by flow cytometry in cells gated for EGFP(+), as well as in their EGFP(-) (transfection-resistant) counterparts that were taken as internal controls. This approach facilitated intra- and inter-assay normalization of endocytic rates/loads by comparison with the internal control. We have used this assay to test the regulatory activity of polarity kinase EMK1, and here we substantiate a role for EMK1 in the control of receptor internalization in T-lymphocytes. The method here presented gives quantitative measures of internalization, and will facilitate the development of tools to modulate endocytic rates or the intracellular fate of internalized materials.
Collapse
Affiliation(s)
- Violeta Beltran-Sastre
- Laboratori d'Oncologia Molecular (LOM), Bellvitge Research Institute (IDIBELL), Gran Via 199-203 Hospitalet de Llobregat, 08908, Barcelona, Spain
| | | |
Collapse
|
16
|
Abstract
This unit provides detailed protocols for measuring receptor internalization. The techniques are sufficiently generalized to be applicable to most receptors in a wide variety of cell types. Both radioactive and non-radioactive techniques are described that may be used to quantify receptor internalization, and the differences between the two are highlighted. This unit discusses how quantification of internalization may be achieved, and the advantages and drawbacks of each technique. Low- and higher-throughput methods are compared, and the technologies required to conduct the analyses are discussed.
Collapse
|
17
|
Conway BR, Demarest KT. The Use of Biosensors to Study GPCR Function: Applications for High-Content Screening. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820214641] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
18
|
Carrel D, Simon A, Emerit MB, Rivals I, Leterrier C, Biard M, Hamon M, Darmon M, Lenkei Z. Axonal Targeting of the 5-HT1B Serotonin Receptor Relies on Structure-Specific Constitutive Activation. Traffic 2011; 12:1501-20. [DOI: 10.1111/j.1600-0854.2011.01260.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
19
|
Cheng SB, Quinn JA, Graeber CT, Filardo EJ. Down-modulation of the G-protein-coupled estrogen receptor, GPER, from the cell surface occurs via a trans-Golgi-proteasome pathway. J Biol Chem 2011; 286:22441-55. [PMID: 21540189 PMCID: PMC3121390 DOI: 10.1074/jbc.m111.224071] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/26/2011] [Indexed: 11/06/2022] Open
Abstract
GPER is a G(s)-coupled seven-transmembrane receptor that has been linked to specific estrogen binding and signaling activities that are manifested by plasma membrane-associated enzymes. However, in many cell types, GPER is predominately localized to the endoplasmic reticulum (ER), and only minor amounts of receptor are detectable at the cell surface, an observation that has caused controversy regarding its role as a plasma membrane estrogen receptor. Here, we show that GPER constitutively buds intracellularly into EEA-1+ endosomes from clathrin-coated pits. Nonvisual arrestins-2/-3 do not co-localize with GPER, and expression of arrestin-2 dominant-negative mutants lacking clathrin- or β-adaptin interaction sites fails to block GPER internalization suggesting that arrestins are not involved in GPER endocytosis. Like β1AR, which recycles to the plasma membrane, GPER co-traffics with transferrin+, Rab11+ recycling endosomes. However, endocytosed GPER does not recycle to the cell surface, but instead returns to the trans-Golgi network (TGN) and does not re-enter the ER. GPER is ubiquitinated at the cell surface, exhibits a short half-life (t½;) <1 h), and is protected from degradation by the proteasome inhibitor, MG132. Disruption of the TGN by brefeldin A induces the accumulation of endocytosed GPER in Rab11+ perinuclear endosomes and prevents GPER degradation. Our results provide an explanation as to why GPER is not readily detected on the cell surface in some cell types and further suggest that TGN serves as the checkpoint for degradation of endocytosed GPER.
Collapse
Affiliation(s)
- Shi-Bin Cheng
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Jeffrey A. Quinn
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Carl T. Graeber
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Edward J. Filardo
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| |
Collapse
|
20
|
Bianco SDC, Vandepas L, Correa-Medina M, Gereben B, Mukherjee A, Kuohung W, Carroll R, Teles MG, Latronico AC, Kaiser UB. KISS1R intracellular trafficking and degradation: effect of the Arg386Pro disease-associated mutation. Endocrinology 2011; 152:1616-26. [PMID: 21285314 PMCID: PMC3060635 DOI: 10.1210/en.2010-0903] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The goal of this study was to investigate how the Arg386Pro mutation prolongs KiSS-1 receptor (KISS1R) responsiveness to kisspeptin, contributing to human central precocious puberty. Confocal imaging showed colocalization of wild-type (WT) KISS1R with a membrane marker, which persisted for up to 5 h of stimulation. Conversely, no colocalization with a lysosome marker was detected. Also, overnight treatment with a lysosome inhibitor did not affect WT KISS1R protein, whereas overnight treatment with a proteasome inhibitor increased protein levels by 24-fold. WT and Arg386Pro KISS1R showed time-dependent internalization upon stimulation. However, both receptors were recycled back to the membrane. The Arg386Pro mutation did not affect the relative distribution of KISS1R in membrane and internalized fractions when compared to WT KISS1R for up to 120 min of stimulation, demonstrating that this mutation does not affect KISS1R trafficking rate. Nonetheless, total Arg386Pro KISS1R was substantially increased compared with WT after 120 min of kisspeptin stimulation. This net increase was eliminated by blockade of detection of recycled receptors, demonstrating that recycled receptors account for the increased responsiveness of this mutant to kisspeptin. We therefore conclude the following: 1) WT KISS1R is degraded by proteasomes rather than lysosomes; 2) WT and Arg386Pro KISS1R are internalized upon stimulation, but most of the internalized receptors are recycled back to the membrane rather than degraded; 3) the Arg386Pro mutation does not affect the rate of KISS1R trafficking--instead, it prolongs responsiveness to kisspeptin by decreasing KISS1R degradation, resulting in the net increase on mutant receptor recycled back to the plasma membrane.
Collapse
Affiliation(s)
- Suzy D C Bianco
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Cong P, Pricolo V, Biancani P, Behar J. Effects of cholesterol on CCK-1 receptors and caveolin-3 proteins recycling in human gallbladder muscle. Am J Physiol Gastrointest Liver Physiol 2010; 299:G742-50. [PMID: 20558763 PMCID: PMC2950694 DOI: 10.1152/ajpgi.00064.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The contraction of gallbladders (GBs) with cholesterol stones is impaired due to high cholesterol concentrations in caveolae compared with GBs with pigment stones. The reduced contraction is caused by a lower cholecystokinin (CCK)-8 binding to CCK-1 receptors (CCK-1R) due to caveolar sequestration of receptors. We aimed to examine the mechanism of cholesterol-induced sequestration of receptors. Muscle cells from human and guinea pig GBs were studied. Antibodies were used to examine CCK-1R, antigens of early and recycling endosomes, and total (CAV-3) and phosphorylated caveolar-3 protein (pCAV-3) by Western blots. Contraction was measured in muscle cells transfected with CAV3 mRNA or clathrin heavy-chain small-interfering RNA (siRNA). CCK-1R returned back to the bulk plasma membrane (PM) 30 min after CCK-8 recycled by endosomes, peaking at 5 min in early endosomes and at 20 min in recycling endosomes. Pretreatment with cholesterol-rich liposomes inhibited the transfer of CCK-1R and of CAV-3 in the endosomes by blocking CAV-3 phosphorylation. 4-Amino-5-(4-chloro-phenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (inhibitor of tyrosine kinase) reproduced these effects by blocking pCAV-3 formation, increasing CAV-3 and CCK-1R sequestration in the caveolae and impairing CCK-8-induced contraction. CAV-3 siRNA reduced CAV-3 protein expression, decreased CCK-8-induced contraction, and accumulated CCK-1R in the caveolae. Abnormal concentrations of caveolar cholesterol had no effect on met-enkephalin that stimulates a delta-opioid receptor that internalizes through clathrin. We found that impaired muscle contraction in GBs with cholesterol stones is due to high caveolar levels of cholesterol that inhibits pCAV-3 generation. Caveolar cholesterol increases the caveolar sequestration of CAV-3 and CCK-1R caused by their reduced recycling to the PM.
Collapse
Affiliation(s)
- P. Cong
- Departments of 1Medicine and
| | - V. Pricolo
- 2Surgery, Rhode Island Hospital and Brown University Medical School, Providence, Rhode Island
| | | | | |
Collapse
|
22
|
Cheng L, Biancani P, Behar J. Progesterone receptor A mediates VIP inhibition of contraction. Am J Physiol Gastrointest Liver Physiol 2010; 298:G433-9. [PMID: 20019164 DOI: 10.1152/ajpgi.00346.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The slow transit time of the colon in females with constipation is due to impairment of agonist-induced contraction. The impairment is associated with downregulation of G proteins that mediate contraction and upregulation of Gs proteins that mediate relaxation. These changes are caused by overexpression of progesterone (P4) receptors in the colon, rendering its muscle cells sensitive to physiological P4 concentrations. Downregulation of Gq/11 is mediated by P4 receptor B (PR-B). We examined whether upregulation of Gs proteins increased the inhibition of contraction and whether the increase is mediated by the P4 receptor A (PR-A). These studies were conducted in colon-isolated colon muscle cells from human control and slow-transit constipation (STC) females and from guinea pigs. Muscle cell contraction was induced by CCK-8. Inhibition of contraction was induced by vasoactive intestinal polypeptide (VIP), and 8'bromo-c'AMP (8B-c'AMP) G protein levels were determined by Western blot. VIP-induced inhibition of contraction was greater in muscle cells from STC and P4-treated muscle cells. There were no differences in the inhibition induced by 8B-c'AMP between muscle cells from STC and P4-treated controls. The increased VIP-induced inhibition of muscle cells treated with P4 was blocked by pretreatment with PR-A antibodies and unaffected by PR-B antibodies. These antibodies had no effect on 8B-c'AMP induced-inhibition. The P4 upregulation of Gs proteins was blocked by PR-A antibodies and unaffected by PR-B antibodies. Similar results were obtained in muscle cells from guinea pig colons. We concluded that P4 upregulation of Gs proteins increases VIP-induced inhibition of contraction mediated by PR-A.
Collapse
Affiliation(s)
- Ling Cheng
- Department of Medicine of the Rhode Island Hospital and Warren Alpert Medical School of Brown University, Providence, USA
| | | | | |
Collapse
|
23
|
Mundell SJ, Matharu AL, Nisar S, Palmer TM, Benovic JL, Kelly E. Deletion of the distal COOH-terminus of the A2B adenosine receptor switches internalization to an arrestin- and clathrin-independent pathway and inhibits recycling. Br J Pharmacol 2010; 159:518-33. [PMID: 20128803 PMCID: PMC2828017 DOI: 10.1111/j.1476-5381.2009.00598.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 10/21/2009] [Accepted: 10/22/2009] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE We have investigated the effect of deletions of a postsynaptic density, disc large and zo-1 protein (PDZ) motif at the end of the COOH-terminus of the rat A(2B) adenosine receptor on intracellular trafficking following long-term exposure to the agonist 5'-(N-ethylcarboxamido)-adenosine. EXPERIMENTAL APPROACH The trafficking of the wild type A(2B) adenosine receptor and deletion mutants expressed in Chinese hamster ovary cells was studied using an enzyme-linked immunosorbent assay in combination with immunofluorescence microscopy. KEY RESULTS The wild type A(2B) adenosine receptor and deletion mutants were all extensively internalized following prolonged treatment with NECA. The intracellular compartment through which the Gln(325)-stop receptor mutant, which lacks the Type II PDZ motif found in the wild type receptor initially trafficked was not the same as the wild type receptor. Expression of dominant negative mutants of arrestin-2, dynamin or Eps-15 inhibited internalization of wild type and Leu(330)-stop receptors, whereas only dominant negative mutant dynamin inhibited agonist-induced internalization of Gln(325)-stop, Ser(326)-stop and Phe(328)-stop receptors. Following internalization, the wild type A(2B) adenosine receptor recycled rapidly to the cell surface, whereas the Gln(325)-stop receptor did not recycle. CONCLUSIONS AND IMPLICATIONS Deletion of the COOH-terminus of the A(2B) adenosine receptor beyond Leu(330) switches internalization from an arrestin- and clathrin-dependent pathway to one that is dynamin dependent but arrestin and clathrin independent. The presence of a Type II PDZ motif appears to be essential for arrestin- and clathrin-dependent internalization, as well as recycling of the A(2B) adenosine receptor following prolonged agonist addition.
Collapse
Affiliation(s)
- S J Mundell
- Department of Physiology and Pharmacology, School of Medical Sciences, University of Bristol, Bristol, UK
| | | | | | | | | | | |
Collapse
|
24
|
Böhme I, Beck-Sickinger AG. Illuminating the life of GPCRs. Cell Commun Signal 2009; 7:16. [PMID: 19602276 PMCID: PMC2726148 DOI: 10.1186/1478-811x-7-16] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 07/14/2009] [Indexed: 01/19/2023] Open
Abstract
The investigation of biological systems highly depends on the possibilities that allow scientists to visualize and quantify biomolecules and their related activities in real-time and non-invasively. G-protein coupled receptors represent a family of very dynamic and highly regulated transmembrane proteins that are involved in various important physiological processes. Since their localization is not confined to the cell surface they have been a very attractive "moving target" and the understanding of their intracellular pathways as well as the identified protein-protein-interactions has had implications for therapeutic interventions. Recent and ongoing advances in both the establishment of a variety of labeling methods and the improvement of measuring and analyzing instrumentation, have made fluorescence techniques to an indispensable tool for GPCR imaging. The illumination of their complex life cycle, which includes receptor biosynthesis, membrane targeting, ligand binding, signaling, internalization, recycling and degradation, will provide new insights into the relationship between spatial receptor distribution and function. This review covers the existing technologies to track GPCRs in living cells. Fluorescent ligands, antibodies, auto-fluorescent proteins as well as the evolving technologies for chemical labeling with peptide- and protein-tags are described and their major applications concerning the GPCR life cycle are presented.
Collapse
Affiliation(s)
- Ilka Böhme
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Leipzig University, Brüderstr, 34, 04103 Leipzig, Germany.
| | | |
Collapse
|
25
|
Effect of CCR5 receptor antagonists on endocytosis of the human CCR5 receptor in CHO-K1 cells. Br J Pharmacol 2008; 153:1513-27. [PMID: 18223665 DOI: 10.1038/sj.bjp.0707691] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The CCR5 chemokine receptor is a member of the G protein-coupled receptor (GPCR) family that is expressed by macrophages, memory T-lymphocytes and dendritic cells and is activated by chemotactic proteins (e.g. MIP-1alpha [CCL3], MIP-1beta [CCL4] and RANTES [CCL5]). CCR5 is also the principal co-receptor for macrophage-tropic strains of human immunodeficiency virus-1 (HIV-1) and some chemokines can inhibit HIV-1 infection by stimulating CCR5 receptor endocytosis. The aim of this study was to evaluate the effect of CCR5 antagonists on CCR5 endocytosis. EXPERIMENTAL APPROACH The effects of CCR5 agonists and antagonists on receptor internalization in CHO cells, expressing a C-terminal green fluorescent protein-tagged human CCR5 receptor (CCR5-GFP), were quantified using a confocal imaging plate reader. KEY RESULTS MIP-1alpha [CCL3], MIP-1beta [CCL4] and RANTES [CCL5] were all able to stimulate potently the internalization of CCR5-GFP. This effect was inhibited by the non-peptide antagonist TAK 779. The CCR5 peptide antagonist met-RANTES antagonized MIP-1alpha-mediated increases in intracellular free calcium but was also able to stimulate a substantial internalization of the human CCR5-GFP receptor. However, CHO cells exhibited an aminopeptidase activity that was able to metabolize sufficient met-RANTES into an agonist metabolite capable of stimulating calcium mobilization via CCR5 receptors in naïve cells. CONCLUSIONS AND IMPLICATIONS These data suggest that there is an endogenous aminopeptidase activity on the surface of CHO cells, that produces a slow internalization of the receptor following a time-dependent conversion of receptor-bound met-RANTES from a CCR5 receptor antagonist into a CCR5 agonist molecule.
Collapse
|
26
|
Abstract
We briefly survey the current knowledge and concepts regarding structure and function of the neuropeptide Y Y2 receptor and its agonists, especially as related to pharmacology of the receptor and its roles in pathological processes. Specific structural features are considered that could be responsible for the known compartmentalization and participation of the receptor in cell and tissue organization. This is further discussed in relation to changes of levels of the Y2 receptor in pathological conditions (especially in epilepsy and drug abuse), to endocytosis and recycling, and to participation in wound healing, retinopathy and angiogenesis. Properties of the receptor and of Y2 agonists are considered and reviewed in connection to the negative regulation of transmitter release, feeding, mood and social behavior. The possible involvement of the Y2 receptor in diabetes, carcinogenesis and bone formation is also reviewed.
Collapse
Affiliation(s)
- S L Parker
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
| | | |
Collapse
|
27
|
Thumser AE, Storch J. Characterization of a BODIPY-labeled fluorescent fatty acid analogue. Binding to fatty acid-binding proteins, intracellular localization, and metabolism. Mol Cell Biochem 2007; 299:67-73. [PMID: 16645726 DOI: 10.1007/s11010-005-9041-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The BODIPY-labeled fatty acid analogues are a useful addition to the tools employed to study the cellular uptake and metabolism of lipids. In this study, we show that BODIPY FL C(16) binds to purified liver and intestinal fatty acid-binding proteins with high affinity at a site similar to that for the physiological fatty acid oleic acid. Further, in human intestinal Caco-2 cells BODIPY FL C(16) co-localizes extensively with mitochondria, endoplasmic reticulum/Golgi, and L-FABP. Virtually no esterification of BODIPY FL C(16) was observed under the experimental conditions employed. We conclude that BODIPY FL C(16) may be a useful tool for studying the distribution and function of FABPs in a cellular environment.
Collapse
Affiliation(s)
- Alfred E Thumser
- School of Biomedical and Molecular Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
| | | |
Collapse
|
28
|
Xiao Z, Schmitz F, Pricolo VE, Biancani P, Behar J. Role of caveolae in the pathogenesis of cholesterol-induced gallbladder muscle hypomotility. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1641-9. [PMID: 17307729 DOI: 10.1152/ajpgi.00495.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Muscle cells from human gallbladders (GB) with cholesterol stones (ChS) exhibit a defective contraction, excess cholesterol (Ch) in the plasma membrane, and lower binding of CCK-1 receptors. These abnormalities improved after muscle cells were incubated with Ch-free liposomes that remove the excess Ch from the plasma membrane. The present studies were designed to investigate the role of caveolin-3 proteins (Cav-3) in the pathogenesis of these abnormalities. Muscle cells from GB with ChS exhibit higher Ch levels in the plasma membrane that were mostly localized in caveolae and associated with parallel increases in the expression of Cav-3 in the caveolae compared with that in GB with pigment stones (PS). The overall number of CCK-1 receptors in the plasma membrane was not different between muscle cells from GB with ChS and PS, but they were increased in the caveolae in muscle cells from GB with ChS. Treatment of muscle cells from GB with ChS with a Galpha(i3) protein fragment increased the total binding of CCK-1 receptors (from 8.3 to 11.2%) and muscle contraction induced by CCK-8 (from 11.2 to 17.3% shortening). However, Galpha(q/11) protein fragment had no such effect. Moreover, neither fragment had any effect on muscle cells from GB with PS. We conclude that the defective contraction of muscle cells with excessive Ch levels in the plasma membrane is due to an increased expression of Cav-3 that results in the sequestration of CCK-1 receptors in the caveolae, probably by inhibiting the functions of Galpha(i3) proteins.
Collapse
Affiliation(s)
- Zuoliang Xiao
- Division of Gastroenterology, APC 406, Rhode Island Hospital/Brown Univ. Medical School, 593 Eddy St., Providence, RI 02903, USA.
| | | | | | | | | |
Collapse
|
29
|
Abstract
G protein-coupled receptors (GPCRs) mediate cellular responses to diverse extracellular stimuli to play a vital role in the control of physiology and behaviour. GPCR trafficking is of fundamental importance for the regulation of GPCRs signaling. In this mini review, we will discuss some of the recent findings on the mechanisms that regulate GPCR trafficking, which include (i) large dense-core vesicle (LDCV)-associated GPCR delivery which could be a general cell biological mechanism for rapid modulation of membrane receptors in response to certain stimuli; (ii) lateral diffusion of GPCRs in the plasma membrane for rapid change of the number of neurotransmitter receptors during synaptic plasticity and (iii) constitutive internalization of GPCRs, that contributes to receptor resensitization and distribution, including axonal polarization.
Collapse
Affiliation(s)
- Z-Q D Xu
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | | | | |
Collapse
|
30
|
Abstract
G-protein-coupled receptor kinases (GRKs) interact with the agonist-activated form of G-protein-coupled receptor (GPCR) to affect receptor phosphorylation and to initiate profound impairment of receptor signaling, or desensitization. GPCR forms the largest family of cell surface receptors, and defects in GRK function have the potential consequence to affect GPCR-stimulated biological responses in many pathological situations.
Collapse
Affiliation(s)
- Wen Yang
- Department of Gastroenterology, Pancreas Center, Affiliated Hospital of Medical College of the Chinese People's Armed Police Forces, Chenglinzhuang Road, Tianjin 300162, China
| | | |
Collapse
|
31
|
Fukunaga S, Setoguchi S, Hirasawa A, Tsujimoto G. Monitoring ligand-mediated internalization of G protein-coupled receptor as a novel pharmacological approach. Life Sci 2006; 80:17-23. [PMID: 16978657 DOI: 10.1016/j.lfs.2006.08.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 07/12/2006] [Accepted: 08/16/2006] [Indexed: 11/17/2022]
Abstract
Agonist activation of a G protein-coupled receptor (GPCR) results in the redistribution of the receptor protein away from the cell surface into internal cellular compartments through a process of endocytosis known as internalization. Visualization of receptor internalization has become experimentally practicable by using fluorescent reagents such as green fluorescent protein (GFP). In this study, we examined whether the ligand-mediated internalization of a GPCR can be exploited for pharmacological evaluations. We acquired fluorescent images of cells expressing GFP-labeled GPCRs and evaluated the ligand-mediated internalization quantitatively by image processing. Using beta2-adrenoceptor and vasopressin V1a receptor as model GPCRs that couple to Gs and Gq, respectively, we first examined whether these GFP-tagged GPCRs exhibited appropriate pharmacology. The rank order of receptor internalization potency for a variety of agonists and antagonists specific to each receptor corresponded well with that previously observed in ligand binding studies. In addition to chemical ligand-induced internalization, this cell-based fluorescence imaging system successfully monitored the internalization of the proton-sensing GPCR TDAG8, and that of the free fatty acid-sensitive GPCR GPR120. The results show that monitoring receptor internalization can be a useful approach for pharmacological characterization of GPCRs and in fishing for ligands of orphan GPCRs.
Collapse
Affiliation(s)
- Shin'ichi Fukunaga
- Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimo-adachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | | | | | | |
Collapse
|
32
|
Zhang Y, Wittner M, Bouamar H, Jarrier P, Vainchenker W, Louache F. Identification of CXCR4 as a new nitric oxide-regulated gene in human CD34+ cells. Stem Cells 2006; 25:211-9. [PMID: 17023512 DOI: 10.1634/stemcells.2006-0468] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
As an intracellular second messenger, nitric oxide (NO) is increasingly implicated in the control of transcriptional machinery and gene expression. Here, we show that cell surface expression of CXCR4 on CD34(+) cells was increased in a dose- and time-dependent manner in response to NO donors. Augmented surface expression was correlated with an increase in CXCR4 mRNA level. A specific NO scavenger prevented the elevation in CXCR4 mRNA caused by NO donors, suggesting a direct signaling action mediated by NO on CXCR4 transcription. NO treatment had no significant effect on CXCR4 mRNA stability. However, induction of CXCR4 mRNA by NO was still observed in conditions in which initiation of translation was inhibited, suggesting that the NO effect must be mediated by a pre-existing protein. CXCR4 mRNA induction did not involve cGMP (guanosine 3', 5'-cyclic monophosphate) generation but was most likely mediated via oxidation of intracellular protein thiols. Finally, CD34(+) cells pretreated with NO donors exhibited an increased chemotactic response. This study demonstrates that the NO pathway can modulate CXCR4 expression in human CD34(+) cells and suggests that NO may play a critical role in the trafficking of hematopoietic progenitors.
Collapse
Affiliation(s)
- Yanyan Zhang
- INSERM U790, Institut Gustave Roussy, PR1, Villejuif, France
| | | | | | | | | | | |
Collapse
|
33
|
Tao YX. Inactivating mutations of G protein-coupled receptors and diseases: Structure-function insights and therapeutic implications. Pharmacol Ther 2006; 111:949-73. [PMID: 16616374 DOI: 10.1016/j.pharmthera.2006.02.008] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 02/21/2006] [Indexed: 12/20/2022]
Abstract
Since the discovery of the first rhodopsin mutation that causes retinitis pigmentosa in 1990, significant progresses have been made in elucidating the pathophysiology of diseases caused by inactivating mutations of G protein-coupled receptors (GPCRs). This review aims to compile the compelling evidence accumulated during the past 15 years demonstrating the etiologies of more than a dozen diseases caused by inactivating GPCR mutations. A generalized classification scheme, based on the life cycle of GPCRs, is proposed. Insights gained through detailed studies of these naturally occurring mutations into the structure-function relationship of these receptors are reviewed. Therapeutic approaches directed against the different classes of mutants are being developed. Since intracellular retention emerges as the most common defect, recent progresses aimed at correcting this defect through membrane permeable pharmacological chaperones are highlighted.
Collapse
MESH Headings
- Animals
- Diabetes Insipidus, Nephrogenic/etiology
- Dwarfism/etiology
- Humans
- Hypogonadism/etiology
- Mutation
- Obesity/etiology
- Receptor, Melanocortin, Type 1/genetics
- Receptor, Melanocortin, Type 2/genetics
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptors, CCR5/genetics
- Receptors, Calcium-Sensing/genetics
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/physiology
- Receptors, LHRH/genetics
- Receptors, Vasopressin/genetics
- Retinitis Pigmentosa/etiology
- Rhodopsin/genetics
- Structure-Activity Relationship
Collapse
Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, 213 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
| |
Collapse
|
34
|
Radu D, Tomkinson B, Zachrisson O, Weber G, de Belleroche J, Hirsch S, Lindefors N. Overlapping regional distribution of CCK and TPPII mRNAs in Cynomolgus monkey brain and correlated levels in human cerebral cortex (BA 10). Brain Res 2006; 1104:175-82. [PMID: 16822484 DOI: 10.1016/j.brainres.2006.05.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 05/09/2006] [Accepted: 05/19/2006] [Indexed: 11/21/2022]
Abstract
UNLABELLED Tripeptidyl peptidase II (TPPII) is a high molecular weight exopeptidase important in inactivating extracellular cholecystokinin (CCK). Our aims were to study the anatomical localization of TPPII and CCK mRNA in the Cynomolgus monkey brain as a basis for a possible functional anatomical connection between enzyme (TPPII) and substrate (CCK) and examine if indications of changes in substrate availability in the human brain might be reflected in changes of levels of TPPII mRNA. METHODS mRNA in situ hybridization on postmortem brain from patients having had a schizophrenia diagnosis as compared to controls and on monkey and rat brain slices. RESULTS overlapping distribution patterns of mRNAs for TPPII and CCK in rat and monkey. High amounts of TPPII mRNA are seen in the neocortex, especially in the frontal region and the hippocampus. TPPII mRNA is also present in the basal ganglia and cerebellum where CCK immunoreactivity and/or CCK B receptors have been found in earlier studies, suggesting presence of CCK-ergic afferents from other brain regions. Levels of mRNAs for CCK and TPPII show a positive correlation in postmortem human cerebral cortex Brodmann area (BA) 10. TPPII mRNA might be affected following schizophrenia. DISCUSSION overall TPPII and CCK mRNA show a similar distribution in rat and monkey brain, confirming and extending earlier studies in rodents. In addition, correlated levels of TPPII and CCK mRNA in human BA 10 corroborate a functional link between CCK and TPPII in the human brain.
Collapse
Affiliation(s)
- Diana Radu
- Department of Clinical Neuroscience, Psychiatry Section, Karolinska Institutet, Stockholm, Sweden.
| | | | | | | | | | | | | |
Collapse
|
35
|
Yang GX, Liu TL, Zhang H, Wu CQ, Shen DL. Expression and localization of recombinant human B2 receptors in the methylotrophic yeast Pichia pastoris. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406070040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
36
|
Pula G, Mundell SJ, Roberts PJ, Kelly E. Analysis of mGluR1a constitutive internalization using a pulse-chase enzyme-linked immuno-sorbant assay (ELISA). ACTA ACUST UNITED AC 2006; 64:167-81. [PMID: 16112201 DOI: 10.1016/j.jbbm.2005.07.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2005] [Accepted: 07/15/2005] [Indexed: 11/28/2022]
Abstract
The surface expression of G protein-coupled receptors is regulated by internalization. For many receptors, a constitutive level of internalization in the absence of agonist has been reported. The constitutive internalization of metabotropic glutamate receptor 1a (mGluR1a) has been described, but in general little attention has been dedicated to this important aspect of receptor regulation. Here we describe a pulse-chase ELISA method that allows the investigation of mGluR1a constitutive internalization. When investigated by pulse-chase ELISA, the constitutive internalization of mGluR1a was inhibited by dominant negative mutant constructs of arrestin-2 or Eps-15. This observation, besides indicating the arrestin- and clathrin-dependence of mGluR1a constitutive internalization, also confirmed the physiological relevance of the method described in this article. Confocal microscopy experiments to study receptor localization further validated the pulse-chase labelling procedure. The application of the pulse-chase ELISA to mGluR1b, revealed that this splice variant undergoes marginal constitutive internalization. Two COOH-terminal deletion mutants of mGluR1a, DMI (Arg847stop) and DMII (Arg868stop), were also tested for constitutive internalization. Interestingly, only DMII underwent significant constitutive internalization, suggesting that the region between Arg847 and Arg868 might play a regulatory role in mGluR1a trafficking. Taken together, the pulse-chase ELISA appears to be an efficient tool to analyze the constitutive internalization of different mGluR1 splice variants.
Collapse
Affiliation(s)
- Giordano Pula
- Department of Pharmacology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom.
| | | | | | | |
Collapse
|
37
|
Birse RT, Johnson EC, Taghert PH, Nässel DR. Widely distributed Drosophila G-protein-coupled receptor (CG7887) is activated by endogenous tachykinin-related peptides. ACTA ACUST UNITED AC 2006; 66:33-46. [PMID: 16193493 DOI: 10.1002/neu.20189] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neuropeptides related to vertebrate tachykinins have been identified in Drosophila. Two Drosophila G-protein-coupled receptors (GPCRs), designated NKD (CG6515) and DTKR (CG7887), cloned earlier, display sequence similarities to mammalian tachykinin receptors. However, they were not characterized with the endogenous Drosophila tachykinins (DTKs). The present study characterizes one of these receptors, DTKR. We determined that HEK-293 cells transfected with DTKR displayed dose-dependent increases in both intracellular calcium and cyclic AMP levels in response to the different DTK peptides. DTK peptides also induced internalization of DTKR-green fluorescent protein (GFP) fusion constructs in HEK-293 cells. We generated specific antireceptor antisera and showed that DTKR is widely distributed in the adult brain and more scarcely in the larval CNS. The distribution of the receptor in brain neuropils corresponds well with the distribution of its ligands, the DTKs. Our findings suggest that DTKR is a DTK receptor in Drosophila and that this ligand-receptor system plays multiple functional roles.
Collapse
Affiliation(s)
- Ryan T Birse
- Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden
| | | | | | | |
Collapse
|
38
|
Oh DY, Kim K, Kwon HB, Seong JY. Cellular and molecular biology of orphan G protein-coupled receptors. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 252:163-218. [PMID: 16984818 DOI: 10.1016/s0074-7696(06)52003-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The superfamily of G protein-coupled receptors (GPCRs) is the largest and most diverse group of membrane-spanning proteins. It plays a variety of roles in pathophysiological processes by transmitting extracellular signals to cells via heterotrimeric G proteins. Completion of the human genome project revealed the presence of approximately 168 genes encoding established nonsensory GPCRs, as well as 207 genes predicted to encode novel GPCRs for which the natural ligands remained to be identified, the so-called orphan GPCRs. Eighty-six of these orphans have now been paired to novel or previously known molecules, and 121 remain to be deorphaned. A better understanding of the GPCR structures and classification; knowledge of the receptor activation mechanism, either dependent on or independent of an agonist; increased understanding of the control of GPCR-mediated signal transduction; and development of appropriate ligand screening systems may improve the probability of discovering novel ligands for the remaining orphan GPCRs.
Collapse
Affiliation(s)
- Da Young Oh
- Laboratory of G Protein-Coupled Receptors, Korea University College of Medicine, Seoul 136-707, Korea
| | | | | | | |
Collapse
|
39
|
Sarnataro D, Grimaldi C, Pisanti S, Gazzerro P, Laezza C, Zurzolo C, Bifulco M. Plasma membrane and lysosomal localization of CB1 cannabinoid receptor are dependent on lipid rafts and regulated by anandamide in human breast cancer cells. FEBS Lett 2005; 579:6343-9. [PMID: 16263116 DOI: 10.1016/j.febslet.2005.10.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 10/10/2005] [Accepted: 10/11/2005] [Indexed: 01/06/2023]
Abstract
In this report we show, by confocal analysis of indirect immunofluorescence, that the type-1 cannabinoid receptor (CB1R), which belongs to the family of G-protein-coupled receptors, is expressed on the plasma membrane in human breast cancer MDA-MB-231 cells. However, a substantial proportion of the receptor is present in lysosomes. We found that CB1R is associated with cholesterol- and sphyngolipid-enriched membrane domains (rafts). Cholesterol depletion by methyl-beta-cyclodextrin (MCD) treatment strongly reduces the flotation of the protein on the raft-fractions (DRM) of sucrose density gradients suggesting that CB1 raft-association is cholesterol dependent. Interestingly binding of the agonist, anandamide (AEA) also impairs DRM-association of the receptor suggesting that the membrane distribution of the receptor is dependent on rafts and is possibly regulated by the agonist binding. Indeed MCD completely blocked the clustering of CB1R at the plasma membrane. On the contrary the lysosomal localization of CB1R was impaired by this treatment only after AEA binding.
Collapse
Affiliation(s)
- Daniela Sarnataro
- Dip.di Scienze Farmaceutiche, Università degli Studi di Salerno, Italy
| | | | | | | | | | | | | |
Collapse
|
40
|
Niebauer RT, Wedekind A, Robinson AS. Decreases in yeast expression yields of the human adenosine A2a receptor are a result of translational or post-translational events. Protein Expr Purif 2005; 37:134-43. [PMID: 15294291 DOI: 10.1016/j.pep.2004.06.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Revised: 06/01/2004] [Indexed: 11/21/2022]
Abstract
The human adenosine receptor (A2a), a G-protein-coupled receptor (GPCR), was C-terminally tagged with the green fluorescent protein (GFP) and expressed in the yeast Saccharomyces cerevisiae to gain an understanding of the expression limitations of this medically relevant class of membrane proteins. The A2a-GFP protein was able to bind adenosine analogs indicating that the GFP tag did not alter the ligand binding activity of the receptor. A screen based on whole cell fluorescence was developed and a library of clones with various gene copy numbers was screened via flow cytometry to isolate clones with the highest protein expression levels. All clones studied exhibited a decrease in the net A2a-GFP protein production rate over time as determined by whole cell fluorescence, Western blotting, confocal microscopy, and ligand binding. Quantitative PCR showed that A2a-GFP mRNA levels remained relatively high even as the protein production rate decreased. A cycloheximide chase experiment showed that the mature protein was stable over time and was not significantly degraded. Taken together, these results suggest that heterologous expression of GPCRs is limited by a translational or post-translational bottleneck that is unique from expression limitations seen for soluble proteins.
Collapse
Affiliation(s)
- Ronald T Niebauer
- Department of Chemical Engineering, University of Delaware, Newark, DE 19716, USA
| | | | | |
Collapse
|
41
|
Tao YX. Molecular mechanisms of the neural melanocortin receptor dysfunction in severe early onset obesity. Mol Cell Endocrinol 2005; 239:1-14. [PMID: 15975705 DOI: 10.1016/j.mce.2005.04.012] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Revised: 04/10/2005] [Accepted: 04/20/2005] [Indexed: 11/23/2022]
Abstract
The neural melanocortin receptors, melanocortin-3 and -4 receptors (MC3R and MC4R), have been shown to regulate different aspects of energy homeostasis in rodents. Human genetic studies showed that mutations in the MC4R gene are the most common monogenic form of obesity. Functional analyses of the mutant receptors revealed multiple defects. A classification scheme is presented for cataloguing the ever-increasing array of MC4R mutations. Functional analysis of the only inactivating MC3R mutation is also summarized. Insights from the analyses of the naturally occurring mutations in the MC3R and MC4R on the structure and function of these receptors are highlighted.
Collapse
Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, AL 36849, USA.
| |
Collapse
|
42
|
Veyrat-Durebex C, Pomerleau L, Langlois D, Gaudreau P. Internalization and trafficking of the human and rat growth hormone-releasing hormone receptor. J Cell Physiol 2005; 203:335-44. [PMID: 15499571 DOI: 10.1002/jcp.20233] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Internalization and intracellular trafficking of the growth hormone-releasing hormone receptor (GHRH-R) were studied in rat anterior pituitary and human (h) and rat (r) GHRH-R-transfected BHK cells, with the GHRH agonist, [N(alpha)-5-carboxyfluoresceinyl-D-Ala(2), Ala(8), Ala(15), Lys(22)]hGHRH(1-29)NH(2) (Fluo-GHRH). Time- and temperature-dependent internalization of stimulated GHRH-R was blocked by phenyl arsine oxide (PAO) in both cell types. In anterior pituitary and rGHRH-R-transfected BHK cells, only filipin III and cerulenin blocked receptor-mediated internalization of Fluo-GHRH while in hGHRH-R-transfected BHK cells, only hyperosmolar sucrose inhibited this process. These results suggest that hGHRH-R internalization is clathrin-dependent, while fatty acid acylation of rGHRH-R appears to be a prerequisite to caveolin-dependent internalization. Experiments in anterior pituitary using Bodipy-FL-C(5) ganglioside GM1, a specific marker of lipid rafts such as caveolae, confirmed this latter pathway. Co-localization of Fluo-GHRH with LysoTracker indicated that Fluo-GHRH was directed to acidic organelles in both cell types. Finally, studies using cycloheximide and monensin showed that upon stimulation with GHRH, an optimal concentration of functional GHRH-R was maintained at the plasma membrane due to de novo synthesis and recycling in pituitary cells and to de novo synthesis solely in hGHRH-R-transfected BHK cells. This first study on the dynamics of the GHRH/GHRH-R complexes using fluorescence imaging in a native environment compared to cell system models, revealed that both receptor primary structure and concentration at the plasma membrane play important roles in internalization and trafficking of specific G-protein-coupled receptors (GPCR).
Collapse
Affiliation(s)
- Christelle Veyrat-Durebex
- Laboratory of Neuroendocrinology of Aging, Centre Hospitalier de l'Université de Montréal Research Center, Notre-Dame Hospital and Department of Medicine, University of Montreal, Montreal, Quebec, Canada H2L 4M1
| | | | | | | |
Collapse
|
43
|
Bhattacharya M, Babwah AV, Godin C, Anborgh PH, Dale LB, Poulter MO, Ferguson SSG. Ral and phospholipase D2-dependent pathway for constitutive metabotropic glutamate receptor endocytosis. J Neurosci 2005; 24:8752-61. [PMID: 15470141 PMCID: PMC6729950 DOI: 10.1523/jneurosci.3155-04.2004] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
G-protein-coupled receptors play a central role in the regulation of neuronal cell communication. Class 1 metabotropic glutamate receptors (mGluRs) mGluR1a and mGluR5a, which are coupled with the hydrolysis of phosphoinositides, are essential for modulating excitatory neurotransmission at glutamatergic synapses. These receptors are constitutively internalized in heterologous cell cultures, neuronal cultures, and intact neuronal tissues. We show here that the small GTP-binding protein Ral, its guanine nucleotide exchange factor RalGDS (Ral GDP dissociation stimulator), and phospholipase D2 (PLD2) are constitutively associated with class 1 mGluRs and regulate constitutive mGluR endocytosis. Moreover, both Ral and PLD2 are colocalized with mGluRs in endocytic vesicles in both human embryonic kidney 293 (HEK 293) cells and neurons. Ral and PLD2 activity is required for the internalization of class 1 mGluRs but is not required for the internalization of the beta2-adrenergic receptor. Constitutive class 1 mGluR internalization is not dependent on the downstream Ral effector proteins Ral-binding protein 1 and PLD1 or either ADP-ribosylation factors ARF1 or ARF6. The treatment of HEK 293 cells and neurons with small interfering RNA both downregulates PLD2 expression and blocks mGluR1a and mGluR5a endocytosis. The constitutive internalization of mGluR1a and mGluR5a is also attenuated by the treatment of cells with 1-butanol to prevent PLD2-mediated phosphatidic acid formation. We propose that the formation of a mGluR-scaffolded RalGDS/Ral/PLD2 protein complex provides a novel alternative mechanism to beta-arrestins for the constitutive endocytosis of class 1 mGluRs.
Collapse
Affiliation(s)
- Moshmi Bhattacharya
- Cell Biology Research Group, Robarts Research Institute, London, Ontario, Canada N6A 5K8
| | | | | | | | | | | | | |
Collapse
|
44
|
Moody TW, Czerwinski G, Tarasova NI, Moody DL, Michejda CJ. The development of VIP-ellipticine conjugates. ACTA ACUST UNITED AC 2005; 123:187-92. [PMID: 15518911 DOI: 10.1016/j.regpep.2004.03.021] [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] [Indexed: 11/17/2022]
Abstract
The mechanism by which vasoactive intestinal peptide (VIP)-ellipticine (E) conjugates are cytotoxic for human lung cancer cells was investigated. VIP-alanyl-leucyl-alanyl-leucyl-alanine (ALALA)-E and VIP-leucyl-alanyl-leucyl-alanine (LALA)-E inhibited (125)I-VIP binding to NCI-H1299 cells with an IC50 values of 0.5 and 0.1 microM, respectively. VIP-ALALA-E and VIP-LALA-E caused elevation of cAMP in NCI-H1299 cells with ED50 values of 0.7 and 0.1 microM. Radiolabeled VIP-LALA-E was internalized at 37 degrees C and delivered the cytotoxic E into NCI-H1299 cells. VIP-LALA-E inhibited the growth of NCI-H1299 cells in vitro. Three days after the addition of VIP-LALA-E to NCI-H1299 cells, cell viability decreased based on trypan blue exclusion and reduced 3H-thymidine uptake. These results suggest that VIP-E conjugates are internalized in lung cancer cells as a result of VPAC1 receptor-mediated endocytosis.
Collapse
Affiliation(s)
- Terry W Moody
- Department of Health and Human Services, NCI Office of the Director, CCR, Building 31, Room 3A34, 31 Center Drive, Bethesda, MD 20892, USA.
| | | | | | | | | |
Collapse
|
45
|
Xiao ZL, Pricolo V, Biancani P, Behar J. Role of progesterone signaling in the regulation of G-protein levels in female chronic constipation. Gastroenterology 2005; 128:667-75. [PMID: 15765402 DOI: 10.1053/j.gastro.2004.12.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND & AIMS Chronic constipation caused by slow transit is common in women with an F/M ratio of 9:1. The cause and mechanisms responsible for this syndrome are unknown. Progesterone has been suggested as a possible contributing factor. Our aim was to investigate the site and mechanisms responsible for this colonic motility disorder. METHODS Seven women with intractable constipation and slow transit time underwent colectomy and 6 women who underwent a left colectomy for adenocarcinoma (controls) were studied. Dissociated colonic circular muscle cells were obtained by enzymatic digestion. Changes in G-protein levels were measured by Western blot. The messenger RNA (mRNA) expression of Galpha q and progesterone receptors was determined by reverse-transcription polymerase chain reaction and Northern blot. RESULTS Muscle cells from patients with chronic constipation exhibited impaired contraction in response to receptor-G-protein-dependent agonists (cholecystokinin [CCK], acetylcholine) and in response to the direct G-protein activator guanosine 5'-O-(3-thiophosphate). Contraction was normal with receptor-G-protein-independent agonists (diacylglycerol and KCl). Western blot showed down-regulation of Galpha q/11 and up-regulation of Galpha s proteins in patients with chronic constipation. The mRNA expression of Galpha q was lower and the progesterone receptors were overexpressed in patients with chronic constipation compared with controls. These abnormalities were reproduced in vitro by pretreatment of normal colonic muscle cells with progesterone for 4 hours. CONCLUSIONS Slow transit chronic constipation in women may be caused by down-regulation of contractile G proteins and up-regulation of inhibitory G proteins, probably caused by overexpression of progesterone receptors.
Collapse
Affiliation(s)
- Zuo-Liang Xiao
- Department of Medicine, Rhode Island Hospital and Brown University School of Medicine, Providence, Rhode Island 02903, USA
| | | | | | | |
Collapse
|
46
|
Wang L, Radu CG, Yang LV, Bentolila LA, Riedinger M, Witte ON. Lysophosphatidylcholine-induced surface redistribution regulates signaling of the murine G protein-coupled receptor G2A. Mol Biol Cell 2005; 16:2234-47. [PMID: 15728718 PMCID: PMC1087231 DOI: 10.1091/mbc.e04-12-1044] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intracellular trafficking and spatial dynamics of membrane receptors critically regulate receptor function. Using microscopic and subcellular fractionation analysis, we studied the localization of the murine G protein-coupled receptor G2A (muG2A). Evaluating green fluorescent protein-tagged, exogenously expressed as well as the endogenous muG2A, we observed that this receptor was spontaneously internalized and accumulated in endosomal compartments, whereas its surface expression was enhanced and stabilized by lysophosphatidylcholine (LPC) treatment. Monensin, a general inhibitor of recycling pathways, blocked LPC-regulated surface localization of muG2A as well as muG2A-dependent extracellular signal-regulated kinase (ERK) activation and cell migration induced by LPC treatment. Mutation of the conserved DRY motif (R-->A) enhanced the surface expression of muG2A, resulting in its resistance to monensin inhibition of ERK activation. Our data suggest that intracellular sequestration and surface expression regulated by LPC, rather than direct agonistic activity control the signaling responses of murine G2A toward LPC.
Collapse
Affiliation(s)
- Li Wang
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
| | | | | | | | | | | |
Collapse
|
47
|
Pucadyil TJ, Kalipatnapu S, Harikumar KG, Rangaraj N, Karnik SS, Chattopadhyay A. G-protein-dependent cell surface dynamics of the human serotonin1A receptor tagged to yellow fluorescent protein. Biochemistry 2005; 43:15852-62. [PMID: 15595840 DOI: 10.1021/bi0480887] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Serotonergic signaling appears to play a key role in the generation and modulation of various cognitive, behavioral, and developmental processes. The serotonin(1A) receptor is an important member of the superfamily of seven transmembrane domain G-protein-coupled receptors and is the most extensively studied among the serotonin receptors. Several aspects of serotonin(1A) receptor biology such as cellular distribution and signal transduction characteristics are technically difficult to address in living cells on account of the inability to optically track these receptors with fluorescence-based techniques. We describe here the characterization of the serotonin(1A) receptor tagged to the enhanced yellow fluorescent protein (EYFP) stably expressed in Chinese hamster ovary (CHO) cells. These receptors were found to be essentially similar to the native receptor in pharmacological assays and can therefore be used to reliably explore aspects of receptor biology such as cellular distribution and dynamics on account of their intrinsic fluorescent properties. Analysis of the cell surface dynamics of these receptors by fluorescence recovery after photobleaching (FRAP) experiments has provided novel insight into the molecular mechanism of signal transduction of serotonin(1A) receptors in living cells. Interestingly, addition of pharmacologically well-characterized ligands or activators of G-proteins altered the diffusion characteristics of the receptor in a manner consistent with the G-protein activation model. These results demonstrate, for the first time, that membrane dynamics of this receptor is modulated in a G-protein-dependent manner.
Collapse
Affiliation(s)
- Thomas J Pucadyil
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | | | | | | | | | | |
Collapse
|
48
|
Pediani JD, Colston JF, Caldwell D, Milligan G, Daly CJ, McGrath JC. Beta-arrestin-dependent spontaneous alpha1a-adrenoceptor endocytosis causes intracellular transportation of alpha-blockers via recycling compartments. Mol Pharmacol 2004; 67:992-1004. [PMID: 15626751 DOI: 10.1124/mol.104.008417] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The antagonist ligand BODIPY-FL-prazosin (QAPB) fluoresces when bound to bovine alpha(1a)-adrenoceptors (ARs). Data indicate that the receptor-ligand complex is spontaneously internalized by beta-arrestin-dependent endocytosis. Internalization of the ligand did not occur in beta-arrestin-deficient cells; was blocked or reversed by another alpha(1) ligand, phentolamine, indicating it to reflect binding to the orthosteric recognition site; and was prevented by blocking clathrin-mediated endocytosis. The ligand showed rapid, diffuse, low-intensity, surface binding, superseded by punctate intracellular binding that developed to equilibrium in 50 to 60 min and was reversible on ligand removal, indicating a dynamic equilibrium. In cells expressing a human alpha(1a)-AR-enhanced green fluorescent protein (EGFP) 2 fusion protein, BODIPY-R-558/568-prazosin (RQAPB) colocalized with the fusion, indicating that the ligand gained access to all compartments containing the receptor, and, conversely, that the receptor has affinity for the ligand at all of these sites. The distribution of QAPB binding sites was similar for receptors with or without EGFP2, validating the fusion protein as an indicator of receptor location. The ligand partially colocalized with beta-arrestin in recycling and late endosomes, indicating receptor transit without destruction. Organelles containing receptors showed considerable movement consistent with a transportation function. This was absent in beta-arrestin-deficient cells, indicating that both constitutive receptor internalization and subsequent intracellular transportation are beta-arrestin-dependent. Calculations of relative receptor number indicate that at steady state, less than 30% of receptors reside on the cell surface and that recycling is rapid. We conclude that alpha(1a)-ARs recycle rapidly by an agonist-independent, constitutive, beta-arrestin-dependent process and that this can transport "alpha-blockers" into cells carrying these receptors.
Collapse
Affiliation(s)
- John D Pediani
- Autonomic Physiology Unit, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
| | | | | | | | | | | |
Collapse
|
49
|
Uchida D, Begum NM, Tomizuka Y, Bando T, Almofti A, Yoshida H, Sato M. Acquisition of lymph node, but not distant metastatic potentials, by the overexpression of CXCR4 in human oral squamous cell carcinoma. J Transl Med 2004; 84:1538-46. [PMID: 15492752 DOI: 10.1038/labinvest.3700190] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Recently, it has been suggested that chemokine/receptor interactions determine the destination of the invasive tumor cells in several types of cancer. It has also been proposed that the stromal cell-derived factor-1 (SDF-1; CXCL12)/CXCR4 system might be involved lymph node metastasis in oral squamous cell carcinoma (SCC). In order to further clarify the role of the SDF-1/CXCR4 system in oral SCC, we generated CXCR4 stable transfectants (IH-CXCR4) using oral SCC cells, and compared them to IH, which did not express CXCR4 and which did not have lymph node metastatic potentials in vivo. We introduced enhanced green fluorescent protein (GFP) fused-CXCR4 into IH cells, and detected the GFP fluorescence in the cytoplasm and cell membrane in approximately 60% of the G418-resistant cells. This bulk-transfectant expressed a high level of CXCR4 mRNA and protein, and exhibited the characteristic calcium fluxes and chemotactic activity observed in treatment with SDF-1. SDF-1 biphasically activated extracellular signal-regulated kinase (ERK)1/2, but continuously activated Akt/protein kinase B (PKB) in IH-CXCR4 cells. Most importantly, IH-CXCR4 cells frequently metastasized to the cervical lymph node, but not to the distant organs in the orthotopic inoculation of nude mice. Furthermore, these lymph node metastases were inhibited by the treatment of a mitogen-activated protein kinase/ERK kinase inhibitor, U0126, or a phosphatidylinositol 3 kinase inhibitor, wortmannin. These results indicate that SDF-1/CXCR4 signaling mediates the establishment of lymph node metastasis in oral SCC via ERK1/2 or Akt/PKB pathway.
Collapse
Affiliation(s)
- Daisuke Uchida
- Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, Kuramoto, Tokushima, Japan.
| | | | | | | | | | | | | |
Collapse
|
50
|
González-Maeso J, Wise A, Green A, Koenig JA. Agonist-induced desensitization and endocytosis of heterodimeric GABAB receptors in CHO-K1 cells. Eur J Pharmacol 2004; 481:15-23. [PMID: 14637170 DOI: 10.1016/j.ejphar.2003.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
gamma-Aminobutyric acid B (GABA(B)) receptor is the first discovered G protein-coupled receptor that requires two subunits, GB1 and GB2, to form a functional receptor. Whereas the molecular and functional characteristics of GABA(B) receptors have been recently extensively studied, the mechanisms underlying receptor desensitization and endocytosis are still poorly understood. We have investigated the effect of continuous agonist exposure on the human GABA(B) receptor functional response and redistribution when expressed in Chinese hamster ovary (CHO-K1) cells. The wild-type GABA(B) receptor-mediated inhibition of the adenylate cyclase activity appeared desensitized after 2 h in the presence of GABA (100 microM). Fusion proteins were generated by attachment of cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) to GB1 and GB2, respectively, and confocal microscopy experiments in intact living cells semi-stably expressing the constructs were performed. Incubation of co-expressing CFP-GB1 and YFP-GB2 cells in the presence of GABA (100 microM) for 2 h induced a profound receptor internalization, and CFP-GB1 and YFP-GB2 appeared co-localized in the endosome (labelled with Cy3-transferrin). The internalization was blocked by a selective GABA(B) receptor antagonist. These results represent the first clear visualization of agonist-induced internalization of the unique heterodimeric GABA(B) receptor.
Collapse
Affiliation(s)
- Javier González-Maeso
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QJ, UK.
| | | | | | | |
Collapse
|