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Bolinger AA, Frazier A, La JH, Allen JA, Zhou J. Orphan G Protein-Coupled Receptor GPR37 as an Emerging Therapeutic Target. ACS Chem Neurosci 2023; 14:3318-3334. [PMID: 37676000 PMCID: PMC11144446 DOI: 10.1021/acschemneuro.3c00479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are successful druggable targets, making up around 35% of all FDA-approved medications. However, a large number of receptors remain orphaned, with no known endogenous ligand, representing a challenging but untapped area to discover new therapeutic targets. Among orphan GPCRs (oGPCRs) of interest, G protein-coupled receptor 37 (GPR37) is highly expressed in the central nervous system (CNS), particularly in the spinal cord and oligodendrocytes. While its cellular signaling mechanisms and endogenous receptor ligands remain elusive, GPR37 has been implicated in several important neurological conditions, including Parkinson's disease (PD), inflammation, pain, autism, and brain tumors. GPR37 structure, signaling, emerging physiology, and pharmacology are reviewed while integrating a discussion on potential therapeutic indications and opportunities.
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Affiliation(s)
- Andrew A. Bolinger
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Andrew Frazier
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jun-Ho La
- Department of Neurobiology, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - John A. Allen
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jia Zhou
- Department of Pharmacology and Toxicology, Center for Addiction Sciences and Therapeutics, University of Texas Medical Branch, Galveston, Texas 77555, United States
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2
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Libanje F, Delille R, Young PA, Rolland S, Meyer-Losic F, Lewkowicz E, Klinz S. NTSR1 glycosylation and MMP dependent cleavage generate three distinct forms of the protein. Sci Rep 2023; 13:4663. [PMID: 36949141 PMCID: PMC10033925 DOI: 10.1038/s41598-023-31790-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 03/17/2023] [Indexed: 03/24/2023] Open
Abstract
NTSR1 abnormal expression by cancer cells makes it a strategic target for antitumoral therapies, such as compounds that use NTSR1 binding probes to deliver cytotoxic agents to tumor cells. Success of these therapies relies on NTSR1 protein availability and accessibility; therefore, understanding the protein's biology is crucial. We studied NTSR1 protein in exogenously and endogenously expressing non-tumoral and tumoral cells. We found NTSR1 to be expressed as three distinct protein forms: the NTSR1-high form, a glycosylated protein; the NTSR1-low form, a N-terminally cleaved and de-glycosylated protein; and the NTSR1-LP protein with the MW size predicted by its NTSR1 amino acid sequence. We show that the NTSR1-high form is cleaved by MMPs to generate the NTSR1-low form, a process that is promoted by the Neurotensin (NTS) ligand. In addition, NTS induced the internalization of plasma membrane localized NTSR1 and degradation of NTSR1-low form via the proteasome. Importantly, we found NTSR1-low form to be the most abundant form in the tumoral cells and in PDAC Patient Derived Xenograft, demonstrating its physiopathological relevance. Altogether, our work provides important technical and experimental tools as well as new crucial insights into NTSR1 protein biology that are required to develop clinically relevant NTSR1 targeting anti-tumoral therapies.
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Affiliation(s)
- Fotine Libanje
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France.
| | - Raphael Delille
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Pamela A Young
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Sylvie Rolland
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | | | - Elodie Lewkowicz
- Translational Biomarkers and Pharmacology, IPSEN Innovation, Les Ulis, France
| | - Stephan Klinz
- Early Development and Translational Sciences, IPSEN Bioscience, Cambridge, USA
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3
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Emerging Roles for the Orphan GPCRs, GPR37 and GPR37 L1, in Stroke Pathophysiology. Int J Mol Sci 2022; 23:ijms23074028. [PMID: 35409385 PMCID: PMC9000135 DOI: 10.3390/ijms23074028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/31/2022] [Accepted: 04/02/2022] [Indexed: 11/17/2022] Open
Abstract
Recent studies have shed light on the diverse and complex roles of G-protein coupled receptors (GPCRs) in the pathophysiology of stroke. These receptors constitute a large family of seven transmembrane-spanning proteins that play an intricate role in cellular communication mechanisms which drive both tissue injury and repair following ischemic stroke. Orphan GPCRs represent a unique sub-class of GPCRs for which no natural ligands have been found. Interestingly, the majority of these receptors are expressed within the central nervous system where they represent a largely untapped resource for the treatment of neurological diseases. The focus of this review will thus be on the emerging roles of two brain-expressed orphan GPCRs, GPR37 and GPR37 L1, in regulating various cellular and molecular processes underlying ischemic stroke.
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4
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Klenk C, Hommers L, Lohse MJ. Proteolytic Cleavage of the Extracellular Domain Affects Signaling of Parathyroid Hormone 1 Receptor. Front Endocrinol (Lausanne) 2022; 13:839351. [PMID: 35273573 PMCID: PMC8902639 DOI: 10.3389/fendo.2022.839351] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Accepted: 01/27/2022] [Indexed: 11/13/2022] Open
Abstract
Parathyroid hormone 1 receptor (PTH1R) is a member of the class B family of G protein-coupled receptors, which are characterized by a large extracellular domain required for ligand binding. We have previously shown that the extracellular domain of PTH1R is subject to metalloproteinase cleavage in vivo that is regulated by ligand-induced receptor trafficking and leads to impaired stability of PTH1R. In this work, we localize the cleavage site in the first loop of the extracellular domain using amino-terminal protein sequencing of purified receptor and by mutagenesis studies. We further show, that a receptor mutant not susceptible to proteolytic cleavage exhibits reduced signaling to Gs and increased activation of Gq compared to wild-type PTH1R. These findings indicate that the extracellular domain modulates PTH1R signaling specificity, and that its cleavage affects receptor signaling.
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Affiliation(s)
- Christoph Klenk
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
- *Correspondence: Christoph Klenk,
| | - Leif Hommers
- Interdisciplinary Center for Clinical Research, University Hospital of Würzburg, Würzburg, Germany
- Department of Psychiatry, Psychosomatics and Psychotherapy, Center for Mental Health, University Hospital of Würzburg, Würzburg, Germany
- Comprehensive Heart Failure Center (CHFC), University Hospital of Würzburg, Würzburg, Germany
| | - Martin J. Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
- Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
- Max Delbrück Center for Molecular Medicine (MDC), Berlin, Germany
- ISAR Bioscience Institute, Planegg, Germany
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5
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Mattila SO, Tuhkanen HE, Lackman JJ, Konzack A, Morató X, Argerich J, Saftig P, Ciruela F, Petäjä-Repo UE. GPR37 is processed in the N-terminal ectodomain by ADAM10 and furin. FASEB J 2021; 35:e21654. [PMID: 34042202 DOI: 10.1096/fj.202002385rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 04/12/2021] [Accepted: 04/26/2021] [Indexed: 11/11/2022]
Abstract
GPR37 is an orphan G protein-coupled receptor (GPCR) implicated in several neurological diseases and important physiological pathways in the brain. We previously reported that its long N-terminal ectodomain undergoes constitutive metalloprotease-mediated cleavage and shedding, which have been rarely described for class A GPCRs. Here, we demonstrate that the protease that cleaves GPR37 at Glu167↓Gln168 is a disintegrin and metalloprotease 10 (ADAM10). This was achieved by employing selective inhibition, RNAi-mediated downregulation, and genetic depletion of ADAM10 in cultured cells as well as in vitro cleavage of the purified receptor with recombinant ADAM10. In addition, the cleavage was restored in ADAM10 knockout cells by overexpression of the wild type but not the inactive mutant ADAM10. Finally, postnatal conditional depletion of ADAM10 in mouse neuronal cells was found to reduce cleavage of the endogenous receptor in the brain cortex and hippocampus, confirming the physiological relevance of ADAM10 as a GPR37 sheddase. Additionally, we discovered that the receptor is subject to another cleavage step in cultured cells. Using site-directed mutagenesis, the site (Arg54↓Asp55) was localized to a highly conserved region at the distal end of the ectodomain that contains a recognition site for the proprotein convertase furin. The cleavage by furin was confirmed by using furin-deficient human colon carcinoma LoVo cells and proprotein convertase inhibitors. GPR37 is thus the first multispanning membrane protein that has been validated as an ADAM10 substrate and the first GPCR that is processed by both furin and ADAM10. The unconventional N-terminal processing may represent an important regulatory element for GPR37.
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Affiliation(s)
- S Orvokki Mattila
- Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, Oulu, Finland
| | - Hanna E Tuhkanen
- Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, Oulu, Finland
| | - Jarkko J Lackman
- Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, Oulu, Finland
| | - Anja Konzack
- Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, Oulu, Finland
| | - Xavier Morató
- Unitat de Farmacologia, Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain
| | - Josep Argerich
- Unitat de Farmacologia, Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain
| | - Paul Saftig
- Institute of Biochemistry, Kiel University, Kiel, Germany
| | - Francisco Ciruela
- Unitat de Farmacologia, Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain.,Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
| | - Ulla E Petäjä-Repo
- Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, Oulu, Finland
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Ahmad R, Lahuna O, Sidibe A, Daulat A, Zhang Q, Luka M, Guillaume JL, Gallet S, Guillonneau F, Hamroune J, Polo S, Prévot V, Delagrange P, Dam J, Jockers R. GPR50-Ctail cleavage and nuclear translocation: a new signal transduction mode for G protein-coupled receptors. Cell Mol Life Sci 2020; 77:5189-5205. [PMID: 31900622 PMCID: PMC11105015 DOI: 10.1007/s00018-019-03440-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 11/21/2019] [Accepted: 12/23/2019] [Indexed: 01/14/2023]
Abstract
Transmission of extracellular signals by G protein-coupled receptors typically relies on a cascade of intracellular events initiated by the activation of heterotrimeric G proteins or β-arrestins followed by effector activation/inhibition. Here, we report an alternative signal transduction mode used by the orphan GPR50 that relies on the nuclear translocation of its carboxyl-terminal domain (CTD). Activation of the calcium-dependent calpain protease cleaves off the CTD from the transmembrane-bound GPR50 core domain between Phe-408 and Ser-409 as determined by MALDI-TOF-mass spectrometry. The cytosolic CTD then translocates into the nucleus assisted by its 'DPD' motif, where it interacts with the general transcription factor TFII-I to regulate c-fos gene transcription. RNA-Seq analysis indicates a broad role of the CTD in modulating gene transcription with ~ 8000 differentially expressed genes. Our study describes a non-canonical, direct signaling mode of GPCRs to the nucleus with similarities to other receptor families such as the NOTCH receptor.
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Affiliation(s)
- Raise Ahmad
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Olivier Lahuna
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Anissa Sidibe
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Avais Daulat
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Qiang Zhang
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Marine Luka
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Jean-Luc Guillaume
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Sarah Gallet
- Jean-Pierre Aubert Research Center, U837, Lille, France
| | - François Guillonneau
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Juliette Hamroune
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Sophie Polo
- Epigenetics and Cell Fate Centre, UMR7216, CNRS, Paris Diderot University, Paris, France
| | | | - Philippe Delagrange
- Pôle D'Innovation Thérapeutique Neuropsychiatrie, Institut de Recherches Servier, 125 Chemin de Ronde, 78290, Croissy, France
| | - Julie Dam
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France
| | - Ralf Jockers
- Université de Paris, Institut Cochin, CNRS, INSERM, 22 rue Méchain, 75014, Paris, France.
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7
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The N-terminus of GPR37L1 is proteolytically processed by matrix metalloproteases. Sci Rep 2020; 10:19995. [PMID: 33203955 PMCID: PMC7673139 DOI: 10.1038/s41598-020-76384-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 10/22/2020] [Indexed: 12/11/2022] Open
Abstract
GPR37L1 is an orphan G protein-coupled receptor expressed exclusively in the brain and linked to seizures, neuroprotection and cardiovascular disease. Based upon the observation that fragments of the GPR37L1 N-terminus are found in human cerebrospinal fluid, we hypothesized that GPR37L1 was subject to post-translational modification. Heterologous expression of GPR37L1-eYFP in either HEK293 or U87 glioblastoma cells yielded two cell surface species of approximately equivalent abundance, the larger of which is N-glycosylated at Asn105. The smaller species is produced by matrix metalloprotease/ADAM-mediated proteolysis (shown by the use of pharmacological inhibitors) and has a molecular weight identical to that of a mutant lacking the entire N-terminus, Δ122 GPR37L1. Serial truncation of the N-terminus prevented GPR37L1 expression except when the entire N-terminus was removed, narrowing the predicted site of N-terminal proteolysis to residues 105–122. Using yeast expressing different G protein chimeras, we found that wild type GPR37L1, but not Δ122 GPR37L1, coupled constitutively to Gpa1/Gαs and Gpa1/Gα16 chimeras, in contrast to previous studies. We tested the peptides identified in cerebrospinal fluid as well as their putative newly-generated N-terminal ‘tethered’ counterparts in both wild type and Δ122 GPR37L1 Gpa1/Gαs strains but saw no effect, suggesting that GPR37L1 does not signal in a manner akin to the protease-activated receptor family. We also saw no evidence of receptor activation or regulation by the reported GPR37L1 ligand, prosaptide/TX14A. Finally, the proteolytically processed species predominated both in vivo and ex vivo in organotypic cerebellar slice preparations, suggesting that GPR37L1 is rapidly processed to a signaling-inactive form. Our data indicate that the function of GPR37L1 in vivo is tightly regulated by metalloprotease-dependent N-terminal cleavage.
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8
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Park KC, Geleta B, Leck LYW, Paluncic J, Chiang S, Jansson PJ, Kovacevic Z, Richardson DR. Thiosemicarbazones suppress expression of the c-Met oncogene by mechanisms involving lysosomal degradation and intracellular shedding. J Biol Chem 2019; 295:481-503. [PMID: 31744884 DOI: 10.1074/jbc.ra119.011341] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 11/12/2019] [Indexed: 12/22/2022] Open
Abstract
Considering the role of proto-oncogene c-Met (c-Met) in oncogenesis, we examined the effects of the metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), and two NDRG1-inducing thiosemicarbazone-based agents, Dp44mT and DpC, on c-Met expression in DU145 and Huh7 cells. NDRG1 silencing without Dp44mT and DpC up-regulated c-Met expression, demonstrating that NDRG1 modulates c-Met levels. Dp44mT and DpC up-regulated NDRG1 by an iron-dependent mechanism and decreased c-Met levels, c-Met phosphorylation, and phosphorylation of its downstream effector, GRB2-associated binding protein 1 (GAB1). However, incubation with Dp44mT and DpC after NDRG1 silencing or silencing of the receptor tyrosine kinase inhibitor, mitogen-inducible gene 6 (MIG6), decreased c-Met and its phosphorylation, suggesting NDRG1- and MIG6-independent mechanism(s). Lysosomal inhibitors rescued the Dp44mT- and DpC-mediated c-Met down-regulation in DU145 cells. Confocal microscopy revealed that lysosomotropic agents and the thiosemicarbazones significantly increased co-localization between c-Met and lysosomal-associated membrane protein 2 (LAMP2). Moreover, generation of c-Met C-terminal fragment (CTF) and its intracellular domain (ICD) suggested metalloprotease-mediated cleavage. In fact, Dp44mT increased c-Met CTF while decreasing the ICD. Dp44mT and a γ-secretase inhibitor increased cellular c-Met CTF levels, suggesting that Dp44mT induces c-Met CTF levels by increasing metalloprotease activity. The broad metalloprotease inhibitors, EDTA and batimastat, partially prevented Dp44mT-mediated down-regulation of c-Met. In contrast, the ADAM inhibitor, TIMP metallopeptidase inhibitor 3 (TIMP-3), had no such effect, suggesting c-Met cleavage by another metalloprotease. Notably, Dp44mT did not induce extracellular c-Met shedding that could decrease c-Met levels. In summary, the thiosemicarbazones Dp44mT and DpC effectively inhibit oncogenic c-Met through lysosomal degradation and metalloprotease-mediated cleavage.
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Affiliation(s)
- Kyung Chan Park
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Bekesho Geleta
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Lionel Yi Wen Leck
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Jasmina Paluncic
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Shannon Chiang
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Patric J Jansson
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Zaklina Kovacevic
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia.
| | - Des R Richardson
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, University of Sydney, Sydney, New South Wales 2006, Australia; Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
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9
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Chen YS, Liu F, Luo YH, Fan Y, Xu FG, Li P, Zhou B, Pan XY, Wang CC, Cui L. EDNRB isoform 3 confers Temozolomide resistance in A375 melanoma cells by modulating membrane potential, reactive oxygen species and mitochondrial Ca 2. Cancer Manag Res 2019; 11:7353-7367. [PMID: 31496797 PMCID: PMC6689146 DOI: 10.2147/cmar.s208604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 07/10/2019] [Indexed: 12/24/2022] Open
Abstract
Background The role of endothelin receptor type B (EDNRB) isoform 3 involved in Temozolomide (TMZ)-induced melanoma cell death has not yet been elucidated. Methods The subcellular localization of EDNRB isoform 3 was determined by confocal and immunoblotting assays. Silencing EDNRB isoform 3 was performed by CRISPR/Cas9. Apoptosis was assessed by annexin V/propium iodide staining and caspases 3/7/9 activity. Mitochondrial membrane potential, reactive oxygen species and mitochondrial Ca2+ were measured by flow cytometry. Apoptosis protein array was applied. Results Confocal and immunoblot analyses indicate mitochondrial localization of EDNRB isoform 3 and the first N-terminal (1–22) amino acids are sufficient for its mitochondrial targeting. EDNRB isoform 3 depleted A375 cells significantly confers chemoresistance with mitochondrial depolarization, reduced reactive oxygen species, enhanced mitochondrial Ca2+ uptake and decreased caspase 9 activation. Additionally, apoptosis array shows that lack of EDNRB isoform 3 has relatively lower expression of phosphorylation of p53 at S392 and a slightly higher expression of Paraoxonase 2. Conclusion Our findings raise the possibility of targeting EDNRB isoform 3 as a new therapeutic strategy in combination with TMZ for melanoma treatment.
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Affiliation(s)
- Yun Shan Chen
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Fen Liu
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Yi Hong Luo
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Yue Fan
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Fang Gui Xu
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Pin Li
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Bei Zhou
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Xiu Yu Pan
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China
| | - Chi Chiu Wang
- Reproduction and Development Laboratory, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.,School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.,Department of Obstetrics and Gynaecology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Long Cui
- Department of Obstetrics and Gynaecology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, Guangdong, People's Republic of China.,Department of Obstetrics and Gynaecology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong
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10
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Dong F, Rues RB, Kazemi S, Dötsch V, Bernhard F. Molecular Determinants for Ligand Selectivity of the Cell-Free Synthesized Human Endothelin B Receptor. J Mol Biol 2018; 430:5105-5119. [PMID: 30342934 DOI: 10.1016/j.jmb.2018.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/02/2018] [Accepted: 10/12/2018] [Indexed: 01/14/2023]
Abstract
Extracellular domains of G-protein-coupled receptors act as initial molecular selectivity filters for subtype specific ligands and drugs. Chimeras of the human endothelin-B receptor containing structural units from the extracellular domains of the endothelin-A receptor were analyzed after their co-translational insertion into preformed nanodiscs. A short β-strand and a linker region in the second extracellular loop as well as parts of the extracellular N-terminal domain were identified as molecular discrimination sites for the endothelin-B receptor-selective agonists IRL1620, sarafotoxin 6c, 4Ala-ET-1 and ET-3, but not for the non-selective agonist ET-1 recognized by both endothelin receptors. A proposed second disulfide bridge in the endothelin-B receptor tethering the N-terminal domain with the third extracellular loop was not essential for ET-1 recognition and binding, but increased the receptor thermostability. We further demonstrate an experimental approach with cell-free synthesized engineered agonists to analyze the differential discrimination of peptide ligand topologies by the two endothelin receptors. The study is based on the engineering and cell-free insertion of G-protein-coupled receptors into defined membranes and may become interesting also for other targets as an alternative platform to reveal molecular details of ligand selectivity and ligand binding mechanisms.
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Affiliation(s)
- Fang Dong
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Ralf B Rues
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Sina Kazemi
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Frank Bernhard
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany.
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11
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Kii I, Hirahara-Owada S, Yamaguchi M, Niwa T, Koike Y, Sonamoto R, Ito H, Takahashi K, Yokoyama C, Hayashi T, Hosoya T, Watanabe Y. Quantification of receptor activation by oxytocin and vasopressin in endocytosis-coupled bioluminescence reduction assay using nanoKAZ. Anal Biochem 2018; 549:174-183. [PMID: 29627593 DOI: 10.1016/j.ab.2018.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 04/03/2018] [Accepted: 04/03/2018] [Indexed: 11/25/2022]
Abstract
Oxytocin (OXT) and arginine vasopressin (AVP) are structurally similar neuropeptide hormones that function as neurotransmitters in the brain, and have opposite key roles in social behaviors. These peptides bind to their G protein-coupled receptors (OXTR and AVPRs), inducing calcium ion-dependent signaling pathways and endocytosis of these receptors. Because selective agonists and antagonists for these receptors have been developed as therapeutic and diagnostic agents for diseases such as psychiatric disorders, facile methods are in demand for the evaluation of selectivity between these receptors. In this study, we developed a quantitative assay for OXT- and AVP-induced endocytosis of their receptors. The mutated Oplophorus luciferase, nanoKAZ, was fused to OXTR and AVPRs to enable rapid quantification of agonist-induced endocytosis by bioluminescence reduction. Agonist stimulation significantly decreases bioluminescence of nanoKAZ-fused receptors in living cells. Using this system, we evaluated clinically used OXTR antagonist atosiban and a reported pyrazinyltriazole derivative, hereby designated as PF13. Atosiban acted as an antagonist of AVPR1a, as well as an agonist for AVPR1b, whereas PF13 antagonized OXTR more selectively than atosiban, as reported previously. This paper shows a strategy for quantification of agonist-induced endocytosis of OXTR and AVPRs, and confirms its potent utility in the evaluation of agonists and antagonists.
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Affiliation(s)
- Isao Kii
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Compass to Healthy Life Research Complex Program, RIKEN Cluster for Science and Technology Hub, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
| | - Shino Hirahara-Owada
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Masataka Yamaguchi
- Functional Architecture Imaging Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Takashi Niwa
- Chemical Biology Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Yuka Koike
- Compass to Healthy Life Research Complex Program, RIKEN Cluster for Science and Technology Hub, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Rie Sonamoto
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Harumi Ito
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Laboratory of Chemical Bioscience, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan
| | - Kayo Takahashi
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Compass to Healthy Life Research Complex Program, RIKEN Cluster for Science and Technology Hub, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Chihiro Yokoyama
- Functional Architecture Imaging Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Takuya Hayashi
- Compass to Healthy Life Research Complex Program, RIKEN Cluster for Science and Technology Hub, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Functional Architecture Imaging Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Takamitsu Hosoya
- Chemical Biology Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Laboratory of Chemical Bioscience, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan
| | - Yasuyoshi Watanabe
- Pathophysiological and Health Science Team, Imaging Platform and Innovation Group, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Compass to Healthy Life Research Complex Program, RIKEN Cluster for Science and Technology Hub, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
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12
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Fine-Tuning Limited Proteolysis: A Major Role for Regulated Site-Specific O-Glycosylation. Trends Biochem Sci 2018; 43:269-284. [PMID: 29506880 DOI: 10.1016/j.tibs.2018.02.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/26/2018] [Accepted: 02/02/2018] [Indexed: 11/23/2022]
Abstract
Limited proteolytic processing is an essential and ubiquitous post-translational modification (PTM) affecting secreted proteins; failure to regulate the process is often associated with disease. Glycosylation is also a ubiquitous protein PTM and site-specific O-glycosylation in close proximity to sites of proteolysis can regulate and direct the activity of proprotein convertases, a disintegrin and metalloproteinases (ADAMs), and metalloproteinases affecting the activation or inactivation of many classes of proteins, including G-protein-coupled receptors (GPCRs). Here, we summarize the emerging data that suggest O-glycosylation to be a key regulator of limited proteolysis, and highlight the potential for crosstalk between multiple PTMs.
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13
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Goth CK, Tuhkanen HE, Khan H, Lackman JJ, Wang S, Narimatsu Y, Hansen LH, Overall CM, Clausen H, Schjoldager KT, Petäjä-Repo UE. Site-specific O-Glycosylation by Polypeptide N-Acetylgalactosaminyltransferase 2 (GalNAc-transferase T2) Co-regulates β 1-Adrenergic Receptor N-terminal Cleavage. J Biol Chem 2017; 292:4714-4726. [PMID: 28167537 PMCID: PMC5377785 DOI: 10.1074/jbc.m116.730614] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 01/29/2017] [Indexed: 01/08/2023] Open
Abstract
The β1-adrenergic receptor (β1AR) is a G protein-coupled receptor (GPCR) and the predominant adrenergic receptor subtype in the heart, where it mediates cardiac contractility and the force of contraction. Although it is the most important target for β-adrenergic antagonists, such as β-blockers, relatively little is yet known about its regulation. We have shown previously that β1AR undergoes constitutive and regulated N-terminal cleavage participating in receptor down-regulation and, moreover, that the receptor is modified by O-glycosylation. Here we demonstrate that the polypeptide GalNAc-transferase 2 (GalNAc-T2) specifically O-glycosylates β1AR at five residues in the extracellular N terminus, including the Ser-49 residue at the location of the common S49G single-nucleotide polymorphism. Using in vitro O-glycosylation and proteolytic cleavage assays, a cell line deficient in O-glycosylation, GalNAc-T-edited cell line model systems, and a GalNAc-T2 knock-out rat model, we show that GalNAc-T2 co-regulates the metalloproteinase-mediated limited proteolysis of β1AR. Furthermore, we demonstrate that impaired O-glycosylation and enhanced proteolysis lead to attenuated receptor signaling, because the maximal response elicited by the βAR agonist isoproterenol and its potency in a cAMP accumulation assay were decreased in HEK293 cells lacking GalNAc-T2. Our findings reveal, for the first time, a GPCR as a target for co-regulatory functions of site-specific O-glycosylation mediated by a unique GalNAc-T isoform. The results provide a new level of β1AR regulation that may open up possibilities for new therapeutic strategies for cardiovascular diseases.
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Affiliation(s)
- Christoffer K Goth
- From the Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Hanna E Tuhkanen
- the Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland
| | - Hamayun Khan
- the Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland
| | - Jarkko J Lackman
- the Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland
| | - Shengjun Wang
- From the Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Yoshiki Narimatsu
- From the Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Lasse H Hansen
- the Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospital, DK-2100 Copenhagen Ø, Denmark and
| | - Christopher M Overall
- the Centre for Blood Research, Department of Oral Biological and Medical Sciences, and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Henrik Clausen
- From the Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Katrine T Schjoldager
- From the Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark,
| | - Ulla E Petäjä-Repo
- the Medical Research Center Oulu, Research Unit of Biomedicine, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland,
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14
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Tien WS, Chen JH, Wu KP. SheddomeDB: the ectodomain shedding database for membrane-bound shed markers. BMC Bioinformatics 2017; 18:42. [PMID: 28361715 PMCID: PMC5374707 DOI: 10.1186/s12859-017-1465-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND A number of membrane-anchored proteins are known to be released from cell surface via ectodomain shedding. The cleavage and release of membrane proteins has been shown to modulate various cellular processes and disease pathologies. Numerous studies revealed that cell membrane molecules of diverse functional groups are subjected to proteolytic cleavage, and the released soluble form of proteins may modulate various signaling processes. Therefore, in addition to the secreted protein markers that undergo secretion through the secretory pathway, the shed membrane proteins may comprise an additional resource of noninvasive and accessible biomarkers. In this context, identifying the membrane-bound proteins that will be shed has become important in the discovery of clinically noninvasive biomarkers. Nevertheless, a data repository for biological and clinical researchers to review the shedding information, which is experimentally validated, for membrane-bound protein shed markers is still lacking. RESULTS In this study, the database SheddomeDB was developed to integrate publicly available data of the shed membrane proteins. A comprehensive literature survey was performed to collect the membrane proteins that were verified to be cleaved or released in the supernatant by immunological-based validation experiments. From 436 studies on shedding, 401 validated shed membrane proteins were included, among which 199 shed membrane proteins have not been annotated or validated yet by existing cleavage databases. SheddomeDB attempted to provide a comprehensive shedding report, including the regulation of shedding machinery and the related function or diseases involved in the shedding events. In addition, our published tool ShedP was embedded into SheddomeDB to support researchers for predicting the shedding event on unknown or unrecorded membrane proteins. CONCLUSIONS To the best of our knowledge, SheddomeDB is the first database for the identification of experimentally validated shed membrane proteins and currently may provide the most number of membrane proteins for reviewing the shedding information. The database included membrane-bound shed markers associated with numerous cellular processes and diseases, and some of these markers are potential novel markers because they are not annotated or validated yet in other databases. SheddomeDB may provide a useful resource for discovering membrane-bound shed markers. The interactive web of SheddomeDB is publicly available at http://bal.ym.edu.tw/SheddomeDB/ .
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Affiliation(s)
- Wei-Sheng Tien
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.,Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan
| | - Jun-Hong Chen
- Department of Computer Science, National Taipei University of Education, Taipei, 106, Taiwan
| | - Kun-Pin Wu
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.
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15
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Coleman JLJ, Ngo T, Smith NJ. The G protein-coupled receptor N-terminus and receptor signalling: N-tering a new era. Cell Signal 2017; 33:1-9. [PMID: 28188824 DOI: 10.1016/j.cellsig.2017.02.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 02/06/2017] [Indexed: 01/22/2023]
Abstract
G protein-coupled receptors (GPCRs) are a vast family of membrane-traversing proteins, essential to the ability of eukaryotic life to detect, and mount an intracellular response to, a diverse range of extracellular stimuli. GPCRs have evolved with archetypal features including an extracellular N-terminus and intracellular C-terminus that flank a transmembrane structure of seven sequential helices joined by intracellular and extracellular loops. These structural domains contribute to the ability of a GPCR to be correctly synthesised and inserted into the cell membrane, to interact with its cognate ligand(s) and to couple with signal-transducing heterotrimeric G proteins, allowing the activated receptor to selectively modulate a number of signalling cascades. Whilst well known for its importance in receptor translation and trafficking, the GPCR N-terminus is underexplored as a participant in receptor signalling. This review aims to discuss and integrate recent advances in knowledge of the vital roles of the GPCR N-terminus in receptor signalling.
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Affiliation(s)
- James L J Coleman
- Molecular Pharmacology Group, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia.
| | - Tony Ngo
- Molecular Pharmacology Group, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia
| | - Nicola J Smith
- Molecular Pharmacology Group, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia.
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16
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Borrull A, Allard B, Wijkhuisen A, Herbet A, Lamourette P, Birouk W, Leiber D, Tanfin Z, Ducancel F, Boquet D, Couraud JY, Robin P. Rendomab B4, a monoclonal antibody that discriminates the human endothelin B receptor of melanoma cells and inhibits their migration. MAbs 2016; 8:1371-1385. [PMID: 27390909 DOI: 10.1080/19420862.2016.1208865] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Metastatic melanoma is an aggressive cancer with a poor prognostic, and the design of new targeted drugs to treat melanoma is a therapeutic challenge. A promising approach is to produce monoclonal antibodies (mAbs) against the endothelin B receptor (ETB), which is known to be overexpressed in melanoma and to contribute to proliferation, migration and vasculogenic mimicry associated with invasiveness of this cancer. We previously described rendomab-B1, a mAb produced by DNA immunization. It is endowed with remarkable characteristics in term of affinity, specificity and antagonist properties against human ETB expressed by the endothelial cells, but, surprisingly, had poor affinity for ETB expressed by melanoma cells. This characteristic strongly suggested the existence of a tumor-specific ETB form. In the study reported here, we identified a new mAb, rendomab-B4, which, in contrast to rendomab-B1, binds ETB expressed on UACC-257, WM-266-4 and SLM8 melanoma cells. Moreover, after binding to UACC-257 cells, rendomab-B4 is internalized and colocalizes with the endosomal protein EEA-1. Interestingly, rendomab-B4, despite its inability to compete with endothelin binding, is able to inhibit phospholipase C pathway and migration induced by endothelin. By contrast, rendomab-B4 fails to decrease ERK1/2 phosphorylation induced by endothelin, suggesting a biased effect on ETB. These particular properties make rendomab-B4 an interesting tool to analyze ETB-structure/function and a promising starting point for the development of new immunological tools in the field of melanoma therapeutics.
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Affiliation(s)
- Aurélie Borrull
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France.,b Université Paris Sud-11 , CNRS, UMR 8619, IBBMC , Orsay , France
| | - Bertrand Allard
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France
| | - Anne Wijkhuisen
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France.,c Université Paris Diderot, Sorbonne Paris Cité , Gif-sur-Yvette , France
| | - Amaury Herbet
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France
| | - Patricia Lamourette
- d CEA, iBiTec-S, SPI, Laboratoire d'Etude et de Recherche en Immunoanalyse , Gif-sur-Yvette , France
| | - Wided Birouk
- b Université Paris Sud-11 , CNRS, UMR 8619, IBBMC , Orsay , France
| | - Denis Leiber
- b Université Paris Sud-11 , CNRS, UMR 8619, IBBMC , Orsay , France
| | - Zahra Tanfin
- b Université Paris Sud-11 , CNRS, UMR 8619, IBBMC , Orsay , France
| | - Frédéric Ducancel
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France
| | - Didier Boquet
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France
| | - Jean-Yves Couraud
- a CEA, iBiTec-S, SPI, Laboratoire d'Ingénierie des Anticorps pour la Santé , Gif-sur-Yvette , France.,c Université Paris Diderot, Sorbonne Paris Cité , Gif-sur-Yvette , France
| | - Philippe Robin
- b Université Paris Sud-11 , CNRS, UMR 8619, IBBMC , Orsay , France
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17
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Coleman JLJ, Ngo T, Schmidt J, Mrad N, Liew CK, Jones NM, Graham RM, Smith NJ. Metalloprotease cleavage of the N terminus of the orphan G protein-coupled receptor GPR37L1 reduces its constitutive activity. Sci Signal 2016; 9:ra36. [PMID: 27072655 DOI: 10.1126/scisignal.aad1089] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Little is known about the pharmacology or physiology of GPR37L1, a G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor that is abundant in the cerebellum. Mice deficient in this receptor exhibit precocious cerebellar development and hypertension. We showed that GPR37L1 coupled to the G protein Gα(s) when heterologously expressed in cultured cells in the absence of any added ligand, whereas a mutant receptor that lacked the amino terminus was inactive. Conversely, inhibition of ADAMs (a disintegrin and metalloproteases) enhanced receptor activity, indicating that the presence of the amino terminus is necessary for GPR37L1 signaling. Metalloprotease-dependent processing of GPR37L1 was evident in rodent cerebellum, where we detected predominantly the cleaved, inactive form. However, comparison of the accumulation of cAMP (adenosine 3',5'-monophosphate) in response to phosphodiesterase inhibition in cerebellar slice preparations from wild-type and GPR37L1-null mice showed that some constitutive signaling remained in the wild-type mice. In reporter assays of Gα(s) or Gα(i) signaling, the synthetic, prosaposin-derived peptide prosaptide (TX14A) did not increase GPR37L1 activity. Our data indicate that GPR37L1 may be a constitutively active receptor, or perhaps its ligand is present under the conditions that we used for analysis, and that the activity of this receptor is instead controlled by signals that regulate metalloprotease activity in the tissue.
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Affiliation(s)
- James L J Coleman
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia. St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Tony Ngo
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia. St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Johannes Schmidt
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Nadine Mrad
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Chu Kong Liew
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Nicole M Jones
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, Kensington, New South Wales 2033, Australia
| | - Robert M Graham
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia. St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Nicola J Smith
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia. St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia.
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18
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Mattila SO, Tuusa JT, Petäjä-Repo UE. The Parkinson's-disease-associated receptor GPR37 undergoes metalloproteinase-mediated N-terminal cleavage and ectodomain shedding. J Cell Sci 2016; 129:1366-77. [PMID: 26869225 DOI: 10.1242/jcs.176115] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 02/08/2016] [Indexed: 12/20/2022] Open
Abstract
The G-protein-coupled receptor 37 ( GPR37) has been implicated in the juvenile form of Parkinson's disease, in dopamine signalling and in the survival of dopaminergic cells in animal models. The structure and function of the receptor, however, have remained enigmatic. Here, we demonstrate that although GPR37 matures and is exported from the endoplasmic reticulum in a normal manner upon heterologous expression in HEK293 and SH-SY5Y cells, its long extracellular N-terminus is subject to metalloproteinase-mediated limited proteolysis between E167 and Q168. The proteolytic processing is a rapid and efficient process that occurs constitutively. Moreover, the GPR37 ectodomain is released from cells by shedding, a phenomenon rarely described for GPCRs. Immunofluorescence microscopy further established that although full-length receptors are present in the secretory pathway until the trans-Golgi network, GPR37 is expressed at the cell surface predominantly in the N-terminally truncated form. This notion was verified by flow cytometry and cell surface biotinylation assays. These new findings on the GPR37 N-terminal limited proteolysis may help us to understand the role of this GPCR in the pathophysiology of Parkinson's disease and in neuronal function in general.
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Affiliation(s)
- S Orvokki Mattila
- Medical Research Center Oulu, and Cancer and Translational Medicine Research Unit, University of Oulu, Oulu FI-90014, Finland
| | - Jussi T Tuusa
- Medical Research Center Oulu, and Cancer and Translational Medicine Research Unit, University of Oulu, Oulu FI-90014, Finland
| | - Ulla E Petäjä-Repo
- Medical Research Center Oulu, and Cancer and Translational Medicine Research Unit, University of Oulu, Oulu FI-90014, Finland
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19
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Regulation of GPCR Anterograde Trafficking by Molecular Chaperones and Motifs. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:289-305. [PMID: 26055064 DOI: 10.1016/bs.pmbts.2015.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
G protein-coupled receptors (GPCRs) make up a superfamily of integral membrane proteins that respond to a wide variety of extracellular stimuli, giving them an important role in cell function and survival. They have also proven to be valuable targets in the fight against various diseases. As such, GPCR signal regulation has received considerable attention over the last few decades. With the amplitude of signaling being determined in large part by receptor density at the plasma membrane, several endogenous mechanisms for modulating GPCR expression at the cell surface have come to light. It has been shown that cell surface expression is determined by both exocytic and endocytic processes. However, the body of knowledge surrounding GPCR trafficking from the endoplasmic reticulum to the plasma membrane, commonly known as anterograde trafficking, has considerable room for growth. We focus here on the current paradigms of anterograde GPCR trafficking. We will discuss the regulatory role of both the general and "nonclassical private" chaperone systems in GPCR trafficking as well as conserved motifs that serve as modulators of GPCR export from the endoplasmic reticulum and Golgi apparatus. Together, these topics summarize some of the known mechanisms by which the cell regulates anterograde GPCR trafficking.
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20
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Barr TP, Kornberg D, Montmayeur JP, Long M, Reichheld S, Strichartz GR. Validation of endothelin B receptor antibodies reveals two distinct receptor-related bands on Western blot. Anal Biochem 2015; 468:28-33. [PMID: 25232999 DOI: 10.1016/j.ab.2014.09.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 08/29/2014] [Accepted: 09/08/2014] [Indexed: 10/24/2022]
Abstract
Antibodies are important tools for the study of protein expression but are often used without full validation. In this study, we used Western blots to characterize antibodies targeted to the N or C terminal (NT or CT, respectively) and the second or third intracellular loop (IL2 or IL3, respectively) of the endothelin B receptor (ETB). The IL2-targeted antibody accurately detected endogenous ETB expression in rat brain and cultured rat astrocytes by labeling a 50-kDa band, the expected weight of full-length ETB. However, this antibody failed to detect transfected ETB in HEK293 cultures. In contrast, the NT-targeted antibody accurately detected endogenous ETB in rat astrocyte cultures and transfected ETB in HEK293 cultures by labeling a 37-kDa band but failed to detect endogenous ETB in rat brain. Bands detected by the CT- or IL3-targeted antibody were found to be unrelated to ETB. Our findings show that functional ETB can be detected at 50 or 37kDa on Western blot, with drastic differences in antibody affinity for these bands. The 37-kDa band likely reflects ETB processing, which appears to be dependent on cell type and/or culture condition.
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Affiliation(s)
- Travis P Barr
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA
| | - Daniel Kornberg
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA
| | - Jean-Pierre Montmayeur
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA
| | - Melinda Long
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA
| | - Stephen Reichheld
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA
| | - Gary R Strichartz
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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Teichmann A, Gibert A, Lampe A, Grzesik P, Rutz C, Furkert J, Schmoranzer J, Krause G, Wiesner B, Schülein R. The specific monomer/dimer equilibrium of the corticotropin-releasing factor receptor type 1 is established in the endoplasmic reticulum. J Biol Chem 2014; 289:24250-62. [PMID: 24966326 DOI: 10.1074/jbc.m114.553644] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
G protein-coupled receptors (GPCRs) represent the most important drug targets. Although the smallest functional unit of a GPCR is a monomer, it became clear in the past decades that the vast majority of the receptors form dimers. Only very recently, however, data were presented that some receptors may in fact be expressed as a mixture of monomers and dimers and that the interaction of the receptor protomers is dynamic. To date, equilibrium measurements were restricted to the plasma membrane due to experimental limitations. We have addressed the question as to where this equilibrium is established for the corticotropin-releasing factor receptor type 1. By developing a novel approach to analyze single molecule fluorescence cross-correlation spectroscopy data for intracellular membrane compartments, we show that the corticotropin-releasing factor receptor type 1 has a specific monomer/dimer equilibrium that is already established in the endoplasmic reticulum (ER). It remains constant at the plasma membrane even following receptor activation. Moreover, we demonstrate for seven additional GPCRs that they are expressed in specific but substantially different monomer/dimer ratios. Although it is well known that proteins may dimerize in the ER in principle, our data show that the ER is also able to establish the specific monomer/dimer ratios of GPCRs, which sheds new light on the functions of this compartment.
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Affiliation(s)
- Anke Teichmann
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Arthur Gibert
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - André Lampe
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Paul Grzesik
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Claudia Rutz
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Jens Furkert
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Jan Schmoranzer
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Gerd Krause
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Burkhard Wiesner
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Ralf Schülein
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany
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Functional properties of cell-free expressed human endothelin A and endothelin B receptors in artificial membrane environments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2182-92. [DOI: 10.1016/j.bbamem.2013.05.031] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/27/2013] [Accepted: 05/29/2013] [Indexed: 01/06/2023]
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Intracrine endothelin signaling evokes IP3-dependent increases in nucleoplasmic Ca²⁺ in adult cardiac myocytes. J Mol Cell Cardiol 2013; 62:189-202. [PMID: 23756157 DOI: 10.1016/j.yjmcc.2013.05.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Revised: 05/30/2013] [Accepted: 05/31/2013] [Indexed: 12/17/2022]
Abstract
Endothelin receptors are present on the nuclear membranes in adult cardiac ventricular myocytes. The objectives of the present study were to determine 1) which endothelin receptor subtype is in cardiac nuclear membranes, 2) if the receptor and ligand traffic from the cell surface to the nucleus, and 3) the effect of increased intracellular ET-1 on nuclear Ca(2+) signaling. Confocal microscopy using fluorescently-labeled endothelin analogs confirmed the presence of ETB at the nuclear membrane of rat cardiomyocytes in skinned-cells and isolated nuclei. Furthermore, in both cardiac myocytes and aortic endothelial cells, endocytosed ET:ETB complexes translocated to lysosomes and not the nuclear envelope. Although ETA and ETB can form heterodimers, the presence or absence of ETA did not alter ETB trafficking. Treatment of isolated nuclei with peptide: N-glycosidase F did not alter the electrophoretic mobility of ETB. The absence of N-glycosylation further indicates that these receptors did not originate at the cell surface. Intracellular photolysis of a caged ET-1 analog ([Trp-ODMNB(21)]ET-1) evoked an increase in nucleoplasmic Ca(2+) ([Ca(2+)]n) that was attenuated by inositol 1,4,5-trisphosphate receptor inhibitor 2-aminoethoxydiphenyl borate and prevented by pre-treatment with ryanodine. A caged cell-permeable analog of the ETB-selective antagonist IRL-2500 blocked the ability of intracellular cET-1 to increase [Ca(2+)]n whereas extracellular application of ETA and ETB receptor antagonists did not. These data suggest that 1) the endothelin receptor in the cardiac nuclear membranes is ETB, 2) ETB traffics directly to the nuclear membrane after biosynthesis, 3) exogenous endothelins are not ligands for ETB on nuclear membranes, and 4) ETB associated with the nuclear membranes regulates nuclear Ca(2+) signaling.
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Wilkinson S, Lu ZH, Megens HJ, Archibald AL, Haley C, Jackson IJ, Groenen MAM, Crooijmans RPMA, Ogden R, Wiener P. Signatures of diversifying selection in European pig breeds. PLoS Genet 2013; 9:e1003453. [PMID: 23637623 PMCID: PMC3636142 DOI: 10.1371/journal.pgen.1003453] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 02/25/2013] [Indexed: 01/14/2023] Open
Abstract
Following domestication, livestock breeds have experienced intense selection pressures for the development of desirable traits. This has resulted in a large diversity of breeds that display variation in many phenotypic traits, such as coat colour, muscle composition, early maturity, growth rate, body size, reproduction, and behaviour. To better understand the relationship between genomic composition and phenotypic diversity arising from breed development, the genomes of 13 traditional and commercial European pig breeds were scanned for signatures of diversifying selection using the Porcine60K SNP chip, applying a between-population (differentiation) approach. Signatures of diversifying selection between breeds were found in genomic regions associated with traits related to breed standard criteria, such as coat colour and ear morphology. Amino acid differences in the EDNRB gene appear to be associated with one of these signatures, and variation in the KITLG gene may be associated with another. Other selection signals were found in genomic regions including QTLs and genes associated with production traits such as reproduction, growth, and fat deposition. Some selection signatures were associated with regions showing evidence of introgression from Asian breeds. When the European breeds were compared with wild boar, genomic regions with high levels of differentiation harboured genes related to bone formation, growth, and fat deposition. The domestic pig, an important source of protein worldwide, was domesticated from the ancestral wild boar in multiple locations throughout the world. In Europe, local types were developed following domestication, but phenotypically distinct breeds only arose in the eighteenth century with the advent of systematic breeding. Recently developed molecular tools for pigs (as well as other livestock species) now allow a genetic characterisation of breed histories, including identification of regions of the genome that have been under selection in the establishment of breeds. We have applied these tools to identify genomic regions associated with breed development in a set of commercial and traditional pig breeds. We found strong evidence of genetic differentiation between breeds near genes associated with traits that are used to define breed standards, such as ear morphology and coat colour, as well as in regions of the genome that are associated with pork production traits. It is well documented that crosses with Asian pigs have been used to modify European breeds. We have found evidence of genetic influence from Asian pigs in European breeds, again in regions of the genome associated with breed standard characteristics, including ear shape and coat colour, as well as production traits.
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Affiliation(s)
- Samantha Wilkinson
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Zen H. Lu
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Hendrik-Jan Megens
- Animal Breeding and Genomics Centre, Wageningen UR, Wageningen, The Netherlands
| | - Alan L. Archibald
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Chris Haley
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Ian J. Jackson
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | | | | | - Rob Ogden
- Wildgenes Laboratory, Royal Zoological Society of Scotland, Edinburgh, United Kingdom
| | - Pamela Wiener
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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25
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Allard B, Wijkhuisen A, Borrull A, Deshayes F, Priam F, Lamourette P, Ducancel F, Boquet D, Couraud JY. Generation and characterization of rendomab-B1, a monoclonal antibody displaying potent and specific antagonism of the human endothelin B receptor. MAbs 2012; 5:56-69. [PMID: 23221682 DOI: 10.4161/mabs.22696] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Endothelin B receptor (ETBR) is a G protein-coupled receptor able to bind equally to the three identified human endothelin peptides. It is expressed primarily on vascular endothelial cells and involved in various physiological processes including vascular tone homeostasis, enteric nervous system development, melanogenesis and angiogenesis. Furthermore, overactivation or overexpression of ETBR have been associated with the development of various diseases such as cardiovascular disorders and cancers. Therefore, ETBR appears to be relevant target for the therapy or diagnosis of highly prevalent human diseases. In this study, we report the in vitro characterization of rendomab-B1, a monoclonal antibody (mAb) obtained by genetic immunization, which selectively recognizes the native form of human ETBR (hETBR). Rendomab-B1 is the first-reported mAb that behaves as a potent antagonist of hETBR. It recognizes an original extracellular conformational epitope on the receptor, distinct from the endothelin-1 (ET-1) binding site. Rendomab-B1 not only blocks ET-1-induced calcium signaling pathway and triggers rapid receptor internalization on recombinant hETBR-expressing cells, but also exerts pharmacological activities on human vascular endothelial cells, reducing both cell viability and ET-1-induced hETBR synthesis. In addition, binding experiments using rendomab-B1 on different melanoma cell lines reveal the structural and functional heterogeneity of hETBR expressed at the surface of these cancer cells, strongly suggesting the existence of tumor-specific receptors. Collectively, our results underscore the value of rendomab-B1 for research, therapeutic and diagnostic applications dealing with hETBR.
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Affiliation(s)
- Bertrand Allard
- CEA, iBiTecS, SPI, Laboratoire d'Ingénierie des Anticorps pour Santé, Gif sur Yvette, France
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26
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Cook JL, Re RN. Lessons from in vitro studies and a related intracellular angiotensin II transgenic mouse model. Am J Physiol Regul Integr Comp Physiol 2011; 302:R482-93. [PMID: 22170617 DOI: 10.1152/ajpregu.00493.2011] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the classical renin-angiotensin system, circulating ANG II mediates growth stimulatory and hemodynamic effects through the plasma membrane ANG II type I receptor, AT1. ANG II also exists in the intracellular space in some native cells, and tissues and can be upregulated in diseases, including hypertension and diabetes. Moreover, intracellular AT1 receptors can be found associated with endosomes, nuclei, and mitochondria. Intracellular ANG II can function in a canonical fashion through the native receptor and also in a noncanonical fashion through interaction with alternative proteins. Likewise, the receptor and proteolytic fragments of the receptor can function independently of ANG II. Participation of the receptor and ligand in alternative intracellular pathways may serve to amplify events that are initiated at the plasma membrane. We review historical and current literature relevant to ANG II, compared with other intracrines, in tissue culture and transgenic models. In particular, we describe a new transgenic mouse model, which demonstrates that intracellular ANG II is linked to high blood pressure. Appreciation of the diverse, pleiotropic intracellular effects of components of the renin-angiotensin system should lead to alternative disease treatment targets and new therapies.
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Affiliation(s)
- Julia L Cook
- Laboratory of Molecular Genetics, Department of Research, New Orleans, LA 70121, USA.
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27
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Cook JL, Singh A, DeHaro D, Alam J, Re RN. Expression of a naturally occurring angiotensin AT(1) receptor cleavage fragment elicits caspase-activation and apoptosis. Am J Physiol Cell Physiol 2011; 301:C1175-85. [PMID: 21813711 DOI: 10.1152/ajpcell.00040.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Several transmembrane receptors are documented to accumulate in nuclei, some as holoreceptors and others as cleaved receptor products. Our prior studies indicate that a population of the 7-transmembrane angiotensin type-1 receptor (AT(1)R) is cleaved in a ligand-augmented manner after which the cytoplasmic, carboxy-terminal cleavage fragment (CF) traffics to the nucleus. In the present report, we determine the precise cleavage site within the AT(1)R by mass spectrometry and Edman sequencing. Cleavage occurs between Leu(305) and Gly(306) at the junction of the seventh transmembrane domain and the intracellular cytoplasmic carboxy-terminal domain. To evaluate the function of the CF distinct from the holoreceptor, we generated a construct encoding the CF as an in-frame yellow fluorescent protein fusion. The CF accumulates in nuclei and induces apoptosis in CHO-K1 cells, rat aortic smooth muscle cells (RASMCs), MCF-7 human breast adenocarcinoma cells, and H9c2 rat cardiomyoblasts. All cell types show nuclear fragmentation and disintegration, as well as evidence for phosphotidylserine displacement in the plasma membrane and activated caspases. RASMCs specifically showed a 5.2-fold increase (P < 0.001) in CF-induced active caspases compared with control and a 7.2-fold increase (P < 0.001) in cleaved caspase-3 (Asp174). Poly(ADP-ribose)polymerase was upregulated 4.8-fold (P < 0.001) in CF expressing cardiomyoblasts and colocalized with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). CF expression also induces DNA laddering, the gold-standard for apoptosis in all cell types studied. CF-induced apoptosis, therefore, appears to be a general phenomenon as it is observed in multiple cell types including smooth muscle cells and cardiomyoblasts.
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Affiliation(s)
- Julia L Cook
- Laboratory of Molecular Genetics, Department of Research, Ochsner Clinic Foundation, New Orleans, LA 70121, USA.
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28
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Westendorf C, Schmidt A, Coin I, Furkert J, Ridelis I, Zampatis D, Rutz C, Wiesner B, Rosenthal W, Beyermann M, Schülein R. Inhibition of biosynthesis of human endothelin B receptor by the cyclodepsipeptide cotransin. J Biol Chem 2011; 286:35588-35600. [PMID: 21808059 DOI: 10.1074/jbc.m111.239244] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The specific inhibition of the biosynthesis of target proteins is a relatively novel strategy in pharmacology and is based mainly on antisense approaches (e.g. antisense oligonucleotides or RNA interference). Recently, a novel class of substances was described acting at a later step of protein biosynthesis. The cyclic heptadepsipeptides CAM741 and cotransin were shown to inhibit selectively the biosynthesis of a small subset of secretory proteins by preventing stable insertion of the nascent chains into the Sec61 translocon complex at the endoplasmic reticulum membrane (Besemer, J., Harant, H., Wang, S., Oberhauser, B., Marquardt, K., Foster, C. A., Schreiner, E. P., de Vries, J. E., Dascher-Nadel, C., and Lindley, I. J. (2005) Nature 436, 290-293; Garrison, J. L., Kunkel, E. J., Hegde, R. S., and Taunton, J. (2005) Nature 436, 285-289). These peptides act in a signal sequence-discriminatory manner, which explains their selectivity. Here, we have analyzed the cotransin sensitivity of various G protein-coupled receptors in transfected HEK 293 cells. We show that the biosynthesis of the human endothelin B receptor (ET(B)R) is highly sensitive to cotransin, in contrast to that of the other G protein-coupled receptors analyzed. Using a novel biosynthesis assay based on fusions with the photoconvertible Kaede protein, we show that the IC(50) value of cotransin action on ET(B)R biosynthesis is 5.4 μm and that ET(B)R signaling could be completely blocked by treating cells with 30 μm cotransin. Taken together, our data add an integral membrane protein, namely the ET(B)R, to the small group of cotransin-sensitive proteins.
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Affiliation(s)
- Carolin Westendorf
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Antje Schmidt
- Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Irene Coin
- Salk Institute for Biological Studies, La Jolla, California 92037-1099
| | - Jens Furkert
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Ingrid Ridelis
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Bereich Molekulare Pharmakologie und Zellbiologie, Charité-Universitätsmedizin Berlin, Thielallee 67-73, 14195 Berlin, Germany
| | - Dimitris Zampatis
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Claudia Rutz
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Burkhard Wiesner
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Walter Rosenthal
- Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Bereich Molekulare Pharmakologie und Zellbiologie, Charité-Universitätsmedizin Berlin, Thielallee 67-73, 14195 Berlin, Germany
| | - Michael Beyermann
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Ralf Schülein
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
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29
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Membrane-delimited proteolytic regulation of opioid receptors. Brain Res 2011; 1386:25-34. [DOI: 10.1016/j.brainres.2011.02.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/31/2011] [Accepted: 02/14/2011] [Indexed: 11/21/2022]
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30
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Asundi J, Reed C, Arca J, McCutcheon K, Ferrando R, Clark S, Luis E, Tien J, Firestein R, Polakis P. An Antibody–Drug Conjugate Targeting the Endothelin B Receptor for the Treatment of Melanoma. Clin Cancer Res 2011; 17:965-75. [DOI: 10.1158/1078-0432.ccr-10-2340] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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31
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Schulz K, Rutz C, Westendorf C, Ridelis I, Vogelbein S, Furkert J, Schmidt A, Wiesner B, Schülein R. The pseudo signal peptide of the corticotropin-releasing factor receptor type 2a decreases receptor expression and prevents Gi-mediated inhibition of adenylyl cyclase activity. J Biol Chem 2010; 285:32878-32887. [PMID: 20682782 DOI: 10.1074/jbc.m110.129627] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The corticotropin-releasing factor receptor type 2a (CRF(2(a))R) belongs to the family of G protein-coupled receptors. The receptor possesses an N-terminal pseudo signal peptide that is unable to mediate targeting of the nascent chain to the endoplasmic reticulum membrane during early receptor biogenesis. The pseudo signal peptide remains uncleaved and consequently forms an additional hydrophobic receptor domain with unknown function that is unique within the large G protein-coupled receptor protein family. Here, we have analyzed the functional significance of this domain in comparison with the conventional signal peptide of the homologous corticotropin-releasing factor receptor type 1 (CRF(1)R). We show that the presence of the pseudo signal peptide leads to a very low cell surface receptor expression of the CRF(2(a))R in comparison with the CRF(1)R. Moreover, whereas the presence of the pseudo signal peptide did not affect coupling to the G(s) protein, G(i)-mediated inhibition of adenylyl cyclase activity was abolished. The properties mediated by the pseudo signal peptide were entirely transferable to the CRF(1)R in signal peptide exchange experiments. Taken together, our results show that signal peptides do not only influence early protein biogenesis. In the case of the corticotropin-releasing factor receptor subtypes, the use of conventional and pseudo signal peptides have an unexpected influence on signal transduction.
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Affiliation(s)
- Katharina Schulz
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Claudia Rutz
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Carolin Westendorf
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Ingrid Ridelis
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Susanne Vogelbein
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Jens Furkert
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Antje Schmidt
- Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Burkhard Wiesner
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Ralf Schülein
- From the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
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32
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Hakalahti AE, Vierimaa MM, Lilja MK, Kumpula EP, Tuusa JT, Petäjä-Repo UE. Human beta1-adrenergic receptor is subject to constitutive and regulated N-terminal cleavage. J Biol Chem 2010; 285:28850-61. [PMID: 20587416 DOI: 10.1074/jbc.m110.149989] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The beta(1)-adrenergic receptor (beta(1)AR) is the predominant betaAR in the heart, mediating the catecholamine-stimulated increase in cardiac rate and force of contraction. Regulation of this important G protein-coupled receptor is nevertheless poorly understood. We describe here the biosynthetic profile of the human beta(1)AR and reveal novel features relevant to its regulation using an inducible heterologous expression system in HEK293(i) cells. Metabolic pulse-chase labeling and cell surface biotinylation assays showed that the synthesized receptors are efficiently and rapidly transported to the cell surface. The N terminus of the mature receptor is extensively modified by sialylated mucin-type O-glycosylation in addition to one N-glycan attached to Asn(15). Furthermore, the N terminus was found to be subject to limited proteolysis, resulting in two membrane-bound C-terminal fragments. N-terminal sequencing of the fragments identified two cleavage sites between Arg(31) and Leu(32) and Pro(52) and Leu(53), which were confirmed by cleavage site and truncation mutants. Metalloproteinase inhibitors were able to inhibit the cleavage, suggesting that it is mediated by a matrix metalloproteinase or a disintegrin and metalloproteinase (ADAM) family member. Most importantly, the N-terminal cleavage was found to occur not only in vitro but also in vivo. Receptor activation mediated by the betaAR agonist isoproterenol enhanced the cleavage in a concentration- and time-dependent manner, and it was also enhanced by direct stimulation of protein kinase C and adenylyl cyclase. Mutation of the Arg(31)-Leu(32) cleavage site stabilized the mature receptor. We hypothesize that the N-terminal cleavage represents a novel regulatory mechanism of cell surface beta(1)ARs.
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Affiliation(s)
- Anna E Hakalahti
- Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, FI-90014 Oulu, Finland
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33
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Grossmann S, Higashiyama S, Oksche A, Schaefer M, Tannert A. Localisation of endothelin B receptor variants to plasma membrane microdomains and its effects on downstream signalling. Mol Membr Biol 2009; 26:279-92. [PMID: 19757321 DOI: 10.1080/09687680903191682] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The endothelin B (ET(B)) receptor can undergo a proteolytic cleavage resulting in an unglycosylated N-terminally truncated receptor. We investigated whether ET(B) receptor processing affects caveolar localisation and mitogenic signalling. Distinct subcellular localisations of ET(B) receptor constructs and epidermal growth factor (EGF) receptor ligands were analysed performing detergent-free caveolae preparations and total internal reflection fluorescence microscopy. ET(B) receptor-induced transactivation of the EGF receptor and its downstream signalling was investigated performing shedding assays and ERK1/2 phosphorylation analyses. In COS7 cells, the N-terminally truncated but not the full-length or glycosylation-deficient ET(B) receptor localised to caveolae. In caveolae-free HEK293 cells, only ET(B) receptor constructs fused to caveolin-2 localised to membrane microdomains. A caveolar accumulation of the ET(B) receptor disfavoured EGF receptor ligand shedding. Nonetheless, the activation of ERK1/2 was efficient and long-lasting. In HEK293 cells, the shedding activity was also impaired by N-terminal truncation. The subsequent ERK1/2 phosphorylation was long-lasting only for the full-length ET(B) receptor. We conclude that the ET(B) receptor localisation might depend on the presence of caveolae within the cell investigated. The data further suggest that caveolar enrichment of ET(B) receptors does not facilitate the release of EGF receptor ligands. However, independent of their localisation, ET(B) receptors are able to induce an ERK1/2 phosphorylation.
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Affiliation(s)
- Solveig Grossmann
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Unversität Leipzig, Härtelstrasse 16-18, Leipzig, Germany
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Parker MS, Sah R, Balasubramaniam A, Sallee FR, Sweatman T, Park EA, Parker SL. Dimers of the neuropeptide Y (NPY) Y2 receptor show asymmetry in agonist affinity and association with G proteins. J Recept Signal Transduct Res 2009; 28:437-51. [PMID: 18946765 DOI: 10.1080/10799890802447423] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In conditions precluding activation of G proteins, the binding of agonists to dimers of the neuropeptide Y (NPY) Y2 receptor shows two components of similar size, but differing in affinity. The dimers of all NPY receptors are solubilized as approximately 180-kDa complexes containing one G protein alpha beta gamma trimer. These heteropentamers are stable to excess agonists, chelators, and alkylators. However, dispersion in the weak surfactant cholate releases approximately 300-kDa complexes. These findings indicate that both protomers in the Y2 dimer are associated with G protein heterotrimers, but the extent of interaction depends on affinity for the agonist peptide. The G protein in contact with the first-liganded, higher-affinity protomer should have a stronger interaction with the receptor and a larger probability of activation.
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Affiliation(s)
- M S Parker
- Department of Molecular Cell Sciences, University of Memphis, Memphis, Tennessee, USA.
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35
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Lättig J, Oksche A, Beyermann M, Rosenthal W, Krause G. Structural determinants for selective recognition of peptide ligands for endothelin receptor subtypes ETA
and ETB. J Pept Sci 2009; 15:479-91. [DOI: 10.1002/psc.1146] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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36
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Schmidt A, Wiesner B, Weißhart K, Schulz K, Furkert J, Lamprecht B, Rosenthal W, Schülein R. Use of Kaede Fusions to Visualize Recycling of G Protein-Coupled Receptors. Traffic 2008; 10:2-15. [DOI: 10.1111/j.1600-0854.2008.00843.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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37
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Nordström R, Andersson H. Amino-Terminal Processing of the Human Cannabinoid Receptor 1. J Recept Signal Transduct Res 2008; 26:259-67. [PMID: 16818376 DOI: 10.1080/10799890600758252] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The human cannabinoid receptor 1 (CB1), a G protein-coupled receptor (GPCR), translocates its long amino-terminal (N-terminal) domain across the endoplasmic reticulum (ER) membrane in a C-to-N terminal direction. Using the Semliki Forest virus (SFV) expression system, CB1 was expressed in baby hamster kidney (BHK) cells. It was found that a large fraction of the CB1 molecules were N-terminally truncated prior to ER translocation. Truncation was fast and independent of the proteasome. It is concluded that the truncation process might be a way to create a novel type of CB1.
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Affiliation(s)
- Rickard Nordström
- Department of Biosciences and Nutrition at Novum, Karolinska Institute, Huddinge, Sweden
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Estes A, Wong Y, Parker M, Sallee F, Balasubramaniam A, Parker S. Neuropeptide Y (NPY) Y2 receptors of rabbit kidney cortex are largely dimeric. ACTA ACUST UNITED AC 2008; 150:88-94. [DOI: 10.1016/j.regpep.2008.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 04/28/2008] [Accepted: 06/01/2008] [Indexed: 10/22/2022]
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Ashok A, Hegde RS. Retrotranslocation of prion proteins from the endoplasmic reticulum by preventing GPI signal transamidation. Mol Biol Cell 2008; 19:3463-76. [PMID: 18508914 DOI: 10.1091/mbc.e08-01-0087] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Neurodegeneration in diseases caused by altered metabolism of mammalian prion protein (PrP) can be averted by reducing PrP expression. To identify novel pathways for PrP down-regulation, we analyzed cells that had adapted to the negative selection pressure of stable overexpression of a disease-causing PrP mutant. A mutant cell line was isolated that selectively and quantitatively routes wild-type and various mutant PrPs for ER retrotranslocation and proteasomal degradation. Biochemical analyses of the mutant cells revealed that a defect in glycosylphosphatidylinositol (GPI) anchor synthesis leads to an unprocessed GPI-anchoring signal sequence that directs both ER retention and efficient retrotranslocation of PrP. An unprocessed GPI signal was sufficient to impart ER retention, but not retrotranslocation, to a heterologous protein, revealing an unexpected role for the mature domain in the metabolism of misprocessed GPI-anchored proteins. Our results provide new insights into the quality control pathways for unprocessed GPI-anchored proteins and identify transamidation of the GPI signal sequence as a step in PrP biosynthesis that is absolutely required for its surface expression. As each GPI signal sequence is unique, these results also identify signal recognition by the GPI-transamidase as a potential step for selective small molecule perturbation of PrP expression.
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Affiliation(s)
- Aarthi Ashok
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Agonist-specific down regulation of mu-opioid receptors: Different cellular pathways are activated by different opioid agonists. Life Sci 2008; 82:831-9. [PMID: 18358497 DOI: 10.1016/j.lfs.2008.01.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 01/17/2008] [Accepted: 01/23/2008] [Indexed: 11/21/2022]
Abstract
Opioid agonists are known to induce down regulation of opioid receptors through the classical pathway that involves phosphorylation, clathrin-dependent endocytosis and lysosomal/endosomal degradation of the internalized receptors. As expected, exposure of mu-opioid receptor (MOR)-transfected HEK-293 cells to either DAMGO (a specific mu-opioid agonist) or etorphine (a wide spectrum opioid agonist) resulted in down regulation of the receptors that was blocked by the kinase inhibitor staurosporine, by hypertonic sucrose and by the lysosomal and proteasomal inhibitors chloroquine and lactacystin. High concentration of etorphine, but not of DAMGO, induced an additional process of down regulation that was resistant to staurosporine, to hypertonic sucrose and to chloroquine-lactacystin. Etorphine, but not DAMGO, also induced down regulation of mu-opioid receptors in isolated membranes of HEK cells. This membrane-delimited down regulation was blocked by selective inhibitors of protease enzymes, suggesting the involvement of membranous serine- and amino-peptidases. This membranous down regulation of opioid receptors was dependent on the concentration of etorphine and was blocked by the opioid antagonist naloxone. Etorphine induced similar down regulation in membranes of HEK-293 cells transfected with delta-opioid receptors (DOR) as well in membranes of cells that endogenously express opioid receptors. This agonist-specific membrane-delimited regulatory process appears to be physiologically relevant and should be taken into account when studying long term effects of opioid drugs.
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Plant TD, Zöllner C, Kepura F, Mousa SS, Eichhorst J, Schaefer M, Furkert J, Stein C, Oksche A. Endothelin potentiates TRPV1 via ETA receptor-mediated activation of protein kinase C. Mol Pain 2007; 3:35. [PMID: 18001466 PMCID: PMC2206006 DOI: 10.1186/1744-8069-3-35] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Accepted: 11/14/2007] [Indexed: 01/26/2023] Open
Abstract
Background Endothelin-1 (ET-1) both stimulates nociceptors and sensitizes them to noxious stimuli, an effect probably mediated by the ETA receptor (ETAR) expressed in sensory neurons. The cellular mechanisms of this ET-1-mediated effect are only poorly understood. TRPV1, the heat-, pH- and capsaicin-sensitive cation channel already known to be modulated by a number of cellular mediators released in response to noxious stimuli and during inflammation, is a potential target for the action of ET-1. Results We studied the effects of ET-1 on TRPV1 in sensory neurons from the dorsal root ganglion (DRG) and in HEK293 cells coexpressing TRPV1 and the ETAR. Specific 125I-ET-1 binding sites (817 ± 92 fmol/mg) were detected in membrane preparations of DRG with an ETAR/ETBR ratio of 60:40. In an immunofluorescence analysis, coexpression of TRPV1 and the ETAR was found in a subpopulation of primary sensory neurons. ET-1 strongly potentiated capsaicin-induced TRPV1 currents in some neurons, and in HEK293 cells co-expressing TRPV1 and the ETAR. Weaker potentiation was observed in HEK293 cells coexpressing TRPV1 and the ETBR. ETAR activation also increased responses to low pH and heat. In HEK293 cells, strong potentiation of TRPV1 like that induced by ET-1 via the ETAR could be induced by PKC activation, but not with activators of the adenylyl cyclase or the PKA pathway. Furthermore, inhibition of PKC with bisindolylmaleimide X (BIM X) or mutation of the PKC phosphorylation site S800 completely prevented ETAR-mediated potentiation. Conclusion We conclude that ET-1 potentiates TRPV1 by a PKC-dependent mechanism and that this could play a major role in the algogenic and hyperalgesic effects of ET-1 described in previous studies.
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Affiliation(s)
- Tim D Plant
- Institut für Pharmakologie und Toxikologie, FB-Medizin, Philipps-Universität Marburg, Karl-von-Frisch-Str, 1, 35032 Marburg, Germany.
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Beyermann M, Heinrich N, Fechner K, Furkert J, Zhang W, Kraetke O, Bienert M, Berger H. Achieving signalling selectivity of ligands for the corticotropin-releasing factor type 1 receptor by modifying the agonist's signalling domain. Br J Pharmacol 2007; 151:851-9. [PMID: 17533422 PMCID: PMC2014118 DOI: 10.1038/sj.bjp.0707293] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Most of the pharmaceuticals target G-protein-coupled receptors (GPCRs) which can generally activate different signalling events. The aim of this study was to achieve functional selectivity of corticotropin-releasing factor receptor type 1 (CRF(1)) ligands. EXPERIMENTAL APPROACH We systematically substituted urocortin, a natural peptide agonist of CRF(1), with bulky amino acids (benzoyl-phenylalanine, naphthylalanine) and determined the effect of the analogues on coupling of CRF(1) to Gs- and Gi-protein in human embryonic kidney cells, using receptor binding, [(35)S]-GTPgammaS binding stimulation, and cAMP accumulation assays. KEY RESULTS Native ligands stimulated Gs and Gi activation through CRF(1), resulting in stimulation and then inhibition of cAMP accumulation. Single replacements in urocortin at positions 6-15 led, dependent on the position and nature of the substituent, to ligands that conserved Gs activity, but were devoid of Gi activity, only stimulating cAMP accumulation, and competitively antagonized the Gi activation by sauvagine. In contrast, analogues with substitutions outside this sequence non-selectively activated Gs and Gi, as urocortin did. CONCLUSIONS AND IMPLICATIONS Modifications in a specific region, which we have called the signalling domain, in the polypeptide agonist urocortin resulted in analogues that behaved as agonists and, at the same time, antagonists for the activation of different G-proteins by CRF(1). This finding implies significant differences between active conformations of the receptor when coupled to different G-proteins. A similar structural encoding of signalling information in other polypeptide hormone receptor ligands would result in a general concept for the development of signalling-selective drug candidates.
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Affiliation(s)
- M Beyermann
- Leibniz-Institut für Molekulare Pharmakologie im FV Berlin e.V., Berlin, Germany.
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43
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Stefan E, Wiesner B, Baillie GS, Mollajew R, Henn V, Lorenz D, Furkert J, Santamaria K, Nedvetsky P, Hundsrucker C, Beyermann M, Krause E, Pohl P, Gall I, MacIntyre AN, Bachmann S, Houslay MD, Rosenthal W, Klussmann E. Compartmentalization of cAMP-dependent signaling by phosphodiesterase-4D is involved in the regulation of vasopressin-mediated water reabsorption in renal principal cells. J Am Soc Nephrol 2006; 18:199-212. [PMID: 17135396 DOI: 10.1681/asn.2006020132] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The cAMP/protein kinase A (PKA)-dependent insertion of water channel aquaporin-2 (AQP2)-bearing vesicles into the plasma membrane in renal collecting duct principal cells (AQP2 shuttle) constitutes the molecular basis of arginine vasopressin (AVP)-regulated water reabsorption. cAMP/PKA signaling systems are compartmentalized by A kinase anchoring proteins (AKAP) that tether PKA to subcellular sites and by phosphodiesterases (PDE) that terminate PKA signaling through hydrolysis of localized cAMP. In primary cultured principal cells, AVP causes focal activation of PKA. PKA and cAMP-specific phosphodiesterase-4D (PDE4D) are located on AQP2-bearing vesicles. The selective PDE4 inhibitor rolipram increases AKAP-tethered PKA activity on AQP2-bearing vesicles and enhances the AQP2 shuttle and thereby the osmotic water permeability. AKAP18delta, which is located on AQP2-bearing vesicles, directly interacts with PDE4D and PKA. In response to AVP, PDE4D and AQP2 translocate to the plasma membrane. Here PDE4D is activated through PKA phosphorylation and reduces the osmotic water permeability. Taken together, a novel, compartmentalized, and physiologically relevant cAMP-dependent signal transduction module on AQP2-bearing vesicles, comprising anchored PDE4D, AKAP18delta, and PKA, has been identified.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors
- 3',5'-Cyclic-AMP Phosphodiesterases/genetics
- 3',5'-Cyclic-AMP Phosphodiesterases/metabolism
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Amino Acid Sequence
- Animals
- Aquaporin 2/metabolism
- Arginine Vasopressin/metabolism
- Arginine Vasopressin/pharmacology
- Cells, Cultured
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/genetics
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 3
- Cyclic Nucleotide Phosphodiesterases, Type 4
- Humans
- Kidney Tubules, Collecting/cytology
- Kidney Tubules, Collecting/drug effects
- Kidney Tubules, Collecting/metabolism
- Models, Biological
- Molecular Sequence Data
- Phosphodiesterase Inhibitors/pharmacology
- Rats
- Rats, Sprague-Dawley
- Recombinant Proteins/antagonists & inhibitors
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Rolipram/pharmacology
- Sequence Homology, Amino Acid
- Signal Transduction
- Water/metabolism
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Affiliation(s)
- Eduard Stefan
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
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Cook JL, Mills SJ, Naquin RT, Alam J, Re RN. Cleavage of the angiotensin II type 1 receptor and nuclear accumulation of the cytoplasmic carboxy-terminal fragment. Am J Physiol Cell Physiol 2006; 292:C1313-22. [PMID: 17122414 DOI: 10.1152/ajpcell.00454.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Our published studies show that the distribution of the ANG II type 1 (AT(1)) receptor (AT(1)R), expressed as a enhanced yellow fluorescent fusion (YFP) protein (AT(1)R/EYFP), is altered upon cellular treatment with ANG II or coexpression with intracellular ANG II. AT(1)R accumulates in nuclei of cells only in the presence of ANG II. Several transmembrane receptors are known to accumulate in nuclei, some as holoreceptors and others as cleaved receptor products. The present study was designed to determine whether the AT(1)R is cleaved before nuclear transport. A plasmid encoding a rat AT(1)R labeled at the amino terminus with enhanced cyan fluorescent protein (CFP) and at the carboxy terminus with EYFP was employed. Image analyses of this protein in COS-7 cells, CCF-STTG1 glial cells, and A10 vascular smooth muscle cells show the two fluorescent moieties to be largely spatially colocalized in untreated cells. ANG II treatment, however, leads to a separation of the fluorescent moieties with yellow fluorescence accumulating in more than 30% of cellular nuclei. Immunoblot analyses of extracts and conditioned media from transfected cells indicate that the CFP domain fused to the extracellular amino-terminal AT(1)R domain is cleaved from the membrane and that the YFP domain, together with the intracellular cytoplasmic carboxy terminus of the AT(1)R, is also cleaved from the membrane-bound receptor. The carboxy terminus of the AT(1)R is essential for cleavage; cleavage does not occur in protein deleted with respect to this region. Overexpressed native AT(1)R (nonfusion) is also cleaved; the intracellular 6-kDa cytoplasmic domain product accumulates to a significantly higher level with ANG II treatment.
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Affiliation(s)
- Julia L Cook
- Ochsner Clinic Foundation, Ochsner Health System, 1516 Jefferson Hwy., New Orleans, LA 70121, USA.
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45
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Dong C, Wu G. Regulation of anterograde transport of alpha2-adrenergic receptors by the N termini at multiple intracellular compartments. J Biol Chem 2006; 281:38543-54. [PMID: 17038316 PMCID: PMC2648813 DOI: 10.1074/jbc.m605734200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The studies on the intrinsic structural determinants for export trafficking of G protein-coupled receptors (GPCRs) have been mainly focused on the C termini of the receptors. In this report we determined the role of the extracellular N termini of alpha(2)-adrenergic receptors (alpha(2)-ARs) in the anterograde transport from the endoplasmic reticulum (ER) through the Golgi to the cell surface. The N-terminal-truncated alpha(2B)-AR mutant is completely unable to target to the cell surface. A single Met-6 residue is essential for the export of alpha(2B)-AR from the ER, likely through modulating correct alpha(2B)-AR folding in the ER. The Tyr-Ser motif, highly conserved in the membrane-proximal N termini of all alpha(2)-AR subtypes, is required for the exit of alpha(2A)-AR and alpha(2B)-AR from the Golgi apparatus, thus representing a novel Tyr-based motif modulating GPCR transport at the Golgi level. These data provide the first evidence indicating an essential role of the N termini of GPCRs in the export from distinct intracellular compartments along the secretory pathway.
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Affiliation(s)
- Chunmin Dong
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA 70112, USA
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Dong C, Filipeanu CM, Duvernay MT, Wu G. Regulation of G protein-coupled receptor export trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:853-70. [PMID: 17074298 PMCID: PMC1885203 DOI: 10.1016/j.bbamem.2006.09.008] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 09/14/2006] [Accepted: 09/18/2006] [Indexed: 12/26/2022]
Abstract
G protein-coupled receptors (GPCRs) constitute a superfamily of cell-surface receptors which share a common topology of seven transmembrane domains and modulate a variety of cell functions through coupling to heterotrimeric G proteins by responding to a vast array of stimuli. The magnitude of cellular response elicited by a given signal is dictated by the level of GPCR expression at the plasma membrane, which is the balance of elaborately regulated endocytic and exocytic trafficking. This review will cover recent advances in understanding the molecular mechanism underlying anterograde transport of the newly synthesized GPCRs from the endoplasmic reticulum (ER) through the Golgi to the plasma membrane. We will focus on recently identified motifs involved in GPCR exit from the ER and the Golgi, GPCR folding in the ER and the rescue of misfolded receptors from within, GPCR-interacting proteins that modulate receptor cell-surface targeting, pathways that mediate GPCR traffic, and the functional role of export in controlling GPCR signaling.
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Affiliation(s)
| | | | | | - Guangyu Wu
- * Corresponding author. Tel: +1 504 568 2236; Fax: +1 504 568 2361. E-mail address: (G. Wu)
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Grantcharova E, Reusch HP, Grossmann S, Eichhorst J, Krell HW, Beyermann M, Rosenthal W, Oksche A. N-Terminal Proteolysis of the Endothelin B Receptor Abolishes Its Ability to Induce EGF Receptor Transactivation and Contractile Protein Expression in Vascular Smooth Muscle Cells. Arterioscler Thromb Vasc Biol 2006; 26:1288-96. [PMID: 16601236 DOI: 10.1161/01.atv.0000220377.51354.30] [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: 11/16/2022]
Abstract
OBJECTIVE The extracellular N terminus of the endothelin B (ETB) receptor is cleaved by a metalloprotease in an agonist-dependent manner, but the physiological role of this N-terminal proteolysis is not known. In this study, we aimed to determine the functional role of the ETB receptor and of its N-terminal cleavage in vascular smooth muscle cells (VSMCs). METHODS AND RESULTS VSMCs expressing either the full-length ETB receptor or an N-terminally truncated ETB receptor (corresponding to the N-terminally cleaved receptor) were analyzed for ligand-induced mitogen-activated protein kinase activation and expression of contractile proteins. In VSMCs expressing the full-length ETB receptor, IRL1620 (an ETB-selective agonist) induced a biphasic extracellular signal-regulated kinase 1/2 (ERK1/2) activation and increased expression of contractile proteins (smooth muscle myosin-1 [SM-1]/SM-2, SM22alpha, and alpha-actin). Interestingly, the second phase of ERK1/2 activation required metalloprotease activity, epidermal growth factor (EGF) receptor transactivation, and predominantly activation of Gi proteins. In contrast, in VSMCs expressing N-terminally truncated ETB receptors, IRL1620 did not elicit EGF transactivation and failed to increase contractile protein expression. CONCLUSIONS This study is the first to show that stimulation of full-length ETB receptors promotes expression of contractile proteins and may thus participate in the differentiation of VSMCs.
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MESH Headings
- Animals
- Cells, Cultured
- Contractile Proteins/metabolism
- Endothelins/pharmacology
- Enzyme Activation/drug effects
- ErbB Receptors/genetics
- Extracellular Signal-Regulated MAP Kinases/metabolism
- GTP-Binding Protein alpha Subunits, Gi-Go/physiology
- Green Fluorescent Proteins/genetics
- Humans
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Mutation
- Myocytes, Smooth Muscle/metabolism
- Peptide Fragments/metabolism
- Peptide Fragments/pharmacology
- Peptide Hydrolases/metabolism
- Rats
- Receptor, Endothelin B/agonists
- Receptor, Endothelin B/chemistry
- Receptor, Endothelin B/genetics
- Receptor, Endothelin B/metabolism
- Recombinant Fusion Proteins/drug effects
- Recombinant Fusion Proteins/metabolism
- Recombinant Fusion Proteins/pharmacology
- Transcriptional Activation
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48
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Sah R, Balasubramaniam A, Parker MS, Sallee F, Parker SL. Neuropeptide Y as a partial agonist of the Y1 receptor. Eur J Pharmacol 2005; 525:60-8. [PMID: 16293244 DOI: 10.1016/j.ejphar.2005.10.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 09/12/2005] [Accepted: 10/07/2005] [Indexed: 12/01/2022]
Abstract
In absence of receptor cycling, human/rat neuropeptide Y was found to persistently occupy the guinea pig neuropeptide Y Y1 receptors expressed on the surface of Chinese hamster ovary (CHO) cells (IC50 approximately 8 nM); a lasting occupancy was also evident with active receptor cycling. A similar blockade was obtained with the human neuropeptide Y Y1 receptor (in CHO or SK-N-MC cells). Peptidic antagonists GR238118 (1229U91) and VD-11 blocked the Y1 receptor in the same molarity range. A neuropeptide Y-related Y1 agonist, (Leu31Pro34) human neuropeptide Y, also strongly adhered to the Y1 site. Similar blockade-like occupancy by neuropeptide Y was found with particulates from Y1-expressing CHO cells, and with native neuropeptide Y Y1 receptors of rat synaptosomes. Peptide YY and a related Y1-selective agonist, (Leu31Pro34) human peptide YY, showed a much less stable binding to the neuropeptide Y Y1 receptor with either the intact cells or particulates. The Y1 binding of neuropeptide Y was also less sensitive to chaotropic agents and guanine nucleotides than the binding of peptide YY, indicating a larger stability for association of neuropeptide Y with the receptor. Inhibition of forskolin-stimulated adenylyl cyclase showed a distinctly attenuating agonism for neuropeptide Y, with an activity similar to peptide YY below 1 nM, but considerably lower above 3 nM of the peptides. This activity was largely exerted via pertussis toxin-sensitive G-proteins of Y1-CHO cells. Our findings indicate that signaling by neuropeptide Y via its Y1 receptor could be self-restricting at higher levels of the peptide, in relation to a strong association of the agonist with the Y1 binding site.
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Affiliation(s)
- Renu Sah
- Department of Psychiatry, University of Cincinnati School of Medicine, Cincinnati, OH, USA
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Giebing G, Tölle M, Jürgensen J, Eichhorst J, Furkert J, Beyermann M, Neuschäfer-Rube F, Rosenthal W, Zidek W, van der Giet M, Oksche A. Arrestin-Independent Internalization and Recycling of the Urotensin Receptor Contribute to Long-Lasting Urotensin II–Mediated Vasoconstriction. Circ Res 2005; 97:707-15. [PMID: 16141412 DOI: 10.1161/01.res.0000184670.58688.9f] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Urotensin II (UII), which acts on the G protein-coupled urotensin (UT) receptor, elicits long-lasting vasoconstriction. The role of UT receptor internalization and intracellular trafficking in vasoconstriction has yet not been analyzed. Therefore, UII-mediated contractile responses of aortic ring preparations in wire myography and rat UT (rUT) receptor internalization and intracellular trafficking in binding and imaging analyses were compared. UII elicited a concentration-dependent vasoconstriction of rat aorta (-log EC50, mol/L:9.0+/-0.1). A second application of UII after 30 minutes elicited a reduced contraction (36+/-4% of the initial response), but when applied after 60 minutes elicited a full contraction. In internalization experiments with radioactive labeled VII ((125)I-UII), approximately 70% of rUT receptors expressed on the cell surface of human embryonic kidney 293 cells were sequestered within 30 minutes (half life [t(h)]: 5.6+/-0.2 minutes), but recycled quantitatively within 60 minutes (t(h) 31.9+/-2.6 minutes). UII-bound rUT receptors were sorted to early and recycling endosomes, as evidenced by colocalization of rUT receptors with the early endosomal antigen and the transferrin receptor. Real-time imaging with a newly developed fluorescent UII (Cy3-UII) revealed that rUT receptors recruited arrestin3 green fluorescent protein to the plasma membrane. Arrestin3 was not required for the endocytosis of the rUT receptor, however, as internalization of Cy3-UII was not altered in mouse embryonic fibroblasts lacking endogenous arrestin2/arrestin3 expression. The data demonstrate that the rUT receptor internalizes arrestin independently and recycles quantitatively. The continuous externalization of rUT receptors provides the basis for repetitive and lasting UII-mediated vasoconstriction.
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Affiliation(s)
- Günter Giebing
- Med. Klinik IV-Nephrologie, Charité, Campus Benjamin Franklin, Berlin, Germany
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Gregan B, Jürgensen J, Papsdorf G, Furkert J, Schaefer M, Beyermann M, Rosenthal W, Oksche A. Ligand-dependent Differences in the Internalization of Endothelin A and Endothelin B Receptor Heterodimers. J Biol Chem 2004; 279:27679-87. [PMID: 15075338 DOI: 10.1074/jbc.m403601200] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endothelin-1 (ET-1) is a potent vasoactive peptide that acts on endothelin A (ET(A)) and endothelin B (ET(B)) receptors. Although both receptor subtypes are co-expressed in numerous cells, little is known about their ability to form heterodimers. Here we show that both receptors were co-immunoprecipitated with an ET(B)-specific antibody using extracts from HEK293 cells stably co-expressing a fusion protein consisting of a myc-tagged ET(A) receptor and CFP (ET(A)myc.CFP) and a fusion protein consisting of an ET(B) receptor and YFP (ET(B).YFP). Co-immunoprecipitation was also observed with extracts from HEK293 cells transiently co-expressing FLAG-tagged ET(B) and myc-tagged ET(A) receptors, thereby excluding that heterodimerization is mediated by the CFP/YFP moieties. Heterodimerization was further confirmed in fluorescence resonance energy transfer (FRET) analysis of HEK293 cells transiently co-expressing ET(A)myc.CFP and ET(B).YFP receptors. FRET efficiencies were between 12 and 18% in untreated and antagonist- or ET-1-treated cells, indicating constitutive heterodimerization. Prolonged stimulation (30 min) with the ET(B) receptor-selective agonist BQ3020 decreased FRET efficiency by 50%. This decrease was not observed when internalization was inhibited by co-expression of dominant-negative K44A.dynamin I or incubation with 450 mm sucrose. Enzyme-linked immunosorbent assay and laser scanning microscopy of cell clones stably co-expressing ET(A)myc.CFP/ET(B)flag.YFP receptors revealed a slower sequestration of the ET(B)flag.YFP receptors upon stimulation with ET-1 than with BQ3020. No difference in ET-1 or BQ3020-mediated sequestration was observed with cell clones expressing ET(B)flag.YFP receptors alone. The data suggest that ET(A) and ET(B) receptors form constitutive heterodimers, which show a slower sequestration upon stimulation with ET-1 than with BQ3020. Heterodimer dissociation along the endocytic pathway only occurs upon ET(B)-selective stimulation.
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Affiliation(s)
- Bernd Gregan
- Institut für Pharmakologie, Charité Universitätsmedizin Berlin, Campus Benjamin Franklin, Thielallee 67-73, 14195 Berlin, Germany
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