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Lee J, Gonzalez-Hernandez AJ, Kristt M, Abreu N, Roßmann K, Arefin A, Marx DC, Broichhagen J, Levitz J. Distinct beta-arrestin coupling and intracellular trafficking of metabotropic glutamate receptor homo- and heterodimers. SCIENCE ADVANCES 2023; 9:eadi8076. [PMID: 38055809 PMCID: PMC10699790 DOI: 10.1126/sciadv.adi8076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 11/03/2023] [Indexed: 12/08/2023]
Abstract
The metabotropic glutamate receptors (mGluRs) are family C, dimeric G protein-coupled receptors (GPCRs), which play critical roles in synaptic transmission. Despite an increasing appreciation of the molecular diversity of this family, how distinct mGluR subtypes are regulated remains poorly understood. We reveal that different group II/III mGluR subtypes show markedly different beta-arrestin (β-arr) coupling and endocytic trafficking. While mGluR2 is resistant to internalization and mGluR3 shows transient β-arr coupling, which enables endocytosis and recycling, mGluR8 and β-arr form stable complexes, which leads to efficient lysosomal targeting and degradation. Using chimeras and mutagenesis, we pinpoint carboxyl-terminal domain regions that control β-arr coupling and trafficking, including the identification of an mGluR8 splice variant with impaired internalization. We then use a battery of high-resolution fluorescence assays to find that heterodimerization further expands the diversity of mGluR regulation. Together, this work provides insight into the relationship between GPCR/β-arr complex formation and trafficking while revealing diversity and intricacy in the regulation of mGluRs.
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Affiliation(s)
- Joon Lee
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | | | - Melanie Kristt
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - Nohely Abreu
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - Kilian Roßmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany
| | - Anisul Arefin
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - Dagan C. Marx
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | | | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Psychiatry, Weill Cornell Medicine, New York, NY 10065, USA
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2
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Pitonzo DG. Albuterol: Still first-line in rescue therapy? JAAPA 2022; 35:15-16. [PMID: 36165542 DOI: 10.1097/01.jaa.0000873824.54710.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
ABSTRACT Albuterol has been a cornerstone of asthma treatment for several decades, but evidence suggests that it may be overused at the expense of more efficacious treatment. Albuterol may not even be appropriate for sole first-line rescue medication in some patients. Inflammatory mechanisms have been shown to play a role early in the course of developing bronchospasm, suggesting that inhaled corticosteroids should be included as part of initial rescue treatment. Newer biologics target inflammatory cytokine pathways, which may be needed in patients with moderate to severe disease. Evidence-based recommendations for the management of asthma and bronchospasm are continuing to evolve.
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Affiliation(s)
- David G Pitonzo
- David G. Pitonzo is an associate professor in the PA program at High Point (N.C.) University and practices at Triad Adult and Pediatric Medicine in High Point. The author has disclosed no potential conflicts of interest, financial or otherwise
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3
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Skopál A, Kéki T, Tóth PÁ, Csóka B, Koscsó B, Németh ZH, Antonioli L, Ivessa A, Ciruela F, Virág L, Haskó G, Kókai E. Cathepsin D interacts with adenosine A 2A receptors in mouse macrophages to modulate cell surface localization and inflammatory signaling. J Biol Chem 2022; 298:101888. [PMID: 35367412 PMCID: PMC9065627 DOI: 10.1016/j.jbc.2022.101888] [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: 10/01/2021] [Revised: 03/21/2022] [Accepted: 03/23/2022] [Indexed: 11/30/2022] Open
Abstract
Adenosine A2A receptor (A2AR)–dependent signaling in macrophages plays a key role in the regulation of inflammation. However, the processes regulating A2AR targeting to the cell surface and degradation in macrophages are incompletely understood. For example, the C-terminal domain of the A2AR and proteins interacting with it are known to regulate receptor recycling, although it is unclear what role potential A2AR-interacting partners have in macrophages. Here, we aimed to identify A2AR-interacting partners in macrophages that may effect receptor trafficking and activity. To this end, we performed a yeast two-hybrid screen using the C-terminal tail of A2AR as the “bait” and a macrophage expression library as the “prey.” We found that the lysosomal protease cathepsin D (CtsD) was a robust hit. The A2AR–CtsD interaction was validated in vitro and in cellular models, including RAW 264.7 and mouse peritoneal macrophage (IPMΦ) cells. We also demonstrated that the A2AR is a substrate of CtsD and that the blockade of CtsD activity increases the density and cell surface targeting of A2AR in macrophages. Conversely, we demonstrate that A2AR activation prompts the maturation and enzymatic activity of CtsD in macrophages. In summary, we conclude that CtsD is a novel A2AR-interacting partner and thus describe molecular and functional interplay that may be crucial for adenosine-mediated macrophage regulation in inflammatory processes.
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Affiliation(s)
- Adrienn Skopál
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Kéki
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Doctoral School of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter Á Tóth
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Csóka
- Department of Anesthesiology, Columbia University, New York, New York, USA
| | - Balázs Koscsó
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Zoltán H Németh
- Department of Anesthesiology, Columbia University, New York, New York, USA; Department of Surgery, Morristown Medical Center, Morristown, New Jersey, USA
| | - Luca Antonioli
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Andreas Ivessa
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain; Neuropharmacology and Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Barcelona, Spain
| | - László Virág
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, University of Debrecen, Debrecen, Hungary
| | - György Haskó
- Department of Anesthesiology, Columbia University, New York, New York, USA.
| | - Endre Kókai
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
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4
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Song X, Akasaka H, Wang H, Abbasgholizadeh R, Shin JH, Zang F, Chen J, Logsdon CD, Maitra A, Bean AJ, Wang H. Hematopoietic progenitor kinase 1 down-regulates the oncogenic receptor tyrosine kinase AXL in pancreatic cancer. J Biol Chem 2020; 295:2348-2358. [PMID: 31959629 DOI: 10.1074/jbc.ra119.012186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/14/2020] [Indexed: 12/23/2022] Open
Abstract
The oncogenic receptor tyrosine kinase AXL is overexpressed in cancer and plays an important role in carcinomas of multiple organs. However, the mechanisms of AXL overexpression in cancer remain unclear. In this study, using HEK293T, Panc-1, and Panc-28 cells and samples of human pancreatic intraepithelial neoplasia (PanIN), along with several biochemical approaches and immunofluorescence microscopy analyses, we sought to investigate the mechanisms that regulate AXL over-expression in pancreatic ductal adenocarcinoma (PDAC). We found that AXL interacts with hematopoietic progenitor kinase 1 (HPK1) and demonstrate that HPK1 down-regulates AXL and decreases its half-life. The HPK1-mediated AXL degradation was inhibited by the endocytic pathway inhibitors leupeptin, bafilomycin A1, and monensin. HPK1 accelerated the movement of AXL from the plasma membrane to endosomes in pancreatic cancer cells treated with the AXL ligand growth arrest-specific 6 (GAS6). Moreover, HPK1 increased the binding of AXL to the Cbl proto-oncogene (c-Cbl); promoted AXL ubiquitination; decreased AXL-mediated signaling, including phospho-AKT and phospho-ERK signaling; and decreased the invasion capability of PDAC cells. Importantly, we show that AXL expression inversely correlates with HPK1 expression in human PanINs and that patients whose tumors have low HPK1 and high AXL expression levels have shorter survival than those with low AXL or high HPK1 expression (p < 0.001). Our results suggest that HPK1 is a tumor suppressor that targets AXL for degradation via the endocytic pathway. HPK1 loss of function may contribute to AXL overexpression and thereby enhance AXL-dependent downstream signaling and tumor invasion in PDAC.
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Affiliation(s)
- Xianzhou Song
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Hironari Akasaka
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Hua Wang
- Department of Gastrointestinal Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Reza Abbasgholizadeh
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Ji-Hyun Shin
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Fenglin Zang
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Jiayi Chen
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Craig D Logsdon
- Department of Cancer Biology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Anirban Maitra
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Translational Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Andrew J Bean
- Department of Neurobiology and Anatomy, University of Texas McGovern Medical School, Houston, Texas 77030
| | - Huamin Wang
- Department of Anatomical Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Translational Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030.
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5
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Montgomery MK, Bayliss J, Keenan S, Rhost S, Ting SB, Watt MJ. The role of Ap2a2 in PPARα-mediated regulation of lipolysis in adipose tissue. FASEB J 2019; 33:13267-13279. [PMID: 31533003 DOI: 10.1096/fj.201900909rr] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Adipose tissue plays a major role in the regulation of systemic metabolic homeostasis, with the AP2 adaptor complex being important in clathrin-mediated endocytosis (CME) of various cell surface receptors, including glucose transporter 4, the insulin receptor, and β-adrenergic receptors (ARs). One of the AP2 subunits, adaptor-related protein complex 2, α2 subunit (Ap2a2), has recently been identified as a peroxisome proliferator-activated receptor (PPAR)α target gene. The effects of PPARα on the AP2 adaptor complex and CME are unknown. We generated adipocyte-specific Ap2a2 knockout mice and investigated their metabolism when fed a standard chow or high-fat diet, without and with supplementation with the PPARα-agonist WY-14643 (WY). Although Ap2a2 deletion had only minor effects on glycaemic control, it led to substantial impairment in β-adrenergic activation of lipolysis, as evidenced by a loss of cAMP response, PKA activation, and glycerol/fatty acid release. These differences were related to increased cell surface localization of the β2- and β3-ARs. Lipolytic defects were accompanied by impaired WY-mediated loss of fat mass and whole-body fat oxidation. This study demonstrates a novel role for PPARα in β-adrenergic regulation of adipose tissue lipolysis and for adipose tissue in supplying adequate substrate to other peripheral tissues to accommodate the increase in systemic fatty acid oxidation that occurs upon treatment with PPARα agonists.-Montgomery, M. K., Bayliss, J., Keenan, S., Rhost, S., Ting, S. B., Watt, M. J. The role of Ap2a2 in PPARα-mediated regulation of lipolysis in adipose tissue.
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Affiliation(s)
- Magdalene K Montgomery
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Jacqueline Bayliss
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Stacey Keenan
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Sarah Rhost
- Australian Centre for Blood Diseases, The Alfred Centre, Monash University, Melbourne, Victoria, Australia
| | - Stephen B Ting
- Australian Centre for Blood Diseases, The Alfred Centre, Monash University, Melbourne, Victoria, Australia.,Department of Haematology, Box Hill Hospital (Eastern Health), Melbourne, Victoria, Australia
| | - Matthew J Watt
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, Victoria, Australia
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6
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Endothelin-converting enzyme-1 regulates glucagon-like peptide-1 receptor signalling and resensitisation. Biochem J 2019; 476:513-533. [PMID: 30626614 DOI: 10.1042/bcj20180853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 02/08/2023]
Abstract
Following nutrient ingestion, glucagon-like peptide 1 (GLP-1) is secreted from intestinal L-cells and mediates anti-diabetic effects, most notably stimulating glucose-dependent insulin release from pancreatic β-cells but also inhibiting glucagon release, promoting satiety and weight reduction and potentially enhancing or preserving β-cell mass. These effects are mediated by the GLP-1 receptor (GLP-1R), which is a therapeutic target in type 2 diabetes. Although agonism at the GLP-1R has been well studied, desensitisation and resensitisation are perhaps less well explored. An understanding of these events is important, particularly in the design and use of novel receptor ligands. Here, using either HEK293 cells expressing the recombinant human GLP-1R or the pancreatic β-cell line, INS-1E with endogenous expressesion of the GLP-1R, we demonstrate GLP-1R desensitisation and subsequent resensitisation following removal of extracellular GLP-1 7-36 amide. Resensitisation is dependent on receptor internalisation, endosomal acidification and receptor recycling. Resensitisation is also regulated by endothelin-converting enzyme-1 (ECE-1) activity, most likely through proteolysis of GLP-1 in endosomes and the facilitation of GLP-1R dephosphorylation and recycling. Inhibition of ECE-1 activity also increases GLP-1-induced activation of extracellular signal-regulated kinase and generation of cAMP, suggesting processes dependent upon the lifetime of the internalised ligand-receptor complex.
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7
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Kim D, Cho S, Woo JA, Liggett SB. A CREB-mediated increase in miRNA let-7f during prolonged β-agonist exposure: a novel mechanism of β 2-adrenergic receptor down-regulation in airway smooth muscle. FASEB J 2018; 32:3680-3688. [PMID: 29455573 DOI: 10.1096/fj.201701278r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
β2-Adrenergic receptors (β2ARs) desensitize during continuous agonist activation, which manifests clinically as tachyphylaxis. β-Agonist desensitization of β2ARs in human airway smooth muscle (HASM) cells is recognized in the treatment of asthma and may be related to poor outcomes. Rapid events in desensitization include receptor phosphorylation and internalization, but mechanisms responsible for the decrease in receptor protein after prolonged agonist exposure (down-regulation) are ill defined. The microRNA (miRNA) let-7f regulates β2AR expression by translational repression. In cultured HASM cells from nonasthmatic and asthmatic lungs, 18 h of β-agonist exposure increased let-7f by 2-3-fold, concomitant with a ∼90% decrease in β2ARs. Inhibition of let-7f attenuated this down-regulation response by ∼50%. The let-7f increase was found to be cAMP/PKA-dependent. The mechanism of the let-7f increase was found by chromatin immunoprecipitation to be from activated cAMP response element-binding protein (CREB) binding to the let-7f promoter, thereby increasing let-7f expression. Knockdown of CREB attenuated agonist-promoted β2AR down-regulation by ∼50%. Thus, β2AR down-regulation occurs as a result of not only internalized receptor degradation but also a novel cAMP/PKA/CREB-mediated increase in let-7f, which causes enhanced repression of the β2AR gene, adrenoreceptor β2 ( ADRB2) translation and represents ∼50% of the net loss of receptors observed after prolonged agonist exposure. This mechanism is apparent in asthmatic HASM cells, indicating relevance in a disease model.-Kim, D., Cho, S., Woo, J. A., Liggett, S. B. A CREB-mediated increase in miRNA let-7f during prolonged β-agonist exposure: a novel mechanism of β2-adrenergic receptor down-regulation in airway smooth muscle.
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Affiliation(s)
- Donghwa Kim
- Center for Personalized Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Soomin Cho
- Center for Personalized Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Jung A Woo
- Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, Florida, USA; and
| | - Stephen B Liggett
- Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, Florida, USA; and.,Department of Internal Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
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8
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Roux BT, Bauer CC, McNeish AJ, Ward SG, Cottrell GS. The Role of Ubiquitination and Hepatocyte Growth Factor-Regulated Tyrosine Kinase Substrate in the Degradation of the Adrenomedullin Type I Receptor. Sci Rep 2017; 7:12389. [PMID: 28959041 PMCID: PMC5620052 DOI: 10.1038/s41598-017-12585-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/06/2017] [Indexed: 01/27/2023] Open
Abstract
Calcitonin receptor-like receptor (CLR) and the receptor activity-modifying protein 2 (RAMP2) comprise a receptor for adrenomedullin (AM). Although it is known that AM induces internalization of CLR•RAMP2, little is known about the molecular mechanisms that regulate the trafficking of CLR•RAMP2. Using HEK and HMEC-1 cells, we observed that AM-induced activation of CLR•RAMP2 promoted ubiquitination of CLR. A mutant (CLRΔ9KR), lacking all intracellular lysine residues was functional and trafficked similar to the wild-type receptor, but was not ubiquitinated. Degradation of CLR•RAMP2 and CLRΔ9KR•RAMP2 was not dependent on the duration of AM stimulation or ubiquitination and occurred via a mechanism that was partially prevented by peptidase inhibitors. Degradation of CLR•RAMP2 was sensitive to overexpression of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), but not to HRS knockdown, whereas CLRΔ9KR•RAMP2 degradation was unaffected. Overexpression, but not knockdown of HRS, promoted hyperubiquitination of CLR under basal conditions. Thus, we propose a role for ubiquitin and HRS in the regulation of AM-induced degradation of CLR•RAMP2.
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Affiliation(s)
- Benoît T Roux
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Claudia C Bauer
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Alister J McNeish
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Stephen G Ward
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Graeme S Cottrell
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK.
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9
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Wan M, Zhang W, Tian Y, Xu C, Xu T, Liu J, Zhang R. Unraveling a molecular determinant for clathrin-independent internalization of the M2 muscarinic acetylcholine receptor. Sci Rep 2015; 5:11408. [PMID: 26094760 PMCID: PMC4476042 DOI: 10.1038/srep11408] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 05/22/2015] [Indexed: 12/25/2022] Open
Abstract
Endocytosis and postendocytic sorting of G-protein-coupled receptors (GPCRs) is important for the regulation of both their cell surface density and signaling profile. Unlike the mechanisms of clathrin-dependent endocytosis (CDE), the mechanisms underlying the control of GPCR signaling by clathrin-independent endocytosis (CIE) remain largely unknown. Among the muscarinic acetylcholine receptors (mAChRs), the M4 mAChR undergoes CDE and recycling, whereas the M2 mAChR is internalized through CIE and targeted to lysosomes. Here we investigated the endocytosis and postendocytic trafficking of M2 mAChR based on a comparative analysis of the third cytoplasmic domain in M2 and M4 mAChRs. For the first time, we identified that the sequence (374)KKKPPPS(380) servers as a sorting signal for the clathrin-independent internalization of M2 mAChR. Switching (374)KKKPPPS(380) to the i3 loop of the M4 mAChR shifted the receptor into lysosomes through the CIE pathway; and therefore away from CDE and recycling. We also found another previously unidentified sequence that guides CDE of the M2 mAChR, (361)VARKIVKMTKQPA(373), which is normally masked in the presence of the downstream sequence (374)KKKPPPS(380). Taken together, our data indicate that endocytosis and postendocytic sorting of GPCRs that undergo CIE could be sequence-dependent.
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Affiliation(s)
- Min Wan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Wenhua Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yangli Tian
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Chanjuan Xu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Tao Xu
- 1] Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China [2] National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jianfeng Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Rongying Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
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10
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Bowman SL, Puthenveedu MA. Postendocytic Sorting of Adrenergic and Opioid Receptors: New Mechanisms and Functions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:189-206. [PMID: 26055059 DOI: 10.1016/bs.pmbts.2015.03.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The endocytic pathway tightly regulates the activity of G protein-coupled receptors (GPCRs). Much of our understanding of this relationship between GPCR endocytic trafficking and signaling comes from studies done on catecholamine and opioid receptors. After ligand-induced endocytosis, a key sorting step in the endosome determines whether receptors are recycled back to the cell surface, leading to recovery of signaling, or are degraded in the lysosome, leading to desensitization. Recycling of GPCRs, unlike that of many other proteins, is an active process driven by specific sequences on the receptor and proteins that interact with this sequence. Recent data suggest that sequence-dependent recycling plays complex roles in regulating both the timing and location of GPCR signaling. This chapter will describe our current understanding of the mechanisms regulating GPCR sorting in the endosome and discuss emerging ideas on their role in GPCR signaling, focusing on adrenergic and opioid receptors as prototypes.
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Affiliation(s)
- Shanna L Bowman
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
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11
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Cottrell GS. Roles of proteolysis in regulation of GPCR function. Br J Pharmacol 2013; 168:576-90. [PMID: 23043558 DOI: 10.1111/j.1476-5381.2012.02234.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 09/03/2012] [Accepted: 09/24/2012] [Indexed: 12/18/2022] Open
Abstract
The enzymatic activity of peptidases must be tightly regulated to prevent uncontrolled hydrolysis of peptide bonds, which could have devastating effects on biological systems. Peptidases are often generated as inactive propeptidases, secreted with endogenous inhibitors, or they are compartmentalized. Propeptidases become active after proteolytic removal of N-terminal activation peptides by other peptidases. Some peptidases only become active towards substrates only at certain pHs, thus confining activity to specific compartments or conditions. This review discusses the different roles proteolysis plays in regulating GPCRs. At the cell-surface, certain GPCRs are regulated by the hydrolytic inactivation of bioactive peptides by membrane-anchored peptidases, which prevent signalling. Conversely, cell-surface peptidases can also generate bioactive peptides, which directly activate GPCRs. Alternatively, cell-surface peptidases activated by GPCRs, can generate bioactive peptides to cause transactivation of receptor tyrosine kinases, thereby promoting signalling. Certain peptidases can signal directly to cells, by cleaving GPCR to initiate intracellular signalling cascades. Intracellular peptidases also regulate GPCRs; lysosomal peptidases destroy GPCRs in lysosomes to permanently terminate signalling and mediate down-regulation; endosomal peptidases cleave internalized peptide agonists to regulate GPCR recycling, resensitization and signalling; and soluble intracellular peptidases also participate in GPCR function by regulating the ubiquitination state of GPCRs, thereby altering GPCR signalling and fate. Although the use of peptidase inhibitors has already brought success in the treatment of diseases such as hypertension, the discovery of new regulatory mechanisms involving proteolysis that control GPCRs may provide additional targets to modulate dysregulated GPCR signalling in disease.
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Affiliation(s)
- G S Cottrell
- Reading School of Pharmacy, University of Reading, Reading, UK.
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12
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Effects of the β-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of β2-adrenergic receptors with N-terminal polymorphisms. Cell Biol Int 2013; 36:1171-83. [PMID: 22938397 DOI: 10.1042/cbi20120134] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The β2-AR (β2-adrenergic receptor) is an important target for respiratory and CVD (cardiovascular disease) medications. Clinical studies suggest that N-terminal polymorphisms of β2-AR may act as disease modifiers. We hypothesized that polymorphisms at amino acids 16 and 27 result in differential trafficking and down-regulation of β2-AR variants following β-agonist exposure. The functional consequences of the four possible combinations of these polymorphisms in the human β2-AR (designated β2-AR-RE, β2-AR-GE, β2-AR-RQ and β2-AR-GQ) were studied using site-directed mutagenesis and recombinant expression in HEK-293 cells (human embryonic kidney cells). Ligand-binding assays demonstrated that after 24 h exposure to 1 μM isoprenaline, isoforms with Arg16 (β2-AR-RE and β2-AR-RQ) underwent increased down-regulation compared with isoforms with Gly16 (β2-AR-GE and β2-AR-GQ). Consistent with these differences in down-regulation between isoforms, prolonged isoprenaline treatment resulted in diminished cAMP response to subsequent isoprenaline challenge in β2-AR-RE relative to β2-AR-GE. Confocal microscopy revealed that the receptor isoforms had similar co-localization with the early endosomal marker EEA1 following isoprenaline treatment, suggesting that they had similar patterns of internalization. None of the isoforms exhibited significant co-localization with the recycling endosome marker Rab11 in response to isoprenaline treatment. Furthermore, we found that prolonged isoprenaline treatment led to a higher degree of co-localization of β2-AR-RE with the lysosomal marker LAMP1 (lysosome-associated membrane protein 1) compared with that of β2-AR-GE. Taken together, these results indicate that a mechanism responsible for differential responses of these receptor isoforms to the β-agonist involves differences in the efficiency with which agonist-activated receptors are trafficked to the lysosomes for degradation, or differences in degradation in the lysosomes.
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Grover A, Schmidt BF, Salter RD, Watkins SC, Waggoner AS, Bruchez MP. Genetically encoded pH sensor for tracking surface proteins through endocytosis. Angew Chem Int Ed Engl 2012; 51:4838-42. [PMID: 22461279 PMCID: PMC3538816 DOI: 10.1002/anie.201108107] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/19/2012] [Indexed: 12/20/2022]
Abstract
Traffic cam: a tandem dye prepared from a FRET acceptor and a fluorogenic donor functions as a cell surface ratiometric pH indicator, which upon internalization serves to follow protein trafficking during endocytosis. This sensor was used to analyze agonist-dependent internalization of β(2)-adrenergic receptors. It was also used as a surrogate antigen to reveal direct surface-to-endosome antigen transfer between dendritic cells (not shown).
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Affiliation(s)
- Anmol Grover
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University
| | | | - Russell D. Salter
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh (PA)
| | - Simon C. Watkins
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh (PA)
| | - Alan S. Waggoner
- Department of Biological Sciences and Molecular Biosensor and Imaging Center, Carnegie Mellon University
| | - Marcel P. Bruchez
- Department of Chemistry, Department of Biological Sciences and Molecular Biosensor and Imaging Center,
Carnegie Mellon University
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14
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Grover A, Schmidt BF, Salter RD, Watkins SC, Waggoner AS, Bruchez MP. Genetically Encoded pH Sensor for Tracking Surface Proteins through Endocytosis. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108107] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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Rosenfeld JL, Knoll BJ, Moore RH. Regulation of G-Protein-Coupled Receptor Activity by Rab GTPases. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820212398] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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16
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Cooper PR, Kurten RC, Zhang J, Nicholls DJ, Dainty IA, Panettieri RA. Formoterol and salmeterol induce a similar degree of β2-adrenoceptor tolerance in human small airways but via different mechanisms. Br J Pharmacol 2011; 163:521-32. [PMID: 21306583 DOI: 10.1111/j.1476-5381.2011.01257.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND AND PURPOSE Steroids prevent and reverse salbutamol-induced β(2)-adrenoceptor tolerance in human small airways. This study examines the effects of the long-acting β(2) agonists (LABAs) formoterol and salmeterol, and the ability of budesonide to prevent desensitization. EXPERIMENTAL APPROACH Long-acting β(2) agonists in the presence and absence of budesonide were incubated with human precision-cut lung slices containing small airways. Tolerance was deduced from measurements of reduced bronchodilator responses to isoprenaline and correlated with β(2)-adrenoceptor trafficking using a virally transduced, fluorescent-tagged receptor. The ability of the LABAs to protect airways against muscarinic-induced contraction was also assessed. KEY RESULTS Following a 12 h incubation, both formoterol and salmeterol attenuated isoprenaline-induced bronchodilatation to a similar degree and these effects were not reversible by washing. Pre-incubation with budesonide prevented the desensitization induced by formoterol, but not that induced by salmeterol. Formoterol also protected the airways from carbachol-induced bronchoconstriction to a greater extent than salmeterol. In the epithelial cells of small airways, incubation with formoterol promoted receptor internalization but this did not appear to occur following incubation with salmeterol. Budesonide inhibited the formoterol-induced reduction in plasma membrane β(2)-adrenoceptor fluorescence. CONCLUSIONS AND IMPLICATIONS Although both formoterol and salmeterol attenuate isoprenaline-induced bronchodilatation, they appear to induce β(2)-adrenoceptor tolerance via different mechanisms; formoterol, but not salmeterol, enhances receptor internalization. Budesonide protection against β(2)-adrenoceptor tolerance was correlated with the retention of receptor fluorescence on the plasma membrane, thereby suggesting a mechanism by which steroids alter β(2)-adrenoceptor function.
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Affiliation(s)
- P R Cooper
- Department of Medicine, Airway Biology Initiative, University of Pennsylvania School of Medicine, Philadelphia, USA
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17
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Shi Q, Hou Y, Yang Y, Bai G. Protective effects of glycyrrhizin against β₂-adrenergic receptor agonist-induced receptor internalization and cell apoptosis. Biol Pharm Bull 2011; 34:609-17. [PMID: 21532146 DOI: 10.1248/bpb.34.609] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It has been reported that treatment with β₂ adrenergic receptor (β₂AR) agonist bronchodilators may result in airway β₂ARs internalization and cardiac muscle cells apoptosis. This could lead to the loss of pharmacological effect of β₂AR agonists and increase adverse cardiovascular events in asthma patients receiving β₂AR agonist therapy. Glycyrrhizin, the major bioactive component of licorice root extract, has been reported to exhibit protective effect on respiratory system. Here, we investigate the effects of glycyrrhizin against β₂AR agonist salbutamol-induced receptor internalization and cell apoptosis. In our study, the live cell confocal imaging and fixed-cell enzyme-linked immunosorbent assay (ELISA) assay revealed that glycyrrhizin significantly inhibited salbutamol-induced surface β₂AR internalization. The underlying mechanisms were then identified to be that glycyrrhizin could reduce the association of β₂ARs with β-arrestins and clathrin heavy chain as well as the level of G protein-coupled receptor kinase (GRK) mediated phosphorylation of β₂ARs. The inhibition of receptor internalization by glycyrrhizin further lead to stabilization of the β₂AR mRNA and protein expression, thus amplified the transmembrane signaling via the β₂ARs. We also proved that glycyrrhizin could profoundly attenuate salbutamol-induced early cellular apoptosis by regulating the expressions of B-cell lymphoma 2 (Bcl-2) family genes. Taken together, our results suggest that glycyrrhizin exhibits protective effects against β₂AR agonist-induced receptor internalization and cell apoptosis. These findings might have practical implications for future strategies of combined application of glycyrrhizin with β₂AR receptor agonists to improve the efficacy of bronchodilators in patients with asthma and chronic obstructive pulmonary disease (COPD).
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Affiliation(s)
- Qian Shi
- College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Tianjin, China
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18
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Waite A, De Rosa MC, Brancaccio A, Blake DJ. A gain-of-glycosylation mutation associated with myoclonus-dystonia syndrome affects trafficking and processing of mouse ε-sarcoglycan in the late secretory pathway. Hum Mutat 2011; 32:1246-58. [PMID: 21796726 DOI: 10.1002/humu.21561] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 06/20/2011] [Indexed: 11/07/2022]
Abstract
Missense mutations in the SGCE gene encoding ε-sarcoglycan account for approximately 15% of SGCE-positive cases of myoclonus-dystonia syndrome (MDS) in humans. In this study, we show that while the majority of MDS-associated missense mutants modeled with a murine ε-sarcoglycan cDNA are substrates for endoplasmic reticulum-associated degradation, one mutant, M68T (analogous to human c.275T>C, p.M92T), located in the Ig-like domain of ε-sarcoglycan, results in a gain-of-glycosylation mutation producing a protein that is targeted to the plasma membrane, albeit at reduced levels compared to wild-type ε-sarcoglycan. Removal of the ectopic N-linked glycan failed to restore efficient plasma membrane targeting of M68T demonstrating that the substitution rather than the glycan was responsible for the trafficking defect of this mutant. M68T also colocalized with CD63-positive vesicles in the endosomal-lysosomal system and was found to be more susceptible to lysosomal proteolysis than wild-type ε-sarcoglycan. Finally, we demonstrate impaired ectodomain shedding of M68T, a process that occurs physiologically for ε-sarcoglycan resulting in the lysosomal trafficking of the intracellular C-terminal domain of the protein. Our findings show that functional analysis of rare missense mutations can provide a mechanistic insight into the pathogenesis of MDS and the physiological role of ε-sarcoglycan.
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Affiliation(s)
- Adrian Waite
- Department of Psychological Medicine and Neurology, MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Heath Park, Cardiff, UK
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19
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Chung LP, Waterer G, Thompson PJ. Pharmacogenetics of β2 adrenergic receptor gene polymorphisms, long-acting β-agonists and asthma. Clin Exp Allergy 2011; 41:312-26. [PMID: 21294785 DOI: 10.1111/j.1365-2222.2011.03696.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Adrenergic β2 receptor (ADRβ2) agonists are widely used in asthma. Approximately 10% of patients have severe, poorly controlled disease despite extensive use of ADRβ2 agonists. Variations in responses to ADRβ2 agonists can, in part, be attributed to genetic variation, with 49 different polymorphisms having been identified for the ADRβ2 gene. Although clear associations exist between ADRβ2 gene polymorphisms, such as +46G>A, and patient response, the importance of these polymorphisms remains controversial. Patient selection, the number of polymorphisms analysed, differences in the type/dose of ADRβ2 agonist, use of inhaled corticosteroids and population sizes have all varied. Most studies were limited to mild or moderate asthmatics using ADRβ2 agonists sparingly. It is difficult to extrapolate from these studies to individual patients who have severe asthma, use a variety of ADRβ2 agonists and do so frequently. The extent to which ADRβ2 gene polymorphisms are relevant to asthma management needs further review, both clinically and at the molecular level. In vitro studies have helped to define the functional changes induced by specific ADRβ2 gene polymorphisms, including 3'-untranslated region poly-C repeat. The resulting ADRβ2 gene haplotypes (rather than genotypes), the interactions among ADRβ2 gene haplotypes and variations in the chemistry of different agonists deserve more detailed assessment. Responses to ADRβ2 agonists depend on effective downstream signalling following ADRβ2 activation and also on receptor regulation. Studies on other regulators of ADRβ2 receptor signalling and trafficking may be equally important in understanding the functional role of ADRβ2 gene polymorphisms. The role of ADRβ2 gene polymorphisms in the pathogenesis and management of severe asthma cannot be clearly defined until more specific and targeted research studies are performed.
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Affiliation(s)
- L P Chung
- Genetics Unit, Lung Institute of Western Australia, Centre for Asthma, Allergy and Respiratory Research, Perth, WA, Australia
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20
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Bianco SDC, Vandepas L, Correa-Medina M, Gereben B, Mukherjee A, Kuohung W, Carroll R, Teles MG, Latronico AC, Kaiser UB. KISS1R intracellular trafficking and degradation: effect of the Arg386Pro disease-associated mutation. Endocrinology 2011; 152:1616-26. [PMID: 21285314 PMCID: PMC3060635 DOI: 10.1210/en.2010-0903] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The goal of this study was to investigate how the Arg386Pro mutation prolongs KiSS-1 receptor (KISS1R) responsiveness to kisspeptin, contributing to human central precocious puberty. Confocal imaging showed colocalization of wild-type (WT) KISS1R with a membrane marker, which persisted for up to 5 h of stimulation. Conversely, no colocalization with a lysosome marker was detected. Also, overnight treatment with a lysosome inhibitor did not affect WT KISS1R protein, whereas overnight treatment with a proteasome inhibitor increased protein levels by 24-fold. WT and Arg386Pro KISS1R showed time-dependent internalization upon stimulation. However, both receptors were recycled back to the membrane. The Arg386Pro mutation did not affect the relative distribution of KISS1R in membrane and internalized fractions when compared to WT KISS1R for up to 120 min of stimulation, demonstrating that this mutation does not affect KISS1R trafficking rate. Nonetheless, total Arg386Pro KISS1R was substantially increased compared with WT after 120 min of kisspeptin stimulation. This net increase was eliminated by blockade of detection of recycled receptors, demonstrating that recycled receptors account for the increased responsiveness of this mutant to kisspeptin. We therefore conclude the following: 1) WT KISS1R is degraded by proteasomes rather than lysosomes; 2) WT and Arg386Pro KISS1R are internalized upon stimulation, but most of the internalized receptors are recycled back to the membrane rather than degraded; 3) the Arg386Pro mutation does not affect the rate of KISS1R trafficking--instead, it prolongs responsiveness to kisspeptin by decreasing KISS1R degradation, resulting in the net increase on mutant receptor recycled back to the plasma membrane.
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Affiliation(s)
- Suzy D C Bianco
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
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21
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Xiao K, Shenoy SK. Beta2-adrenergic receptor lysosomal trafficking is regulated by ubiquitination of lysyl residues in two distinct receptor domains. J Biol Chem 2011; 286:12785-95. [PMID: 21330366 DOI: 10.1074/jbc.m110.203091] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Agonist stimulation of the β2-adrenergic receptors (β2ARs) leads to their ubiquitination and lysosomal degradation. Inhibition of lysosomal proteases results in the stabilization and retention of internalized full-length β2ARs in the lysosomes, whereas inhibition of proteasomal proteases stabilizes newly synthesized β2ARs in nonlysosomal compartments. Additionally, a lysine-less β2AR (0K-β2AR) that is deficient in ubiquitination and degradation is not sorted to lysosomes unlike the WT β2AR, which is sorted to lysosomes. Thus, lysosomes are the primary sites for the degradation of agonist-activated, ubiquitinated β2ARs. To identify the specific site(s) of ubiquitination required for lysosomal sorting of the β2AR, four mutants, with lysines only in one intracellular domain, namely, loop 1, loop 2, loop 3, and carboxyl tail were generated. All of these receptor mutants coupled to G proteins, recruited β-arrestin2, and internalized just as the WT β2AR. However, only loop 3 and carboxyl tail β2ARs with lysines in the third intracellular loop or in the carboxyl tail were ubiquitinated and sorted for lysosomal degradation. As a complementary approach, we performed MS-based proteomic analyses to directly identify ubiquitination sites within the β2AR. We overexpressed and purified the β2AR from HEK-293 cells with or without prior agonist exposure and subjected trypsin-cleaved β2AR to LC-MS/MS analyses. We identified ubiquitinated lysines in the third intracellular loop (Lys-263 and Lys-270) and in the carboxyl tail (Lys-348, Lys-372, and Lys-375) of the β2AR. These findings introduce a new concept that two distinct domains in the β2AR are involved in ubiquitination and lysosomal degradation, contrary to the generalization that such regulatory mechanisms occur mainly at the carboxyl tails of GPCRs and other transmembrane receptors.
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Affiliation(s)
- Kunhong Xiao
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
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22
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Awwad HO, Millman EE, Alpizar-Foster E, Moore RH, Knoll BJ. Mutating the dileucine motif of the human beta(2)-adrenoceptor reduces the high initial rate of receptor phosphorylation by GRK without affecting postendocytic sorting. Eur J Pharmacol 2010; 635:9-15. [PMID: 20193676 DOI: 10.1016/j.ejphar.2010.02.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 01/27/2010] [Accepted: 02/13/2010] [Indexed: 10/19/2022]
Abstract
The internalization of beta(2)-adrenoceptors after agonist activation results in a desensitized and phosphorylated receptor that either resensitizes by recycling to the cell surface or becomes degraded by postendocytic sorting to lysosomes. The duration and physiological effects of agonists therefore depend on beta(2)-adrenoceptor sorting, highlighting the importance of sorting signals. Dileucine motifs within other membrane proteins act as signals for endocytosis and/or postendocytic sorting, and the beta(2)-adrenoceptor has a dileucine motif within helix 8 that might play a role in efficient receptor recycling and/or downregulation. beta(2)-adrenoceptor internalization and sorting were studied in HEK293 cells stably expressing wild type or mutant dialanine L339A,L340A beta(2)-adrenoceptors. The mutant beta(2)-adrenoceptors showed a significantly lower initial rate of phosphorylation at the prominent G-protein coupled receptor kinase (GRK) sites Ser355 and 356 compared to wild type beta(2)-adrenoceptors. Furthermore, the agonist-induced endocytic rate constant for L339A,L340A beta(2)-adrenoceptors was reduced to approximately 25% that of wild type beta(2)-adrenoceptors, which resulted in a similar reduction in agonist-induced downregulation. Internalized L339A,L340A beta(2)-adrenoceptors recycled to the surface with a rate and extent similar to that of wild type beta(2)-adrenoceptors. Therefore, although the role of L339,L340 in beta(2)-adrenoceptor recycling or postendocytic sorting seems minimal, we conclude that L339,L340 is required for the initial high rate of phosphorylation by G-protein coupled receptor kinases at Ser355,356, which in turn is required for efficient beta(2)-adrenoceptors endocytosis.
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Affiliation(s)
- Hibah O Awwad
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204, USA
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23
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Rab11 regulates the recycling of the beta2-adrenergic receptor through a direct interaction. Biochem J 2009; 418:163-72. [PMID: 18983266 DOI: 10.1042/bj20080867] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The beta2ARs (beta(2)-adrenergic receptors) undergo ligand-induced internalization into early endosomes, but then are rapidly and efficiently recycled back to the plasma membrane, restoring the numbers of functional cell-surface receptors. Gathering evidence suggests that, during prolonged exposure to agonist, some beta2ARs also utilize a slow recycling pathway through the perinuclear recycling endosomal compartment regulated by the small GTPase Rab11. In the present study, we demonstrate by co-immunoprecipitation studies that there is a beta2AR-Rab11 association in HEK-293 cells (human embryonic kidney cells). We show using purified His(6)-tagged Rab11 protein and beta2AR intracellular domains fused to GST (glutathione transferase) that Rab11 interacts directly with the C-terminal tail of beta2AR, but not with the other intracellular domains of the receptor. Pull-down and immunoprecipitation assays revealed that the beta2AR interacts preferentially with the GDP-bound form of Rab11. Arg(333) and Lys(348) in the C-terminal tail of the beta2AR were identified as crucial determinants for Rab11 binding. A beta2AR construct with these two residues mutated to alanine, beta2AR RK/AA (R333A/K348A), was generated. Analysis of cell-surface receptors by ELISA revealed that the recycling of beta2AR RK/AA was drastically reduced when compared with wild-type beta2AR after agonist washout, following prolonged receptor stimulation. Confocal microscopy demonstrated that the beta2AR RK/AA mutant failed to co-localize with Rab11 and recycle to the plasma membrane, in contrast with the wild-type receptor. To our knowledge, the present study is the first report of a direct interaction between the beta2AR and a Rab GTPase, which is required for the accurate intracellular trafficking of the receptor.
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Liang W, Hoang Q, Clark RB, Fishman PH. Accelerated dephosphorylation of the beta2-adrenergic receptor by mutation of the C-terminal lysines: effects on ubiquitination, intracellular trafficking, and degradation. Biochemistry 2008; 47:11750-62. [PMID: 18841999 DOI: 10.1021/bi800219q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Agonist-mediated ubiquitination regulates some G protein-coupled receptors by targeting them to lysosomes for degradation. Phosphorylation also regulates receptor endocytosis and trafficking to lysosomes. To explore the roles of the two post-translational modifications, we mutated the three C-terminal lysines to arginines in the human beta 2-adrenergic receptor (beta 2AR) (K348/372/375R). The level of agonist-mediated ubiquitination of the mutant (3K/R) was greatly reduced compared to that of wild-type (WT) beta 2AR in whole cells and in cell-free assays. Downregulation of 3K/R also was attenuated compared to that of the WT, whereas internalization and recycling were more similar. During endocytosis, WT and 3K/R appeared in different vesicles and WT, but not 3K/R, was transported to lysosomes. Both were rapidly phosphorylated in agonist-stimulated cells, but upon agonist removal, the rate of dephosphorylation of 3K/R initially was approximately 5 times faster than that of WT. The increased rate also was observed in a cell-free, soluble assay and, thus, was not due to differences in receptor trafficking. Okadaic acid, a potent phosphatase inhibitor, reduced the level of dephosphorylation and increased the levels of lysosomal targeting and degradation of 3K/R. The reduced level of ubiquitination and rapid dephosphorylation of 3K/R appear to prevent it from being sorted to lysosomes in contrast to the phosphorylated and ubiquitinated WT beta 2AR. Our findings indicate that both phosphorylation and ubiquitination are involved in the intracellular sorting of beta 2AR between pathways of recycling to the plasma membrane and degradation in lysosomes, and that the rate of dephosphorylation may be another mechanism of regulating the sorting.
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Affiliation(s)
- Wei Liang
- Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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25
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Manson ME, Corey DA, White NM, Kelley TJ. cAMP-mediated regulation of cholesterol accumulation in cystic fibrosis and Niemann-Pick type C cells. Am J Physiol Lung Cell Mol Physiol 2008; 295:L809-19. [PMID: 18790990 DOI: 10.1152/ajplung.90402.2008] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The goal of this study was to identify a mechanism regulating cholesterol accumulation in cystic fibrosis (CF) cells. Both CFTR activation and expression are regulated by the cAMP pathway, and it is hypothesized that a feedback response involving this pathway may be involved in the phenotype of cholesterol accumulation. To examine the role of the cAMP pathway in cholesterol accumulation, we treated two CF model cell lines with the Rp diastereomer of adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS) and visualized by filipin staining. Rp-cAMPS treatment eliminated cholesterol accumulation in CF cells, whereas 8-bromo-cAMP treatment led to cholesterol accumulation in wild-type cells. To confirm these findings in an independent model system, we also examined the role of cAMP in modulating cholesterol accumulation in Niemann-Pick type C (NPC) fibroblasts. Expression of the protein related to NPC, NPC1, is also directly regulated by cAMP; therefore, it is postulated that NPC cells exhibit the same cAMP-mediated control of cholesterol accumulation. Cholesterol accumulation in NPC cells also was reduced by the presence of Rp-cAMPS. Expression of beta-arrestin-2 (betaarr2), a marker of cellular response to cAMP signaling, was significantly elevated in CF model cells, Cftr(-/-) MNE, primary tissue obtained by nasal scrapes from CF subjects, and in NPC fibroblasts compared with respective controls.
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Affiliation(s)
- Mary E Manson
- Department of Pediatrics, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4948, USA
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Krilov L, Nguyen A, Miyazaki T, Unson CG, Bouscarel B. Glucagon receptor recycling: role of carboxyl terminus, beta-arrestins, and cytoskeleton. Am J Physiol Cell Physiol 2008; 295:C1230-7. [PMID: 18787074 DOI: 10.1152/ajpcell.00240.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Glucagon receptor (GR) activity and expression are altered in several diseases, including Type 2 diabetes. Previously, we investigated the mechanism of GR desensitization and internalization. The present study focused on the fate of internalized GR. Using both hamster hepatocytes and human embryonic kidney (HEK)-293 cells, we showed that internalized GR recycled to the plasma membrane within 30-60 min following stimulation of the cells with 100 nM glucagon. In HEK-293 cells and during recycling, GR colocalized with Rab4, Rab11, beta-arrestin1, beta-arrestin2, and actin filaments, in the cytosolic and/or perinuclear domains. Glucagon treatment triggered redistribution of actin filaments from the plasma membrane to the cytosol. GR coimmunoprecipitated with beta-actin in both hepatocytes and HEK-293 cells. Downregulation of beta-arrestin1 and beta-arrestin2 or disruption of the cytoskeleton inhibited recycling, but not internalization of GR. Deletion of the GR carboxyl-terminal 70 amino acids abolished internalization of GR in response to glucagon while deletion of the last 40 amino acids only did not affect GR internalization and recycling. After exposure of the cells to either high concentrations or prolonged duration of glucagon, GR colocalized with lysosomes. GR degradation was inhibited by lysosomal, but not proteosomal, inhibitors. In conclusion, GR recycles through Rab4- and Rab11- positive vesicles. The actin cytoskeleton, beta-arrestin1, beta-arrestin2, and the receptor's carboxyl terminus are involved in recycling. Prolonged stimulation with glucagon targets GR for degradation in lysosomes. Therefore, the present study provides a better understanding of the GR recycling mechanism, which could become useful in the treatment of certain diseases, including diabetes.
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Affiliation(s)
- Lada Krilov
- Gastroenterology Research Laboratory. Digestive Diseases Center, Dept. of Biochemistry and Molecular Biology, George Washington Univ., 2300 Eye St. NW, Washington, DC 20037, USA
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Millman EE, Zhang H, Zhang H, Godines V, Bean AJ, Knoll BJ, Moore RH. Rapid recycling of beta-adrenergic receptors is dependent on the actin cytoskeleton and myosin Vb. Traffic 2008; 9:1958-71. [PMID: 18785920 DOI: 10.1111/j.1600-0854.2008.00813.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
For the beta(2)-adrenergic receptor (beta(2)AR), published evidence suggests that an intact actin cytoskeleton is required for the endocytosis of receptors and their proper sorting to the rapid recycling pathway. We have characterized the role of the actin cytoskeleton in the regulation of beta(2)AR trafficking in human embryonic kidney 293 (HEK293) cells using two distinct actin filament disrupting compounds, cytochalasin D and latrunculin B (LB). In cells pretreated with either drug, beta(2)AR internalization into transferrin-positive vesicles was not altered but both agents significantly decreased the rate at which beta(2)ARs recycled to the cell surface. In LB-treated cells, nonrecycled beta(2)ARs were localized to early embryonic antigen 1-positive endosomes and also accumulated in the recycling endosome (RE), but only a small fraction of receptors localized to LAMP-positive late endosomes and lysosomes. Treatment with LB also markedly enhanced the inhibitory effect of rab11 overexpression on receptor recycling. Dissociating receptors from actin by expression of the myosin Vb tail fragment resulted in missorting of beta(2)ARs to the RE, while the expression of various CART fragments or the depletion of actinin-4 had no detectable effect on beta(2)AR sorting. These results indicate that the actin cytoskeleton is required for the efficient recycling of beta(2)ARs, a process that likely is dependent on myosin Vb.
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Affiliation(s)
- Ellen E Millman
- Department of Pediatrics, Baylor College of Medicine, 6621 Fannin, CCC 1040.00, Houston, TX 77030, USA
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Kim OJ, Ariano MA, Namkung Y, Marinec P, Kim E, Han J, Sibley DR. D2 dopamine receptor expression and trafficking is regulated through direct interactions with ZIP. J Neurochem 2008; 106:83-95. [PMID: 18346199 DOI: 10.1111/j.1471-4159.2008.05348.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have used the yeast two-hybrid system to identify protein kinase C-zeta interacting protein (ZIP) as a novel interacting protein for the D(2) dopamine receptor (DAR). This interaction was identified by screening a rat brain cDNA library using the third intracellular loop of the D(2) DAR as bait. A partial-length cDNA encoding ZIP was isolated and characterized as specifically interacting with the third intracellular loop of the D(2) DAR, but not with the third intracellular loops of other DAR subtypes. Biochemical confirmation of the ZIP-D(2) DAR interaction was obtained by expressing the full-length ZIP and D(2) DAR proteins in mammalian cells and demonstrating that they could be co-immunoprecipitated. We further showed that ZIP and the D(2) DAR could be co-immunoprecipitated from endogenous brain tissues. Immunohistochemical analyses further revealed that ZIP and the D(2) DAR were extensively co-localized within numerous neurons in various brain regions. ZIP exists as three protein isoforms of varying length, which are derived from alternative RNA splicing. All three isoforms were found to interact with the D(2) DAR, which allowed for the delineation of the receptor interacting domain to within 38 residues of ZIP. Functionally, over-expression of ZIP was found to result in decreased expression of the D(2) DAR with a corresponding decrease in receptor modulation of cAMP accumulation. Confocal microscopy revealed that ZIP over-expression also lead to an intracellular accumulation of D(2) DAR protein in lysosome compartments. These results suggest that ZIP can physically interact with the D(2) DAR leading to increased intracellular trafficking to lysosomes with subsequent down-regulation of receptor expression and function.
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Affiliation(s)
- Ok-Jin Kim
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045-7582, USA.
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29
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Shenoy SK, Xiao K, Venkataramanan V, Snyder PM, Freedman NJ, Weissman AM. Nedd4 mediates agonist-dependent ubiquitination, lysosomal targeting, and degradation of the beta2-adrenergic receptor. J Biol Chem 2008; 283:22166-76. [PMID: 18544533 DOI: 10.1074/jbc.m709668200] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Agonist-stimulated beta(2)-adrenergic receptor (beta(2)AR) ubiquitination is a major factor that governs both lysosomal trafficking and degradation of internalized receptors, but the identity of the E3 ubiquitin ligase regulating this process was unknown. Among the various catalytically inactive E3 ubiquitin ligase mutants that we tested, a dominant negative Nedd4 specifically inhibited isoproterenol-induced ubiquitination and degradation of the beta(2)AR in HEK-293 cells. Moreover, siRNA that down-regulates Nedd4 expression inhibited beta(2)AR ubiquitination and lysosomal degradation, whereas siRNA targeting the closely related E3 ligases Nedd4-2 or AIP4 did not. Interestingly, beta(2)AR as well as beta-arrestin2, the endocytic and signaling adaptor for the beta(2)AR, interact robustly with Nedd4 upon agonist stimulation. However, beta(2)AR-Nedd4 interaction is ablated when beta-arrestin2 expression is knocked down by siRNA transfection, implicating an essential E3 ubiquitin ligase adaptor role for beta-arrestin2 in mediating beta(2)AR ubiquitination. Notably, beta-arrestin2 interacts with two different E3 ubiquitin ligases, namely, Mdm2 and Nedd4 to regulate distinct steps in beta(2)AR trafficking. Collectively, our findings indicate that the degradative fate of the beta(2)AR in the lysosomal compartments is dependent upon beta-arrestin2-mediated recruitment of Nedd4 to the activated receptor and Nedd4-catalyzed ubiquitination.
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Affiliation(s)
- Sudha K Shenoy
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
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30
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Koryakina YA, Fowler TW, Jones SM, Schnackenberg BJ, Cornett LE, Kurten RC. Characterization of a panel of six beta2-adrenergic receptor antibodies by indirect immunofluorescence microscopy. Respir Res 2008; 9:32. [PMID: 18423037 PMCID: PMC2383888 DOI: 10.1186/1465-9921-9-32] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Accepted: 04/18/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The beta2-adrenergic receptor (beta2AR) is a primary target for medications used to treat asthma. Due to the low abundance of beta2AR, very few studies have reported its localization in tissues. However, the intracellular location of beta2AR in lung tissue, especially in airway smooth muscle cells, is very likely to have a significant impact on how the airways respond to beta-agonist medications. Thus, a method for visualizing beta2AR in tissues would be of utility. The purpose of this study was to develop an immunofluorescent labeling technique for localizing native and recombinant beta2AR in primary cell cultures. METHODS A panel of six different antibodies were evaluated in indirect immunofluorescence assays for their ability to recognize human and rat beta2AR expressed in HEK 293 cells. Antibodies capable of recognizing rat beta2AR were identified and used to localize native beta2AR in primary cultures of rat airway smooth muscle and epithelial cells. beta2AR expression was confirmed by performing ligand binding assays using the beta-adrenergic antagonist [3H] dihydroalprenolol ([3H]DHA). RESULTS Among the six antibodies tested, we identified three of interest. An antibody developed against the C-terminal 15 amino acids of the human beta2AR (Ab-Bethyl) specifically recognized human but not rat beta2AR. An antibody developed against the C-terminal domain of the mouse beta2AR (Ab-sc570) specifically recognized rat but not human beta2AR. An antibody developed against 78 amino acids of the C-terminus of the human beta2AR (Ab-13989) was capable of recognizing both rat and human beta2ARs. In HEK 293 cells, the receptors were predominantly localized to the cell surface. By contrast, about half of the native rat beta2AR that we visualized in primary cultures of rat airway epithelial and smooth muscle cells using Ab-sc570 and Ab-13989 was found inside cells rather than on their surface. CONCLUSION Antibodies have been identified that recognize human beta2AR, rat beta2AR or both rat and human beta2AR. Interestingly, the pattern of expression in transfected cells expressing millions of receptors was dramatically different from that in primary cell cultures expressing only a few thousand native receptors. We anticipate that these antibodies will provide a valuable tool for evaluating the expression and trafficking of beta2AR in tissues.
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Affiliation(s)
- Yulia A Koryakina
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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31
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Delhaye M, Gravot A, Ayinde D, Niedergang F, Alizon M, Brelot A. Identification of a postendocytic sorting sequence in CCR5. Mol Pharmacol 2007; 72:1497-507. [PMID: 17855654 DOI: 10.1124/mol.107.038422] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The chemokine receptor 5 (CCR5), a member of the G protein-coupled receptor family (GPCR), is used by human immunodeficiency virus type 1 (HIV-1) with a R5 tropism as an entry receptor in addition to CD4. It is a key target for an antiviral action aiming at inhibiting the HIV-1 entry process. Only few data are available today regarding the mechanism involved in the intracellular trafficking process of CCR5. Understanding how CCR5 cell surface expression is regulated is particularly important with regard to HIV-1 entry inhibition. We set out to investigate whether CCR5 molecular determinants were involved in the postendocytic recycling and degradative pathways. We constructed progressive deletion mutants of the C-terminal domain of CCR5 that we stably expressed in HEK293 cells. All of the deletion mutants were expressed at the cell surface and were functional HIV-1 receptors. The deletion mutants were internalized after stimulation, but they lost their ability to recycle to the plasma membrane. They were rerouted toward a lysosomal degradative pathway. We identified here a sequence of four amino acids, present at the extreme C terminus of CCR5, that is necessary for the recycling of the internalized receptor, independently of its phosphorylation. A detailed analysis of this sequence indicated that the four amino acids acted as a postsynaptic density 95/discs-large/zona occludens (PDZ) interacting sequence. These results show that the CCR5 cytoplasmic domain bears a sequence similar to the "recycling signals" previously identified in other GPCRs. Drugs able to disrupt the recycling pathway of CCR5 may constitute promising tools for therapeutic treatment.
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Affiliation(s)
- Maurine Delhaye
- Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (Unité Mixte de Recherche 8104), Paris, France
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Bawolak MT, Gera L, Morissette G, Stewart JM, Marceau F. B-9972 (D-Arg-[Hyp3,Igl5,Oic7,Igl8]-bradykinin) Is an Inactivation-Resistant Agonist of the Bradykinin B2Receptor Derived from the Peptide Antagonist B-9430 (D-Arg-[Hyp3,Igl5,D-Igl7,Oic8]-bradykinin): Pharmacologic Profile and Effective Induction of Receptor Degradation. J Pharmacol Exp Ther 2007; 323:534-46. [PMID: 17699739 DOI: 10.1124/jpet.107.123422] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The bradykinin B(2) receptor is a heptahelical receptor regulated by a cycle of phosphorylation, endocytosis, and extensive recycling at the cell surface following agonist stimulation. B-9430 (d-Arg-[Hyp(3),Igl(5),D-Igl(7),Oic(8)]-bradykinin) is a second generation peptide antagonist found to be competitive at the human B(2) receptor and insurmountable at the rabbit B(2) receptor (contractility assays, isolated human umbilical and rabbit jugular veins). Two isomers of this peptide were prepared: B-10344 (D-Arg-[Hyp(3),Igl(5),Oic(7),D-Igl(8)]-bradykinin; inverted sequence Oic(7), D-Igl(8)) and B-9972 (D-Arg-[Hyp(3),Igl(5),Oic(7),Igl(8)]-bradykinin); they are low- and high-potency agonists, respectively, in vascular preparations. The potency gap between bradykinin and B-9972 is narrow in contractility assays, despite the fact that B-9972 affinity is 7-fold inferior at the rabbit B(2) receptor (radioligand binding competition assay). The effects of agonists on receptors were compared using two chimerical constructions based on rabbit B(2) receptors: conjugate of the B(2) receptor with green fluorescent protein (B(2)R-GFP) and the N-terminally tagged conjugate of the myc epitope with the B(2) receptor. Imaging and immunoblotting showed that B-9972 induced a persistent endocytosis of cell surface B(2) receptors in human embryonic kidney 293 cells with slow receptor degradation (weak after 3 h of treatment, important at 12 h) and B(2)R-GFP desensitization ([(3)H]bradykinin endocytosis and extracellular signal-regulated kinase 1/2 phosphorylation assays). Bradykinin was not active in this respect but when combined with captopril, induced some degradation. B-9430 reduced the endocytosis and degradation of B(2) receptors by the agonists. The results illustrate the agonist-antagonist transition in B(2) receptor peptide ligands with a constrained C-terminal structure, the importance of species in their pharmacological profile, and the possibility of selectively degrading receptors using a peptidase-resistant agonist.
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Affiliation(s)
- Marie-Thérèse Bawolak
- Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, Quebec, Canada
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33
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Dupré DJ, Thompson C, Chen Z, Rollin S, Larrivée JF, Le Gouill C, Rola-Pleszczynski M, Stanková J. Inverse agonist-induced signaling and down-regulation of the platelet-activating factor receptor. Cell Signal 2007; 19:2068-79. [PMID: 17609120 DOI: 10.1016/j.cellsig.2007.05.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 05/25/2007] [Accepted: 05/28/2007] [Indexed: 11/16/2022]
Abstract
Platelet-activating factor (PAF) is a potent phospholipid mediator involved in several diseases such as allergic asthma, atherosclerosis and psoriasis. The human PAF receptor (PAFR) is a member of the G-protein-coupled receptor family. Following stimulation, PAFR becomes rapidly desensitized; this refractory state is dependent on PAFR phosphorylation, internalization and down-regulation. In this report, we show that the PAFR inverse agonist, WEB2086, can induce phosphorylation and down-regulation of PAFR. Using selective inhibitors, we determined that the agonist, PAF, and WEB2086 could induce phosphorylation of PAFR by PKC. Moreover, dominant-negative (DN) mutant of PKC isoforms beta inhibited WEB2086-stimulated PAFR phosphorylation, whereas PAF-stimulated phosphorylation was inhibited by DN PKCalpha and delta. WEB2086 also induced PAFR down-regulation which could be blocked by PKC inhibitors and by DN PKCbeta. WEB2086-induced down-regulation was dynamin-dependent but arrestin-independent. Unlike PAF, WEB2086-stimulated intracellular trafficking of PAFR was independent of Rab5. Specific inhibitors of lysosomal proteases and of proteasomes were both effective in reducing WEB2086-induced PAFR down-regulation, indicating the importance of receptor targeting to both lysosomes and proteasomes in long-term cell desensitization to WEB2086. These results indicate that although both agonists and inverse agonists induce receptor PAFR down-regulation, this may be accomplished through different signal transduction and trafficking pathways.
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Affiliation(s)
- Denis J Dupré
- Immunology Division, Department of Pediatrics, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, 3001 12th Avenue North, Sherbrooke, Quebec, Canada
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Awwad HO, Iyer V, Rosenfeld JL, Millman EE, Foster E, Moore RH, Knoll BJ. Inhibitors of phosphoinositide 3-kinase cause defects in the postendocytic sorting of beta2-adrenergic receptors. Exp Cell Res 2007; 313:2586-96. [PMID: 17553490 PMCID: PMC2034330 DOI: 10.1016/j.yexcr.2007.04.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Revised: 04/18/2007] [Accepted: 04/18/2007] [Indexed: 11/16/2022]
Abstract
Phosphatidylinositol 3-kinase inhibitors have been shown to affect endocytosis or subsequent intracellular sorting in various receptor systems. Agonist-activated beta(2)-adrenergic receptors undergo desensitization by mechanisms that include the phosphorylation, endocytosis and degradation of receptors. Following endocytosis, most internalized receptors are sorted to the cell surface, but some proportion is sorted to lysosomes for degradation. It is not known what governs the ratio of receptors that recycle versus receptors that undergo degradation. To determine if phosphatidylinositol 3-kinases regulate beta(2)-adrenergic receptor trafficking, HEK293 cells stably expressing these receptors were treated with the phosphatidylinositol 3-kinase inhibitors LY294002 or wortmannin. We then studied agonist-induced receptor endocytosis and postendocytic sorting, including recycling and degradation of the internalized receptors. Both inhibitors amplified the internalization of receptors after exposure to the beta-agonist isoproterenol, which was attributable to the sorting of a significant fraction of receptors to an intracellular compartment from which receptor recycling did not occur. The initial rate of beta(2)-adrenergic receptor endocytosis and the default rate of receptor recycling were not significantly altered. During prolonged exposure to agonist, LY294002 slowed the degradation rate of beta(2)-adrenergic receptors and caused the accumulation of receptors within rab7-positive vesicles. These results suggest that phosphatidylinositol 3-kinase inhibitors (1) cause a misrouting of beta(2)-adrenergic receptors into vesicles that are neither able to efficiently recycle to the surface nor sort to lysosomes, and (2) delays the movement of receptors from late endosomes to lysosomes.
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Affiliation(s)
- Hibah O. Awwad
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Varsha Iyer
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Jennifer L. Rosenfeld
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Ellen E. Millman
- Department of Pediatrics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, Texas 77030
| | - Estrella Foster
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Robert H. Moore
- Department of Pediatrics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, Texas 77030
| | - Brian J. Knoll
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
- **Corresponding author: Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Bldg. 2, Rm. 521D, Houston, Texas 77204, Phone:713–743–1299; FAX 713–743–1229;
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Iyer V, Tran TM, Foster E, Dai W, Clark RB, Knoll BJ. Differential phosphorylation and dephosphorylation of beta2-adrenoceptor sites Ser262 and Ser355,356. Br J Pharmacol 2006; 147:249-59. [PMID: 16331289 PMCID: PMC1751300 DOI: 10.1038/sj.bjp.0706551] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Activated beta2-adrenoceptors are rapidly desensitized by phosphorylation of Ser262 by protein kinase A (PKA) and of Ser355,356 by G-protein-coupled receptor kinase (GRK). We sought to determine whether the phosphorylation and subsequent dephosphorylation of these sites had similar kinetics and requirements for receptor endocytosis. The phosphorylation of the PKA and GRK sites were measured using antibodies that recognize phosphoserine 262 and phosphoserine 355,356. Endocytosis in stably transfected HEK293 cells was blocked by inducible expression of dominant-negative dynamin-1 K44A or by treatment with hypertonic sucrose. The phosphorylation of the GRK site Ser355,356 during a 10 microM isoprenaline treatment rapidly reached a steady state, and the extent of kinetics of phosphorylation were unaffected by dynamin-1 K44A expression, and minimally by hypertonic sucrose. In contrast, phosphorylation of the PKA site Ser262 during a 10 microM isoprenaline treatment peaked after 2 min and then rapidly declined, while inhibition of endocytosis enhanced and prolonged phosphorylation. Treatment with 300 pM isoprenaline, a concentration too low to provoke endocytosis, also resulted in prolonged PKA site phosphorylation. The dephosphorylation of these sites was measured after removal of agonist. Significant dephosphorylation of phosphoserines 262 and 355,356 was observed under conditions of very low endocytosis, however dephosphorylation of the GRK site was greater if antagonist was present after removal of agonist. The results indicate that the kinetics of beta2-adrenoceptor GRK and PKA site phosphorylation are distinct and differently affected by endocytosis, and that receptor dephosphorylation can occur either at the plasma membrane or in internal compartments.
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Affiliation(s)
- Varsha Iyer
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston College of Pharmacy, Rm 521D, Science and Research Bldg 2, Houston, TX 77204, U.S.A
| | - Tuan M Tran
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School, P.O. Box 20708, Houston, TX 77225, U.S.A
| | - Estrella Foster
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston College of Pharmacy, Rm 521D, Science and Research Bldg 2, Houston, TX 77204, U.S.A
| | - Wenping Dai
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston College of Pharmacy, Rm 521D, Science and Research Bldg 2, Houston, TX 77204, U.S.A
| | - Richard B Clark
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School, P.O. Box 20708, Houston, TX 77225, U.S.A
| | - Brian J Knoll
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston College of Pharmacy, Rm 521D, Science and Research Bldg 2, Houston, TX 77204, U.S.A
- Author for correspondence:
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Dupré DJ, Hébert TE. Biosynthesis and trafficking of seven transmembrane receptor signalling complexes. Cell Signal 2006; 18:1549-59. [PMID: 16677801 DOI: 10.1016/j.cellsig.2006.03.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 03/21/2006] [Indexed: 12/16/2022]
Abstract
Recent studies have shown that 7-transmembrane receptors (7TM-Rs), their associated signalling molecules and scaffolding proteins are often constitutively associated under basal conditions. These studies highlight that receptor ontogeny and trafficking are likely to play key roles in the determination of both signalling specificity and efficacy. This review highlights information about how 7TM-Rs and their associated signalling molecules are trafficked to the cell surface as well as other intracellular destinations.
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Affiliation(s)
- Denis J Dupré
- Department of Pharmacology and Therapeutics, McIntyre Medical Sciences Building, 3655 Promenade Sir William Osler, Montréal, Québec, Canada H3G 1Y6
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Moore RH, Millman EE, Godines V, Hanania NA, Tran TM, Peng H, Dickey BF, Knoll BJ, Clark RB. Salmeterol stimulation dissociates beta2-adrenergic receptor phosphorylation and internalization. Am J Respir Cell Mol Biol 2006; 36:254-61. [PMID: 16980556 PMCID: PMC1899312 DOI: 10.1165/rcmb.2006-0158oc] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Salmeterol is a long-acting beta(2)-adrenergic receptor (beta(2)AR) agonist commonly used in the treatment of asthma and chronic obstructive pulmonary disease. It differs from other beta-agonists in that it has a very low intrinisic efficacy, especially when compared with the other available long-acting beta-agonist, formoterol. Receptor desensitization and down-regulation has been described with the chronic use of beta-agonists. This effect may not be the same with all beta-agonists and may be related to their stabilization of altered receptor states. The extreme hydrophobicity and high-affinity quasi-irreversible binding of salmeterol have rendered studies examining the mechanisms by which it mediates receptor desensitization, down-regulation, and internalization difficult. We determined the capacity of salmeterol to induce beta(2)AR endocytosis, G protein-coupled receptor kinase (GRK)-site phosphorylation, degradation, and beta-arrestin2 translocation in HEK293 cells as compared with other agonists of varying intrinsic efficacies. Despite stimulating GRK-mediated phosphorylation of Ser355,356 after 30 min and 18 h to an extent similar to that observed with agonists of high intrinsic efficacy, such as epinephrine and formoterol, salmeterol did not induce significant beta(2)AR internalization or degradation and was incapable of stimulating the translocation of enhanced green fluorescent protein-beta-arrestin2 chimera (EGFP-beta-arrestin2) to the cell surface. Salmeterol-induced receptor endocytosis was rescued, at least in part, by the overexpression of EGFP-beta-arrestin2. Our data indicate that salmeterol binding induces an active receptor state that is unable to recruit beta-arrestin or undergo significant endocytosis or degradation despite stimulating considerable GRK-site phosphorylation. Defects in these components of salmeterol-induced receptor desensitization may be important determinants of its sustained bronchodilation with chronic use.
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Affiliation(s)
- Robert H Moore
- Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
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38
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Ogasawara J, Sanpei M, Rahman N, Sakurai T, Kizaki T, Hitomi Y, Ohno H, Izawa T. Beta-adrenergic receptor trafficking by exercise in rat adipocytes: roles of G-protein-coupled receptor kinase-2, beta-arrestin-2, and the ubiquitin-proteasome pathway. FASEB J 2005; 20:350-2. [PMID: 16368719 DOI: 10.1096/fj.05-4688fje] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The effect of exercise on beta-adrenergic receptor (beta-AR) trafficking was investigated in rat adipocytes. The binding sites of a hydrophilic ligand, [(3)H]CGP12177, increased immediately (0 h) and at 3 h after exercise (3 h) but decreased at 24 h after exercise (24 h). The data of immunoblotting revealed that the alterations in the binding sites mainly paralleled the alterations in the beta2-AR proteins in membrane fractions. The protein expressions of both G-protein-coupled receptor kinase (GRK)-2 and beta-arrestin-2 were reduced, with a decline in beta2-AR ubiquitination at 0 h and 3 h. The protein expressions of beta2-AR, GRK-2, beta-arrestin-2, the beta2-AR/beta-arrestin-2 complex, and beta2-AR ubiquitination returned to their respective control levels at 24 h, whereas the beta2-AR mRNA level was reduced. Administration of either lactacystin or propranolol did not alter GRK-2 and beta2-AR protein expressions after exercise. Thus, the mechanism underlying the increased density of beta2-AR up to at least 3 h may involve alterations in a multistep event involving the coordinate interaction among proteins mediating beta2-AR trafficking, in which both the receptor-agonist interactions and ubiquitin-proteasome pathway have a key role. However, the decreased protein expression of beta2-AR at 24 h might be due to some change occurring at the translational levels.
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Affiliation(s)
- Junetsu Ogasawara
- Department of Kinesiology, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
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Hynes TR, Mervine SM, Yost EA, Sabo JL, Berlot CH. Live cell imaging of Gs and the beta2-adrenergic receptor demonstrates that both alphas and beta1gamma7 internalize upon stimulation and exhibit similar trafficking patterns that differ from that of the beta2-adrenergic receptor. J Biol Chem 2004; 279:44101-12. [PMID: 15297467 DOI: 10.1074/jbc.m405151200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
To visualize and investigate the regulation of the localization patterns of Gs and an associated receptor during cell signaling, we produced functional fluorescent fusion proteins and imaged them in HEK-293 cells. alphas-CFP, with cyan fluorescent protein (CFP) inserted into an internal loop of alphas, localized to the plasma membrane and exhibited similar receptor-mediated activity to that of alphas. Functional fluorescent beta1gamma7 dimers were produced by fusing an amino-terminal yellow fluorescent protein (YFP) fragment to beta1 (YFP-N-beta1) and a carboxyl-terminal YFP fragment to gamma7 (YFP-C-gamma7). When expressed together, YFP-N-beta1 and YFP-C-gamma7 produced fluorescent signals in the plasma membrane that were not seen when the subunits were expressed separately. Isoproterenol stimulation of cells co-expressing alphas-CFP, YFP-N-beta1/YFP-C-gamma7, and the beta2-adrenergic receptor (beta2AR) resulted in internalization of both fluorescent signals from the plasma membrane. Initially, alphas-CFP and YFP-N-beta1/YFP-C-gamma7 stained the cytoplasm diffusely, and subsequently they co-localized on vesicles that exhibited minimal overlap with beta2AR-labeled vesicles. Moreover, internalization of beta2AR-GFP, but not alphas-CFP or YFP-N-beta1/YFP-C-gamma7, was inhibited by a fluorescent dominant negative dynamin 1 mutant, Dyn1(K44A)-mRFP, indicating that the Gs subunits and beta2AR utilize different internalization mechanisms. Subsequent trafficking of the Gs subunits and beta2AR also differed in that vesicles labeled with the Gs subunits exhibited less overlap with RhoB-labeled endosomes and greater overlap with Rab11-labeled endosomes. Because Rab11 regulates traffic through recycling endosomes, co-localization of alphas and beta1gamma7 on these endosomes may indicate a means of recycling specific alphasbetagamma combinations to the plasma membrane.
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Affiliation(s)
- Thomas R Hynes
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2623, USA
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40
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Mialet-Perez J, Green SA, Miller WE, Liggett SB. A primate-dominant third glycosylation site of the beta2-adrenergic receptor routes receptors to degradation during agonist regulation. J Biol Chem 2004; 279:38603-7. [PMID: 15247302 DOI: 10.1074/jbc.m403708200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta(2)-adrenergic receptors (beta(2)AR) of all species are N-linked glycosylated at amino terminus residues approximately 6 and approximately 15. However, the human beta(2)AR has a potential third N-glycosylation site at ECL2 residue 187. To determine whether this residue is glycosylated and to ascertain function, all possible single/multiple Asn --> Gln mutations were made in the human beta(2) AR at positions 6, 15, and 187 and were expressed in Chinese hamster fibroblast cells. Substitution of Asn-187 alone or with Asn-6 or Asn-15 decreased the apparent molecular mass of the receptor on SDS-PAGE in a manner consistent with Asn-187 glycosylation. All receptors bound the agonist isoproterenol and functionally coupled to adenylyl cyclase. However, receptors without 187 glycosylation failed to display long term agonist-promoted down-regulation. In contrast, loss of Asn-6/Asn-15 glycosylation did not alter down-regulation. Cell surface distribution and agonist-promoted internalization of receptors and recruitment of beta-arrestin 2 were unaffected by the loss of 187 glycosylation. Furthermore, acutely internalized wild-type and Gln-187 receptors were both localized by confocal microscopy to early endosomes. During prolonged agonist exposure, wild-type beta(2)AR co-localized with lysosomes, consistent with trafficking to a degradation compartment. However, Gln-187 beta(2)AR failed to co-localize with lysosomes despite agonist treatments up to 18 h. Phylogenetic analysis revealed that this third glycosylation site is found in humans and other higher order primates but not in lower order primates such as the monkey. Nor is this third site found in rodents, which are frequently utilized as animal models. These data thus reveal a previously unrecognized beta(2)AR regulatory motif that appeared late in primate evolution and serves to direct internalized receptors to lysosomal degradation during long term agonist exposure.
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Affiliation(s)
- Jeanne Mialet-Perez
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA
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41
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Moore RH, Millman EE, Alpizar-Foster E, Dai W, Knoll BJ. Rab11 regulates the recycling and lysosome targeting of beta2-adrenergic receptors. J Cell Sci 2004; 117:3107-17. [PMID: 15190120 DOI: 10.1242/jcs.01168] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The pericentriolar recycling endosome (RE) may be an alternative compartment through which some beta2-adrenergic receptors (beta2ARs) recycle from early endosomes to the cell surface during prolonged exposure to agonist. For the transferrin receptor, CXCR2, and the M4-muscarinic acetylcholine receptor, trafficking through the RE and receptor recycling is regulated by the small GTPase rab11. The precise role of the RE and rab11 in regulating the cellular trafficking of the beta2AR is not understood. We therefore monitored trafficking of beta2ARs in HEK293 cells following the modulation of rab11 activity. Expression of a rab11 mutant deficient in GTP binding (as a fusion between enhanced green fluorescent protein (EGFP) and the rab11S25N mutant) significantly slowed receptor recycling to the cell surface from dispersed transferrin-positive peripheral vesicles following a brief exposure to agonist. The agonist was applied at a time when receptors have undergone only one or two rounds of endocytosis and recycling. In cells overexpressing wild-type rab11, beta2ARs localized to a rab11-positive compartment and the rate of beta2AR recycling to the cell surface was reduced, but only after prolonged exposure to agonist and multiple rounds of receptor endocytosis and recycling. This effect was associated with impaired beta2AR trafficking to lysosomes and receptor proteolysis, whereas the sorting of low-density lipoprotein from transferrin-positive vesicles to late endosomes and lysosomes was not affected. These data highlight a pivotal role for rab11 in regulating the traffic of a G protein-coupled receptor at the level of the RE, where modulation of rab11 activity dictates the balance between receptor recycling and downregulation during prolonged exposure to agonist.
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Affiliation(s)
- Robert H Moore
- Department of Pediatrics, Baylor College of Medicine, 6621 Fannin, CCC 1040.00, Houston, TX 77030, USA
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42
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Thériault C, Rochdi MD, Parent JL. Role of the Rab11-Associated Intracellular Pool of Receptors Formed by Constitutive Endocytosis of the β Isoform of the Thromboxane A2 Receptor (TPβ). Biochemistry 2004; 43:5600-7. [PMID: 15134434 DOI: 10.1021/bi036268v] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intracellular trafficking pathways of G protein-coupled receptors (GPCRs), following their agonist-induced endocytosis and their consequences on receptor function, are the subject of intense research efforts. However, less is known regarding their constitutive endocytosis. We previously demonstrated that the beta isoform of the thromboxane A(2) receptor (TPbeta) undergoes constitutive and agonist-induced endocytosis. Constitutive endocytosis of GPCRs can lead to the formation of an intracellular pool of receptors from which they can recycle back to the cell surface. In the present report, we show with the help of two TPbeta mutants (TPbeta-Y339A and TPbeta-I343A) specifically deficient in constitutive endocytosis that this intracellular pool of receptors serves to maintain agonist sensitivity over prolonged receptor stimulation in HEK293 cells. Second messenger generation by the TPbeta-Y339A and TPbeta-I343A mutants was drastically reduced compared to the wild-type receptor as suggested by dose-response and time-course experiments of inositol phosphates production following agonist treatment, despite normal coupling between the receptors and the Galpha(q) protein. Moreover, second messenger production after receptor activation was dramatically reduced when cells were pretreated with monensin, a recycling inhibitor. Receptor cell surface expression and endocytosis experiments further revealed that the small GTPase Rab11 protein is a determinant factor in controlling TPbeta recycling back to the cell surface. Co-localization experiments performed by immunofluorescence microscopy indicated that both constitutive and agonist-triggered endocytosis resulted in targeting of TPbeta to the Rab11-positive recycling endosome. Thus, we provide evidence that constitutive endocytosis of TPbeta forms a pool of receptors in the perinuclear recycling endosome from which they recycle to the cell surface, a process involved in preserving receptor sensitivity to agonist stimulation.
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Affiliation(s)
- Caroline Thériault
- Service de Rhumatologie, Faculté de Médecine and Centre de Recherche Clinique-CHUS, Université de Sherbrooke, Sherbrooke, Québec, Canada, J1H 5N4
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43
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Dale LB, Seachrist JL, Babwah AV, Ferguson SSG. Regulation of Angiotensin II Type 1A Receptor Intracellular Retention, Degradation, and Recycling by Rab5, Rab7, and Rab11 GTPases. J Biol Chem 2004; 279:13110-8. [PMID: 14711821 DOI: 10.1074/jbc.m313333200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have demonstrated that the interaction of the angiotensin II type 1A receptor (AT(1A)R) carboxyl-terminal tail with Rab5a may modulate Rab5a activity, leading to the homotypic fusion of endocytic vesicles. Therefore, we have investigated whether AT(1A)R/Rab5a interactions mediate the retention of AT(1A)R.beta-arrestin complexes in early endosomes and whether the overexpression of Rab7 and Rab11 GTPases influences AT(1A)R lysosomal degradation and plasma membrane recycling. We found that internalized AT(1A)R was retained in Rab5a-positive early endosomes and was neither targeted to lysosomes nor recycled back to the cell surface, whereas a mutant defective in Rab5a binding, AT(1A)R-(1-349), was targeted to lysosomes for degradation. However, the loss of Rab5a binding to the AT(1A)R carboxyl-terminal tail did not promote AT(1A)R recycling. Rather, it was the stable binding of beta-arrestin to the AT(1A)R that prevented, at least in part, AT(1A)R recycling. The overexpression of wild-type Rab7 and Rab7-Q67L resulted in both increased AT(1A)R degradation and AT(1A)R targeting to lysosomes. The Rab7 expression-dependent transition of "putative" AT(1A)R.beta-arrestin complexes to late endosomes was blocked by the expression of dominant-negative Rab5a-S34N. Rab11 overexpression established AT(1A)R recycling and promoted the redistribution of AT(1A)R.beta-arrestin complexes from early to recycling endosomes. Taken together, our data suggest that Rab5, Rab7, and Rab11 work in concert with one another to regulate the intracellular trafficking patterns of the AT(1A)R.
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Affiliation(s)
- Lianne B Dale
- Cell Biology Research Group, Robarts Research Institute, 100 Perth Drive, London, Ontario N6A 5K8, Canada
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44
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Liang W, Curran PK, Hoang Q, Moreland RT, Fishman PH. Differences in endosomal targeting of human (beta)1- and (beta)2-adrenergic receptors following clathrin-mediated endocytosis. J Cell Sci 2004; 117:723-34. [PMID: 14734649 DOI: 10.1242/jcs.00878] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The beta(2)-adrenergic receptor (beta(2)AR) undergoes agonist-mediated endocytosis via clathrin-coated pits by a process dependent on both arrestins and dynamin. Internalization of some G protein-coupled receptors, however, is independent of arrestins and/or dynamin and through other membrane microdomains such as caveolae or lipid rafts. The human beta(1)AR is less susceptible to agonist-mediated internalization than the beta(2)-subtype, and its endocytic route, which is unknown, may be different. We have found that (i) co-expression of arrestin-2 or -3 enhanced the internalization of both subtypes whereas co-expression of dominant-negative mutants of arrestin-2 or dynamin impaired their internalization, as did inhibitors of clathrin-mediated endocytosis. (ii) Agonist stimulation increased the phosphorylation of beta(2)AR but not beta(1)AR. (iii) In response to agonist, each subtype redistributed from the cell surface to a distinct population of cytoplasmic vesicles; those containing beta(1)AR were smaller and closer to the plasma membrane whereas those containing beta(2)AR were larger and more perinuclear. (iv) When subcellular fractions from agonist-treated cells were separated by sucrose density gradient centrifugation, all of the internalized beta(2)AR appeared in the lighter endosomal-containing fractions whereas some of the internalized beta(1)AR remained in the denser plasma membrane-containing fractions. (v) Both subtypes recycled with similar kinetics back to the cell surface upon removal of agonist; however, recycling of beta(2)AR but not beta(1)AR was inhibited by monensin. Based on these results, we propose that the internalization of beta(1)AR is both arrestin- and dynamin-dependent and follows the same clathrin-mediated endocytic pathway as beta(2)AR. But during or after endocytosis, beta(1)AR and beta(2)AR are sorted into different endosomal compartments.
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Affiliation(s)
- Wei Liang
- Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, The National Institutes of Health, Bethesda, MD 20892, USA
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45
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Seachrist JL, Ferguson SSG. Regulation of G protein-coupled receptor endocytosis and trafficking by Rab GTPases. Life Sci 2004; 74:225-35. [PMID: 14607250 DOI: 10.1016/j.lfs.2003.09.009] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G protein-coupled receptors (GPCRs) are integral membrane proteins that, in response to activation by extracellular stimuli, regulate intracellular second messenger levels via their coupling to heterotrimeric G proteins. GPCR activation also initiates a series of molecular events that leads to G protein-coupled receptor kinase-mediated receptor phosphorylation and the binding of beta-arrestin proteins to the intracellular face of the receptor. beta-Arrestin binding not only contributes to the G protein-uncoupling of GPCRs, but also mediates the targeting of many GPCRs for endocytosis in clathrin-coated pits. Several GPCRs internalize as a stable complex with beta-arrestin and the stability of this complex appears to regulate, at least in part, whether the receptors are dephosphorylated in early endosomes and recycled back to the cell surface as fully functional receptors, retained in early endosomes or targeted for degradation in lysosomes. More recently, it has become appreciated that the movement of GPCRs through functionally distinct intracellular membrane compartments is regulated by a variety of Rab GTPases and that the activity of these Rab GTPases may influence GPCR function. Moreover, it appears that GPCRs are not simply passive cargo molecules, but that GPCR activation may directly influence Rab GTPase activity and as such, GPCRs may directly control their own targeting between intracellular compartments. This review provides a synopsis of the current knowledge regarding the role of beta-arrestins and Rab GTPases in regulating the intracellular trafficking and function of GPCRs.
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Affiliation(s)
- Jennifer L Seachrist
- Cell Biology Research Group, Robarts Research Institute, 100 Perth Dr., N6A 5K8, London, Ontario, Canada
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46
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Millman EE, Rosenfeld JL, Vaughan DJ, Nguyen J, Dai W, Alpizar-Foster E, Clark RB, Knoll BJ, Moore RH. Endosome sorting of beta 2-adrenoceptors is GRK5 independent. Br J Pharmacol 2003; 141:277-84. [PMID: 14691047 PMCID: PMC1574185 DOI: 10.1038/sj.bjp.0705504] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We have investigated the role of G protein-coupled receptor kinase 5 (GRK5) in the regulation of endosome sorting of human beta(2)-adrenoceptors. 2. Expressing GRK5 at a high level significantly increased the extent of internalization of wild-type beta(2)-adrenoceptors and of an internalization-defective mutant receptor, and increased receptor phosphorylation at serines 355 and 356 in the cytoplasmic tail. 3. Overexpressing GRK5 did not alter beta(2)-adrenoceptor recycling as assessed by immunofluorescence microscopy and radioligand binding assays nor was there any change in receptor downregulation. 4. These data indicate that GRK5 does not regulate the sorting of beta(2)-adrenoceptors in the endocytic pathway.
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Affiliation(s)
- Ellen E Millman
- Department of Pediatrics and Molecular Physiology and Biophysics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, TX 77030, U.S.A
| | - Jennifer L Rosenfeld
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Bldg 2, Rm 521D, Houston, TX 77204, U.S.A
| | - David J Vaughan
- Department of Pediatrics and Molecular Physiology and Biophysics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, TX 77030, U.S.A
| | - Jacqueline Nguyen
- Department of Pediatrics and Molecular Physiology and Biophysics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, TX 77030, U.S.A
| | - WenPing Dai
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Bldg 2, Rm 521D, Houston, TX 77204, U.S.A
| | - Estrella Alpizar-Foster
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Bldg 2, Rm 521D, Houston, TX 77204, U.S.A
| | - Richard B Clark
- Department of Integrative Biology and Pharmacology, University of Texas Health Sciences Center-Houston, 6431 Fannin, Houston, TX, 77030, U.S.A
| | - Brian J Knoll
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Bldg 2, Rm 521D, Houston, TX 77204, U.S.A
| | - Robert H Moore
- Department of Pediatrics and Molecular Physiology and Biophysics, Baylor College of Medicine, 6621 Fannin, CCC1040, Houston, TX 77030, U.S.A
- Author for correspondence:
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47
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Toews ML, Prinster SC, Schulte NA. Regulation of alpha-1B adrenergic receptor localization, trafficking, function, and stability. Life Sci 2003; 74:379-89. [PMID: 14607266 DOI: 10.1016/j.lfs.2003.09.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The alpha-1 adrenergic receptors (alpha(1)ARs) play important roles in normal physiology and in many disease states, and understanding their signaling pathways and regulatory mechanisms is thus of considerable relevance, in particular for identifying pharmacological targets for therapeutic modulation. The expression, function, localization, trafficking, and stability of these receptors are all subject to complex regulation by diverse molecular mechanisms. This article highlights recent studies from our laboratory and others focused on the localization and trafficking of the alpha-1B adrenergic receptor (alpha(1B)AR) subtype and on changes in its stability that are likely to be involved in regulating receptor expression. The role(s) of protein kinase C in alpha(1B)AR sequestration, endocytosis, and extracellular signal-regulated kinase (ERK) activation are summarized, and evidence for alpha(1B)AR localization in caveolae/rafts is presented. Receptor structural domains involved in the multiple steps and mechanisms of agonist-induced desensitization are described. Finally, aspects of alpha(1B)AR structural stability that appear to control its drug-induced up- and down-regulation are discussed. Our understanding of regulation for the alpha(1B)AR subtype provides a model for studies of the differential regulation of the other alpha(1)AR subtypes and may lead to identification of new molecular targets for therapeutic intervention in a variety of disease states.
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Affiliation(s)
- Myron L Toews
- Department of Pharmacology, University of Nebraska Medical Center, 986260 Nebraska Medical Center, Omaha, NE 68198-6260, USA.
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Abstract
A variety of receptors have been analyzed in sufficient detail to identify sorting motifs. Initial studies focused on the identification of sequences in the cytoplasmic tails of the LDL and transferrin receptors that mediated their internalization. These motifs have since been found in the cytoplasmic domains of a wide variety of receptors and provide for numerous sorting functions. This review will outline the early studies on LDL and transferrin receptors and will then focus on two classes of signaling receptors, receptor tyrosine kinases (EGF and the insulin receptors) and heterotrimeric G-protein coupled receptors (beta2-adrenergic receptors). The identification of sorting motifs and proteins that bind these motifs will be discussed. Importantly, the studies identify a variety of potential targets for modulating the sorting and hence activity of these medically important receptors.
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MESH Headings
- Amino Acid Motifs
- Animals
- Endocytosis/physiology
- ErbB Receptors/metabolism
- ErbB Receptors/physiology
- Humans
- Protein Sorting Signals/physiology
- Receptor, Insulin/metabolism
- Receptor, Insulin/physiology
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Adrenergic, beta-2/physiology
- Receptors, Cell Surface/metabolism
- Receptors, Cell Surface/physiology
- Receptors, LDL/metabolism
- Receptors, LDL/physiology
- Receptors, Transferrin/metabolism
- Receptors, Transferrin/physiology
- Signal Transduction
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Affiliation(s)
- Richard C Kurten
- Department Physiology and Biophysics, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72005, USA.
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49
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Liang W, Austin S, Hoang Q, Fishman PH. Resistance of the human beta 1-adrenergic receptor to agonist-mediated down-regulation. Role of the C terminus in determining beta-subtype degradation. J Biol Chem 2003; 278:39773-81. [PMID: 12888573 DOI: 10.1074/jbc.m304482200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Prolonged agonist stimulation results in down-regulation of most G protein-coupled receptors. When we exposed baby hamster kidney cells stably expressing the human beta1-adrenergic receptor (beta 1AR) to agonist over a 24-h period, we instead observed an increase of approximately 30% in both beta 1AR binding activity and immune-detected receptors. In contrast, beta 2AR expressed in these cells exhibited a decrease of > or =50%. We determined that the basal turnover rates of the two subtypes were similar (t(1/2) approximately 7 h) and that agonist stimulation increased beta 2AR but not beta 1AR turnover. Blocking receptor trafficking to lysosomes with bafilomycin A1 had no effect on basal turnover of either subtype but blocked agonist-stimulated beta 2AR turnover. As beta 1AR mRNA levels increased in agonist-stimulated cells, beta 1AR up-regulation appeared to result from increased synthesis with no change in degradation. To explore the basis for the subtype differences, we expressed chimeras in which the C termini had been exchanged. Each chimera responded to persistent agonist stimulation based on the source of its C-tail; beta 1AR with a beta 2AR C-tail underwent down-regulation, and beta 2AR with a beta 1AR C-tail underwent up-regulation. The C-tails had a corresponding effect on agonist-stimulated receptor phosphorylation and internalization with the order being beta 2AR > beta 1AR with beta 2AR C-tail > beta 2AR with a beta 1AR C-tail > beta 1AR. As internalization may be a prerequisite for down-regulation, we addressed this possibility by co-expressing each subtype with arrestin-2. Although beta 1AR internalization was increased to that of beta 2AR, down-regulation still did not occur. Instead, beta 1AR accumulated inside the cells. We conclude that in unstimulated cells, both subtypes appear to be turned over by the same mechanism. Upon agonist stimulation, both subtypes are internalized, and beta 2AR but not beta 1AR undergoes lysosomal degradation, the fate of each subtype being regulated by determinants in its C-tail.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Amino Acid Sequence
- Animals
- Base Sequence
- Cell Line
- Cricetinae
- DNA, Complementary/genetics
- Down-Regulation/drug effects
- Humans
- Kinetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/drug effects
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
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Affiliation(s)
- Wei Liang
- Membrane Biochemistry Section, Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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50
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Wang W, Loh HH, Law PY. The intracellular trafficking of opioid receptors directed by carboxyl tail and a di-leucine motif in Neuro2A cells. J Biol Chem 2003; 278:36848-58. [PMID: 12851402 DOI: 10.1074/jbc.m301540200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mu- and delta-opioid receptors (MOR and DOR) differ significantly in their intracellular trafficking. MORs recycle back to the cell surface upon agonist treatment, whereas most internalized DORs are targeted to lysosomes for degradation. By exchanging the carboxyl tail domains of MOR and DOR and expressing the receptor chimeras in mouse neuroblastoma Neuro2A cells, it could be demonstrated that the carboxyl tail domain is not the sole determinant in directing the intracellular trafficking in these Neuro2A cells. Deletion of the dileucine motif (Leu245-Leu246) within the third intracellular loop of DOR or the mutation of Leu245 to Met slowed the lysosomal targeting of these delta-opioid receptors. Meanwhile the mutation of Met264 to Leu increased the rate of agonist-induced receptor internalization and the lysosomal targeting of the wild type and the delta-opioid receptor carboxyl tail chimera of the mu-opioid receptor. These studies suggest interplay between a di-leucine motif and the carboxyl tail in the lysosomal targeting of the receptor.
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Affiliation(s)
- Wei Wang
- Department of Pharmacology, Medical School, University of Minnesota, Minneapolis, Minnesota 55455-0217, USA
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