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Sander CL, Luu J, Kim K, Furkert D, Jang K, Reichenwallner J, Kang M, Lee HJ, Eger BT, Choe HW, Fiedler D, Ernst OP, Kim YJ, Palczewski K, Kiser PD. Structural evidence for visual arrestin priming via complexation of phosphoinositols. Structure 2022; 30:263-277.e5. [PMID: 34678158 PMCID: PMC8818024 DOI: 10.1016/j.str.2021.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/06/2021] [Accepted: 09/29/2021] [Indexed: 02/05/2023]
Abstract
Visual arrestin (Arr1) terminates rhodopsin signaling by blocking its interaction with transducin. To do this, Arr1 translocates from the inner to the outer segment of photoreceptors upon light stimulation. Mounting evidence indicates that inositol phosphates (InsPs) affect Arr1 activity, but the Arr1-InsP molecular interaction remains poorly defined. We report the structure of bovine Arr1 in a ligand-free state featuring a near-complete model of the previously unresolved C-tail, which plays a crucial role in regulating Arr1 activity. InsPs bind to the N-domain basic patch thus displacing the C-tail, suggesting that they prime Arr1 for interaction with rhodopsin and help direct Arr1 translocation. These structures exhibit intact polar cores, suggesting that C-tail removal by InsP binding is insufficient to activate Arr1. These results show how Arr1 activity can be controlled by endogenous InsPs in molecular detail.
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Affiliation(s)
- Christopher L. Sander
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA,Department of Ophthalmology and the Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA
| | - Jennings Luu
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA,Department of Ophthalmology and the Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA
| | - Kyumhyuk Kim
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - David Furkert
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Kiyoung Jang
- Department of Lifestyle Medicine, Jeonbuk National University, Iksan 54596, Republic of Korea
| | | | - MinSoung Kang
- Department of Lifestyle Medicine, Jeonbuk National University, Iksan 54596, Republic of Korea,Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeong-ro, Daejeon 34114, Republic of Korea
| | - Ho-Jun Lee
- Department of Ophthalmology and the Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA,Research Service, VA Long Beach Healthcare System, Long Beach, CA 90822, USA
| | - Bryan T. Eger
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Hui-Woog Choe
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Oliver P. Ernst
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Yong Ju Kim
- Department of Lifestyle Medicine, Jeonbuk National University, Iksan 54596, Republic of Korea,Department of Oriental Medicine Resources, College of Environmental and Bioresource Sciences, Jeonbuk National University, Iksan 54596, Republic of Korea
| | - Krzysztof Palczewski
- Department of Ophthalmology and the Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA,Department of Chemistry and Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA,Department of Physiology & Biophysics, University of California, Irvine, CA 92697, USA
| | - Philip D. Kiser
- Department of Ophthalmology and the Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA,Department of Physiology & Biophysics, University of California, Irvine, CA 92697, USA,Research Service, VA Long Beach Healthcare System, Long Beach, CA 90822, USA,Lead contact
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Woo JA, Yan Y, Kee TR, Cazzaro S, McGill Percy KC, Wang X, Liu T, Liggett SB, Kang DE. β-arrestin1 promotes tauopathy by transducing GPCR signaling, disrupting microtubules and autophagy. Life Sci Alliance 2021; 5:5/3/e202101183. [PMID: 34862271 PMCID: PMC8675912 DOI: 10.26508/lsa.202101183] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 01/14/2023] Open
Abstract
GPCRs regulator, β-arrestin1, is increased in FTLD-tau patients, is required for β2-adrenergic receptor and metabotropic glutamate receptor 2-induced tau phosphorylation, promotes tau aggregation by impairing autophagy, and destabilizes microtubule dynamics, whereas genetic reduction in β-arrestin1 mitigates tauopathy and cognitive impairments. G protein–coupled receptors (GPCRs) have been shown to play integral roles in Alzheimer’s disease pathogenesis. However, it is unclear how diverse GPCRs similarly affect Aβ and tau pathogenesis. GPCRs share a common mechanism of action via the β-arrestin scaffolding signaling complexes, which not only serve to desensitize GPCRs by internalization, but also mediate multiple downstream signaling events. As signaling via the GPCRs, β2-adrenergic receptor (β2AR), and metabotropic glutamate receptor 2 (mGluR2) promotes hyperphosphorylation of tau, we hypothesized that β-arrestin1 represents a point of convergence for such pathogenic activities. Here, we report that β-arrestins are not only essential for β2AR and mGluR2-mediated increase in pathogenic tau but also show that β-arrestin1 levels are increased in brains of Frontotemporal lobar degeneration (FTLD-tau) patients. Increased β-arrestin1 in turn drives the accumulation of pathogenic tau, whereas reduced ARRB1 alleviates tauopathy and rescues impaired synaptic plasticity and cognitive impairments in PS19 mice. Biochemical and cellular studies show that β-arrestin1 drives tauopathy by destabilizing microtubules and impeding p62/SQSTM1 autophagy flux by interfering with p62 body formation, which promotes pathogenic tau accumulation.
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Affiliation(s)
- Jung-Aa Woo
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA
| | - Yan Yan
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA.,Department of Molecular Medicine, University of South Florida, College of Medicine, Tampa, FL, USA
| | - Teresa R Kee
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA.,Department of Molecular Medicine, University of South Florida, College of Medicine, Tampa, FL, USA
| | - Sara Cazzaro
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA.,Department of Molecular Medicine, University of South Florida, College of Medicine, Tampa, FL, USA
| | - Kyle C McGill Percy
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA
| | - Xinming Wang
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA
| | - Tian Liu
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA
| | - Stephen B Liggett
- Department of Molecular Pharmacology and Physiology, University of South Florida, College of Medicine, Tampa, FL, USA
| | - David E Kang
- Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, USA.,Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA
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3
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Aydin Y, Coin I. Biochemical insights into structure and function of arrestins. FEBS J 2021; 288:2529-2549. [DOI: 10.1111/febs.15811] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/26/2021] [Accepted: 03/09/2021] [Indexed: 12/13/2022]
Affiliation(s)
- Yasmin Aydin
- Institute of Biochemistry Faculty of Life Sciences University of Leipzig Germany
| | - Irene Coin
- Institute of Biochemistry Faculty of Life Sciences University of Leipzig Germany
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4
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Phosphorylated peptide of G protein-coupled receptor induces dimerization in activated arrestin. Sci Rep 2020; 10:10938. [PMID: 32616825 PMCID: PMC7331637 DOI: 10.1038/s41598-020-67944-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 06/16/2020] [Indexed: 11/08/2022] Open
Abstract
Termination of the G-protein-coupled receptor signaling involves phosphorylation of its C-terminus and subsequent binding of the regulatory protein arrestin. In the visual system, arrestin-1 preferentially binds to photoactivated and phosphorylated rhodopsin and inactivates phototransduction. Here, we have investigated binding of a synthetic phosphopeptide of bovine rhodopsin (residues 323-348) to the active variants of visual arrestin-1: splice variant p44, and the mutant R175E. Unlike the wild type arrestin-1, both these arrestins are monomeric in solution. Solution structure analysis using small angle X-ray scattering supported by size exclusion chromatography results reveal dimerization in both the arrestins in the presence of phosphopeptide. Our results are the first report, to our knowledge, on receptor-induced oligomerization in arrestin, suggesting possible roles for the cellular function of arrestin oligomers. Given high structural homology and the similarities in their activation mechanism, these results are expected to have implications for all arrestin isoforms.
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Woo JAA, Liu T, Fang CC, Castaño MA, Kee T, Yrigoin K, Yan Y, Cazzaro S, Matlack J, Wang X, Zhao X, Kang DE, Liggett SB. β-Arrestin2 oligomers impair the clearance of pathological tau and increase tau aggregates. Proc Natl Acad Sci U S A 2020; 117:5006-5015. [PMID: 32071246 PMCID: PMC7060747 DOI: 10.1073/pnas.1917194117] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multiple G protein-coupled receptors (GPCRs) are targets in the treatment of dementia, and the arrestins are common to their signaling. β-Arrestin2 was significantly increased in brains of patients with frontotemporal lobar degeneration (FTLD-tau), a disease second to Alzheimer's as a cause of dementia. Genetic loss and overexpression experiments using genetically encoded reporters and defined mutant constructs in vitro, and in cell lines, primary neurons, and tau P301S mice crossed with β-arrestin2-/- mice, show that β-arrestin2 stabilizes pathogenic tau and promotes tau aggregation. Cell and mouse models of FTLD showed this to be maladaptive, fueling a positive feedback cycle of enhanced neuronal tau via non-GPCR mechanisms. Genetic ablation of β-arrestin2 markedly ablates tau pathology and rescues synaptic plasticity defects in tau P301S transgenic mice. Atomic force microscopy and cellular studies revealed that oligomerized, but not monomeric, β-arrestin2 increases tau by inhibiting self-interaction of the autophagy cargo receptor p62/SQSTM1, impeding p62 autophagy flux. Hence, reduction of oligomerized β-arrestin2 with virus encoding β-arrestin2 mutants acting as dominant-negatives markedly reduces tau-laden neurofibrillary tangles in FTLD mice in vivo. Reducing β-arrestin2 oligomeric status represents a new strategy to alleviate tau pathology in FTLD and related tauopathies.
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Affiliation(s)
- Jung-A A Woo
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613;
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Tian Liu
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Cenxiao C Fang
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Maria A Castaño
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Teresa Kee
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Ksenia Yrigoin
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Yan Yan
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Sara Cazzaro
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Jenet Matlack
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Xinming Wang
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - Xingyu Zhao
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
| | - David E Kang
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613;
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Research Division, James A. Haley Veteran's Administration Hospital, Tampa, FL 33612
| | - Stephen B Liggett
- University of South Florida Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613;
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33613
- Department of Medical Engineering, University of South Florida, Tampa, FL 33613
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6
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Conformational Dynamics and Functional Implications of Phosphorylated β-Arrestins. Structure 2020; 28:314-323.e3. [DOI: 10.1016/j.str.2019.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/25/2019] [Accepted: 12/21/2019] [Indexed: 12/18/2022]
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Ostermaier MK, Schertler GFX, Standfuss J. Molecular mechanism of phosphorylation-dependent arrestin activation. Curr Opin Struct Biol 2014; 29:143-51. [PMID: 25484000 DOI: 10.1016/j.sbi.2014.07.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 07/16/2014] [Accepted: 07/18/2014] [Indexed: 12/31/2022]
Abstract
The past years have seen tremendous progress towards understanding how arrestins recognize phosphorylated G protein-coupled receptors (GPCRs). Two arrestin crystal structures, one of a pre-activated splice variant and one bound to a GPCR phosphopeptide, provided insights into the conformational changes upon phosphate recognition. Scanning mutagenesis and spectroscopic studies complete the picture of arrestin activation and receptor binding. Most perspicuous is the C-tail exchange mechanism, by which the C-tail of arrestin is released from its basal conformation and replaced by the phosphorylated GPCR C-terminus. Three positively charged clusters could act as conserved arrestin phosphosensors. Variations in the pattern of phosphorylation in a GPCR and variations within the C-terminus of different GPCRs may encode specificity to arrestin subtypes and particular physiological responses.
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Affiliation(s)
- Martin K Ostermaier
- Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Gebhard F X Schertler
- Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen, Switzerland; Deparment of Biology, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
| | - Joerg Standfuss
- Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen, Switzerland.
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Palczewski K. Chemistry and biology of the initial steps in vision: the Friedenwald lecture. Invest Ophthalmol Vis Sci 2014; 55:6651-72. [PMID: 25338686 DOI: 10.1167/iovs.14-15502] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Visual transduction is the process in the eye whereby absorption of light in the retina is translated into electrical signals that ultimately reach the brain. The first challenge presented by visual transduction is to understand its molecular basis. We know that maintenance of vision is a continuous process requiring the activation and subsequent restoration of a vitamin A-derived chromophore through a series of chemical reactions catalyzed by enzymes in the retina and retinal pigment epithelium (RPE). Diverse biochemical approaches that identified key proteins and reactions were essential to achieve a mechanistic understanding of these visual processes. The three-dimensional arrangements of these enzymes' polypeptide chains provide invaluable insights into their mechanisms of action. A wealth of information has already been obtained by solving high-resolution crystal structures of both rhodopsin and the retinoid isomerase from pigment RPE (RPE65). Rhodopsin, which is activated by photoisomerization of its 11-cis-retinylidene chromophore, is a prototypical member of a large family of membrane-bound proteins called G protein-coupled receptors (GPCRs). RPE65 is a retinoid isomerase critical for regeneration of the chromophore. Electron microscopy (EM) and atomic force microscopy have provided insights into how certain proteins are assembled to form much larger structures such as rod photoreceptor cell outer segment membranes. A second challenge of visual transduction is to use this knowledge to devise therapeutic approaches that can prevent or reverse conditions leading to blindness. Imaging modalities like optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) applied to appropriate animal models as well as human retinal imaging have been employed to characterize blinding diseases, monitor their progression, and evaluate the success of therapeutic agents. Lately two-photon (2-PO) imaging, together with biochemical assays, are revealing functional aspects of vision at a new molecular level. These multidisciplinary approaches combined with suitable animal models and inbred mutant species can be especially helpful in translating provocative cell and tissue culture findings into therapeutic options for further development in animals and eventually in humans. A host of different approaches and techniques is required for substantial progress in understanding fundamental properties of the visual system.
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Affiliation(s)
- Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States
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Abstract
G-protein-coupled receptors (GPCRs) are the primary interaction partners for arrestins. The visual arrestins, arrestin1 and arrestin4, physiologically bind to only very few receptors, i.e., rhodopsin and the color opsins, respectively. In contrast, the ubiquitously expressed nonvisual variants β-arrestin1 and 2 bind to a large number of receptors in a fairly nonspecific manner. This binding requires two triggers, agonist activation and receptor phosphorylation by a G-protein-coupled receptor kinase (GRK). These two triggers are mediated by two different regions of the arrestins, the "phosphorylation sensor" in the core of the protein and a less well-defined "activation sensor." Binding appears to occur mostly in a 1:1 stoichiometry, involving the N-terminal domain of GPCRs, but in addition a second GPCR may loosely bind to the C-terminal domain when active receptors are abundant.Arrestin binding initially uncouples GPCRs from their G-proteins. It stabilizes receptors in an active conformation and also induces a conformational change in the arrestins that involves a rotation of the two domains relative to each other plus changes in the polar core. This conformational change appears to permit the interaction with further downstream proteins. The latter interaction, demonstrated mostly for β-arrestins, triggers receptor internalization as well as a number of nonclassical signaling pathways.Open questions concern the exact stoichiometry of the interaction, possible specificity with regard to the type of agonist and of GRK involved, selective regulation of downstream signaling (=biased signaling), and the options to use these mechanisms as therapeutic targets.
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Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Straße 9, 97078, Würzburg, Germany,
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Smith WC. The role of arrestins in visual and disease processes of the eye. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:243-65. [PMID: 23764057 DOI: 10.1016/b978-0-12-394440-5.00010-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Visual arrestins are well known for their function in quenching the phototransduction process in rods and cones. Perhaps not as well known is their participation in multiple other processes in the normal and disease states of the eye. This chapter covers the range of the known functions of the visual arrestins, beginning with their classical role in quenching light-activated visual pigments. The role of visual arrestins is also reviewed from the perspective of their dynamic mobility whereby they redistribute significantly between the compartments of highly polarized photoreceptor cells. Additional roles of the visual arrestins are also reviewed based on new interacting partners that have been discovered over the past decade. Finally, the contribution of the visual arrestins to diseases of the visual system is explored.
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Affiliation(s)
- W Clay Smith
- Department of Ophthalmology, University of Florida, Gainesville, Florida, USA
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Granzin J, Cousin A, Weirauch M, Schlesinger R, Büldt G, Batra-Safferling R. Crystal structure of p44, a constitutively active splice variant of visual arrestin. J Mol Biol 2012; 416:611-8. [PMID: 22306737 DOI: 10.1016/j.jmb.2012.01.028] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 12/22/2011] [Accepted: 01/17/2012] [Indexed: 11/26/2022]
Abstract
Visual arrestin specifically binds to photoactivated and phosphorylated rhodopsin and inactivates phototransduction. In contrast, the p44 splice variant can terminate phototransduction by binding to nonphosphorylated light-activated rhodopsin. Here we report the crystal structure of bovine p44 at a resolution of 1.85 Å. Compared to native arrestin, the p44 structure reveals significant differences in regions crucial for receptor binding, namely flexible loop V-VI and polar core regions. Additionally, electrostatic potential is remarkably positive on the N-domain and the C-domain. The p44 structure represents an active conformation that serves as a model to explain the 'constitutive activity' found in arrestin variants.
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Affiliation(s)
- Joachim Granzin
- Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, 52425 Jülich, Germany
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Smith WC, Bolch S, Dugger DR, Li J, Esquenazi I, Arendt A, Benzenhafer D, McDowell JH. Interaction of arrestin with enolase1 in photoreceptors. Invest Ophthalmol Vis Sci 2011; 52:1832-40. [PMID: 21051714 DOI: 10.1167/iovs.10-5724] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Arrestin is in disequilibrium in photoreceptors, translocating between inner and outer segments in response to light. The purpose of this project was to identify the cellular component with which arrestin associates in the dark-adapted retina. METHODS Retinas were cross-linked with 2.5 mM dithiobis(succinimidylpropionate) (DSP), and arrestin-containing complexes purified by anion-exchange chromatography. Tandem mass spectrometric analysis was used to identify the protein components in the complex. Enolase localization in photoreceptors was assessed by immunohistochemistry. Confirmation of interacting components was performed using immunoprecipitation and surface plasmon resonance (SPR). Enolase activity was also assessed in the presence of arrestin1. RESULTS In retinas treated with DSP, arrestin cross-linked in a 125-kDa complex. The principal components of this complex were arrestin1 and enolase1. Both arrestin1 and -4 were pulled down with enolase1 when enolase1 was immunoprecipitated. In the dark-adapted retina, enolase1 co-localized with arrestin1 in the inner segments and outer nuclear layer, but remained in the inner segments when arrestin1 translocated in response to light adaptation. SPR of purified arrestin1 and enolase1 demonstrated direct binding between arrestin1 and enolase1. Arrestin1 modulated the catalytic activity of enolase1, slowing it by as much as 24%. CONCLUSIONS The results show that in the dark-adapted retina, arrestin1 and -4 interact with enolase1. The SPR data show that the interaction between arrestin1 and enolase1 was direct, not requiring a third element to form the complex. Arrestin1 slowed the catalytic activity of enolase1, suggesting that light-driven translocation of arrestin1 may modulate the metabolic activity of photoreceptors.
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Affiliation(s)
- W Clay Smith
- Department of Ophthalmology, University of Florida, Gainesville, FL 32610-0284, USA.
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Caruso G, Bisegna P, Lenoci L, Andreucci D, Gurevich VV, Hamm HE, DiBenedetto E. Kinetics of rhodopsin deactivation and its role in regulating recovery and reproducibility of rod photoresponse. PLoS Comput Biol 2010; 6:e1001031. [PMID: 21200415 PMCID: PMC3002991 DOI: 10.1371/journal.pcbi.1001031] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 11/11/2010] [Indexed: 12/31/2022] Open
Abstract
The single photon response (SPR) in vertebrate phototransduction is regulated by the dynamics of R* during its lifetime, including the random number of phosphorylations, the catalytic activity and the random sojourn time at each phosphorylation level. Because of this randomness the electrical responses are expected to be inherently variable. However the SPR is highly reproducible. The mechanisms that confer to the SPR such a low variability are not completely understood. The kinetics of rhodopsin deactivation is investigated by a Continuous Time Markov Chain (CTMC) based on the biochemistry of rhodopsin activation and deactivation, interfaced with a spatio-temporal model of phototransduction. The model parameters are extracted from the photoresponse data of both wild type and mutant mice, having variable numbers of phosphorylation sites and, with the same set of parameters, the model reproduces both WT and mutant responses. The sources of variability are dissected into its components, by asking whether a random number of turnoff steps, a random sojourn time between steps, or both, give rise to the known variability. The model shows that only the randomness of the sojourn times in each of the phosphorylated states contributes to the Coefficient of Variation (CV) of the response, whereas the randomness of the number of R* turnoff steps has a negligible effect. These results counter the view that the larger the number of decay steps of R*, the more stable the photoresponse is. Our results indicate that R* shutoff is responsible for the variability of the photoresponse, while the diffusion of the second messengers acts as a variability suppressor.
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Affiliation(s)
- Giovanni Caruso
- Construction Technologies Institute, National Research Council, Rome, Italy
| | - Paolo Bisegna
- Department of Civil Engineering, University of Rome Tor Vergata, Rome, Italy
| | - Leonardo Lenoci
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Daniele Andreucci
- Department of Mathematical Methods and Models, University of Rome La Sapienza, Rome, Italy
| | - Vsevolod V. Gurevich
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Heidi E. Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Emmanuele DiBenedetto
- Department of Mathematics, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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15
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Burns ME. Deactivation mechanisms of rod phototransduction: the Cogan lecture. Invest Ophthalmol Vis Sci 2010; 51:1282-8. [PMID: 20185839 DOI: 10.1167/iovs.09-4366] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The absorption of photons in rods and cones of the retina activate homologous biochemical signaling cascades that lead to the electrical changes that subserve the first steps in vision. Persistent activity of the cascade interferes with the ability of the photoreceptor to signal the absorption of subsequent photons, ultimately limiting the photoreceptor's sensitivity and temporal resolution. This article summarizes recent work on transgenic and knockout mouse rods that has revealed the deactivation mechanisms essential for normal response recovery and how each of these processes contributes to the overall time course of the flash response of rods.
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Affiliation(s)
- Marie E Burns
- Department of Ophthalmology and Vision Science and Center for Neuroscience, University of California, Davis, California, USA
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16
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Codega P, Della Santina L, Gargini C, Bedolla DE, Subkhankulova T, Livesey FJ, Cervetto L, Torre V. Prolonged illumination up-regulates arrestin and two guanylate cyclase activating proteins: a novel mechanism for light adaptation. J Physiol 2009; 587:2457-72. [PMID: 19332500 DOI: 10.1113/jphysiol.2009.168609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Light adaptation in vertebrate photoreceptors is mediated by multiple mechanisms, one of which could involve nuclear feedback and changes in gene expression. Therefore, we have investigated light adaptation-associated changes in gene expression using microarrays and real-time PCR in isolated photoreceptors, in cultured isolated retinas and in acutely isolated retinas. In all three preparations after 2 h of an exposure to a bright light, we observed an up-regulation of almost 100% of three genes, Sag, Guca1a and Guca1b, coding for proteins known to play a major role in phototransduction: arrestin, GCAP1 and GCAP2. No detectable up-regulation occurred for light exposures of less than 1 h. Functional in vivo electroretinographic tests show that a partial recovery of the dark current occurred 1-2 h after prolonged illumination with a steady light that initially caused a substantial suppression of the photoresponse. These observations demonstrate that prolonged illumination results in the up-regulation of genes coding for proteins involved in the phototransduction signalling cascade, possibly underlying a novel component of light adaptation occurring 1-2 h after the onset of a steady bright light.
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Affiliation(s)
- Paolo Codega
- International School for Advanced Studies (SISSA), Trieste, Italy
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17
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Swaney DL, McAlister GC, Coon JJ. Decision tree-driven tandem mass spectrometry for shotgun proteomics. Nat Methods 2008; 5:959-64. [PMID: 18931669 DOI: 10.1038/nmeth.1260] [Citation(s) in RCA: 258] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 09/10/2008] [Indexed: 11/09/2022]
Abstract
Mass spectrometry has become a key technology for modern large-scale protein sequencing. Tandem mass spectrometry, the process of peptide ion dissociation followed by mass-to-charge ratio (m/z) analysis, is the critical component for peptide identification. Recent advances in mass spectrometry now permit two discrete, and complementary, types of peptide ion fragmentation: collision-activated dissociation (CAD) and electron transfer dissociation (ETD) on a single instrument. To exploit this complementarity and increase sequencing success rates, we designed and embedded a data-dependent decision tree algorithm (DT) to make unsupervised, real-time decisions of which fragmentation method to use based on precursor charge and m/z. Applying the DT to large-scale proteome analyses of Saccharomyces cerevisiae and human embryonic stem cells, we identified 53,055 peptides in total, which was greater than by using CAD (38,293) or ETD (39,507) alone. In addition, the DT method also identified 7,422 phosphopeptides, compared to either 2,801 (CAD) or 5,874 (ETD) phosphopeptides.
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Affiliation(s)
- Danielle L Swaney
- Department of Chemistry, 1101 University Avenue, University of Wisconsin, Madison, Wisconsin 53706, USA
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18
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Hanson SM, Dawson ES, Francis DJ, Van Eps N, Klug CS, Hubbell WL, Meiler J, Gurevich VV. A model for the solution structure of the rod arrestin tetramer. Structure 2008; 16:924-34. [PMID: 18547524 DOI: 10.1016/j.str.2008.03.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 03/03/2008] [Accepted: 03/04/2008] [Indexed: 10/22/2022]
Abstract
Visual rod arrestin has the ability to self-associate at physiological concentrations. We previously demonstrated that only monomeric arrestin can bind the receptor and that the arrestin tetramer in solution differs from that in the crystal. We employed the Rosetta docking software to generate molecular models of the physiologically relevant solution tetramer based on the monomeric arrestin crystal structure. The resulting models were filtered using the Rosetta energy function, experimental intersubunit distances measured with DEER spectroscopy, and intersubunit contact sites identified by mutagenesis and site-directed spin labeling. This resulted in a unique model for subsequent evaluation. The validity of the model is strongly supported by model-directed crosslinking and targeted mutagenesis that yields arrestin variants deficient in self-association. The structure of the solution tetramer explains its inability to bind rhodopsin and paves the way for experimental studies of the physiological role of rod arrestin self-association.
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Affiliation(s)
- Susan M Hanson
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
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19
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Lee C, Bhatt S, Shukla A, Desnoyer RW, Yadav SP, Kim M, Jang SH, Karnik SS. Site-specific cleavage of G protein-coupled receptor-engaged beta-arrestin. Influence of the AT1 receptor conformation on scissile site selection. J Biol Chem 2008; 283:21612-20. [PMID: 18505723 PMCID: PMC2490789 DOI: 10.1074/jbc.m803062200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 05/21/2008] [Indexed: 01/14/2023] Open
Abstract
The discovery of beta-arrestin-related approximately 46-kDa polypeptide in transfected cells and mouse hearts led us to examine angiotensin II type 1 receptor (AT(1)R)-dependent proteolytic cleavage of beta-arrestin(s). Receptor-ligand induced proteolysis of beta-arrestin(s) is novel, especially in the endocrine system, since proteolytic and/or splice variants of nonvisual arrestins are unknown. We used a strategy to retrieve AT(1)R-engaged isoforms of beta-arrestin 1 to confirm direct interaction of fragments with this G protein-coupled receptor and determine cleavage sites. Here we show that the angiotensin II-AT(1)R complex is associated with full-length and approximately 46-kDa beta-arrestin forms. Mass spectrometric analysis of the AT(1)R-associated short form suggested a scissile site located within the Arg(363)-Arg(393) region in the bovine beta-arrestin 1. Edman degradation analysis of a beta-arrestin 1 C-terminal fragment fused to enhanced green fluorescent protein confirmed the major cleavage to be after Phe(388) and a minor cleavage after Asn(375). Rather unexpectedly, the inverse agonist EXP3174-bound AT(1)R generated different fragmentation of bovine beta-arrestin 1, at Pro(276). The angiotensin II-induced cleavage is independent of inositol 1,4,5-trisphosphate- and Ca(2+)-mediated signaling pathways. The proteolysis of beta-arrestin 2 occurs, but the pattern is more complex. Our findings suggest that beta-arrestin cleavage upon AT(1)R stimulation is a part of the unraveling beta-arrestin-mediated G protein-coupled receptor signaling diversity.
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Affiliation(s)
- ChangWoo Lee
- Department of Molecular Cardiology and Molecular Biotechnology Core, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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20
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Sommer ME, Farrens DL, McDowell JH, Weber LA, Smith WC. Dynamics of arrestin-rhodopsin interactions: loop movement is involved in arrestin activation and receptor binding. J Biol Chem 2007; 282:25560-8. [PMID: 17606620 DOI: 10.1074/jbc.m702155200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study we investigate conformational changes in Loop V-VI of visual arrestin during binding to light-activated, phosphorylated rhodopsin (Rho*-P) using a combination of site-specific cysteine mutagenesis and intramolecular fluorescence quenching. Introduction of cysteines at positions in the N-domain at residues predicted to be in close proximity to Ile-72 in Loop V-VI of arrestin (i.e. Glu-148 and Lys-298) appear to form an intramolecular disulfide bond with I72C, significantly diminishing the binding of arrestin to Rho*-P. Using a fluorescence approach, we show that the steady-state emission from a monobromobimane fluorophore in Loop V-VI is quenched by tryptophan residues placed at 148 or 298. This quenching is relieved upon binding of arrestin to Rho*-P. These results suggest that arrestin Loop V-VI moves during binding to Rho*-P and that conformational flexibility of this loop is essential for arrestin to adopt a high affinity binding state.
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Affiliation(s)
- Martha E Sommer
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239-3098, USA
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21
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Oliveira L, Costa-Neto CM, Nakaie CR, Schreier S, Shimuta SI, Paiva ACM. The Angiotensin II AT1 Receptor Structure-Activity Correlations in the Light of Rhodopsin Structure. Physiol Rev 2007; 87:565-92. [PMID: 17429042 DOI: 10.1152/physrev.00040.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The most prevalent physiological effects of ANG II, the main product of the renin-angiotensin system, are mediated by the AT1 receptor, a rhodopsin-like AGPCR. Numerous studies of the cardiovascular effects of synthetic peptide analogs allowed a detailed mapping of ANG II's structural requirements for receptor binding and activation, which were complemented by site-directed mutagenesis studies on the AT1 receptor to investigate the role of its structure in ligand binding, signal transduction, phosphorylation, binding to arrestins, internalization, desensitization, tachyphylaxis, and other properties. The knowledge of the high-resolution structure of rhodopsin allowed homology modeling of the AT1 receptor. The models thus built and mutagenesis data indicate that physiological (agonist binding) or constitutive (mutated receptor) activation may involve different degrees of expansion of the receptor's central cavity. Residues in ANG II structure seem to control these conformational changes and to dictate the type of cytosolic event elicited during the activation. 1) Agonist aromatic residues (Phe8 and Tyr4) favor the coupling to G protein, and 2) absence of these residues can favor a mechanism leading directly to receptor internalization via phosphorylation by specific kinases of the receptor's COOH-terminal Ser and Thr residues, arrestin binding, and clathrin-dependent coated-pit vesicles. On the other hand, the NH2-terminal residues of the agonists ANG II and [Sar1]-ANG II were found to bind by two distinct modes to the AT1 receptor extracellular site flanked by the COOH-terminal segments of the EC-3 loop and the NH2-terminal domain. Since the [Sar1]-ligand is the most potent molecule to trigger tachyphylaxis in AT1 receptors, it was suggested that its corresponding binding mode might be associated with this special condition of receptors.
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Affiliation(s)
- Laerte Oliveira
- Department of Biophysics, Escola Paulista de Medicina, Federal University of São Paulo, Brazil.
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22
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Abstract
Phototransduction is the process by which light triggers an electrical signal in a photoreceptor cell. Image-forming vision in vertebrates is mediated by two types of photoreceptors: the rods and the cones. In this review, we provide a summary of the success in which the mouse has served as a vertebrate model for studying rod phototransduction, with respect to both the activation and termination steps. Cones are still not as well-understood as rods partly because it is difficult to work with mouse cones due to their scarcity and fragility. The situation may change, however.
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Affiliation(s)
- Yingbin Fu
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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23
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Chen J, Shi G, Concepcion FA, Xie G, Oprian D, Chen J. Stable rhodopsin/arrestin complex leads to retinal degeneration in a transgenic mouse model of autosomal dominant retinitis pigmentosa. J Neurosci 2006; 26:11929-37. [PMID: 17108167 PMCID: PMC6674877 DOI: 10.1523/jneurosci.3212-06.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Over 100 rhodopsin mutation alleles have been associated with autosomal dominant retinitis pigmentosa (ADRP). These mutations appear to cause photoreceptor cell death through diverse molecular mechanisms. We show that K296E, a rhodopsin mutation associated with ADRP, forms a stable complex with arrestin that is toxic to mouse rod photoreceptors. This cell death pathway appears to be conserved from flies to mammals. A genetics approach to eliminate arrestin unmasked the constitutive activity of K296E and caused photoreceptor cell death through a transducin-dependent mechanism that is similar to light damage. Expressing K296E in the arrestin/transducin double knock-out background prevented transducin signaling and led to substantially improved retinal morphology but did not fully prevent cell death caused by K296E. The adverse effect of K296E in the arrestin/transducin knock-out background can be mimicked by constant exposure to low light. Furthermore, we found that arrestin binding causes K296E to mislocalize to the wrong cellular compartment. Accumulation of stable rhodopsin/arrestin complex in the inner segment may be an important mechanism for triggering the cell death pathway in the mammalian photoreceptor cell.
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Affiliation(s)
- Jiayan Chen
- Zilkha Neurogenetic Institute
- Neuroscience Graduate Program, and
| | | | - Francis A. Concepcion
- Zilkha Neurogenetic Institute
- Department of Cell and Neurobiology and Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, and
| | - Guifu Xie
- Department of Biochemistry and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02545
| | - Daniel Oprian
- Department of Biochemistry and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02545
| | - Jeannie Chen
- Zilkha Neurogenetic Institute
- Neuroscience Graduate Program, and
- Department of Cell and Neurobiology and Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, and
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24
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Sommer ME, Farrens DL. Arrestin can act as a regulator of rhodopsin photochemistry. Vision Res 2006; 46:4532-46. [PMID: 17069872 PMCID: PMC2877124 DOI: 10.1016/j.visres.2006.08.031] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 08/11/2006] [Accepted: 08/16/2006] [Indexed: 11/24/2022]
Abstract
We report that visual arrestin can regulate retinal release and late photoproduct formation in rhodopsin. Our experiments, which employ a fluorescently labeled arrestin and rhodopsin solubilized in detergent/phospholipid micelles, indicate that arrestin can trap a population of retinal in the binding pocket with an absorbance characteristic of Meta II with the retinal Schiff-base intact. Furthermore, arrestin can convert Metarhodopsin III (formed either by thermal decay or blue-light irradiation) to a Meta II-like absorbing species. Together, our results suggest arrestin may be able to play a more complex role in the rod cell besides simply quenching transducin activity. This possibility may help explain why arrestin deficiency leads to problems like stationary night blindness (Oguchi disease) and retinal degeneration.
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Affiliation(s)
| | - David L. Farrens
- Corresponding author. Fax: +1 503 494 8393. E-mail address: (D.L. Farrens)
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25
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Rózanowska M, Sarna T. Light-induced damage to the retina: role of rhodopsin chromophore revisited. Photochem Photobiol 2006; 81:1305-30. [PMID: 16120006 DOI: 10.1562/2004-11-13-ir-371] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The presence of the regenerable visual pigment rhodopsin has been shown to be primarily responsible for the acute photodamage to the retina. The photoexcitation of rhodopsin leads to isomerization of its chromophore 11-cis-retinal to all-trans-retinal (ATR). ATR is a potent photosensitizer and its role in mediating photodamage has been suspected for over two decades. However, there was lack of experimental evidence that free ATR exists in the retina in sufficient concentrations to impose a risk of photosensitized damage. Identification in the retina of a retinal dimer and a pyridinium bisretinoid, so called A2E, and determination of its biosynthetic pathway indicate that substantial amounts of ATR do accumulate in the retina. Both light damage and A2E accumulation are facilitated under conditions where efficient retinoid cycle operates. Efficient retinoid cycle leads to rapid regeneration of rhodopsin, which may result in ATR release from the opsin "exit site" before its enzymatic reduction to all-trans-retinol. Here we discuss photodamage to the retina where ATR could play a role as the main toxic and/or phototoxic agent. Moreover, we discuss secondary products of (photo)toxic properties accumulating within retinal lipofuscin as a result of ATR accumulation.
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26
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Burns ME, Mendez A, Chen CK, Almuete A, Quillinan N, Simon MI, Baylor DA, Chen J. Deactivation of phosphorylated and nonphosphorylated rhodopsin by arrestin splice variants. J Neurosci 2006; 26:1036-44. [PMID: 16421323 PMCID: PMC6675359 DOI: 10.1523/jneurosci.3301-05.2006] [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: 11/21/2022] Open
Abstract
Arrestins constitute a family of small cytoplasmic proteins that mediate deactivation of G-protein-coupled receptors (GPCRs) and are known to be essential for cascade inactivation and receptor desensitization. Alternative splicing produces an array of arrestin gene products that have widely different specificities for their cognate receptors in vitro, but the differential functions of these splice variants in vivo are essentially unknown. Bovine rod photoreceptors express two splice variants of visual arrestin (p44 and p48) that display different affinities for the GPCR rhodopsin. To determine the functions of these splice variants in intact cells, we expressed a transgene encoding either a truncated form of murine arrestin (mArr(1-369), or m44) or the long (p48) isoform in mouse rods lacking endogenous arrestin (Arr-/-). Morphological analysis showed that expression of either variant attenuated the light-induced degeneration that is thought to result from excessive cascade activity in Arr-/-rods. Suction electrode recordings from individual rods indicated that the expression of either m44 or p48 splice variants could restore normal kinetics to Arr-/- dim flash responses, indicating that both isoforms can bind to and quench phosphorylated rhodopsin rapidly. To our surprise, only the full-length variant was able to alter the kinetics of responses in rods lacking both arrestin and rhodopsin kinase, indicating that p48 can also quench the activity of nonphosphorylated rhodopsin.
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Affiliation(s)
- Marie E Burns
- Center for Neuroscience, Department of Psychiatry and Behavioral Sciences, University of California, Davis, California 95616, USA.
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27
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Avidan H, Kipnis J, Butovsky O, Caspi RR, Schwartz M. Vaccination with autoantigen protects against aggregated beta-amyloid and glutamate toxicity by controlling microglia: effect of CD4+CD25+ T cells. Eur J Immunol 2005; 34:3434-45. [PMID: 15549735 DOI: 10.1002/eji.200424883] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neurodegenerative diseases differ in etiology but are propagated similarly. We show that neuronal loss caused by intraocular injection of aggregated beta-amyloid was significantly greater in immunodeficient mice than in normal mice. The neurodegeneration was attenuated or augmented by elimination or addition, respectively, of naturally occurring CD4(+)CD25(+) regulatory T cells (Treg). Vaccination with retina-derived antigens or with the synthetic copolymer glatiramer acetate (Copolymer-1, Cop-1), but not with beta-amyloid, reduced the ocular neuronal loss. In mouse hippocampal slices, microglia encountering activated T cells overcame the cytotoxicity of aggregated beta-amyloid. These findings support the concept of "protective autoimmunity", show that a given T cell-based vaccination is protective at a particular site irrespective of toxicity type, and suggest that locally activated T cells induce a microglial phenotype that helps neurons withstand the insult. Alzheimer's and other neurodegenerative diseases might be arrested or retarded by vaccination with Cop-1 or related compounds or by treatment with compounds that weaken Treg suppression.
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Affiliation(s)
- Hila Avidan
- Department of Neurobiology, The Weizmann Institute of Science, Rehovot, Israel
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28
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Schröder K, Pulvermüller A, Hofmann KP. Arrestin and its splice variant Arr1-370A (p44). Mechanism and biological role of their interaction with rhodopsin. J Biol Chem 2002; 277:43987-96. [PMID: 12194979 DOI: 10.1074/jbc.m206211200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Deactivation of G-protein-coupled receptors relies on a timely blockade by arrestin. However, under dim light conditions, virtually all arrestin is in the rod inner segment, and the splice variant p(44) (Arr(1-370A)) is the stop protein responsible for receptor deactivation. Using size exclusion chromatography and biophysical assays for membrane-bound protein-protein interaction, membrane binding, and G-protein activation, we have investigated the interactions of Arr(1-370A) and proteolytically truncated Arr(3-367) with rhodopsin. We find that these short arrestins do not only interact with the phosphorylated active receptor but also with inactive phosphorylated rhodopsin or opsin in membranes or solution. Because of the latter interaction they are not soluble (like arrestin) but membrane-bound in the dark. Upon photoexcitation, Arr(3-367) and Arr(1-370A) interact with prephosphorylated rhodopsin faster than arrestin and start to quench G(t) activation on a subsecond time scale. The data indicate that in the course of rhodopsin deactivation, Arr(1-370A) is handed over from inactive to active phosphorylated rhodopsin. This mechanism could provide a new aspect of receptor shutoff in the single photon operating range of the rod cell.
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Affiliation(s)
- Katrin Schröder
- Institut für Medizinische Physik und Biophysik, Humboldt-Universität zu Berlin, Universitätsklinikum Charité, Schumannstrasse 20-21, Germany
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29
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Nakagawa M, Orii H, Yoshida N, Jojima E, Horie T, Yoshida R, Haga T, Tsuda M. Ascidian arrestin (Ci-arr), the origin of the visual and nonvisual arrestins of vertebrate. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5112-8. [PMID: 12392543 DOI: 10.1046/j.1432-1033.2002.03240.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Arrestin is one of the key proteins for the termination of G protein signaling. Activated G protein-coupled receptors (GPCRs) are specifically phosphorylated by G protein-coupled receptor kinases (GRKs) and then bind to arrestins to preclude the receptor/G protein interaction, resulting in quenching of the following signal transduction. Vertebrates possess two types of arrestin; visual arrestin expressed exclusively in photoreceptor cells in retinae and pineal organs, and beta-arrestin, which is expressed ubiquitously. Unlike visual arrestin, beta-arrestin contains the clathrin-binding domain at the C-terminus, responsible for the agonist-induced internalization of GPCRs. Here, we isolated a novel arrestin gene (Ci-arr) from the primitive chordate, the ascidian Ciona intestinalis larvae. The deduced amino acid sequence suggests that Ci-Arr be closely related to vertebrate arrestins. Interestingly, this arrestin has the feature of both visual and beta-arrestin. Whereas the expression of Ci-arr was restricted to the photoreceptors in the larvae similarly to visual arrestin, the gene product, containing the clathrin-binding domain, promoted the GPCR internalization in HEK293tsA201 cells similarly to beta-arrestin. The phylogenetic tree shows that Ci-Arr is branched from a common root of visual and beta-arrestins. Southern analysis suggests that the Ciona genome contains only one gene for the arrestin family. These results suggest that the visual and beta-arrestin genes were generated by the duplication of the prototypical arrestin gene like Ci-arr in the early evolution of vertebrates.
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Affiliation(s)
- Masashi Nakagawa
- Department of Life Science, Graduate School of Science, Himeji Institute of Technology, Kamigori, Akoh-Gun, Hyogo, Japan.
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30
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Pao CS, Benovic JL. Phosphorylation-independent desensitization of G protein-coupled receptors? SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2002; 2002:pe42. [PMID: 12372852 DOI: 10.1126/stke.2002.153.pe42] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
G protein-coupled receptors (GPCRs) are involved in a multitude of signaling processes and respond to a wide range of ligands. The activity of GPCRs is subject to three principal modes of regulation: desensitization, trafficking, and down-regulation. Desensitization is defined as a loss in the responsiveness of a signaling system. The generally established paradigm for GPCR desensitization involves receptor phosphorylation by GPCR kinases (GRKs), initiated by agonist-induced conformational changes in the receptor or by kinases activated by specific signaling pathways. GRKs have several interaction domains and may be able to contribute to receptor desensitization through mechanisms that do not involve the kinase activity of GRK. Pao and Benovic discuss some of these interactions and their relevance for the regulation of GPCR signaling.
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Affiliation(s)
- Christina S Pao
- The Kimmel Cancer Center, Department of Microbiology and Immunology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
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31
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Abstract
G protein-coupled receptors are a large family of signaling molecules that respond to a wide variety of extracellular stimuli. The receptors relay the information encoded by the ligand through the activation of heterotrimeric G proteins and intracellular effector molecules. To ensure the appropriate regulation of the signaling cascade, it is vital to properly inactivate the receptor. This inactivation is achieved, in part, by the binding of a soluble protein, arrestin, which uncouples the receptor from the downstream G protein. In addition to the inactivation of G protein-coupled receptors, arrestins have also been implicated in the endocytosis of receptors and cross talk with other signaling pathways. Due to its central role in cellular signaling, misregulation or misfunction of arrestin can have dramatic affects on cell viability and have direct implications in human disease.
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Affiliation(s)
- Patrick J Dolph
- Department of Biological Sciences, Dartmouth College, 6044 Gilman, Hanover, NH 03755, USA.
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32
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Dinculescu A, McDowell JH, Amici SA, Dugger DR, Richards N, Hargrave PA, Smith WC. Insertional mutagenesis and immunochemical analysis of visual arrestin interaction with rhodopsin. J Biol Chem 2002; 277:11703-8. [PMID: 11809770 DOI: 10.1074/jbc.m111833200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Visual arrestin inactivates the phototransduction cascade by specifically binding to light-activated phosphorylated rhodopsin. This study describes the combined use of insertional mutagenesis and immunochemical approaches to probe the structural determinants of arrestin function. Recombinant arrestins with insertions of a 10-amino acid c-Myc tag (EQKLISEEDL) were expressed in yeast and characterized. When the tag was placed on the C terminus after amino acid 399, between amino acids 99 and 100 or between residues 162 and 163, binding to rhodopsin was found to be very similar to that of wild-type arrestin. Two stable mutants with Myc insertions in the 68-78 loop were also generated. Binding to rhodopsin was markedly decreased for one (72myc73) and completely abolished for the other (77myc78). Limited proteolysis assays using trypsin in the absence or presence of heparin were performed on all mutants and confirmed their overall conformational integrity. Rhodopsin binding to either 162myc163 or 72myc73 arrestins in solution was completely inhibited in the presence of less than a 2-fold molar excess of anti-Myc antibody relative to arrestin. In contrast, the antibody did not block the interaction of the 399myc or 99myc100 arrestins with rhodopsin. These results indicate that an interactive surface for rhodopsin is located on or near the concave region of the N-domain of arrestin.
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Affiliation(s)
- Astra Dinculescu
- Department of Ophthalmology, University of Florida, Gainesville, Florida 32610-0284, USA
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33
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Affiliation(s)
- Izabela Sokal
- Department of Ophthalmology, University of Washington, Seattle, Washington 98195, USA
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Carr SA, Annan RS. Overview of Peptide and Protein Analysis by Mass Spectrometry. ACTA ACUST UNITED AC 2001; Chapter 10:Unit 10.21. [DOI: 10.1002/0471142727.mb1021s38] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Steven A. Carr
- SmithKline Beecham Pharmaceuticals King of Prussia Pennsylvania
| | - Roland S. Annan
- SmithKline Beecham Pharmaceuticals King of Prussia Pennsylvania
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35
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Abstract
The basis of the duplex theory of vision is examined in view of the dazzling array of data on visual pigment sequences and the pigments they form, on the microspectrophotometry measurements of single photoreceptor cells, on the kinds of photoreceptor cascade enzymes, and on the electrophysiological properties of photoreceptors. The implications of the existence of five distinct visual pigment families are explored, especially with regard to what pigments are in what types of photoreceptors, if there are different phototransduction enzymes associated with different types of photoreceptors, and if there are electrophysiological differences between different types of cones.
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Affiliation(s)
- T Ebrey
- University of Washington, Seattle 98195, USA
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36
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Pulvermüller A, Schroder K, Fischer T, Hofmann KP. Interactions of metarhodopsin II. Arrestin peptides compete with arrestin and transducin. J Biol Chem 2000; 275:37679-85. [PMID: 10969086 DOI: 10.1074/jbc.m006776200] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arrestin blocks the interaction of rhodopsin with the G protein transducin (G(t)). To characterize the sites of arrestin that interact with rhodopsin, we have utilized a spectrophotometric peptide competition assay. It is based on the stabilization of the active intermediates metarhodopsin II (MII) and phosphorylated MII by G(t) and arrestin, respectively (extra MII monitor). The protocol involves native disc membranes and three sets of peptides 10-30 amino acids in length spanning the arrestin sequence. In the absence of arrestin, not one of the peptides by itself had an effect on the amount of MII formed. However, inhibition of arrestin-dependent extra MII was found for the peptides at residues 11-30 and 51-70 (IC(50) < 100 microm) and residues 231-260 (IC(50) < 200 microm). A similar pattern of inhibition by arrestin peptides was seen when arrestin was replaced by G(t) or the farnesylated G(t)gamma C-terminal peptide. Only arrestin-(11-30) inhibited MII.G(t) less (IC(50) = 300 microm) than phosphorylated MII.arrestin. We interpreted the data by competition of the arrestin peptides for interaction sites at rhodopsin, exposed in the MII conformation and specific for both arrestin and G(t). The arrestin sites are located in both the C- and N-terminal domains of the arrestin structure.
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Affiliation(s)
- A Pulvermüller
- Institut für Medizinische Physik und Biophysik, Humboldt-Universität zu Berlin, Universitätsklinikum Charité, Schumannstrasse 20-21, 10098 Berlin, Germany.
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37
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Mendez A, Burns ME, Roca A, Lem J, Wu LW, Simon MI, Baylor DA, Chen J. Rapid and reproducible deactivation of rhodopsin requires multiple phosphorylation sites. Neuron 2000; 28:153-64. [PMID: 11086991 DOI: 10.1016/s0896-6273(00)00093-3] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Efficient single-photon detection by retinal rod photoreceptors requires timely and reproducible deactivation of rhodopsin. Like other G protein-coupled receptors, rhodopsin contains multiple sites for phosphorylation at its COOH-terminal domain. Transgenic and electrophysiological methods were used to functionally dissect the role of the multiple phosphorylation sites during deactivation of rhodopsin in intact mouse rods. Mutant rhodopsins bearing zero, one (S338), or two (S334/S338) phosphorylation sites generated single-photon responses with greatly prolonged, exponentially distributed durations. Responses from rods expressing mutant rhodopsins bearing more than two phosphorylation sites declined along smooth, reproducible time courses; the rate of recovery increased with increasing numbers of phosphorylation sites. We conclude that multiple phosphorylation of rhodopsin is necessary for rapid and reproducible deactivation.
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Affiliation(s)
- A Mendez
- Department of Ophthalmology and Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles 90089, USA
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38
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Chapter 3 Late photoproducts and signaling states of bovine rhodopsin. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1383-8121(00)80006-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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39
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Schubert C, Hirsch JA, Gurevich VV, Engelman DM, Sigler PB, Fleming KG. Visual arrestin activity may be regulated by self-association. J Biol Chem 1999; 274:21186-90. [PMID: 10409673 DOI: 10.1074/jbc.274.30.21186] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Visual arrestin is the protein responsible for rapid quenching of G-protein-coupled receptor signaling. Arrestin exists as a latent inhibitor which must be 'activated' upon contact with a phosphorylated receptor. X-ray crystal structures of visual arrestin exhibit a tetrameric arrangement wherein an asymmetric dimer with an extensive interface between conformationally different subunits is related to a second asymmetric dimer by a local two-fold rotation axis. To test the biological relevance of this molecular organization in solution, we carried out a sedimentation equilibrium analysis of arrestin at both crystallographic and physiological protein concentrations. While the tetrameric form can exist at the high concentrations used in crystallography experiments, we find that arrestin participates in a monomer/dimer equilibrium at concentrations more likely to be physiologically relevant. Solution interaction analysis of a proteolytically modified, constitutively active form of arrestin shows diminished dimerization. We propose that self-association of arrestin may provide a mechanism for regulation of arrestin activity by (i) ensuring an adequate supply for rapid quenching of the visual signal and (ii) limiting the availability of active monomeric species, thereby preventing inappropriate signal termination.
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Affiliation(s)
- C Schubert
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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40
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Hirsch JA, Schubert C, Gurevich VV, Sigler PB. The 2.8 A crystal structure of visual arrestin: a model for arrestin's regulation. Cell 1999; 97:257-69. [PMID: 10219246 DOI: 10.1016/s0092-8674(00)80735-7] [Citation(s) in RCA: 329] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
G protein-coupled signaling is utilized by a wide variety of eukaryotes for communicating information from the extracellular environment. Signal termination is achieved by the action of the arrestins, which bind to activated, phosphorylated G protein-coupled receptors. We describe here crystallographic studies of visual arrestin in its basal conformation. The salient features of the structure are a bipartite molecule with an unusual polar core. This core is stabilized in part by an extended carboxy-terminal tail that locks the molecule into an inactive state. In addition, arrestin is found to be a dimer of two asymmetric molecules, suggesting an intrinsic conformational plasticity. In conjunction with biochemical and mutagenesis data, we propose a molecular mechanism by which arrestin is activated for receptor binding.
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Affiliation(s)
- J A Hirsch
- Howard Hughes Medical Institute, Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA
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41
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Saari JC, Garwin GG, Van Hooser JP, Palczewski K. Reduction of all-trans-retinal limits regeneration of visual pigment in mice. Vision Res 1998; 38:1325-33. [PMID: 9667000 DOI: 10.1016/s0042-6989(97)00198-3] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Absorption of photons by pigments in photoreceptor cells results in photoisomerization of the chromophore, 11-cis-retinal, to all-trans-retinal and activation of opsin. Photolysed chromophore is converted back to the 11-cis-configuration via several enzymatic steps in photoreceptor and retinal pigment epithelial cells. We investigated the levels of retinoids in mouse retina during constant illumination and regeneration in the dark as a means of obtaining more information about the rate-limiting step of the visual cycle and about cycle intermediates that could be responsible for desensitization of the visual system. All-trans-retinal accumulated in the retinas during constant illumination and following flash illumination. Decay of all-trans-retinal in the dark following constant illumination occurred without substantial accumulation of all-trans-retinal, generated by constant approximately equal to visual pigment regeneration (t1/2 approximately 5 and t1/2 approximately 7 min, respectively). All-trans-retinal, generated by constant illumination, decayed approximately 3 times more rapidly than that generated by a flash and, as shown previously, the rate of rhodopsin regeneration following a flash was approximately 4 times slower than after constant illumination. The retinyl ester pool (> 95% all-trans-retinyl ester) did not show a statistically significant change in size or composition during illumination. In addition, constant illumination increased the amount of photoreceptor membrane-associated arrestin. The results suggest that the rate-limiting step of the visual cycle is the reduction of all-trans-retinal to all-trans-retinol by all-trans-retinol dehydrogenase. The accumulation of all-trans-retinal during illumination may be responsible, in part, for the reduction in sensitivity of the visual system that accompanies photobleaching and may contribute to the development of retinal pathology associated with light damage and aging.
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Affiliation(s)
- J C Saari
- Department of Ophthalmology, University of Washington School of Medicine, Seattle 98195-6485, USA.
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42
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Cideciyan AV, Zhao X, Nielsen L, Khani SC, Jacobson SG, Palczewski K. Null mutation in the rhodopsin kinase gene slows recovery kinetics of rod and cone phototransduction in man. Proc Natl Acad Sci U S A 1998; 95:328-33. [PMID: 9419375 PMCID: PMC18214 DOI: 10.1073/pnas.95.1.328] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Rhodopsin kinase (RK), a specialized G-protein-coupled receptor kinase expressed in retina, is involved in quenching of light-induced signal transduction in photoreceptors. The role of RK in recovery after photoactivation has been explored in vitro and in vivo experimentally but has not been specifically defined in humans. We investigated the effects on human vision of a mutation in the RK gene causing Oguchi disease, a recessively inherited retinopathy. In vitro experiments demonstrated that the mutation, a deletion of exon 5, abolishes the enzymatic activity of RK and is likely a null. Both a homozygote and heterozygote with this RK mutation had recovery phase abnormalities of rod-isolated photoresponses by electroretinography (ERG); photoactivation was normal. Kinetics of rod bleaching adaptation by psychophysics were dramatically slowed in the homozygote but normal final thresholds were attained. Light adaptation was normal at low backgrounds but became abnormal at higher backgrounds. A slight slowing of cone deactivation kinetics in the homozygote was detected by ERG. Cone bleaching adaptation and background adaptation were normal. In this human in vivo condition without a functional RK and probable lack of phosphorylation and arrestin binding to activated rhodopsin, reduction of photolyzed chromophore and regeneration processes with 11-cis-retinal probably constitute the sole pathway for recovery of rod sensitivity. The role of RK in rods would thus be to accelerate inactivation of activated rhodopsin molecules that in concert with regeneration leads to the normal rate of recovery of sensitivity. Cones may rely mainly on regeneration for the inactivation of photolyzed visual pigment, but RK also contributes to cone recovery.
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Affiliation(s)
- A V Cideciyan
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.
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43
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Nato A, Mirshahi A, Tichtinsky G, Mirshahi M, Faure JP, Lavergne D, De Buyser J, Jean C, Ducreux G, Henry Y. Immunological detection of potential signal-transduction proteins expressed during wheat somatic tissue culture. PLANT PHYSIOLOGY 1997; 113:801-807. [PMID: 9085574 PMCID: PMC158199 DOI: 10.1104/pp.113.3.801] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
An immunochemical approach was used to detect the expression of putative guanine nucleotide-binding proteins (G-proteins), arrestin, and nucleoside diphosphate kinases during wheat (Triticum aestivum) tissue culture initiated from immature embryos. Both the soluble and membrane extracts from the immature embryos revealed bands of 58, 40, and 16 kD with antibodies to G-protein (alpha subunit), arrestin, and nucleoside diphosphate kinase, respectively. These proteins were overexpressed in vitro in both nonembryogenic callus and embryogenic cultures. An additional soluble protein (32 kD) was detected by anti-G alpha antibodies in cultured tissues but not in immature embryos, suggesting a possible function in cell multiplication. Moreover, somatic embryogenesis was associated with the appearance of a 29-kD protein reactive with anti-arrstin antibodies, both in soluble and membrane fractions. Tissue-cultured genetic stocks of Chinese Spring wheat, including the disomic, 36 ditelosomic, and 6 nullisomic-tetrasomic wheat lines, were used to ascertain the chromosomal location of the genes encoding the 29-kD arrestin-like protein. The lack of a signal with the nonembryogenic ditelosomic 3 D short chromosome arm line suggests that the 3 D long chromosome arm possesses at least one gene involved in the expression of the 29-kD protein. The putative role of the 29-kD protein in signal-transduction regulating embryogenesis is discussed.
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Affiliation(s)
- A Nato
- Laboratoire de Morphogénèse Expérimentale Végétale, Université Paris XI, Orsay, France.
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44
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Gurevich VV, Benovic JL. Mechanism of phosphorylation-recognition by visual arrestin and the transition of arrestin into a high affinity binding state. Mol Pharmacol 1997; 51:161-9. [PMID: 9016359 DOI: 10.1124/mol.51.1.161] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Arrestin plays an important role in quenching phototransduction via its ability to interact specifically with the phosphorylated light-activated form of the visual receptor rhodopsin (P-Rh*). Previous studies have demonstrated that Arg175 in bovine arrestin is directly involved in the phosphorylation-dependent binding of arrestin to rhodopsin and seems to function as a phosphorylation-sensitive trigger. In this study, we further probed the molecular mechanism of phosphorylation recognition by substituting 19 different amino acids for Arg175. We also assessed the effects of mutagenesis of several other highly conserved residues within the phosphorylation-recognition region (Val170, Leu172, Leu173, Ile174, Val177, and Gln178). The binding of all of these mutants to P-Rh*, light-activated rhodopsin, and truncated rhodopsin, which lacks the carboxyl-terminal phosphorylation sites, was then characterized. Overall, our results suggest that arrestin interaction with the phosphorylated carboxyl-terminal domain of rhodopsin activates two relatively independent changes in arrestin: (a) mobilization of additional binding sites and (b) increased affinity of the phosphorylation-recognition region for the rhodopsin carboxyl-terminal domain. Together, these two mechanisms ensure the exquisite selectivity of arrestin toward P-Rh*. Mutagenesis of residues that play a major role in binding site mobilization and phosphorylation-recognition enabled us to create "constitutively active" (phosphorylation-independent) arrestin mutants that have high affinity for both P-Rh* and light-activated rhodopsin. The introduction of a negative charge in position 175 was particularly effective in this respect. A detailed molecular model of phosphorylation-recognition is proposed.
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Affiliation(s)
- V V Gurevich
- Department of Biochemistry and Molecular Pharmacology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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45
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Felber S, Breuer HP, Petruccione F, Honerkamp J, Hofmann KP. Stochastic simulation of the transducin GTPase cycle. Biophys J 1996; 71:3051-63. [PMID: 8968576 PMCID: PMC1233794 DOI: 10.1016/s0006-3495(96)79499-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
On rod disc membranes, single photoactivated rhodopsin (R*) molecules catalytically activate many copies of the G-protein (Gt), which in turn binds and activates the effector (phosphodiesterase). We have performed master equation simulations of the underlying diffusional protein interactions on a rectangular 1-micron2 model membrane, divided into 15 x 15 cells. Mono- and bimolecular reactions occur within cells, and diffusional transitions occur between (neighboring) cells. Reaction and diffusion constants yield the related probabilities for the stochastic transitions. The calculated kinetics of active effector form a response that is essentially determined by the stochastic lifetime distribution of R* (with characteristic time tau R*) and the reaction constants of Gt activation. Only a short tau R* (approximately 0.3 s) and a high catalytic rate (3000-4000 Gt s-1 R*-1) are consistent with electrophysiological data. Although R* shut-off limits the rise of the response, the lifetime distribution of free R* is not translated into a corresponding variability of the response peaks, because 1) the lifetime distribution of catalytically engaged R* is distorted, 2) small responses are enlarged by an overshoot of active effector, and 3) larger responses tend to undergo saturation. Comparison of these results to published photocurrent waveforms may open ways to understand the relative uniformity of the rod response.
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Affiliation(s)
- S Felber
- Institut für Medizinische Physik und Biophysik, Medizinische Fakultät Charité, Humboldt-Universität zu Berlin, Germany
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46
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Helmreich EJ, Hofmann KP. Structure and function of proteins in G-protein-coupled signal transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1286:285-322. [PMID: 8982287 DOI: 10.1016/s0304-4157(96)00013-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- E J Helmreich
- Department of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Germany
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47
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Abstract
Transgenic mice provide a powerful tool for elucidating the molecular mechanisms of phototransduction. Mice expressing a phosphorylation-deficient rhodopsin and mice deficient in arrestin are being used to study shutoff of photoactivated rhodopsin. These in vivo mouse studies indicate that shutoff is partially mediated by rhodopsin phosphorylation alone, but complete deactivation on a physiological time scale requires arrestin. Work on other transgenic mutant mice to unravel the function of recoverin and phosducin and to further define the role of the gamma subunit of phosphodiesterase is in progress. Transgenic mice are also being used to investigate how mutant proteins give rise to retinal disease and to develop therapeutic interventions.
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Affiliation(s)
- J Lem
- Department of Ophthalmology, New England Eye Center, Tufts Medical School, 750 Washington Street, Box 450, Boston, Massachusetts 02111, USA.
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48
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Langlois G, Chen CK, Palczewski K, Hurley JB, Vuong TM. Responses of the phototransduction cascade to dim light. Proc Natl Acad Sci U S A 1996; 93:4677-82. [PMID: 8643463 PMCID: PMC39338 DOI: 10.1073/pnas.93.10.4677] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The biochemistry of visual excitation is kinetically explored by measuring the activity of the cGMP phosphodiesterase (PDE) at light levels that activate only a few tens of rhodopsin molecules per rod. At 23 degrees C and in the presence of ATP, the pulse of PDE activity lasts 4 s (full width at half maximum). Complementing the rod outer segments (ROS) with rhodopsin kinase (RK) and arrestin or its splice variant p44 does not significantly shorten the pulse. But when the ROS are washed, the duration of the signal doubles. Adding either arrestin or p44 back to washed ROS approximately restores the pulse width to its initial value, with p44 being 10 times more efficient than arrestin. This supports the idea that, in vivo, capping of phosphorylated R* is mostly done by p44. When myristoylated (14:0) recoverin is added to unwashed ROS, the pulse duration and amplitude increase by about 50% if the free calcium is 500 nM. This effect increases further if the calcium is raised to 1 microM. Whenever R* deactivation is changed--when RK is exogenously enriched or when ATP is omitted from the buffer--there is no impact on the rising slope of the PDE pulse but only on its amplitude and duration. We explain this effect as due to the unequal competition between transducin and RK for R*. The kinetic model issued from this idea fits the data well, and its prediction that enrichment with transducin should lengthen the PDE pulse is successfully validated.
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Affiliation(s)
- G Langlois
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Valbonne, France
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49
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Ohguro H, Rudnicka-Nawrot M, Buczyłko J, Zhao X, Taylor JA, Walsh KA, Palczewski K. Structural and enzymatic aspects of rhodopsin phosphorylation. J Biol Chem 1996; 271:5215-24. [PMID: 8617805 DOI: 10.1074/jbc.271.9.5215] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Photoactivated rhodopsin (Rho*) is phosphorylated near the C terminus at multiple sites, predominantly at Ser334, Ser338, and Ser343. We systematically examined the sites of phosphorylation upon flash activation of Rho in rod outer segment (ROS) homogenates. Addition of an inhibitory antibody against rhodopsin kinase (RK) lowered phosphorylation at Ser334, Ser338, and Ser343, without changing the ratio between phosphorylation sites. In contrast, no effect of protein kinase C was detected after stimulation (by a phorbol ester), inhibition (with H7), or reconstitution of protein kinase C with purified ROS membranes. The stoichiometry and the ratio between different phosphorylation sites in purified Rho were also reproduced using RK, purified to apparent homogeneity from ROS or from an insect cell expression system. Thus, we conclude that light-dependent phosphorylation of Rho is mediated primarily by RK. Depalmitoylation of Rho at Cys322 and Cys323 altered the conformation of the C terminus of Rho, as observed by phosphorylation by casein kinase I, but did not affect phosphorylation by RK. The sites of phosphorylation were influenced, however, by the presence of four conserved amino acids at the C terminus of Rho. The accumulation of phosphorylated Ser334 observed in vivo could result from slower dephosphorylation of this site as compared with dephosphorylation of Ser338 and Ser343. These data provide a molecular mechanism for the site-specific phosphorylation of Rho observed in vivo.
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Affiliation(s)
- H Ohguro
- Department of Ophthalmology, School of Medicine, University of Washington, Seattle, 98195, USA
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50
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Abstract
Over the past decade and a half, there have been great advances in our understanding of how light is transduced into electrical signals by the retinal rod and cone photoreceptors in vertebrates. One essential feature of these sensory neurons is their ability to adapt to background illumination, which allows them to function over a broad range of light intensities. This adaptation appears to arise mostly from negative feedback on phototransduction that is mediated by calcium ions. Recent work has suggested that this feedback is fairly complex, and involves several pathways directed at different components of phototransduction. From direct measurements of these feedback pathways in rods, it is possible to evaluate their relative contributions to the overall sensitivity of the cell. At the same time, these feedback mechanisms, as currently known, appear to be sufficient for explaining the change in sensitivity of rods during adaptation to light.
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Affiliation(s)
- Y Koutalos
- Dept of Physiology, University of Colorado School of Medicine, Denver 80262, USA
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