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Wang F, Fernandez-Gonzalez P, Perez JJ, Morillo M, Garriga P. Retigabine increases the conformational stability of the visual photoreceptor rhodopsin. Int J Biol Macromol 2024; 279:135343. [PMID: 39241995 DOI: 10.1016/j.ijbiomac.2024.135343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Revised: 09/03/2024] [Accepted: 09/03/2024] [Indexed: 09/09/2024]
Abstract
Rhodopsin is the key photoreceptor protein that mediates vision in low-light conditions. Mutations in rhodopsin are the cause of retinal degenerative diseases such as retinitis pigmentosa. Some of these mutations cause a decreased stability of the receptor. It is, therefore, of interest to find new approaches that can help improving rhodopsin conformational stability. In this study, we have analyzed the effect of retigabine, an anticonvulsant formerly used to treat epilepsy, on rhodopsin thermal stability, regeneration capacity, and signal transduction by means of UV-visible and fluorescence spectroscopic techniques. We find that retigabine enhances the thermal stability of dark-state rhodopsin and improves chromophore regeneration without disrupting the photobleaching process. Furthermore, retigabine does not significantly affect transducin activation. These results provide novel insights into the potential therapeutic applications of retigabine in the treatment of retinitis pigmentosa caused by rhodopsin mutations that cause a decreased stability of the mutated receptors.
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Affiliation(s)
- Feifei Wang
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Quimica, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Pol Fernandez-Gonzalez
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Quimica, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Juan Jesus Perez
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Quimica, Universitat Politècnica de Catalunya-Barcelona Tech Edifici ETSEIB, Av. Diagonal, 647, 08028 Barcelona, Catalonia, Spain
| | - Margarita Morillo
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Quimica, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Pere Garriga
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Quimica, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain.
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2
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Ramkumar S, Jastrzebska B, Montenegro D, Sparrow JR, von Lintig J. Unraveling the mystery of ocular retinoid turnover: Insights from albino mice and the role of STRA6. J Biol Chem 2024; 300:105781. [PMID: 38395306 PMCID: PMC10950888 DOI: 10.1016/j.jbc.2024.105781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/02/2024] [Accepted: 02/17/2024] [Indexed: 02/25/2024] Open
Abstract
A delicate balance between photon absorption for vision and the protection of photoreceptors from light damage is pivotal for ocular health. This equilibrium is governed by the light-absorbing 11-cis-retinylidene chromophore of visual pigments, which, upon bleaching, transforms into all-trans-retinal and undergoes regeneration through an enzymatic pathway, named the visual cycle. Chemical side reactions of retinaldehyde during the recycling process can generate by-products that may result in a depletion of retinoids. In our study, we have clarified the crucial roles played by melanin pigmentation and the retinoid transporter STRA6 in preventing this loss and preserving the integrity of the visual cycle. Our experiments initially confirmed that consecutive green and blue light bleaching of isolated bovine rhodopsin produced 9-cis and 13-cis retinal. The same unusual retinoids were found in the retinas of mice exposed to intense light, with elevated concentrations observed in albino mice. Examining the metabolic fate of these visual cycle byproducts revealed that 9-cis-retinal, but not 13-cis-retinal, was recycled back to all-trans-retinal through an intermediate called isorhodopsin. However, investigations in Stra6 knockout mice unveiled that the generation of these visual cycle byproducts correlated with a light-induced loss of ocular retinoids and visual impairment. Collectively, our findings uncover important novel aspects of visual cycle dynamics, with implications for ocular health and photoreceptor integrity.
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Affiliation(s)
- Srinivasagan Ramkumar
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Beata Jastrzebska
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Diego Montenegro
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA; Departments of Pathology and Cell Biology, Columbia University Medical Center, New York, New York, USA
| | - Janet R Sparrow
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA; Departments of Pathology and Cell Biology, Columbia University Medical Center, New York, New York, USA
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
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3
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Cellular and Molecular Mechanisms of Pathogenesis Underlying Inherited Retinal Dystrophies. Biomolecules 2023; 13:biom13020271. [PMID: 36830640 PMCID: PMC9953031 DOI: 10.3390/biom13020271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/23/2023] [Accepted: 01/27/2023] [Indexed: 02/04/2023] Open
Abstract
Inherited retinal dystrophies (IRDs) are congenital retinal degenerative diseases that have various inheritance patterns, including dominant, recessive, X-linked, and mitochondrial. These diseases are most often the result of defects in rod and/or cone photoreceptor and retinal pigment epithelium function, development, or both. The genes associated with these diseases, when mutated, produce altered protein products that have downstream effects in pathways critical to vision, including phototransduction, the visual cycle, photoreceptor development, cellular respiration, and retinal homeostasis. The aim of this manuscript is to provide a comprehensive review of the underlying molecular mechanisms of pathogenesis of IRDs by delving into many of the genes associated with IRD development, their protein products, and the pathways interrupted by genetic mutation.
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Roy S, Nagrale P. Encoding the Photoreceptors of the Human Eye. Cureus 2022; 14:e30125. [PMID: 36381896 PMCID: PMC9644661 DOI: 10.7759/cureus.30125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 10/10/2022] [Indexed: 01/25/2023] Open
Abstract
This review aims to assess the anatomy of the human eye with a focus on exploring opportunities to mimic certain functionalities of photoreceptors in the optical system. This can help restore vision issues in people who had normal vision earlier, but their vision was impaired due to reasons that damaged parts of the eye; however, the functionality of the optic nerve remained intact. It is a conceptual article where the methodology to simulate artificial photoreceptors is discussed.
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Affiliation(s)
- Shreya Roy
- Medical Student, Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences, Wardha, IND
| | - Prachi Nagrale
- Ophthalmology, Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences, Wardha, IND
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5
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Sakai K, Shichida Y, Imamoto Y, Yamashita T. Creation of photocyclic vertebrate rhodopsin by single amino acid substitution. eLife 2022; 11:75979. [PMID: 35199641 PMCID: PMC8871353 DOI: 10.7554/elife.75979] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/14/2022] [Indexed: 01/27/2023] Open
Abstract
Opsins are universal photoreceptive proteins in animals and can be classified into three types based on their photoreaction properties. Upon light irradiation, vertebrate rhodopsin forms a metastable active state, which cannot revert back to the original dark state via either photoreaction or thermal reaction. By contrast, after photoreception, most opsins form a stable active state which can photoconvert back to the dark state. Moreover, we recently found a novel type of opsins whose activity is regulated by photocycling. However, the molecular mechanism underlying this diversification of opsins remains unknown. In this study, we showed that vertebrate rhodopsin acquired the photocyclic and photoreversible properties upon introduction of a single mutation at position 188. This revealed that the residue at position 188 contributes to the diversification of photoreaction properties of opsins by its regulation of the recovery from the active state to the original dark state.
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Affiliation(s)
- Kazumi Sakai
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.,Research Organization for Science and technology, Ritsumeikan University, Kusatsu, Japan
| | - Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
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6
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Ortega JT, Jastrzebska B. Rhodopsin as a Molecular Target to Mitigate Retinitis Pigmentosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1371:61-77. [PMID: 34962636 DOI: 10.1007/5584_2021_682] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Retinitis pigmentosa (RP) is a group of hereditary degenerative diseases affecting 1 of 4000 people worldwide and being the most prevalent cause of visual handicap among working populations in developed countries. These disorders are mainly related to the abnormalities in the rod G protein-coupled receptor (GPCR), rhodopsin reflected in the dysregulated membrane trafficking, stability and phototransduction processes that lead to progressive loss of retina function and eventually blindness. Currently, there is no cure for RP, and the therapeutic options are limited. Targeting rhodopsin with small molecule chaperones to improve the folding and stability of the mutant receptor is one of the most promising pharmacological approaches to alleviate the pathology of RP. This review provides an update on the current knowledge regarding small molecule compounds that have been evaluated as rhodopsin modulators to be considered as leads for the development of novel therapies for RP.
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Affiliation(s)
- Joseph T Ortega
- Department of Pharmacology, School of Medicine, Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Beata Jastrzebska
- Department of Pharmacology, School of Medicine, Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH, USA.
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7
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Cross-linking of bovine rhodopsin with sulfosuccinimidyl 4-(N maleimidomethyl)cyclohexane-1-carboxylate affects its functionality. Biochem J 2020; 477:2295-2312. [PMID: 32497171 DOI: 10.1042/bcj20200376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/01/2020] [Accepted: 06/03/2020] [Indexed: 02/08/2023]
Abstract
Rhodopsin is the photoreceptor protein involved in visual excitation in retinal rods. The functionality of bovine rhodopsin was determined following treatment with sulfosuccinimidyl 4-(N maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC), a bifunctional reagent capable of forming covalent cross-links between suitable placed lysines and cysteines. Denaturing polyacrylamide gel electrophoresis showed that rhodopsin incubated with sulfo-SMCC generated intermolecular dimers, trimers, and higher oligomers, although most of the sulfo-SMCC-treated protein remained as a monomer. Minor alterations on the absorption spectrum of light-activated sulfo-SMCC-treated rhodopsin were observed. However, only ∼2% stimulation of the guanine nucleotide binding activity of transducin was measured in the presence of sulfo-SMCC-cross-linked photolyzed rhodopsin. Moreover, rhodopsin kinase was not able of phosphorylating sulfo-SMCC-cross-linked rhodopsin after illumination. Rhodopsin was purified in the presence of either 0.1% or 1% n-dodecyl β-d-maltoside, to obtain dimeric and monomeric forms of the protein, respectively. Interestingly, no generation of the regular F1 and F2 thermolytic fragments was perceived with sulfo-SMCC-cross-linked rhodopsin either in the dimeric or monomeric state, implying the formation of intramolecular connections in the protein that might thwart the light-induced conformational changes required for interaction with transducin and rhodopsin kinase. Structural analysis of the rhodopsin three-dimensional structure suggested that the following lysine and cysteine pairs: Lys66/Lys67 and Cys316, Cys140 and Lys141, Cys140 and Lys248, Lys311 and Cys316, and/or Cys316 and Lys325 are potential candidates to generate intramolecular cross-links in the protein. Yet, the lack of fragmentation of sulfo-SMCC-treated Rho with thermolysin is consistent with the formation of cross-linking bridges between Lys66/Lys67 and Cys316, and/or Cys140 and Lys248.
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8
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Molecular effects and retinopathy induced by hydroxychloroquine during SARS-CoV-2 therapy: Role of CYP450 isoforms and epigenetic modulations. Eur J Pharmacol 2020; 886:173454. [PMID: 32763298 PMCID: PMC7402235 DOI: 10.1016/j.ejphar.2020.173454] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/30/2020] [Accepted: 07/30/2020] [Indexed: 01/07/2023]
Abstract
Antimalaria drugs such as chloroquine (CQ) and hydroxychloroquine (HCQ) have been administered to several inflammatory diseases including rheumatoid arthritis and systemic lupus erythematosus, and infectious diseases such as acquired immune deficiency syndrome and influenza. Recently, several patients infected with novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were given HCQ, and showed a discrepant response. HCQ inhibits SARS-CoV-2 cell entry, and inflammatory cascade by interfering with lysosomal and endosomal activities, and autophagy, impeding virus-membrane fusion, and inhibiting cytokine production resulted from inflammatory pathways activation. Despite ongoing administration of HCQ in a wide spectrum of disorders, there are some reports about several side effects, especially retinopathy in some patients treated with HCQ. Cytochrome P450 (CYP450) and its isoforms are the main metabolizers of HCQ and CQ. Pharmacokinetic properties of CYP enzymes are influenced by CYP polymorphism, non-coding RNAs, and epigenetic mechanisms such as DNA methylation, and histone acetylation. Accumulating evidence about side effects of HCQ in some patients raise the possibility that different response of patients to HCQ might be due to difference in their genome. Therefore, CYP450 genotyping especially for CYP2D6 might be helpful to refine HCQ dosage. Also, regular control of retina should be considered for patients under HCQ treatment. The major focus of the present review is to discuss about the pharmacokinetic and pharmacodynamic properties of CQ and HCQ that may be influenced by epigenetic mechanisms, and consequently cause several side effects especially retinopathy during SARS-CoV-2 therapy.
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9
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Do MTH. Melanopsin and the Intrinsically Photosensitive Retinal Ganglion Cells: Biophysics to Behavior. Neuron 2019; 104:205-226. [PMID: 31647894 PMCID: PMC6944442 DOI: 10.1016/j.neuron.2019.07.016] [Citation(s) in RCA: 146] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 06/19/2019] [Accepted: 07/12/2019] [Indexed: 12/19/2022]
Abstract
The mammalian visual system encodes information over a remarkable breadth of spatiotemporal scales and light intensities. This performance originates with its complement of photoreceptors: the classic rods and cones, as well as the intrinsically photosensitive retinal ganglion cells (ipRGCs). IpRGCs capture light with a G-protein-coupled receptor called melanopsin, depolarize like photoreceptors of invertebrates such as Drosophila, discharge electrical spikes, and innervate dozens of brain areas to influence physiology, behavior, perception, and mood. Several visual responses rely on melanopsin to be sustained and maximal. Some require ipRGCs to occur at all. IpRGCs fulfill their roles using mechanisms that include an unusual conformation of the melanopsin protein, an extraordinarily slow phototransduction cascade, divisions of labor even among cells of a morphological type, and unorthodox configurations of circuitry. The study of ipRGCs has yielded insight into general topics that include photoreceptor evolution, cellular diversity, and the steps from biophysical mechanisms to behavior.
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Affiliation(s)
- Michael Tri H Do
- F.M. Kirby Neurobiology Center and Department of Neurology, Boston Children's Hospital and Harvard Medical School, Center for Life Science 12061, 3 Blackfan Circle, Boston, MA 02115, USA.
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10
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Du Q, Peng J, Wu P, He H. Review: Metal-organic framework based crystalline sponge method for structure analysis. Trends Analyt Chem 2018. [DOI: 10.1016/j.trac.2018.02.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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11
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Saeed A, Hoekstra M, Hoeke MO, Heegsma J, Faber KN. The interrelationship between bile acid and vitamin A homeostasis. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:496-512. [PMID: 28111285 DOI: 10.1016/j.bbalip.2017.01.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 01/04/2017] [Accepted: 01/18/2017] [Indexed: 12/12/2022]
Abstract
Vitamin A is a fat-soluble vitamin important for vision, reproduction, embryonic development, cell differentiation, epithelial barrier function and adequate immune responses. Efficient absorption of dietary vitamin A depends on the fat-solubilizing properties of bile acids. Bile acids are synthesized in the liver and maintained in an enterohepatic circulation. The liver is also the main storage site for vitamin A in the mammalian body, where an intimate collaboration between hepatocytes and hepatic stellate cells leads to the accumulation of retinyl esters in large cytoplasmic lipid droplet hepatic stellate cells. Chronic liver diseases are often characterized by disturbed bile acid and vitamin A homeostasis, where bile production is impaired and hepatic stellate cells lose their vitamin A in a transdifferentiation process to myofibroblasts, cells that produce excessive extracellular matrix proteins leading to fibrosis. Chronic liver diseases thus may lead to vitamin A deficiency. Recent data reveal an intricate crosstalk between vitamin A metabolites and bile acids, in part via the Retinoic Acid Receptor (RAR), Retinoid X Receptor (RXR) and the Farnesoid X Receptor (FXR), in maintaining vitamin A and bile acid homeostasis. Here, we provide an overview of the various levels of "communication" between vitamin A metabolites and bile acids and its relevance for the treatment of chronic liver diseases.
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Affiliation(s)
- Ali Saeed
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Institute of Molecular biology & Bio-technology, Bahauddin Zakariya University, Multan, Pakistan.
| | - Mark Hoekstra
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
| | - Martijn Oscar Hoeke
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
| | - Janette Heegsma
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Laboratory Medicine, Center for Liver, Digestive, and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
| | - Klaas Nico Faber
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
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12
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Le Bailly BAF, Byrne L, Clayden J. Refoldable Foldamers: Global Conformational Switching by Deletion or Insertion of a Single Hydrogen Bond. Angew Chem Int Ed Engl 2016; 55:2132-6. [PMID: 26762559 PMCID: PMC4755161 DOI: 10.1002/anie.201510605] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Indexed: 11/12/2022]
Abstract
Small changes in the structure of a foldamer may lead to gross changes in conformational preference. We show that the simple insertion or deletion of a single hydrogen bond by changes in pH or by photochemical deprotection is sufficient to refold a helical oligomer, interconverting M and P screw-sense preference. As a consequence of the switch, information may be transmitted to a remote catalytic site, selectively directing the formation of either of two enantiomeric products by a reaction involving 1,22-remote intermolecular asymmetric induction.
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Affiliation(s)
- Bryden A F Le Bailly
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.,School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Liam Byrne
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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13
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Le Bailly BAF, Byrne L, Clayden J. Refoldable Foldamers: Global Conformational Switching by Deletion or Insertion of a Single Hydrogen Bond. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201510605] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bryden A. F. Le Bailly
- School of Chemistry; University of Bristol; Cantock's Close Bristol BS8 1TS UK
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - Liam Byrne
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - Jonathan Clayden
- School of Chemistry; University of Bristol; Cantock's Close Bristol BS8 1TS UK
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14
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Chatterjee D, Eckert CE, Slavov C, Saxena K, Fürtig B, Sanders CR, Gurevich VV, Wachtveitl J, Schwalbe H. Influence of Arrestin on the Photodecay of Bovine Rhodopsin. Angew Chem Int Ed Engl 2015; 54:13555-60. [PMID: 26383645 PMCID: PMC4685475 DOI: 10.1002/anie.201505798] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/11/2015] [Indexed: 11/07/2022]
Abstract
Continued activation of the photocycle of the dim-light receptor rhodopsin leads to the accumulation of all-trans-retinal in the rod outer segments (ROS). This accumulation can damage the photoreceptor cell. For retinal homeostasis, deactivation processes are initiated in which the release of retinal is delayed. One of these processes involves the binding of arrestin to rhodopsin. Here, the interaction of pre-activated truncated bovine visual arrestin (Arr(Tr)) with rhodopsin in 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) micelles is investigated by solution NMR techniques and flash photolysis spectroscopy. Our results show that formation of the rhodopsin-arrestin complex markedly influences partitioning in the decay kinetics of rhodopsin, which involves the simultaneous formation of a meta II and a meta III state from the meta I state. Binding of Arr(Tr) leads to an increase in the population of the meta III state and consequently to an approximately twofold slower release of all-trans-retinal from rhodopsin.
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Affiliation(s)
- Deep Chatterjee
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Carl Elias Eckert
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Chavdar Slavov
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Krishna Saxena
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Boris Fürtig
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Charles R Sanders
- Department of Biochemistry, Center for Structural Biology, Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 (USA)
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232 (USA)
| | - Josef Wachtveitl
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany).
| | - Harald Schwalbe
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany).
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15
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Chatterjee D, Eckert CE, Slavov C, Saxena K, Fürtig B, Sanders CR, Gurevich VV, Wachtveitl J, Schwalbe H. Influence of Arrestin on the Photodecay of Bovine Rhodopsin. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201505798] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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16
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van der Steen JB, Hellingwerf KJ. Activation of the General Stress Response of Bacillus subtilis by Visible Light. Photochem Photobiol 2015; 91:1032-45. [PMID: 26189730 DOI: 10.1111/php.12499] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 06/25/2015] [Indexed: 12/20/2022]
Abstract
A key challenge for microbiology is to understand how evolution has shaped the wiring of regulatory networks. This is amplified by the paucity of information of power-spectra of physicochemical stimuli to which microorganisms are exposed. Future studies of genome evolution, driven by altered stimulus regimes, will therefore require a versatile signal transduction system that allows accurate signal dosing. Here, we review the general stress response of Bacillus subtilis, and its upstream signal transduction network, as a candidate system. It can be activated by red and blue light, and by many additional stimuli. Signal integration therefore is an intricate function of this system. The blue-light response is elicited via the photoreceptor YtvA, which forms an integral part of stressosomes, to activate expression of the stress regulon of B. subtilis. Signal transfer through this network can be assayed with reporter enzymes, while intermediate steps can be studied with live-cell imaging of fluorescently tagged proteins. Different parts of this system have been studied in vitro, such that its computational modeling has made significant progress. One can directly relate the microscopic characteristics of YtvA with activation of the general stress regulon, making this system a very well-suited system for network evolution studies.
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Affiliation(s)
- Jeroen B van der Steen
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Klaas J Hellingwerf
- Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
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17
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Effects of Mutations of Lys41 and Asp102 of Bacteriorhodopsin. Biosci Biotechnol Biochem 2014; 75:1364-70. [DOI: 10.1271/bbb.110180] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Stehle J, Silvers R, Werner K, Chatterjee D, Gande S, Scholz F, Dutta A, Wachtveitl J, Klein-Seetharaman J, Schwalbe H. Characterization of the simultaneous decay kinetics of metarhodopsin states II and III in rhodopsin by solution-state NMR spectroscopy. Angew Chem Int Ed Engl 2014; 53:2078-84. [PMID: 24505031 DOI: 10.1002/anie.201309581] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Indexed: 11/09/2022]
Abstract
The mammalian visual dim-light photoreceptor rhodopsin is considered a prototype G protein-coupled receptor. Here, we characterize the kinetics of its light-activation process. Milligram quantities of α,ε-(15)N-labeled tryptophan rhodopsin were produced in stably transfected HEK293 cells. Assignment of the chemical shifts of the indole signals was achieved by generating the single-point-tryptophan to phenylalanine mutants, and the kinetics of each of the five tryptophan residues were recorded. We find kinetic partitioning in rhodopsin decay, including three half-lives, that reveal two parallel processes subsequent to rhodopsin activation that are related to the photocycle. The meta II and meta III states emerge in parallel with a relative ratio of about 3:1. Transient formation of the meta III state was confirmed by flash photolysis experiments. From analysis of the site-resolved kinetic data we propose the involvement of the E2 -loop in the formation of the meta III state.
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Affiliation(s)
- Jochen Stehle
- Institute for Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
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Stehle J, Silvers R, Werner K, Chatterjee D, Gande S, Scholz F, Dutta A, Wachtveitl J, Klein-Seetharaman J, Schwalbe H. Characterization of the Simultaneous Decay Kinetics of Metarhodopsin States II and III in Rhodopsin by Solution-State NMR Spectroscopy. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201309581] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Sommer ME, Hofmann KP, Heck M. Not just signal shutoff: the protective role of arrestin-1 in rod cells. Handb Exp Pharmacol 2014; 219:101-16. [PMID: 24292826 DOI: 10.1007/978-3-642-41199-1_5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The retinal rod cell is an exquisitely sensitive single-photon detector that primarily functions in dim light (e.g., moonlight). However, rod cells must routinely survive light intensities more than a billion times greater (e.g., bright daylight). One serious challenge to rod cell survival in daylight is the massive amount of all-trans-retinal that is released by Meta II, the light-activated form of the photoreceptor rhodopsin. All-trans-retinal is toxic, and its condensation products have been implicated in disease. Our recent work has developed the concept that rod arrestin (arrestin-1), which terminates Meta II signaling, has an additional role in protecting rod cells from the consequences of bright light by limiting free all-trans-retinal. In this chapter we will elaborate upon the molecular mechanisms by which arrestin-1 serves as both a single-photon response quencher as well as an instrument of rod cell survival in bright light. This discussion will take place within the framework of three distinct functional modules of vision: signal transduction, the retinoid cycle, and protein translocation.
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Affiliation(s)
- Martha E Sommer
- Institut für Medizinische Physik und Biophysik (CC2), Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany,
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Park PSH. Constitutively active rhodopsin and retinal disease. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 70:1-36. [PMID: 24931191 DOI: 10.1016/b978-0-12-417197-8.00001-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Rhodopsin is the light receptor in rod photoreceptor cells of the retina that initiates scotopic vision. In the dark, rhodopsin is bound to the chromophore 11-cis retinal, which locks the receptor in an inactive state. The maintenance of an inactive rhodopsin in the dark is critical for rod photoreceptor cells to remain highly sensitive. Perturbations by mutation or the absence of 11-cis retinal can cause rhodopsin to become constitutively active, which leads to the desensitization of photoreceptor cells and, in some instances, retinal degeneration. Constitutive activity can arise in rhodopsin by various mechanisms and can cause a variety of inherited retinal diseases including Leber congenital amaurosis, congenital night blindness, and retinitis pigmentosa. In this review, the molecular and structural properties of different constitutively active forms of rhodopsin are overviewed, and the possibility that constitutive activity can arise from different active-state conformations is discussed.
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Affiliation(s)
- Paul Shin-Hyun Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA.
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Shelyakin PV, Kovarskii AL, Kasparov VV, Fel’dman TB, Ostrovskii MA. A study of the photoinduced conformational mobility of spin-labeled regenerated rhodopsin by ESR spectroscopy. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B 2013. [DOI: 10.1134/s1990793112060127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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van der Steen JB, Nakasone Y, Hendriks J, Hellingwerf KJ. Modeling the functioning of YtvA in the general stress response in Bacillus subtilis. MOLECULAR BIOSYSTEMS 2013; 9:2331-43. [DOI: 10.1039/c3mb70124g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lomonosova E, Kolesnikov AV, Kefalov VJ, Kisselev OG. Signaling states of rhodopsin in rod disk membranes lacking transducin βγ-complex. Invest Ophthalmol Vis Sci 2012; 53:1225-33. [PMID: 22266510 DOI: 10.1167/iovs.11-9350] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To characterize the possible role of transducin Gtβγ-complex in modulating the signaling properties of photoactivated rhodopsin and its lifetime in rod disc membranes and intact rods. METHODS Rhodopsin photolysis was studied using UV-visible spectroscopy and rapid scanning spectroscopy in the presence of hydroxylamine in highly purified wild-type and Gtγ-deficient mouse rod disc membranes. Complex formation between photoactivated rhodopsin and transducin was measured by extra-metarhodopsin (meta) II assay. Recovery of dark current and flash sensitivity in individual intact wild-type and Gtγ-deficient mouse rods was measured by single-cell suction recordings. RESULTS Photoconversion of rhodopsin to meta I/meta II equilibrium proceeds normally after elimination of the Gtβγ-complex. The meta I/meta II ratio, the rate of meta II decay, the reactivity of meta II toward hydroxylamine, and the rate of meta III formation in Gtγ-deficient rod disc membranes were identical with those observed in wild-type samples. Under low-intensity illumination, the amount of extra-meta II in Gtγ-deficient discs was significantly reduced. The initial rate of dark current recovery after 12% rhodopsin bleach was three times faster in Gtγ-deficient rods, whereas the rate of the late current recovery was largely unchanged. Mutant rods also exhibited faster postbleach recovery of flash sensitivity. CONCLUSIONS Photoactivation and thermal decay of rhodopsin proceed similarly in wild-type and Gtγ-deficient mouse rods, but the complex formation between photoactivated rhodopsin and transducin is severely compromised in the absence of Gtβγ. The resultant lower transduction activation contributes to faster photoresponse recovery after a moderate pigment bleach in Gtγ-deficient rods.
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Affiliation(s)
- Elena Lomonosova
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, MO, USA
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Bossi ML, Aramendía PF. Photomodulation of macroscopic properties. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2011. [DOI: 10.1016/j.jphotochemrev.2011.09.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Piechnick R, Heck M, Sommer ME. Alkylated hydroxylamine derivatives eliminate peripheral retinylidene Schiff bases but cannot enter the retinal binding pocket of light-activated rhodopsin. Biochemistry 2011; 50:7168-76. [PMID: 21766795 DOI: 10.1021/bi200675y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Besides Lys-296 in the binding pocket of opsin, all-trans-retinal forms adducts with peripheral lysine residues and phospholipids, thereby mimicking the spectral and chemical properties of metarhodopsin species. These pseudophotoproducts composed of nonspecific retinylidene Schiff bases have long plagued the investigation of rhodopsin deactivation and identification of decay products. We discovered that, while hydroxylamine can enter the retinal binding pocket of light-activated rhodopsin, the modified hydroxylamine compounds o-methylhydroxylamine (mHA), o-ethylhydroxylamine (eHA), o-tert-butylhydroxylamine (t-bHA), and o-(carboxymethyl)hydroxylamine (cmHA) are excluded. However, the alkylated hydroxylamines react quickly and efficiently with exposed retinylidene Schiff bases to form their respective retinal oximes. We further investigated how t-bHA affects light-activated rhodopsin and its interaction with binding partners. We found that both metarhodopsin II (Meta II) and Meta III are resistant to t-bHA, and neither arrestin nor transducin binding is affected by t-bHA. This discovery suggests that the hypothetical solvent channel that opens in light-activated rhodopsin is extremely stringent with regard to size and/or polarity. We believe that alkylated hydroxylamines will prove to be extremely useful reagents for the investigation of rhodopsin activation and decay mechanisms. Furthermore, the use of alkylated hydroxylamines should not be limited to in vitro studies and could help elucidate visual signal transduction mechanisms in the living cells of the retina.
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Affiliation(s)
- Ronny Piechnick
- Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany
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Burri BJ. Evaluating Sweet Potato as an Intervention Food to Prevent Vitamin A Deficiency. Compr Rev Food Sci Food Saf 2011. [DOI: 10.1111/j.1541-4337.2010.00146.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Piwowarski P, Ritter E, Hofmann KP, Hildebrandt P, von Stetten D, Scheerer P, Michael N, Lamparter T, Bartl F. Light-induced activation of bacterial phytochrome Agp1 monitored by static and time-resolved FTIR spectroscopy. Chemphyschem 2010; 11:1207-14. [PMID: 20333618 DOI: 10.1002/cphc.200901008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phytochromes, which regulate many biological processes in plants, bacteria, and fungi, can exist in two stable states, Pr and Pfr, that can be interconverted by light, via a number of intermediates such as meta-Rc. Herein we employ FTIR spectroscopy to study the Pr-to-Pfr conversion of the bacteriophytochrome Agp1 from Agrobacterium tumefaciens. Static FTIR Pfr/Pr and meta-Rc/Pr difference spectra are disentangled in terms of cofactor and protein structural changes. Guided by DFT calculations on cofactor models, the chromophore conformational changes can be grouped into structural adjustments of the cofactor-protein interactions localized in the C-D dipyrrole moiety, that is, the photoisomerisation site, and in the A-B dipyrrole moiety including the protein attachment site. Whereas changes at the C and D rings appear to be largely completed in the meta-Rc state, the structural changes in the A-B unit occur during the transition from meta-Rc to Pfr, concomitant with the main protein structural changes, as demonstrated by static and time-resolved FTIR difference spectroscopy. We employ this technique to monitor, for the first time, the dynamics of the photocycle of phytochrome on the millisecond timescale. By extending the studies to genetically engineered protein variants of Agp1, we further demonstrate that H250 and D197 as well as the PHY domain are essential for formation of the Pfr state. Based on the IR spectroscopic and available crystallographic data we discuss the role of critical amino acid residues for the protein-cofactor interactions during the photoinduced reaction cycle.
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Affiliation(s)
- Patrick Piwowarski
- Institut für Medizinische Physik und Biophysik, Charité, Universitätsmedizin Berlin, Charitéplatz 1, 10098 Berlin, Germany
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Schmidt P, Berger C, Scheidt HA, Berndt S, Bunge A, Beck-Sickinger AG, Huster D. A reconstitution protocol for the in vitro folded human G protein-coupled Y2 receptor into lipid environment. Biophys Chem 2010; 150:29-36. [PMID: 20421142 DOI: 10.1016/j.bpc.2010.02.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 02/10/2010] [Indexed: 10/19/2022]
Abstract
Although highly resolved crystal structures of G protein-coupled receptors have become available within the last decade, the need for studying these molecules in their natural membrane environment, where the molecules are rather dynamic, has been widely appreciated. Solid-state NMR spectroscopy is an excellent method to study structure and dynamics of membrane proteins in their native lipid environment. We developed a reconstitution protocol for the uniformly (15)N labeled Y(2) receptor into a bicelle-like lipid structure with high yields suitable for NMR studies. Milligram quantities of target protein were expressed in Escherichia coli using an optimized fermentation process in defined medium yielding in over 10mg/L medium of purified Y(2) receptor solubilized in SDS micelles. The structural integrity of the receptor molecules was strongly increased through refolding and subsequent reconstitution into phospholipid membranes. Specific ligand binding to the integrated receptor was determined using radioligand affinity assay. Further, by NMR measurement a dispersion of the (15)N signals comparable to native rhodopsin was shown. The efficiency of the reconstitution could also be inferred from the fact that reasonable (13)C NMR spectra at natural abundance could be acquired.
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Affiliation(s)
- Peter Schmidt
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany
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Ohara K, Kawano M, Inokuma Y, Fujita M. A Porous Coordination Network Catalyzes an Olefin Isomerization Reaction in the Pore. J Am Chem Soc 2009; 132:30-1. [DOI: 10.1021/ja908794n] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kazuaki Ohara
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, CREST-JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784, South Korea
| | - Masaki Kawano
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, CREST-JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784, South Korea
| | - Yasuhide Inokuma
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, CREST-JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784, South Korea
| | - Makoto Fujita
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, CREST-JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784, South Korea
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Abstract
By its action on rhodopsin, light triggers the well-known visual transduction cascade, but can also induce cell damage and death through phototoxic mechanisms - a comprehensive understanding of which is still elusive despite more than 40 years of research. Herein, we integrate recent experimental findings to address several hypotheses of retinal light damage, premised in part on the close anatomical and metabolic relationships between the photoreceptors and the retinal pigment epithelium. We begin by reviewing the salient features of light damage, recently joined by evidence for retinal remodeling which has implications for the prognosis of recovery of function in retinal degenerations. We then consider select factors that influence the progression of the damage process and the extent of visual cell loss. Traditional, genetically modified, and emerging animal models are discussed, with particular emphasis on cone visual cells. Exogenous and endogenous retinal protective factors are explored, with implications for light damage mechanisms and some suggested avenues for future research. Synergies are known to exist between our long term light environment and photoreceptor cell death in retinal disease. Understanding the molecular mechanisms of light damage in a variety of animal models can provide valuable insights into the effects of light in clinical disorders and may form the basis of future therapies to prevent or delay visual cell loss.
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A G protein-coupled receptor at work: the rhodopsin model. Trends Biochem Sci 2009; 34:540-52. [PMID: 19836958 DOI: 10.1016/j.tibs.2009.07.005] [Citation(s) in RCA: 294] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 07/17/2009] [Accepted: 07/28/2009] [Indexed: 12/17/2022]
Abstract
G protein-coupled receptors (GPCRs) are ubiquitous signal transducers in cell membranes, as well as important drug targets. Interaction with extracellular agonists turns the seven transmembrane helix (7TM) scaffold of a GPCR into a catalyst for GDP and GTP exchange in heterotrimeric Galphabetagamma proteins. Activation of the model GPCR, rhodopsin, is triggered by photoisomerization of its retinal ligand. From the augmentation of biochemical and biophysical studies by recent high-resolution 3D structures, its activation intermediates can now be interpreted as the stepwise engagement of protein domains. Rearrangement of TM5-TM6 opens a crevice at the cytoplasmic side of the receptor into which the C terminus of the Galpha subunit can bind. The Galpha C-terminal helix is used as a transmission rod to the nucleotide binding site. The mechanism relies on dynamic interactions between conserved residues and could therefore be common to other GPCRs.
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Hisatomi O, Iwasa T, Kataoka M, Ebrey T. Introduction to the Symposium-in-Print on Photoreceptors and Signal Transduction in Honor of Professor Fumio Tokunaga. Photochem Photobiol 2008. [DOI: 10.1111/j.1751-1097.2008.00391.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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