1
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Vasudevan S, Senapati S, Pendergast M, Park PSH. Aggregation of rhodopsin mutants in mouse models of autosomal dominant retinitis pigmentosa. Nat Commun 2024; 15:1451. [PMID: 38365903 PMCID: PMC10873427 DOI: 10.1038/s41467-024-45748-4] [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: 04/07/2023] [Accepted: 02/01/2024] [Indexed: 02/18/2024] Open
Abstract
Mutations in rhodopsin can cause it to misfold and lead to retinal degeneration. A distinguishing feature of these mutants in vitro is that they mislocalize and aggregate. It is unclear whether or not these features contribute to retinal degeneration observed in vivo. The effect of P23H and G188R misfolding mutations were examined in a heterologous expression system and knockin mouse models, including a mouse model generated here expressing the G188R rhodopsin mutant. In vitro characterizations demonstrate that both mutants aggregate, with the G188R mutant exhibiting a more severe aggregation profile compared to the P23H mutant. The potential for rhodopsin mutants to aggregate in vivo was assessed by PROTEOSTAT, a dye that labels aggregated proteins. Both mutants mislocalize in photoreceptor cells and PROTEOSTAT staining was detected surrounding the nuclei of photoreceptor cells. The G188R mutant promotes a more severe retinal degeneration phenotype and greater PROTEOSTAT staining compared to that promoted by the P23H mutant. Here, we show that the level of PROTEOSTAT positive cells mirrors the progression and level of photoreceptor cell death, which suggests a potential role for rhodopsin aggregation in retinal degeneration.
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Affiliation(s)
- Sreelakshmi Vasudevan
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Subhadip Senapati
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
- Prayoga Institute of Education Research, Bengaluru, KA, 560116, India
| | - Maryanne Pendergast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
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2
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Bighinati A, Adani E, Stanzani A, D’Alessandro S, Marigo V. Molecular mechanisms underlying inherited photoreceptor degeneration as targets for therapeutic intervention. Front Cell Neurosci 2024; 18:1343544. [PMID: 38370034 PMCID: PMC10869517 DOI: 10.3389/fncel.2024.1343544] [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: 11/23/2023] [Accepted: 01/16/2024] [Indexed: 02/20/2024] Open
Abstract
Retinitis pigmentosa (RP) is a form of retinal degeneration characterized by primary degeneration of rod photoreceptors followed by a secondary cone loss that leads to vision impairment and finally blindness. This is a rare disease with mutations in several genes and high genetic heterogeneity. A challenging effort has been the characterization of the molecular mechanisms underlying photoreceptor cell death during the progression of the disease. Some of the cell death pathways have been identified and comprise stress events found in several neurodegenerative diseases such as oxidative stress, inflammation, calcium imbalance and endoplasmic reticulum stress. Other cell death mechanisms appear more relevant to photoreceptor cells, such as high levels of cGMP and metabolic changes. Here we review some of the cell death pathways characterized in the RP mutant retina and discuss preclinical studies of therapeutic approaches targeting the molecular outcomes that lead to photoreceptor cell demise.
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Affiliation(s)
- Andrea Bighinati
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Elisa Adani
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Agnese Stanzani
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Sara D’Alessandro
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Valeria Marigo
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
- Center for Neuroscience and Neurotechnology, Modena, Italy
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3
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Abstract
Rhodopsin is the photoreceptor in human rod cells responsible for dim-light vision. The visual receptors are part of the large superfamily of G protein-coupled receptors (GPCRs) that mediate signal transduction in response to diverse diffusible ligands. The high level of sequence conservation within the transmembrane helices of the visual receptors and the family A GPCRs has long been considered evidence for a common pathway for signal transduction. I review recent studies that reveal a comprehensive mechanism for how light absorption by the retinylidene chromophore drives rhodopsin activation and highlight those features of the mechanism that are conserved across the ligand-activated GPCRs.
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Affiliation(s)
- Steven O Smith
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, New York, USA;
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4
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CRISPR/Cas9-Mediated Models of Retinitis Pigmentosa Reveal Differential Proliferative Response of Müller Cells between Xenopus laevis and Xenopus tropicalis. Cells 2022; 11:cells11050807. [PMID: 35269429 PMCID: PMC8909648 DOI: 10.3390/cells11050807] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 02/18/2022] [Accepted: 02/22/2022] [Indexed: 12/25/2022] Open
Abstract
Retinitis pigmentosa is an inherited retinal dystrophy that ultimately leads to blindness due to the progressive degeneration of rod photoreceptors and the subsequent non-cell autonomous death of cones. Rhodopsin is the most frequently mutated gene in this disease. We here developed rhodopsin gene editing-based models of retinitis pigmentosa in two Xenopus species, Xenopus laevis and Xenopus tropicalis, by using CRISPR/Cas9 technology. In both of them, loss of rhodopsin function results in massive rod cell degeneration characterized by progressive shortening of outer segments and occasional cell death. This is followed by cone morphology deterioration. Despite these apparently similar degenerative environments, we found that Müller glial cells behave differently in Xenopus laevis and Xenopus tropicalis. While a significant proportion of Müller cells re-enter into the cell cycle in Xenopus laevis, their proliferation remains extremely limited in Xenopus tropicalis. This work thus reveals divergent responses to retinal injury in closely related species. These models should help in the future to deepen our understanding of the mechanisms that have shaped regeneration during evolution, with tremendous differences across vertebrates.
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5
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Vasudevan S, Park PSH. Differential Aggregation Properties of Mutant Human and Bovine Rhodopsin. Biochemistry 2020; 60:6-18. [PMID: 33356167 DOI: 10.1021/acs.biochem.0c00733] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rhodopsin is the light receptor required for the function and health of photoreceptor cells. Mutations in rhodopsin can cause misfolding and aggregation of the receptor, which leads to retinal degeneration. Bovine rhodopsin is often used as a model to understand the effect of pathogenic mutations in rhodopsin due to the abundance of structural information on the bovine form of the receptor. It is unclear whether or not the bovine rhodopsin template is adequate in predicting the effect of these mutations occurring in human retinal disease or in predicting the efficacy of therapeutic strategies. To better understand the extent to which bovine rhodopsin can serve as a model, human and bovine P23H rhodopsin mutants expressed heterologously in cells were examined. The aggregation properties and cellular localization of the mutant receptors were determined by Förster resonance energy transfer and confocal microscopy. The potential therapeutic effects of the pharmacological compounds 9-cis retinal and metformin were also examined. Human and bovine P23H rhodopsin mutants exhibited different aggregation properties and responses to the pharmacological compounds tested. These observations would lead to different predictions on the severity of the phenotype and divergent predictions on the benefit of the therapeutic compounds tested. The bovine rhodopsin template does not appear to adequately model the effects of the P23H mutation in the human form of the receptor.
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Affiliation(s)
- Sreelakshmi Vasudevan
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
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6
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Newton F, Megaw R. Mechanisms of Photoreceptor Death in Retinitis Pigmentosa. Genes (Basel) 2020; 11:genes11101120. [PMID: 32987769 PMCID: PMC7598671 DOI: 10.3390/genes11101120] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/15/2020] [Accepted: 09/22/2020] [Indexed: 02/08/2023] Open
Abstract
Retinitis pigmentosa (RP) is the most common cause of inherited blindness and is characterised by the progressive loss of retinal photoreceptors. However, RP is a highly heterogeneous disease and, while much progress has been made in developing gene replacement and gene editing treatments for RP, it is also necessary to develop treatments that are applicable to all causative mutations. Further understanding of the mechanisms leading to photoreceptor death is essential for the development of these treatments. Recent work has therefore focused on the role of apoptotic and non-apoptotic cell death pathways in RP and the various mechanisms that trigger these pathways in degenerating photoreceptors. In particular, several recent studies have begun to elucidate the role of microglia and innate immune response in the progression of RP. Here, we discuss some of the recent progress in understanding mechanisms of rod and cone photoreceptor death in RP and summarise recent clinical trials targeting these pathways.
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Affiliation(s)
- Fay Newton
- MRC Human Genetics Unit, University of Edinburgh, South Bridge, Edinburgh EH8 9YL, UK;
- Correspondence:
| | - Roly Megaw
- MRC Human Genetics Unit, University of Edinburgh, South Bridge, Edinburgh EH8 9YL, UK;
- Princess Alexandra Eye Pavilion, NHS Lothian, Edinburgh EH3 9HA, UK
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7
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Liu X, Feng B, Vats A, Tang H, Seibel W, Swaroop M, Tawa G, Zheng W, Byrne L, Schurdak M, Chen Y. Pharmacological clearance of misfolded rhodopsin for the treatment of RHO-associated retinitis pigmentosa. FASEB J 2020; 34:10146-10167. [PMID: 32536017 DOI: 10.1096/fj.202000282r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 05/07/2020] [Accepted: 05/15/2020] [Indexed: 01/20/2023]
Abstract
Rhodopsin mutation and misfolding is a common cause of autosomal dominant retinitis pigmentosa (RP). Using a luciferase reporter assay, we undertook a small-molecule high-throughput screening (HTS) of 68, 979 compounds and identified nine compounds that selectively reduced the misfolded P23H rhodopsin without an effect on the wild type (WT) rhodopsin protein. Further, we found five of these compounds, including methotrexate (MTX), promoted P23H rhodopsin degradation that also cleared out other misfolded rhodopsin mutant proteins. We showed MTX increased P23H rhodopsin degradation via the lysosomal but not the proteasomal pathway. Importantly, one intravitreal injection (IVI) of 25 pmol MTX increased electroretinogram (ERG) response and rhodopsin level in the retinae of RhoP23H/+ knock-in mice at 1 month of age. Additionally, four weekly IVIs increased the photoreceptor cell number in the retinae of RhoP23H/+ mice compared to vehicle control. Our study indicates a therapeutic potential of repurposing MTX for the treatment of rhodopsin-associated RP.
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Affiliation(s)
- Xujie Liu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bing Feng
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Abhishek Vats
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hong Tang
- Drug Discovery Center, University of Cincinnati, Cincinnati, OH, USA
| | - William Seibel
- Drug Discovery Center, University of Cincinnati, Cincinnati, OH, USA.,Oncology Department, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Manju Swaroop
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Gregory Tawa
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Wei Zheng
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Leah Byrne
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mark Schurdak
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yuanyuan Chen
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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8
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Ahmed CM, Dwyer BT, Romashko A, Van Adestine S, Park EH, Lou Z, Welty D, Josiah S, Savinainen A, Zhang B, Lewin AS. SRD005825 Acts as a Pharmacologic Chaperone of Opsin and Promotes Survival of Photoreceptors in an Animal Model of Autosomal Dominant Retinitis Pigmentosa. Transl Vis Sci Technol 2019; 8:30. [PMID: 31857914 PMCID: PMC6910612 DOI: 10.1167/tvst.8.6.30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 10/11/2019] [Indexed: 01/17/2023] Open
Abstract
Purpose Mutations in RHO, the gene for a rhodopsin, are a leading cause of autosomal dominant retinitis pigmentosa. The objective of this study was to determine if a synthetic retinal analogue (SRD005825) serves as a pharmacologic chaperone to promote appropriate membrane trafficking of a mutant version of human rhodopsin. Methods A tetracycline-inducible cell line was used to produce human wild-type and T17M opsin. A cell-free assay was used to study the impact of SRD005825 on binding of 9-cis-retinal to wild-type opsin. A cell-based assay was used to measure the effect of SRD005825 on the generation of rhodopsin by spectroscopy and Western blot and the transport of rhodopsin to the cell membrane by confocal microscopy. Mice bearing T17M RHO were treated with daily oral doses of SRD005825, and retinal degeneration was measured by spectral-domain optical coherence tomography and, at the conclusion of the experiment, by electroretinography and morphometry. Results SRD005825 competed with 9-cis-retinal for binding to wild-type opsin but promoted the formation of rhodopsin in HEK293 cells and the trafficking of T17M rhodopsin to the plasma membrane of these cells. T17M transgenic mice exhibited rapid retinal degeneration, but thinning of the outer nuclear layer representative of photoreceptor cell bodies was delayed by treatment with SRD005825. Electroretinography a-wave and b-wave amplitudes were significantly improved by drug treatment. Conclusions SRD005825 promoted the reconstitution of mutant rhodopsin and its membrane localization. Because it delayed retinal degeneration in the mouse model, it has potential as a therapeutic for autosomal dominant retinitis pigmentosa. Translational Relevance SRD005825 may be useful as a treatment to delay retinal degeneration in retinitis pigmentosa patients with rhodopsin mutations causing misfolding of the protein.
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Affiliation(s)
- Chulbul M Ahmed
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA
| | - Brian T Dwyer
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - All Romashko
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | | | - Eun-He Park
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Zhe Lou
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Devi Welty
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Seren Josiah
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Annel Savinainen
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Bohon Zhang
- Shire HGT Inc., a member of the Takeda group of companies, Cambridge, MA, USA
| | - Alfred S Lewin
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA
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9
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Wang J, Xu D, Zhu T, Zhou Y, Chen X, Wang F, Zhang J, Tian H, Gao F, Zhang J, Jin C, Xu J, Lu L, Liu Q, Xu GT. Identification of two novel RHO mutations in Chinese retinitis pigmentosa patients. Exp Eye Res 2019; 188:107726. [DOI: 10.1016/j.exer.2019.107726] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 11/29/2022]
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10
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Scott BM, Wybenga-Groot LE, McGlade CJ, Heon E, Peisajovich SG, Chang BSW. Screening of Chemical Libraries Using a Yeast Model of Retinal Disease. SLAS DISCOVERY 2019; 24:969-977. [PMID: 31556794 DOI: 10.1177/2472555219875934] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Retinitis pigmentosa (RP) is a degenerative retinal disease, often caused by mutations in the G-protein-coupled receptor rhodopsin. The majority of pathogenic rhodopsin mutations cause rhodopsin to misfold, including P23H, disrupting its crucial ability to respond to light. Previous screens to discover pharmacological chaperones of rhodopsin have primarily been based on rescuing rhodopsin trafficking and localization to the plasma membrane. Here, we present methods utilizing a yeast-based assay to screen for compounds that rescue the ability of rhodopsin to activate an associated downstream G-protein signaling cascade. We engineered a yeast strain in which human rhodopsin variants were genomically integrated, and were able to demonstrate functional coupling to the yeast mating pathway, leading to fluorescent protein expression. We confirmed that a known pharmacological chaperone, 9-cis retinal, could partially rescue light-dependent activation of a disease-associated rhodopsin mutation (P23H) expressed in yeast. These novel yeast strains were used to perform a phenotypic screen of 4280 compounds from the LOPAC1280 library and a peptidomimetic library, to discover novel pharmacological chaperones of rhodopsin. The fluorescence-based assay was robust in a 96-well format, with a Z' factor of 0.65 and a signal-to-background ratio of above 14. One compound was selected for additional analysis, but it did not appear to rescue rhodopsin function in yeast. The methods presented here are amenable to future screens of small-molecule libraries, as they are robust and cost-effective. We also discuss how these methods could be further modified or adapted to perform screens of more compounds in the future.
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Affiliation(s)
- Benjamin M Scott
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.,Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.,Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | | | - C Jane McGlade
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.,Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Elise Heon
- Department of Ophthalmology and Vision Science, The Hospital for Sick Children, Toronto, ON, Canada
| | - Sergio G Peisajovich
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Belinda S W Chang
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, ON, Canada
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11
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Park PSH. Rhodopsin Oligomerization and Aggregation. J Membr Biol 2019; 252:413-423. [PMID: 31286171 DOI: 10.1007/s00232-019-00078-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 06/25/2019] [Indexed: 12/18/2022]
Abstract
Rhodopsin is the light receptor in photoreceptor cells of the retina and a prototypical G protein-coupled receptor. Two types of quaternary structures can be adopted by rhodopsin. If rhodopsin folds and attains a proper tertiary structure, it can then form oligomers and nanodomains within the photoreceptor cell membrane. In contrast, if rhodopsin misfolds, it cannot progress through the biosynthetic pathway and instead will form aggregates that can cause retinal degenerative disease. In this review, emerging views are highlighted on the supramolecular organization of rhodopsin within the membrane of photoreceptor cells and the aggregation of rhodopsin that can lead to retinal degeneration.
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Affiliation(s)
- Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
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12
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Wan A, Place E, Pierce EA, Comander J. Characterizing variants of unknown significance in rhodopsin: A functional genomics approach. Hum Mutat 2019; 40:1127-1144. [PMID: 30977563 PMCID: PMC7027811 DOI: 10.1002/humu.23762] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 03/31/2019] [Accepted: 04/08/2019] [Indexed: 01/19/2023]
Abstract
Characterizing the pathogenicity of DNA sequence variants of unknown significance (VUS) is a major bottleneck in human genetics, and is increasingly important in determining which patients with inherited retinal diseases could benefit from gene therapy. A library of 210 rhodopsin (RHO) variants from literature and in‐house genetic diagnostic testing were created to efficiently detect pathogenic RHO variants that fail to express on the cell surface. This study, while focused on RHO, demonstrates a streamlined, generalizable method for detecting pathogenic VUS. A relatively simple next‐generation sequencing‐based readout was developed so that a flow cytometry‐based assay could be performed simultaneously on all variants in a pooled format, without the need for barcodes or viral transduction. The resulting dataset characterized the surface expression of every RHO library variant with a high degree of reproducibility (r2 = 0.92–0.95), recategorizing 37 variants. For example, three retinitis pigmentosa pedigrees were solved by identifying VUS which showed low expression levels (p.G18D, p.G101V, and p.P180T). Results were validated across multiple assays and correlated with clinical disease severity. This study presents a parallelized, higher‐throughput cell‐based assay for the functional characterization of VUS in RHO, and can be applied more broadly to other inherited retinal disease genes and other disorders.
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Affiliation(s)
- Aliete Wan
- Department of Ophthalmology, Ocular Genomics Institute, Berman-Gund Laboratory for the Study of Retinal Degenerations, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts
| | - Emily Place
- Department of Ophthalmology, Ocular Genomics Institute, Berman-Gund Laboratory for the Study of Retinal Degenerations, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts
| | - Eric A Pierce
- Department of Ophthalmology, Ocular Genomics Institute, Berman-Gund Laboratory for the Study of Retinal Degenerations, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts
| | - Jason Comander
- Department of Ophthalmology, Ocular Genomics Institute, Berman-Gund Laboratory for the Study of Retinal Degenerations, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts
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13
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Mitchell J, Balem F, Tirupula K, Man D, Dhiman HK, Yanamala N, Ollesch J, Planas-Iglesias J, Jennings BJ, Gerwert K, Iannaccone A, Klein-Seetharaman J. Comparison of the molecular properties of retinitis pigmentosa P23H and N15S amino acid replacements in rhodopsin. PLoS One 2019; 14:e0214639. [PMID: 31100078 PMCID: PMC6524802 DOI: 10.1371/journal.pone.0214639] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 03/19/2019] [Indexed: 12/16/2022] Open
Abstract
Mutations in the RHO gene encoding for the visual pigment protein, rhodopsin, are among the most common cause of autosomal dominant retinitis pigmentosa (ADRP). Previous studies of ADRP mutations in different domains of rhodopsin have indicated that changes that lead to more instability in rhodopsin structure are responsible for more severe disease in patients. Here, we further test this hypothesis by comparing side-by-side and therefore quantitatively two RHO mutations, N15S and P23H, both located in the N-terminal intradiscal domain. The in vitro biochemical properties of these two rhodopsin proteins, expressed in stably transfected tetracycline-inducible HEK293S cells, their UV-visible absorption, their Fourier transform infrared, circular dichroism and Metarhodopsin II fluorescence spectroscopy properties were characterized. As compared to the severely impaired P23H molecular function, N15S is only slightly defective in structure and stability. We propose that the molecular basis for these structural differences lies in the greater distance of the N15 residue as compared to P23 with respect to the predicted rhodopsin folding core. As described previously for WT rhodopsin, addition of the cytoplasmic allosteric modulator chlorin e6 stabilizes especially the P23H protein, suggesting that chlorin e6 may be generally beneficial in the rescue of those ADRP rhodopsin proteins whose stability is affected by amino acid replacement.
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Affiliation(s)
- James Mitchell
- Division of Biomedical Sciences, Medical School, University of Warwick, Coventry, United Kingdom
| | - Fernanda Balem
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Kalyan Tirupula
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - David Man
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Harpreet Kaur Dhiman
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Naveena Yanamala
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Julian Ollesch
- Department of Biophysics, Ruhr-University Bochum, Bochum, Germany
| | - Joan Planas-Iglesias
- Division of Biomedical Sciences, Medical School, University of Warwick, Coventry, United Kingdom
| | - Barbara J Jennings
- Retinal Degeneration & Ophthalmic Genetics Service & Lions Visual Function Diagnostic Lab, Hamilton Eye Institute, Dept. Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Klaus Gerwert
- Department of Biophysics, Ruhr-University Bochum, Bochum, Germany
| | - Alessandro Iannaccone
- Retinal Degeneration & Ophthalmic Genetics Service & Lions Visual Function Diagnostic Lab, Hamilton Eye Institute, Dept. Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Judith Klein-Seetharaman
- Division of Biomedical Sciences, Medical School, University of Warwick, Coventry, United Kingdom
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
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14
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Salom D, Jin H, Gerken TA, Yu C, Huang L, Palczewski K. Human red and green cone opsins are O-glycosylated at an N-terminal Ser/Thr-rich domain conserved in vertebrates. J Biol Chem 2019; 294:8123-8133. [PMID: 30948514 DOI: 10.1074/jbc.ra118.006835] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/15/2019] [Indexed: 12/28/2022] Open
Abstract
There are fundamental differences in the structures of outer segments between rod and cone photoreceptor cells in the vertebrate retina. Visual pigments are the only essential membrane proteins that differ between rod and cone outer segments, making it likely that they contribute to these structural differences. Human rhodopsin is N-glycosylated on Asn2 and Asn15, whereas human (h) red and green cone opsins (hOPSR and hOPSG, respectively) are N-glycosylated at Asn34 Here, utilizing a monoclonal antibody (7G8 mAB), we demonstrate that hOPSR and hOPSG from human retina also are O-glycosylated with full occupancy. We determined that 7G8 mAB recognizes the N-terminal sequence 21DSTQSSIF28 of hOPSR and hOPSG from extracts of human retina, but only after their O-glycans have been removed with O-glycosidase treatment, thus revealing this post-translational modification of red and green cone opsins. In addition, we show that hOPSR and hOPSG from human retina are recognized by jacalin, a lectin that binds to O-glycans, preferentially to Gal-GalNAc. Next, we confirmed the presence of O-glycans on OPSR and OPSG from several vertebrate species, including mammals, birds, and amphibians. Finally, the analysis of bovine OPSR by MS identified an O-glycan on Ser22, a residue that is semi-conserved (Ser or Thr) among vertebrate OPSR and OPSG. These results suggest that O-glycosylation is a fundamental feature of red and green cone opsins, which may be relevant to their function or to cone cell development, and that differences in this post-translational modification also could contribute to the different morphologies of rod and cone photoreceptors.
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Affiliation(s)
- David Salom
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, Irvine, California 92697; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106.
| | - Hui Jin
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Thomas A Gerken
- Department of Biochemistry and Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Clinton Yu
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697
| | - Lan Huang
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, Irvine, California 92697; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106.
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15
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Wang W, Guo DY, Tao YX. Therapeutic strategies for diseases caused by loss-of-function mutations in G protein-coupled receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2019; 161:181-210. [DOI: 10.1016/bs.pmbts.2018.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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16
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Coupling of Human Rhodopsin to a Yeast Signaling Pathway Enables Characterization of Mutations Associated with Retinal Disease. Genetics 2018; 211:597-615. [PMID: 30514708 DOI: 10.1534/genetics.118.301733] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 11/29/2018] [Indexed: 12/24/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are crucial sensors of extracellular signals in eukaryotes, with multiple GPCR mutations linked to human diseases. With the growing number of sequenced human genomes, determining the pathogenicity of a mutation is challenging, but can be aided by a direct measurement of GPCR-mediated signaling. This is particularly difficult for the visual pigment rhodopsin-a GPCR activated by light-for which hundreds of mutations have been linked to inherited degenerative retinal diseases such as retinitis pigmentosa. In this study, we successfully engineered, for the first time, activation by human rhodopsin of the yeast mating pathway, resulting in signaling via a fluorescent reporter. We combine this novel assay for rhodopsin light-dependent activation with studies of subcellular localization, and the upregulation of the unfolded protein response in response to misfolded rhodopsin protein. We use these assays to characterize a panel of rhodopsin mutations with known molecular phenotypes, finding that rhodopsin maintains a similar molecular phenotype in yeast, with some interesting differences. Furthermore, we compare our assays in yeast with clinical phenotypes from patients with novel disease-linked mutations. We demonstrate that our engineered yeast strain can be useful in rhodopsin mutant classification, and in helping to determine the molecular mechanisms underlying their pathogenicity. This approach may also be applied to better understand the clinical relevance of other human GPCR mutations, furthering the use of yeast as a tool for investigating molecular mechanisms relevant to human disease.
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17
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Gragg M, Park PSH. Misfolded rhodopsin mutants display variable aggregation properties. Biochim Biophys Acta Mol Basis Dis 2018; 1864:2938-2948. [PMID: 29890221 PMCID: PMC6066411 DOI: 10.1016/j.bbadis.2018.06.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 05/31/2018] [Accepted: 06/06/2018] [Indexed: 11/20/2022]
Abstract
The largest class of rhodopsin mutations causing autosomal dominant retinitis pigmentosa (adRP) is mutations that lead to misfolding and aggregation of the receptor. The misfolding mutants have been characterized biochemically, and categorized as either partial or complete misfolding mutants. This classification is incomplete and does not provide sufficient information to fully understand the disease pathogenesis and evaluate therapeutic strategies. A Förster resonance energy transfer (FRET) method was utilized to directly assess the aggregation properties of misfolding rhodopsin mutants within the cell. Partial (P23H and P267L) and complete (G188R, H211P, and P267R) misfolding mutants were characterized to reveal variability in aggregation properties. The complete misfolding mutants all behaved similarly, forming aggregates when expressed alone, minimally interacting with the wild-type receptor when coexpressed, and were unresponsive to treatment with the pharmacological chaperone 9-cis retinal. In contrast, variability was observed between the partial misfolding mutants. In the opsin form, the P23H mutant behaved similarly as the complete misfolding mutants. In contrast, the opsin form of the P267L mutant existed as both aggregates and oligomers when expressed alone and formed mostly oligomers with the wild-type receptor when coexpressed. The partial misfolding mutants both reacted similarly to the pharmacological chaperone 9-cis retinal, displaying improved folding and oligomerization when expressed alone but aggregating with wild-type receptor when coexpressed. The observed differences in aggregation properties and effect of 9-cis retinal predict different outcomes in disease pathophysiology and suggest that retinoid-based chaperones will be ineffective or even detrimental.
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Affiliation(s)
- Megan Gragg
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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18
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Athanasiou D, Aguila M, Bellingham J, Li W, McCulley C, Reeves PJ, Cheetham ME. The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy. Prog Retin Eye Res 2018; 62:1-23. [PMID: 29042326 PMCID: PMC5779616 DOI: 10.1016/j.preteyeres.2017.10.002] [Citation(s) in RCA: 213] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 10/03/2017] [Accepted: 10/13/2017] [Indexed: 12/12/2022]
Abstract
Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP). Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP). Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity. The in-depth characterisation of many rhodopsin mutations has revealed that there are distinct consequences on the protein structure and function associated with different mutations. Here we categorise rhodopsin mutations into seven discrete classes; with defects ranging from misfolding and disruption of proteostasis, through mislocalisation and disrupted intracellular traffic to instability and altered function. Rhodopsin adRP offers a unique paradigm to understand how disturbances in photoreceptor homeostasis can lead to neuronal cell death. Furthermore, a wide range of therapies have been tested in rhodopsin RP, from gene therapy and gene editing to pharmacological interventions. The understanding of the disease mechanisms associated with rhodopsin RP and the development of targeted therapies offer the potential of treatment for this currently untreatable neurodegeneration.
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Affiliation(s)
| | - Monica Aguila
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - James Bellingham
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Wenwen Li
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Caroline McCulley
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Philip J Reeves
- School of Biological Sciences, University of Essex, Wivenhoe Park, Essex CO4 3SQ, UK.
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19
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Flavonoid allosteric modulation of mutated visual rhodopsin associated with retinitis pigmentosa. Sci Rep 2017; 7:11167. [PMID: 28894166 PMCID: PMC5593859 DOI: 10.1038/s41598-017-11391-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/22/2017] [Indexed: 11/08/2022] Open
Abstract
Dietary flavonoids exhibit many biologically-relevant functions and can potentially have beneficial effects in the treatment of pathological conditions. In spite of its well known antioxidant properties, scarce structural information is available on the interaction of flavonoids with membrane receptors. Advances in the structural biology of a specific class of membrane receptors, the G protein-coupled receptors, have significantly increased our understanding of drug action and paved the way for developing improved therapeutic approaches. We have analyzed the effect of the flavonoid quercetin on the conformation, stability and function of the G protein-coupled receptor rhodopsin, and the G90V mutant associated with the retinal degenerative disease retinitis pigmentosa. By using a combination of experimental and computational methods, we suggest that quercetin can act as an allosteric modulator of opsin regenerated with 9-cis-retinal and more importantly, that this binding has a positive effect on the stability and conformational properties of the G90V mutant associated with retinitis pigmentosa. These results open new possibilities to use quercetin and other flavonoids, in combination with specific retinoids like 9-cis-retinal, for the treatment of retinal degeneration associated with retinitis pigmentosa. Moreover, the use of flavonoids as allosteric modulators may also be applicable to other members of the G protein-coupled receptors superfamily.
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20
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Krebs MP, Collin GB, Hicks WL, Yu M, Charette JR, Shi LY, Wang J, Naggert JK, Peachey NS, Nishina PM. Mouse models of human ocular disease for translational research. PLoS One 2017; 12:e0183837. [PMID: 28859131 PMCID: PMC5578669 DOI: 10.1371/journal.pone.0183837] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 08/12/2017] [Indexed: 01/24/2023] Open
Abstract
Mouse models provide a valuable tool for exploring pathogenic mechanisms underlying inherited human disease. Here, we describe seven mouse models identified through the Translational Vision Research Models (TVRM) program, each carrying a new allele of a gene previously linked to retinal developmental and/or degenerative disease. The mutations include four alleles of three genes linked to human nonsyndromic ocular diseases (Aipl1tvrm119, Aipl1tvrm127, Rpgrip1tvrm111, RhoTvrm334) and three alleles of genes associated with human syndromic diseases that exhibit ocular phentoypes (Alms1tvrm102, Clcn2nmf289, Fkrptvrm53). Phenotypic characterization of each model is provided in the context of existing literature, in some cases refining our current understanding of specific disease attributes. These murine models, on fixed genetic backgrounds, are available for distribution upon request and may be useful for understanding the function of the gene in the retina, the pathological mechanisms induced by its disruption, and for testing experimental approaches to treat the corresponding human ocular diseases.
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Affiliation(s)
- Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Wanda L. Hicks
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Minzhong Yu
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
| | | | - Lan Ying Shi
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Neal S. Peachey
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States of America
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
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21
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Sanchez-Reyes OB, Cooke ALG, Tranter DB, Rashid D, Eilers M, Reeves PJ, Smith SO. G Protein-Coupled Receptors Contain Two Conserved Packing Clusters. Biophys J 2017; 112:2315-2326. [PMID: 28591604 DOI: 10.1016/j.bpj.2017.04.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 04/24/2017] [Accepted: 04/28/2017] [Indexed: 01/01/2023] Open
Abstract
G protein-coupled receptors (GPCRs) have evolved a seven-transmembrane helix framework that is responsive to a wide range of extracellular signals. An analysis of the interior packing of family A GPCR crystal structures reveals two clusters of highly packed residues that facilitate tight transmembrane helix association. These clusters are centered on amino acid positions 2.47 and 4.53, which are highly conserved as alanine and serine, respectively. Ala2.47 mediates the interaction between helices H1 and H2, while Ser4.53 mediates the interaction between helices H3 and H4. The helical interfaces outside of these clusters are lined with residues that are more loosely packed, a structural feature that facilitates motion of helices H5, H6, and H7, which is required for receptor activation. Mutation of the conserved small side chain at position 4.53 within packing cluster 2 is shown to disrupt the structure of the visual receptor rhodopsin, whereas sites in packing cluster 1 (e.g., positions 1.46 and 2.47) are more tolerant to mutation but affect the overall stability of the protein. These findings reveal a common structural scaffold of GPCRs that is important for receptor folding and activation.
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Affiliation(s)
- Omar B Sanchez-Reyes
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Aidan L G Cooke
- School of Biological Sciences, University of Essex, Essex, United Kingdom
| | - Dale B Tranter
- School of Biological Sciences, University of Essex, Essex, United Kingdom
| | - Dawood Rashid
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Markus Eilers
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Philip J Reeves
- School of Biological Sciences, University of Essex, Essex, United Kingdom.
| | - Steven O Smith
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
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22
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Sandoval A, Eichler S, Madathil S, Reeves PJ, Fahmy K, Böckmann RA. The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs. Biophys J 2017; 111:79-89. [PMID: 27410736 DOI: 10.1016/j.bpj.2016.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 05/31/2016] [Accepted: 06/08/2016] [Indexed: 10/21/2022] Open
Abstract
The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu(134) in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu(134)- and Gln(134)-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface.
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Affiliation(s)
- Angelica Sandoval
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Stefanie Eichler
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, and Technische Universität Dresden, Dresden, Germany
| | - Sineej Madathil
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Philip J Reeves
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Karim Fahmy
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, and Technische Universität Dresden, Dresden, Germany.
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
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23
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Morrow JM, Castiglione GM, Dungan SZ, Tang PL, Bhattacharyya N, Hauser FE, Chang BSW. An experimental comparison of human and bovine rhodopsin provides insight into the molecular basis of retinal disease. FEBS Lett 2017; 591:1720-1731. [PMID: 28369862 DOI: 10.1002/1873-3468.12637] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/22/2017] [Accepted: 03/25/2017] [Indexed: 11/05/2022]
Abstract
Rhodopsin is the visual pigment that mediates dim-light vision in vertebrates and is a model system for the study of retinal disease. The majority of rhodopsin experiments are performed using bovine rhodopsin; however, recent evidence suggests that significant functional differences exist among mammalian rhodopsins. In this study, we identify differences in both thermal decay and light-activated retinal release rates between bovine and human rhodopsin and perform mutagenesis studies to highlight two clusters of substitutions that contribute to these differences. We also demonstrate that the retinitis pigmentosa-associated mutation G51A behaves differently in human rhodopsin compared to bovine rhodopsin and determine that the thermal decay rate of an ancestrally reconstructed mammalian rhodopsin displays an intermediate phenotype compared to the two extant pigments.
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Affiliation(s)
- James M Morrow
- Department of Cell and Systems Biology, University of Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Canada
| | | | - Sarah Z Dungan
- Department of Ecology and Evolutionary Biology, University of Toronto, Canada
| | - Portia L Tang
- Department of Cell and Systems Biology, University of Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Canada
| | | | - Frances E Hauser
- Department of Ecology and Evolutionary Biology, University of Toronto, Canada
| | - Belinda S W Chang
- Department of Cell and Systems Biology, University of Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Canada.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, Canada
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24
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Athanasiou D, Aguila M, Opefi CA, South K, Bellingham J, Bevilacqua D, Munro PM, Kanuga N, Mackenzie FE, Dubis AM, Georgiadis A, Graca AB, Pearson RA, Ali RR, Sakami S, Palczewski K, Sherman MY, Reeves PJ, Cheetham ME. Rescue of mutant rhodopsin traffic by metformin-induced AMPK activation accelerates photoreceptor degeneration. Hum Mol Genet 2017; 26:305-319. [PMID: 28065882 PMCID: PMC5351934 DOI: 10.1093/hmg/ddw387] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 11/04/2016] [Accepted: 11/05/2016] [Indexed: 01/29/2023] Open
Abstract
Protein misfolding caused by inherited mutations leads to loss of protein function and potentially toxic 'gain of function', such as the dominant P23H rhodopsin mutation that causes retinitis pigmentosa (RP). Here, we tested whether the AMPK activator metformin could affect the P23H rhodopsin synthesis and folding. In cell models, metformin treatment improved P23H rhodopsin folding and traffic. In animal models of P23H RP, metformin treatment successfully enhanced P23H traffic to the rod outer segment, but this led to reduced photoreceptor function and increased photoreceptor cell death. The metformin-rescued P23H rhodopsin was still intrinsically unstable and led to increased structural instability of the rod outer segments. These data suggest that improving the traffic of misfolding rhodopsin mutants is unlikely to be a practical therapy, because of their intrinsic instability and long half-life in the outer segment, but also highlights the potential of altering translation through AMPK to improve protein function in other protein misfolding diseases.
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Affiliation(s)
| | - Monica Aguila
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
| | - Chikwado A. Opefi
- School of Biological Sciences, University of Essex, Wivenhoe Park, Essex, UK
| | - Kieron South
- School of Biological Sciences, University of Essex, Wivenhoe Park, Essex, UK
| | | | | | - Peter M. Munro
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
| | - Naheed Kanuga
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
| | | | - Adam M. Dubis
- Moorfields Eye Hospital NHS Trust, 162 City Road, London, UK
| | | | - Anna B. Graca
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
| | | | - Robin R. Ali
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
| | - Sanae Sakami
- Department of Pharmacology, and Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, and Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, USA
| | - Michael Y. Sherman
- Department of Biochemistry, Boston University Medical School, Boston, Massachusetts, MA, USA
| | - Philip J. Reeves
- School of Biological Sciences, University of Essex, Wivenhoe Park, Essex, UK
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25
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Parfitt DA, Cheetham ME. Targeting the Proteostasis Network in Rhodopsin Retinitis Pigmentosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:479-84. [PMID: 26427449 DOI: 10.1007/978-3-319-17121-0_64] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Mutations in rhodopsin are one of the most common causes of retinitis pigmentosa (RP). Misfolding of rhodopsin can result in disruptions in cellular protein homeostasis, or proteostasis. There is currently no available treatment for RP. In this review, we discuss the different approaches currently being investigated for treatment of rhodopsin RP, focusing on the potential of manipulation of the proteostasis network as a therapeutic approach to combat retinal degeneration.
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Affiliation(s)
- David A Parfitt
- Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, 11-43 Bath Street, EC1V 9EL, London, UK.
| | - Michael E Cheetham
- Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, 11-43 Bath Street, EC1V 9EL, London, UK.
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26
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Fernández-Sampedro MA, Invergo BM, Ramon E, Bertranpetit J, Garriga P. Functional role of positively selected amino acid substitutions in mammalian rhodopsin evolution. Sci Rep 2016; 6:21570. [PMID: 26865329 PMCID: PMC4749998 DOI: 10.1038/srep21570] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 01/27/2016] [Indexed: 12/22/2022] Open
Abstract
Visual rhodopsins are membrane proteins that function as light photoreceptors in the vertebrate retina. Specific amino acids have been positively selected in visual pigments during mammal evolution, which, as products of adaptive selection, would be at the base of important functional innovations. We have analyzed the top candidates for positive selection at the specific amino acids and the corresponding reverse changes (F13M, Q225R and A346S) in order to unravel the structural and functional consequences of these important sites in rhodopsin evolution. We have constructed, expressed and immunopurified the corresponding mutated pigments and analyzed their molecular phenotypes. We find that position 13 is very important for the folding of the receptor and also for proper protein glycosylation. Position 225 appears to be important for the function of the protein affecting the G-protein activation process, and position 346 would also regulate functionality of the receptor by enhancing G-protein activation and presumably affecting protein phosphorylation by rhodopsin kinase. Our results represent a link between the evolutionary analysis, which pinpoints the specific amino acid positions in the adaptive process, and the structural and functional analysis, closer to the phenotype, making biochemical sense of specific selected genetic sequences in rhodopsin evolution.
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Affiliation(s)
- Miguel A Fernández-Sampedro
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Brandon M Invergo
- IBE - Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), CEXS-UPF-PRBB, Barcelona, Catalonia, Spain
| | - Eva Ramon
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Jaume Bertranpetit
- IBE - Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), CEXS-UPF-PRBB, Barcelona, Catalonia, Spain
| | - Pere Garriga
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
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27
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Comparative sequence analyses of rhodopsin and RPE65 reveal patterns of selective constraint across hereditary retinal disease mutations. Vis Neurosci 2016; 33:e002. [DOI: 10.1017/s0952523815000322] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractRetinitis pigmentosa (RP) comprises several heritable diseases that involve photoreceptor, and ultimately retinal, degeneration. Currently, mutations in over 50 genes have known links to RP. Despite advances in clinical characterization, molecular characterization of RP remains challenging due to the heterogeneous nature of causal genes, mutations, and clinical phenotypes. In this study, we compiled large datasets of two important visual genes associated with RP: rhodopsin, which initiates the phototransduction cascade, and the retinoid isomerase RPE65, which regenerates the visual cycle. We used a comparative evolutionary approach to investigate the relationship between interspecific sequence variation and pathogenic mutations that lead to degenerative retinal disease. Using codon-based likelihood methods, we estimated evolutionary rates (dN/dS) across both genes in a phylogenetic context to investigate differences between pathogenic and nonpathogenic amino acid sites. In both genes, disease-associated sites showed significantly lower evolutionary rates compared to nondisease sites, and were more likely to occur in functionally critical areas of the proteins. The nature of the dataset (e.g., vertebrate or mammalian sequences), as well as selection of pathogenic sites, affected the differences observed between pathogenic and nonpathogenic sites. Our results illustrate that these methods can serve as an intermediate step in understanding protein structure and function in a clinical context, particularly in predicting the relative pathogenicity (i.e., functional impact) of point mutations and their downstream phenotypic effects. Extensions of this approach may also contribute to current methods for predicting the deleterious effects of candidate mutations and to the identification of protein regions under strong constraint where we expect pathogenic mutations to occur.
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Lys39-Lysophosphatidate Carbonyl Oxygen Interaction Locks LPA1 N-terminal Cap to the Orthosteric Site and partners Arg124 During Receptor Activation. Sci Rep 2015; 5:13343. [PMID: 26268898 PMCID: PMC4542628 DOI: 10.1038/srep13343] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 07/21/2015] [Indexed: 12/21/2022] Open
Abstract
Lysophosphatidic acid (LPA) receptor 1 (LPA1) is a member of the G protein-coupled receptors mediating the biological response to LPA species. Lack of detailed mechanism underlying LPA/LPA1 interaction has hampered the development of specific antagonists. Here, novel N-terminal Lys39 has been identified as a key residue during LPA-type agonist binding and LPA1 activation. Analysis of the molecular dynamics (MD) trajectories showed that LPA-type agonist but not VPC-32183 (antagonist) evolved structures with classical GPCR activation signatures such as reduced cytoplasmic transmembrane (TM) 3/TM6 dynamic network, ruptured ionic lock, and formation of a continuous and highly ordered internal water pathway was also observed. In activated state, LPA-type agonists interact with Arg124 (R3.28), Gln125 (Q3.29), Lys294 (K7.36) and a novel N-terminal Lys39. Site-directed mutagenesis showed complete loss of intracellular calcium mobilization in B103 cells expressing R3.28A and Lys39Ala when treated with LPA-type agonists. Structurally, LPA-type agonist via Carbonyl-oxygen/Lys39 interaction facilitated the formation of a hypothetical N-terminal cap tightly packed over LPA1 heptahelical bundle. This packing may represent a key mechanism to distinguish an apo-receptor from bound LPA1.
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Abstract
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Whole human genome sequencing of
individuals is becoming rapid
and inexpensive, enabling new strategies for using personal genome
information to help diagnose, treat, and even prevent human disorders
for which genetic variations are causative or are known to be risk
factors. Many of the exploding number of newly discovered genetic
variations alter the structure, function, dynamics, stability, and/or
interactions of specific proteins and RNA molecules. Accordingly,
there are a host of opportunities for biochemists and biophysicists
to participate in (1) developing tools to allow accurate and sometimes
medically actionable assessment of the potential pathogenicity of
individual variations and (2) establishing the mechanistic linkage
between pathogenic variations and their physiological consequences,
providing a rational basis for treatment or preventive care. In this
review, we provide an overview of these opportunities and their associated
challenges in light of the current status of genomic science and personalized
medicine, the latter often termed precision medicine.
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Affiliation(s)
- Brett M Kroncke
- †Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.,‡Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Carlos G Vanoye
- §Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, United States
| | - Jens Meiler
- ‡Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States.,∥Departments of Chemistry, Pharmacology, and Bioinformatics, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Alfred L George
- §Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, United States
| | - Charles R Sanders
- †Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.,‡Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
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Jiang H, Xiong S, Xia X. Chemical chaperone 4-phenylbutyrate prevents endoplasmic reticulum stress induced by T17M rhodopsin. Cell Biosci 2014; 4:75. [PMID: 25530840 PMCID: PMC4271335 DOI: 10.1186/2045-3701-4-75] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 11/25/2014] [Indexed: 11/30/2022] Open
Abstract
Background Rhodopsin mutations are associated with the autosomal dominant form of retinitis pigmentosa. T17M mutation in rhodopsin predisposes cells to endoplasmic reticulum (ER) stress and induces cell death. This study aimed to examine whether chemical chaperone 4-phenylbutyrate prevents ER stress induced by rhodopsin T17M. Results ARPE-19 cells were transfected with myc-tagged wild-type (WT) and T17M rhodopsin constructs. Turnover of WT and T17M rhodopsin was measured by cycloheximide chase analysis. The activity of ubiquitin-proteasome system was evaluated by GFPU reporter. We found that T17M rhodopsin was misfolded, ubiqutinated and eliminated by ER-associated degradation pathway (ERAD) in ARPE-19 cells. Accumulated T17M rhodopsin induced unfolded protein response, but had no effect on the activity of ubiquitin proteasome system. Moreover, chemical chaperone 4-phenylbutyrate facilitated the turnover of T17M rhodopsin and prevented apoptosis and ER stress induced by T17M rhodopsin. Conclusions Chemical chaperone could attenuate UPR signaling and ER stress induced by T17M rhodopsin and has potential therapeutic significance for retinitis pigmentosa.
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Affiliation(s)
- Haibo Jiang
- Department of Ophthalmology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410078 P.R. China
| | - Siqi Xiong
- Department of Ophthalmology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410078 P.R. China
| | - Xiaobo Xia
- Department of Ophthalmology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410078 P.R. China
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The heat-shock response co-inducer arimoclomol protects against retinal degeneration in rhodopsin retinitis pigmentosa. Cell Death Dis 2014; 5:e1236. [PMID: 24853414 PMCID: PMC4047904 DOI: 10.1038/cddis.2014.214] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/04/2014] [Accepted: 04/09/2014] [Indexed: 01/04/2023]
Abstract
Retinitis pigmentosa (RP) is a group of inherited diseases that cause blindness due to the progressive death of rod and cone photoreceptors in the retina. There are currently no effective treatments for RP. Inherited mutations in rhodopsin, the light-sensing protein of rod photoreceptor cells, are the most common cause of autosomal-dominant RP. The majority of mutations in rhodopsin, including the common P23H substitution, lead to protein misfolding, which is a feature in many neurodegenerative disorders. Previous studies have shown that upregulating molecular chaperone expression can delay disease progression in models of neurodegeneration. Here, we have explored the potential of the heat-shock protein co-inducer arimoclomol to ameliorate rhodopsin RP. In a cell model of P23H rod opsin RP, arimoclomol reduced P23H rod opsin aggregation and improved viability of mutant rhodopsin-expressing cells. In P23H rhodopsin transgenic rat models, pharmacological potentiation of the stress response with arimoclomol improved electroretinogram responses and prolonged photoreceptor survival, as assessed by measuring outer nuclear layer thickness in the retina. Furthermore, treated animal retinae showed improved photoreceptor outer segment structure and reduced rhodopsin aggregation compared with vehicle-treated controls. The heat-shock response (HSR) was activated in P23H retinae, and this was enhanced with arimoclomol treatment. Furthermore, the unfolded protein response (UPR), which is induced in P23H transgenic rats, was also enhanced in the retinae of arimoclomol-treated animals, suggesting that arimoclomol can potentiate the UPR as well as the HSR. These data suggest that pharmacological enhancement of cellular stress responses may be a potential treatment for rhodopsin RP and that arimoclomol could benefit diseases where ER stress is a factor.
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