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Motipally SI, Kolson DR, Guan T, Kolandaivelu S. Aberrant lipid accumulation and retinal pigmental epithelium dysfunction in PRCD-deficient mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.08.584131. [PMID: 38558979 PMCID: PMC10979840 DOI: 10.1101/2024.03.08.584131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Progressive Rod-Cone Degeneration (PRCD) is an integral membrane protein found in photoreceptor outer segment (OS) disc membranes and its function remains unknown. Mutations in Prcd are implicated in Retinitis pigmentosa (RP) in humans and multiple dog breeds. PRCD-deficient models exhibit decreased levels of cholesterol in the plasma. However, potential changes in the retinal cholesterol remain unexplored. In addition, impaired phagocytosis observed in these animal models points to potential deficits in the retinal pigment epithelium (RPE). Here, using a Prcd -/- murine model we investigated the alterations in the retinal cholesterol levels and impairments in the structural and functional integrity of the RPE. Lipidomic and immunohistochemical analyses show a 5-fold increase in the levels of cholesteryl esters (C.Es) and accumulation of neutral lipids in the PRCD-deficient retina, respectively, indicating alterations in total retinal cholesterol. Longitudinal fundus and spectral domain optical coherence tomography (SD-OCT) examinations showed focal lesions and RPE hyperreflectivity. Strikingly, the RPE of Prcd -/- mice exhibited age-related pathological features such as neutral lipid deposits, lipofuscin accumulation, Bruch's membrane (BrM) thickening and drusenoid focal deposits, mirroring an Age-related Macular Degeneration (AMD)-like phenotype. We propose that the extensive lipofuscin accumulation likely impairs lysosomal function, leading to the defective phagocytosis observed in Prcd -/- mice. Our findings support the dysregulation of retinal cholesterol homeostasis in the absence of PRCD. Further, we demonstrate that progressive photoreceptor degeneration in Prcd -/- mice is accompanied by progressive structural and functional deficits in the RPE, which likely exacerbates vision loss over time.
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Rose K, Chen N, Andreev A, Chen J, Kefalov VJ, Chen J. Light regulation of rhodopsin distribution during outer segment renewal in murine rod photoreceptors. Curr Biol 2024; 34:1492-1505.e6. [PMID: 38508186 PMCID: PMC11003846 DOI: 10.1016/j.cub.2024.02.070] [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: 10/26/2023] [Revised: 01/11/2024] [Accepted: 02/28/2024] [Indexed: 03/22/2024]
Abstract
Vision under dim light relies on primary cilia elaborated by rod photoreceptors in the retina. This specialized sensory structure, called the rod outer segment (ROS), comprises hundreds of stacked, membranous discs containing the light-sensitive protein rhodopsin, and the incorporation of new discs into the ROS is essential for maintaining the rod's health and function. ROS renewal appears to be primarily regulated by extrinsic factors (light); however, results vary depending on different model organisms. We generated two independent transgenic mouse lines where rhodopsin's fate is tracked by a fluorescently labeled rhodopsin fusion protein (Rho-Timer) and show that rhodopsin incorporation into nascent ROS discs appears to be regulated by both external lighting cues and autonomous retinal clocks. Live-cell imaging of the ROS isolated from mice exposed to six unique lighting conditions demonstrates that ROS formation occurs in a periodic manner in cyclic light, constant darkness, and artificial light/dark cycles. This alternating bright/weak banding of Rho-Timer along the length of the ROS relates to inhomogeneities in rhodopsin density and potential points of structural weakness. In addition, we reveal that prolonged dim ambient light exposure impacts not only the rhodopsin content of new discs but also that of older discs, suggesting a dynamic interchange of material between new and old discs. Furthermore, we show that rhodopsin incorporation into the ROS is greatly altered in two autosomal recessive retinitis pigmentosa mouse models, potentially contributing to the pathogenesis. Our findings provide insights into how extrinsic (light) and intrinsic (retinal clocks and genetic mutation) factors dynamically regulate mammalian ROS renewal.
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Affiliation(s)
- Kasey Rose
- Zilkha Neurogenetic Institute, Department of Physiology and Neuroscience, Keck School of Medicine of University of Southern California, Los Angeles, CA 90033, USA
| | - Natalie Chen
- Zilkha Neurogenetic Institute, Department of Physiology and Neuroscience, Keck School of Medicine of University of Southern California, Los Angeles, CA 90033, USA
| | - Andrey Andreev
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jiayan Chen
- Zilkha Neurogenetic Institute, Department of Physiology and Neuroscience, Keck School of Medicine of University of Southern California, Los Angeles, CA 90033, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine CA 92697, USA
| | - Jeannie Chen
- Zilkha Neurogenetic Institute, Department of Physiology and Neuroscience, Keck School of Medicine of University of Southern California, Los Angeles, CA 90033, USA.
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3
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Garner MA, Hubbard MG, Boitet ER, Hubbard ST, Gade A, Ying G, Jones BW, Baehr W, Gross AK. NUDC is critical for rod photoreceptor function, maintenance, and survival. FASEB J 2024; 38:e23518. [PMID: 38441532 PMCID: PMC10917122 DOI: 10.1096/fj.202301641rr] [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: 08/11/2023] [Revised: 01/31/2024] [Accepted: 02/14/2024] [Indexed: 03/07/2024]
Abstract
NUDC (nuclear distribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (rNudC-/- ). Loss of NUDC in rods led to complete photoreceptor cell death at 6 weeks of age. By 3 weeks of age, rNudC-/- function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of rNudC-/- by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. The absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.
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Affiliation(s)
- Mary Anne Garner
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
| | - Meredith G. Hubbard
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
| | - Evan R. Boitet
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
| | - Seth T. Hubbard
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
| | - Anushree Gade
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
| | - Guoxin Ying
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, 84132 USA
| | - Bryan W. Jones
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, 84132 USA
| | - Wolfgang Baehr
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, 84132 USA
| | - Alecia K. Gross
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
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4
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Wang B, Arbuckle RK, Davoli KA, Clinger OD, Brown R, Sahel JA, Chen Y, Pi S. Compensation of inner retina to early-stage photoreceptor degeneration in a Rho P23H/+ mouse model of retinitis pigmentosa. Exp Eye Res 2024; 240:109826. [PMID: 38340947 PMCID: PMC10940204 DOI: 10.1016/j.exer.2024.109826] [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: 12/01/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/12/2024]
Abstract
Retinitis pigmentosa (RP) is an inherited retinal disorder characterized by the degeneration of photoreceptors. RhoP23H/+ mice, which carry a Pro23His mutation in the RHODOPSIN (Rho) gene, are one of the most studied animal models for RP. However, except for the photoreceptors, other retinal neural cells have not been fully investigated in this model. Here, we record the temporal changes of the retina by optical coherence tomography (OCT) imaging of the RhoP23H/+ mice, from early to mid-phase of retinal degeneration. Based on thickness analysis, we identified a natural retinal thickness adaption in wild-type mice during early adulthood and observed morphological compensation of the inner retina layer to photoreceptor degeneration in the RhoP23H/+ mice, primarily on the inner nuclear layer (INL). RhoP23H/+ mice findings were further validated via: histology showing the negative correlation of INL and ONL thicknesses; as well as electroretinogram (ERG) showing an increased b-wave to a-wave ratio. These results unravel the sequential morphologic events in this model and suggest a better understanding of retinal degeneration of RP for future studies.
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Affiliation(s)
- Bingjie Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Riley K Arbuckle
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA, 15213, USA
| | - Katherine A Davoli
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Owen D Clinger
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Richard Brown
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - José-Alain Sahel
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Yuanyuan Chen
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, 15213, USA.
| | - Shaohua Pi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, 15213, USA; UPMC Vision Institute, University of Pittsburgh, Pittsburgh, PA, 15213, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, 15213, USA.
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5
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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Super-resolution mapping in rod photoreceptors identifies rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway. PLoS Biol 2024; 22:e3002467. [PMID: 38190419 PMCID: PMC10773939 DOI: 10.1371/journal.pbio.3002467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 12/10/2023] [Indexed: 01/10/2024] Open
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient phototransduction and vision. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane, at the surface, in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
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6
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Lewis TR, Makia MS, Castillo CM, Hao Y, Al-Ubaidi MR, Skiba NP, Conley SM, Arshavsky VY, Naash MI. ROM1 is redundant to PRPH2 as a molecular building block of photoreceptor disc rims. eLife 2023; 12:RP89444. [PMID: 37991486 PMCID: PMC10665016 DOI: 10.7554/elife.89444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2023] Open
Abstract
Visual signal transduction takes place within a stack of flattened membranous 'discs' enclosed within the light-sensitive photoreceptor outer segment. The highly curved rims of these discs, formed in the process of disc enclosure, are fortified by large hetero-oligomeric complexes of two homologous tetraspanin proteins, PRPH2 (a.k.a. peripherin-2 or rds) and ROM1. While mutations in PRPH2 affect the formation of disc rims, the role of ROM1 remains poorly understood. In this study, we found that the knockout of ROM1 causes a compensatory increase in the disc content of PRPH2. Despite this increase, discs of ROM1 knockout mice displayed a delay in disc enclosure associated with a large diameter and lack of incisures in mature discs. Strikingly, further increasing the level of PRPH2 rescued these morphological defects. We next showed that disc rims are still formed in a knockin mouse in which the tetraspanin body of PRPH2 was replaced with that of ROM1. Together, these results demonstrate that, despite its contribution to the formation of disc rims, ROM1 can be replaced by an excess of PRPH2 for timely enclosure of newly forming discs and establishing normal outer segment structure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
- College of Optometry, University of HoustonHoustonUnited States
| | - Nikolai P Skiba
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma CityUnited States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
- Department of Pharmacology and Cancer Biology, Duke University Medical CenterDurhamUnited States
| | - Muna I Naash
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
- College of Optometry, University of HoustonHoustonUnited States
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7
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Lewis TR, Makia MS, Castillo CM, Hao Y, Al-Ubaidi MR, Skiba NP, Conley SM, Arshavsky VY, Naash MI. ROM1 is redundant to PRPH2 as a molecular building block of photoreceptor disc rims. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.02.547380. [PMID: 37693615 PMCID: PMC10491102 DOI: 10.1101/2023.07.02.547380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Visual signal transduction takes place within a stack of flattened membranous "discs" enclosed within the light-sensitive photoreceptor outer segment. The highly curved rims of these discs, formed in the process of disc enclosure, are fortified by large hetero-oligomeric complexes of two homologous tetraspanin proteins, PRPH2 (a.k.a. peripherin-2 or rds) and ROM1. While mutations in PRPH2 affect the formation of disc rims, the role of ROM1 remains poorly understood. In this study, we found that the knockout of ROM1 causes a compensatory increase in the disc content of PRPH2. Despite this increase, discs of ROM1 knockout mice displayed a delay in disc enclosure associated with a large diameter and lack of incisures in mature discs. Strikingly, further increasing the level of PRPH2 rescued these morphological defects. We next showed that disc rims are still formed in a knockin mouse in which the tetraspanin body of PRPH2 was replaced with that of ROM1. Together, these results demonstrate that, despite its contribution to the formation of disc rims, ROM1 can be replaced by an excess of PRPH2 for timely enclosure of newly forming discs and establishing normal outer segment structure.
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Affiliation(s)
- Tylor R. Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Mustafa S. Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
| | - Carson M. Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Muayyad R. Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
- College of Optometry, University of Houston, Houston, TX, USA, 77204
| | - Nikolai P. Skiba
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA, 73104
| | - Vadim Y. Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Muna I. Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
- College of Optometry, University of Houston, Houston, TX, USA, 77204
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8
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Sun C, Ruzycki PA, Chen S. Rho enhancers play unexpectedly minor roles in Rhodopsin transcription and rod cell integrity. Sci Rep 2023; 13:12899. [PMID: 37558693 PMCID: PMC10412641 DOI: 10.1038/s41598-023-39979-6] [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: 12/06/2022] [Accepted: 08/02/2023] [Indexed: 08/11/2023] Open
Abstract
Enhancers function with a basal promoter to control the transcription of target genes. Enhancer regulatory activity is often studied using reporter-based transgene assays. However, unmatched results have been reported when selected enhancers are silenced in situ. In this study, using genomic deletion analysis in mice, we investigated the roles of two previously identified enhancers and the promoter of the Rho gene that codes for the visual pigment rhodopsin. The Rho gene is robustly expressed by rod photoreceptors of the retina, and essential for the subcellular structure and visual function of rod photoreceptors. Mutations in RHO cause severe vision loss in humans. We found that each Rho regulatory region can independently mediate local epigenomic changes, but only the promoter is absolutely required for establishing active Rho chromatin configuration and transcription and maintaining the cell integrity and function of rod photoreceptors. To our surprise, two Rho enhancers that enable strong promoter activation in reporter assays are largely dispensable for Rho expression in vivo. Only small and age-dependent impact is detectable when both enhancers are deleted. Our results demonstrate context-dependent roles of enhancers and highlight the importance of studying functions of cis-regulatory regions in the native genomic context.
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Affiliation(s)
- Chi Sun
- Department of Ophthalmology and Visual Sciences, Washington University, Saint Louis, MO, USA
| | - Philip A Ruzycki
- Department of Ophthalmology and Visual Sciences, Washington University, Saint Louis, MO, USA.
- Department of Genetics, Washington University, 660 South Euclid Avenue, MSC 8096-0006-11, Saint Louis, MO, 63110, USA.
| | - Shiming Chen
- Department of Ophthalmology and Visual Sciences, Washington University, Saint Louis, MO, USA.
- Department of Developmental Biology, Washington University, 660 South Euclid Avenue, MSC 8096-0006-06, Saint Louis, MO, 63110, USA.
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9
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Skiba NP, Lewis TR, Spencer WJ, Castillo CM, Shevchenko A, Arshavsky VY. Absolute Quantification of Photoreceptor Outer Segment Proteins. J Proteome Res 2023; 22:2703-2713. [PMID: 37493966 PMCID: PMC10513726 DOI: 10.1021/acs.jproteome.3c00267] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Photoreceptor cells generate neuronal signals in response to capturing light. This process, called phototransduction, takes place in a highly specialized outer segment organelle. There are significant discrepancies in the reported amounts of many proteins supporting this process, particularly those of low abundance, which limits our understanding of their molecular organization and function. In this study, we used quantitative mass spectrometry to simultaneously determine the abundances of 20 key structural and functional proteins residing in mouse rod outer segments. We computed the absolute number of molecules of each protein residing within an individual outer segment and the molar ratio among all 20 proteins. The molar ratios of proteins comprising three well-characterized constitutive complexes in outer segments differed from the established subunit stoichiometries of these complexes by less than 7%, highlighting the exceptional precision of our quantification. Overall, this study resolves multiple existing discrepancies regarding the outer segment abundances of these proteins, thereby advancing our understanding of how the phototransduction pathway functions as a single, well-coordinated molecular ensemble.
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Affiliation(s)
- Nikolai P. Skiba
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Tylor R. Lewis
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - William J. Spencer
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Carson M. Castillo
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany 01307
| | - Vadim Y. Arshavsky
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
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10
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Lewis TR, Phan S, Castillo CM, Kim KY, Coppenrath K, Thomas W, Hao Y, Skiba NP, Horb ME, Ellisman MH, Arshavsky VY. Photoreceptor disc incisures form as an adaptive mechanism ensuring the completion of disc enclosure. eLife 2023; 12:e89160. [PMID: 37449984 PMCID: PMC10361718 DOI: 10.7554/elife.89160] [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: 05/05/2023] [Accepted: 07/13/2023] [Indexed: 07/18/2023] Open
Abstract
The first steps of vision take place within a stack of tightly packed disc-shaped membranes, or 'discs', located in the outer segment compartment of photoreceptor cells. In rod photoreceptors, discs are enclosed inside the outer segment and contain deep indentations in their rims called 'incisures'. The presence of incisures has been documented in a variety of species, yet their role remains elusive. In this study, we combined traditional electron microscopy with three-dimensional electron tomography to demonstrate that incisures are formed only after discs become completely enclosed. We also observed that, at the earliest stage of their formation, discs are not round as typically depicted but rather are highly irregular in shape and resemble expanding lamellipodia. Using genetically manipulated mice and frogs and measuring outer segment protein abundances by quantitative mass spectrometry, we further found that incisure size is determined by the molar ratio between peripherin-2, a disc rim protein critical for the process of disc enclosure, and rhodopsin, the major structural component of disc membranes. While a high perpherin-2 to rhodopsin ratio causes an increase in incisure size and structural complexity, a low ratio precludes incisure formation. Based on these data, we propose a model whereby normal rods express a modest excess of peripherin-2 over the amount required for complete disc enclosure in order to ensure that this important step of disc formation is accomplished. Once the disc is enclosed, the excess peripherin-2 incorporates into the rim to form an incisure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Sebastien Phan
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Keun-Young Kim
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Kelsey Coppenrath
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - William Thomas
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Nikolai P Skiba
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Marko E Horb
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
- Department of Pharmacology and Cancer Biology, Duke University Medical CenterDurhamUnited States
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11
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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Mapping rhodopsin trafficking in rod photoreceptors with quantitative super-resolution microscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.20.537413. [PMID: 37131638 PMCID: PMC10153271 DOI: 10.1101/2023.04.20.537413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient long-term phototransduction. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
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12
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Lewis TR, Phan S, Castillo CM, Kim KY, Coppenrath K, Thomas W, Hao Y, Skiba NP, Horb ME, Ellisman MH, Arshavsky VY. Photoreceptor disc incisures form as an adaptive mechanism ensuring the completion of disc enclosure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.06.535932. [PMID: 37066355 PMCID: PMC10104153 DOI: 10.1101/2023.04.06.535932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
The first steps of vision take place within a stack of tightly packed disc-shaped membranes, or "discs", located in the outer segment compartment of photoreceptor cells. In rod photoreceptors, discs are enclosed inside the outer segment and contain deep indentations in their rims called "incisures". The presence of incisures has been documented in a variety of species, yet their role remains elusive. In this study, we combined traditional electron microscopy with three-dimensional electron tomography to demonstrate that incisures are formed only after discs become completely enclosed. We also observed that, at the earliest stage of their formation, discs are not round as typically depicted but rather are highly irregular in shape and resemble expanding lamellipodia. Using genetically manipulated mice and frogs and measuring outer segment protein abundances by quantitative mass spectrometry, we further found that incisure size is determined by the molar ratio between peripherin-2, a disc rim protein critical for the process of disc enclosure, and rhodopsin, the major structural component of disc membranes. While a high perpherin-2 to rhodopsin ratio causes an increase in incisure size and structural complexity, a low ratio precludes incisure formation. Based on these data, we propose a model whereby normal rods express a modest excess of peripherin-2 over the amount required for complete disc enclosure in order to ensure that this important step of disc formation is accomplished. Once the disc is enclosed, the excess peripherin-2 incorporates into the rim to form an incisure.
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13
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Sakai D, Hiraoka M, Matsuzaki M, Yokota S, Hirami Y, Onishi A, Nakamura M, Takahashi M, Kurimoto Y, Maeda A. Genotype and phenotype characteristics of RHO-associated retinitis pigmentosa in the Japanese population. Jpn J Ophthalmol 2023; 67:138-148. [PMID: 36648560 DOI: 10.1007/s10384-023-00975-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 11/19/2022] [Indexed: 01/18/2023]
Abstract
PURPOSE To identify the genotypic and phenotypic characteristics of rhodopsin (RHO)-associated retinitis pigmentosa (RP) in the Japanese population. STUDY DESIGN Cross-sectional, single-center study METHODS: The medical records of 1336 patients with RP who underwent genetic testing at our clinic between November 2008 and September 2021 were reviewed, and patients with RHO variants were included. The patients were divided into class A and class B to assess genotype-phenotype correlations based on previous reports. The clinical findings, including best-corrected visual acuity (BCVA), OCT parameters (ellipsoid zone [EZ] width and central retinal thickness [CRT]), and presence of macular degeneration, of the 2 groups were compared. RESULTS The study included 28 patients diagnosed with RHO-associated RP (class A, 19; class B, 9). The BCVA was significantly worse in class A patients than in class B patients (P = 0.045). Superior EZ width was significantly shorter in class A than in class B patients (P = 0.016). Class A patients tended to have thinner CRT and shorter inferior EZ width than those of class B patients, although this difference was not significant. Macular degeneration was observed in 61.5% of class A and 12.5% of class B patients, demonstrating that macular degeneration can be a common complication in class A variants. CONCLUSION Patients with class A variants presented with a severer form of RP than that of patients with class B variants in the Japanese population. These results suggest that the phenotype of RHO-associated RP is linked to the location of the variants and that such a genotype-phenotype correlation is less affected by ethnicities with different genetic backgrounds.
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Affiliation(s)
- Daiki Sakai
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan. .,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan. .,Department of Surgery, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan.
| | - Masakazu Hiraoka
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kawasaki Medical School, Kurashiki, Okayama, Japan
| | - Mitsuhiro Matsuzaki
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan
| | - Satoshi Yokota
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan
| | - Yasuhiko Hirami
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan
| | - Akishi Onishi
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Vision Care Inc., Kobe, Japan
| | - Makoto Nakamura
- Department of Surgery, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masayo Takahashi
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Vision Care Inc., Kobe, Japan
| | - Yasuo Kurimoto
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan
| | - Akiko Maeda
- Department of Ophthalmology, Kobe City Eye Hospital, 2-1-8 Minatojima Minamimachi, Chuo-ku, Kobe-shi, Hyogo, 650-0047, Japan.,Department of Ophthalmology, Kobe City Medical Center General Hospital, Kobe, Japan
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14
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Gulati S, Palczewski K. Structural view of G protein-coupled receptor signaling in the retinal rod outer segment. Trends Biochem Sci 2023; 48:172-186. [PMID: 36163145 PMCID: PMC9868064 DOI: 10.1016/j.tibs.2022.08.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 01/26/2023]
Abstract
Visual phototransduction is the most extensively studied G protein-coupled receptor (GPCR) signaling pathway because of its quantifiable stimulus, non-redundancy of genes, and immense importance in vision. We summarize recent discoveries that have advanced our understanding of rod outer segment (ROS) morphology and the pathological basis of retinal diseases. We have combined recently published cryo-electron tomography (cryo-ET) data on the ROS with structural knowledge on individual proteins to define the precise spatial limitations under which phototransduction occurs. Although hypothetical, the reconstruction of the rod phototransduction system highlights the potential roles of phosphodiesterase 6 (PDE6) and guanylate cyclases (GCs) in maintaining the spacing between ROS discs, suggesting a plausible mechanism by which intrinsic optical signals are generated in the retina.
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Affiliation(s)
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, Center for Translational Vision Research, Department of Physiology and Biophysics, Department of Chemistry, Molecular Biology, and Biochemistry, University of California Irvine, 850 Health Sciences Road, Irvine, CA 92697-4375, USA.
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15
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Skiba NP, Lewis TR, Spencer WJ, Castillo CM, Shevchenko A, Arshavsky VY. Absolute quantification of photoreceptor outer segment proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.19.524794. [PMID: 36711880 PMCID: PMC9882265 DOI: 10.1101/2023.01.19.524794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Photoreceptor cells generate neuronal signals in response to capturing light. This process, called phototransduction, takes place in a highly specialized outer segment organelle. There are significant discrepancies in the reported amounts of many proteins supporting this process, particularly those of low abundance, which limits our understanding of their molecular organization and function. In this study, we used quantitative mass spectrometry to simultaneously measure the outer segment content of twenty key structural and functional proteins. We determined the molar ratio amongst all twenty proteins as well as the number of molecules of each protein residing within an outer segment. To assess the precision of this quantification, we took advantage of the fact that seven of these proteins exist within three constitutive complexes of well-established subunit stoichiometries. Remarkably, our measurements differed from these stoichiometries by less than 7%, highlighting the exceptional precision of our quantification. This allowed us to resolve the existing discrepancies regarding the outer segment abundances of these proteins, thereby advancing our understanding of how the phototransduction pathway functions as a single, well-coordinated molecular ensemble.
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16
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Hollingsworth TJ, Wang X, Simpson RN, White WA, Williams RW, Jablonski MM. Current Advancements in Mouse Models of Retinal Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:371-376. [PMID: 37440059 DOI: 10.1007/978-3-031-27681-1_54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The field of retinal degenerative (RDs) disease study has been in a state of exponential growth from discovering the underlying genetic components of such diseases as age-related macular degeneration (AMD) and retinitis pigmentosa (RP) to the first gene therapy developed and approved for human Leber congenital amaurosis. However, a source for high-fidelity animal models of these complex, multifactorial, and/or polygenic diseases is a need that has yet to be fulfilled. While models for AMD and RP do exist, they often require aging the animals for a year or more, feeding special diets, or introduction of external modulators such as exposure to cigarette smoke. Currently, work is being done to uncover high-fidelity naturally occurring models of these retinal diseases with the hope and intent of providing the vision community the tools it needs to better understand, treat, and, one day, cure the patients suffering from these devastating afflictions.
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Affiliation(s)
- T J Hollingsworth
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Memphis, TN, USA.
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA.
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA.
| | - Xiangdi Wang
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | - Raven N Simpson
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | - William A White
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | - Robert W Williams
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Genetics, Genomics, and Informatics, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | - Monica M Jablonski
- Department of Ophthalmology, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, TN, USA
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17
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Motipally SI, Kolandaivelu S. Absence of PRCD Leads to Dysregulation in Lipid Homeostasis Resulting in Disorganization of Photoreceptor Outer Segment Structure. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:389-394. [PMID: 37440062 DOI: 10.1007/978-3-031-27681-1_57] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The outer segments of photoreceptors are specialized sensory cilia crucial for light detection. Any disruption that alters outer segment morphology can impair photoreceptor function and therefore vision. Progressive rod-cone degeneration (PRCD) is an integral membrane protein exclusively present in the photoreceptor OS with an unknown function. Multiple mutations in PRCD are linked with retinitis pigmentosa. The most common PRCD mutation observed in both human and multiple dog breeds, PRCD-C2Y, lacks the lipid modification "palmitoylation," which is crucial for protein stability and trafficking to the OS. Previous studies including ours show impaired disc morphogenesis and rhodopsin distributions in the absence of PRCD, but the precise role of PRCD in maintaining OS structure and function remains unclear. In this chapter, we discuss the potential role of PRCD in the maintenance of photoreceptor OS structural and functional integrity.
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Affiliation(s)
- Sree I Motipally
- Departments of Neuroscience and Biochemistry, Robert C. Byrd Health Sciences Centre, WVU Eye Institute, Morgantown, WV, USA
| | - Saravanan Kolandaivelu
- Departments of Ophthalmology, Visual Sciences and Biochemistry, Robert C. Byrd Health Sciences Centre, WVU Eye Institute, Morgantown, WV, USA.
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18
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Vats A, Xi Y, Feng B, Clinger OD, St Leger AJ, Liu X, Ghosh A, Dermond CD, Lathrop KL, Tochtrop GP, Picaud S, Chen Y. Non-retinoid chaperones improve rhodopsin homeostasis in a mouse model of retinitis pigmentosa. JCI Insight 2022; 7:153717. [PMID: 35472194 PMCID: PMC9220944 DOI: 10.1172/jci.insight.153717] [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: 07/29/2021] [Accepted: 04/20/2022] [Indexed: 11/17/2022] Open
Abstract
Rhodopsin-associated (RHO-associated) retinitis pigmentosa (RP) is a progressive retinal disease that currently has no cure. RHO protein misfolding leads to disturbed proteostasis and the death of rod photoreceptors, resulting in decreased vision. We previously identified nonretinoid chaperones of RHO, including YC-001 and F5257-0462, by small-molecule high-throughput screening. Here, we profile the chaperone activities of these molecules toward the cell-surface level of 27 RP-causing human RHO mutants in NIH3T3 cells. Furthermore, using retinal explant culture, we show that YC-001 improves retinal proteostasis by supporting RHO homeostasis in RhoP23H/+ mouse retinae, which results in thicker outer nuclear layers (ONL), indicating delayed photoreceptor degeneration. Interestingly, YC-001 ameliorated retinal immune responses and reduced the number of microglia/macrophages in the RhoP23H/+ retinal explants. Similarly, F5257-0462 also protects photoreceptors in RhoP23H/+ retinal explants. In vivo, intravitreal injection of YC-001 or F5257-0462 microparticles in PBS shows that F5257-0462 has a higher efficacy in preserving photoreceptor function and delaying photoreceptor death in RhoP23H/+ mice. Collectively, we provide proof of principle that nonretinoid chaperones are promising drug candidates in treating RHO-associated RP.
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Affiliation(s)
- Abhishek Vats
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Yibo Xi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Bing Feng
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Owen D Clinger
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Anthony J St Leger
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Xujie Liu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Archisha Ghosh
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Chase D Dermond
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Kira L Lathrop
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
| | - Gregory P Tochtrop
- Department of Chemistry, Case Western Reserve University, Cleveland, United States of America
| | - Serge Picaud
- Institut de la Vision, Sorbonne Université, Paris, France
| | - Yuanyuan Chen
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States of America
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19
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Ortega JT, Parmar T, Carmena-Bargueño M, Pérez-Sánchez H, Jastrzebska B. Flavonoids improve the stability and function of P23H rhodopsin slowing down the progression of retinitis pigmentosa in mice. J Neurosci Res 2022; 100:1063-1083. [PMID: 35165923 PMCID: PMC9615108 DOI: 10.1002/jnr.25021] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/29/2021] [Accepted: 12/29/2021] [Indexed: 12/22/2022]
Abstract
The balanced homeostasis of the G protein-coupled receptor (GPCR), rhodopsin (Rho), is required for vision. Misfolding mutations in Rho cause photoreceptor death, leading to retinitis pigmentosa (RP) and consequently blindness. With no cure currently available, the development of efficient therapy for RP is an urgent need. Pharmacological supplementation with molecular chaperones, including flavonoids, improves stability, folding, and membrane targeting of the RP Rho mutants in vitro. Thus, we hypothesized that flavonoids by binding to P23H Rho and enhancing its conformational stability could mitigate detrimental effects of this mutation on retinal health. In this work, we evaluated the pharmacological potential of two model flavonoids, quercetin and myricetin, by using in silico, in vitro, and in vivo models of P23H Rho. Our computational analysis showed that quercetin could interact within the orthosteric binding pocket of P23H Rho and shift the conformation of its N-terminal loop toward the wild type (WT)-like state. Quercetin added to the NIH-3T3 cells stably expressing P23H Rho increased the stability of this receptor and improved its function. Systemic administration of quercetin to P23H Rho knock-in mice substantially improved retinal morphology and function, which was associated with an increase in levels of Rho and cone opsins. In addition, treatment with quercetin resulted in downregulation of the UPR signaling and oxidative stress-related markers. This study unravels the pharmacological potential of quercetin to slow down the progression of photoreceptor death in Rho-related RP and highlights its prospective as a lead compound to develop a novel therapeutic remedy to counter RP pathology.
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Affiliation(s)
- Joseph Thomas Ortega
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Tanu Parmar
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Miguel Carmena-Bargueño
- Structural Bioinformatics and High Performance Computing Research Group (BIO-HPC), UCAM Universidad Católica de Murcia, Guadalupe, Spain
| | - Horacio Pérez-Sánchez
- Structural Bioinformatics and High Performance Computing Research Group (BIO-HPC), UCAM Universidad Católica de Murcia, Guadalupe, Spain
| | - Beata Jastrzebska
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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20
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Identification of small molecule allosteric modulators that act as enhancers/disrupters of rhodopsin oligomerization. J Biol Chem 2021; 297:101401. [PMID: 34774799 PMCID: PMC8665362 DOI: 10.1016/j.jbc.2021.101401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/01/2021] [Accepted: 11/04/2021] [Indexed: 11/27/2022] Open
Abstract
The elongated cilia of the outer segment of rod and cone photoreceptor cells can contain concentrations of visual pigments of up to 5 mM. The rod visual pigments, G protein–coupled receptors called rhodopsins, have a propensity to self-aggregate, a property conserved among many G protein–coupled receptors. However, the effect of rhodopsin oligomerization on G protein signaling in native cells is less clear. Here, we address this gap in knowledge by studying rod phototransduction. As the rod outer segment is known to adjust its size proportionally to overexpression or reduction of rhodopsin expression, genetic perturbation of rhodopsin cannot be used to resolve this question. Therefore, we turned to high-throughput screening of a diverse library of 50,000 small molecules and used a novel assay for the detection of rhodopsin dimerization. This screen identified nine small molecules that either disrupted or enhanced rhodopsin dimer contacts in vitro. In a subsequent cell-free binding study, we found that all nine compounds decreased intrinsic fluorescence without affecting the overall UV-visible spectrum of rhodopsin, supporting their actions as allosteric modulators. Furthermore, ex vivo electrophysiological recordings revealed that a disruptive, hit compound #7 significantly slowed down the light response kinetics of intact rods, whereas compound #1, an enhancing hit candidate, did not substantially affect the photoresponse kinetics but did cause a significant reduction in light sensitivity. This study provides a monitoring tool for future investigation of the rhodopsin signaling cascade and reports the discovery of new allosteric modulators of rhodopsin dimerization that can also alter rod photoreceptor physiology.
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21
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Gulati S, Palczewski K. New focus on regulation of the rod photoreceptor phosphodiesterase. Curr Opin Struct Biol 2021; 69:99-107. [PMID: 33945959 DOI: 10.1016/j.sbi.2021.03.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 02/18/2021] [Accepted: 03/25/2021] [Indexed: 02/03/2023]
Abstract
Rod photoreceptor phosphodiesterase (PDE6) is the key catalytic enzyme of visual phototransduction. PDE6 is the only member of the phosphodiesterase family that consists of a heterodimeric catalytic core composed of PDE6α and PDE6β subunits and two inhibitory PDE6γ subunits. Both PDE6α and PDE6β contain two regulatory GAF domains and one catalytic domain. GAF domains and the tightly bound PDE6γ subunits allosterically regulate the activity of the catalytic domain in association with the GTP-bound transducin alpha subunit (Gtα-GTP). Recent cryo-electron microscopy structures of the PDE6αγβγ and PDE6αγβγ-(Gtα-GTP)2 complexes have provided valuable knowledge shedding additional light on the allosteric activation of PDE6 by Gtα-GTP. Here we discuss recent developments in our understanding of the mechanism of PDE6 activation.
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Affiliation(s)
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, Center for Translational Vision Research, University of California, 829 Health Sciences Road, Irvine, CA 92617, USA; The Department of Physiology & Biophysics, University of California, Irvine, CA 92697, USA; The Department of Chemistry, University of California, Irvine, CA 92697, USA.
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22
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Temporal Contrast Sensitivity Increases despite Photoreceptor Degeneration in a Mouse Model of Retinitis Pigmentosa. eNeuro 2021; 8:ENEURO.0020-21.2021. [PMID: 33509952 PMCID: PMC8059883 DOI: 10.1523/eneuro.0020-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 01/18/2021] [Indexed: 11/21/2022] Open
Abstract
The detection of temporal variations in amplitude of light intensity, or temporal contrast sensitivity (TCS), depends on the kinetics of rod photoresponse recovery. Uncharacteristically fast rod recovery kinetics are facets of both human patients and transgenic animal models with a P23H rhodopsin mutation, a prevalent cause of retinitis pigmentosa (RP). Here, we show that mice with this mutation (RhoP23H/+) exhibit an age-dependent and illumination-dependent enhancement in TCS compared with controls. At retinal illumination levels producing ≥1000 R*/rod/s or more, postnatal day 30 (P30) RhoP23H/+ mice exhibit a 1.2-fold to 2-fold increase in retinal and optomotor TCS relative to controls in response to flicker frequencies of 3, 6, and 12 Hz despite significant photoreceptor degeneration and loss of flash electroretinogram (ERG) b-wave amplitude. Surprisingly, the TCS of RhoP23H/+ mice further increases as degeneration advances. Enhanced TCS is also observed in a second model (rhodopsin heterozygous mice, Rho+/-) with fast rod recovery kinetics and no apparent retinal degeneration. In both mouse models, enhanced TCS is explained quantitatively by a comprehensive model that includes photoresponse recovery kinetics, density and collecting area of degenerating rods. Measurement of TCS may be a non-invasive early diagnostic tool indicative of rod dysfunction in some forms of retinal degenerative disease.
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23
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Park PSH. Supramolecular organization of rhodopsin in rod photoreceptor cell membranes. Pflugers Arch 2021; 473:1361-1376. [PMID: 33591421 DOI: 10.1007/s00424-021-02522-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/12/2021] [Accepted: 01/18/2021] [Indexed: 11/30/2022]
Abstract
Rhodopsin is the light receptor in rod photoreceptor cells that initiates scotopic vision. Studies on the light receptor span well over a century, yet questions about the organization of rhodopsin within the photoreceptor cell membrane still persist and a consensus view on the topic is still elusive. Rhodopsin has been intensely studied for quite some time, and there is a wealth of information to draw from to formulate an organizational picture of the receptor in native membranes. Early experimental evidence in apparent support for a monomeric arrangement of rhodopsin in rod photoreceptor cell membranes is contrasted and reconciled with more recent visual evidence in support of a supramolecular organization of rhodopsin. What is known so far about the determinants of forming a supramolecular structure and possible functional roles for such an organization are also discussed. Many details are still missing on the structural and functional properties of the supramolecular organization of rhodopsin in rod photoreceptor cell membranes. The emerging picture presented here can serve as a springboard towards a more in-depth understanding of the topic.
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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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24
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Das Y, Swinkels D, Kocherlakota S, Vinckier S, Vaz FM, Wever E, van Kampen AHC, Jun B, Do KV, Moons L, Bazan NG, Van Veldhoven PP, Baes M. Peroxisomal Multifunctional Protein 2 Deficiency Perturbs Lipid Homeostasis in the Retina and Causes Visual Dysfunction in Mice. Front Cell Dev Biol 2021; 9:632930. [PMID: 33604342 PMCID: PMC7884615 DOI: 10.3389/fcell.2021.632930] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/11/2021] [Indexed: 01/09/2023] Open
Abstract
Patients lacking multifunctional protein 2 (MFP2), the central enzyme of the peroxisomal β-oxidation pathway, develop retinopathy. This pathway is involved in the metabolism of very long chain (VLCFAs) and polyunsaturated (PUFAs) fatty acids, which are enriched in the photoreceptor outer segments (POS). The molecular mechanisms underlying the retinopathy remain, however, elusive. Here, we report that mice with MFP2 inactivation display decreased retinal function already at the age of 3 weeks, which is accompanied by a profound shortening of the photoreceptor outer and inner segments, but with preserved photoreceptor ultrastructure. Furthermore, MFP2 deficient retinas exhibit severe changes in gene expression with downregulation of genes involved in the phototransduction pathway and upregulation of inflammation related genes. Lipid profiling of the mutant retinas revealed a profound reduction of DHA-containing phospholipids. This was likely due to a hampered systemic supply and retinal traffic of this PUFA, although we cannot exclude that the local defect of peroxisomal β-oxidation contributes to this DHA decrease. Moreover, very long chain PUFAs were also reduced, with the exception of those containing ≥ 34 carbons that accumulated. The latter suggests that there is an uncontrollable elongation of retinal PUFAs. In conclusion, our data reveal that intact peroxisomal β-oxidation is indispensable for retinal integrity, most likely by maintaining PUFA homeostasis.
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Affiliation(s)
- Yannick Das
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Sai Kocherlakota
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Stefan Vinckier
- Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology, KU Leuven-VIB, Leuven, Belgium
| | - Frédéric M Vaz
- Laboratory of Genetic Metabolic Diseases, Department of Clinical Chemistry and Pediatrics, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Core Facility Metabolomics, Amsterdam University Medical Center (UMC), Amsterdam, Netherlands
| | - Eric Wever
- Laboratory of Genetic Metabolic Diseases, Department of Clinical Chemistry and Pediatrics, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Core Facility Metabolomics, Amsterdam University Medical Center (UMC), Amsterdam, Netherlands.,Bioinformatics Laboratory, Department of Epidemiology and Data Science, Amsterdam Public Health Research Institute, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands
| | - Antoine H C van Kampen
- Bioinformatics Laboratory, Department of Epidemiology and Data Science, Amsterdam Public Health Research Institute, Amsterdam University Medical Center (UMC), University of Amsterdam, Amsterdam, Netherlands.,Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Khanh V Do
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Lieve Moons
- Animal Physiology and Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Paul P Van Veldhoven
- Lipid Biochemistry and Protein Interactions (LIPIT), Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
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25
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Ortega JT, Parmar T, Golczak M, Jastrzebska B. Protective Effects of Flavonoids in Acute Models of Light-Induced Retinal Degeneration. Mol Pharmacol 2020; 99:60-77. [PMID: 33154094 DOI: 10.1124/molpharm.120.000072] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 10/26/2020] [Indexed: 12/17/2022] Open
Abstract
Degeneration of photoreceptors caused by excessive illumination, inherited mutations, or aging is the principal pathology of blinding diseases. Pharmacological compounds that stabilize the visual receptor rhodopsin and modulate the cellular pathways triggering death of photoreceptors could avert this pathology. Interestingly, flavonoids can modulate the cellular processes, such as oxidative stress, inflammatory responses, and apoptosis, that are activated during retinal degeneration. As we found previously, flavonoids also bind directly to unliganded rod opsin, enhancing its folding, stability, and regeneration. In addition, flavonoids stimulate rhodopsin gene expression. Thus, we evaluated the effect of two main dietary flavonoids, quercetin and myricetin, in ATP-binding cassette subfamily A member 4 -/- /retinol dehydrogenase 8 -/- and wild-type BALB/c mice susceptible to light-induced photoreceptor degeneration. Using in vivo imaging, such as optical coherence tomography, scanning laser ophthalmoscopy, and histologic assessment of retinal morphology, we found that treatment with these flavonoids prior to light insult remarkably protected retina from deterioration and preserved its function. Using high-performance liquid chromatography-mass spectrometry analysis, we detected these flavonoids in the eye upon their intraperitoneal administration. The molecular events associated with the protective effect of quercetin and myricetin were related to the elevated expression of photoreceptor-specific proteins, rhodopsin and cone opsins, decreased expression of the specific inflammatory markers, and the shift of the equilibrium between cell death regulators BCL2-associated X protein (BAX) and B-cell lymphoma 2 toward an antiapoptotic profile. These results were confirmed in photoreceptor-derived 661W cells treated with either H2O2 or all-trans-retinal stressors implicated in the mechanism of retinal degeneration. Altogether, flavonoids could have significant prophylactic value for retinal degenerative diseases. SIGNIFICANCE STATEMENT: Flavonoids commonly present in food exhibit advantageous effects in blinding diseases. They bind to and stabilize unliganded rod opsin, which in excess accelerates degenerative processes in the retina. Additionally, flavonoids enhance the expression of the visual receptors, rod and cone opsins; inhibit the inflammatory reactions; and induce the expression of antiapoptotic markers in the retina, preventing the degeneration in vivo. Thus, flavonoids could have a prophylactic value for retinal degenerative diseases.
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Affiliation(s)
- Joseph T Ortega
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Tanu Parmar
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Marcin Golczak
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Beata Jastrzebska
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio
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26
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Sechrest ER, Murphy J, Senapati S, Goldberg AFX, Park PSH, Kolandaivelu S. Loss of PRCD alters number and packaging density of rhodopsin in rod photoreceptor disc membranes. Sci Rep 2020; 10:17885. [PMID: 33087780 PMCID: PMC7577997 DOI: 10.1038/s41598-020-74628-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 09/28/2020] [Indexed: 02/06/2023] Open
Abstract
Progressive rod-cone degeneration (PRCD) is a small protein localized to photoreceptor outer segment (OS) disc membranes. Several mutations in PRCD are linked to retinitis pigmentosa (RP) in canines and humans, and while recent studies have established that PRCD is required for high fidelity disc morphogenesis, its precise role in this process remains a mystery. To better understand the part which PRCD plays in disease progression as well as its contribution to photoreceptor OS disc morphogenesis, we generated a Prcd-KO animal model using CRISPR/Cas9. Loss of PRCD from the retina results in reduced visual function accompanied by slow rod photoreceptor degeneration. We observed a significant decrease in rhodopsin levels in Prcd-KO retina prior to photoreceptor degeneration. Furthermore, ultrastructural analysis demonstrates that rod photoreceptors lacking PRCD display disoriented and dysmorphic OS disc membranes. Strikingly, atomic force microscopy reveals that many disc membranes in Prcd-KO rod photoreceptor neurons are irregular, containing fewer rhodopsin molecules and decreased rhodopsin packing density compared to wild-type discs. This study strongly suggests an important role for PRCD in regulation of rhodopsin incorporation and packaging density into disc membranes, a process which, when dysregulated, likely gives rise to the visual defects observed in patients with PRCD-associated RP.
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Affiliation(s)
- Emily R Sechrest
- Department of Pharmaceutical Sciences, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA.,Department of Ophthalmology and Visual Sciences, Eye Institute, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA
| | - Joseph Murphy
- Department of Ophthalmology and Visual Sciences, Eye Institute, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA.,Department of Biochemistry, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA
| | - Subhadip Senapati
- 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
| | - Saravanan Kolandaivelu
- Department of Ophthalmology and Visual Sciences, Eye Institute, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA. .,Department of Biochemistry, One Medical Center Drive, West Virginia University, Morgantown, WV, 26506-9193, USA.
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27
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Abstract
Numerous rhodopsin mutations have been implicated in night blindness and retinal degeneration, often with unclear etiology. D190N-rhodopsin (D190N-Rho) is a well-known inherited human mutation causing retinitis pigmentosa. Both higher-than-normal spontaneous-isomerization activity and misfolding/mistargeting of the mutant protein have been proposed as causes of the disease, but neither explanation has been thoroughly examined. We replaced wild-type rhodopsin (WT-Rho) in RhoD190N/WT mouse rods with a largely "functionally silenced" rhodopsin mutant to isolate electrical responses triggered by D190N-Rho activity, and found that D190N-Rho at the single-molecule level indeed isomerizes more frequently than WT-Rho by over an order of magnitude. Importantly, however, this higher molecular dark activity does not translate into an overall higher cellular dark noise, owing to diminished D190N-Rho content in the rod outer segment. Separately, we found that much of the degeneration and shortened outer-segment length of RhoD190N/WT mouse rods was not averted by ablating rod transducin in phototransduction-also consistent with D190N-Rho's higher isomerization activity not being the primary cause of disease. Instead, the low pigment content, shortened outer-segment length, and a moderate unfolded protein response implicate protein misfolding as the major pathogenic problem. Finally, D190N-Rho also provided some insight into the mechanism of spontaneous pigment excitation.
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28
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Lewis TR, Shores CR, Cady MA, Hao Y, Arshavsky VY, Burns ME. The F220C and F45L rhodopsin mutations identified in retinitis pigmentosa patients do not cause pathology in mice. Sci Rep 2020; 10:7538. [PMID: 32371886 PMCID: PMC7200662 DOI: 10.1038/s41598-020-64437-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 03/18/2020] [Indexed: 11/12/2022] Open
Abstract
Retinitis pigmentosa is a retinal degenerative disease that leads to blindness through photoreceptor loss. Rhodopsin is the most frequently mutated protein in this disease. While many rhodopsin mutations have well-understood consequences that lead to cell death, the disease association of several rhodopsin mutations identified in retinitis pigmentosa patients, including F220C and F45L, has been disputed. In this study, we generated two knockin mouse lines bearing each of these mutations. We did not observe any photoreceptor degeneration in either heterozygous or homozygous animals of either line. F220C mice exhibited minor disruptions of photoreceptor outer segment dimensions without any mislocalization of outer segment proteins, whereas photoreceptors of F45L mice were normal. Suction electrode recordings from individual photoreceptors of both mutant lines showed normal flash sensitivity and photoresponse kinetics. Taken together, these data suggest that neither the F220C nor F45L mutation has pathological consequences in mice and, therefore, may not be causative of retinitis pigmentosa in humans.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, United States
| | - Camilla R Shores
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA, 95616, United States
| | - Martha A Cady
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, United States
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, United States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, United States.,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, United States
| | - Marie E Burns
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA, 95616, United States. .,Center for Neuroscience and Department of Ophthalmology & Vision Science, University of California, Davis, CA, 95616, United States.
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29
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Talib M, Boon CJF. Retinal Dystrophies and the Road to Treatment: Clinical Requirements and Considerations. Asia Pac J Ophthalmol (Phila) 2020; 9:159-179. [PMID: 32511120 PMCID: PMC7299224 DOI: 10.1097/apo.0000000000000290] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/01/2020] [Indexed: 12/15/2022] Open
Abstract
: Retinal dystrophies (RDs) comprise relatively rare but devastating causes of progressive vision loss. They represent a spectrum of diseases with marked genetic and clinical heterogeneity. Mutations in the same gene may lead to different diagnoses, for example, retinitis pigmentosa or cone dystrophy. Conversely, mutations in different genes may lead to the same phenotype. The age at symptom onset, and the rate and characteristics of peripheral and central vision decline, may vary widely per disease group and even within families. For most RD cases, no effective treatment is currently available. However, preclinical studies and phase I/II/III gene therapy trials are ongoing for several RD subtypes, and recently the first retinal gene therapy has been approved by the US Food and Drug Administration for RPE65-associated RDs: voretigene neparvovec-rzyl (Luxturna). With the rapid advances in gene therapy studies, insight into the phenotypic spectrum and long-term disease course is crucial information for several RD types. The vast clinical heterogeneity presents another important challenge in the evaluation of potential efficacy in future treatment trials, and in establishing treatment candidacy criteria. This perspective describes these challenges, providing detailed clinical descriptions of several forms of RD that are caused by genes of interest for ongoing and future gene or cell-based therapy trials. Several ongoing and future treatment options will be described.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology, Leiden, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden, The Netherlands
- Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, University of Amsterdam. Amsterdam, The Netherlands
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30
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Xiao J, Adil MY, Chang K, Yu Z, Yang L, Utheim TP, Chen DF, Cho KS. Visual Contrast Sensitivity Correlates to the Retinal Degeneration in Rhodopsin Knockout Mice. Invest Ophthalmol Vis Sci 2020; 60:4196-4204. [PMID: 31618423 PMCID: PMC6795341 DOI: 10.1167/iovs.19-26966] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Purpose Clinical manifestations of photoreceptor degeneration include gradual thinning of the outer nuclear layer (ONL) and progressive reduction of electroretinogram (ERG) amplitudes and vision loss. Although preclinical evaluations of treatment strategies greatly depend on rodent models, the courses of these changes in mice remain unclear. We thus sought to investigate the temporal correlations in changes of spatial vision, ERG response, and ONL thickness in mice with progressive photoreceptor degeneration. Methods Adult wild-type (WT) mice and mice carrying rhodopsin deficiency (Rho−/−), a frequently used mouse model of human retinitis pigmentosa, were selected for investigation. Mouse spatial vision, including visual acuity (VA) and contrast sensitivity (CS), was determined using optomotor response (OMR) assays; ONL thickness was quantified by spectral-domain optical coherence tomography (SD-OCT), and ERG was performed to evaluate retinal functions. The mice were killed when they were 14 weeks old, and the cone photoreceptors in retinal sections were counted. Results Spatial vision, ONL thickness, and ERG amplitudes remained stable in WT mice at all examined time points. While 6-week-old Rho−/− mice had VA, CS, as well as ERG responses similar to those of WT mice, progressive reductions in the spatial vision and retinal functions were recorded thereafter. Most tested 12-week-old Rho−/− mice had no visual-evoked OMR and ERG responses. Moreover, CS, but not VA, displayed a linear decline that was closely associated with ONL thinning, reduction of ERG amplitudes, and loss of cones. Conclusions We presented a comprehensive study of the relation between the changes of spatial vision, retinal function, and ONL thickness in postnatal week (PW)6 to PW12 Rho−/− mice. CS is a more sensitive indicator of spatial vision compared to VA, although both are required as separate parameters for monitoring the visual changes in retina undergoing photoreceptor degeneration.
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Affiliation(s)
- Jiaxin Xiao
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.,Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Muhammed Yasin Adil
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.,Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Karen Chang
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.,National Taiwan University, Taiwan
| | - Zicheng Yu
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Lanbo Yang
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Tor P Utheim
- Department of Oral Biology, Faculty of Dentistry, University of Oslo, Norway
| | - Dong Feng Chen
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Kin-Sang Cho
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.,Geriatric Research Education and Clinical Center, Office of Research and Development, Edith Nourse Rogers Memorial Veterans Hospital, Bedford, Massachusetts, United States
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31
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Lamb TD, Kraft TW. A quantitative account of mammalian rod phototransduction with PDE6 dimeric activation: responses to bright flashes. Open Biol 2020; 10:190241. [PMID: 31910741 PMCID: PMC7014685 DOI: 10.1098/rsob.190241] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We develop an improved quantitative model of mammalian rod phototransduction, and we apply it to the prediction of responses to bright flashes of light. We take account of the recently characterized dimeric nature of PDE6 activation, where the configuration of primary importance has two transducin molecules bound. We simulate the stochastic nature of the activation and shut-off reactions to generate the predicted kinetics of the active molecular species on the disc membrane surfaces, and then we integrate the differential equations for the downstream cytoplasmic reactions to obtain the predicted electrical responses. The simulated responses recover the qualitative form of bright-flash response families recorded from mammalian rod photoreceptors. Furthermore, they provide an accurate description of the relationship between the time spent in saturation and flash intensity, predicting the transition between first and second ‘dominant time constants’ to occur at an intensity around 5000 isomerizations per flash, when the rate of transducin activation is taken to be 1250 transducins s−1 per activated rhodopsin. This rate is consistent with estimates from light-scattering experiments, but is around fourfold higher than has typically been assumed in other studies. We conclude that our model and parameters provide a compelling description of rod photoreceptor bright-flash responses.
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Affiliation(s)
- Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2600, Australia
| | - Timothy W Kraft
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, USA
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32
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Yang TC, Chang CY, Yarmishyn AA, Mao YS, Yang YP, Wang ML, Hsu CC, Yang HY, Hwang DK, Chen SJ, Tsai ML, Lai YH, Tzeng Y, Chang CC, Chiou SH. Carboxylated nanodiamond-mediated CRISPR-Cas9 delivery of human retinoschisis mutation into human iPSCs and mouse retina. Acta Biomater 2020; 101:484-494. [PMID: 31672582 DOI: 10.1016/j.actbio.2019.10.037] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/14/2019] [Accepted: 10/24/2019] [Indexed: 01/08/2023]
Abstract
Nanodiamonds (NDs) are considered to be relatively safe carbon nanomaterials used for the transmission of DNA, proteins and drugs. The feasibility of utilizing the NDs to deliver CRISPR-Cas9 system for gene editing has not been clearly studied. Therefore, in this study, we aimed to use NDs as the carriers of CRISPR-Cas9 components designed to introduce the mutation in RS1 gene associated with X-linked retinoschisis (XLRS). ND particles with a diameter of 3 nm were functionalized by carboxylation of the surface and covalently conjugated with fluorescent mCherry protein. Two linear DNA constructs were attached to the conjugated mCherry: one encoded Cas9 endonuclease and GFP reporter, another encoded sgRNA and contained insert of HDR template designed to introduce RS1 c.625C>T mutation. Such nanoparticles were successfully delivered and internalized by human iPSCs and mouse retinas, the efficiency of internalization was significantly improved by mixing with BSA. The delivery of ND particles led to introduction of RS1 c.625C>T mutation in both human iPSCs and mouse retinas. Rs1 gene editing in mouse retinas resulted in several pathological features typical for XLRS, such as aberrant photoreceptor structure. To conclude, our ND-based CRISPR-Cas9 delivery system can be utilized as a tool for creating in vitro and in vivo disease models of XLRS. STATEMENT OF SIGNIFICANCE: X-linked retinoschisis (XLRS) is a prevalent hereditary retinal disease, which is caused by mutations in RS1 gene, whose product is important for structural organization of the retina. The recent development of genome editing techniques such as CRISPR-Cas9 significantly improved the prospects for better understanding the pathology and development of treatment for this disease. Firstly, gene editing can allow development of appropriate in vitro and in vivo disease models; secondly, CRISPR-Cas9 can be applied for gene therapy by removing the disease-causative mutation in vivo. The major prerequisite for these approaches is to develop safe and efficient CRISPR-Cas9 delivery system. In this study, we tested specifically modified nanodiamonds for such a delivery system. We were able to introduce Rs1 mutation into the mouse retina and, importantly, observed several XLRS-specific effects.
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Coussa RG, Basali D, Maeda A, DeBenedictis M, Traboulsi EI. Sector retinitis pigmentosa: Report of ten cases and a review of the literature. Mol Vis 2019; 25:869-889. [PMID: 31908405 PMCID: PMC6937219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 12/28/2019] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To describe the genotypes and phenotypes of ten patients with sector retinitis pigmentosa (RP). We also review previously reported mutations associated with sector RP and provide a discussion of possible underlying pathophysiological mechanisms. METHODS Patients underwent detailed ophthalmologic examinations, fundus photography, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (SD-OCT), as well as visual field and electroretinographic testing. All patients underwent genetic testing to identify the molecular etiology of their disease. RESULTS A total of ten patients were studied. Among these patients, nine had mutations in RHO (c.677T>C; p.Leu226Pro (novel), c.68C>A; p.Pro23His, c.808A>C; p.Ser270Arg, c.44A>G; p.Asn15Ser, and c.325G>A; p.Gly109Arg), and one patient had a mutation in RPGR (c.3092_3093delAG; p.Glu1031Glyfs*47). All patients with missense mutations in RHO had visual acuities (VAs) better than 20/30 and showed a retained foveal ellipsoid zone and overlying retinal structures. The patient with the c.3092_3093delAG deletion in RPGR had VA of 20/60 oculus dexter (OD) and 20/400 oculus sinister (OS), as well as significant foveal thinning and contour atrophy. All patients showed pigmentary changes, or marked atrophy along the inferior arcades, or both. This pattern of degeneration corresponded to hypo- and hyperFAF and superior visual defects. CONCLUSIONS Sector RP is an uncommon form of RP in which only one or two retinal quadrants display clinical pathological signs. The great majority of cases result from mutations in RHO. The present data confirmed previously reported phenotypic manifestations of sector RP. Inferior retinal quadrants are possibly more severely affected due to greater light exposure.
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Affiliation(s)
- Razek Georges Coussa
- Center for Genetic Eye Diseases, Cole Eye Institute, Cleveland Clinic, Cleveland, OH
| | - Diana Basali
- Center for Genetic Eye Diseases, Cole Eye Institute, Cleveland Clinic, Cleveland, OH
| | - Akiko Maeda
- Department of Ophthalmology & Visual Sciences, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Meghan DeBenedictis
- Center for Genetic Eye Diseases, Cole Eye Institute, Cleveland Clinic, Cleveland, OH
| | - Elias I. Traboulsi
- Center for Genetic Eye Diseases, Cole Eye Institute, Cleveland Clinic, Cleveland, OH
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34
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Gene Therapy in Retinal Dystrophies. Int J Mol Sci 2019; 20:ijms20225722. [PMID: 31739639 PMCID: PMC6888000 DOI: 10.3390/ijms20225722] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 11/13/2019] [Accepted: 11/13/2019] [Indexed: 12/12/2022] Open
Abstract
Inherited retinal dystrophies (IRDs) are a group of clinically and genetically heterogeneous degenerative disorders. To date, mutations have been associated with IRDs in over 270 disease genes, but molecular diagnosis still remains elusive in about a third of cases. The methodologic developments in genome sequencing techniques that we have witnessed in this last decade have represented a turning point not only in diagnosis and prognosis but, above all, in the identification of new therapeutic perspectives. The discovery of new disease genes and pathogenetic mechanisms underlying IRDs has laid the groundwork for gene therapy approaches. Several clinical trials are ongoing, and the recent approval of Luxturna, the first gene therapy product for Leber congenital amaurosis, marks the beginning of a new era. Due to its anatomical and functional characteristics, the retina is the organ of choice for gene therapy, although there are quite a few difficulties in the translational approaches from preclinical models to humans. In the first part of this review, an overview of the current knowledge on methodological issues and future perspectives of gene therapy applied to IRDs is discussed; in the second part, the state of the art of clinical trials on the gene therapy approach in IRDs is illustrated.
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35
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Zhao DY, Pöge M, Morizumi T, Gulati S, Van Eps N, Zhang J, Miszta P, Filipek S, Mahamid J, Plitzko JM, Baumeister W, Ernst OP, Palczewski K. Cryo-EM structure of the native rhodopsin dimer in nanodiscs. J Biol Chem 2019; 294:14215-14230. [PMID: 31399513 PMCID: PMC6768649 DOI: 10.1074/jbc.ra119.010089] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 08/02/2019] [Indexed: 02/03/2023] Open
Abstract
Imaging of rod photoreceptor outer-segment disc membranes by atomic force microscopy and cryo-electron tomography has revealed that the visual pigment rhodopsin, a prototypical class A G protein-coupled receptor (GPCR), can organize as rows of dimers. GPCR dimerization and oligomerization offer possibilities for allosteric regulation of GPCR activity, but the detailed structures and mechanism remain elusive. In this investigation, we made use of the high rhodopsin density in the native disc membranes and of a bifunctional cross-linker that preserves the native rhodopsin arrangement by covalently tethering rhodopsins via Lys residue side chains. We purified cross-linked rhodopsin dimers and reconstituted them into nanodiscs for cryo-EM analysis. We present cryo-EM structures of the cross-linked rhodopsin dimer as well as a rhodopsin dimer reconstituted into nanodiscs from purified monomers. We demonstrate the presence of a preferential 2-fold symmetrical dimerization interface mediated by transmembrane helix 1 and the cytoplasmic helix 8 of rhodopsin. We confirmed this dimer interface by double electron-electron resonance measurements of spin-labeled rhodopsin. We propose that this interface and the arrangement of two protomers is a prerequisite for the formation of the observed rows of dimers. We anticipate that the approach outlined here could be extended to other GPCRs or membrane receptors to better understand specific receptor dimerization mechanisms.
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Affiliation(s)
- Dorothy Yanling Zhao
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Matthias Pöge
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Takefumi Morizumi
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Sahil Gulati
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, California 92697
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Ned Van Eps
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jianye Zhang
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, California 92697
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Przemyslaw Miszta
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw 02-093, Poland
| | - Slawomir Filipek
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw 02-093, Poland
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, California 92697
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106
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36
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Getter T, Gulati S, Zimmerman R, Chen Y, Vinberg F, Palczewski K. Stereospecific modulation of dimeric rhodopsin. FASEB J 2019; 33:9526-9539. [PMID: 31121099 PMCID: PMC6662988 DOI: 10.1096/fj.201900443rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 04/23/2019] [Indexed: 11/11/2022]
Abstract
The classic concept that GPCRs function as monomers has been challenged by the emerging evidence of GPCR dimerization and oligomerization. Rhodopsin (Rh) is the only GPCR whose native oligomeric arrangement was revealed by atomic force microscopy demonstrating that Rh exists as a dimer. However, the role of Rh dimerization in retinal physiology is currently unknown. In this study, we identified econazole and sulconazole, two small molecules that disrupt Rh dimer contacts, by implementing a cell-based high-throughput screening assay. Racemic mixtures of identified lead compounds were separated and tested for their stereospecific binding to Rh using UV-visible spectroscopy and intrinsic fluorescence of tryptophan (Trp) 265 after illumination. By following the changes in UV-visible spectra and Trp265 fluorescence in vitro, we found that binding of R-econazole modulates the formation of Meta III and quenches the intrinsic fluorescence of Trp265. In addition, electrophysiological ex vivo recording revealed that R-econazole slows photoresponse kinetics, whereas S-econazole decreased the sensitivity of rods without effecting the kinetics. Thus, this study contributes new methodology to identify compounds that disrupt the dimerization of GPCRs in general and validates the first active compounds that disrupt the Rh dimer specifically.-Getter, T., Gulati, S., Zimmerman, R., Chen, Y., Vinberg, F., Palczewski, K. Stereospecific modulation of dimeric rhodopsin.
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Affiliation(s)
- Tamar Getter
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Sahil Gulati
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Physiology and Biophysics, University of California–Irvine, Irvine, California, USA
| | - Remy Zimmerman
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
| | - Yuanyuan Chen
- Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Frans Vinberg
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Physiology and Biophysics, University of California–Irvine, Irvine, California, USA
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37
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Bocchero U, Tam BM, Chiu CN, Torre V, Moritz OL. Electrophysiological Changes During Early Steps of Retinitis Pigmentosa. Invest Ophthalmol Vis Sci 2019; 60:933-943. [PMID: 30840038 DOI: 10.1167/iovs.18-25347] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The rhodopsin mutation P23H is responsible for a significant portion of autosomal-dominant retinitis pigmentosa, a disorder characterized by rod photoreceptor death. The mechanisms of toxicity remain unclear; previous studies implicate destabilization of P23H rhodopsin during light exposure, causing decreased endoplasmic reticulum (ER) exit and ER stress responses. Here, we probed phototransduction in Xenopus laevis rods expressing bovine P23H rhodopsin, in which retinal degeneration is inducible by light exposure, in order to examine early physiological changes that occur during retinal degeneration. Methods We recorded single-cell and whole-retina responses to light stimuli using electrophysiology. Moreover, we monitored morphologic changes in rods after different periods of light exposure. Results Initially, P23H rods had almost normal photoresponses, but following a brief light exposure varying from 4 to 32 photoisomerizations per disc, photoresponses became irreversibly prolonged. In intact retinas, rods began to shed OS fragments after a rod-saturating exposure of 12 minutes, corresponding to approximately 10 to 100 times more photoisomerizations. Conclusions Our results indicate that in P23H rods light-induced degeneration occurs in at least two stages, the first involving impairment of phototransduction and the second involving initiation of morphologic changes.
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Affiliation(s)
- Ulisse Bocchero
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Beatrice M Tam
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Colette N Chiu
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Vincent Torre
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Orson L Moritz
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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38
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Mallory DP, Gutierrez E, Pinkevitch M, Klinginsmith C, Comar WD, Roushar FJ, Schlebach JP, Smith AW, Jastrzebska B. The Retinitis Pigmentosa-Linked Mutations in Transmembrane Helix 5 of Rhodopsin Disrupt Cellular Trafficking Regardless of Oligomerization State. Biochemistry 2018; 57:5188-5201. [PMID: 30085663 DOI: 10.1021/acs.biochem.8b00403] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
G protein-coupled receptors can exist as dimers and higher-order oligomers in biological membranes. The specific oligomeric assembly of these receptors is believed to play a major role in their function, and the disruption of native oligomers has been implicated in specific human pathologies. Computational predictions and biochemical analyses suggest that two molecules of rhodopsin (Rho) associate through the interactions involving its fifth transmembrane helix (TM5). Interestingly, there are several pathogenic loss-of-function mutations within TM5 that face the lipid bilayer in a manner that could potentially influence the dimerization of Rho. Though several of these mutations are known to induce misfolding, the pathogenic defects associated with V209M and F220C Rho remain unclear. In this work, we utilized a variety of biochemical and biophysical approaches to elucidate the effects of these mutations on the dimerization, folding, trafficking, and function of Rho in relation to other pathogenic TM5 variants. Chemical cross-linking, bioluminescence energy transfer, and pulsed-interleaved excitation fluorescence cross-correlation spectroscopy experiments revealed that each of these mutants exhibits a wild type-like propensity to self-associate within the plasma membrane. However, V209M and F220C each exhibit subtle defects in cellular trafficking. Together, our results suggest that the RP pathology associated with the expression of the V209M and F220C mutants could arise from defects in folding and cellular trafficking rather than the disruption of dimerization, as has been previously proposed.
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Affiliation(s)
- D Paul Mallory
- Department of Chemistry , University of Akron , 190 Buchtel Common , Akron , Ohio 44325 , United States
| | - Elizabeth Gutierrez
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Margaret Pinkevitch
- Department of Chemistry , University of Akron , 190 Buchtel Common , Akron , Ohio 44325 , United States
| | - Christie Klinginsmith
- Department of Chemistry , University of Akron , 190 Buchtel Common , Akron , Ohio 44325 , United States
| | - William D Comar
- Department of Chemistry , University of Akron , 190 Buchtel Common , Akron , Ohio 44325 , United States
| | - Francis J Roushar
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405-7102 , United States
| | - Jonathan P Schlebach
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405-7102 , United States
| | - Adam W Smith
- Department of Chemistry , University of Akron , 190 Buchtel Common , Akron , Ohio 44325 , United States
| | - Beata Jastrzebska
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
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39
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Perche O, Felgerolle C, Ardourel M, Bazinet A, Pâris A, Rossignol R, Meyer-Dilhet G, Mausset-Bonnefont AL, Hébert B, Laurenceau D, Montécot-Dubourg C, Menuet A, Bizot JC, Pichon J, Ranchon-Cole I, Briault S. Early Retinal Defects in Fmr1-/y Mice: Toward a Critical Role of Visual Dys-Sensitivity in the Fragile X Syndrome Phenotype? Front Cell Neurosci 2018; 12:96. [PMID: 29681800 PMCID: PMC5897671 DOI: 10.3389/fncel.2018.00096] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 03/22/2018] [Indexed: 12/29/2022] Open
Abstract
Fragile X Syndrome (FXS) is caused by a deficiency in Fragile X Mental Retardation Protein (FMRP) leading to global sensorial abnormalities, among which visual defects represent a critical part. These visual defects are associated with cerebral neuron immaturity especially in the primary visual cortex. However, we recently demonstrated that retinas of adult Fmr1−/y mice, the FXS murine model, present molecular, cellular and functional alterations. However, no data are currently available on the evolution pattern of such defects. As retinal stimulation through Eye Opening (EO) is a crucial signal for the cerebral visual system maturation, we questioned the precocity of molecular and functional retinal phenotype. To answer this question, we studied the retinal molecular phenotype of Fmr1−/y mice before EO until adult age and the consequences of the retinal loss of Fmrp on retinal function in young and adult mice. We showed that retinal molecular defects are present before EO and remain stable at adult age, leading to electrophysiological impairments without any underlying structural changes. We underlined that loss of Fmrp leads to a wide range of defects in the retina, settled even before EO. Our work demonstrates a critical role of the sensorial dysfunction in the Fmr1−/y mice overall phenotype, and provides evidence that altered peripheral perception is a component of the sensory processing defect in FXS conditions.
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Affiliation(s)
- Olivier Perche
- Genetic Department, Centre Hospitalier Régional d'Orléans, Orléans, France.,UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Chloé Felgerolle
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Maryvonne Ardourel
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Audrey Bazinet
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Arnaud Pâris
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Rafaëlle Rossignol
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Géraldine Meyer-Dilhet
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | | | - Betty Hébert
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - David Laurenceau
- Genetic Department, Centre Hospitalier Régional d'Orléans, Orléans, France
| | - Céline Montécot-Dubourg
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Arnaud Menuet
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | | | - Jacques Pichon
- UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
| | - Isabelle Ranchon-Cole
- Laboratory of Sensorial Biophysical, INSERM UMR1107 Equipe Biophysique Neurosensorielle, University of Clermont 1, Clermont-Ferrand, France
| | - Sylvain Briault
- Genetic Department, Centre Hospitalier Régional d'Orléans, Orléans, France.,UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique, Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France
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Senapati S, Gragg M, Samuels IS, Parmar VM, Maeda A, Park PSH. Effect of dietary docosahexaenoic acid on rhodopsin content and packing in photoreceptor cell membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1403-1413. [PMID: 29626443 DOI: 10.1016/j.bbamem.2018.03.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/13/2018] [Accepted: 03/30/2018] [Indexed: 01/03/2023]
Abstract
Docosahexaenoic acid (DHA) is enriched in photoreceptor cell membranes. DHA deficiency impairs vision due to photoreceptor cell dysfunction, which is caused, at least in part, by reduced activity of rhodopsin, the light receptor that initiates phototransduction. It is unclear how the depletion of membrane DHA impacts the structural properties of rhodopsin and, in turn, its activity. Atomic force microscopy (AFM) was used to assess the impact of DHA deficiency on membrane structure and rhodopsin organization. AFM revealed that signaling impairment in photoreceptor cells is independent of the oligomeric status of rhodopsin and causes adaptations in photoreceptor cells where the content and density of rhodopsin in the membrane is increased. Functional and structural changes caused by DHA deficiency were reversible.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Megan Gragg
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ivy S Samuels
- Research Service, Louis Stokes Cleveland Veterans Administration Medical Center, Cleveland, OH 44106, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Vipul M Parmar
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Akiko Maeda
- 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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C8ORF37 Is Required for Photoreceptor Outer Segment Disc Morphogenesis by Maintaining Outer Segment Membrane Protein Homeostasis. J Neurosci 2018; 38:3160-3176. [PMID: 29440555 DOI: 10.1523/jneurosci.2964-17.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 01/30/2018] [Accepted: 02/05/2018] [Indexed: 01/09/2023] Open
Abstract
C8ORF37 is a causative gene for three different clinical forms of incurable retinal degeneration. However, the completely unknown function of C8ORF37 limits our understanding of the pathogenicity of C8ORF37 mutations. Here, we performed a comprehensive phenotypic characterization of a C8orf37 KO mouse line, generated using CRISPR/Cas9 technology. Both C8orf37 KO male and female mice exhibited progressive and simultaneous degeneration of rod and cone photoreceptors but no non-ocular phenotypes. The major ultrastructural feature of C8orf37 KO photoreceptors was massive disorganization of the outer segment (OS) membrane discs starting from the onset of disc morphogenesis during development. At the molecular level, the amounts of multiple OS-specific membrane proteins, including proteins involved in membrane disc organization, were reduced, although these proteins were targeted normally to the OS. Considering the distribution of C8ORF37 throughout the photoreceptor cell body, the normal structure of the KO photoreceptor connecting cilium, and the absence of defects in other ciliary organs of the KO mice, our findings do not support the previous notion that C8ORF37 was a ciliary protein. Because C8ORF37 is absent in the photoreceptor OS, C8ORF37 may participate in the secretory pathway of OS membrane proteins in the photoreceptor cell body and thus maintain the homeostasis of these proteins. This study established a valid animal model for future therapeutic studies of C8ORF37-associated retinal degeneration. This study also shed new light on the role of C8ORF37 in photoreceptors and on the pathogenic mechanism underlying retinal degeneration caused by C8ORF37 mutations.SIGNIFICANCE STATEMENT Inherited retinal degeneration is a group of incurable conditions with poorly understood underlying molecular mechanisms. We investigated C8ORF37, a causative gene for three retinal degenerative conditions: retinitis pigmentosa, cone-rod dystrophy, and Bardet-Biedl syndrome. C8ORF37 encodes a protein with no known functional domains and thus its biological function is unpredictable. We knocked out the C8ORF37 ortholog in mice, which resulted in a retinal phenotype similar to that observed in patients. We further demonstrated that C8ORF37 is required for photoreceptor outer segment disc formation and alignment, a process that is critical for photoreceptor function and survival. This study advances our understanding of the pathogenesis of retinal degeneration and establishes a valuable mouse model for future therapeutic development.
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Chakraborty D, Conley SM, Pittler SJ, Naash MI. Role of RDS and Rhodopsin in Cngb1-Related Retinal Degeneration. Invest Ophthalmol Vis Sci 2016; 57:787-97. [PMID: 26934134 PMCID: PMC4777275 DOI: 10.1167/iovs.15-18516] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Rod photoreceptor outer segment (OS) morphogenesis, structural integrity, and proper signal transduction rely on critical proteins found in the different OS membrane domains (e.g., plasma, disc, and disc rim membrane). Among these key elements are retinal degeneration slow (RDS, also known as peripherin-2), rhodopsin, and the beta subunit of the cyclic nucleotide gated channel (CNGB1a), which have been found to interact in a complex. The purpose of this study was to evaluate the potential interplay between these three proteins by examining retinal disease phenotypes in animal models expressing varying amounts of CNGB1a, rhodopsin, and RDS. Methods Outer segment trafficking, retinal function, and photoreceptor structure were evaluated using knockout mouse lines. Results Eliminating Cngb1 and reducing RDS leads to additive defects in RDS expression levels and rod electroretinogram (ERG) function, (e.g., Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−) but not to additive defects in rod ultrastructure. These additive effects also manifested in cone function: Photopic ERG responses were significantly lower in the Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−, suggesting that eliminating Cngb1 can accelerate the cone degeneration that usually presents later in the rds+/−. This was not the case with rhodopsin; reducing rhodopsin levels in concert with eliminating CNGB1a did not lead to phenotypes more severe than those observed in the Cngb1 knockout alone. Conclusions These data support a role for RDS as the core component of a multiprotein plasma membrane-rim-disc complex that has both a structural role in photoreceptor OS formation and maintenance and a functional role in orienting proteins for optimal signal transduction.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Steven J Pittler
- Department of Vision Sciences, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
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43
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Goldberg AFX, Moritz OL, Williams DS. Molecular basis for photoreceptor outer segment architecture. Prog Retin Eye Res 2016; 55:52-81. [PMID: 27260426 DOI: 10.1016/j.preteyeres.2016.05.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/27/2016] [Accepted: 05/29/2016] [Indexed: 01/11/2023]
Abstract
To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ∼10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained.
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Affiliation(s)
- Andrew F X Goldberg
- Eye Research Institute, Oakland University, 417 Dodge Hall, Rochester, MI, 48309, USA.
| | - Orson L Moritz
- Department of Ophthalmology & Visual Sciences, University of British Columbia, Vancouver, BC, Canada
| | - David S Williams
- Department of Ophthalmology and Jules Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, USA
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44
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Wong BH, Chan JP, Cazenave-Gassiot A, Poh RW, Foo JC, Galam DLA, Ghosh S, Nguyen LN, Barathi VA, Yeo SW, Luu CD, Wenk MR, Silver DL. Mfsd2a Is a Transporter for the Essential ω-3 Fatty Acid Docosahexaenoic Acid (DHA) in Eye and Is Important for Photoreceptor Cell Development. J Biol Chem 2016; 291:10501-14. [PMID: 27008858 DOI: 10.1074/jbc.m116.721340] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Indexed: 12/22/2022] Open
Abstract
Eye photoreceptor membrane discs in outer rod segments are highly enriched in the visual pigment rhodopsin and the ω-3 fatty acid docosahexaenoic acid (DHA). The eye acquires DHA from blood, but transporters for DHA uptake across the blood-retinal barrier or retinal pigment epithelium have not been identified. Mfsd2a is a newly described sodium-dependent lysophosphatidylcholine (LPC) symporter expressed at the blood-brain barrier that transports LPCs containing DHA and other long-chain fatty acids. LPC transport via Mfsd2a has been shown to be necessary for human brain growth. Here we demonstrate that Mfsd2a is highly expressed in retinal pigment epithelium in embryonic eye, before the development of photoreceptors, and is the primary site of Mfsd2a expression in the eye. Eyes from whole body Mfsd2a-deficient (KO) mice, but not endothelium-specific Mfsd2a-deficient mice, were DHA-deficient and had significantly reduced LPC/DHA transport in vivo Fluorescein angiography indicated normal blood-retinal barrier function. Histological and electron microscopic analysis indicated that Mfsd2a KO mice exhibited a specific reduction in outer rod segment length, disorganized outer rod segment discs, and mislocalization of and reduction in rhodopsin early in postnatal development without loss of photoreceptors. Minor photoreceptor cell loss occurred in adult Mfsd2a KO mice, but electroretinography indicated visual function was normal. The developing eyes of Mfsd2a KO mice had activated microglia and up-regulation of lipogenic and cholesterogenic genes, likely adaptations to loss of LPC transport. These findings identify LPC transport via Mfsd2a as an important pathway for DHA uptake in eye and for development of photoreceptor membrane discs.
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Affiliation(s)
- Bernice H Wong
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Jia Pei Chan
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Amaury Cazenave-Gassiot
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Rebecca W Poh
- the Carl Zeiss Pte. Ltd., Microscopy Business Group, Singapore, 50 Kaki Bukit Place, 05-01, Singapore 415926, Singapore
| | - Juat Chin Foo
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Dwight L A Galam
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Sujoy Ghosh
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Centre for Computational Biology, and
| | - Long N Nguyen
- the Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Building MD4, Level 1-03A, Singapore 117545, Singapore
| | - Veluchamy A Barathi
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Rd 119228, NUHS Tower Block, Level 11, Singapore 117597, Singapore, and ACP Ophthalmology, Duke-National University of Singapore Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Sia W Yeo
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore
| | - Chi D Luu
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Centre for Eye Research Australia, Level 1, 32 Gisborne St., East Melbourne, Victoria 3002, Australia
| | - Markus R Wenk
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - David L Silver
- From the Signature Research Program in Cardiovascular and Metabolic Disorders,
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McKeown AS, Pitale PM, Kraft TW. Signalling beyond photon absorption: extracellular retinoids and growth factors modulate rod photoreceptor sensitivity. J Physiol 2016; 594:1841-54. [PMID: 26691896 DOI: 10.1113/jp271650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 12/18/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We propose that the end product of chromophore bleaching in rod photoreceptors, all-trans retinol, is part of a feedback loop that increases the sensitivity of the phototransduction cascade in rods. A previously described light-induced hypersensitivity in rods, termed adaptive potentiation, is reduced by exogenously applied all-trans retinol but not all-trans retinal. This potentiation is produced by insulin-like growth factor-1, whose binding proteins are located in the extracellular matrix, even in our isolated retina preparation after removal of the retinal pigmented epithelium. Simple modelling suggests that the light stimuli used in the present study will produce sufficient all-trans retinol within the interphotoreceptor matrix to explain the potentiation effect. ABSTRACT Photoreceptors translate the absorption of photons into electrical signals for propagation through the visual system. Mammalian photoreceptor signalling has largely been studied in isolated cells, and such studies have necessarily avoided the complex environment of supportive proteins that surround the photoreceptors. The interphotoreceptor matrix (IPM) contains an array of proteins that aid in both structural maintenance and cellular homeostasis, including chromophore turnover. In signalling photon absorption, the chromophore 11-cis retinal is first isomerized to all-trans retinal, followed by conversion to all-trans retinol (ROL) for removal from the photoreceptor. Interphotoreceptor retinoid-binding protein (IRBP) is the most abundant protein in the IPM, and it promotes the removal of bleached chromophores and recycling in the nearby retinal pigment epithelium. By studying the light responses of isolated mouse retinas, we demonstrate that ROL can act as a feedback signal onto photoreceptors that influences the sensitivity of phototransduction. In addition to IRBP, the IPM also contains insulin-like growth factor-1 (IGF-1) and its associated binding proteins, although their functions have not yet been described. We demonstrate that extracellular application of physiological concentrations of IGF-1 can increase rod photoreceptor sensitivity in mammalian retinas. We also determine that chromophores and growth factors can limit the range of a newly described form of photoreceptor light adaptation. Finally, fluorescent antibodies demonstrate the presence of IRBP and IGFBP-3 in isolated retinas. A simple model of the formation and release of ROL into the extracellular space quantitatively describes this novel feedback loop.
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Affiliation(s)
| | | | - Timothy W Kraft
- Department of Vision Sciences.,Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
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Pearring JN, Spencer WJ, Lieu EC, Arshavsky VY. Guanylate cyclase 1 relies on rhodopsin for intracellular stability and ciliary trafficking. eLife 2015; 4:e12058. [PMID: 26590321 PMCID: PMC4709261 DOI: 10.7554/elife.12058] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Accepted: 11/20/2015] [Indexed: 01/21/2023] Open
Abstract
Sensory cilia are populated by a select group of signaling proteins that detect environmental stimuli. How these molecules are delivered to the sensory cilium and whether they rely on one another for specific transport remains poorly understood. Here, we investigated whether the visual pigment, rhodopsin, is critical for delivering other signaling proteins to the sensory cilium of photoreceptor cells, the outer segment. Rhodopsin is the most abundant outer segment protein and its proper transport is essential for formation of this organelle, suggesting that such a dependency might exist. Indeed, we demonstrated that guanylate cyclase-1, producing the cGMP second messenger in photoreceptors, requires rhodopsin for intracellular stability and outer segment delivery. We elucidated this dependency by showing that guanylate cyclase-1 is a novel rhodopsin-binding protein. These findings expand rhodopsin's role in vision from being a visual pigment and major outer segment building block to directing trafficking of another key signaling protein.
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Affiliation(s)
- Jillian N Pearring
- Department of Ophthalmology, Duke University Medical Center, Durham, United States
| | - William J Spencer
- Department of Ophthalmology, Duke University Medical Center, Durham, United States
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Eric C Lieu
- Department of Ophthalmology, Duke University Medical Center, Durham, United States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, United States
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
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47
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Rhodopsin Forms Nanodomains in Rod Outer Segment Disc Membranes of the Cold-Blooded Xenopus laevis. PLoS One 2015; 10:e0141114. [PMID: 26492040 PMCID: PMC4619631 DOI: 10.1371/journal.pone.0141114] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 10/04/2015] [Indexed: 11/19/2022] Open
Abstract
Rhodopsin forms nanoscale domains (i.e., nanodomains) in rod outer segment disc membranes from mammalian species. It is unclear whether rhodopsin arranges in a similar manner in amphibian species, which are often used as a model system to investigate the function of rhodopsin and the structure of photoreceptor cells. Moreover, since samples are routinely prepared at low temperatures, it is unclear whether lipid phase separation effects in the membrane promote the observed nanodomain organization of rhodopsin from mammalian species. Rod outer segment disc membranes prepared from the cold-blooded frog Xenopus laevis were investigated by atomic force microscopy to visualize the organization of rhodopsin in the absence of lipid phase separation effects. Atomic force microscopy revealed that rhodopsin nanodomains form similarly as that observed previously in mammalian membranes. Formation of nanodomains in ROS disc membranes is independent of lipid phase separation and conserved among vertebrates.
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48
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Chen Y, Tang H, Seibel W, Papoian R, Li X, Lambert NA, Palczewski K. A High-Throughput Drug Screening Strategy for Detecting Rhodopsin P23H Mutant Rescue and Degradation. Invest Ophthalmol Vis Sci 2015; 56:2553-67. [PMID: 25783607 DOI: 10.1167/iovs.14-16298] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Inherent instability of the P23H mutant opsin accounts for approximately 10% of autosomal dominant retinitis pigmentosa cases. Our purpose was to develop an overall set of reliable screening strategies to assess if either stabilization or enhanced degradation of mutant rhodopsin could rescue rod photoreceptors expressing this mutant protein. These strategies promise to reveal active compounds and clarify molecular mechanisms of biologically important processes, such as inhibition of target degradation or enhanced target folding. METHODS Cell-based bioluminescence reporter assays were developed and validated for high-throughput screening (HTS) of compounds that promote either stabilization or degradation of P23H mutant opsin. Such assays were further complemented by immunoblotting and image-based analyses. RESULTS Two stabilization assays of P23H mutant opsin were developed and validated, one based on β-galactosidase complementarity and a second assay involving bioluminescence resonance energy transfer (BRET) technology. Moreover, two additional assays evaluating mutant protein degradation also were employed, one based on the disappearance of luminescence and another employing the ALPHA immunoassay. Imaging of cells revealed the cellular localization of mutant rhodopsin, whereas immunoblots identified changes in the aggregation and glycosylation of P23H mutant opsin. CONCLUSIONS Our findings indicate that these initial HTS and following assays can identify active therapeutic compounds, even for difficult targets such as mutant rhodopsin. The assays are readily scalable and their function has been proven with model compounds. High-throughput screening, supported by automated imaging and classic immunoassays, can further characterize multiple steps and pathways in the biosynthesis and degradation of this essential visual system protein.
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Affiliation(s)
- Yuanyuan Chen
- Department of Pharmacology Case Western Reserve University, Cleveland, Ohio, United States
| | - Hong Tang
- Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio, United States
| | - William Seibel
- Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio, United States
| | - Ruben Papoian
- Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio, United States
| | - Xiaoyu Li
- Department of Pharmacology Case Western Reserve University, Cleveland, Ohio, United States
| | - Nevin A Lambert
- Department of Pharmacology and Toxicology, Georgia Regents University, Augusta, Georgia, United States
| | - Krzysztof Palczewski
- Department of Pharmacology Case Western Reserve University, Cleveland, Ohio, United States
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49
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Zernii EY, Nazipova AA, Gancharova OS, Kazakov AS, Serebryakova MV, Zinchenko DV, Tikhomirova NK, Senin II, Philippov PP, Permyakov EA, Permyakov SE. Light-induced disulfide dimerization of recoverin under ex vivo and in vivo conditions. Free Radic Biol Med 2015; 83:283-95. [PMID: 25772009 DOI: 10.1016/j.freeradbiomed.2015.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 01/10/2015] [Accepted: 03/02/2015] [Indexed: 12/13/2022]
Abstract
Despite vast knowledge of the molecular mechanisms underlying photochemical damage of photoreceptors, linked to progression of age-related macular degeneration, information on specific protein targets of the light-induced oxidative stress is scarce. Here, we demonstrate that prolonged intense illumination (halogen bulb, 1500 lx, 1-5 h) of mammalian eyes under ex vivo (cow) or in vivo (rabbit) conditions induces disulfide dimerization of recoverin, a Ca(2+)-dependent inhibitor of rhodopsin kinase. Western blotting and mass spectrometry analysis of retinal extracts reveals illumination time-dependent accumulation of disulfide homodimers of recoverin and its higher order disulfide cross-linked species, including a minor fraction of mixed disulfides with intracellular proteins (tubulins, etc.). Meanwhile, monomeric bovine recoverin remains mostly reduced. These effects are accompanied by accumulation of disulfide homodimers of visual arrestin. Histological studies demonstrate that the light-induced oxidation of recoverin and arrestin occurs in intact retina (illumination for 2 h), while illumination for 5 h is associated with damage of the photoreceptor layer. A comparison of ex vivo levels of disulfide homodimers of bovine recoverin with redox dependence of its in vitro thiol-disulfide equilibrium (glutathione redox pair) gives the lowest estimate of redox potential in rod outer segments under illumination from -160 to -155 mV. Chemical crosslinking and dynamic light scattering data demonstrate an increased propensity of disulfide dimer of bovine recoverin to multimerization/aggregation. Overall, the oxidative stress caused by the prolonged intense illumination of retina might affect rhodopsin desensitization via concerted disulfide dimerization of recoverin and arrestin. The developed herein models of eye illumination are useful for studies of the light-induced thiol oxidation of visual proteins.
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Affiliation(s)
- Evgeni Yu Zernii
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia.
| | - Aliya A Nazipova
- Protein Research Group, Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia
| | - Olga S Gancharova
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia
| | - Alexey S Kazakov
- Protein Research Group, Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia
| | - Marina V Serebryakova
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia
| | - Dmitry V Zinchenko
- Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia
| | - Natalya K Tikhomirova
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia
| | - Ivan I Senin
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia
| | - Pavel P Philippov
- Department of Cell Signaling, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992 Russia
| | - Eugene A Permyakov
- Protein Research Group, Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia; Department of Biomedical Engineering, Pushchino State Institute of Natural Sciences, Pushchino, Moscow region, 142290 Russia
| | - Sergei E Permyakov
- Protein Research Group, Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia; Department of Biomedical Engineering, Pushchino State Institute of Natural Sciences, Pushchino, Moscow region, 142290 Russia
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50
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Rakshit T, Park PSH. Impact of reduced rhodopsin expression on the structure of rod outer segment disc membranes. Biochemistry 2015; 54:2885-94. [PMID: 25881629 DOI: 10.1021/acs.biochem.5b00003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rhodopsin is the light receptor embedded in rod outer segment (ROS) disc membranes of photoreceptor cells that initiates vision via phototransduction. The relationship between rhodopsin expression and the formation of membrane structures in the ROS is unclear but important to better understand both normal function and pathological conditions. To determine the impact of reduced rhodopsin expression on the structure of ROS discs and the supramolecular organization of rhodopsin, ROS disc membrane samples from heterozygous rhodopsin knockout mice were examined by atomic force microscopy. Similar to rhodopsin in wild-type mice, rhodopsin formed nanodomains in ROS disc membranes of heterozygous knockout mice. The reduced rhodopsin expression in heterozygous knockout mice resulted in ROS disc membranes that were smaller compared to those in wild-type mice at all ages tested. Changes in ROS disc membrane properties were observed between 4 and 6 weeks of age in heterozygous knockout mice that were not present in age-matched wild-type mice. In 4 week old mice, the number and density of rhodopsin in ROS disc membranes was lower than that in age-matched wild-type mice. In contrast, 6 and 8 week old mice had more rhodopsin molecules present in disc membranes compared to 4 week old mice, which resulted in rhodopsin densities similar to those found in age-matched wild-type mice. Thus, mechanisms appear to be present that maintain a constant density of rhodopsin within ROS disc membranes even when reducing the expression of the light receptor by about half. These adaptive mechanisms, however, only occur after 4 weeks of age.
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Affiliation(s)
- Tatini Rakshit
- 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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