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Radhakrishnan R, Leung M, Lor A, More S, Lobo GP. Loss of the systemic vitamin A transporter RBPR2 affects the quantitative balance between chromophore and opsins in visual pigment synthesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.08.602543. [PMID: 39026765 PMCID: PMC11257425 DOI: 10.1101/2024.07.08.602543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
The distribution of dietary vitamin A/all-trans retinol (ROL) throughout the body is critical for maintaining retinoid function in peripheral tissues and for generating visual pigments for photoreceptor cell function. ROL circulates in the blood bound to the retinol binding protein 4 (RBP4) as RBP4-ROL. Two membrane receptors, RBPR2 in the liver and STRA6 in the eye are proposed to bind circulatory RBP4 and this mechanism is critical for internalizing ROL into cells. Here, we present a longitudinal investigation towards the importance of RBPR2 and influence of the diet on systemic retinoid homeostasis for visual function. Age matched Rbpr2-KO (Rbpr2 -/- ) and wild-type (WT) mice were fed either a vitamin A sufficient (VAS) or a vitamin A deficient (VAD) diet. At 3- and 6-months, we performed retinoid quantification of ocular and non-ocular tissues using HPLC analysis and complemented the data with visual physiology, rhodopsin quantification by spectrophotometry, and biochemical analysis. At 3-months and compared to WT mice, Rbpr2 -/- mice fed either vitamin A diets displayed lower scotopic and photopic electroretinogram (ERG) responses, which correlated with HPLC analysis that revealed Rbpr2 -/- mice had significantly lower hepatic and ocular retinoid content. Interestingly, with the exception of the liver, long-term feeding of Rbpr2 -/- mice with a VAS diet promoted all-trans retinol accumulation in most peripheral tissues. However, even under VAS dietary conditions significant amounts of unliganded opsins in rods, together with decreased visual responses were evident in aged mice lacking RBPR2, when compared to WT mice. Together, our analyses characterize the molecular events underlying nutritional blindness in a novel mouse model and indicate that loss of the liver specific RBP4-ROL receptor, RBPR2, influences systemic retinoid homeostasis and rhodopsin synthesis, which causes profound visual function defects under severe vitamin A deficiency conditions.
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Affiliation(s)
- Rakesh Radhakrishnan
- Department of Ophthalmology, University of Minnesota, Lions Research Building, 2001 6 Street SE, Minneapolis, MN 55455, USA
| | - Matthias Leung
- Department of Ophthalmology, University of Minnesota, Lions Research Building, 2001 6 Street SE, Minneapolis, MN 55455, USA
| | - Anjelynt Lor
- Department of Ophthalmology, University of Minnesota, Lions Research Building, 2001 6 Street SE, Minneapolis, MN 55455, USA
| | - Swati More
- Center for Drug Design, College of Pharmacy, University of Minnesota, MN 55455, USA
| | - Glenn P. Lobo
- Department of Ophthalmology, University of Minnesota, Lions Research Building, 2001 6 Street SE, Minneapolis, MN 55455, USA
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2
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Bassetto M, Kolesnikov AV, Lewandowski D, Kiser JZ, Halabi M, Einstein DE, Choi EH, Palczewski K, Kefalov VJ, Kiser PD. Dominant role for pigment epithelial CRALBP in supplying visual chromophore to photoreceptors. Cell Rep 2024; 43:114143. [PMID: 38676924 PMCID: PMC11211020 DOI: 10.1016/j.celrep.2024.114143] [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: 02/28/2024] [Revised: 03/22/2024] [Accepted: 04/09/2024] [Indexed: 04/29/2024] Open
Abstract
Cellular retinaldehyde-binding protein (CRALBP) supports production of 11-cis-retinaldehyde and its delivery to photoreceptors. It is found in the retinal pigment epithelium (RPE) and Müller glia (MG), but the relative functional importance of these two cellular pools is debated. Here, we report RPE- and MG-specific CRALBP knockout (KO) mice and examine their photoreceptor and visual cycle function. Bulk visual chromophore regeneration in RPE-KO mice is 15-fold slower than in controls, accounting for their delayed rod dark adaptation and protection against retinal phototoxicity, whereas MG-KO mice have normal bulk visual chromophore regeneration and retinal light damage susceptibility. Cone pigment regeneration is significantly impaired in RPE-KO mice but mildly affected in MG-KO mice, disclosing an unexpectedly strong reliance of cone photoreceptors on the RPE-based visual cycle. These data reveal a dominant role for RPE-CRALBP in supporting rod and cone function and highlight the importance of RPE cell targeting for CRALBP gene therapies.
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Affiliation(s)
- Marco Bassetto
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Research Service, Tibor Rubin VA Long Beach Medical Center, Long Beach, CA 90822, USA; Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Alexander V Kolesnikov
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Dominik Lewandowski
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Jianying Z Kiser
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Maximilian Halabi
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA
| | - David E Einstein
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Research Service, Tibor Rubin VA Long Beach Medical Center, Long Beach, CA 90822, USA
| | - Elliot H Choi
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Krzysztof Palczewski
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA; Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA; Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Vladimir J Kefalov
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
| | - Philip D Kiser
- Department of Physiology & Biophysics, University of California Irvine, Irvine, CA 92697, USA; Research Service, Tibor Rubin VA Long Beach Medical Center, Long Beach, CA 90822, USA; Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA; Department of Clinical Pharmacy Practice, University of California Irvine, Irvine, CA 92697, USA.
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3
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Andreazzoli M, Longoni B, Angeloni D, Demontis GC. Retinoid Synthesis Regulation by Retinal Cells in Health and Disease. Cells 2024; 13:871. [PMID: 38786093 PMCID: PMC11120330 DOI: 10.3390/cells13100871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 05/13/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024] Open
Abstract
Vision starts in retinal photoreceptors when specialized proteins (opsins) sense photons via their covalently bonded vitamin A derivative 11cis retinaldehyde (11cis-RAL). The reaction of non-enzymatic aldehydes with amino groups lacks specificity, and the reaction products may trigger cell damage. However, the reduced synthesis of 11cis-RAL results in photoreceptor demise and suggests the need for careful control over 11cis-RAL handling by retinal cells. This perspective focuses on retinoid(s) synthesis, their control in the adult retina, and their role during retina development. It also explores the potential importance of 9cis vitamin A derivatives in regulating retinoid synthesis and their impact on photoreceptor development and survival. Additionally, recent advancements suggesting the pivotal nature of retinoid synthesis regulation for cone cell viability are discussed.
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Affiliation(s)
| | - Biancamaria Longoni
- Department of Translational Medicine and New Technologies in Medicine, University of Pisa, 56126 Pisa, Italy
| | - Debora Angeloni
- The Institute of Biorobotics, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
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4
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Takahashi N. [Prevention and Treatment of Cancer with Vitamin A and Its Derivatives: Cell Differentiation and Proliferation]. YAKUGAKU ZASSHI 2024; 144:203-222. [PMID: 38296498 DOI: 10.1248/yakushi.23-00184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Normal differentiation and proliferation of cells are essential for maintaining homeostasis. Following the successful completion of whole genome sequencing, protein modification has been attracted increasing attention in order to understand the roles of protein diversification in protein function and to elucidate molecular targets in mechanisms of signal transduction. Vitamin A is an essential nutrient for health maintenance. It is present as β-carotene in green and yellow vegetables and retinyl ester in animal products and absorbed into the body from the intestines. After ingestion, it is converted to retinol and oxidized in target cells to retinal, which plays critical roles in vision. It is then further oxidized to retinoic acid (RA), which exhibits a number of effects prior to being metabolized by cytochrome P450 and excreted from the body. Since RA exhibits cell differentiation-inducing actions, it is used as a therapeutic agent for patients with acute promyelocytic leukemia. The current paper describes: (1) HL60 cell differentiation and cell differentiation induction therapy by RA; (2) roles played by RA and retinal and their mechanisms of action; (3) retinoylation, post-translational protein-modified by RA, a novel non-genomic RA mechanism of action without RA receptor; (4) new actions of β-carotene and retinol in vivo and (5) potent anticancer effects of p-dodecylaminophenol (p-DDAP), a novel vitamin A derivative created from the RA derivative fenretinide. We propose that nutritional management of vitamin A can be effective at preventing and treating diseases, and that p-DDAP is a promising anticancer drug.
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Affiliation(s)
- Noriko Takahashi
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University
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Rozanowska M, Edge R, Land EJ, Navaratnam S, Sarna T, Truscott TG. Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin. Int J Mol Sci 2023; 25:506. [PMID: 38203675 PMCID: PMC10779001 DOI: 10.3390/ijms25010506] [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: 11/18/2023] [Revised: 12/26/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 107 M-1s-1 whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4-1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules.
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Affiliation(s)
- Malgorzata Rozanowska
- Cardiff Institute of Tissue Engineering and Repair, Cardiff University, Cardiff CF10 3AX, UK
- School of Optometry and Vision Sciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Ruth Edge
- Dalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row, Cumbria CA24 3HA, UK;
| | - Edward J. Land
- The Paterson Institute, The University of Manchester, Wilmslow Road, Manchester M20 4BX, UK;
| | - Suppiah Navaratnam
- Biomedical Sciences Research Institute, University of Salford, Manchester M5 4WT, UK;
| | - Tadeusz Sarna
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland;
| | - T. George Truscott
- School of Chemical and Physical Sciences, Lennard-Jones Building, Keele University, Staffordshire ST5 5BG, UK;
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6
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Kerschensteiner D. Losing, preserving, and restoring vision from neurodegeneration in the eye. Curr Biol 2023; 33:R1019-R1036. [PMID: 37816323 PMCID: PMC10575673 DOI: 10.1016/j.cub.2023.08.044] [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] [Indexed: 10/12/2023]
Abstract
The retina is a part of the brain that sits at the back of the eye, looking out onto the world. The first neurons of the retina are the rod and cone photoreceptors, which convert changes in photon flux into electrical signals that are the basis of vision. Rods and cones are frequent targets of heritable neurodegenerative diseases that cause visual impairment, including blindness, in millions of people worldwide. This review summarizes the diverse genetic causes of inherited retinal degenerations (IRDs) and their convergence onto common pathogenic mechanisms of vision loss. Currently, there are few effective treatments for IRDs, but recent advances in disparate areas of biology and technology (e.g., genome editing, viral engineering, 3D organoids, optogenetics, semiconductor arrays) discussed here enable promising efforts to preserve and restore vision in IRD patients with implications for neurodegeneration in less approachable brain areas.
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Affiliation(s)
- Daniel Kerschensteiner
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO 63110, USA.
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7
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Ren C, Cui H, Bao X, Huang L, He S, Fong HKW, Zhao M. Proteopathy Linked to Exon-Skipping Isoform of RGR-Opsin Contributes to the Pathogenesis of Age-Related Macular Degeneration. Invest Ophthalmol Vis Sci 2023; 64:41. [PMID: 37883094 PMCID: PMC10615142 DOI: 10.1167/iovs.64.13.41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 10/09/2023] [Indexed: 10/27/2023] Open
Abstract
Purpose Proteopathy is believed to contribute to age-related macular degeneration (AMD). Much research indicates that AMD begins in the retinal pigment epithelium (RPE), which is associated with formation of extracellular drusen, a clinical hallmark of AMD. Human RPE produces a drusen-associated abnormal protein, the exon Ⅵ-skipping splice isoform of retinal G protein-coupled receptor (RGR-d). In this study, we investigate the detrimental effects of RGR-d on cultured cells and mouse retina. Methods ARPE-19 cells were stably infected by lentivirus overexpressing RGR or RGR-d and were treated with MG132, sometimes combined with or without endoplasmic reticulum (ER) stress inducer, tunicamycin. RGR and RGR-d protein expression, degeneration pathway, and potential cytotoxicity were explored. Homozygous RGR-d mice aged 8 or 14 months were fed with a high-fat diet for 3 months and then subjected to ocular examination and histopathology experiments. Results We confirm that RGR-d is proteotoxic under various conditions. In ARPE-19 cells, RGR-d is misfolded and almost completely degraded via the ubiquitin-proteasome system. Unlike normal RGR, RGR-d increases ER stress, triggers the unfolded protein response, and exerts potent cytotoxicity. Aged RGR-d mice manifest disrupted RPE cell integrity, apoptotic photoreceptors, choroidal deposition of complement C3, and CD86+CD32+ proinflammatory cell infiltration into retina and RPE-choroid. Furthermore, the AMD-like phenotype of RGR-d mice can be aggravated by a high-fat diet. Conclusions Our study confirmed the pathogenicity of the RGR splice isoform and corroborated a significant role of proteopathy in AMD. These findings may contribute to greater comprehension of the multifactorial causes of AMD.
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Affiliation(s)
- Chi Ren
- Department of Ophthalmology, Eye Disease and Optometry Institute, Peking University People's Hospital, Beijing, China
- Beijing Key Laboratory of Diagnosis and Therapy of Retinal and Choroid Diseases, Beijing, China
| | - Haoran Cui
- Department of Ophthalmology, Eye Disease and Optometry Institute, Peking University People's Hospital, Beijing, China
- Beijing Key Laboratory of Diagnosis and Therapy of Retinal and Choroid Diseases, Beijing, China
- Department of Ophthalmology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Xuan Bao
- Department of Ophthalmology, Eye Disease and Optometry Institute, Peking University People's Hospital, Beijing, China
- Beijing Key Laboratory of Diagnosis and Therapy of Retinal and Choroid Diseases, Beijing, China
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States
| | - Lvzhen Huang
- Department of Ophthalmology, Eye Disease and Optometry Institute, Peking University People's Hospital, Beijing, China
- Beijing Key Laboratory of Diagnosis and Therapy of Retinal and Choroid Diseases, Beijing, China
| | - Shikun He
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine of University of Southern California, Los Angeles, California, United States
| | - Henry K. W. Fong
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine of University of Southern California, Los Angeles, California, United States
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, California, United States
| | - Mingwei Zhao
- Department of Ophthalmology, Eye Disease and Optometry Institute, Peking University People's Hospital, Beijing, China
- Beijing Key Laboratory of Diagnosis and Therapy of Retinal and Choroid Diseases, Beijing, China
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8
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Tworak A, Kolesnikov AV, Hong JD, Choi EH, Luu JC, Palczewska G, Dong Z, Lewandowski D, Brooks MJ, Campello L, Swaroop A, Kiser PD, Kefalov VJ, Palczewski K. Rapid RGR-dependent visual pigment recycling is mediated by the RPE and specialized Müller glia. Cell Rep 2023; 42:112982. [PMID: 37585292 PMCID: PMC10530494 DOI: 10.1016/j.celrep.2023.112982] [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] [Received: 05/04/2023] [Revised: 06/14/2023] [Accepted: 07/29/2023] [Indexed: 08/18/2023] Open
Abstract
In daylight, demand for visual chromophore (11-cis-retinal) exceeds supply by the classical visual cycle. This shortfall is compensated, in part, by the retinal G-protein-coupled receptor (RGR) photoisomerase, which is expressed in both the retinal pigment epithelium (RPE) and in Müller cells. The relative contributions of these two cellular pools of RGR to the maintenance of photoreceptor light responses are not known. Here, we use a cell-specific gene reactivation approach to elucidate the kinetics of RGR-mediated recovery of photoreceptor responses following light exposure. Electroretinographic measurements in mice with RGR expression limited to either cell type reveal that the RPE and a specialized subset of Müller glia contribute both to scotopic and photopic function. We demonstrate that 11-cis-retinal formed through photoisomerization is rapidly hydrolyzed, consistent with its role in a rapid visual pigment regeneration process. Our study shows that RGR provides a pan-retinal sink for all-trans-retinal released under sustained light conditions and supports rapid chromophore regeneration through the photic visual cycle.
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Affiliation(s)
- Aleksander Tworak
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA.
| | - Alexander V Kolesnikov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA
| | - John D Hong
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA
| | - Elliot H Choi
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA
| | - Jennings C Luu
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA; Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Grazyna Palczewska
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA; Polgenix, Inc., Department of Medical Devices, Cleveland, OH 44106, USA
| | - Zhiqian Dong
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA
| | - Dominik Lewandowski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA
| | - Matthew J Brooks
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Laura Campello
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Anand Swaroop
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Philip D Kiser
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA; Department of Physiology & Biophysics, University of California, Irvine, Irvine, CA 92697, USA; Department of Clinical Pharmacy Practice, University of California, Irvine, Irvine, CA 92697, USA; Research Service, VA Long Beach Healthcare System, Long Beach, CA 90822, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA; Department of Physiology & Biophysics, University of California, Irvine, Irvine, CA 92697, USA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA 92697, USA; Department of Physiology & Biophysics, University of California, Irvine, Irvine, CA 92697, USA; Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA.
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9
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Bassetto M, Zaluski J, Li B, Zhang J, Badiee M, Kiser PD, Tochtrop GP. Tuning the Metabolic Stability of Visual Cycle Modulators through Modification of an RPE65 Recognition Motif. J Med Chem 2023; 66:8140-8158. [PMID: 37279401 PMCID: PMC10824489 DOI: 10.1021/acs.jmedchem.3c00461] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the eye, the isomerization of all-trans-retinal to 11-cis-retinal is accomplished by a metabolic pathway termed the visual cycle that is critical for vision. RPE65 is the essential trans-cis isomerase of this pathway. Emixustat, a retinoid-mimetic RPE65 inhibitor, was developed as a therapeutic visual cycle modulator and used for the treatment of retinopathies. However, pharmacokinetic liabilities limit its further development including: (1) metabolic deamination of the γ-amino-α-aryl alcohol, which mediates targeted RPE65 inhibition, and (2) unwanted long-lasting RPE65 inhibition. We sought to address these issues by more broadly defining the structure-activity relationships of the RPE65 recognition motif via the synthesis of a family of novel derivatives, which were tested in vitro and in vivo for RPE65 inhibition. We identified a potent secondary amine derivative with resistance to deamination and preserved RPE65 inhibitory activity. Our data provide insights into activity-preserving modifications of the emixustat molecule that can be employed to tune its pharmacological properties.
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Affiliation(s)
- Marco Bassetto
- Department of Physiology and Biophysics, School of Medicine, University of California - Irvine, Irvine, California 92697, United States
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, School of Medicine, University of California - Irvine, Irvine, California 92697, United States
- Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Jordan Zaluski
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Bowen Li
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Jianye Zhang
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, School of Medicine, University of California - Irvine, Irvine, California 92697, United States
| | - Mohsen Badiee
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Philip D Kiser
- Department of Physiology and Biophysics, School of Medicine, University of California - Irvine, Irvine, California 92697, United States
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, School of Medicine, University of California - Irvine, Irvine, California 92697, United States
- Department of Clinical Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University of California - Irvine, Irvine, California 92697, United States
- Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Gregory P Tochtrop
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
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10
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C. Luu J, Saadane A, Leinonen H, H. Choi E, Gao F, Lewandowski D, Halabi M, L. Sander C, Wu A, Wang JM, Singh R, Gao S, Lessieur EM, Dong Z, Palczewska G, Mullins RF, Peachey NS, Kiser PD, Tabaka M, Kern TS, Palczewski K. Stress resilience-enhancing drugs preserve tissue structure and function in degenerating retina via phosphodiesterase inhibition. Proc Natl Acad Sci U S A 2023; 120:e2221045120. [PMID: 37126699 PMCID: PMC10175720 DOI: 10.1073/pnas.2221045120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 04/02/2023] [Indexed: 05/03/2023] Open
Abstract
Chronic, progressive retinal diseases, such as age-related macular degeneration (AMD), diabetic retinopathy, and retinitis pigmentosa, arise from genetic and environmental perturbations of cellular and tissue homeostasis. These disruptions accumulate with repeated exposures to stress over time, leading to progressive visual impairment and, in many cases, legal blindness. Despite decades of research, therapeutic options for the millions of patients suffering from these disorders remain severely limited, especially for treating earlier stages of pathogenesis when the opportunity to preserve the retinal structure and visual function is greatest. To address this urgent, unmet medical need, we employed a systems pharmacology platform for therapeutic development. Through integrative single-cell transcriptomics, proteomics, and phosphoproteomics, we identified universal molecular mechanisms across distinct models of age-related and inherited retinal degenerations, characterized by impaired physiological resilience to stress. Here, we report that selective, targeted pharmacological inhibition of cyclic nucleotide phosphodiesterases (PDEs), which serve as critical regulatory nodes that modulate intracellular second messenger signaling pathways, stabilized the transcriptome, proteome, and phosphoproteome through downstream activation of protective mechanisms coupled with synergistic inhibition of degenerative processes. This therapeutic intervention enhanced resilience to acute and chronic forms of stress in the degenerating retina, thus preserving tissue structure and function across various models of age-related and inherited retinal disease. Taken together, these findings exemplify a systems pharmacology approach to drug discovery and development, revealing a new class of therapeutics with potential clinical utility in the treatment or prevention of the most common causes of blindness.
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Affiliation(s)
- Jennings C. Luu
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH44106
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Aicha Saadane
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Henri Leinonen
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
- Department of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio70211, Finland
| | - Elliot H. Choi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH44106
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Fangyuan Gao
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Dominik Lewandowski
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Maximilian Halabi
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Christopher L. Sander
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH44106
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Arum Wu
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Jacob M. Wang
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH44195
| | - Rupesh Singh
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH44195
| | - Songqi Gao
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH44106
| | - Emma M. Lessieur
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Zhiqian Dong
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Grazyna Palczewska
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Robert F. Mullins
- Institute for Vision Research, Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA52242
| | - Neal S. Peachey
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH44195
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH44106
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH44195
| | - Philip D. Kiser
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
- Department of Physiology & Biophysics, School of Medicine, University of California-Irvine, Irvine, CA92697
- Research Service, VA Long Beach Healthcare System, Long Beach, CA90822
- Department of Clinical Pharmacy Practice, University of California-Irvine, Irvine, CA92697
| | - Marcin Tabaka
- International Centre for Translational Eye Research, Warsaw01224, Poland
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01224, Poland
| | - Timothy S. Kern
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
| | - Krzysztof Palczewski
- Center for Translational Vision Research, Gavin Herbert Eye Institute, Department of Ophthalmology, University of California-Irvine, Irvine, CA92697
- Department of Physiology & Biophysics, School of Medicine, University of California-Irvine, Irvine, CA92697
- International Centre for Translational Eye Research, Warsaw01224, Poland
- Department of Chemistry, University of California-Irvine, Irvine, CA92697
- Department of Molecular Biology and Biochemistry, University of California-Irvine, Irvine, CA92697
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11
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Palczewska G, Wojtkowski M, Palczewski K. From mouse to human: Accessing the biochemistry of vision in vivo by two-photon excitation. Prog Retin Eye Res 2023; 93:101170. [PMID: 36787681 PMCID: PMC10463242 DOI: 10.1016/j.preteyeres.2023.101170] [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: 12/11/2022] [Revised: 02/03/2023] [Accepted: 02/06/2023] [Indexed: 02/13/2023]
Abstract
The eye is an ideal organ for imaging by a multi-photon excitation approach, because ocular tissues such as the sclera, cornea, lens and neurosensory retina, are highly transparent to infrared (IR) light. The interface between the retina and the retinal pigment epithelium (RPE) is especially informative, because it reflects the health of the visual (retinoid) cycle and its changes in response to external stress, genetic manipulations, and drug treatments. Vitamin A-derived retinoids, like retinyl esters, are natural fluorophores that respond to multi-photon excitation with near IR light, bypassing the filter-like properties of the cornea, lens, and macular pigments. Also, during natural aging some retinoids form bisretinoids, like diretinoid-pyridiniumethanolamine (A2E), that are highly fluorescent. These bisretinoids appear to be elevated concurrently with aging. Vitamin A-derived retinoids and bisretinoidss are detected by two-photon ophthalmoscopy (2PO), using a new class of light sources with adjustable spatial, temporal, and spectral properties. Furthermore, the two-photon (2P) absorption of IR light by the visual pigments in rod and cone photoreceptors can initiate visual transduction by cis-trans isomerization of retinal, enabling parallel functional studies. Recently we overcame concerns about safety, data interpretation and complexity of the 2P-based instrumentation, the major roadblocks toward advancing this modality to the clinic. These imaging and retina-function assessment advancements have enabled us to conduct the first 2P studies with humans.
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Affiliation(s)
- Grazyna Palczewska
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA, USA; International Center for Translational Eye Research, Polish Academy of Sciences, Warsaw, Poland; Polgenix, Inc., Department of Medical Devices, Cleveland, OH, USA; Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
| | - Maciej Wojtkowski
- International Center for Translational Eye Research, Polish Academy of Sciences, Warsaw, Poland; Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland; Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland.
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Physiology & Biophysics, School of Medicine, And Chemistry, Molecular Biology and Biochemistry, University of California, Irvine, CA, USA.
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12
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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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13
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Chromophore hydrolysis and release from photoactivated rhodopsin in native membranes. Proc Natl Acad Sci U S A 2022; 119:e2213911119. [PMID: 36322748 PMCID: PMC9659404 DOI: 10.1073/pnas.2213911119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
For sustained vision, photoactivated rhodopsin (Rho*) must undergo hydrolysis and release of all-trans-retinal, producing substrate for the visual cycle and apo-opsin available for regeneration with 11-cis-retinal. The kinetics of this hydrolysis has yet to be described for rhodopsin in its native membrane environment. We developed a method consisting of simultaneous denaturation and chromophore trapping by isopropanol/borohydride, followed by exhaustive protein digestion, complete extraction, and liquid chromatography-mass spectrometry. Using our method, we tracked Rho* hydrolysis, the subsequent formation of N-retinylidene-phosphatidylethanolamine (N-ret-PE) adducts with the released all-trans-retinal, and the reduction of all-trans-retinal to all-trans-retinol. We found that hydrolysis occurred faster in native membranes than in detergent micelles typically used to study membrane proteins. The activation energy of the hydrolysis in native membranes was determined to be 17.7 ± 2.4 kcal/mol. Our data support the interpretation that metarhodopsin II, the signaling state of rhodopsin, is the primary species undergoing hydrolysis and release of its all-trans-retinal. In the absence of NADPH, free all-trans-retinal reacts with phosphatidylethanolamine (PE), forming a substantial amount of N-ret-PE (∼40% of total all-trans-retinal at physiological pH), at a rate that is an order of magnitude faster than Rho* hydrolysis. However, N-ret-PE formation was highly attenuated by NADPH-dependent reduction of all-trans-retinal to all-trans-retinol. Neither N-ret-PE formation nor all-trans-retinal reduction affected the rate of hydrolysis of Rho*. Our study provides a comprehensive picture of the hydrolysis of Rho* and the release of all-trans-retinal and its reentry into the visual cycle, a process in which alteration can lead to severe retinopathies.
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14
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Pandey RS, Krebs MP, Bolisetty MT, Charette JR, Naggert JK, Robson P, Nishina PM, Carter GW. Single-Cell RNA Sequencing Reveals Molecular Features of Heterogeneity in the Murine Retinal Pigment Epithelium. Int J Mol Sci 2022; 23:10419. [PMID: 36142331 PMCID: PMC9499471 DOI: 10.3390/ijms231810419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 08/09/2022] [Accepted: 09/05/2022] [Indexed: 11/16/2022] Open
Abstract
Transcriptomic analysis of the mammalian retinal pigment epithelium (RPE) aims to identify cellular networks that influence ocular development, maintenance, function, and disease. However, available evidence points to RPE cell heterogeneity within native tissue, which adds complexity to global transcriptomic analysis. Here, to assess cell heterogeneity, we performed single-cell RNA sequencing of RPE cells from two young adult male C57BL/6J mice. Following quality control to ensure robust transcript identification limited to cell singlets, we detected 13,858 transcripts among 2667 and 2846 RPE cells. Dimensional reduction by principal component analysis and uniform manifold approximation and projection revealed six distinct cell populations. All clusters expressed transcripts typical of RPE cells; the smallest (C1, containing 1-2% of total cells) exhibited the hallmarks of stem and/or progenitor (SP) cells. Placing C1-6 along a pseudotime axis suggested a relative decrease in melanogenesis and SP gene expression and a corresponding increase in visual cycle gene expression upon RPE maturation. K-means clustering of all detected transcripts identified additional expression patterns that may advance the understanding of RPE SP cell maintenance and the evolution of cellular metabolic networks during development. This work provides new insights into the transcriptome of the mouse RPE and a baseline for identifying experimentally induced transcriptional changes in future studies of this tissue.
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Affiliation(s)
- Ravi S. Pandey
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Dr., Farmington, CT 06032, USA
| | - Mark P. Krebs
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA
| | - Mohan T. Bolisetty
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Dr., Farmington, CT 06032, USA
| | | | | | - Paul Robson
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Dr., Farmington, CT 06032, USA
| | - Patsy M. Nishina
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA
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15
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Chen BY, Liou JC, Wu JL, Chen CH, Yang SL. Photoreceptor and vision protective effects of astragaloside IV in mice model with light-evoked retinal damage. Biomed Pharmacother 2022; 153:113404. [DOI: 10.1016/j.biopha.2022.113404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 07/01/2022] [Accepted: 07/08/2022] [Indexed: 11/02/2022] Open
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16
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Takahashi N. Inhibitory Effects of Vitamin A and Its Derivatives on Cancer Cell Growth Not Mediated by Retinoic Acid Receptors. Biol Pharm Bull 2022; 45:1213-1224. [DOI: 10.1248/bpb.b22-00315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Noriko Takahashi
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University
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17
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Gu Y, Wang Y, Lan Y, Feng J, Zeng W, Zhang W, Lu H. Expression of Retinal G Protein-Coupled Receptor, a Member of the Opsin Family, in Human Skin Cells and Its Mediation of the Cellular Functions of Keratinocytes. Front Cell Dev Biol 2022; 10:787730. [PMID: 35445026 PMCID: PMC9014095 DOI: 10.3389/fcell.2022.787730] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 03/10/2022] [Indexed: 11/24/2022] Open
Abstract
Background: Photoreceptive proteins play critical physiological roles in human skin cells. The retinal G protein-coupled receptor (RGR) is a photoisomerase in the human retina, but its expression and cellular functions in human skin cells have not been reported. Objectives: We aimed to detect RGR expression in various skin cells and evaluate its regulation of the cellular functions of keratinocytes. Methods: The expression, distribution, and subcellular location of the RGR in normal human epidermal keratinocytes and cells with pathological conditions including psoriasis, seborrheic keratosis, and squamous cell carcinoma were determined using microscopic tools (immunohistochemical staining, immunofluorescence staining, and immunoelectron microscopy) and Western blotting (WB). The protein levels of the RGR in primary human melanocytes, keratinocytes, and fibroblasts isolated from the neonatal foreskin were measured by WB. The expression and subcellular localization of the RGR in these cells were detected by immunofluorescence staining under a fluorescence microscope and laser scanning confocal microscope. Additionally, the levels of RGR expression in normal keratinocytes exposed to ultraviolet (UV)-A or total ultraviolet radiation (UVR) in the presence or absence of all-trans-retinal were measured by WB. Furthermore, the effects of the RGR on human keratinocyte functions including proliferation, migration, and apoptosis were evaluated using the Cell Counting Kit 8, wound healing, and Transwell assays after reducing the RGR mRNA level in keratinocytes using small interfering RNA technology. Results: The RGR was primarily located in the epidermal basal and spinous layers and skin appendages. Its expression increased in psoriatic lesions, seborrheic keratosis, and squamous cell carcinoma. Confocal microscopy showed that the RGR was located in the cell membrane and nucleus of keratinocytes, melanocytes, and fibroblasts. Keratinocytes had a higher expression of the RGR than melanocytes and fibroblasts, as well as nuclear expression, according to nuclear/cytoplasmic fractionation. Colloidal gold immunoelectron microscopy technology further confirmed that the RGR is mainly located in the nucleoplasm and mitochondria and is scattered in the cytoplasm and other organelles in the epidermal keratinocytes. Notably, RGR knockdown in keratinocytes led to the inhibition of cell proliferation and migration, augmenting cell apoptosis. Conclusions: This study is the first to demonstrate the presence of RGR in the human skin. Our findings indicate that the RGR may play a critical role in the physiological function of epidermal keratinocytes.
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Affiliation(s)
- Yangguang Gu
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Yu Wang
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Yinghua Lan
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Jianglong Feng
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Wen Zeng
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Wei Zhang
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
| | - Hongguang Lu
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, China.,Department of Dermatology and Venereology, Clinical College of Medicine, Guizhou Medical University, Guiyang, China
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18
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Chen S, Getter T, Salom D, Wu D, Quetschlich D, Chorev DS, Palczewski K, Robinson CV. Capturing a rhodopsin receptor signalling cascade across a native membrane. Nature 2022; 604:384-390. [PMID: 35388214 PMCID: PMC9007743 DOI: 10.1038/s41586-022-04547-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 02/14/2022] [Indexed: 11/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are cell-surface receptors that respond to various stimuli to induce signalling pathways across cell membranes. Recent progress has yielded atomic structures of key intermediates1,2 and roles for lipids in signalling3,4. However, capturing signalling events of a wild-type receptor in real time, across a native membrane to its downstream effectors, has remained elusive. Here we probe the archetypal class A GPCR, rhodopsin, directly from fragments of native disc membranes using mass spectrometry. We monitor real-time photoconversion of dark-adapted rhodopsin to opsin, delineating retinal isomerization and hydrolysis steps, and further showing that the reaction is significantly slower in its native membrane than in detergent micelles. Considering the lipids ejected with rhodopsin, we demonstrate that opsin can be regenerated in membranes through photoisomerized retinal-lipid conjugates, and we provide evidence for increased association of rhodopsin with unsaturated long-chain phosphatidylcholine during signalling. Capturing the secondary steps of the signalling cascade, we monitor light activation of transducin (Gt) through loss of GDP to generate an intermediate apo-trimeric G protein, and observe Gαt•GTP subunits interacting with PDE6 to hydrolyse cyclic GMP. We also show how rhodopsin-targeting compounds either stimulate or dampen signalling through rhodopsin-opsin and transducin signalling pathways. Our results not only reveal the effect of native lipids on rhodopsin signalling and regeneration but also enable us to propose a paradigm for GPCR drug discovery in native membrane environments.
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Affiliation(s)
- Siyun Chen
- Chemistry Research Laboratory, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Tamar Getter
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, Irvine, CA, USA
| | - David Salom
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, Irvine, CA, USA
| | - Di Wu
- Chemistry Research Laboratory, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Daniel Quetschlich
- Chemistry Research Laboratory, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Dror S Chorev
- Chemistry Research Laboratory, University of Oxford, Oxford, UK.
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, Irvine, CA, USA.
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
- Department of Chemistry, University of California, Irvine, Irvine, CA, USA.
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, USA.
| | - Carol V Robinson
- Chemistry Research Laboratory, University of Oxford, Oxford, UK.
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK.
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19
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O’Connor C, Varshosaz P, Moise AR. Mechanisms of Feedback Regulation of Vitamin A Metabolism. Nutrients 2022; 14:nu14061312. [PMID: 35334970 PMCID: PMC8950952 DOI: 10.3390/nu14061312] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/15/2022] [Accepted: 03/17/2022] [Indexed: 02/06/2023] Open
Abstract
Vitamin A is an essential nutrient required throughout life. Through its various metabolites, vitamin A sustains fetal development, immunity, vision, and the maintenance, regulation, and repair of adult tissues. Abnormal tissue levels of the vitamin A metabolite, retinoic acid, can result in detrimental effects which can include congenital defects, immune deficiencies, proliferative defects, and toxicity. For this reason, intricate feedback mechanisms have evolved to allow tissues to generate appropriate levels of active retinoid metabolites despite variations in the level and format, or in the absorption and conversion efficiency of dietary vitamin A precursors. Here, we review basic mechanisms that govern vitamin A signaling and metabolism, and we focus on retinoic acid-controlled feedback mechanisms that contribute to vitamin A homeostasis. Several approaches to investigate mechanistic details of the vitamin A homeostatic regulation using genomic, gene editing, and chromatin capture technologies are also discussed.
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Affiliation(s)
- Catherine O’Connor
- MD Program, Northern Ontario School of Medicine, 317-MSE Bldg., 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada;
| | - Parisa Varshosaz
- Biology and Biomolecular Sciences Ph.D. Program, Northern Ontario School of Medicine, Laurentian University, Sudbury, ON P3E 2C6, Canada;
| | - Alexander R. Moise
- Medical Sciences Division, Northern Ontario School of Medicine, 317-MSE Bldg., 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada
- Department of Chemistry and Biochemistry, Biology and Biomolecular Sciences Program, Laurentian University, Sudbury, ON P3E 2C6, Canada
- Correspondence: ; Tel.: +1-705-662-7253
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20
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Miller AP, Black M, Amengual J. Fenretinide inhibits vitamin A formation from β-carotene and regulates carotenoid levels in mice. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159070. [PMID: 34742949 PMCID: PMC8688340 DOI: 10.1016/j.bbalip.2021.159070] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 10/14/2021] [Accepted: 11/02/2021] [Indexed: 02/03/2023]
Abstract
N-[4-hydroxyphenyl]retinamide, commonly known as fenretinide, a synthetic retinoid with pleiotropic benefits for human health, is currently utilized in clinical trials for cancer, cystic fibrosis, and COVID-19. However, fenretinide reduces plasma vitamin A levels by interacting with retinol-binding protein 4 (RBP4), which often results in reversible night blindness in patients. Cell culture and in vitro studies show that fenretinide binds and inhibits the activity of β-carotene oxygenase 1 (BCO1), the enzyme responsible for endogenous vitamin A formation. Whether fenretinide inhibits vitamin A synthesis in mammals, however, remains unknown. The goal of this study was to determine if the inhibition of BCO1 by fenretinide affects vitamin A formation in mice fed β-carotene. Our results show that wild-type mice treated with fenretinide for ten days had a reduction in tissue vitamin A stores accompanied by a two-fold increase in β-carotene in plasma (P < 0.01) and several tissues. These effects persisted in RBP4-deficient mice and were independent of changes in intestinal β-carotene absorption, suggesting that fenretinide inhibits vitamin A synthesis in mice. Using Bco1-/- and Bco2-/- mice we also show that fenretinide regulates intestinal carotenoid and vitamin E uptake by activating vitamin A signaling during short-term vitamin A deficiency. This study provides a deeper understanding of the impact of fenretinide on vitamin A, carotenoid, and vitamin E homeostasis, which is crucial for the pharmacological utilization of this retinoid.
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Affiliation(s)
- Anthony P Miller
- Department of Food Science and Human Nutrition, University of Illinois Urbana Champaign, Urbana, IL 61801, United States of America.
| | - Molly Black
- Department of Food Science and Human Nutrition, University of Illinois Urbana Champaign, Urbana, IL 61801, United States of America.
| | - Jaume Amengual
- Department of Food Science and Human Nutrition, University of Illinois Urbana Champaign, Urbana, IL 61801, United States of America; Division of Nutritional Sciences, University of Illinois Urbana Champaign, Urbana, IL 61801, United States of America.
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21
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Ortega JT, Jastrzebska B. Rhodopsin as a Molecular Target to Mitigate Retinitis Pigmentosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1371:61-77. [PMID: 34962636 DOI: 10.1007/5584_2021_682] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Retinitis pigmentosa (RP) is a group of hereditary degenerative diseases affecting 1 of 4000 people worldwide and being the most prevalent cause of visual handicap among working populations in developed countries. These disorders are mainly related to the abnormalities in the rod G protein-coupled receptor (GPCR), rhodopsin reflected in the dysregulated membrane trafficking, stability and phototransduction processes that lead to progressive loss of retina function and eventually blindness. Currently, there is no cure for RP, and the therapeutic options are limited. Targeting rhodopsin with small molecule chaperones to improve the folding and stability of the mutant receptor is one of the most promising pharmacological approaches to alleviate the pathology of RP. This review provides an update on the current knowledge regarding small molecule compounds that have been evaluated as rhodopsin modulators to be considered as leads for the development of novel therapies for RP.
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Affiliation(s)
- Joseph T Ortega
- Department of Pharmacology, School of Medicine, Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Beata Jastrzebska
- Department of Pharmacology, School of Medicine, Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH, USA.
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22
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Pasqualetto G, Pileggi E, Schepelmann M, Varricchio C, Rozanowska M, Brancale A, Bassetto M. Ligand-based rational design, synthesis and evaluation of novel potential chemical chaperones for opsin. Eur J Med Chem 2021; 226:113841. [PMID: 34555613 DOI: 10.1016/j.ejmech.2021.113841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 09/07/2021] [Accepted: 09/07/2021] [Indexed: 12/01/2022]
Abstract
Inherited blinding diseases retinitis pigmentosa (RP) and a subset of Leber's congenital amaurosis (LCA) are caused by the misfolding and mistrafficking of rhodopsin molecules, which aggregate and accumulate in the endoplasmic reticulum (ER), leading to photoreceptor cell death. One potential therapeutic strategy to prevent the loss of photoreceptors in these conditions is to identify opsin-binding compounds that act as chemical chaperones for opsin, aiding its proper folding and trafficking to the outer cell membrane. Aiming to identify novel compounds with such effect, a rational ligand-based approach was applied to the structure of the visual pigment chromophore, 11-cis-retinal, and its locked analogue 11-cis-6mr-retinal. Following molecular docking studies on the main chromophore binding site of rhodopsin, 49 novel compounds were synthesized according to optimized one-to seven-step synthetic routes. These agents were evaluated for their ability to compete for the chromophore binding site of opsin, and their capacity to increase the trafficking of the P23H opsin mutant from the ER to the cell membrane. Different new molecules displayed an effect in at least one assay, acting either as chemical chaperones or as stabilizers of the 9-cis-retinal-rhodopsin complex. These compounds could provide the basis to develop novel therapeutics for RP and LCA.
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Affiliation(s)
- Gaia Pasqualetto
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, CF10 3NB, UK
| | - Elisa Pileggi
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, CF10 3NB, UK
| | - Martin Schepelmann
- Institute of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, 1090, Austria; School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Carmine Varricchio
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, CF10 3NB, UK
| | - Malgorzata Rozanowska
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4HQ, UK; Cardiff Institute for Tissue Engineering and Repair (CITER), Cardiff University, Cardiff, CF10 3NB, UK
| | - Andrea Brancale
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, CF10 3NB, UK
| | - Marcella Bassetto
- Department of Chemistry, Faculty of Science and Engineering, Swansea University, Swansea, SA2 8PP, UK.
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Schlegel DK, Ramkumar S, von Lintig J, Neuhauss SC. Disturbed retinoid metabolism upon loss of rlbp1a impairs cone function and leads to subretinal lipid deposits and photoreceptor degeneration in the zebrafish retina. eLife 2021; 10:71473. [PMID: 34668483 PMCID: PMC8585484 DOI: 10.7554/elife.71473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 10/20/2021] [Indexed: 01/04/2023] Open
Abstract
The RLBP1 gene encodes the 36 kDa cellular retinaldehyde-binding protein, CRALBP, a soluble retinoid carrier, in the visual cycle of the eyes. Mutations in RLBP1 are associated with recessively inherited clinical phenotypes, including Bothnia dystrophy, retinitis pigmentosa, retinitis punctata albescens, fundus albipunctatus, and Newfoundland rod–cone dystrophy. However, the etiology of these retinal disorders is not well understood. Here, we generated homologous zebrafish models to bridge this knowledge gap. Duplication of the rlbp1 gene in zebrafish and cell-specific expression of the paralogs rlbp1a in the retinal pigment epithelium and rlbp1b in Müller glial cells allowed us to create intrinsically cell type-specific knockout fish lines. Using rlbp1a and rlbp1b single and double mutants, we investigated the pathological effects on visual function. Our analyses revealed that rlbp1a was essential for cone photoreceptor function and chromophore metabolism in the fish eyes. rlbp1a-mutant fish displayed reduced chromophore levels and attenuated cone photoreceptor responses to light stimuli. They accumulated 11-cis and all-trans-retinyl esters which displayed as enlarged lipid droplets in the RPE reminiscent of the subretinal yellow-white lesions in patients with RLBP1 mutations. During aging, these fish developed retinal thinning and cone and rod photoreceptor dystrophy. In contrast, rlbp1b mutants did not display impaired vision. The double mutant essentially replicated the phenotype of the rlbp1a single mutant. Together, our study showed that the rlbp1a zebrafish mutant recapitulated many features of human blinding diseases caused by RLBP1 mutations and provided novel insights into the pathways for chromophore regeneration of cone photoreceptors.
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Affiliation(s)
- Domino K Schlegel
- Department of Molecular Life Sciences, University of Zurich, Zürich, Switzerland
| | - Srinivasagan Ramkumar
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, United States
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, United States
| | - Stephan Cf Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Zürich, Switzerland
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24
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Kiser PD. Retinal pigment epithelium 65 kDa protein (RPE65): An update. Prog Retin Eye Res 2021; 88:101013. [PMID: 34607013 PMCID: PMC8975950 DOI: 10.1016/j.preteyeres.2021.101013] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/21/2021] [Accepted: 09/24/2021] [Indexed: 12/21/2022]
Abstract
Vertebrate vision critically depends on an 11-cis-retinoid renewal system known as the visual cycle. At the heart of this metabolic pathway is an enzyme known as retinal pigment epithelium 65 kDa protein (RPE65), which catalyzes an unusual, possibly biochemically unique, reaction consisting of a coupled all-trans-retinyl ester hydrolysis and alkene geometric isomerization to produce 11-cis-retinol. Early work on this isomerohydrolase demonstrated its membership to the carotenoid cleavage dioxygenase superfamily and its essentiality for 11-cis-retinal production in the vertebrate retina. Three independent studies published in 2005 established RPE65 as the actual isomerohydrolase instead of a retinoid-binding protein as previously believed. Since the last devoted review of RPE65 enzymology appeared in this journal, major advances have been made in a number of areas including our understanding of the mechanistic details of RPE65 isomerohydrolase activity, its phylogenetic origins, the relationship of its membrane binding affinity to its catalytic activity, its role in visual chromophore production for rods and cones, its modulation by macromolecules and small molecules, and the involvement of RPE65 mutations in the development of retinal diseases. In this article, I will review these areas of progress with the goal of integrating results from the varied experimental approaches to provide a comprehensive picture of RPE65 biochemistry. Key outstanding questions that may prove to be fruitful future research pursuits will also be highlighted.
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Affiliation(s)
- Philip D Kiser
- Research Service, VA Long Beach Healthcare System, Long Beach, CA, 90822, USA; Department of Physiology & Biophysics, University of California, Irvine School of Medicine, Irvine, CA, 92697, USA; Department of Ophthalmology and Center for Translational Vision Research, Gavin Herbert Eye Institute, University of California, Irvine School of Medicine, Irvine, CA, 92697, USA.
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25
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Opsins outside the eye and the skin: a more complex scenario than originally thought for a classical light sensor. Cell Tissue Res 2021; 385:519-538. [PMID: 34236517 DOI: 10.1007/s00441-021-03500-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 06/23/2021] [Indexed: 12/19/2022]
Abstract
Since the discovery of melanopsin as a retinal non-visual photopigment, opsins have been described in several organs and cells. This distribution is strikingly different from the classical localization of photopigments in light-exposed tissues such as the eyes and the skin. More than 10 years ago, a new paradigm in the field was created as opsins were shown, to detect not only light, but also thermal energy in Drosophila. In agreement with these findings, thermal detection by opsins was also reported in mammalian cells. Considering the presence of opsins in tissues not reached by light, an intriguing question has emerged: What is the role of a classical light-sensor, and more recently appreciated thermo-sensor, in these tissues? To tackle this question, we address in this review the most recent studies in the field, with emphasis in mammals. We provide the present view about the role of opsins in peripheral tissues, aiming to integrate the current knowledge of the presence and function of opsins in organs that are not directly affected by light.
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Takahashi N, Saito D, Hasegawa S, Yamasaki M, Imai M. Vitamin A in health care: Suppression of growth and induction of differentiation in cancer cells by vitamin A and its derivatives and their mechanisms of action. Pharmacol Ther 2021; 230:107942. [PMID: 34175370 DOI: 10.1016/j.pharmthera.2021.107942] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/13/2021] [Accepted: 06/03/2021] [Indexed: 02/06/2023]
Abstract
Vitamin A is an important micro-essential nutrient, whose primary dietary source is retinyl esters. In addition, β-carotene (pro-vitamin A) is a precursor of vitamin A contained in green and yellow vegetables that is converted to retinol in the body after ingestion. Retinol is oxidized to produce visual retinal, which is further oxidized to retinoic acid (RA), which is used as a therapeutic agent for patients with promyelocytic leukemia. Thus, the effects of retinal and RA are well known. In this paper, we will introduce (1) vitamin A circulation in the body, (2) the actions and mechanisms of retinal and RA, (3) retinoylation: another RA mechanism not depending on RA receptors, (4) the relationship between cancer and actions of retinol or β-carotene, whose roles in vivo are still unknown, and (5) anti-cancer actions of vitamin A derivatives derived from fenretinide (4-HPR). We propose that vitamin A nutritional management is effective in the prevention of cancer.
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Affiliation(s)
- Noriko Takahashi
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan.
| | - Daisuke Saito
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Shinya Hasegawa
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Masahiro Yamasaki
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Masahiko Imai
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
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Koch M, Scheel C, Ma H, Yang F, Stadlmeier M, Glück AF, Murenu E, Traube FR, Carell T, Biel M, Ding XQ, Michalakis S. The cGMP-Dependent Protein Kinase 2 Contributes to Cone Photoreceptor Degeneration in the Cnga3-Deficient Mouse Model of Achromatopsia. Int J Mol Sci 2020; 22:E52. [PMID: 33374621 PMCID: PMC7793084 DOI: 10.3390/ijms22010052] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 12/21/2022] Open
Abstract
Mutations in the CNGA3 gene, which encodes the A subunit of the cyclic guanosine monophosphate (cGMP)-gated cation channel in cone photoreceptor outer segments, cause total colour blindness, also referred to as achromatopsia. Cones lacking this channel protein are non-functional, accumulate high levels of the second messenger cGMP and degenerate over time after induction of ER stress. The cell death mechanisms that lead to loss of affected cones are only partially understood. Here, we explored the disease mechanisms in the Cnga3 knockout (KO) mouse model of achromatopsia. We found that another important effector of cGMP, the cGMP-dependent protein kinase 2 (Prkg2) is crucially involved in cGMP cytotoxicity of cones in Cnga3 KO mice. Virus-mediated knockdown or genetic ablation of Prkg2 in Cnga3 KO mice counteracted degeneration and preserved the number of cones. Analysis of markers of endoplasmic reticulum stress and unfolded protein response confirmed that induction of these processes in Cnga3 KO cones also depends on Prkg2. In conclusion, we identified Prkg2 as a novel key mediator of cone photoreceptor degeneration in achromatopsia. Our data suggest that this cGMP mediator could be a novel pharmacological target for future neuroprotective therapies.
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Affiliation(s)
- Mirja Koch
- Department of Pharmacy—Center for Drug Research, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.K.); (C.S.); (E.M.); (M.B.)
| | - Constanze Scheel
- Department of Pharmacy—Center for Drug Research, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.K.); (C.S.); (E.M.); (M.B.)
| | - Hongwei Ma
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (H.M.); (F.Y.); (X.-Q.D.)
| | - Fan Yang
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (H.M.); (F.Y.); (X.-Q.D.)
| | - Michael Stadlmeier
- Department of Chemistry, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.S.); (A.F.G.); (F.R.T.); (T.C.)
| | - Andrea F. Glück
- Department of Chemistry, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.S.); (A.F.G.); (F.R.T.); (T.C.)
| | - Elisa Murenu
- Department of Pharmacy—Center for Drug Research, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.K.); (C.S.); (E.M.); (M.B.)
- Department of Ophthalmology, Ludwig-Maximilians-University, 80336 Munich, Germany
| | - Franziska R. Traube
- Department of Chemistry, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.S.); (A.F.G.); (F.R.T.); (T.C.)
| | - Thomas Carell
- Department of Chemistry, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.S.); (A.F.G.); (F.R.T.); (T.C.)
| | - Martin Biel
- Department of Pharmacy—Center for Drug Research, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.K.); (C.S.); (E.M.); (M.B.)
| | - Xi-Qin Ding
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (H.M.); (F.Y.); (X.-Q.D.)
| | - Stylianos Michalakis
- Department of Pharmacy—Center for Drug Research, Ludwig-Maximilians-University, 81377 Munich, Germany; (M.K.); (C.S.); (E.M.); (M.B.)
- Department of Ophthalmology, Ludwig-Maximilians-University, 80336 Munich, Germany
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