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DeRamus ML, Jasien JV, Eppstein JM, Koala P, Kraft TW. Retinal Responses to Visual Stimuli in Interphotoreceptor Retinoid Binding-Protein Knock-Out Mice. Int J Mol Sci 2023; 24:10655. [PMID: 37445836 PMCID: PMC10341985 DOI: 10.3390/ijms241310655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/07/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is an abundant glycoprotein in the subretinal space bound by the photoreceptor (PR) outer segments and the processes of the retinal pigmented epithelium (RPE). IRBP binds retinoids, including 11-cis-retinal and all-trans-retinol. In this study, visual function for demanding visual tasks was assessed in IRBP knock-out (KO) mice. Surprisingly, IRBP KO mice showed no differences in scotopic critical flicker frequency (CFF) compared to wildtype (WT). However, they did have lower photopic CFF than WT. IRBP KO mice had reduced scotopic and photopic acuity and contrast sensitivity compared to WT. IRBP KO mice had a significant reduction in outer nuclear layer (ONL) thickness, PR outer and inner segment, and full retinal thickness (FRT) compared to WT. There were fewer cones in IRBP KO mice. Overall, these results confirm substantial loss of rods and significant loss of cones within 30 days. Absence of IRBP resulted in cone circuit damage, reducing photopic flicker, contrast sensitivity, and spatial frequency sensitivity. The c-wave was reduced and accelerated in response to bright steps of light. This result also suggests altered retinal pigment epithelium activity. There appears to be a compensatory mechanism such as higher synaptic gain between PRs and bipolar cells since the loss of the b-wave did not linearly follow the loss of rods, or the a-wave. Scotopic CFF is normal despite thinning of ONL and reduced scotopic electroretinogram (ERG) in IRBP KO mice, suggesting either a redundancy or plasticity in circuits detecting (encoding) scotopic flicker at threshold even with substantial rod loss.
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Affiliation(s)
| | | | | | | | - Timothy W. Kraft
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (J.V.J.); (J.M.E.); (P.K.)
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2
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Asatryan A, Calandria JM, Kautzmann MAI, Jun B, Gordon WC, Do KV, Bhattacharjee S, Pham TL, Bermúdez V, Mateos MV, Heap J, Bazan NG. New Retinal Pigment Epithelial Cell Model to Unravel Neuroprotection Sensors of Neurodegeneration in Retinal Disease. Front Neurosci 2022; 16:926629. [PMID: 35873810 PMCID: PMC9301569 DOI: 10.3389/fnins.2022.926629] [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: 04/22/2022] [Accepted: 05/30/2022] [Indexed: 01/02/2023] Open
Abstract
Retinal pigment epithelial (RPE) cells sustain photoreceptor integrity, and when this function is disrupted, retinal degenerations ensue. Herein, we characterize a new cell line from human RPE that we termed ABC. These cells remarkably recapitulate human eye native cells. Distinctive from other epithelia, RPE cells originate from the neural crest and follow a neural development but are terminally differentiated into "epithelial" type, thus sharing characteristics with their neuronal lineages counterparts. Additionally, they form microvilli, tight junctions, and honeycomb packing and express distinctive markers. In these cells, outer segment phagocytosis, phagolysosome fate, phospholipid metabolism, and lipid mediator release can be studied. ABC cells display higher resistance to oxidative stress and are protected from senescence through mTOR inhibition, making them more stable in culture. The cells are responsive to Neuroprotectin D1 (NPD1), which downregulates inflammasomes and upregulates antioxidant and anti-inflammatory genes. ABC gene expression profile displays close proximity to native RPE lineage, making them a reliable cell system to unravel signaling in uncompensated oxidative stress (UOS) and retinal degenerative disease to define neuroprotection sites.
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Affiliation(s)
- Aram Asatryan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Jorgelina M Calandria
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Marie-Audrey I Kautzmann
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - William C Gordon
- 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
| | - Surjyadipta Bhattacharjee
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Thang L Pham
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Vicente Bermúdez
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Melina Valeria Mateos
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Jessica Heap
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
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3
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Miyagishima KJ, Sharma R, Nimmagadda M, Clore-Gronenborn K, Qureshy Z, Ortolan D, Bose D, Farnoodian M, Zhang C, Fausey A, Sergeev YV, Abu-Asab M, Jun B, Do KV, Kautzman Guerin MA, Calandria J, George A, Guan B, Wan Q, Sharp RC, Cukras C, Sieving PA, Hufnagel RB, Bazan NG, Boesze-Battaglia K, Miller S, Bharti K. AMPK modulation ameliorates dominant disease phenotypes of CTRP5 variant in retinal degeneration. Commun Biol 2021; 4:1360. [PMID: 34887495 PMCID: PMC8660775 DOI: 10.1038/s42003-021-02872-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/09/2021] [Indexed: 12/13/2022] Open
Abstract
Late-onset retinal degeneration (L-ORD) is an autosomal dominant disorder caused by a missense substitution in CTRP5. Distinctive clinical features include sub-retinal pigment epithelium (RPE) deposits, choroidal neovascularization, and RPE atrophy. In induced pluripotent stem cells-derived RPE from L-ORD patients (L-ORD-iRPE), we show that the dominant pathogenic CTRP5 variant leads to reduced CTRP5 secretion. In silico modeling suggests lower binding of mutant CTRP5 to adiponectin receptor 1 (ADIPOR1). Downstream of ADIPOR1 sustained activation of AMPK renders it insensitive to changes in AMP/ATP ratio resulting in defective lipid metabolism, reduced Neuroprotectin D1(NPD1) secretion, lower mitochondrial respiration, and reduced ATP production. These metabolic defects result in accumulation of sub-RPE deposits and leave L-ORD-iRPE susceptible to dedifferentiation. Gene augmentation of L-ORD-iRPE with WT CTRP5 or modulation of AMPK, by metformin, re-sensitize L-ORD-iRPE to changes in cellular energy status alleviating the disease cellular phenotypes. Our data suggests a mechanism for the dominant behavior of CTRP5 mutation and provides potential treatment strategies for L-ORD patients.
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Affiliation(s)
- Kiyoharu J. Miyagishima
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Ruchi Sharma
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Malika Nimmagadda
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Katharina Clore-Gronenborn
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Zoya Qureshy
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Davide Ortolan
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Devika Bose
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Mitra Farnoodian
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Congxiao Zhang
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Andrew Fausey
- grid.280030.90000 0001 2150 6316Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD 20892 USA
| | - Yuri V. Sergeev
- grid.280030.90000 0001 2150 6316Ophthalmic Genetics and Visual Function Branch, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Mones Abu-Asab
- grid.280030.90000 0001 2150 6316Section of Histopathology, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Bokkyoo Jun
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Khanh V. Do
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Marie-Audrey Kautzman Guerin
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Jorgelina Calandria
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Aman George
- grid.280030.90000 0001 2150 6316Ophthalmic Genetics and Visual Function Branch, National Eye Institute, NIH, Bethesda, MD 20892 USA
| | - Bin Guan
- grid.280030.90000 0001 2150 6316Medical Genetics and Ophthalmic Genomics Unit, NEI, NIH, Bethesda, MD 20892 USA
| | - Qin Wan
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Rachel C. Sharp
- grid.25879.310000 0004 1936 8972Department of Biochemistry University of Pennsylvania, 240 South 40th Street, Levy Building, Room 515, Philadelphia, PA 19104 USA
| | - Catherine Cukras
- grid.280030.90000 0001 2150 6316Division of Epidemiology and Clinical Applications and Ophthalmic Genetics and Visual Function Branch, NEI, NIH, Bethesda, MD 20892 USA
| | - Paul A. Sieving
- grid.280030.90000 0001 2150 6316Section for Translation Research in Retinal and Macular Degeneration, NEI, NIH, Bethesda, MD 20892 USA
| | - Robert B. Hufnagel
- grid.280030.90000 0001 2150 6316Medical Genetics and Ophthalmic Genomics Unit, NEI, NIH, Bethesda, MD 20892 USA
| | - Nicolas G. Bazan
- grid.279863.10000 0000 8954 1233Neuroscience Center of Excellence, Louisiana State University Health, New Orleans, LA 70112 USA
| | - Kathleen Boesze-Battaglia
- grid.25879.310000 0004 1936 8972Department of Biochemistry University of Pennsylvania, 240 South 40th Street, Levy Building, Room 515, Philadelphia, PA 19104 USA
| | - Sheldon Miller
- grid.280030.90000 0001 2150 6316Section on Epithelial and Retinal Physiology and Disease, NEI, NIH, Bethesda, MD 20892 USA
| | - Kapil Bharti
- Ocular and Stem Cell Translational Research Section, NEI, NIH, Bethesda, MD, 20892, USA.
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4
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Ruiz-Pastor MJ, Kutsyr O, Lax P, Cuenca N. Decrease in DHA and other fatty acids correlates with photoreceptor degeneration in retinitis pigmentosa. Exp Eye Res 2021; 209:108667. [PMID: 34119484 DOI: 10.1016/j.exer.2021.108667] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/21/2021] [Accepted: 06/07/2021] [Indexed: 10/21/2022]
Abstract
Fatty acids, and especially docosahexaenoic acid (DHA), are essential for photoreceptor cell integrity and are involved in the phototransduction cascade. In this study, we analyzed the changes in the fatty acid profile in the retina of the rd10 mouse, model of retinitis pigmentosa, in order to identify potential risk factors for retinal degeneration and possible therapeutic approaches. Fatty acids from C57BL/6J and rd10 mouse retinas were extracted with Folch's method and analyzed by gas chromatography/mass spectrometry. Changes in retinal morphology were evaluated by immunohistochemistry. The rd10 mouse retina showed a decreased number of photoreceptor rows and alterations in photoreceptor morphology compared to C57BL/6J mice. The total amount of fatty acids dropped by 29.4% in the dystrophic retinas compared to C57BL/6J retinas. A positive correlation was found between the retinal content of specific fatty acids and the number of photoreceptor rows. We found that the amount of several short-chain and long-chain saturated fatty acids, as well as monounsaturated fatty acids, decreased in the retina of rd10 mice. Moreover, the content of the n-6 polyunsaturated fatty acid arachidonic acid and the n-3 polyunsaturated DHA decreased markedly in the dystrophic retina. The fall of DHA was more pronounced, hence the n-6/n-3 ratio was significantly increased in the diseased retina. The content of specific fatty acids in the retina decreased with photoreceptor degeneration in retinitis pigmentosa mice, with a remarkable reduction in DHA and other saturated and unsaturated fatty acids. These fatty acids could be essential for photoreceptor cell viability, and they should be evaluated for the design of therapeutical strategies and nutritional supplements.
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Affiliation(s)
- María José Ruiz-Pastor
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Oksana Kutsyr
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Pedro Lax
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
| | - Nicolás Cuenca
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
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5
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Ghosh D, Haswell KM, Sprada M, Gonzalez-Fernandez F. Structure of zebrafish IRBP reveals fatty acid binding. Exp Eye Res 2015; 140:149-158. [PMID: 26344741 DOI: 10.1016/j.exer.2015.08.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 08/22/2015] [Accepted: 08/31/2015] [Indexed: 10/23/2022]
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) has a remarkable role in targeting and protecting all-trans and 11-cis retinol, and 11-cis retinal during the rod and cone visual cycles. Little is known about how the correct retinoid is efficiently delivered and removed from the correct cell at the required time. It has been proposed that different fatty composition at that the outer-segments and retinal-pigmented epithelium have an important role is regulating the delivery and uptake of the visual cycle retinoids at the cell-interphotoreceptor-matrix interface. Although this suggests intriguing mechanisms for the role of local fatty acids in visual-cycle retinoid trafficking, nothing is known about the structural basis of IRBP-fatty acid interactions. Such regulation may be mediated through IRBP's unusual repeating homologous modules, each containing about 300 amino acids. We have been investigating structure-function relationships of Zebrafish IRBP (zIRBP), which has only two tandem modules (z1 and z2), as a model for the more complex four-module mammalian IRBP's. Here we report the first X-ray crystal structure of a teleost IRBP, and the only structure with a bound ligand. The X-ray structure of z1, determined at 1.90 Å resolution, reveals a two-domain organization of the module (domains A and B). A deep hydrophobic pocket with a single bound molecule of oleic acid was identified within the N-terminal domain A. In fluorescence titrations assays, oleic acid displaced all-trans retinol from zIRBP. Our study, which provides the first structure of an IRBP with bound ligand, supports a potential role for fatty acids in regulating retinoid binding.
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Affiliation(s)
- Debashis Ghosh
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, NY, USA.
| | - Karen M Haswell
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, NY, USA
| | - Molly Sprada
- SUNY Eye Institute, State University of New York, USA
| | - Federico Gonzalez-Fernandez
- Medical Research & Development Service, G.V. (Sonny) Veterans Affairs Medical Center, Jackson, MS, USA; Departments of Ophthalmology and Pathology, University of Mississippi Medical Center, Jackson, MS, USA; SUNY Eye Institute, State University of New York, USA.
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6
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Ishikawa M, Sawada Y, Yoshitomi T. Structure and function of the interphotoreceptor matrix surrounding retinal photoreceptor cells. Exp Eye Res 2015; 133:3-18. [DOI: 10.1016/j.exer.2015.02.017] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 02/20/2015] [Accepted: 02/20/2015] [Indexed: 12/21/2022]
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7
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Garlipp MA, Gonzalez-Fernandez F. Cone outer segment and Müller microvilli pericellular matrices provide binding domains for interphotoreceptor retinoid-binding protein (IRBP). Exp Eye Res 2013; 113:192-202. [DOI: 10.1016/j.exer.2013.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 01/24/2013] [Accepted: 02/04/2013] [Indexed: 10/27/2022]
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8
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Bazan NG, Molina MF, Gordon WC. Docosahexaenoic acid signalolipidomics in nutrition: significance in aging, neuroinflammation, macular degeneration, Alzheimer's, and other neurodegenerative diseases. Annu Rev Nutr 2011; 31:321-51. [PMID: 21756134 DOI: 10.1146/annurev.nutr.012809.104635] [Citation(s) in RCA: 303] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Essential polyunsaturated fatty acids (PUFAs) are critical nutritional lipids that must be obtained from the diet to sustain homeostasis. Omega-3 and -6 PUFAs are key components of biomembranes and play important roles in cell integrity, development, maintenance, and function. The essential omega-3 fatty acid family member docosahexaenoic acid (DHA) is avidly retained and uniquely concentrated in the nervous system, particularly in photoreceptors and synaptic membranes. DHA plays a key role in vision, neuroprotection, successful aging, memory, and other functions. In addition, DHA displays anti-inflammatory and inflammatory resolving properties in contrast to the proinflammatory actions of several members of the omega-6 PUFAs family. This review discusses DHA signalolipidomics, comprising the cellular/tissue organization of DHA uptake, its distribution among cellular compartments, the organization and function of membrane domains rich in DHA-containing phospholipids, and the cellular and molecular events revealed by the uncovering of signaling pathways regulated by DHA and docosanoids, the DHA-derived bioactive lipids, which include neuroprotectin D1 (NPD1), a novel DHA-derived stereoselective mediator. NPD1 synthesis agonists include neurotrophins and oxidative stress; NPD1 elicits potent anti-inflammatory actions and prohomeostatic bioactivity, is anti-angiogenic, promotes corneal nerve regeneration, and induces cell survival. In the context of DHA signalolipidomics, this review highlights aging and the evolving studies on the significance of DHA in Alzheimer's disease, macular degeneration, Parkinson's disease, and other brain disorders. DHA signalolipidomics in the nervous system offers emerging targets for pharmaceutical intervention and clinical translation.
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Affiliation(s)
- Nicolas G Bazan
- Neuroscience Center of Excellence and Department of Ophthalmology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
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9
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Bazan NG. Cellular and molecular events mediated by docosahexaenoic acid-derived neuroprotectin D1 signaling in photoreceptor cell survival and brain protection. Prostaglandins Leukot Essent Fatty Acids 2009; 81:205-11. [PMID: 19520558 PMCID: PMC2756692 DOI: 10.1016/j.plefa.2009.05.024] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Deficiency in docosahexaenoic acid (DHA) is associated with impaired visual and neurological postnatal development, cognitive decline, macular degeneration, and other neurodegenerative diseases. DHA is an omega-3 polyunsaturated fatty acyl chain concentrated in phospholipids of brain and retina, with photoreceptor cells displaying the highest content of DHA of all cell membranes. The identification and characterization of neuroprotectin D1 (NPD1, 10R, 17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid) contributes in understanding the biological significance of DHA. In oxidative stress-challenged human retinal pigment epithelial (RPE) cells, human brain cells, or rat brains undergoing ischemia-reperfusion, NPD1 synthesis is enhanced as a response for sustaining homeostasis. Thus, neurotrophins, Abeta peptide 42 (Abeta42), calcium ionophore A23187, interleukin (IL)-1beta, or DHA supply enhances NPD1 synthesis. NPD1, in turn, up-regulates the antiapoptotic proteins of the Bcl-2 family and decreases the expression of proapoptotic Bcl-2 family members. Moreover, NPD1 inhibits IL-1beta-stimulated expression of cyclooxygenase-2 (COX-2). Because both RPE and photoreceptors are damaged and then die in retinal degenerations, elucidating how NPD1 signaling contributes to retinal cell survival may lead to a new understanding of disease mechanisms. In human neural cells, DHA attenuates amyloid-beta (Abeta) secretion, resulting in concomitant formation of NPD1. NPD1 was found to be reduced in the Alzheimer's disease (AD) cornu ammonis region 1 (CA1) hippocampal region, but not in other areas of the brain. The expression of key enzymes for NPD1 biosynthesis, cytosolic phospholipase A(2) (cPLA(2)), and 15-lipoxygenase (15-LOX) was found altered in the AD hippocampal CA1 region. NPD1 repressed Abeta42-triggered activation of pro-inflammatory genes and upregulated the antiapoptotic genes encoding Bcl-2, Bcl-xl, and Bfl-1(A1) in human brain cells in culture. Overall, these results support the concept that NPD1 promotes brain and retina cell survival via the induction of antiapoptotic and neuroprotective gene-expression programs that suppress Abeta42-induced neurotoxicity and other forms of cell injury, which in turn fosters homeostasis during development in aging, as well as during the initiation and progression of neurodegenerative diseases.
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Affiliation(s)
- Nicolas G Bazan
- Neuroscience Center of Excellence and Department of Ophthalmology, School of Medicine, Louisiana State University Health Sciences Center, 2020 Gravier Street, Suite D, New Orleans, LA 70112, USA.
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11
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BAZAN NICOLASG, MARCHESELLI VICTORL, COLE-EDWARDS KASIE. Brain Response to Injury and Neurodegeneration. Ann N Y Acad Sci 2008. [DOI: 10.1111/j.1749-6632.2005.tb00018.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Watkins PA, Hamilton JA. Roundtable discussion of session 4: fatty acids and lipids in brain disorders. J Mol Neurosci 2007; 33:120-4. [PMID: 17901556 DOI: 10.1007/s12031-007-0054-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 11/30/2022]
Affiliation(s)
- Paul A Watkins
- Kennedy Krieger Institute, 707 North Broadway, Baltimore, MD 21205, USA.
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13
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Bazan NG. The Onset of Brain Injury and Neurodegeneration Triggers the Synthesis of Docosanoid Neuroprotective Signaling. Cell Mol Neurobiol 2006; 26:901-13. [PMID: 16897369 DOI: 10.1007/s10571-006-9064-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Accepted: 03/14/2006] [Indexed: 11/26/2022]
Abstract
Bioactive lipid messengers are formed through phospholipase-mediated cleavage of specific phospholipids from membrane reservoirs. Effectors that activate the synthesis of lipid messengers, include ion channels, neurotransmitters, membrane depolarization, cytokines, and neurotrophic factors. In turn, lipid messengers regulate and interact with multiple pathways, participating in the development, differentiation, function (e.g., long-term potentiation and memory), protection, and repair of cells of the nervous system. Overall, bioactive lipids participate in the regulation of synaptic function and dysfunction. Platelet-activating factor (PAF) and COX-2-synthesized PGE(2) modulate synaptic plasticity and memory. Oxidative stress disrupts lipid signaling, fosters lipid peroxidation, and initiates and propagates neurodegeneration. Lipid messengers participate in the interactions among neurons, astrocytes, oligodendrocytes, microglia, cells of the microvasculature, and other cells. A conglomerate of interrelated cells comprises the neurovascular unit. Signaling at the neurovascular unit is clearly altered in the early stages of cerebrovascular disease as well as in neurodegenerations. Here we will provide examples of how signaling by lipids regulates critical events essential for neuronal survival. We will highlight a newly identified, DHA-derived messenger, neuroprotectin D1, which attenuates oxidative stress-induced apoptosis. The specificity and potency of this novel docosanoid (neuroprotectin D1) indicate a potentially important target for therapeutic intervention.
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Affiliation(s)
- Nicolas G Bazan
- LSU Neuroscience Center and Department of Ophthalmology, Louisiana State University Health Sciences Center School of Medicine in New Orleans, New Orleans 70112, USA.
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14
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Best CA, Laposata M, Proios VG, Szczepiorkowski ZM. METHOD TO ASSESS FATTY ACID ETHYL ESTER BINDING TO ALBUMIN. Alcohol Alcohol 2006; 41:240-6. [PMID: 16554377 DOI: 10.1093/alcalc/agl009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS To develop a method to assess the relative binding of fatty acid ethyl esters (FAEE) and free fatty acids (FFA) to albumin, and to determine if binding affinity is related to fatty acid chain length and or degree of saturation. METHODS Radiolabelled ethyl-[14C] oleate bound to albumin was challenged with various ratios of FFA to FAEE. The displacement of ethyl-[14C] oleate by FFA was visualized and quantitated through a combination of native-PAGE, autoradiography, and liquid scintillation counting (LSC). RESULTS As the ratio of FFA to FAEE increased from 0:1 to 12:1, for all fatty acids tested (myristate, palmitate, stearate, oleate, linoleate, and arachidonate), ethyl-[14C] oleate displacement increased, when expressed as radioactivity (in DPM) as a percentage of control. In contrast, ethyl oleate did not displace stearate or oleate from albumin at molar ratios up to 5:1 (FAEE:FFA). CONCLUSIONS The method developed gave reproducible visualization of noncovalent binding of radiolabelled FAEE to albumin. The combination of native-PAGE and autoradiography LSC works well in assessing the binding properties of albumin and radiolabelled FAEE. The data indicate preferential binding of FFA over FAEE to albumin with six different FFA displacing FAEE to an approximately equal extent.
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Affiliation(s)
- Catherine A Best
- Department of Biomedical Sciences, Northeastern University, Boston, MA 02115, USA.
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15
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Abstract
Feeding dams a diet enriched with DHA during gestation and lactation has been associated with improvements in neurologic development of their puppies. Also, feeding diets or supplements containing DHA may improve memory or learning in young dogs.
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Affiliation(s)
- Kimberly M Heinemann
- Comparative Nutrition Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843, USA
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16
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Avichezer D, Liou GI, Chan CC, Lewis GM, Wiggert B, Donoso LA, Nickerson JM, Crawford MA, Caspi RR. Interphotoreceptor retinoid-binding protein (IRBP)-deficient C57BL/6 mice have enhanced immunological and immunopathogenic responses to IRBP and an altered recognition of IRBP epitopes. J Autoimmun 2004; 21:185-94. [PMID: 14599843 DOI: 10.1016/j.jaut.2003.08.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Experimental autoimmune uveitis (EAU) and pinealitis (EAP) can be induced in susceptible mice by immunization with immunologically privileged retinal antigens. In the present study, we analyzed the immunologic and immunopathologic responses of mice deficient in the retinal autoantigen interphotoreceptor retinoid-binding protein (IRBP). The consequences of IRBP deficiency on the T-cell repertoire were also investigated. IRBP+/+, IRBP+/- and IRBP-/- mice on the C57BL/6 background were immunized with IRBP or with a pathogenic epitope, IRBP(1-20) peptide in adjuvant, and were evaluated for disease severity and immunological responses. C57BL/6 IRBP-/- mice were completely resistant to EAU and EAP, and had enhanced immunological responses to IRBP and to its pathogenic peptide 1-20, as compared to their IRBP+/+ counterparts. IRBP-/- mice exhibited an altered IRBP epitope recognition. T cell epitope mapping revealed a response to IRBP peptide 271-290 in IRBP-/- mice, that was absent in the wild type. Primed T cells of IRBP-/- mice transferred an exacerbated form of EAU to nai;ve wild type recipients. A gene-dose effect was evident in that C57BL/6 IRBP+/- mice, exhibited intermediate immunological responses and lower disease scores compared to wild type. We conclude that expression of IRBP in target tissues is a necessary prerequisite for disease induction, excluding other retinoid-binding or vision-related proteins as surrogate targets. Furthermore, endogenous expression of IRBP is directly responsible for lowering the threshold of susceptibility to uveitic disease.
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Affiliation(s)
- Dody Avichezer
- Laboratory of Immunology, Section of Immunoregulation, National Institutes of Health, 10 Center Drive, 10/10N222, Bethesda, MD 20892-1857, USA
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17
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Mukherjee PK, Marcheselli VL, Serhan CN, Bazan NG. Neuroprotectin D1: a docosahexaenoic acid-derived docosatriene protects human retinal pigment epithelial cells from oxidative stress. Proc Natl Acad Sci U S A 2004; 101:8491-6. [PMID: 15152078 PMCID: PMC420421 DOI: 10.1073/pnas.0402531101] [Citation(s) in RCA: 521] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Docosahexaenoic acid (DHA) is a lipid peroxidation target in oxidative injury to retinal pigment epithelium (RPE) and retina. Photoreceptor and synaptic membranes share the highest content of DHA of all cell membranes. This fatty acid is required for RPE functional integrity; however, it is not known whether specific mediators generated from DHA contribute to its biological significance. We used human ARPE-19 cells and demonstrated the synthesis of 10,17S-docosatriene [neuroprotectin D1 (NPD1)]. This synthesis was enhanced by the calcium ionophore A-23187, by IL-1beta, or by supplying DHA. Under these conditions, there is a time-dependent release of endogenous free DHA followed by NPD1 formation, suggesting that phospholipase A(2) releases the mediator's precursor. Added NPD1 potently counteracted H(2)O(2)/tumor necrosis factor alpha oxidative-stress-triggered apoptotic RPE DNA damage. NPD1 also up-regulated the antiapoptotic proteins Bcl-2 and Bcl-x(L) and decreased proapoptotic Bax and Bad expression. Moreover, NPD1 (50 nM) inhibited oxidative-stress-induced caspase-3 activation. NPD1 also inhibited IL-1beta-stimulated expression of cyclooxygenase 2 promoter transfected into ARPE-19 cells. Overall, NPD1 protected RPE cells from oxidative-stress-induced apoptosis, and we predict that it will similarly protect neurons. This lipid mediator therefore may indirectly contribute to photoreceptor cell survival as well. Because both RPE and photoreceptor cells die in retinal degenerations, our findings contribute to the understanding of retinal cell survival signaling and potentially to the development of new therapeutic strategies.
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Affiliation(s)
- Pranab K Mukherjee
- Neuroscience Center of Excellence and Department of Ophthalmology, Louisiana State University Health Sciences Center School of Medicine, New Orleans, LA 70112, USA
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18
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Gonzalez-Fernandez F. Interphotoreceptor retinoid-binding protein--an old gene for new eyes. Vision Res 2004; 43:3021-36. [PMID: 14611938 DOI: 10.1016/j.visres.2003.09.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evolving 40 times independently, eyes are striking examples of convergent evolution in that 11-cis retinaldehyde is always used for photon capture, yet the mechanism for its regeneration may be dramatically different in between systems. In particular, insects, cephalopods and vertebrates show varying physical separation of the cis-->trans photoisomerization and chromphore reisomerization. In the vertebrate retina, these two processes are actually distributed between different cells. This compartmentalization is made possible by the phylogenetic innovation of the two-layered optic cup of the vertebrate retina. This unprecedented design created the subretinal space as a novel anatomical compartment allowing photoreceptors access to the retinal pigment epithelium (RPE) and Müller cells, the two cell types which share the burden of 11-cis retinoid regeneration. To take advantage of this arrangement, early vertebrates appear to have recruited for retinoid binding, the betabetaalpha-spiral fold proven useful in enoyl-CoA isomerase/hydratases, and the carboxy-terminal proteases for stabilizing hydrophobic ligands. Quadruplication of this functional domain within a single polypeptide lead to the emergence of interphotoreceptor retinoid-binding protein (IRBP). IRBP is the main soluble component of the IPM, and is prevented from diffusing out of the subretinal space because its large size excludes it from the photoreceptor/Müller cell zonulae adheretes. Despite this physical entrapment, IRBP is rapidly turned over within the IPM through a process that coordinates secretion of the protein by the photoreceptors, and its removal from the matrix by RPE and photoreceptor endocytosis. The present review will summarize what is known about the structure and function of IRBP to anticipate future avenues of research.
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Affiliation(s)
- Federico Gonzalez-Fernandez
- Department of Ophthalmology, State University of New York at Buffalo and Medical Research Service, Veteran's Affairs Medical Center, 3495 Bailey Avenue, Buffalo, NY 14215, USA.
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19
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Semenova EM, Converse CA. Comparison between oleic acid and docosahexaenoic acid binding to interphotoreceptor retinoid-binding protein. Vision Res 2003; 43:3063-7. [PMID: 14611942 DOI: 10.1016/j.visres.2003.09.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Interphotoreceptor retinoid-binding protein (IRBP), which binds retinoids and fatty acids, is the major soluble protein in the interphotoreceptor matrix (IPM) but its role remains ambiguous. Using competitive fluorescence and tryptophan-quenching assays we found oleic acid and other cis-monounsaturated fatty acids bind much more strongly than does docosahexaenoic acid to bovine IRBP. IPM's fatty acid composition was determined: it was richer in oleic acid than either the retinal pigment epithelium or rod outer segments. This may imply oleic acid has a key role in the balance and transport of retinoids and fatty acids in the retina.
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Affiliation(s)
- Ekaterina M Semenova
- Department of Pharmaceutical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, Scotland, UK
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20
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Abstract
An important role for docosahexaenoic acid (DHA) within the retina is suggested by its high levels and active conservation in this tissue. Animals raised on n-3-deficient diets have large reductions in retinal DHA levels that are associated with altered retinal function as assessed by the electroretinogram (ERG). Despite two decades of research in this field, little is known about the mechanisms underlying altered retinal function in n-3-deficient animals. The focus of this review is on recent research that has sought to elucidate the role of DHA in retinal function, particularly within the rod photoreceptor outer segments where DHA is found at its highest concentration. An overview is also given of human infant studies that have examined whether a neonatal dietary supply of DHA is required for the normal development of retinal function.
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Affiliation(s)
- B G Jeffrey
- Department of Paediatrics and Child Health, Flinders Medical Centre, The Flinders University of South Australia, Bedford Park, Adelaide, South Australia 5042, Australia
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21
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Loew A, Baer C, Gonzalez-Fernandez F. The functional unit of interphotoreceptor retinoid-binding protein (IRBP)--purification, characterization and preliminary crystallographic analysis. Exp Eye Res 2001; 73:257-64. [PMID: 11446776 DOI: 10.1006/exer.2001.1031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To define the relationship between the structure and function of interphotoreceptor retinoid-binding protein (IRBP) we seek to prepare crystals of IRBP suitable for X-ray crystallographic analysis. As recent studies suggest that each of IRBPs four homologous regions or modules possess ligand-binding activity, we here explore the feasibility of preparing crystals from an individual module. Xenopus laevis IRBP, which has a similar four-module structure as that of mammalian and avian IRBPs, was selected for these studies in view of the advantage of the Xenopus retina for cellular and transgenic approaches. In the present study we focused on the second module of Xenopus IRBP. This module was expressed as a thioredoxin/histidine-patch fusion protein to promote its soluble expression in Escherichia coli and subsequent purification. The ligand-binding properties of the fusion protein were determined by fluorescence spectroscopy. For the preparation of crystals, the module was enzymatically separated from the fusion tag. Crystals of the native and selenomethionine derivatized module were prepared by vapor diffusion in hanging drops. Module II of IRBP binds 1.57 +/- 0.041 and 1.49 +/- 0.15 equivalents of at all- trans retinol and 9-(9-anthroyloxy) stearic acid, respectively, with KDs in the 0.1 microM range. Crystals of this module had an elongated rectangular beam-like morphology. A complete dataset of a frozen selenomethionine crystal extending to 1.85 A resolution was collected. Focusing on the individual modules will likely provide an effective strategy to correlate biochemical and structural data to define the functional domains of IRBP. The quality and resolution of the data obtained suggests that it will be possible in the near future to solve the X-ray crystal structure of the IRBP modules.
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Affiliation(s)
- A Loew
- Department of Biochemistry, University of Texas, Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd, Dallas, TX 75390-9050, USA.
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22
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Affiliation(s)
- H Ripps
- Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine, 1855 West Taylor Street, Chicago, IL 60612, USA.
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23
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McBee JK, Palczewski K, Baehr W, Pepperberg DR. Confronting complexity: the interlink of phototransduction and retinoid metabolism in the vertebrate retina. Prog Retin Eye Res 2001; 20:469-529. [PMID: 11390257 DOI: 10.1016/s1350-9462(01)00002-7] [Citation(s) in RCA: 259] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Absorption of light by rhodopsin or cone pigments in photoreceptors triggers photoisomerization of their universal chromophore, 11-cis-retinal, to all-trans-retinal. This photoreaction is the initial step in phototransduction that ultimately leads to the sensation of vision. Currently, a great deal of effort is directed toward elucidating mechanisms that return photoreceptors to the dark-adapted state, and processes that restore rhodopsin and counterbalance the bleaching of rhodopsin. Most notably, enzymatic isomerization of all-trans-retinal to 11-cis-retinal, called the visual cycle (or more properly the retinoid cycle), is required for regeneration of these visual pigments. Regeneration begins in rods and cones when all-trans-retinal is reduced to all-trans-retinol. The process continues in adjacent retinal pigment epithelial cells (RPE), where a complex set of reactions converts all-trans-retinol to 11-cis-retinal. Although remarkable progress has been made over the past decade in understanding the phototransduction cascade, our understanding of the retinoid cycle remains rudimentary. The aim of this review is to summarize recent developments in our current understanding of the retinoid cycle at the molecular level, and to examine the relevance of these reactions to phototransduction.
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Affiliation(s)
- J K McBee
- Department of Ophthalmology, University of Washington, Seattle, WA 98195, USA
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24
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Abstract
Interphotoreceptor retinoid binding protein (IRBP), the major soluble protein component of the interphotoreceptor matrix, is believed to participate in the visual cycle by transporting retinoids between retinal pigment epithelium and photoreceptor cells in the eye. IRBP can associate with several chemical and isomeric forms of retinoids but displays the highest affinity towards the retinoids that are important in the visual cycle, 11-cis-retinal and all-trans-retinol. It was previously reported that IRBP can associate with 2 mol of all-trans-retinol or 2 mol of 11-cis-retinal per mol of protein. One of the retinoid binding sites, termed 'site 1', was found to display a broad ligand selectivity and to bind either all-trans-retinol or 11-cis-retinal with similar affinities. Here, the retinoid-binding properties of IRBP were further examined. The data demonstrate that IRBP contains three distinct retinoid binding sites. The promiscuous 'site 1', and two additional sites with a stricter selectivity. One of the latter sites appears to be selective towards all-trans-retinol, while the other is specific for 11-cis-retinal.
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Affiliation(s)
- N S Shaw
- Division of Nutritional Sciences, Cornell University, Savage Hall, Ithaca, NY 14853, USA
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25
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Abstract
Phagocytosis of tips of rod outer segments (ROS) by retinal pigment epithelial (RPE) cells is vitally important for maintaining structural and functional integrity of the retina. We previously reported that receptor-mediated specific phagocytosis of ROS induces expression of early response genes coding for transcription factors. Here we study the expression of peroxisome proliferator-activated receptors (PPAR) -alpha, -delta (beta) and -gamma during ROS phagocytosis of rat RPE cells in primary cell culture, using competitive quantitative RT-PCR. During phagocytosis of ROS (but not of latex particles) by RPE cells, RT-PCR revealed a transient increase in PPARgamma mRNA expression, that peaked at 4-6 hr. We sequenced and described two alternatively spliced variants of rat PPARgamma: rPPARgamma1a and rPPARgamma1b. Both of these, along with the recently described rPPARgamma2 were induced by ROS phagocytosis. PPARalpha and PPARdelta mRNA expression was also detected in RPE cells, but the level of expression did not change during ROS phagocytosis. All-trans-retinoic acid and prostaglandin E(2) (PGE(2)) selectively potentiated both basal and ROS-phagocytosis-induced PPARgamma expression. All-trans-retinoic acid had the opposite inhibitory effect on PPARalpha and PPARdelta expression. Cycloheximide had a dual action on PPARgamma expression in RPE cells: it enhanced expression under basal conditions but repressed expression induced by ROS phagocytosis. It also stimulated expression of PPARalpha but had no effect on PPARdelta. Selective activation of PPARgamma may play an important role in regulating the expression of target genes that are involved in lipid and fatty acid metabolism in the photoreceptor renewal process.
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Affiliation(s)
- A V Ershov
- Neuroscience Center of Excellence and Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans. LA, USA
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26
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Abstract
Interphotoreceptor retinoid-binding protein (IRBP) greatly enhances the conversion of all- trans -retinol to 11- cis -retinal by the retinal pigment epithelium (RPE) and facilitates 11- cis -retinal release from the RPE. However, the mechanisms by which IRBP exerts these effects are not clear. Using a model system of purified bovine IRBP and isolated bovine RPE membranes, we investigated the possibility that IRBP may favor the delivery of all- trans -retinol to, or the release of 11- cis -retinal from, RPE membranes. As the interphotoreceptor space contains serum retinol-binding protein (RBP) and serum albumin in addition to IRBP, we similarly examined the exchange of retinoids between RPE membranes and human RBP or bovine serum albumin (BSA). Isolated RPE membranes were loaded with radioactive 11- cis -retinal and incubated with solutions of IRBP, RBP, BSA or with buffer alone. Membranes (pellet) and retinoid-binding protein or buffer (supernatant) were separated by centrifugation and analysed for radioactive 11- cis -retinal. Membranes incubated with buffer alone released only 4-5% of their 11- cis -retinal, while 25 microm IRBP removed 18-35%. More retinal was released as the membrane concentration was reduced. In contrast, RBP and BSA removed little retinal, even though both proteins are capable of binding this retinoid. Similar results were obtained with bovine liver membranes, consistent with the idea that the effects of IRBP do not depend on an RPE surface receptor for IRBP. IRBP was also markedly superior to RBP and BSA in removing all- trans -retinol from RPE membranes. In addition, IRBP efficiently delivered bound all- trans -retinol to membranes; however, in contrast to their differential removal of retinoids, all three binding proteins delivered comparable amounts of retinol to membranes. (This result supports the practice of using BSA as a retinoid carrier in in vitro experimental systems). We conclude that, whereas IRBP shares with other retinoid-binding proteins the ability to deliver retinol to membranes, IRBP is unique in its capacity to remove 11- cis -retinal from membranes. This may be the feature of IRBP that drives the vitamin A cycle to efficiently produce 11- cis -retinal.
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Affiliation(s)
- R B Edwards
- Schepens Eye Research Institute, Boston, MA 02114, USA
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27
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Ershov AV, Bazan NG. Induction of cyclooxygenase-2 gene expression in retinal pigment epithelium cells by photoreceptor rod outer segment phagocytosis and growth factors. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19991015)58:2<254::aid-jnr5>3.0.co;2-u] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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28
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Rodriguez de Turco EB, Parkins N, Ershov AV, Bazan NG. Selective retinal pigment epithelial cell lipid metabolism and remodeling conserves photoreceptor docosahexaenoic acid following phagocytosis. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19990815)57:4<479::aid-jnr7>3.0.co;2-u] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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29
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Zhang Z, Mandal AK, Wang N, Keck CL, Zimonjic DB, Popescu NC, Mukherjee AB. Palmitoyl-protein thioesterase gene expression in the developing mouse brain and retina: implications for early loss of vision in infantile neuronal ceroid lipofuscinosis. Gene 1999; 231:203-11. [PMID: 10231585 DOI: 10.1016/s0378-1119(99)00050-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mutations in the palmitoyl-protein thioesterase (PPT) gene cause infantile neuronal ceroid lipofuscinosis (INCL), the clinical manifestations of which include the early loss of vision followed by deterioration of brain functions. To gain insight into the temporal onset of these clinical manifestations, we isolated and characterized a murine PPT (mPPT)-cDNA, mapped the gene on distal chromosome 4, and studied its expression in the eye and in the brain during development. Our results show that both cDNA and protein sequences of the murine and human PPTs are virtually identical and that the mPPT expression in the retina and in the brain is temporally regulated during development. Furthermore, the retinal expression of mPPT occurs much earlier and at a higher level than in the brain at all developmental stages investigated. Since many retinal and brain proteins are highly palmitoylated and depalmitoylation by PPT is essential for their effective recycling in the lysosomes, our results raise the possibility that inactivating mutations of the PPT gene, as occur in INCL, are likely to cause cellular accumulation of lipid-modified proteins in the retina earlier than in the brain. Consequently, the loss of vision occurs before the deterioration of brain functions in this disease.
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Affiliation(s)
- Z Zhang
- Section on Developmental Genetics, Heritable Disorders Branch, NICHD, NIH, Bethesda, MD 20892-1830, USA
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30
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Abstract
In the retina, the interphotoreceptor retinoid-binding protein shuttles retinoids between the retinal pigment epithelium and the rod outer segment. A molecular mechanism for this transport is proposed.
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Affiliation(s)
- G Wolf
- Department of Nutritional Sciences, University of California, Berkeley 94720-3104, USA
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31
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Baer CA, Retief JD, Van Niel E, Braiman MS, Gonzalez-Fernandez F. Soluble expression in E. coli of a functional interphotoreceptor retinoid-binding protein module fused to thioredoxin: correlation of vitamin A binding regions with conserved domains of C-terminal processing proteases. Exp Eye Res 1998; 66:249-62. [PMID: 9533851 DOI: 10.1006/exer.1997.0418] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The exchange of all-trans retinol and 11-cis retinal between the photoreceptors and retinal pigmented epithelium is mediated by interphotoreceptor retinoid-binding protein (IRBP). IRBP contains binding sites for retinoids, docosahexaenoic acid and probably cell surface and matrix receptors. IRBP arose through the quadruplication of an ancient protein, represented by its carboxy-terminal module (module 4 in amphibians and mammals). Module 4 has retinol binding activity and is composed of regions coded for by each of IRBP's four exons. Determining the function of the exons has been hampered by insoluble expression of module 4 in Escherichia coli. Here, we found that module 4 of Xenopus IRBP (X4IRBP), as well as its exon segments, can be expressed in a soluble form as thioredoxin fusion proteins. The recombinant proteins were purified by ion exchange and arsenical-based affinity chromatography. Liquid chromatography/mass spectrometry confirmed that the sequence of X4IRBP is correct. All-trans retinol binding was characterized by monitoring enhancement of retinol fluorescence, quenching of intrinsic protein fluorescence, and transfer of energy to the bound retinol. Retinol bound to X4IRBP at 2.20+/-0.29 sites with a KD=1.25+/-0.39. One of the two sites was localized to Exons(2+3) and had a KD=0.26+/-0.13 micron. This site, which supported protein quenching and energy transfer, probably contains at least one of the two conserved tryptophans present in this segment. The second site was localized to Exon 4. This site supported the enhancement of retinol fluorescence but not protein quenching or energy transfer and had a KD=1.94+/-0.20 micron. Exon 1 had no retinol binding activity. The location of the retinol binding regions correlated with the distribution of domains conserved between IRBPs and the newly recognized family of C-terminal processing proteases (CtpAs), proteins which bind and cleave non-polar carboxy termini.
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Affiliation(s)
- C A Baer
- Department of Ophthalmology, University of Virginia Health Center, Charlottesville, Virginia 22908, USA
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32
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Liou GI, Matragoon S, Chen DM, Gao CL, Zhang L, Fei Y, Katz ML, Stark WS. Visual sensitivity and interphotoreceptor retinoid binding protein in the mouse: regulation by vitamin A. FASEB J 1998; 12:129-38. [PMID: 9438418 DOI: 10.1096/fasebj.12.1.129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Interphotoreceptor retinoid binding protein (IRBP) is a retinoid and fatty acid binding glycoprotein secreted by rod and cone photoreceptors in all vertebrates. IRBP is believed to serve as a carrier for retinoids in the bleaching and regeneration cycle of rhodopsin. IRBP protein has been found to be decreased in vitamin A-deprived rats; it is rapidly recovered after retinol repletion. To understand the mechanism for this recovery, we determined whether vitamin A affects transcription and translation of the IRBP gene. Wild-type and transgenic mice harboring the IRBP promoter-CAT reporter fusion gene were maintained on a retinol-deficient diet supplemented with retinoic acid (-A) or on a control diet (+A) for up to 60 wk postweaning. Some of the -A mice were given retinol repletion for 7 days (-A+A). Electroretinography analysis revealed alterations in waveform and a 2 log unit decrease in b-wave sensitivity in the -A mice over a broad range of stimulus wavelengths. Retinol repletion effected a full recovery. Immunochemistry showed a significant decrease in the immunogold-labeled IRBP between the retinal pigment epithelium and the outer segments of the -A mice compared with +A and -A+A mice. Northern blots showed no differences in the amounts of IRBP or CAT mRNA between these three treatment groups. These results suggest that the regulation of IRBP by retinol is not transcriptional.
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Affiliation(s)
- G I Liou
- Medical College of Georgia, Department of Opthalmology, Augusta 30912, USA
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33
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Liou GI, Matragoon S, Chen D, Gao C, Zhang L, Fei Y, Katz ML, Stark WS. Visual sensitivity and interphotoreceptor retinoid binding protein in the mouse: regulation by vitamin A. FASEB J 1998. [DOI: 10.1096/fsb2fasebj.12.1.129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Gregory I. Liou
- Medical College of GeorgiaDepartment of OphthalmologyAugusta Georgia 30912 USA
| | - Suraporn Matragoon
- Medical College of GeorgiaDepartment of OphthalmologyAugusta Georgia 30912 USA
| | - De‐Mao Chen
- Saint Louis UniversityDepartment of BiologySt. Louis Missouri 63103 USA
| | - Chun‐Lan Gao
- University of Missouri School of MedicineMason Eye Institute Columbia Missouri 65212 USA
| | - Lu Zhang
- Medical College of GeorgiaDepartment of Cellular Biology and Anatomy Augusta Georgia 30912 USA
| | - Yijian Fei
- Medical College of GeorgiaDepartment of OphthalmologyAugusta Georgia 30912 USA
| | - Martin L. Katz
- University of Missouri School of MedicineMason Eye Institute Columbia Missouri 65212 USA
| | - William S. Stark
- Saint Louis UniversityDepartment of BiologySt. Louis Missouri 63103 USA
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34
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Tschanz CL, Noy N. Binding of retinol in both retinoid-binding sites of interphotoreceptor retinoid-binding protein (IRBP) is stabilized mainly by hydrophobic interactions. J Biol Chem 1997; 272:30201-7. [PMID: 9374503 DOI: 10.1074/jbc.272.48.30201] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is an ocular protein which is believed to participate in the visual cycle by mediating transport of retinoids between pigment epithelium and photoreceptor cells. The molecular mechanism underlying the ability of IRBP to target particular retinoids to the specific cells that are their sites of action and metabolism is not completely clear, and little information is available regarding the structure of the protein's multiple ligand-binding sites. IRBP possesses two retinoid-binding sites, and it was reported that binding of the visual chromophore, 11-cis-retinal, in one of these sites, but not in the other, is tightly regulated by another IRBP ligand, docosahexaenoic acid (Chen, Y., Houghton, L. A., Brenna, J. T., and Noy, N. (1996) J. Biol. Chem. 271, 20507). The two sites are thus functionally distinct. Here, the thermodynamic parameters governing the interactions of retinol with the IRBP retinoid-binding sites were measured. The data demonstrate that the interactions of retinol with both sites are stabilized mainly by hydrophobic interactions, and that the hydroxyl head group of retinol is not involved in formation of protein-ligand complexes. Nevertheless, the data indicate that the two sites are structurally distinct, and that binding of retinol in them occurs by remarkably different modes of interactions.
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Affiliation(s)
- C L Tschanz
- Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, New York 14853, USA.
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35
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Ershov AV, Lukiw WJ, Bazan NG. Selective transcription factor induction in retinal pigment epithelial cells during photoreceptor phagocytosis. J Biol Chem 1996; 271:28458-62. [PMID: 8910472 DOI: 10.1074/jbc.271.45.28458] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Expression of early response genes during rod outer segment phagocytosis by normal Long Evans and Royal College of Surgeons-rdy+p+ rats and by dystrophic Royal College of Surgeons-p+ rat retinal pigment epithelial cells was studied in primary cell culture. Northern analysis revealed that the abundance of zif-268 (egr-1), c-fos, and tis-1 (NGF1-B) mRNA was rapidly and transiently increased in normal retinal pigment epithelial cells during rod outer segment phagocytosis but not during phagocytosis of latex particles. No increase in gene expression was found in Royal College of Surgeons-p+ dystrophic retinal pigment epithelial cells challenged with rod outer segments. As shown by electrophoretic mobility shift assay, a prominent short term increase in the intensity of the gel-shifted band was detected using nuclear protein extracts derived from rod outer segment-challenged, control retinal pigment epithelial cells and zif-268, AP-1, AP-2, or tis-1 consensus oligonucleotides. No such increase was detected when using nuclear factor kappaB consensus oligonucleotide or when the early response gene prostaglandin H synthase-2 mRNA was measured over the time course studied. The results suggest that in retinal pigment epithelial cells, rod outer segment-specific phagocytosis is accompanied by the selective expression of early response genes coding for transcription factors. The specific pattern of the induction of these transcription factors is predicted to modulate the expression of gene cascades.
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Affiliation(s)
- A V Ershov
- Neuroscience Center and Department of Ophthalmology, Louisiana State University Medical Center, New Orleans, Louisiana 70112, USA.
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Chen Y, Houghton LA, Brenna JT, Noy N. Docosahexaenoic acid modulates the interactions of the interphotoreceptor retinoid-binding protein with 11-cis-retinal. J Biol Chem 1996; 271:20507-15. [PMID: 8702792 DOI: 10.1074/jbc.271.34.20507] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Rapid transport of retinoids across the interphotoreceptor matrix is a critical part of the visual cycle, since it serves to replenish bleached rhodopsin with its chromophore 11-cis-retinal. The transport of retinoids in the interphotoreceptor matrix is believed to be mediated by the interphotoreceptor retinoid-binding protein (IRBP), a protein that, in addition to possessing two retinoid-binding sites, associates in vivo with long chain fatty acids. Here, the interrelationships between binding of the two types of ligands to IRBP were studied. The composition of fatty acids associated with IRBP in bovine retina was determined, and it was found that polyunsaturated fatty acids constitute a significant fraction of those. It was further found that docosahexaenoic acid, but not palmitic acid, induced a rapid and specific release of 11-cis-retinal from one of the protein's retinoid-binding sites. Based on these results and on the additional observation that a steep concentration gradient of docosahexaenoic acid exists between photoreceptor and pigment epithelium cells, a model for the mechanism by which IRBP may target 11-cis-retinal to photoreceptor cells is proposed.
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Affiliation(s)
- Y Chen
- Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, New York 14853-6301, USA
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Chen CK, Inglese J, Lefkowitz RJ, Hurley JB. Ca(2+)-dependent interaction of recoverin with rhodopsin kinase. J Biol Chem 1995; 270:18060-6. [PMID: 7629115 DOI: 10.1074/jbc.270.30.18060] [Citation(s) in RCA: 243] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Recoverin (Rv) is a myristoylated Ca(2+)-binding protein present primarily in bovine photoreceptors. It represents a newly identified family of neuronal specific Ca(2+)-binding proteins that includes neurocalcin, hippocalcin, and guanylyl cyclase-activating protein. To investigate the function of Rv in photoreceptors, we identified proteins that bind immobilized Rv in a Ca(2+)-dependent manner. Rhodopsin kinase (RK), interphotoreceptor retinoid-binding protein, and tubulin interact with Rv in the presence of Ca2+. The importance of the Rv/RK interaction was further characterized. RK, purified using immobilized Rv as an affinity matrix, catalyzed the light-dependent and Ca(2+)-independent incorporation of phosphates into rhodopsin when reconstituted with urea-stripped rod outer segment membranes. When only a small fraction (0.04%) of rhodopsin was photolyzed, as many as 700 phosphates were incorporated per photolyzed rhodopsin, a phenomenon known as "high gain" phosphorylation. When recoverin was added, the activity of RK became sensitive to free Ca2+, with EC50 = 3 microM. The N-terminal myristoyl residue of Rv enhances the inhibitory effect of Rv and introduces cooperativity to the Ca(2+)-dependent inhibition of rhodopsin phosphorylation. Rv neither interacts with other members of the G-protein-coupled receptor kinase family such as beta-adrenergic receptor kinase 1 nor inhibits beta-adrenergic receptor kinase 1 activity. The specific and Ca(2+)-dependent Rv/RK interaction is necessary for the inhibitory effect of Rv on rhodopsin phosphorylation and may play an important role in photoreceptor light adaptation.
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Affiliation(s)
- C K Chen
- Department of Biochemistry, University of Washington, Seattle 98195, USA
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Santos FF, de Turco EB, Gordon WC, Peyman GA, Bazan NG. Alterations in rabbit retina lipid metabolism induced by detachment. Decreased incorporation of [3H]DHA into phospholipids. Int Ophthalmol 1995; 19:149-59. [PMID: 8926126 DOI: 10.1007/bf00133731] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Docosahexaenoic acid (22:6n-3, DHA) is found in high concentration in phospholipids from retinal membranes, and is essential for their function. This study investigated the effect of in vivo retinal detachment on in vitro lipid metabolism using [3H]DHA. METHODS Rabbit retina was detached from the retinal pigment epithelium by injecting physiological saline into the subretinal space of the eye. Retinal samples from control (non-operated) and sham (operated, no detachment) animals, and from attached and detached retinal areas from the same eye, were incubated in vitro with [3H]DHA for 4 hours, and then prepared for biochemical and autoradiographic analysis. RESULTS In control and sham retinas, [3H]DHA was preferentially esterified into phospholipids (82%) with low labeling of free fatty acids (FFA) (5%). In samples from detached areas of the retina, a higher proportion of [3H]DHA was recovered in the FFA pool (up to 30%) and its esterification was shunted into triacylglycerol, thereby reducing the formation of [3H]DHA-phospholipids. Changes were sustained through 48 hours of postdetachment. High labeling of inner segments and synaptic terminals was observed autoradiographically in control retinas, while in detached retinas, clusters of labeling were detected in the neural retina, and eventually within the photoreceptor layer. CONCLUSION Retinal detachment induces longlasting changes in lipid metabolism which are reflected in lower labeling of [3H]DHA-phospholipids. Metabolic changes, sustained through 48 hours, may lead to inadequate synthesis/turnover of phospholipids, among them, those containing DHA, possibly resulting in defective disc membrane assembly with subsequent deterioration of visual cells.
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Affiliation(s)
- F F Santos
- LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans 70112-2234, USA
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Bobola N, Hirsch E, Albini A, Altruda F, Noonan D, Ravazzolo R. A single cis-acting element in a short promoter segment of the gene encoding the interphotoreceptor retinoid-binding protein confers tissue-specific expression. J Biol Chem 1995; 270:1289-94. [PMID: 7836393 DOI: 10.1074/jbc.270.3.1289] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is the major protein component of the interphotoreceptor matrix. IRBP has a highly restricted tissue-specific expression in retinal photoreceptor cells and in a subgroup of pinealocytes. With the purpose of understanding how transcriptional regulation contributes to the expression of human IRBP, we have studied a short promoter fragment (from -123 to +18, relative to the transcription start site). We demonstrate, by analysis of the expression of the lacZ reporter gene fused to this short promoter fragment in transgenic mice, that it is sufficient to confer tissue-specific expression in retinal photoreceptors and in pinealocytes. DNA/protein binding assays, performed to identify binding sites for tissue-specific trans-acting factors, have shown that an element between -45 and -58 binds a factor present only in nuclear extracts of retinoblastoma-derived cell lines, which express IRBP. An element further upstream, between -86 and -106, binds apparently ubiquitous factors. Site-directed mutagenesis was performed to disrupt a GATTAA motif included in the -45 to -58 binding site and a second inverted GATTAA motif present shortly upstream. In transgenic mice bearing the mutated version of the promoter fragment, the expression of the reporter gene was completely abolished, thus suggesting that this element is essential for tissue-specific expression. A GATTAA motif appears in the 5'-flanking regions of several photoreceptor-specific genes, suggesting that this could be the recognition site for a photoreceptor-specific factor.
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Affiliation(s)
- N Bobola
- Institute of Biology and Genetics, University of Genova, Italy
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40
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Affiliation(s)
- A J McColl
- Department of Pharmaceutical Sciences, University of Strathclyde, Glasgow, U.K
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41
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Clandinin MT, Jumpsen J, Suh M. Relationship between fatty acid accretion, membrane composition, and biologic functions. J Pediatr 1994; 125:S25-32. [PMID: 7965449 DOI: 10.1016/s0022-3476(06)80733-x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Dietary fat affects metabolic pathways for phospholipid biosynthesis in tissues in a coordinated fashion. This may be important to aspects of development that concern phosphatidylcholine metabolism or regulatory processes that depend on signals from a changing milieu in the microenvironment of the membrane. Dietary fat influences the phosphatidylethanolamine (PE) composition in many membranes of the brain and retina and may by altered by small changes in the content of 20:4(6) and 22:6(3). Membrane PE fatty acids that contain one, four, or six double bonds and the ratio of 22:5(6) to 22:6(3) in PE that contains four to six double bonds are also affected. An increase in the omega 6 fatty acid content of membranes is associated with increased PE methyltransferase activity and decreased phosphocholine transferase activity, thus indicating a mechanism by which change in an exogenous factor (e.g., dietary fat intake) may alter neural phospholipid biosynthesis. Small changes in the composition of dietary fat intake change the composition of brain membranes during development. It is provocative to ponder whether diet could be used to induce formation of membrane structures that are more resistant to specific insults that cause degeneration of brain structural material, to ensure optimal functional compositions, or to reverse degenerative changes that occur in neural membrane structure and function.
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Affiliation(s)
- M T Clandinin
- Department of Food Science and Nutrition, University of Alberta, Edmonton, Canada
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Wiggert B, van Veen T, Kutty G, Lee L, Nickerson J, Si JS, Nilsson SE, Chader GJ, Narfström K. An early decrease in interphotoreceptor retinoid-binding protein gene expression in Abyssinian cats homozygous for hereditary rod-cone degeneration. Cell Tissue Res 1994; 278:291-8. [PMID: 8001085 DOI: 10.1007/bf00414173] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Levels of interphotoreceptor retinoid-binding protein (IRBP) protein and message in retinas of Abyssinian cats homozygous for progressive rod-cone degeneration were determined at early ages, well before the onset of clinical retinal degeneration. IRBP gene expression was assessed by immunochemical quantitation of IRBP protein, and by Northern blotting and slot-blotting of total RNA using a human IRBP cDNA probe. Morphology was assessed by electron microscopy and immunocytochemistry. Levels of both IRBP protein and message in affected Abyssinian cat retinas were significantly reduced below normal as early as 4 weeks of age at the earliest stage of retinal disorientation. Opsin mRNA was more abundant in affected Abyssinian cat retinas than in control retinas. This was at least 1 year before the onset of clinical symptoms. The reduction in IRBP gene expression to levels significantly below normal well before the onset of retinal degeneration in affected Abyssinian cat retinas indicates that this represents a primary defect or at least an early problem that could itself cause adverse effects.
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Affiliation(s)
- B Wiggert
- National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
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Baer CA, Kittredge KL, Klinger AL, Briercheck DM, Braiman MS, Gonzalez-Fernandez F. Expression and characterization of the fourth repeat of Xenopus interphotoreceptor retinoid-binding protein in E. coli. Curr Eye Res 1994; 13:391-400. [PMID: 7924403 DOI: 10.3109/02713689408999866] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is an extracellular glycolipoprotein which in higher vertebrates has a 4-repeat structure and carries endogenous vitamin A and fatty acids. The location of IRBP's 1-2 binding sites for retinol is unknown. To begin to understand which repeat(s) are responsible for ligand-binding, we expressed the fourth repeat of Xenopus IRBP in E. coli to determine if it could by itself bind all-trans retinol. Our expression studies used a polyhistidine fusion domain to purify the recombinant protein directly from inclusion bodies. The fusion protein could be renatured without aggregation if refolded at a sufficiently dilute concentration (< 3 microM). The recombinant fourth repeat of Xenopus IRBP binds [3H]all-trans retinol and the fluorescence of this ligand increases 8-fold upon binding. The binding is saturable with a Kd = 0.4 microM. The expression of recombinant IRBP fragments as fusion proteins in prokaryotes will be useful for defining the structural requirements for ligand binding by this interesting protein.
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Affiliation(s)
- C A Baer
- Department of Ophthalmology, University of Virginia Health Sciences Center, Charlottesville 22908
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44
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Randall W. Cellular expression of a cloned, hydrophilic, murine acetylcholinesterase. Evidence of palmitoylated membrane-bound forms. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32725-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Developmental maturation of hepatic n-3 polyunsaturated fatty acid metabolism: Supply of docosahexaenoic acid to retina and brain. J Nutr Biochem 1994. [DOI: 10.1016/0955-2863(94)90087-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Rodriguez de Turco EB, Gordon WC, Bazan NG. Docosahexaenoic acid is taken up by the inner segment of frog photoreceptors leading to an active synthesis of docosahexaenoyl-inositol lipids: similarities in metabolism in vivo and in vitro. Curr Eye Res 1994; 13:21-8. [PMID: 8156822 DOI: 10.3109/02713689409042394] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Retinal uptake and metabolism of docosahexaenoic acid (DHA) was studied in vivo in frogs 1, 2, and 6 hours after dorsal lymph sac injections of [3H]-DHA (50 microCi/g). Light microscope autoradiography and biochemical techniques were used to compare the profiles of cellular uptake and lipid labeling with those obtained from 6 hour [3H]-DHA retinal incubations (final DHA concentration, 0.11 and 25 microM). Light microscope autoradiography demonstrated that rod photoreceptor ellipsoids and synaptic terminals preferentially labeled both in vivo and in vitro conditions. Also, the cytoplasm and oil droplets of retinal pigment epithelial cells became very heavily labeled after 6 hours of in vivo labeling. Phosphatidic acid showed the highest labeling in one hour, while other phospholipids accumulated label throughout the 6 hours. At that time point, most label was recovered in phosphatidyl-ethanolamine (37%), phosphatidylcholine (27%), and phosphatidylinositol (16%), the latter displaying 1.6-fold higher labeling than phosphatidylserine. The profile of labeled lipids was similar to that obtained in vitro when the concentration of DHA was in the nanomolar range. Our results suggest that de novo lipid synthesis is a major route for esterification of [3H]-DHA into retinal lipids, giving rise to an early and rapid labeling of DHA-phosphatidylinositol, both in vivo and in vitro, when DHA is present at low concentrations. Furthermore, the profile of labeled retinal cells under in vivo conditions closely resembles in vitro DHA labeling.
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Caffé AR, Söderpalm A, van Veen T. Photoreceptor-specific protein expression of mouse retina in organ culture and retardation of rd degeneration in vitro by a combination of basic fibroblast and nerve growth factors. Curr Eye Res 1993; 12:719-26. [PMID: 8222732 DOI: 10.3109/02713689308995767] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Previously we have presented the morphological features of a neonatal mouse retinal explant kept in culture for 3 to 4 weeks. To further evaluate the organotypic parameters of the tissue we have examined the presence of opsin, S-antigen, and interphotoreceptor retinoid-binding protein (IRBP) in the same experimental paradigm, using light microscopic immunocytochemistry. In vitro, opsin and S-antigen staining is found in photoreceptor somata from genetically normal explants and those derived from mice with the rd or the rds mutation. When present, inner and outer segments label more intensely. No IRBP staining has been found in cell bodies of any genotype. However, some labeling is found in the plexiform layers and in the inner segments. The results indicate that photoreceptor proteins are continuously produced in vitro. This further establishes the organotypic nature of the retinal explant in culture. The administration of growth factors to these explants has been investigated. Neither basic fibroblast growth factor nor nerve growth factor alone has affected the explants phenotype. However, the combination of these proteins has significantly retarded rd cell loss in vitro.
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Affiliation(s)
- A R Caffé
- Department of Anatomy, Erasmus University Rotterdam, The Netherlands
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Gonzalez-Fernandez F, Kittredge KL, Rayborn ME, Hollyfield JG, Landers RA, Saha M, Grainger RM. Interphotoreceptor retinoid-binding protein (IRBP), a major 124 kDa glycoprotein in the interphotoreceptor matrix of Xenopus laevis. Characterization, molecular cloning and biosynthesis. J Cell Sci 1993; 105 ( Pt 1):7-21. [PMID: 8360278 DOI: 10.1242/jcs.105.1.7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have demonstrated that the neural retina of Xenopus laevis secretes into the extracellular matrix surrounding the inner and outer segments of its photoreceptors a glycoprotein containing hydrophobic domains conserved in mammalian interphotoreceptor retinoid-binding proteins (IRBPs). The soluble extract of the interphotoreceptor matrix contains a 124 kDa protein that cross-reacts with anti-bovine IRBP immunoglobulins. In vitro [3H]fucose incorporation studies combined with in vivo light and electron microscopic autoradiographic analysis, showed that the IRBP-like glycoprotein is synthesized by the neural retina and secreted into the interphotoreceptor matrix. A 1.2 kb Xenopus IRBP cDNA was isolated by screening a stage 42 (swimming tadpole) lambda Zap II library with a human IRBP cDNA under low-stringency conditions. The cDNA hybridizes with a 4.2 kb mRNA in adult Xenopus neural retina, tadpole heads as well as a less-abundant mRNA of the same size in brain. During development, IRBP and opsin mRNA expression correlates with photoreceptor differentiation. The translated amino acid sequence of the Xenopus IRBP clone has an overall 70% identity with the fourth repeat of the human protein. Sequence alignment with the four repeats of human IRBP showed three highly conserved regions, rich in hydrophobic residues. This focal conservation predicts domains important to the protein's function, which presumably is to facilitate the exchange of 11-cis retinal and all-trans retinol between the pigment epithelium and photoreceptors, and to the transport of fatty acids through the hydrophilic interphotoreceptor matrix.
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Affiliation(s)
- F Gonzalez-Fernandez
- Department of Ophthalmology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
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Pepperberg DR, Okajima TL, Wiggert B, Ripps H, Crouch RK, Chader GJ. Interphotoreceptor retinoid-binding protein (IRBP). Molecular biology and physiological role in the visual cycle of rhodopsin. Mol Neurobiol 1993; 7:61-85. [PMID: 8318167 DOI: 10.1007/bf02780609] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The regeneration of visual pigment in rod photoreceptors of the vertebrate retina requires an exchange of retinoids between the neural retina and the retina pigment epithelium (RPE). It has been hypothesized that interphotoreceptor retinoid-binding protein (IRBP) functions as a two-way carrier of retinoid through the aqueous compartment (interphotoreceptor matrix) that separates the RPE and the photoreceptors. The first part of this review summarizes the cellular and molecular biology of IRBP. Work on the IRBP gene indicates that the protein contains a four-fold repeat structure that may be involved in binding multiple retinoid and fatty acid ligands. These repeats and other aspects of the gene structure indicate that the gene has had an active and complex evolutionary history. IRBP mRNA is detected only in retinal photoreceptors and in the pineal gland; expression is thus restricted to the two photosensitive tissues of vertebrate organisms. In the second part of this review, we consider the results obtained in experiments that have examined the activity of IRBP in the process of visual pigment regeneration. We also consider the results obtained on the bleaching and regeneration of rhodopsin in the acutely detached retina, as well as in experiments testing the ability of IRBP to protect its retinoid ligand from isomerization and oxidation. Taken together, the findings provide evidence that, in vivo, IRBP facilitates both the delivery of all-trans retinol to the RPE and the transfer of 11-cis retinal from the RPE to bleached rod photoreceptors, and thereby directly supports the regeneration of rhodopsin in the visual cycle.
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Affiliation(s)
- D R Pepperberg
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences
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50
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Wang N, Anderson RE. Enrichment of polyunsaturated fatty acids from rat retinal pigment epithelium to rod outer segments. Curr Eye Res 1992; 11:783-91. [PMID: 1424722 DOI: 10.3109/02713689209000751] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Polyunsaturated fatty acids (PUFA), especially docosahexaenoic acid (DHA, 22:6n-3), are enriched in phospholipids of vertebrate rod outer segments (ROS). Retinal ROS can incorporate 22 carbon (C-22) PUFA from the plasma pool where C-20 PUFA are predominant. In this study, we analyzed the fatty acid composition of retinal pigment epithelium (RPE) and ROS from rats fed different fatty acid supplements to determine whether this enrichment is at the photoreceptor-RPE boundary or the RPE-choriocapillaris boundary. Long Evans rats were raised from birth for 13-14 weeks on a diet supplemented with 10% (wt/wt) hydrogenated coconut oil (COC; 0.2% 18:2n-6, no 18:3n-3), safflower oil (SAF; 73.8% 18:2n-6, 0.1% 18:3n-3), or linseed oil (LIN; 16.4% 18:2n-6, 52.2% 18:3n-3). These diets were chosen because they increased plasma levels of 20:3n-9, 20:4n-6, and 20:5n-3, respectively. These three fatty acids served as metabolic markers. Plasma levels of 22:6n-3 were reduced by the COC and SAF diets. The RPE incorporated 20:3n-9, 20:4n-6, and 20:5n-3 from the plasma. However, the levels of 20:3n-9 and 20:5n-3 were very low in ROS and 20:4n-6 was not significantly elevated in the ROS of the SAF diet group. The relative amount of total C-20 PUFA in phospholipids in RPE was similar to that found in plasma and was about 4-16 times (depending on different lipid classes) that in the ROS. In contrast, C-22 PUFA (22:6n-3 and 22:5n-6) showed a step-wise, average 3-5 fold increase in concentration from the plasma to the RPE to the ROS.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- N Wang
- Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030
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