1
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Chen J, Curcio CA, Crosson JN. Shotgun lipidomics of human subretinal fluids under rod-dominant retina reveals cone-dominated lipids. Exp Eye Res 2024; 240:109807. [PMID: 38278468 DOI: 10.1016/j.exer.2024.109807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/08/2024] [Accepted: 01/22/2024] [Indexed: 01/28/2024]
Abstract
Subretinal fluid (SRF) accumulates between photoreceptor outer segments and retinal pigment epithelium during rhegmatogenous retinal detachment. Biomolecular components such as lipids originate from cells surrounding the SRF. Knowledge of the composition of these molecules in SRF potentially provides mechanistic insight into the physiologic transfer of lipids between retinal tissue compartments. Using mass spectrometry and tandem mass spectrometry analysis on an electrospray ionization quadrupole-time-of-flight mass spectrometer, we identified a total of 115 lipid molecular species of 11 subclasses and 9 classes in two samples from two patients with rhegmatogenous retinal detachment. These included 47 glycerophosphocholines, 6 glycerophosphoethanolamines, 1 glycerophosphoinositol, 18 sphingomyelins, 9 cholesteryl esters, free cholesterol, 3 ceramides, 22 triacylglycerols and 8 free fatty acids. Glycerophosphocholines were of the highest intensity. By minimizing the formation of different adduct forms or clustering ions of different adducts, we determined the relative intensity of lipid molecular species within the same subclasses. The profiles were compared with those of retinal cells available in the published literature. The glycerophosphocholine profile of SRF was similar to that of cone outer segments, suggesting that outer segment degradation products are constitutively released into the interphotoreceptor matrix, appearing in SRF during detachment. This hypothesis was supported by the retinal distributions of corresponding lipid synthases' mRNA expression obtained from an online resource based on publicly available single-cell sequencing data. In contrast, based on lipid profiles and relevant gene expression in this study, the sources of free cholesterol and cholesteryl esters in SRF appeared more ambiguous, possibly reflecting that outer retina takes up plasma lipoproteins. Further studies to identify and quantify lipids in SRF will help better understand etiology of diseases relevant to outer retina.
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Affiliation(s)
- Jianzhong Chen
- Center for Biotechnology & Genomic Medicine, Medical College of Georgia, Augusta University, GA, United States; Department of Cellular Biology & Anatomy, Medical College of Georgia, Augusta University, GA, United States; Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States.
| | - Christine A Curcio
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, AL, United States.
| | - Jason N Crosson
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, AL, United States
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2
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Aplin C, Cerione RA. Probing the mechanism by which the retinal G protein transducin activates its biological effector PDE6. J Biol Chem 2024; 300:105608. [PMID: 38159849 PMCID: PMC10838916 DOI: 10.1016/j.jbc.2023.105608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Revised: 11/23/2023] [Accepted: 12/14/2023] [Indexed: 01/03/2024] Open
Abstract
Phototransduction in retinal rods occurs when the G protein-coupled photoreceptor rhodopsin triggers the activation of phosphodiesterase 6 (PDE6) by GTP-bound alpha subunits of the G protein transducin (GαT). Recently, we presented a cryo-EM structure for a complex between two GTP-bound recombinant GαT subunits and native PDE6, that included a bivalent antibody bound to the C-terminal ends of GαT and the inhibitor vardenafil occupying the active sites on the PDEα and PDEβ subunits. We proposed GαT-activated PDE6 by inducing a striking reorientation of the PDEγ subunits away from the catalytic sites. However, questions remained including whether in the absence of the antibody GαT binds to PDE6 in a similar manner as observed when the antibody is present, does GαT activate PDE6 by enabling the substrate cGMP to access the catalytic sites, and how does the lipid membrane enhance PDE6 activation? Here, we demonstrate that 2:1 GαT-PDE6 complexes form with either recombinant or retinal GαT in the absence of the GαT antibody. We show that GαT binding is not necessary for cGMP nor competitive inhibitors to access the active sites; instead, occupancy of the substrate binding sites enables GαT to bind and reposition the PDE6γ subunits to promote catalytic activity. Moreover, we demonstrate by reconstituting GαT-stimulated PDE6 activity in lipid bilayer nanodiscs that the membrane-induced enhancement results from an increase in the apparent binding affinity of GαT for PDE6. These findings provide new insights into how the retinal G protein stimulates rapid catalytic turnover by PDE6 required for dim light vision.
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Affiliation(s)
- Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA; Department of Molecular Medicine, Cornell University, Ithaca, New York, USA.
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3
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Subczynski WK, Pasenkiewicz-Gierula M, Widomska J. Protecting the Eye Lens from Oxidative Stress through Oxygen Regulation. Antioxidants (Basel) 2023; 12:1783. [PMID: 37760086 PMCID: PMC10525422 DOI: 10.3390/antiox12091783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 09/08/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
Molecular oxygen is a primary oxidant that is involved in the formation of active oxygen species and in the oxidation of lipids and proteins. Thus, controlling oxygen partial pressure (concentration) in the human organism, tissues, and organs can be the first step in protecting them against oxidative stress. However, it is not an easy task because oxygen is necessary for ATP synthesis by mitochondria and in many biochemical reactions taking place in all cells in the human body. Moreover, the blood circulatory system delivers oxygen to all parts of the body. The eye lens seems to be the only organ that is protected from the oxidative stress through the regulation of oxygen partial pressure. The basic mechanism that developed during evolution to protect the eye lens against oxidative damage is based on the maintenance of a very low concentration of oxygen within the lens. This antioxidant mechanism is supported by the resistance of both the lipid components of the lens membrane and cytosolic proteins to oxidation. Any disturbance, continuous or acute, in the working of this mechanism increases the oxygen concentration, in effect causing cataract development. Here, we describe the biophysical basis of the mechanism and its correlation with lens transparency.
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Affiliation(s)
| | - Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, Jagiellonian University, 30-387 Krakow, Poland;
| | - Justyna Widomska
- Department of Biophysics, Medical University of Lublin, 20-090 Lublin, Poland
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4
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Farnoodian M, Bose D, Barone F, Nelson LM, Boyle M, Jun B, Do K, Gordon W, Guerin MAK, Perera R, Ji JX, Cogliati T, Sharma R, Brooks BP, Bazan NG, Bharti K. Retina and RPE lipid profile changes linked with ABCA4 associated Stargardt's maculopathy. Pharmacol Ther 2023; 249:108482. [PMID: 37385300 PMCID: PMC10530239 DOI: 10.1016/j.pharmthera.2023.108482] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/20/2023] [Accepted: 06/26/2023] [Indexed: 07/01/2023]
Abstract
Stargardt maculopathy, caused predominantly by mutations in the ABCA4 gene, is characterized by an accumulation of non-degradable visual pigment derivative, lipofuscin, in the retinal pigment epithelium (RPE) - resulting in RPE atrophy. RPE is a monolayer tissue located adjacent to retinal photoreceptors and regulates their health and functioning; RPE atrophy triggers photoreceptor cell death and vision loss in Stargardt patients. Previously, ABCA4 mutations in photoreceptors were thought to be the major contributor to lipid homeostasis defects in the eye. Recently, we demonstrated that ABCA4 loss of function in the RPE leads to cell-autonomous lipid homeostasis defects. Our work underscores that an incomplete understanding of lipid metabolism and lipid-mediated signaling in the retina and RPE are potential causes for lacking treatments for this disease. Here we report altered lipidomic in mouse and human Stargardt models. This work provides the basis for therapeutics that aim to restore lipid homeostasis in the retina and the RPE.
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Affiliation(s)
- Mitra Farnoodian
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Devika Bose
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Francesca Barone
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Luke Mathew Nelson
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Marisa Boyle
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Khanh Do
- Faculty of Medicine, Phenikaa University, Hanoi, Viet Nam
| | - William Gordon
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Marie-Audrey Kautzmann Guerin
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Rasangi Perera
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Jeff X Ji
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Tiziana Cogliati
- Division of Aging Biology, National Institute on Aging, National Institute of Health, Bethesda, MD, USA
| | - Ruchi Sharma
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Brian P Brooks
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, USA
| | - Kapil Bharti
- Ocular and Stem Cell Translational Research Section, National Eye Institute, National Institute of Health, Bethesda, MD, USA.
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5
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Radzin S, Wiśniewska-Becker A, Markiewicz M, Bętkowski S, Furso J, Waresiak J, Grolik J, Sarna T, Pawlak AM. Structural Impact of Selected Retinoids on Model Photoreceptor Membranes. MEMBRANES 2023; 13:575. [PMID: 37367779 DOI: 10.3390/membranes13060575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 05/07/2023] [Accepted: 05/27/2023] [Indexed: 06/28/2023]
Abstract
Photoreceptor membranes have a unique lipid composition. They contain a high level of polyunsaturated fatty acids including the most unsaturated fatty acid in nature, docosahexaenoic acid (22:6), and are enriched in phosphatidylethanolamines. The phospholipid composition and cholesterol content of the subcellular components of photoreceptor outer segments enables to divide photoreceptor membranes into three types: plasma membranes, young disc membranes, and old disc membranes. A high degree of lipid unsaturation, extended exposure to intensive irradiation, and high respiratory demands make these membranes sensitive to oxidative stress and lipid peroxidation. Moreover, all-trans retinal (AtRAL), which is a photoreactive product of visual pigment bleaching, accumulates transiently inside these membranes, where its concentration may reach a phototoxic level. An elevated concentration of AtRAL leads to accelerated formation and accumulation of bisretinoid condensation products such as A2E or AtRAL dimers. However, a possible structural impact of these retinoids on the photoreceptor-membrane properties has not yet been studied. In this work we focused just on this aspect. The changes induced by retinoids, although noticeable, seem not to be significant enough to be physiologically relevant. This is, however, an positive conclusion because it can be assumed that accumulation of AtRAL in photoreceptor membranes will not affect the transduction of visual signals and will not disturb the interaction of proteins engaged in this process.
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Affiliation(s)
- Szymon Radzin
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Anna Wiśniewska-Becker
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Michał Markiewicz
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics, Jagiellonian University, 30-387 Krakow, Poland
| | - Sebastian Bętkowski
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics, Jagiellonian University, 30-387 Krakow, Poland
| | - Justyna Furso
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Joanna Waresiak
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Jarosław Grolik
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland
| | - Tadeusz Sarna
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Anna M Pawlak
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
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6
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Agbaga MP, McClellan ME, Elliott MH. Analysis of Lipids, Fatty Acid, and Cholesterol in Membrane Microdomains. Methods Mol Biol 2023; 2625:129-139. [PMID: 36653639 DOI: 10.1007/978-1-0716-2966-6_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The original concept that lipid and protein components are randomly distributed in cellular membranes has been challenged by evidence of compartmentalization of such components into discrete membrane microdomains (known as lipid rafts). The lipid microdomain hypothesis has generated significant controversy and rigorous inquiry to test the idea that such domains concentrate machinery to mediate cellular processes such as signaling, synaptic plasticity, and endocytosis. As such, a large number of studies have used biochemical, cell biological, and biophysical methodologies to define the composition of membrane microdomains in experimental contexts. Although biochemical preparation strategies are not without limitations (as discussed herein), the isolation of detergent-resistant and detergent-free membrane domains can provide important information about the segregation of lipids and proteins in membranes. In this chapter, we describe methodologies to isolate membranes from cell or tissue sources with biophysical/biochemical properties of membrane microdomains and also provide methods for subsequent classical or mass spectrometry-based lipid analytical approaches.
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Affiliation(s)
- Martin-Paul Agbaga
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Mark E McClellan
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael H Elliott
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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7
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Loss of the Bardet-Biedl protein Bbs1 alters photoreceptor outer segment protein and lipid composition. Nat Commun 2022; 13:1282. [PMID: 35277505 PMCID: PMC8917222 DOI: 10.1038/s41467-022-28982-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 02/23/2022] [Indexed: 12/22/2022] Open
Abstract
Primary cilia are key sensory organelles whose dysfunction leads to ciliopathy disorders such as Bardet-Biedl syndrome (BBS). Retinal degeneration is common in ciliopathies, since the outer segments (OSs) of photoreceptors are highly specialized primary cilia. BBS1, encoded by the most commonly mutated BBS-associated gene, is part of the BBSome protein complex. Using a bbs1 zebrafish mutant, we show that retinal development and photoreceptor differentiation are unaffected by Bbs1-loss, supported by an initially unaffected transcriptome. Quantitative proteomics and lipidomics on samples enriched for isolated OSs show that Bbs1 is required for BBSome-complex stability and that Bbs1-loss leads to accumulation of membrane-associated proteins in OSs, with enrichment in proteins involved in lipid homeostasis. Disruption of the tightly regulated OS lipid composition with increased OS cholesterol content are paralleled by early functional visual deficits, which precede progressive OS morphological anomalies. Our findings identify a role for Bbs1/BBSome in OS lipid homeostasis, suggesting a pathomechanism underlying retinal degeneration in BBS. Primary cilia are key sensory organelles whose dysfunction leads to ciliopathy disorders such as Bardet-Biedl syndrome (BBS). Here they identify a role for Bbs1 in lipid homeostasis of photoreceptor outer segments in zebrafish, which may contribute to vision loss in patients with Bardet-Biedl syndrome.
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8
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Millette MA, Roy S, Salesse C. Farnesylation and lipid unsaturation are critical for the membrane binding of the C-terminal segment of G-Protein Receptor Kinase 1. Colloids Surf B Biointerfaces 2022; 211:112315. [PMID: 35026543 DOI: 10.1016/j.colsurfb.2021.112315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/15/2021] [Accepted: 12/30/2021] [Indexed: 10/19/2022]
Abstract
Many proteins are modified by the covalent addition of different types of lipids, such as myristoylation, palmitoylation and prenylation. Lipidation is expected to promote membrane association of proteins. Visual phototransduction involves many lipid-modified proteins. The G-Protein-coupled receptor of rod photoreceptors, rhodopsin, is inactivated by G-Protein-coupled Receptor Kinase 1 (GRK1). The C-terminus of GRK1 is farnesylated and its truncation has been shown to result in a very high decrease of its enzymatic activity, most likely because of the loss of its membrane localization. Little information is available on the membrane binding of GRK1 as well as of most prenylated proteins. Measurements of the membrane binding of the non-farnesylated and farnesylated C-terminal segment of GRK1 were thus performed using lipids typical of those found in rod outer segment disk membranes. Their random coil secondary structure was determined using circular dichroism and infrared spectroscopy. The non-farnesylated C-terminal segment of GRK1 has no surface activity. In contrast, the farnesylated C-terminal segment of GRK1 shows a particularly strong binding to lipid monolayers bearing at least one unsaturated fatty acyl chain. No binding is observed in the presence of monolayers of saturated phospholipids, in agreement with the low affinity of farnesylated Ras proteins for lipids in the liquid-ordered state. Altogether, these data demonstrate that the farnesyl group of the C-terminal segment of GRK1 is mandatory for its membrane binding, which is favored by particular lipids or lipid mixtures. This information will also be useful for the understanding of the membrane binding of other prenylated proteins.
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Affiliation(s)
- Marc-Antoine Millette
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sarah Roy
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
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9
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Sander CL, Sears AE, Pinto AF, Choi EH, Kahremany S, Gao F, Salom D, Jin H, Pardon E, Suh S, Dong Z, Steyaert J, Saghatelian A, Skowronska-Krawczyk D, Kiser PD, Palczewski K. Nano-scale resolution of native retinal rod disk membranes reveals differences in lipid composition. J Cell Biol 2021; 220:e202101063. [PMID: 34132745 PMCID: PMC8240855 DOI: 10.1083/jcb.202101063] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/26/2021] [Accepted: 05/18/2021] [Indexed: 02/07/2023] Open
Abstract
Photoreceptors rely on distinct membrane compartments to support their specialized function. Unlike protein localization, identification of critical differences in membrane content has not yet been expanded to lipids, due to the difficulty of isolating domain-specific samples. We have overcome this by using SMA to coimmunopurify membrane proteins and their native lipids from two regions of photoreceptor ROS disks. Each sample's copurified lipids were subjected to untargeted lipidomic and fatty acid analysis. Extensive differences between center (rhodopsin) and rim (ABCA4 and PRPH2/ROM1) samples included a lower PC to PE ratio and increased LC- and VLC-PUFAs in the center relative to the rim region, which was enriched in shorter, saturated FAs. The comparatively few differences between the two rim samples likely reflect specific protein-lipid interactions. High-resolution profiling of the ROS disk lipid composition gives new insights into how intricate membrane structure and protein activity are balanced within the ROS, and provides a model for future studies of other complex cellular structures.
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Affiliation(s)
- Christopher L. Sander
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Avery E. Sears
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Antonio F.M. Pinto
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA
| | - Elliot H. Choi
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Shirin Kahremany
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Fangyuan Gao
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - David Salom
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Hui Jin
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
| | - Els Pardon
- Vlaams Instituut voor Biotechnologie–Vrije Universiteit Brussel Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Susie Suh
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Zhiqian Dong
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Jan Steyaert
- Vlaams Instituut voor Biotechnologie–Vrije Universiteit Brussel Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Alan Saghatelian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA
| | - Dorota Skowronska-Krawczyk
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
| | - Philip D. Kiser
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
- Research Service, VA Long Beach Healthcare System, Long Beach, CA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
- Department of Chemistry, University of California, Irvine, Irvine, CA
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10
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Factors Differentiating the Antioxidant Activity of Macular Xanthophylls in the Human Eye Retina. Antioxidants (Basel) 2021; 10:antiox10040601. [PMID: 33919673 PMCID: PMC8070478 DOI: 10.3390/antiox10040601] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 04/01/2021] [Accepted: 04/07/2021] [Indexed: 02/06/2023] Open
Abstract
Macular xanthophylls, which are absorbed from the human diet, accumulate in high concentrations in the human retina, where they efficiently protect against oxidative stress that may lead to retinal damage. In addition, macular xanthophylls are uniquely spatially distributed in the retina. The zeaxanthin concentration (including the lutein metabolite meso-zeaxanthin) is ~9-fold greater than lutein concentration in the central fovea. These numbers do not correlate at all with the dietary intake of xanthophylls, for which there is a dietary zeaxanthin-to-lutein molar ratio of 1:12 to 1:5. The unique spatial distributions of macular xanthophylls—lutein, zeaxanthin, and meso-zeaxanthin—in the retina, which developed during evolution, maximize the protection of the retina provided by these xanthophylls. We will correlate the differences in the spatial distributions of macular xanthophylls with their different antioxidant activities in the retina. Can the major protective function of macular xanthophylls in the retina, namely antioxidant actions, explain their evolutionarily determined, unique spatial distributions? In this review, we will address this question.
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11
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Park PSH. Supramolecular organization of rhodopsin in rod photoreceptor cell membranes. Pflugers Arch 2021; 473:1361-1376. [PMID: 33591421 DOI: 10.1007/s00424-021-02522-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/12/2021] [Accepted: 01/18/2021] [Indexed: 11/30/2022]
Abstract
Rhodopsin is the light receptor in rod photoreceptor cells that initiates scotopic vision. Studies on the light receptor span well over a century, yet questions about the organization of rhodopsin within the photoreceptor cell membrane still persist and a consensus view on the topic is still elusive. Rhodopsin has been intensely studied for quite some time, and there is a wealth of information to draw from to formulate an organizational picture of the receptor in native membranes. Early experimental evidence in apparent support for a monomeric arrangement of rhodopsin in rod photoreceptor cell membranes is contrasted and reconciled with more recent visual evidence in support of a supramolecular organization of rhodopsin. What is known so far about the determinants of forming a supramolecular structure and possible functional roles for such an organization are also discussed. Many details are still missing on the structural and functional properties of the supramolecular organization of rhodopsin in rod photoreceptor cell membranes. The emerging picture presented here can serve as a springboard towards a more in-depth understanding of the topic.
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Affiliation(s)
- Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
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12
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Kwon W, Freeman SA. Phagocytosis by the Retinal Pigment Epithelium: Recognition, Resolution, Recycling. Front Immunol 2020; 11:604205. [PMID: 33281830 PMCID: PMC7691529 DOI: 10.3389/fimmu.2020.604205] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Tissue-resident phagocytes are responsible for the routine binding, engulfment, and resolution of their meals. Such populations of cells express appropriate surface receptors that are tailored to recognize the phagocytic targets of their niche and initiate the actin polymerization that drives internalization. Tissue-resident phagocytes also harbor enzymes and transporters along the endocytic pathway that orchestrate the resolution of ingested macromolecules from the phagolysosome. Solutes fluxed from the endocytic pathway and into the cytosol can then be reutilized by the phagocyte or exported for their use by neighboring cells. Such a fundamental metabolic coupling between resident phagocytes and the tissue in which they reside is well-emphasized in the case of retinal pigment epithelial (RPE) cells; specialized phagocytes that are responsible for the turnover of photoreceptor outer segments (POS). Photoreceptors are prone to photo-oxidative damage and their long-term health depends enormously on the disposal of aged portions of the outer segment. The phagocytosis of the POS by the RPE is the sole means of this turnover and clearance. RPE are themselves mitotically quiescent and therefore must resolve the ingested material to prevent their toxic accumulation in the lysosome that otherwise leads to retinal disorders. Here we describe the sequence of events underlying the healthy turnover of photoreceptors by the RPE with an emphasis on the signaling that ensures the phagocytosis of the distal POS and on the transport of solutes from the phagosome that supersedes its resolution. While other systems may utilize different receptors and transporters, the biophysical and metabolic manifestations of such events are expected to apply to all tissue-resident phagocytes that perform regular phagocytic programs.
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Affiliation(s)
- Whijin Kwon
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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13
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The Elovl4 Spinocerebellar Ataxia-34 Mutation 736T>G (p.W246G) Impairs Retinal Function in the Absence of Photoreceptor Degeneration. Mol Neurobiol 2020; 57:4735-4753. [PMID: 32780351 PMCID: PMC7515967 DOI: 10.1007/s12035-020-02052-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 07/30/2020] [Indexed: 02/08/2023]
Abstract
Elongation of very long chain fatty acids-4 (ELOVL4) is essential for synthesis of very long chain polyunsaturated and saturated fatty acids (VLC-PUFA and VLC-SFA, respectively) of chain length greater than 26 carbons. Mutations in the ELOVL4 gene cause several distinct neurodegenerative diseases including Stargardt-like macular dystrophy (STGD3), spinocerebellar ataxia 34 (SCA34), and a neuro-ichthyotic syndrome with severe seizures and spasticity, as well as erythrokeratitis variabilis (EKV), a skin disorder. However, the relationship between ELOVL4 mutations, its VLC-PUFA and VLC-SFA products, and specific neurological symptoms remains unclear. We generated a knock-in rat line (SCA34-KI) that expresses the 736T>G (p.W246G) form of ELOVL4 that causes human SCA34. Lipids were analyzed by gas chromatography and mass spectrometry. Retinal function was assessed using electroretinography. Retinal integrity was assessed by histology, optical coherence tomography, and immunolabeling. Analysis of retina and skin lipids showed that the W246G mutation selectively impaired synthesis of VLC-SFA, but not VLC-PUFA. Homozygous SCA34-KI rats showed reduced ERG a- and b-wave amplitudes by 90 days of age, particularly for scotopic responses. Anatomical analyses revealed no indication of neurodegeneration in heterozygote or homozygote SCA34-KI rats out to 6-7 months of age. These studies reveal a previously unrecognized role for VLC-SFA in regulating retinal function, particularly transmission from photoreceptors to the inner retina, in the absence of neurodegeneration. Furthermore, these findings suggest that the tissue specificity and symptoms associated with disease-causing ELOVL4 mutations likely arise from selective differences in the ability of the mutant ELOVL4 enzymes to support synthesis of VLC-PUFA and/or VLC-SFA.
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14
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Perdomo D, Bubis J. Light or tyrosine phosphorylation recruits retinal rod outer segment proteins to lipid rafts. Biochimie 2020; 177:1-12. [PMID: 32758687 DOI: 10.1016/j.biochi.2020.07.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/22/2020] [Accepted: 07/26/2020] [Indexed: 02/06/2023]
Abstract
Lipid rafts are localized liquid-ordered regions of the plasma membrane that contain high levels of cholesterol and glycosphingolipids, and are resistant to extraction with nonionic detergents. Retinal photoreceptor cells contain detergent-resistant membrane microdomains (DRM), which were isolated here from bovine rod outer segments (ROS) under dark and light conditions. Rhodopsin (R) was present in both DRM and detergent soluble fractions (DSF), and detergent-insoluble ROS rafts were enriched in caveolin 1 (Cav-1) and c-Src. In the dark, arrestin and its 44-kDa truncated form (p44) were present mainly in DSF; however, p44 was translocated to DRM under illumination. Similarly, transducin (T) was mainly present in DSF in the dark, but it was recruited toward the DRM fraction following photolysis. DRM were also prepared in the absence or presence of Mg-ATP, guanosine 5'-3-O-(thio)triphosphate (GTPγS), or both. Although GTPγS released T into DSF in the light, GTPγS-activated T was retained in DRM when Mg2+ and ATP were added. Moreover, T was always tyrosine-phosphorylated under light conditions, which suggested that T phosphorylation prevents its GTPγS-induced release from DRM. In addition, treatment with the tyrosine kinase inhibitor genistein prevented the segregation of T to the rafts. In contrast, no localization difference was seen in the presence of Mg-ATP for Cav-1, c-Src, R and both forms of arrestin. Interestingly, immunoprecipitation assays followed by Western blot analyses under light conditions showed the formation of multimeric complexes containing R, T, c-Src, p44 and Cav-1 in DRM, where T and c-Src were tyrosine-phosphorylated.
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Affiliation(s)
- Deisy Perdomo
- Departamento de Biología Celular, Universidad Simón Bolívar, Valle de Sartenejas, Baruta, Caracas, Venezuela.
| | - José Bubis
- Departamento de Biología Celular, Universidad Simón Bolívar, Valle de Sartenejas, Baruta, Caracas, Venezuela.
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15
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Hayashi F, Saito N, Tanimoto Y, Okada K, Morigaki K, Seno K, Maekawa S. Raftophilic rhodopsin-clusters offer stochastic platforms for G protein signalling in retinal discs. Commun Biol 2019; 2:209. [PMID: 31240247 PMCID: PMC6570657 DOI: 10.1038/s42003-019-0459-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 05/10/2019] [Indexed: 12/18/2022] Open
Abstract
Rhodopsin is a G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disc membrane. Recent studies have suggested that rhodopsin forms highly ordered rows of dimers responsible for single-photon detection by rod photoreceptors. Dimerization is also known to confer to rhodopsin a high affinity for ordered lipids (raftophilicity). However, the role of rhodopsin organization and its raftophilicity in phototransduction remains obscure, owing to the lack of direct observation of rhodopsin dynamics and distribution in native discs. Here, we explore the single-molecule and semi-multimolecule behaviour of rhodopsin in native discs. Rhodopsin forms transient meso-scale clusters, even in darkness, which are loosely confined to the disc centre. Cognate G protein transducin co-distributes with rhodopsin, and exhibits lateral translocation to the disc periphery upon activation. We demonstrate that rhodopsin offers inherently distributed and stochastic platforms for G protein signalling by self-organizing raftophilic clusters, which continually repeat generation/extinction in the disc membrane.
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Affiliation(s)
- Fumio Hayashi
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Natsumi Saito
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Yasushi Tanimoto
- Research Centre for Environmental Genomics, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Keisuke Okada
- Graduate School of Agriculture, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Kenichi Morigaki
- Research Centre for Environmental Genomics, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
- Graduate School of Agriculture, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Keiji Seno
- Faculty of Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192 Japan
- International Mass Imaging Centre, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192 Japan
| | - Shohei Maekawa
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
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16
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Simón MV, Prado Spalm FH, Vera MS, Rotstein NP. Sphingolipids as Emerging Mediators in Retina Degeneration. Front Cell Neurosci 2019; 13:246. [PMID: 31244608 PMCID: PMC6581011 DOI: 10.3389/fncel.2019.00246] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 05/17/2019] [Indexed: 12/12/2022] Open
Abstract
The sphingolipids ceramide (Cer), sphingosine-1-phosphate (S1P), sphingosine (Sph), and ceramide-1-phosphate (C1P) are key signaling molecules that regulate major cellular functions. Their roles in the retina have gained increasing attention during the last decade since they emerge as mediators of proliferation, survival, migration, neovascularization, inflammation and death in retina cells. As exacerbation of these processes is central to retina degenerative diseases, they appear as crucial players in their progression. This review analyzes the functions of these sphingolipids in retina cell types and their possible pathological roles. Cer appears as a key arbitrator in diverse retinal pathologies; it promotes inflammation in endothelial and retina pigment epithelium (RPE) cells and its increase is a common feature in photoreceptor death in vitro and in animal models of retina degeneration; noteworthy, inhibiting Cer synthesis preserves photoreceptor viability and functionality. In turn, S1P acts as a double edge sword in the retina. It is essential for retina development, promoting the survival of photoreceptors and ganglion cells and regulating proliferation and differentiation of photoreceptor progenitors. However, S1P has also deleterious effects, stimulating migration of Müller glial cells, angiogenesis and fibrosis, contributing to the inflammatory scenario of proliferative retinopathies and age related macular degeneration (AMD). C1P, as S1P, promotes photoreceptor survival and differentiation. Collectively, the expanding role for these sphingolipids in the regulation of critical processes in retina cell types and in their dysregulation in retina degenerations makes them attractive targets for treating these diseases.
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Affiliation(s)
- M Victoria Simón
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Departamento De Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Argentine National Research Council (CONICET), Bahía Blanca, Argentina
| | - Facundo H Prado Spalm
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Departamento De Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Argentine National Research Council (CONICET), Bahía Blanca, Argentina
| | - Marcela S Vera
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Departamento De Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Argentine National Research Council (CONICET), Bahía Blanca, Argentina
| | - Nora P Rotstein
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Departamento De Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Argentine National Research Council (CONICET), Bahía Blanca, Argentina
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17
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Storti F, Klee K, Todorova V, Steiner R, Othman A, van der Velde-Visser S, Samardzija M, Meneau I, Barben M, Karademir D, Pauzuolyte V, Boye SL, Blaser F, Ullmer C, Dunaief JL, Hornemann T, Rohrer L, den Hollander A, von Eckardstein A, Fingerle J, Maugeais C, Grimm C. Impaired ABCA1/ABCG1-mediated lipid efflux in the mouse retinal pigment epithelium (RPE) leads to retinal degeneration. eLife 2019; 8:45100. [PMID: 30864945 PMCID: PMC6435327 DOI: 10.7554/elife.45100] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/12/2019] [Indexed: 01/04/2023] Open
Abstract
Age-related macular degeneration (AMD) is a progressive disease of the retinal pigment epithelium (RPE) and the retina leading to loss of central vision. Polymorphisms in genes involved in lipid metabolism, including the ATP-binding cassette transporter A1 (ABCA1), have been associated with AMD risk. However, the significance of retinal lipid handling for AMD pathogenesis remains elusive. Here, we study the contribution of lipid efflux in the RPE by generating a mouse model lacking ABCA1 and its partner ABCG1 specifically in this layer. Mutant mice show lipid accumulation in the RPE, reduced RPE and retinal function, retinal inflammation and RPE/photoreceptor degeneration. Data from human cell lines indicate that the ABCA1 AMD risk-conferring allele decreases ABCA1 expression, identifying the potential molecular cause that underlies the genetic risk for AMD. Our results highlight the essential homeostatic role for lipid efflux in the RPE and suggest a pathogenic contribution of reduced ABCA1 function to AMD.
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Affiliation(s)
- Federica Storti
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland
| | - Katrin Klee
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland.,Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Vyara Todorova
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland.,Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland
| | - Regula Steiner
- Institute of Clinical Chemistry, University of Zurich, Schlieren, Switzerland
| | - Alaa Othman
- Institute of Clinical Chemistry, University of Zurich, Schlieren, Switzerland
| | | | - Marijana Samardzija
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland
| | - Isabelle Meneau
- Department of Ophthalmology, University Hospital Zurich, Zurich, Switzerland
| | - Maya Barben
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland
| | - Duygu Karademir
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland.,Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Valda Pauzuolyte
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland
| | - Sanford L Boye
- Department of Ophthalmology, University of Florida, Gainesville, United States
| | - Frank Blaser
- Department of Ophthalmology, University Hospital Zurich, Zurich, Switzerland
| | - Christoph Ullmer
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F Hoffmann-La Roche Ltd., Basel, Switzerland
| | - Joshua L Dunaief
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, United States
| | - Thorsten Hornemann
- Institute of Clinical Chemistry, University of Zurich, Schlieren, Switzerland
| | - Lucia Rohrer
- Institute of Clinical Chemistry, University of Zurich, Schlieren, Switzerland
| | - Anneke den Hollander
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, Netherlands
| | | | - Jürgen Fingerle
- Natural and Medical Sciences Institute, University of Tübingen, Tübingen, Germany
| | - Cyrille Maugeais
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F Hoffmann-La Roche Ltd., Basel, Switzerland
| | - Christian Grimm
- Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Schlieren, Switzerland.,Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland
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18
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Prokopiou E, Kolovos P, Kalogerou M, Neokleous A, Nicolaou O, Sokratous K, Kyriacou K, Georgiou T. Omega-3 Fatty Acids Supplementation: Therapeutic Potential in a Mouse Model of Stargardt Disease. Invest Ophthalmol Vis Sci 2019; 59:2757-2767. [PMID: 29860462 DOI: 10.1167/iovs.17-23523] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To evaluate the therapeutic effects of omega-3 (ω3) fatty acids on retinal degeneration in the ABCA4-/- model of Stargardt disease when the blood level of arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio is between 1 and 1.5. Methods Eight-month-old mice were allocated to three groups: wild type (129S1), ABCA4-/- untreated, and ABCA4-/- ω3 treated. ω3 treatment lasted 3 months and comprised daily gavage administration of EPA and docosahexaenoic acid (DHA). Blood and retinal fatty acid analysis was performed using gas chromatography to adjust the blood AA/EPA ∼1 to 1.5. Eyecups were histologically examined using transmission electron microscopy and confocal microscopy to evaluate lipofuscin granules and the photoreceptor layer. Retinal N-retinylidene-N-retinylethanolamine (A2E), a major component of retinal pigment epithelium lipofuscin, was quantified using liquid chromatography and tandem mass spectrometry, in addition to retinal proteomic analysis to determine changes in inflammatory proteins. Results EPA levels increased and AA levels decreased in the blood and retinas of the treatment group. Significantly less A2E and lipofuscin granules were observed in the treatment group. The thickness of the outer nuclear layer was significantly greater in the treatment group (75.66 ± 4.80 μm) than in the wild-type (61.40 ± 1.84 μm) or untreated ABCA4-/- (56.50 ± 3.24 μm) groups. Proteomic analysis indicated lower levels of complement component 3 (C3) in the treatment group, indicative of lower complement-induced inflammatory response. Conclusions Three months of ω3 supplementation (AA/EPA ∼1-1.5) reduces A2E levels, lipofuscin granules, and C3 levels in the ABCA4-/- mouse model of Stargardt disease, consistent with slowing of the disease.
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Affiliation(s)
| | | | - Maria Kalogerou
- Ophthalmos Research and Educational Institute, Nicosia, Cyprus
| | | | - Orthodoxia Nicolaou
- Department of Electron Microscopy and Molecular Pathology, The Cyprus Institute of Neurology and Genetics, The Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kleitos Sokratous
- Department of Electron Microscopy and Molecular Pathology, The Cyprus Institute of Neurology and Genetics, The Cyprus School of Molecular Medicine, Nicosia, Cyprus.,Bioinformatics Group, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Kyriacos Kyriacou
- Department of Electron Microscopy and Molecular Pathology, The Cyprus Institute of Neurology and Genetics, The Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Tassos Georgiou
- Ophthalmos Research and Educational Institute, Nicosia, Cyprus
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19
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Hopiavuori BR, Anderson RE, Agbaga MP. ELOVL4: Very long-chain fatty acids serve an eclectic role in mammalian health and function. Prog Retin Eye Res 2018; 69:137-158. [PMID: 30982505 PMCID: PMC6688602 DOI: 10.1016/j.preteyeres.2018.10.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 10/17/2018] [Accepted: 10/22/2018] [Indexed: 11/30/2022]
Abstract
ELOngation of Very Long chain fatty acids-4 (ELOVL4) is an elongase responsible for the biosynthesis of very long chain (VLC, ≥C28) saturated (VLC-SFA) and polyunsaturated (VLC-PUFA) fatty acids in brain, retina, skin, Meibomian glands, and testes. Fascinatingly, different mutations in this gene have been reported to cause vastly different phenotypes in humans. Heterozygous inheritance of seven different mutations in the coding sequence and 5' untranslated region of ELOVL4 causes autosomal dominant Stargardt-like macular dystrophy (STGD3), while homozygous inheritance of three more mutant variants causes severe seizures with ichthyosis, hypertonia, and even death. Some recent studies have described heterozygous inheritance in yet another three mutant ELOVL4 variants, two that cause spinocerebellar ataxia-34 (SCA34) with erythrokeratodermia (EKV) and one that causes SCA34 without EKV. We identified the specific enzymatic reactions catalyzed by ELOVL4 and, using a variety of genetically engineered mouse models, have actively searched for the mechanisms by which ELOVL4 impacts neural function and health. In this review, we critically compare and contrast the various animal model and case studies involving ELOVL4 deficiency via either mutation or deletion, and the resulting consequences on neuronal health and function in both the retina and central nervous system.
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Affiliation(s)
- Blake R Hopiavuori
- Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Robert E Anderson
- Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Reynolds Oklahoma Center on Aging, Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
| | - Martin-Paul Agbaga
- Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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20
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Agbaga MP, Merriman DK, Brush RS, Lydic TA, Conley SM, Naash MI, Jackson S, Woods AS, Reid GE, Busik JV, Anderson RE. Differential composition of DHA and very-long-chain PUFAs in rod and cone photoreceptors. J Lipid Res 2018; 59:1586-1596. [PMID: 29986998 PMCID: PMC6121944 DOI: 10.1194/jlr.m082495] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 06/28/2018] [Indexed: 11/20/2022] Open
Abstract
Long-chain PUFAs (LC-PUFAs; C20-C22; e.g., DHA and arachidonic acid) are highly enriched in vertebrate retina, where they are elongated to very-long-chain PUFAs (VLC-PUFAs; C 28) by the elongation of very-long-chain fatty acids-4 (ELOVL4) enzyme. These fatty acids play essential roles in modulating neuronal function and health. The relevance of different lipid requirements in rods and cones to disease processes, such as age-related macular degeneration, however, remains unclear. To better understand the role of LC-PUFAs and VLC-PUFAs in the retina, we investigated the lipid compositions of whole retinas or photoreceptor outer segment (OS) membranes in rodents with rod- or cone-dominant retinas. We analyzed fatty acid methyl esters and the molecular species of glycerophospholipids (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine) by GC-MS/GC-flame ionization detection and ESI-MS/MS, respectively. We found that whole retinas and OS membranes in rod-dominant animals compared with cone-dominant animals had higher amounts of LC-PUFAs and VLC-PUFAs. Compared with those of rod-dominant animals, retinas and OS membranes from cone-dominant animals also had about 2-fold lower levels of di-DHA (22:6/22:6) molecular species of glycerophospholipids. Because PUFAs are necessary for optimal G protein-coupled receptor signaling in rods, these findings suggest that cones may not have the same lipid requirements as rods.
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Affiliation(s)
- Martin-Paul Agbaga
- Departments of Ophthalmology University of Oklahoma Health Sciences Center, Oklahoma City, OK; Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK.
| | - Dana K Merriman
- McPherson Eye Research Institute, University of Wisconsin Oshkosh, Oshkosh, WI
| | - Richard S Brush
- Departments of Ophthalmology University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK
| | - Todd A Lydic
- Department of Physiology, Michigan State University, East Lansing, MI
| | - Shannon M Conley
- Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX
| | - Shelley Jackson
- National Institute on Drug Abuse Intramural Research Program Structural Biology Unit, Baltimore, MD
| | - Amina S Woods
- National Institute on Drug Abuse Intramural Research Program Structural Biology Unit, Baltimore, MD
| | - Gavin E Reid
- School of Chemistry and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, MI
| | - Robert E Anderson
- Departments of Ophthalmology University of Oklahoma Health Sciences Center, Oklahoma City, OK; Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK
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21
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Sudharsan R, Elliott MH, Dolgova N, Aguirre GD, Beltran WA. Photoreceptor Outer Segment Isolation from a Single Canine Retina for RPE Phagocytosis Assay. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1074:593-601. [PMID: 29721992 DOI: 10.1007/978-3-319-75402-4_72] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Protocols for photoreceptor outer segment (POS) isolation that can be used in phagocytosis assays of retinal pigment epithelium (RPE) cells have routinely used a large number of cow or pig eyes. However, when working with large animal models (e.g., dog, cats, transgenic pigs) of inherited retinal degenerative diseases, access to retinal tissues may be limited. An optimized protocol is presented in this paper to isolate sufficient POS from a single canine retina for use in RPE phagocytosis assays.
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Affiliation(s)
- Raghavi Sudharsan
- Division of Experimental Retinal Therapies, Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Michael H Elliott
- Department of Ophthalmology, University of Oklahoma Health Science Centre, Oklahoma City, OK, USA
| | - Natalia Dolgova
- Division of Experimental Retinal Therapies, Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Gustavo D Aguirre
- Division of Experimental Retinal Therapies, Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - William A Beltran
- Division of Experimental Retinal Therapies, Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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22
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Seno K, Hayashi F. Palmitoylation is a prerequisite for dimerization-dependent raftophilicity of rhodopsin. J Biol Chem 2017; 292:15321-15328. [PMID: 28747438 DOI: 10.1074/jbc.m117.804880] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/23/2017] [Indexed: 01/07/2023] Open
Abstract
The visual photopigment rhodopsin (Rh) is a prototypical G protein-coupled receptor (GPCR) responsible for initiation of the phototransduction cascade in rod photoreceptors. Similar to other GPCRs, Rh can form dimers or even higher oligomers and tends to have a supramolecular organization that is likely important in the dim light response. Rh also exhibits high affinity for lipid rafts (i.e. raftophilicity) upon light-dependent binding with the cognate G protein transducin (Gt), suggesting the presence of lipid raft-like domains in the retinal disk membrane and their importance in phototransduction. However, the relationship between Rh oligomerization and lipid rafts in the disk membrane remains to be explored. Given previous findings that Gt binds to dimeric Rh and that Rh is posttranslationally modified with two highly raftophilic palmitoyl moieties, we hypothesized that Rh becomes raftophilic upon dimerization. Here, using biochemical assays, we found that Rh*-Gt complexes in the detergent-resistant membrane are partially resistant to cholesterol depletion by methyl-β-cyclodextrin and that the Rh-to-Gt stoichiometry in this methyl-β-cyclodextrin-resistant complex is 2:1. Next, we found that IgG-mediated Rh-Rh cross-linking renders Rh highly raftophilic, supporting the premise that Rh becomes raftophilic upon dimerization. Rh depalmitoylation via reduction of thioester linkages blocked the translocation of IgG-cross-linked Rh to the detergent-resistant membrane, highlighting that the two palmitoyl moieties are important for the dimerization-dependent raftophilicity of Rh. These results indicate that palmitoylated GPCRs such as Rh can acquire raftophilicity upon G protein-stabilized dimerization and thereby organize receptor-cluster rafts by recruiting raftophilic lipids.
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Affiliation(s)
- Keiji Seno
- From the Department of Biology, Faculty of Medicine, and.,International Mass Imaging Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan and
| | - Fumio Hayashi
- the Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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23
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Protective effect of resveratrol against light-induced retinal degeneration in aged SAMP8 mice. Oncotarget 2017; 8:65778-65788. [PMID: 29029471 PMCID: PMC5630371 DOI: 10.18632/oncotarget.19473] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 06/24/2017] [Indexed: 12/17/2022] Open
Abstract
Purpose The purpose of this study was to determine the protective effects of Resveratrol (RESV) on acute bright light-induced retinal degeneration in aged senescence accelerated mouse strain. Methods Ten three-month-old male SAMP8 mice (prone to aging) were randomly assigned to two experimental dietary groups: one untreated group and one RESV treatment group (n=20 eyes for each group). After 30 days of treatment, mice were exposed to intense bright light. Ten male SAMR1 mice (resistant to aging) served as control (n=20 eyes). The protective effects of RESV administration on light-induced retinal degeneration in SAMP8 strain as well as the effect of bright light damage in the retinas of SAMP8 mice were analyzed by electroretinography (ERG), retinal histology, mRNA, protein and lipid profile. Results 68%-85% of a-wave amplitude and 72%-92% of b-wave amplitude were persevered by RESV in SAMP8 mice that were exposed to light damage. Also, RESV preserved their photoreceptor nuclei. mRNA expression of neuroprotective factors leukemia inhibitory factor (LIF), brain derived neurotrophic factor (BDNF), oncostatin M (OSM), cardiotrophin 1(CT-1) and cardiotrophin-like cytokine (CLC) were up-regulated 28, 8, 7, 5 and 9-fold in SAMP8 mice after RESV treatment. In addition, RESV could suppress the NF-κB pathway by down-regulating the expression of pIκB. Light damage led to increase of saturated FA, monoenoic FA, n6 PUFA and n6/n3 ratio and decrease of Docosahexaenoic acid (DHA). There was no significant difference on DHA and the ratio of n6/n3-FA between the untreated and RESV treated SAMP8 mice. Conclusions Collectively, our study provides evidence that RESV prevents light-induced retinal damage associated with aging.
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Garali I, Adanyeguh IM, Ichou F, Perlbarg V, Seyer A, Colsch B, Moszer I, Guillemot V, Durr A, Mochel F, Tenenhaus A. A strategy for multimodal data integration: application to biomarkers identification in spinocerebellar ataxia. Brief Bioinform 2017; 19:1356-1369. [DOI: 10.1093/bib/bbx060] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Indexed: 11/14/2022] Open
Affiliation(s)
- Imene Garali
- Bioinformatics and Biostatistics Core Facility of the Brain and Spine Institute, La Pitié-Salpêtriére Hospital, Paris, France
| | | | - Farid Ichou
- ICANalytics department, institute of cardiometabolism and nutrition, Paris, France
| | - Vincent Perlbarg
- Bioinformatics and Biostatistics Core Facility of the Brain and Spine Institute, La Pitié-Salpêtriére Hospital, Paris, France
| | - Alexandre Seyer
- SpectMet platform of the MedDay Pharmaceuticals company, Paris, France
| | | | - Ivan Moszer
- Bioinformatics and Biostatistics Core Facility of the Brain and Spine Institute, La Pitié-Salpêtriére Hospital, Paris, France
| | - Vincent Guillemot
- Institut Pasteur, Statistical Genetics group, Bioinformatics/Biostatistics Core Facility
| | | | - Fanny Mochel
- University Pierre and Marie Curie (UPMC) and the Pitié-Salpêtriére University Hospital
| | - Arthur Tenenhaus
- Bioinformatics and Biostatistics Core Facility of the Brain and Spine Institute, La Pitié-Salpêtriére Hospital, Paris, France
- L2S Laboratory at CentraleSupélec, France
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25
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Hopiavuori BR, Agbaga MP, Brush RS, Sullivan MT, Sonntag WE, Anderson RE. Regional changes in CNS and retinal glycerophospholipid profiles with age: a molecular blueprint. J Lipid Res 2017; 58:668-680. [PMID: 28202633 PMCID: PMC5392743 DOI: 10.1194/jlr.m070714] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 02/13/2017] [Indexed: 12/16/2022] Open
Abstract
We present here a quantitative molecular blueprint of the three major glycerophospholipid (GPL) classes, phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylethanolamine (PE), in retina and six regions of the brain in C57Bl6 mice at 2, 10, and 26 months of age. We found an age-related increase in molecular species containing saturated and monoenoic FAs and an overall decrease in the longer-chain PUFA molecular species across brain regions, with loss of DHA-containing molecular species as the most consistent and dramatic finding. Although we found very-long-chain PUFAs (VLC-PUFAs) (C28) in PC in the retina, no detectable levels were found in any brain region at any of the ages examined. All brain regions (except hippocampus and retina) showed a significant increase with age in PE plasmalogens. All three retina GPLs had di-PUFA molecular species (predominantly 44:12), which were most abundant in PS (∼30%). In contrast, low levels of di-PUFA GPL (1-2%) were found in all regions of the brain. This study provides a regional and age-related assessment of the brain's lipidome with a level of detail, inclusion, and quantification that has not heretofore been published.
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Affiliation(s)
- Blake R Hopiavuori
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Martin-Paul Agbaga
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Richard S Brush
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Michael T Sullivan
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - William E Sonntag
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Robert E Anderson
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104.
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26
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Skotland T, Sandvig K, Llorente A. Lipids in exosomes: Current knowledge and the way forward. Prog Lipid Res 2017; 66:30-41. [PMID: 28342835 DOI: 10.1016/j.plipres.2017.03.001] [Citation(s) in RCA: 642] [Impact Index Per Article: 91.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/14/2017] [Accepted: 03/21/2017] [Indexed: 12/29/2022]
Abstract
Lipids are essential components of exosomal membranes, and it is well-known that specific lipids are enriched in exosomes compared to their parent cells. In this review we discuss current knowledge about the lipid composition of exosomes. We compare published data for different lipid classes in exosomes, and what is known about their lipid species, i.e. lipid molecules with different fatty acyl groups. Moreover, we elaborate on the hypothesis about hand-shaking between the very-long-chain sphingolipids in the outer leaflet and PS 18:0/18:1 in the inner leaflet, and we propose this to be an important mechanism in membrane biology, not only for exosomes. The similarity between the lipid composition of exosomes, HIV particles, and detergent resistant membranes, used as lipid rafts models, is also discussed. Furthermore, we summarize knowledge about the role of specific lipids and lipid metabolizing enzymes on the formation and release of exosomes. Finally, the use of exosomal lipids as biomarkers and how the lipid composition of exosomes may be of importance for researchers aiming to use exosomes as drug delivery vehicles is discussed. In conclusion, we have summarized what is presently known about lipids in exosomes and identified issues that should be taken into consideration in future studies.
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Affiliation(s)
- Tore Skotland
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital-The Norwegian Radium Hospital, 0379 Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0379 Oslo, Norway.
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital-The Norwegian Radium Hospital, 0379 Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0379 Oslo, Norway; Department of Molecular Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Alicia Llorente
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital-The Norwegian Radium Hospital, 0379 Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0379 Oslo, Norway
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27
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Calvez P, Schmidt TF, Cantin L, Klinker K, Salesse C. Phosphatidylserine Allows Observation of the Calcium–Myristoyl Switch of Recoverin and Its Preferential Binding. J Am Chem Soc 2016; 138:13533-13540. [DOI: 10.1021/jacs.6b04218] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Philippe Calvez
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Thaís F. Schmidt
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Line Cantin
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Kristina Klinker
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Christian Salesse
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
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28
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Gu X, Reagan AM, McClellan ME, Elliott MH. Caveolins and caveolae in ocular physiology and pathophysiology. Prog Retin Eye Res 2016; 56:84-106. [PMID: 27664379 DOI: 10.1016/j.preteyeres.2016.09.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 09/15/2016] [Accepted: 09/20/2016] [Indexed: 12/14/2022]
Abstract
Caveolae are specialized, invaginated plasma membrane domains that are defined morphologically and by the expression of signature proteins called, caveolins. Caveolae and caveolins are abundant in a variety of cell types including vascular endothelium, glia, and fibroblasts where they play critical roles in transcellular transport, endocytosis, mechanotransduction, cell proliferation, membrane lipid homeostasis, and signal transduction. Given these critical cellular functions, it is surprising that ablation of the caveolae organelle does not result in lethality suggesting instead that caveolae and caveolins play modulatory roles in cellular homeostasis. Caveolar components are also expressed in ocular cell types including retinal vascular cells, Müller glia, retinal pigment epithelium (RPE), conventional aqueous humor outflow cells, the corneal epithelium and endothelium, and the lens epithelium. In the eye, studies of caveolae and other membrane microdomains (i.e., "lipid rafts") have lagged behind what is a substantial body of literature outside vision science. However, interest in caveolae and their molecular components has increased with accumulating evidence of important roles in vision-related functions such as blood-retinal barrier homeostasis, ocular inflammatory signaling, pathogen entry at the ocular surface, and aqueous humor drainage. The recent association of CAV1/2 gene loci with primary open angle glaucoma and intraocular pressure has further enhanced the need to better understand caveolar functions in the context of ocular physiology and disease. Herein, we provide the first comprehensive review of literature on caveolae, caveolins, and other membrane domains in the context of visual system function. This review highlights the importance of caveolae domains and their components in ocular physiology and pathophysiology and emphasizes the need to better understand these important modulators of cellular function.
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Affiliation(s)
- Xiaowu Gu
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Alaina M Reagan
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Mark E McClellan
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Michael H Elliott
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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29
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Goldberg AFX, Moritz OL, Williams DS. Molecular basis for photoreceptor outer segment architecture. Prog Retin Eye Res 2016; 55:52-81. [PMID: 27260426 DOI: 10.1016/j.preteyeres.2016.05.003] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/27/2016] [Accepted: 05/29/2016] [Indexed: 01/11/2023]
Abstract
To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ∼10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained.
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Affiliation(s)
- Andrew F X Goldberg
- Eye Research Institute, Oakland University, 417 Dodge Hall, Rochester, MI, 48309, USA.
| | - Orson L Moritz
- Department of Ophthalmology & Visual Sciences, University of British Columbia, Vancouver, BC, Canada
| | - David S Williams
- Department of Ophthalmology and Jules Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, USA
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30
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Brüggen B, Kremser C, Bickert A, Ebel P, Vom Dorp K, Schultz K, Dörmann P, Willecke K, Dedek K. Defective ceramide synthases in mice cause reduced amplitudes in electroretinograms and altered sphingolipid composition in retina and cornea. Eur J Neurosci 2016; 44:1700-13. [PMID: 27086873 DOI: 10.1111/ejn.13260] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 04/08/2016] [Indexed: 01/24/2023]
Abstract
Complex sphingolipids are strongly expressed in neuronal tissue and contain ceramides in their backbone. Ceramides are synthesized by six ceramide synthases (CerS1-6). Although it is known that each tissue has a unique profile of ceramide synthase expression and ceramide synthases are implicated in several neurodegenerative disorders, the expression of ceramide synthase isoforms has not been investigated in the retina. Here we demonstrate CerS1, CerS2 and CerS4 expression in mouse retina and cornea, with CerS4 ubiquitously expressed in all retinal neurons and Müller cells. To test whether ceramide synthase deficiency affects retinal function, we compared electroretinograms and retina morphology between wild-type and CerS1-, CerS2- and CerS4-deficient mice. Electroretinograms were strongly reduced in amplitude in ceramide synthase-deficient mice, suggesting that signalling in the outer retina is affected. However, the number of photoreceptors and cone outer segment length were unaltered and no changes in retinal layer thickness or synaptic structures were found. Mass spectrometric analyses of ceramides, hexosyl-ceramides and sphingomyelins showed that C20 to C24 acyl-containing species were decreased whereas C16-containing species were increased in the retina of ceramide synthase-deficient mice. Similar but smaller changes were also found in the cornea. Thus, we hypothesize that the replacement of very long-chain fatty acyl residues by shorter C16 residues may affect the electrical properties of retina and cornea, and alter receptor-mediated signal transduction, vesicle-mediated synaptic transmission or corneal light transmission. Future studies need to identify the molecular targets of ceramides or derived sphingolipids in light signal transduction and transmission in the eye.
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Affiliation(s)
- Bianca Brüggen
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany
| | | | - Andreas Bickert
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Philipp Ebel
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Katharina Vom Dorp
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany
| | - Konrad Schultz
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany
| | - Peter Dörmann
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany
| | - Klaus Willecke
- Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Karin Dedek
- Neurobiology, University of Oldenburg, 26111, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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31
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Albert A, Alexander D, Boesze-Battaglia K. Cholesterol in the rod outer segment: A complex role in a "simple" system. Chem Phys Lipids 2016; 199:94-105. [PMID: 27216754 DOI: 10.1016/j.chemphyslip.2016.04.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 04/22/2016] [Accepted: 04/23/2016] [Indexed: 12/01/2022]
Abstract
The rod outer segment (ROS) of retinal photoreceptor cells consists of disk membranes surrounded by the plasma membrane. It is a relatively uncomplicated system in which to investigate cholesterol distribution and its functional consequences in biologically relevant membranes. The light sensitive protein, rhodopsin is the major protein in both membranes, but the lipid compositions are significantly different in the disk and plasma membranes. Cholesterol is high in the ROS plasma membrane. Disk membranes are synthesized at the base of the ROS and are also high in cholesterol. However, cholesterol is rapidly depleted as the disks are apically displaced. During this apical displacement the disk phospholipid fatty acyl chains become progressively more unsaturated, which creates an environment unfavorable to cholesterol. Membrane cholesterol has functional consequences. The high cholesterol found in the plasma membrane and in newly synthesized disks inhibits the activation of rhodopsin. As disks are apically displaced and cholesterol is depleted rhodopsin becomes more responsive to light. This effect of cholesterol on rhodopsin activation has been shown in both native and reconstituted membranes. The modulation of activity can be at least partially explained by the effect of cholesterol on bulk lipid properties. Cholesterol decreases the partial free volume of the hydrocarbon region of the bilayer and thereby inhibits rhodopsin conformational changes required for activation. However, cholesterol binds to rhodopsin and may directly affect the protein also. Furthermore, cholesterol stabilizes rhodopsin to thermal denaturation. The membrane must provide an environment that allows rhodopsin conformational changes required for activation while also stabilizing the protein to thermal denaturation. Cholesterol thus plays a complex role in modulating the activity and stability of rhodopsin, which have implications for other G-protein coupled receptors.
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32
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Stiles M, Qi H, Sun E, Tan J, Porter H, Allegood J, Chalfant CE, Yasumura D, Matthes MT, LaVail MM, Mandal NA. Sphingolipid profile alters in retinal dystrophic P23H-1 rats and systemic FTY720 can delay retinal degeneration. J Lipid Res 2016; 57:818-31. [PMID: 26947037 DOI: 10.1194/jlr.m063719] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Indexed: 12/28/2022] Open
Abstract
Retinal degeneration (RD) affects millions of people and is a major cause of ocular impairment and blindness. With a wide range of mutations and conditions leading to degeneration, targeting downstream processes is necessary for developing effective treatments. Ceramide and sphingosine-1-phosphate, a pair of bioactive sphingolipids, are involved in apoptosis and its prevention, respectively. Apoptotic cell death is a potential driver of RD, and in order to understand the mechanism of degeneration and potential treatments, we studied rhodopsin mutant RD model, P23H-1 rats. Investigating this genetic model of human RD allows us to investigate the association of sphingolipid metabolites with the degeneration of the retina in P23H-1 rats and the effects of a specific modulator of sphingolipid metabolism, FTY720. We found that P23H-1 rat retinas had altered sphingolipid profiles that, when treated with FTY720, were rebalanced closer to normal levels. FTY720-treated rats also showed protection from RD compared with their vehicle-treated littermates. Based on these data, we conclude that sphingolipid dysregulation plays a secondary role in retinal cell death, which may be common to many forms of RDs, and that the U.S. Food and Drug Administration-approved drug FTY720 or related compounds that modulate sphingolipid metabolism could potentially delay the cell death.
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Affiliation(s)
- Megan Stiles
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Hui Qi
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Eleanor Sun
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Jeremy Tan
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Hunter Porter
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104
| | - Jeremy Allegood
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298
| | - Charles E Chalfant
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298 Research and Development, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, VA 23249 Virginia Commonwealth University School of Medicine, Virginia Commonwealth University Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298 Virginia Commonwealth University Institute of Molecular Medicine and the Virginia Commonwealth University Johnson Center, Virginia Commonwealth University, Richmond, VA 23298
| | - Douglas Yasumura
- Beckman Vision Center, University of California, San Francisco School of Medicine, San Francisco, CA 94143
| | - Michael T Matthes
- Beckman Vision Center, University of California, San Francisco School of Medicine, San Francisco, CA 94143
| | - Matthew M LaVail
- Beckman Vision Center, University of California, San Francisco School of Medicine, San Francisco, CA 94143
| | - Nawajes A Mandal
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Dean McGee Eye Institute, Oklahoma City, OK 73104 Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104 Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
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33
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Widomska J, Zareba M, Subczynski WK. Can Xanthophyll-Membrane Interactions Explain Their Selective Presence in the Retina and Brain? Foods 2016; 5. [PMID: 27030822 PMCID: PMC4809277 DOI: 10.3390/foods5010007] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Epidemiological studies demonstrate that a high dietary intake of carotenoids may offer protection against age-related macular degeneration, cancer and cardiovascular and neurodegenerative diseases. Humans cannot synthesize carotenoids and depend on their dietary intake. Major carotenoids that have been found in human plasma can be divided into two groups, carotenes (nonpolar molecules, such as β-carotene, α-carotene or lycopene) and xanthophylls (polar carotenoids that include an oxygen atom in their structure, such as lutein, zeaxanthin and β-cryptoxanthin). Only two dietary carotenoids, namely lutein and zeaxanthin (macular xanthophylls), are selectively accumulated in the human retina. A third carotenoid, meso-zeaxanthin, is formed directly in the human retina from lutein. Additionally, xanthophylls account for about 70% of total carotenoids in all brain regions. Some specific properties of these polar carotenoids must explain why they, among other available carotenoids, were selected during evolution to protect the retina and brain. It is also likely that the selective uptake and deposition of macular xanthophylls in the retina and brain are enhanced by specific xanthophyll-binding proteins. We hypothesize that the high membrane solubility and preferential transmembrane orientation of macular xanthophylls distinguish them from other dietary carotenoids, enhance their chemical and physical stability in retina and brain membranes and maximize their protective action in these organs. Most importantly, xanthophylls are selectively concentrated in the most vulnerable regions of lipid bilayer membranes enriched in polyunsaturated lipids. This localization is ideal if macular xanthophylls are to act as lipid-soluble antioxidants, which is the most accepted mechanism through which lutein and zeaxanthin protect neural tissue against degenerative diseases.
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Affiliation(s)
- Justyna Widomska
- Department of Biophysics, Medical University of Lublin, 20-090 Lublin, Poland
- Correspondence: ; Tel.: +48-81-479-7169
| | - Mariusz Zareba
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA;
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Lor C, Hirst LS. Effects of Low Concentrations of Docosahexaenoic Acid on the Structure and Phase Behavior of Model Lipid Membranes. MEMBRANES 2015; 5:857-74. [PMID: 26690231 PMCID: PMC4704016 DOI: 10.3390/membranes5040857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/25/2015] [Indexed: 11/21/2022]
Abstract
In this paper we report an X-ray diffraction study on the phase behavior of binary lipid mixtures of 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (DHA-PE) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at low concentrations below 5.0 mol% DHA-PE. Our results show that DHA-PE induces phase separation into a DHA rich liquid crystalline (Lα) phase and a DHA poor gel (Lβ') phase at overall DHA-PE concentrations as low as 0.1 mol%. In addition, we find that the structure of the Lβ' phase, from which the DHA-PE molecules are largely excluded, is modified in the phase-separated state at low DHA-PE concentrations, with a decrease in bilayer thickness of 1.34 nm for 0.1 mol% at room temperature, compared to pure DPPC bilayers. This result is contrary to that seen in similar studies on mono-unsaturated lipids where an increase in bilayer thickness is observed. The surprising effect of such low DHA-PE concentrations on membrane structure may be important in understanding the role of highly polyunsaturated lipids in biological membrane-based structures and similar artificial surfactant systems.
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Affiliation(s)
- Chai Lor
- Bioengineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA 95343, USA.
| | - Linda S Hirst
- Department of Physics, School of Natural Sciences, University of California, Merced, CA 95343, USA.
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Koch KW, Dell'Orco D. Protein and Signaling Networks in Vertebrate Photoreceptor Cells. Front Mol Neurosci 2015; 8:67. [PMID: 26635520 PMCID: PMC4646965 DOI: 10.3389/fnmol.2015.00067] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/26/2015] [Indexed: 01/10/2023] Open
Abstract
Vertebrate photoreceptor cells are exquisite light detectors operating under very dim and bright illumination. The photoexcitation and adaptation machinery in photoreceptor cells consists of protein complexes that can form highly ordered supramolecular structures and control the homeostasis and mutual dependence of the secondary messengers cyclic guanosine monophosphate (cGMP) and Ca2+. The visual pigment in rod photoreceptors, the G protein-coupled receptor rhodopsin is organized in tracks of dimers thereby providing a signaling platform for the dynamic scaffolding of the G protein transducin. Illuminated rhodopsin is turned off by phosphorylation catalyzed by rhodopsin kinase (GRK1) under control of Ca2+-recoverin. The GRK1 protein complex partly assembles in lipid raft structures, where shutting off rhodopsin seems to be more effective. Re-synthesis of cGMP is another crucial step in the recovery of the photoresponse after illumination. It is catalyzed by membrane bound sensory guanylate cyclases (GCs) and is regulated by specific neuronal Ca2+-sensor proteins called guanylate cyclase-activating proteins (GCAPs). At least one GC (ROS-GC1) was shown to be part of a multiprotein complex having strong interactions with the cytoskeleton and being controlled in a multimodal Ca2+-dependent fashion. The final target of the cGMP signaling cascade is a cyclic nucleotide-gated (CNG) channel that is a hetero-oligomeric protein located in the plasma membrane and interacting with accessory proteins in highly organized microdomains. We summarize results and interpretations of findings related to the inhomogeneous organization of signaling units in photoreceptor outer segments.
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Affiliation(s)
- Karl-Wilhelm Koch
- Department of Neurosciences, Biochemistry Group, University of Oldenburg Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry and Center for BioMedical Computing (CBMC), University of Verona Verona, Italy
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Demers É, Boisselier É, Horchani H, Blaudez D, Calvez P, Cantin L, Belley N, Champagne S, Desbat B, Salesse C. Lipid Selectivity, Orientation, and Extent of Membrane Binding of Nonacylated RP2. Biochemistry 2015; 54:2560-70. [DOI: 10.1021/bi501517r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Éric Demers
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Élodie Boisselier
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Habib Horchani
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Daniel Blaudez
- CBMN-UMR
5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy
Saint Hilaire, 33600 Pessac, France
| | - Philippe Calvez
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Line Cantin
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Nicolas Belley
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sophie Champagne
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Bernard Desbat
- CBMN-UMR
5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy
Saint Hilaire, 33600 Pessac, France
| | - Christian Salesse
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
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Bernier SC, Horchani H, Salesse C. Structure and binding of the C-terminal segment of R9AP to lipid monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1967-1979. [PMID: 25614992 DOI: 10.1021/la503867h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Phototransduction cascade takes place in disc membranes of photoreceptor cells. Following its activation by light, rhodopsin activates the G-protein transducin causing the dissociation of its GTP-bound α-subunit, which in turn activates phosphodiesterase 6 (PDE6) leading to the hyperpolarization of photoreceptor cells. PDE6 must then be inactivated to return to the dark state. This is achieved by a protein complex which is presumably anchored to photoreceptor disc membranes by means of the transmembrane C-terminal segment of RGS9-1-Anchor Protein (R9AP). Information on the secondary structure and membrane binding properties of the C-terminal segment of R9AP is not yet available to further support its role in the membrane anchoring of this protein. In the present study, circular dichroism and infrared spectroscopy measurements have allowed us to determine that the C-terminal segment of human and bovine R9AP adopts an α-helical structure in solution. Moreover, this C-terminal segment has shown affinity for most of the phospholipids typical of photoreceptor membranes. In fact, the physical state and the type of phospholipid as well as electrostatic interactions influence the binding of the human and bovine peptides to phospholipid monolayers. In addition, these measurements revealed that the human peptide has a high affinity for saturated phosphocholine, which may suggest a possible localization of R9AP in photoreceptor microdomains. Accordingly, infrared spectroscopy measurements have allowed determining that the C-terminal segment of R9AP adopts an ordered α-helical structure in the presence of saturated phospholipid monolayers. Altogether, these data are consistent with the typical α-helical secondary structure and behavior observed for transmembrane segments and with the proposed role of membrane anchoring of the C-terminal segment of human and bovine R9AP.
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Affiliation(s)
- Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval , Québec (Québec) Canada
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Zulliger R, Naash MI, Rajala RVS, Molday RS, Azadi S. Impaired association of retinal degeneration-3 with guanylate cyclase-1 and guanylate cyclase-activating protein-1 leads to leber congenital amaurosis-1. J Biol Chem 2014; 290:3488-99. [PMID: 25477517 DOI: 10.1074/jbc.m114.616656] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
One-fifth of all cases of Leber congenital amaurosis are type 1 (LCA1). LCA1 is a severe form of retinal dystrophy caused by loss-of-function mutations in guanylate cyclase 1 (GC1), a key member of the phototransduction cascade involved in modulating the photocurrents. Although GC1 has been studied for some time, the mechanisms responsible for its regulation and membrane targeting are not fully understood. We reported earlier that retinal degeneration 3 (RD3) protein interacts with GC1 and promotes its targeting to the photoreceptor outer segments (POS). Here, we extend our studies to show a direct association between RD3 and guanylate cyclase activating protein 1 (GCAP1). Furthermore, we demonstrate that this functional interaction is important for GC1 targeting to POS. We also show that most LCA1-causing mutations in GC1 result in lost GC1 interaction with RD3 or GC1 being targeted to the plasma membrane. Our data suggest that GC1, GCAP1, and RD3 form a complex in the endoplasmic reticulum that targets GC1 to POS. Interruption of this assembly is likely the underlying mechanism for a subset of LCA1. This study offers insights for the development of therapeutic strategies to treat this severe form of blindness.
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Affiliation(s)
| | | | - Raju V S Rajala
- From the Departments of Cell Biology, Ophthalmology, and Physiology, University of Oklahoma Health Sciences Center and the Dean McGee Eye Institute, Oklahoma City, Oklahoma 73104 and
| | - Robert S Molday
- the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Seifollah Azadi
- From the Departments of Cell Biology, the Dean McGee Eye Institute, Oklahoma City, Oklahoma 73104 and
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Mandal NA, Tran JTA, Zheng L, Wilkerson JL, Brush RS, McRae J, Agbaga MP, Zhang K, Petrukhin K, Ayyagari R, Anderson RE. In vivo effect of mutant ELOVL4 on the expression and function of wild-type ELOVL4. Invest Ophthalmol Vis Sci 2014; 55:2705-13. [PMID: 24644051 DOI: 10.1167/iovs.13-13198] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Mutations in the elongation of very long chain fatty acids 4 (ELOVL4) gene cause human Stargardt's macular dystrophy 3 (STGD3), a juvenile onset dominant form of macular degeneration. To understand the role of the ELOVL4 protein in retinal function, several mouse models have been developed by using transgenic (TG), knock-in (Elovl4(+/mut)), and knockout (Elovl4(+/-)) approaches. Here we analyzed quantitatively the ELOVL4 protein and its enzymatic products (very long chain saturated fatty acid [VLC-FA] and VLC-polyunsaturated fatty acid [VLC-PUFA]) in the retinas of 8 to 10-week-old TG1(+), TG2(+), and Elovl4(+/mut) mice that harbor the mutant ELOVL4 and compared them to their wild-type littermates and Elovl4(+/-) that do not express the mutant protein. We also analyzed skin from these mice to gain insight into the pathogenesis resulting from the ELOVL4 mutation. METHODS ELOVL4 protein localization in the retina was determined by immunohistochemistry. Levels of wild-type ELOVL4 protein in skin and retinas were determined by Western blotting. Total lipids from skin and retinas were measured by gas chromatography-mass spectrometry (GC-MS). Retinal glycerophosphatidylcholines (PC) were analyzed by tandem mass spectrometry. RESULTS Immunohistochemical and Western analysis indicated that wild-type ELOVL4 protein was reduced in heterozygous Elovl4(+/mut) and Elovl4(+/-) retinas, but not in TG2(+) retinas. We found that VLC-FA was reduced by 50% in the skin of Elovl4(+/-) and by 60% to 65% in Elovl4(+/mut). We found VLC-PUFA levels at ∼ 50% in both the retinas, and wild-type levels of VLC-PUFA in TG2(+) retinas. CONCLUSIONS We conclude that the presence of the mutant ELOVL4 does not affect the function of wild-type ELOVL4 in the fully developed 8- to 10-week-old retinas.
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Affiliation(s)
- Nawajes A Mandal
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
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Bennett LD, Hopiavuori BR, Brush RS, Chan M, Van Hook MJ, Thoreson WB, Anderson RE. Examination of VLC-PUFA-deficient photoreceptor terminals. Invest Ophthalmol Vis Sci 2014; 55:4063-72. [PMID: 24764063 DOI: 10.1167/iovs.14-13997] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Juvenile-onset autosomal dominant Stargardt-like macular dystrophy (STGD3) is caused by mutations in ELOVL4 (elongation of very long fatty acids-4), an elongase necessary for the biosynthesis of very long chain fatty acids (VLC-FAs ≥ C26). Photoreceptors are enriched with VLC polyunsaturated fatty acids (VLC-PUFAs), which are necessary for long-term survival of rod photoreceptors. The purpose of these studies was to determine the effect of deletion of VLC-PUFAs on rod synaptic function in retinas of mice conditionally depleted (KO) of Elovl4. METHODS Retina function was assessed in wild-type (WT) and KO by electroretinography. Outer plexiform structure was evaluated by immunofluorescence and transmission electron microscopy. Single-cell recordings measured rod ion channel operation and rod bipolar glutamate signaling. Sucrose gradient centrifugation was used to isolate synaptosomes from bovine retina. Proteins and lipids were analyzed by Western blotting and tandem mass spectroscopy, respectively. RESULTS Inner retinal responses (b-wave, oscillatory potentials, and scotopic threshold responses) of the ERG were decreased in the KO mice compared to controls. However the rod ion channel operation and bipolar glutamate responses were comparable between groups. Biochemical analysis revealed that conventional and ribbon synapses have VLC-PUFAs. Ultrastructural analysis showed that the outer plexiform layer was disorganized and the diameter of vesicles in rod terminals was smaller in the KO mice. CONCLUSIONS Very long chain PUFAs affect rod function by contributing to synaptic vesicle size, which may alter the dynamics of synaptic transmission, ultimately resulting in a loss of neuronal connectivity and death of rod photoreceptors.
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Affiliation(s)
- Lea D Bennett
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Blake R Hopiavuori
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Richard S Brush
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Michael Chan
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Matthew J Van Hook
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska, United States
| | - Wallace B Thoreson
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska, United States Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, United States
| | - Robert E Anderson
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
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Abstract
Age-related macular degeneration (AMD) is associated with a low level of macular carotenoids in the eye retina. Only two carotenoids, namely lutein and zeaxanthin are selectively accumulated in the human eye retina from blood plasma where more than twenty other carotenoids are available. The third carotenoid which is found in the human retina, meso-zeaxanthin is formed directly in the retina from lutein. All these carotenoids, named also macular xanthophylls, play key roles in eye health and retinal disease. Macular xanthophylls are thought to combat light-induced damage mediated by reactive oxygen species by absorbing the most damaging incoming wavelength of light prior to the formation of reactive oxygen species (a function expected of carotenoids in nerve fibers) and by chemically and physically quenching reactive oxygen species once they are formed (a function expected of carotenoids in photoreceptor outer segments). There are two major hypotheses about the precise location of macular xanthophylls in the nerve fiber layer of photoreceptor axons and in photoreceptor outer segments. According to the first, macular xanthophylls transversely incorporate in the lipid-bilayer portion of membranes of the human retina. According to the second, macular xanthophylls are protein-bound by membrane-associated, xanthophyll-binding proteins. In this review we indicate specific properties of macular xanthophylls that could help explain their selective accumulation in the primate retina with special attention paid to xanthophyll-membrane interactions.
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Affiliation(s)
- Justyna Widomska
- Department of Biophysics, Medical University of Lublin, Lublin, Poland
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Gu X, Fliesler SJ, Zhao YY, Stallcup WB, Cohen AW, Elliott MH. Loss of caveolin-1 causes blood-retinal barrier breakdown, venous enlargement, and mural cell alteration. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 184:541-55. [PMID: 24326256 DOI: 10.1016/j.ajpath.2013.10.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/13/2013] [Accepted: 10/28/2013] [Indexed: 12/20/2022]
Abstract
Blood-retinal barrier (BRB) breakdown and related vascular changes are implicated in several ocular diseases. The molecules and mechanisms regulating BRB integrity and pathophysiology are not fully elucidated. Caveolin-1 (Cav-1) ablation results in loss of caveolae and microvascular pathologies, but the role of Cav-1 in the retina is largely unknown. We examined BRB integrity and vasculature in Cav-1 knockout mice and found a significant increase in BRB permeability, compared with wild-type controls, with branch veins being frequent sites of breakdown. Vascular hyperpermeability occurred without apparent alteration in junctional proteins. Such hyperpermeability was not rescued by inhibiting eNOS activity. Veins of Cav-1 knockout retinas exhibited additional pathological features, including i) eNOS-independent enlargement, ii) altered expression of mural cell markers (eg, down-regulation of NG2 and up-regulation of αSMA), and iii) dramatic alterations in mural cell phenotype near the optic nerve head. We observed a significant NO-dependent increase in retinal artery diameter in Cav-1 knockout mice, suggesting that Cav-1 plays a role in autoregulation of resistance vessels in the retina. These findings implicate Cav-1 in maintaining BRB integrity in retinal vasculature and suggest a previously undefined role in the retinal venous system and associated mural cells. Our results are relevant to clinically significant retinal disorders with vascular pathologies, including diabetic retinopathy, uveoretinitis, and primary open-angle glaucoma.
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Affiliation(s)
- Xiaowu Gu
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Steven J Fliesler
- Research Service, Veterans Affairs Western New York Healthcare System, Buffalo, New York; Department of Ophthalmology, University at Buffalo, State University of New York, Buffalo, New York; Department of Biochemistry, University at Buffalo, State University of New York, Buffalo, New York; SUNY Eye Institute, University at Buffalo, State University of New York, Buffalo, New York
| | - You-Yang Zhao
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois; Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, Illinois
| | - William B Stallcup
- Tumor Microenvironment Program, Cancer Center, Sanford-Burnham Medical Research Institute, La Jolla, California
| | - Alex W Cohen
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Michael H Elliott
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma.
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Yam XY, Birago C, Fratini F, Di Girolamo F, Raggi C, Sargiacomo M, Bachi A, Berry L, Fall G, Currà C, Pizzi E, Breton CB, Ponzi M. Proteomic analysis of detergent-resistant membrane microdomains in trophozoite blood stage of the human malaria parasite Plasmodium falciparum. Mol Cell Proteomics 2013; 12:3948-61. [PMID: 24045696 DOI: 10.1074/mcp.m113.029272] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intracellular pathogens contribute to a significant proportion of infectious diseases worldwide. The successful strategy of evading the immune system by hiding inside host cells is common to all the microorganism classes, which exploit membrane microdomains, enriched in cholesterol and sphingolipids, to invade and colonize the host cell. These assemblies, with distinct biochemical properties, can be isolated by means of flotation in sucrose density gradient centrifugation because they are insoluble in nonionic detergents at low temperature. We analyzed the protein and lipid contents of detergent-resistant membranes from erythrocytes infected by Plasmodium falciparum, the most deadly human malaria parasite. Proteins associated with membrane microdomains of trophic parasite blood stages (trophozoites) include an abundance of chaperones, molecules involved in vesicular trafficking, and enzymes implicated in host hemoglobin degradation. About 60% of the identified proteins contain a predicted localization signal suggesting a role of membrane microdomains in protein sorting/trafficking. To validate our proteomic data, we raised antibodies against six Plasmodium proteins not characterized previously. All the selected candidates were recovered in floating low-density fractions after density gradient centrifugation. The analyzed proteins localized either to internal organelles, such as the mitochondrion and the endoplasmic reticulum, or to exported membrane structures, the parasitophorous vacuole membrane and Maurer's clefts, implicated in targeting parasite proteins to the host erythrocyte cytosol or surface. The relative abundance of cholesterol and phospholipid species varies in gradient fractions containing detergent-resistant membranes, suggesting heterogeneity in the lipid composition of the isolated microdomain population. This study is the first report showing the presence of cholesterol-rich microdomains with distinct properties and subcellular localization in trophic stages of Plasmodium falciparum.
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Affiliation(s)
- Xue Yan Yam
- University Montpellier II, CNRS UMR 5235, 34095 Montpellier, Cedex 5, France
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Chen H, Tran JTA, Eckerd A, Huynh TP, Elliott MH, Brush RS, Mandal NA. Inhibition of de novo ceramide biosynthesis by FTY720 protects rat retina from light-induced degeneration. J Lipid Res 2013; 54:1616-1629. [PMID: 23468130 DOI: 10.1194/jlr.m035048] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Light-induced retinal degeneration (LIRD) in albino rats causes apoptotic photoreceptor cell death. Ceramide is a second messenger for apoptosis. We tested whether increases in ceramide mediate photoreceptor apoptosis in LIRD and if inhibition of ceramide synthesis protects the retina. Sprague-Dawley rats were exposed to 2,700 lux white light for 6 h, and the retinal levels of ceramide and its intermediary metabolites were measured by GC-MS or electrospray ionization tandem mass spectrometry. Enzymes of the de novo biosynthetic and sphingomyelinase pathways of ceramide generation were assayed, and gene expression was measured. The dosage and temporal effect of the ceramide synthase inhibitor FTY720 on the LIRD retina were measured by histological and functional analyses. Retinal ceramide levels increased coincident with the increase of dihydroceramide at various time points after light stress. Light stress in retina induces ceramide generation predominantly through the de novo pathway, which was prevented by systemic administration of FTY720 (10 mg/kg) leading to the protection of retinal structure and function. The neuroprotection of FTY720 was independent of its immunosuppressive action. We conclude that ceramide increase by de novo biosynthesis mediates photoreceptor apoptosis in the LIRD model and that inhibition of ceramide production protects the retina against light stress.
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Affiliation(s)
- Hui Chen
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and; Ophthalmology Department, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, Chengdu City, Sichuan, 610072, China
| | - Julie-Thu A Tran
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and
| | - Annette Eckerd
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and
| | - Tuan-Phat Huynh
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and
| | - Michael H Elliott
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Departments of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and
| | - Richard S Brush
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and
| | - Nawajes A Mandal
- Departments of Ophthalmology and University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Departments of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104; Dean McGee Eye Institute, Oklahoma City, OK 73104; and.
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Mandal NA, Tran JTA, Saadi A, Rahman AK, Huynh TP, Klein WH, Cho JH. Expression and localization of CERKL in the mammalian retina, its response to light-stress, and relationship with NeuroD1 gene. Exp Eye Res 2012; 106:24-33. [PMID: 23142158 DOI: 10.1016/j.exer.2012.10.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 10/25/2012] [Accepted: 10/26/2012] [Indexed: 01/30/2023]
Abstract
Mutations in the Ceramide kinase like (CERKL) gene are associated with retinitis pigmentosa (RP26) and cone-rod dystrophy. CERKL is homologous to Ceramide kinase (CERK), and its function is still unknown. The purpose of this study was to test the expression and distribution of this gene and its protein in rat and in mouse tissues, in light-stressed rat retinas and in the retinas of NeuroD1 knock-out mice to understand the role of CERKL in the retina. Expression of Cerkl and Cerk mRNA was determined by quantitative RT-PCR. Expression of the protein was determined by Western blotting with anti-CERKL antibody. Localization of the protein was determined by using immunofluorescence microscopy. With qRT-PCR, we revealed that the relative mRNA expression of Cerkl was the highest in the retina among all the rat tissue tested; it was >10-fold higher than in the brain. On the other hand, Cerk has ubiquitous expression and its relative abundance is >2 fold of Cerkl in the retina. Cerkl was expressed minimally in the developing mouse eyes and reached a peak at retinal maturity at 2 months. Western blots of retinal tissues revealed two major CERKL protein bands: 59 kDa (C1) and 37 kDa (C2). However, only C2 CERKL was found in the rat retinal rod outer segment (ROS) at level of that was not changed in light vs. dark adaptation. In the light-stressed retina, expression of Cerkl mRNA increased significantly, which was reflected in only on C2 CERKL protein. The CERKL protein localized prominently to the ganglion cells, inner nuclear layers (INL), retinal pigment epithelial (RPE) cells, and photoreceptor inner segments in the retinal sections. Nuclear localization of CERKL was not affected in RPE, INL and the ganglion cell layers in the light-stressed retina; however, the perinuclear and outer segment locations appear to be altered. In the NeuroD1 knock-out mouse retina, the expression of Cerkl mRNA and protein decreased and that decrease also pertains to C2 CERKL. In conclusion, the retina had the highest level of Cerkl mRNA and protein expression, which reached its maximum in the adult retina; CERKL localized to ROS and RPE cells and the light-adaptation did not change the level of CERKL in ROS; light-stress induced Cerkl expression in the retina; and its expression decreased in NeuroD1 knock-out retina. Thus, CERKL may be important for the stress responses and protection of photoreceptor cells.
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Affiliation(s)
- Nawajes A Mandal
- Department of Ophthalmology, OUHSC, Dean A. McGee Eye Institute, Oklahoma City, OK 73104, United States.
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Boisselier É, Calvez P, Demers É, Cantin L, Salesse C. Influence of the physical state of phospholipid monolayers on protein binding. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:9680-8. [PMID: 22686284 DOI: 10.1021/la301135z] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Langmuir monolayers were used to characterize the influence of the physical state of phospholipid monolayers on the binding of protein Retinis Pigmentosa 2 (RP2). The binding parameters of RP2 (maximum insertion pressure (MIP), synergy and ΔΠ(0)) in monolayers were thus analyzed in the presence of phospholipids bearing increasing fatty acyl chain lengths at temperatures where their liquid-expanded (LE), liquid-condensed (LC), or solid-condensed (SC) states can be individually observed. The data show that a larger value of synergy is observed in the LC/SC states than in the LE state, independent of the fatty acyl chain length of phospholipids. Moreover, both the MIP and the ΔΠ(0) increase with the fatty acyl chain length when phospholipids are in the LC/SC state, whereas those binding parameters remain almost unchanged when phospholipids are in the LE state. This effect of the phospholipid physical state on the binding of RP2 was further demonstrated by measurements performed in the presence of a phospholipid monolayer showing a phase transition from the LE to the LC state at room temperature. The data collected are showing that very similar values of MIP but very different values of synergy and ΔΠ(0) are obtained in the LE (below the phase transition) and LC (above the phase transition) states. In addition, the binding parameters of RP2 in the LE (below the phase transition) as well as in the LC (above the phase transition) states were found to be indistinguishable from those where single LC and LE states are respectively observed. The preference of RP2 for binding phospholipids in the LC state was then confirmed by the observation of a large modification of the shape of the LC domains in the phase transition. Therefore, protein binding parameters can be strongly influenced by the physical state of phospholipid monolayers. Moreover, measurements performed with the α/β domain of RP2 strongly suggest that the β helix of RP2 plays a major role in the preferential binding of this protein to phospholipids in the LC state.
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Affiliation(s)
- Élodie Boisselier
- LOEX/CUO-recherche, Hôpital du Saint-Sacrement, Centre Hospitalier Affilié de Québec, and Département d'Ophtalmologie, Faculté de Médecine, and PROTEO, Université Laval, Québec, Canada G1S 4L8
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Li X, McClellan ME, Tanito M, Garteiser P, Towner R, Bissig D, Berkowitz BA, Fliesler SJ, Woodruff ML, Fain GL, Birch DG, Khan MS, Ash JD, Elliott MH. Loss of caveolin-1 impairs retinal function due to disturbance of subretinal microenvironment. J Biol Chem 2012; 287:16424-34. [PMID: 22451674 DOI: 10.1074/jbc.m112.353763] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Caveolin-1 (Cav-1), an integral component of caveolar membrane domains, is expressed in several retinal cell types, including photoreceptors, retinal vascular endothelial cells, Müller glia, and retinal pigment epithelium (RPE) cells. Recent evidence links Cav-1 to ocular diseases, including autoimmune uveitis, diabetic retinopathy, and primary open angle glaucoma, but its role in normal vision is largely undetermined. In this report, we show that ablation of Cav-1 results in reduced inner and outer retinal function as measured, in vivo, by electroretinography and manganese-enhanced MRI. Somewhat surprisingly, dark current and light sensitivity were normal in individual rods (recorded with suction electrode methods) from Cav-1 knock-out (KO) mice. Although photoreceptor function was largely normal, in vitro, the apparent K(+) affinity of the RPE-expressed α1-Na(+)/K(+)-ATPase was decreased in Cav-1 KO mice. Cav-1 KO retinas also displayed unusually tight adhesion with the RPE, which could be resolved by brief treatment with hyperosmotic medium, suggesting alterations in outer retinal fluid homeostasis. Collectively, these findings demonstrate that reduced retinal function resulting from Cav-1 ablation is not photoreceptor-intrinsic but rather involves impaired subretinal and/or RPE ion/fluid homeostasis.
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Affiliation(s)
- Xiaoman Li
- Department of Ophthalmology and Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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Yu M, Benham A, Logan S, Brush RS, Mandal MNA, Anderson RE, Agbaga MP. ELOVL4 protein preferentially elongates 20:5n3 to very long chain PUFAs over 20:4n6 and 22:6n3. J Lipid Res 2012; 53:494-504. [PMID: 22158834 PMCID: PMC3276472 DOI: 10.1194/jlr.m021386] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We hypothesized that reduction/loss of very long chain PUFAs (VLC-PUFAs) due to mutations in the ELOngase of very long chain fatty acid-4 (ELOVL4) protein contributes to retinal degeneration in autosomal dominant Stargardt-like macular dystrophy (STGD3) and age-related macular degeneration; hence, increasing VLC-PUFA in the retina of these patients could provide some therapeutic benefits. Thus, we tested the efficiency of elongation of C20-C22 PUFA by the ELOVL4 protein to determine which substrates are the best precursors for biosynthesis of VLC-PUFA. The ELOVL4 protein was expressed in pheochromocytoma cells, while green fluorescent protein-expressing and nontransduced cells served as controls. The cells were treated with 20:5n3, 22:6n3, and 20:4n6, either individually or in equal combinations. Both transduced and control cells internalized and elongated the supplemented FAs to C22-C26 precursors. Only ELOVL4-expressing cells synthesized C28-C38 VLC-PUFA from these precursors. In general, 20:5n3 was more efficiently elongated to VLC-PUFA in the ELOVL4-expressing cells, regardless of whether it was in combination with 22:6n3 or with 20:4n6. In each FA treatment group, C34 and C36 VLC-PUFAs were the predominant VLC-PUFAs in the ELOVL4-expressing cells. In summary, 20:5n3, followed by 20:4n6, seems to be the best precursor for boosting the synthesis of VLC-PUFA by ELOVL4 protein.
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Affiliation(s)
- Man Yu
- Departments of Ophthalmology and Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, P. R. China
| | - Aaron Benham
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and
| | - Sreemathi Logan
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Departments of Ophthalmology and Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and
| | - R Steven Brush
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and
| | - Md Nawajes A Mandal
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and
| | - Robert E Anderson
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Departments of Ophthalmology and Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and
| | - Martin-Paul Agbaga
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK; Dean McGee Eye Institute, Oklahoma City, OK; and.
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Ceramide signaling in retinal degeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:553-8. [PMID: 22183377 DOI: 10.1007/978-1-4614-0631-0_70] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Retinal degenerations (RD) are a complex heterogeneous group of diseases in which retinal photoreceptors and the supporting retinal pigment epithelial cells die irreversibly, causing visual loss for millions of people. Mutations on more than 150 genes have been discovered for RD and there are many forms that possess complex etiology involving more than one gene and environmental effect. For years many have searched for some common intracellular second messenger for these many forms of cell death which could be targeted for therapy. Ceramide is a novel cellular second messenger which signals for apoptosis. Several lines of evidence suggest an integral role of ceramide in photoreceptor apoptosis and cell death. Understanding their role in the pathogenic pathways of retinal degenerative diseases is important for development of targeted therapeutics.
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Berta AI, Boesze-Battaglia K, Magyar A, Szél A, Kiss AL. Localization of caveolin-1 and c-src in mature and differentiating photoreceptors: raft proteins co-distribute with rhodopsin during development. J Mol Histol 2011; 42:523-33. [PMID: 21938483 DOI: 10.1007/s10735-011-9360-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 09/10/2011] [Indexed: 11/29/2022]
Abstract
Numerous biochemical and morphological studies have provided insight into the distribution pattern of caveolin-1 and the presence of membrane rafts in the vertebrate retina. To date however, studies have not addressed the localization profile of raft specific proteins during development. Therefore the purpose of our studies was to follow the localization pattern of caveolin-1, phospho-caveolin-1 and c-src in the developing retina and compare it to that observed in adults. Specific antibodies were used to visualize the distribution of caveolin-1, c-src, a kinase phosphorylating caveolin-1, and phospho-caveolin-1. The labeling pattern of this scaffolded complex was compared to those of rhodopsin and rhodopsin kinase. Samples were analyzed at various time points during postnatal development and compared to adult retinas. The immunocytochemical studies were complemented with immunoblots and immunoprecipitation studies. In the mature retina caveolin-1 and c-src localized mainly to the cell body and IS of photoreceptors, with only very weakly labeled OS. In contrast, phospho-caveolin-1 was only detectable in the OS of photoreceptors. During development we followed the expression and distribution profile of these proteins in a temporal sequence with special attention to the period when OS formation is most robust. Double labeling immunocytochemistry and immunoprecipitation showed rhodopsin to colocalize and co-immunoprecipitate with caveolin-1 and c-src. Individual punctate structures between the outer limiting membrane and the outer plexiform layer were seen at P10 to be labeled by both rhodopsin and caveolin-1 as well as by rhodopsin and c-src, respectively. These studies suggest that membrane raft specific proteins are co-distributed during development, thereby pointing to a role for such complexes in OS formation. In addition, the presence of small punctate structures containing caveolin-1, c-src and rhodopsin raise the possibility that these proteins may transport together to OS during development and that caveolin-1 exists predominantly in a phosphorylated form in the OS.
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Affiliation(s)
- Agnes I Berta
- Department of Human Morphology and Developmental Biology, Semmelweis University Budapest, Tűzoltó u. 58, Budapest, Hungary
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