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Simon MV, Basu SK, Qaladize B, Grambergs R, Rotstein NP, Mandal N. Sphingolipids as critical players in retinal physiology and pathology. J Lipid Res 2021; 62:100037. [PMID: 32948663 PMCID: PMC7933806 DOI: 10.1194/jlr.tr120000972] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/04/2020] [Indexed: 12/24/2022] Open
Abstract
Sphingolipids have emerged as bioactive lipids involved in the regulation of many physiological and pathological processes. In the retina, they have been established to participate in numerous processes, such as neuronal survival and death, proliferation and migration of neuronal and vascular cells, inflammation, and neovascularization. Dysregulation of sphingolipids is therefore crucial in the onset and progression of retinal diseases. This review examines the involvement of sphingolipids in retinal physiology and diseases. Ceramide (Cer) has emerged as a common mediator of inflammation and death of neuronal and retinal pigment epithelium cells in animal models of retinopathies such as glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa. Sphingosine-1-phosphate (S1P) has opposite roles, preventing photoreceptor and ganglion cell degeneration but also promoting inflammation, fibrosis, and neovascularization in AMD, glaucoma, and pro-fibrotic disorders. Alterations in Cer, S1P, and ceramide 1-phosphate may also contribute to uveitis. Notably, use of inhibitors that either prevent Cer increase or modulate S1P signaling, such as Myriocin, desipramine, and Fingolimod (FTY720), preserves neuronal viability and retinal function. These findings underscore the relevance of alterations in the sphingolipid metabolic network in the etiology of multiple retinopathies and highlight the potential of modulating their metabolism for the design of novel therapeutic approaches.
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Affiliation(s)
- M Victoria Simon
- 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
| | - Sandip K Basu
- Departments of Ophthalmology and Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Bano Qaladize
- Departments of Ophthalmology and Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Richard Grambergs
- Departments of Ophthalmology and Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - 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.
| | - Nawajes Mandal
- Departments of Ophthalmology and Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA.
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Wu L, Sun Y, Ma L, Zhu J, Zhang B, Pan Q, Li Y, Liu H, Diao A, Li Y. A C-terminally truncated mouse Best3 splice variant targets and alters the ion balance in lysosome-endosome hybrids and the endoplasmic reticulum. Sci Rep 2016; 6:27332. [PMID: 27265833 PMCID: PMC4893618 DOI: 10.1038/srep27332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 05/16/2016] [Indexed: 02/07/2023] Open
Abstract
The Bestrophin family has been characterized as Cl(-) channels in mammals and Na(+) channels in bacteria, but their exact physiological roles remian unknown. In this study, a natural C-terminally truncated variant of mouse Bestrophin 3 (Best3V2) expression in myoblasts and muscles is demonstrated. Unlike full-length Best3, Best3V2 targets the two important intracellular Ca stores: the lysosome and the ER. Heterologous overexpression leads to lysosome swelling and renders it less acidic. Best3V2 overexpression also results in compromised Ca(2+) release from the ER. Knocking down endogenous Best3 expression in myoblasts makes these cells more excitable in response to Ca(2+) mobilizing reagents, such as caffeine. We propose that Best3V2 in myoblasts may work as a tuner to control Ca(2+) release from intracellular Ca(2+) stores.
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Affiliation(s)
- Lichang Wu
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China.,College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yu Sun
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Liqiao Ma
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Jun Zhu
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Baoxia Zhang
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Qingjie Pan
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
| | - Yuyin Li
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Huanqi Liu
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
| | - Aipo Diao
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yinchuan Li
- Department of Animal Sciences and Technology, Qingdao Agricultural University, Qingdao, China
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Strauß O, Reichhart N, Gomez NM, Müller C. Contribution of Ion Channels in Calcium Signaling Regulating Phagocytosis: MaxiK, Cav1.3 and Bestrophin-1. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:739-44. [PMID: 26427483 DOI: 10.1007/978-3-319-17121-0_98] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mutations in the BEST1 gene lead to a variety of retinal degenerations including Best's vitelliforme macular degeneration. The BEST1 gene product, bestrophin-1, is expressed in the retinal pigment epithelium (RPE). It is likely that mutant bestrophin-1 impairs functions of the RPE which support photoreceptor function and will thus lead to retinal degeneration. However, the RPE function which is influenced by bestrophin-1 is so far not identified. Previously we showed that bestrophin-1 interacts with L-type Ca²⁺ channels of the CaV1.3 subtype and that the endogenously expressed bestrophin-1 is required for intracellular Ca²⁺ regulation. A hallmark of Best's disease is the fast lipofuscin accumulation occurring already at young ages. Therefore, we addressed the hypothesis that bestrophin-1 might influence phagocytosis of photoreceptor outer segments (POS) by the RPE. Here, siRNA knock-down of bestrophin-1 expression as well as inhibition of L-type Ca²⁺ channel activity modulated the POS phagocytosis in vitro. In vivo CaV1.3 expression appeared to be diurnal regulated with a higher expression rate in the afternoon. Compared to wild-type littermates, Ca V 1.3 (-/-) mice showed a shift in the circadian POS phagocytosis with an increased activity in the afternoon. Thus we suggest that mutant bestrophin-1 leads to an impaired regulation of the POS phagocytosis by the RPE which would explain the fast lipofuscin accumulation in Best patients.
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Affiliation(s)
- Olaf Strauß
- Experimental Ophthalmology, Department of Ophthalmology, Charite University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Nadine Reichhart
- Experimental Ophthalmology, Department of Ophthalmology, Charite University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Nestor Mas Gomez
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Augustenburger Platz 1, 240 South 40th Street, 19104-6030, Philadelphia, PA, USA.
| | - Claudia Müller
- Department of Biological Sciences, Center for Cancer, Genetic Diseases and Gene Regulation, Fordham University Bronx, 10458, Bronx, NY, USA.
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Giblin JP, Comes N, Strauss O, Gasull X. Ion Channels in the Eye: Involvement in Ocular Pathologies. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2015; 104:157-231. [PMID: 27038375 DOI: 10.1016/bs.apcsb.2015.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The eye is the sensory organ of vision. There, the retina transforms photons into electrical signals that are sent to higher brain areas to produce visual sensations. In the light path to the retina, different types of cells and tissues are involved in maintaining the transparency of avascular structures like the cornea or lens, while others, like the retinal pigment epithelium, have a critical role in the maintenance of photoreceptor function by regenerating the visual pigment. Here, we have reviewed the roles of different ion channels expressed in ocular tissues (cornea, conjunctiva and neurons innervating the ocular surface, lens, retina, retinal pigment epithelium, and the inflow and outflow systems of the aqueous humor) that are involved in ocular disease pathophysiologies and those whose deletion or pharmacological modulation leads to specific diseases of the eye. These include pathologies such as retinitis pigmentosa, macular degeneration, achromatopsia, glaucoma, cataracts, dry eye, or keratoconjunctivitis among others. Several disease-associated ion channels are potential targets for pharmacological intervention or other therapeutic approaches, thus highlighting the importance of these channels in ocular physiology and pathophysiology.
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Affiliation(s)
- Jonathan P Giblin
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Nuria Comes
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | | | - Xavier Gasull
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
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Singh R, Kuai D, Guziewicz KE, Meyer J, Wilson M, Lu J, Smith M, Clark E, Verhoeven A, Aguirre GD, Gamm DM. Pharmacological Modulation of Photoreceptor Outer Segment Degradation in a Human iPS Cell Model of Inherited Macular Degeneration. Mol Ther 2015; 23:1700-1711. [PMID: 26300224 DOI: 10.1038/mt.2015.141] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/23/2015] [Indexed: 12/16/2022] Open
Abstract
Degradation of photoreceptor outer segments (POS) by retinal pigment epithelium (RPE) is essential for vision, and studies have implicated altered POS processing in the pathogenesis of some retinal degenerative diseases. Consistent with this concept, a recently established hiPSC-RPE model of inherited macular degeneration, Best disease (BD), displayed reduced rates of POS breakdown. Herein we utilized this model to determine (i) if disturbances in protein degradation pathways are associated with delayed POS digestion and (ii) whether such defect(s) can be pharmacologically targeted. We found that BD hiPSC-RPE cultures possessed increased protein oxidation, decreased free-ubiquitin levels, and altered rates of exosome secretion, consistent with altered POS processing. Application of valproic acid (VPA) with or without rapamycin increased rates of POS degradation in our model, whereas application of bafilomycin-A1 decreased such rates. Importantly, the negative effect of bafilomycin-A1 could be fully reversed by VPA. The utility of hiPSC-RPE for VPA testing was further evident following examination of its efficacy and metabolism in a complementary canine disease model. Our findings suggest that disturbances in protein degradation pathways contribute to the POS processing defect observed in BD hiPSC-RPE, which can be manipulated pharmacologically. These results have therapeutic implications for BD and perhaps other maculopathies.
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Affiliation(s)
- Ruchira Singh
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA; McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, USA
| | - David Kuai
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Karina E Guziewicz
- Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jackelyn Meyer
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Molly Wilson
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jianfeng Lu
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Molly Smith
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Eric Clark
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Amelia Verhoeven
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Gustavo D Aguirre
- Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - David M Gamm
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA; McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, USA.
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Pasquay C, Wang LF, Lorenz B, Preising MN. Bestrophin 1 – Phenotypes and Functional Aspects in Bestrophinopathies. Ophthalmic Genet 2013; 36:193-212. [DOI: 10.3109/13816810.2013.863945] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Slc26a11 is prominently expressed in the brain and functions as a chloride channel: expression in Purkinje cells and stimulation of V H⁺-ATPase. Pflugers Arch 2013; 465:1583-97. [PMID: 23733100 DOI: 10.1007/s00424-013-1300-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/13/2013] [Accepted: 05/14/2013] [Indexed: 02/07/2023]
Abstract
SLC26A11 (human)/Slc26a11 (mouse), also known as kidney brain anion transporter (KBAT), is a member of the SLC26 anion transporter family and shows abundant mRNA expression in the brain. However, its exact cellular distribution and subcellular localization in the brain and its functional identity and possible physiological roles remain unknown. Expression and immunostaining studies demonstrated that Slc26a11 is abundantly expressed in the cerebellum, with a predominant expression in Purkinje cells. Lower expression levels were detected in hippocampus, olfactory bulb, cerebral cortex, and subcortical structures. Patch clamp studies in HEK293 cells transfected with mouse cDNA demonstrated that Slc26a11 can function as a chloride channel that is active under basal conditions and is not regulated by calcium, forskolin, or co-expression with cystic fibrosis transmembrane regulator. Single and double immunofluorescent labeling studies demonstrated the localization of vacuolar (V) H⁺-ATPase and Slc26a11 (KBAT) in the plasma membrane in Purkinje cells. Functional studies in HEK293 cells indicated that transfection with Slc26a11 stimulated acid transport via endogenous V H⁺-ATPase. We conclude that Slc26a11 (KBAT) is prominently distributed in output neurons of various subcortical and cortical structures in the central nervous system, with specific expression in Purkinje cells and that it may operate as a chloride channel regulating acid translocation by H⁺-ATPase across the plasma membrane and in intracellular compartments.
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