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Smith SB, Wang J, Cui X, Mysona BA, Zhao J, Bollinger KE. Sigma 1 receptor: A novel therapeutic target in retinal disease. Prog Retin Eye Res 2018; 67:130-149. [PMID: 30075336 PMCID: PMC6557374 DOI: 10.1016/j.preteyeres.2018.07.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 07/27/2018] [Accepted: 07/30/2018] [Indexed: 02/08/2023]
Abstract
Retinal degenerative diseases are major causes of untreatable blindness worldwide and efficacious treatments for these diseases are sorely needed. A novel target for treatment of retinal disease is the transmembrane protein Sigma 1 Receptor (Sig1R). This enigmatic protein is an evolutionary isolate with no known homology to any other protein. Sig1R was originally thought to be an opioid receptor. That notion has been dispelled and more recent pharmacological and molecular studies suggest that it is a pluripotent modulator with a number of biological functions, many of which are relevant to retinal disease. This review provides an overview of the discovery of Sig1R and early pharmacologic studies that led to the cloning of the Sig1R gene and eventual elucidation of its crystal structure. Studies of Sig1R in the eye were not reported until the late 1990s, but since that time there has been increasing interest in the potential role of Sig1R as a target for retinal disease. Studies have focused on elucidating the mechanism(s) of Sig1R function in retina including calcium regulation, modulation of oxidative stress, ion channel regulation and molecular chaperone activity. Mechanistic studies have been performed in isolated retinal cells, such as Müller glial cells, microglial cells, optic nerve head astrocytes and retinal ganglion cells as well as in the intact retina. Several compelling studies have provided evidence of powerful in vivo neuroprotective effects against ganglion cell loss as well as photoreceptor cell loss. Also described are studies that have examined retinal structure/function in various models of retinal disease in which Sig1R is absent and reveal that these phenotypes are accelerated compared to retinas of animals that express Sig1R. The collective evidence from analysis of studies over the past 20 years is that Sig1R plays a key role in modulating retinal cellular stress and that it holds great promise as a target in retinal neurodegenerative disease.
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Affiliation(s)
- Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA; The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University 30912, Augusta, GA, USA.
| | - Jing Wang
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA; The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Xuezhi Cui
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA; The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Barbara A Mysona
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA; The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Jing Zhao
- The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University 30912, Augusta, GA, USA
| | - Kathryn E Bollinger
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA; The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA; Department of Ophthalmology, Medical College of Georgia at Augusta University 30912, Augusta, GA, USA
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Shanmugam AK, Mysona BA, Wang J, Zhao J, Tawfik A, Sanders A, Markand S, Zorrilla E, Ganapathy V, Bollinger KE, Smith SB. Progesterone Receptor Membrane Component 1 (PGRMC1) Expression in Murine Retina. Curr Eye Res 2015; 41:1105-1112. [PMID: 26642738 DOI: 10.3109/02713683.2015.1085579] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Sigma receptors 1 (σR1) and 2 (σR2) are thought to be two distinct proteins which share the ability to bind multiple ligands, several of which are common to both receptors. Whether σR1 and σR2 share overlapping biological functions is unknown. Recently, progesterone receptor membrane component 1 (PGRMC1) was shown to contain the putative σR2 binding site. PGRMC1 has not been studied in retina. We hypothesize that biological interactions between σR1 and PGRMC1 will be evidenced by compensatory upregulation of PGRMC1 in σR1-/- mice. METHODS Immunofluorescence, RT-PCR, and immunoblotting methods were used to analyze expression of PGRMC1 in wild-type mouse retina. Tissues from σR1-/- mice were used to investigate whether a biological interaction exists between σR1 and PGRMC1. RESULTS In the eye, PGRMC1 is expressed in corneal epithelium, lens, ciliary body epithelium, and retina. In retina, PGRMC1 is present in Müller cells and retinal pigment epithelium. This expression pattern is similar, but not identical to σR1. PGRMC1 protein levels in neural retina and eye cup from σR1-/- mice did not differ from wild-type mice. Nonocular tissues, lung, heart, and kidney showed similar Pgrmc1 gene expression in wild-type and σR1-/- mice. In contrast, liver, brain, and intestine showed increased Pgrmc1 gene expression in σR1-/- mice. CONCLUSION Despite potential biological overlap, deletion of σR1 did not result in a compensatory change in PGRMC1 protein levels in σR1-/- mouse retina. Increased Pgrmc1 gene expression in organs with high lipid content such as liver, brain, and intestine indicates a possible tissue-specific interaction between σR1 and PGRMC1. The current studies establish the presence of PGRMC1 in retina and lay the foundation for analysis of its biological function.
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Affiliation(s)
- Arul K Shanmugam
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Barbara A Mysona
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Jing Wang
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Jing Zhao
- b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Amany Tawfik
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - A Sanders
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Shanu Markand
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Eric Zorrilla
- d Harold L. Dorris Neurological Research Institute , The Scripps Research Institute , La Jolla , CA , USA
| | - Vadivel Ganapathy
- b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,e Department of Cell Biology and Biochemistry , Texas Tech University Health Sciences Center , Lubbock , TX , USA
| | - Kathryn E Bollinger
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Sylvia B Smith
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
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Ola MS, Moore P, El-Sherbeny A, Roon P, Agarwal N, Sarthy VP, Casellas P, Ganapathy V, Smith SB. Expression pattern of sigma receptor 1 mRNA and protein in mammalian retina. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 95:86-95. [PMID: 11687279 PMCID: PMC3742362 DOI: 10.1016/s0169-328x(01)00249-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sigma receptors are nonopiate and nonphencyclidine binding sites that are thought to be neuroprotective due to modulation of N-methyl-D-aspartate (NMDA) receptors. Sigma receptor 1 expression has been demonstrated in numerous tissues including brain. Recently, studies using binding assays have demonstrated sigma receptor 1 in neural retina, however these studies did not demonstrate in which retinal cell type(s) sigma receptor 1 was present nor did they establish unequivocally the molecular identity of the receptor. The present study was designed to address these issues. Reverse transcription-polymerase chain reaction (RT-PCR) analysis amplified sigma receptor 1 in neural retina, RPE-choroid complex, and lens isolated from mice. A similar RT-PCR product was amplified also in three cultured cell lines, rat Müller cells, rat ganglion cells and human ARPE-19 cells. In situ hybridization analysis revealed abundant sigma receptor 1 expression in ganglion cells, cells of the inner nuclear layer, inner segments of photoreceptor cells and retinal pigment epithelial (RPE) cells. Immunohistochemical studies detected the sigma receptor 1 protein in retinal ganglion, photoreceptor, RPE cells and surrounding the soma of cells in the inner nuclear layer. These data provide the first cellular localization of sigma receptor 1 in neural retina and establish the molecular identity of sigma receptor 1 in retinal cells. The demonstration that sigma receptor 1 is present in ganglion cells is particularly noteworthy given the well-documented susceptibility of these cells to glutamate toxicity. Our findings suggest that retinal ganglion cells may be amenable to the neuroprotective effects of sigma ligands under conditions of neurotoxicity such as occurs in diabetes.
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Affiliation(s)
- M. Shamsul Ola
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta, GA 30912
| | - Pamela Moore
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta, GA 30912
| | - Amira El-Sherbeny
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta, GA 30912
| | - Penny Roon
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta, GA 30912
| | - Neeraj Agarwal
- Department of Anatomy and Cell Biology University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Vijay P. Sarthy
- Dept of Ophthalmology Northwestern University Medical School, Chicago, IL 60611
| | | | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology Medical College of Georgia, Augusta, GA 30912
| | - Sylvia B. Smith
- Department of Cellular Biology and Anatomy Medical College of Georgia, Augusta, GA 30912
- Department of Ophthalmology Medical College of Georgia, Augusta, GA 30912
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Schoenwald RD, Vidvauns S, Wurster DE, Barfknecht CF. The role of tear proteins in tear film stability in the dry eye patient and in the rabbit. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 438:391-400. [PMID: 9634912 DOI: 10.1007/978-1-4615-5359-5_54] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- R D Schoenwald
- Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City, USA
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Schoenwald RD, Yang YS, Xia E, Barfknecht CF. Uptake of N,N-dimethyl-2-phenylethylene HCl into acini cells removed from rabbit lacrimal glands. J Ocul Pharmacol Ther 1998; 14:253-62. [PMID: 9671433 DOI: 10.1089/jop.1998.14.253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Acini cells were obtained from the lacrimal gland of the white New Zealand rabbit. Following isolation and purification, the cells were used to study the uptake of N,N'-dimethyl-2-phenylethylamine HCl (AF2975), which was found to be sodium- and proton-independent, but energy-dependent. Uptake was mainly accomplished via a carrier-mediated transport system for which a Km of 8.72+/-0.96 mM, a Vmax of 602.6+/-41.3 nmol/mg of protein/min, and an exponential coefficient of 2.55+/-0.46 were obtained following a least squares nonlinear fit to the Hill equation. With the addition of the metabolic inhibitors, sodium azide or 2,4-dinitrophenol, the initial uptake rates were reduced from the control experiments by 35.7% and 26.2%, respectively.
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Affiliation(s)
- R D Schoenwald
- Division of Pharmaceutics, College of Pharmacy, The University of Iowa, Iowa City 52242-1112, USA
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Schoenwald RD, Vidvauns S, Wurster DE, Barfknecht CF. The influence of tear proteins on the film stability of rabbit tear extracts. J Ocul Pharmacol Ther 1998; 14:15-29. [PMID: 9493780 DOI: 10.1089/jop.1998.14.15] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This study was undertaken to gain an understanding of the significance of tear proteins in stabilizing the tear film. Either a sigma agonist, N,N-dimethyl-2-phenylethylamine HCl (AF2975), or a sigma antagonist, haloperidol, was administered to rabbit eyes in order to increase or decrease protein secretion, respectively. At 0, 10 and 60 minutes after instillation, tear proteins were extracted from Schirmer strips and measured for total protein. A portion of the extract was used for separating five major protein fractions using size-exclusion HPLC. Total protein extract or individual protein fractions were measured for surface tension by the horizontal capillary method and for in vitro break up time (in vitro BUT), a newly designed procedure. A statistically significant decrease was measured for surface tension and a concomitant increase was measured for in vitro BUT for the total protein samples at 10 and 60 minutes after instillation of AF2975 compared to the vehicle treated eye. The results for haloperidol yielded an increase in surface tension and an decrease in in vitro BUT. When the tear proteins were separated into five major fractions, only the 23 minute protein fraction was found to decrease surface tension and increase in vitro BUT following AF2975 administration. Haloperidol, a sigma antagonist, showed an exact opposite effect for the total protein and the 23 minute protein fraction.
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Affiliation(s)
- R D Schoenwald
- Division of Pharmaceutics, College of Pharmacy, The University of Iowa, Iowa City 52242, USA
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Schoenwald RD, Vidvauns S, Wurster DE, Barfknecht CF. Tear film stability of protein extracts from dry eye patients administered a sigma agonist. J Ocul Pharmacol Ther 1997; 13:151-61. [PMID: 9090615 DOI: 10.1089/jop.1997.13.151] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Fourteen dry eye volunteers placed one to two drops of 0.15% AF2975 (N,N-dimethyl-2-phenylethylamine HCl) in one eye and the vehicle in their other eye four times a day for 21 days. AF2975 is a sigma agonist known to stimulate the release of tear proteins after instillation in rabbit eyes and was tested for its ability to stabilize protein film extracted from dry eye volunteers. After day 7 and again after day 21, Schirmer test strips were inserted in each eye for 5 minutes, measured for wetting, and stored at -20 degrees C for protein analysis. A volume of 600 microliters was used to extract total protein. A portion of the extract was analyzed for total protein. The remainder was used to measure surface tension, to determine in vitro break up time (in vitro BUT) in a newly designed apparatus, and to further analyze for tear lipocalin, formerly known as presystemic tear albumin. Statistically significant differences were obtained between the drug treated eye and the vehicle treated eye for measurements determined for days 7 and 21. Tear extracts from the drug treated eye showed statistically significant decreases in surface tension and increases in in vitro BUT. Extracts from the drug treated eye also showed statistically significant increases in protein content and tear lipocalin. The results suggest that AF2975 may be able to stabilize the tear film by increasing the concentration of proteins in human tears.
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Affiliation(s)
- R D Schoenwald
- Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City, USA
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Schoenwald RD, Barfknecht CF, Shirolkar S, Xia E. The effects of sigma ligands on protein release from lacrimal acinar cells: a potential agonist/antagonist assay. Life Sci 1995; 56:1275-85. [PMID: 8614245 DOI: 10.1016/0024-3205(95)00073-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sigma receptor antagonists have been proposed as leading clinical candidates for use in various psychotic disorders. Prior to clinical testing, it is imperative that a new agent be correctly identified as an antagonist and not an agonist since the latter may worsen the psychosis. For sigma-ligands many behavioral and pharmacological assays have been developed in an attempt to classify agonist/antagonist activity. These assays evaluate a response or a behavior in an animal model that can be related to clinical efficacy. However, is the action by the presumed antagonist a consequence of sigma-receptor activity? Previously we have identified sigma-receptors in acinar cells of the main lacrimal gland of the New Zealand white rabbit and have measured protein release after the addition of various N,N-disubstituted phenylalkylamine derivatives known to be sigma-ligands by receptor binding studies. Although protein release from acinar cells has been attributed to either muscarinic or alpha-adrenergic stimulation, protein release from sigma-receptor stimulation was also confirmed. In the reported studies here, we isolated and incubated acinar cells with varying concentrations of known sigma-ligands and measured protein concentration. A knowledge of the receptor profile for the disubstituted phenylalkylamines permitted experiments to be designed in which various alpha, muscarinic, serotonergic, and dopaminergic antagonists could be added in equimolar concentrations. Under the conditions of these experiments, statistically significant increases in protein release for sigma-ligands could be attributed to stimulation of sigma-receptors. Haloperidol, an apparent sigma-antagonist, caused a statistically significant decrease in protein release and also inhibited protein release when tested with a known sigma-ligand, AF2975 [N,N-dimethyl-2-phenylethylamine]. In this system, stimulation and inhibition of protein release were defined as agonist and antagonist behavior, respectively. Of particular interest were the results for BMY14802 and +/- pentazocine, both of which were found to be agonists. Various antipsychotic and antidepressant drugs were measured for their agonist/antagonist behavior. Because of multireceptors present in acini, their agonist or antagonist behaviour could not be attributed solely to interaction with the sigma-receptor unless specific antagonists were added.
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Affiliation(s)
- R D Schoenwald
- Division of Pharmaceutics, University of Iowa, College of Pharmacy, Iowa City 52242, USA
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